SUSE Linux Enterprise Server 12 SP4 64-bit

File Saves the output of the command into a le, an existing le will be deleted. For example, the ls command writes its output into the le listing.txt : ls > listing.txt Command >> File Appends the output of the command to a le. For example, the ls command appends its output to the le listing.txt : ls >> listing.txt Command < File Reads the le as input for the given command. For example, the read command reads in the content of the le into the variable: read a < foo Command1 | Command2 Redirects the output of the left command as input for the right command. For example, the cat command outputs the content of the /proc/cpuinfo le. This output is used by grep to lter only those lines which contain cpu : cat /proc/cpuinfo | grep cpu 9 Redirecting Command Events SLES 12 SP4Every channel has a le descriptor: 0 (zero) for standard input, 1 for standard output and 2 for standard error. It is allowed to insert this le descriptor before a < or > character. For example, the following line searches for a le starting with foo , but suppresses its errors by redirecting it to /dev/null : find / -name "foo*" 2>/dev/null 1.4 Using Aliases An alias is a shortcut denition of one or more commands. The syntax for an alias is: alias NAME=DEFINITION For example, the following line denes an alias lt that outputs a long listing (option -l ), sorts it by modication time ( -t ), and prints it in reverse sorted order ( -r ): alias lt=''ls -ltr'' To view all alias denitions, use alias . Remove your alias with unalias and the corresponding alias name. 1.5 Using Variables in Bash A shell variable can be global or local. Global variables, or environment variables, can be accessed in all shells. In contrast, local variables are visible in the current shell only. To view all environment variables, use the printenv command. If you need to know the value of a variable, insert the name of your variable as an argument: printenv PATH A variable, be it global or local, can also be viewed with echo : echo $PATH To set a local variable, use a variable name followed by the equal sign, followed by the value: PROJECT="SLED" 10 Using Aliases SLES 12 SP4Do not insert spaces around the equal sign, otherwise you get an error. To set an environment variable, use export : export NAME="tux" To remove a variable, use unset : unset NAME The following table contains some common environment variables which can be used in you shell scripts: TABLE 1.5: USEFUL ENVIRONMENT VARIABLES HOME the home directory of the current user HOST the current host name LANG when a tool is localized, it uses the language from this environment variable. English can also be set to C PATH the search path of the shell, a list of directories separated by colon PS1 species the normal prompt printed before each command PS2 species the secondary prompt printed when you execute a multi-line command PWD current working directory USER the current user 1.5.1 Using Argument Variables For example, if you have the script foo.sh you can execute it like this: foo.sh "Tux Penguin" 2000 11 Using Argument Variables SLES 12 SP4To access all the arguments which are passed to your script, you need positional parameters. These are $1 for the rst argument, $2 for the second, and so on. You can have up to nine parameters. To get the script name, use $0 . The following script foo.sh prints all arguments from 1 to 4: #!/bin/sh echo \"$1\" \"$2\" \"$3\" \"$4\" If you execute this script with the above arguments, you get: "Tux Penguin" "2000" "" "" 1.5.2 Using Variable Substitution Variable substitutions apply a pattern to the content of a variable either from the left or right side. The following list contains the possible syntax forms: ${VAR#pattern} removes the shortest possible match from the left: file=/home/tux/book/book.tar.bz2 echo ${file#*/} home/tux/book/book.tar.bz2 ${VAR##pattern} removes the longest possible match from the left: file=/home/tux/book/book.tar.bz2 echo ${file##*/} book.tar.bz2 ${VAR%pattern} removes the shortest possible match from the right: file=/home/tux/book/book.tar.bz2 echo ${file%.*} /home/tux/book/book.tar ${VAR%%pattern} removes the longest possible match from the right: file=/home/tux/book/book.tar.bz2 12 Using Variable Substitution SLES 12 SP4echo ${file%%.*} /home/tux/book/book ${VAR/pattern_1/pattern_2} substitutes the content of VAR from the PATTERN_1 with PATTERN_2 : file=/home/tux/book/book.tar.bz2 echo ${file/tux/wilber} /home/wilber/book/book.tar.bz2 1.6 Grouping and Combining Commands Shells allow you to concatenate and group commands for conditional execution. Each command returns an exit code which determines the success or failure of its operation. If it is 0 (zero) the command was successful, everything else marks an error which is specic to the command. The following list shows, how commands can be grouped: Command1 ; Command2 executes the commands in sequential order. The exit code is not checked. The following line displays the content of the le with cat and then prints its le properties with ls regardless of their exit codes: cat filelist.txt ; ls -l filelist.txt Command1 && Command2 runs the right command, if the left command was successful (logical AND). The following line displays the content of the le and prints its le properties only, when the previous command was successful (compare it with the previous entry in this list): cat filelist.txt && ls -l filelist.txt Command1 || Command2 runs the right command, when the left command has failed (logical OR). The following line creates only a directory in /home/wilber/bar when the creation of the directory in /home/tux/foo has failed: mkdir /home/tux/foo || mkdir /home/wilber/bar funcname(){ ... } 13 Grouping and Combining Commands SLES 12 SP4creates a shell function. You can use the positional parameters to access its arguments. The following line denes the function hello to print a short message: hello() { echo "Hello $1"; } You can call this function like this: hello Tux which prints: Hello Tux 1.7 Working with Common Flow Constructs To control the ow of your script, a shell has while , if , for and case constructs. 1.7.1 The if Control Command The if command is used to check expressions. For example, the following code tests whether the current user is Tux: if test $USER = "tux"; then echo "Hello Tux." else echo "You are not Tux." fi The test expression can be as complex or simple as possible. The following expression checks if the le foo.txt exists: if test -e /tmp/foo.txt ; then echo "Found foo.txt" fi The test expression can also be abbreviated in angled brackets: if [ -e /tmp/foo.txt ] ; then echo "Found foo.txt" fi Find more useful expressions at http://www.cyberciti.biz/nixcraft/linux/docs/uniqlinuxfeatures/ lsst/ch03sec02.html . 14 Working with Common Flow Constructs SLES 12 SP41.7.2 Creating Loops with the for Command The for loop allows you to execute commands to a list of entries. For example, the following code prints some information about PNG les in the current directory: for i in *.png; do ls -l $i done 1.8 For More Information Important information about Bash is provided in the man pages man bash . More about this topic can be found in the following list: http://tldp.org/LDP/Bash-Beginners-Guide/html/index.html —Bash Guide for Beginners http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html —BASH Programming - Introduction HOW-TO http://tldp.org/LDP/abs/html/index.html —Advanced Bash-Scripting Guide http://www.grymoire.com/Unix/Sh.html —Sh - the Bourne Shell 15 Creating Loops with the for Command SLES 12 SP42 sudo Many commands and system utilities need to be run as root to modify les and/or perform tasks that only the super user is allowed to. For security reasons and to avoid accidentally running dangerous commands, it is generally advisable not to log in directly as root . Instead, it is recommended to work as a normal, unprivileged user and use the sudo command to run commands with elevated privileges. On SUSE Linux Enterprise Server, sudo is congured by default to work similarly to su. However, sudo oers the possibility to allow users to run commands with privileges of any other user in a highly congurable manner. This can be used to assign roles with specic privileges to certain users and groups. It is for example possible to allow members of the group users to run a command with the privileges of wilber . Access to the command can be further restricted by, for example, forbidding to specify any command options. While su always requires the root password for authentication with PAM, sudo can be congured to authenticate with your own credentials. This increases security by not having to share the root password. For example, you can allow members of the group users to run a command frobnicate as wilber , with the restriction that no arguments are specied. This can be used to assign roles with specic abilities to certain users and groups. 2.1 Basic sudo Usage sudo is simple to use, yet very powerful. 2.1.1 Running a Single Command Logged in as normal user, you can run any command as root by adding sudo before it. It will prompt for the root password and, if authenticated successfully, run the command as root : tux > id -un 1 tux tux > sudo id -un root''s password: 2 root tux > id -un tux 3 tux > sudo id -un 16 Basic sudo Usage SLES 12 SP44 root 1 The id -un command prints the login name of the current user. 2 The password is not shown during input, neither as clear text nor as bullets. 3 Only commands started with sudo are run with elevated privileges. If you run the same command without the sudo prex, it is run with the privileges of the current user again. 4 For a limited amount of time, you do not need to enter the root password again. Tip: I/O Redirection I/O redirection does not work as you would probably expect: tux > sudo echo s > /proc/sysrq-trigger bash: /proc/sysrq-trigger: Permission denied tux > sudo cat < /proc/1/maps bash: /proc/1/maps: Permission denied Only the echo / cat binary is run with elevated privileges, while the redirection is performed by the user''s shell with user privileges. You can either start a shell like in Section 2.1.2, “Starting a Shell” or use the dd utility instead: echo s | sudo dd of=/proc/sysrq-trigger sudo dd if=/proc/1/maps | cat 2.1.2 Starting a Shell Having to add sudo before every command can be cumbersome. While you could specify a shell as a command sudo bash , it is recommended to rather use one of the built-in mechanisms to start a shell: sudo -s () Starts a shell specied by the SHELL environment variable or the target user''s default shell. If a command is given, it is passed to the shell (with the -c option), else the shell is run in interactive mode. tux:~ > sudo -i root''s password: 17 Starting a Shell SLES 12 SP4root:/home/tux # exit tux:~ > sudo -i () Like -s , but starts the shell as login shell. This means that the shell''s start-up les ( .profile etc.) are processed and the current working directory is set to the target user''s home directory. tux:~ > sudo -i root''s password: root:~ # exit tux:~ > 2.1.3 Environment Variables By default, sudo does not propagate environment variables: tux > ENVVAR=test env | grep ENVVAR ENVVAR=test tux > ENVVAR=test sudo env | grep ENVVAR root''s password: 1 tux > 1 The empty output shows that the environment variable ENVVAR did not exist in the context of the command run with sudo . This behavior can be changed by the env_reset option, see Table 2.1, “Useful Flags and Options”. 2.2 Configuring sudo sudo is a very exible tool with extensive conguration. Note: Locked yourself out of sudo If you accidentally locked yourself out of sudo , use su - and the root password to get a root shell. To x the error, run visudo . 18 Environment Variables SLES 12 SP42.2.1 Editing the Configuration Files The main policy conguration le for sudo is /etc/sudoers . As it is possible to lock yourself out of the system due to errors in this le, it is strongly recommended to use visudo for editing. It will prevent simultaneous changes to the opened le and check for syntax errors before saving the modications. Despite its name, you can also use editors other than vi by setting the EDITOR environment variable, for example: sudo EDITOR=/usr/bin/nano visudo However, the /etc/sudoers le itself is supplied by the system packages and modications may break on updates. Therefore, it is recommended to put custom conguration into les in the /etc/sudoers.d/ directory. Any le in there is automatically included. To create or edit a le in that subdirectory, run: sudo visudo -f /etc/sudoers.d/NAME Alternatively with a dierent editor (for example nano ): sudo EDITOR=/usr/bin/nano visudo -f /etc/sudoers.d/NAME Note: Ignored Files in /etc/sudoers.d The #includedir command in /etc/sudoers , used for /etc/sudoers.d , ignores les that end in ~ (tilde) or contain a . (dot). For more information on the visudo command, run man 8 visudo . 2.2.2 Basic sudoers Configuration Syntax In the sudoers conguration les, there are two types of options: strings and ags. While strings can contain any value, ags can be turned either ON or OFF. The most important syntax constructs for sudoers conguration les are: # Everything on a line after a # gets ignored 1 Defaults !insults # Disable the insults flag 2 Defaults env_keep += "DISPLAY HOME" # Add DISPLAY and HOME to env_keep 19 Editing the Configuration Files SLES 12 SP4tux ALL = NOPASSWD: /usr/bin/frobnicate, PASSWD: /usr/bin/journalctl 3 1 There are two exceptions: #include and #includedir are normal commands. Followed by digits, it species a UID. 2 Remove the ! to set the specied ag to ON. 3 See Section 2.2.3, “Rules in sudoers”. TABLE 2.1: USEFUL FLAGS AND OPTIONS Option name Description Example targetpw This ag controls whether Defaults targetpw # Turn the invoking user is required targetpw flag ON to enter the password of the target user (ON) (for example root ) or the invoking user (OFF). rootpw If set, sudo will prompt for Defaults !rootpw # Turn the root password instead rootpw flag OFF of the target user''s or the password of the user that invoked the command. The default is OFF. env_reset If set, sudo constructs a Defaults env_reset # Turn minimal environment with env_reset flag ON only TERM , PATH , HOME , MAIL , SHELL , LOGNAME , USER , USERNAME , and SUDO_* set. Additionally, variables listed in env_keep get imported from the calling environment. The default is ON. env_keep List of environment variables # Set env_keep to contain to keep when the env_reset EDITOR and PROMPT Defaults env_keep = "EDITOR ag is ON. PROMPT" 20 Basic sudoers Configuration Syntax SLES 12 SP4Option name Description Example Defaults env_keep += "JRE_HOME" # Add JRE_HOME Defaults env_keep -= "JRE_HOME" # Remove JRE_HOME env_delete List of environment variables # Set env_delete to contain to remove when the EDITOR and PROMPT Defaults env_delete = env_reset ag is OFF. "EDITOR PROMPT" Defaults env_delete += "JRE_HOME" # Add JRE_HOME Defaults env_delete - = "JRE_HOME" # Remove JRE_HOME The Defaults token can also be used to create aliases for a collection of users, hosts, and commands. Furthermore, it is possible to apply an option only to a specic set of users. For detailed information about the /etc/sudoers conguration le, consult man 5 sudoers . 2.2.3 Rules in sudoers Rules in the sudoers conguration can be very complex, so this section will only cover the basics. Each rule follows the basic scheme ( [] marks optional parts): #Who Where As whom Tag What User_List Host_List = [(User_List)] [NOPASSWD:|PASSWD:] Cmnd_List SYNTAX FOR SUDOERS RULES User_List One or more (separated by , ) identiers: Either a user name, a group in the format %GROUPNAME or a user ID in the format #UID . Negation can be performed with a ! prex. Host_List One or more (separated by , ) identiers: Either a (fully qualied) host name or an IP address. Negation can be performed with a ! prex. ALL is the usual choice for Host_List . NOPASSWD:|PASSWD: 21 Rules in sudoers SLES 12 SP4The user will not be prompted for a password when running commands matching CMDSPEC after NOPASSWD: . PASSWD is the default, it only needs to be specied when both are on the same line: tux ALL = PASSWD: /usr/bin/foo, NOPASSWD: /usr/bin/bar Cmnd_List One or more (separated by , ) speciers: A path to an executable, followed by allowed arguments or nothing. /usr/bin/foo # Anything allowed /usr/bin/foo bar # Only "/usr/bin/foo bar" allowed /usr/bin/foo "" # No arguments allowed ALL can be used as User_List , Host_List , and Cmnd_List . A rule that allows tux to run all commands as root without entering a password: tux ALL = NOPASSWD: ALL A rule that allows tux to run systemctl restart apache2 : tux ALL = /usr/bin/systemctl restart apache2 A rule that allows tux to run wall as admin with no arguments: tux ALL = (admin) /usr/bin/wall "" Warning: Dangerous constructs Constructs of the kind ALL ALL = ALL must not be used without Defaults targetpw , otherwise anyone can run commands as root . Important: Winbind and sudo When specifying the group name in the sudoers le, make sure that you use the the NetBIOS domain name instead of the realm, for example: %DOMAIN\\GROUP_NAME ALL = (ALL) ALL 22 Rules in sudoers SLES 12 SP4Keep in mind that when using winbindd, the format also depends on the winbind separator option in the smb.conf le. By default, it is \ . If it is changed, for example, to + , then the account format in sudoers le must be DOMAIN+GROUP_NAME . 2.3 Common Use Cases Although the default conguration is often sucient for simple setups and desktop environments, custom congurations can be very useful. 2.3.1 Using sudo without root Password In cases with special restrictions (“user X can only run command Y as root ”) it is not possible. In other cases, it is still favorable to have some kind of separation. By convention, members of the group wheel can run all commands with sudo as root. 1. Add yourself to the wheel group If your user account is not already member of the wheel group, add it by running sudo usermod -a -G wheel USERNAME and logging out and in again. Verify that the change was successful by running groups USERNAME . 2. Make authentication with the invoking user''s password the default. Create the le /etc/sudoers.d/userpw with visudo (see Section  2.2.1, “Editing the Configuration Files”) and add: Defaults !targetpw 3. Select a new default rule. Depending on whether you want users to re-enter their passwords, uncomment the specic line in /etc/sudoers and comment out the default rule. ## Uncomment to allow members of group wheel to execute any command # %wheel ALL=(ALL) ALL ## Same thing without a password # %wheel ALL=(ALL) NOPASSWD: ALL 4. Make the default rule more restrictive 23 Common Use Cases SLES 12 SP4Comment out or remove the allow-everything rule in /etc/sudoers : ALL ALL=(ALL) ALL # WARNING! Only use this together with ''Defaults targetpw''! Warning: Dangerous rule in sudoers Do not forget this step, otherwise any user can execute any command as root ! 5. Test the conguration Try to run sudo as member and non-member of wheel . tux:~ > groups users wheel tux:~ > sudo id -un tux''s password: root wilber:~ > groups users wilber:~ > sudo id -un wilber is not in the sudoers file. This incident will be reported. 2.3.2 Using sudo with X.Org Applications When starting graphical applications with sudo , you will encounter the following error: tux > sudo xterm xterm: Xt error: Can''t open display: %s xterm: DISPLAY is not set YaST will pick the ncurses interface instead of the graphical one. To use X.Org in applications started with sudo , the environment variables DISPLAY and XAUTHORITY need to be propagated. To congure this, create the le /etc/sudoers.d/xorg , (see Section 2.2.1, “Editing the Configuration Files”) and add the following line: Defaults env_keep += "DISPLAY XAUTHORITY" If not set already, set the XAUTHORITY variable as follows: export XAUTHORITY=~/.Xauthority Now X.Org applications can be run as usual: sudo yast2 24 Using sudo with X.Org Applications SLES 12 SP42.4 More Information A quick overview about the available command line switches can be retrieved by sudo --help . An explanation and other important information can be found in the man page: man 8 sudo , while the conguration is documented in man 5 sudoers . 25 More Information SLES 12 SP43 YaST Online Update SUSE oers a continuous stream of software security updates for your product. By default, the update applet is used to keep your system up-to-date. Refer to Book “Deployment Guide”, Chapter 13 “Installing or Removing Software”, Section 13.5 “Keeping the System Up-to-date” for further information on the update applet. This chapter covers the alternative tool for updating software packages: YaST Online Update. The current patches for SUSE® Linux Enterprise Server are available from an update software repository. If you have registered your product during the installation, an update repository is already congured. If you have not registered SUSE Linux Enterprise Server, you can do so by starting the Product Registration in YaST. Alternatively, you can manually add an update repository from a source you trust. To add or remove repositories, start the Repository Manager with Software Software Repositories in YaST. Learn more about the Repository Manager in Book “Deployment Guide”, Chapter 13 “Installing or Removing Software”, Section 13.4 “Managing Software Repositories and Services”. Note: Error on Accessing the Update Catalog If you are not able to access the update catalog, this might be because of an expired subscription. Normally, SUSE Linux Enterprise Server comes with a one-year or three- year subscription, during which you have access to the update catalog. This access will be denied after the subscription ends. If an access to the update catalog is denied, you will see a warning message prompting you to visit the SUSE Customer Center and check your subscription. The SUSE Customer Center is available at https://scc.suse.com// . SUSE provides updates with dierent relevance levels: Security Updates Fix severe security hazards and should always be installed. Recommended Updates Fix issues that could compromise your computer. Optional Updates Fix non-security relevant issues or provide enhancements. 26 SLES 12 SP43.1 The Online Update Dialog To open the YaST Online Update dialog, start YaST and select Software Online Update. Alternatively, start it from the command line with yast2 online_update . The Online Update window consists of four sections. FIGURE 3.1: YAST ONLINE UPDATE The Summary section on the left lists the available patches for SUSE Linux Enterprise Server. The patches are sorted by security relevance: security , recommended , and optional . You can change the view of the Summary section by selecting one of the following options from Show Patch Category: Needed Patches (default view) Non-installed patches that apply to packages installed on your system. Unneeded Patches Patches that either apply to packages not installed on your system, or patches that have requirements which have already have been fullled (because the relevant packages have already been updated from another source). All Patches All patches available for SUSE Linux Enterprise Server. 27 The Online Update Dialog SLES 12 SP4Each list entry in the Summary section consists of a symbol and the patch name. For an overview of the possible symbols and their meaning, press Shift – F1 . Actions required by Security and Recommended patches are automatically preset. These actions are Autoinstall, Autoupdate and Autodelete. If you install an up-to-date package from a repository other than the update repository, the requirements of a patch for this package may be fullled with this installation. In this case a check mark is displayed in front of the patch summary. The patch will be visible in the list until you mark it for installation. This will in fact not install the patch (because the package already is up-to-date), but mark the patch as having been installed. Select an entry in the Summary section to view a short Patch Description at the bottom left corner of the dialog. The upper right section lists the packages included in the selected patch (a patch can consist of several packages). Click an entry in the upper right section to view details about the respective package that is included in the patch. 3.2 Installing Patches The YaST Online Update dialog allows you to either install all available patches at once or manually select the desired patches. You may also revert patches that have been applied to the system. By default, all new patches (except optional ones) that are currently available for your system are already marked for installation. They will be applied automatically once you click Accept or Apply. If one or multiple patches require a system reboot, you will be notied about this before the patch installation starts. You can then either decide to continue with the installation of the selected patches, skip the installation of all patches that need rebooting and install the rest, or go back to the manual patch selection. PROCEDURE 3.1: APPLYING PATCHES WITH YAST ONLINE UPDATE 1. Start YaST and select Software Online Update. 2. To automatically apply all new patches (except optional ones) that are currently available for your system, press Apply or Accept. 3. First modify the selection of patches that you want to apply: a. Use the respective lters and views that the interface provides. For details, refer to Section 3.1, “The Online Update Dialog”. 28 Installing Patches SLES 12 SP4b. Select or deselect patches according to your needs and wishes by right-clicking the patch and choosing the respective action from the context menu. Important: Always Apply Security Updates Do not deselect any security -related patches without a very good reason. These patches x severe security hazards and prevent your system from being exploited. c. Most patches include updates for several packages. If you want to change actions for single packages, right-click a package in the package view and choose an action. d. To conrm your selection and apply the selected patches, proceed with Apply or Accept. 4. After the installation is complete, click Finish to leave the YaST Online Update. Your system is now up-to-date. 3.3 Automatic Online Update YaST also oers the possibility to set up an automatic update with daily, weekly or monthly schedule. To use the respective module, you need to install the yast2-online-update- configuration package rst. By default, updates are downloaded as delta RPMs. Since rebuilding RPM packages from delta RPMs is a memory- and processor-intensive task, certain setups or hardware congurations might require you to disable the use of delta RPMs for the sake of performance. Some patches, such as kernel updates or packages requiring license agreements, require user interaction, which would cause the automatic update procedure to stop. You can congure to skip patches that require user interaction. PROCEDURE 3.2: CONFIGURING THE AUTOMATIC ONLINE UPDATE 1. After installation, start YaST and select Software Online Update Conguration. Alternatively, start the module with yast2  online_update_configuration from the command line. 2. Activate Automatic Online Update. 29 Automatic Online Update SLES 12 SP43. Choose the update interval: Daily, Weekly, or Monthly. 4. To automatically accept any license agreements, activate Agree with Licenses. 5. Select if you want to Skip Interactive Patches in case you want the update procedure to proceed fully automatically. Important: Skipping Patches If you select to skip any packages that require interaction, run a manual Online Update occasionally to install those patches, too. Otherwise you might miss important patches. 6. To automatically install all packages recommended by updated packages, activate Include Recommended Packages. 7. To disable the use of delta RPMs (for performance reasons), deactivate Use Delta RPMs. 8. To lter the patches by category (such as security or recommended), activate Filter by Category and add the appropriate patch categories from the list. Only patches of the selected categories will be installed. Others will be skipped. 9. Conrm your conguration with OK. The automatic online update does not automatically restart the system afterward. If there are package updates that require a system reboot, you need to do this manually. 30 Automatic Online Update SLES 12 SP44 YaST YaST is the installation and conguration tool for SUSE Linux Enterprise Server. It has a graphical interface and the capability to customize your system quickly during and after the installation. It can be used to set up hardware, congure the network, system services, and tune your security settings. 4.1 Advanced Key Combinations YaST has a set of advanced key combinations. Print Screen Take and save a screenshot. May not be available when YaST is running under some desktop environments. Shift – F4 Enable/disable the color palette optimized for vision impaired users. Shift – F7 Enable/disable logging of debug messages. Shift – F8 Open a le dialog to save log les to a non-standard location. Ctrl – Shift – Alt – D Send a DebugEvent. YaST modules can react to this by executing special debugging actions. The result depends on the specic YaST module. Ctrl – Shift – Alt – M Start/stop macro recorder. Ctrl – Shift – Alt – P Replay macro. Ctrl – Shift – Alt – S Show style sheet editor. Ctrl – Shift – Alt – T Dump widget tree to the log le. 31 Advanced Key Combinations SLES 12 SP4Ctrl – Shift – Alt – X Open a terminal window (xterm). Useful for installation process via VNC. Ctrl – Shift – Alt – Y Show widget tree browser. 32 Advanced Key Combinations SLES 12 SP45 YaST in Text Mode This section is intended for system administrators and experts who do not run an X server on their systems and depend on the text-based installation tool. It provides basic information about starting and operating YaST in text mode. YaST in text mode uses the ncurses library to provide an easy pseudo-graphical user interface. The ncurses library is installed by default. The minimum supported size of the terminal emulator in which to run YaST is 80x25 characters. FIGURE 5.1: MAIN WINDOW OF YAST IN TEXT MODE When you start YaST in text mode, the YaST control center appears (see Figure 5.1). The main window consists of three areas. The left frame features the categories to which the various modules belong. This frame is active when YaST is started and therefore it is marked by a bold white border. The active category is selected. The right frame provides an overview of the modules available in the active category. The bottom frame contains the buttons for Help and Quit. When you start the YaST control center, the category Software is selected automatically. Use ↓ and ↑ to change the category. To select a module from the category, activate the right frame with → and then use ↓ and ↑ to select the module. Keep the arrow keys pressed to scroll through the list of available modules. After selecting a module, press Enter to start it. 33 SLES 12 SP4Various buttons or selection elds in the module contain a highlighted letter (yellow by default). Use Alt – highlighted_letter to select a button directly instead of navigating there with →| . Exit the YaST control center by pressing Alt – Q or by selecting Quit and pressing Enter . Tip: Refreshing YaST Dialogs If a YaST dialog gets corrupted or distorted (for example, while resizing the window), press Ctrl – L to refresh and restore its contents. 5.1 Navigation in Modules The following description of the control elements in the YaST modules assumes that all function keys and Alt key combinations work and are not assigned to dierent global functions. Read Section 5.3, “Restriction of Key Combinations” for information about possible exceptions. Navigation among Buttons and Selection Lists Use →| to navigate among the buttons and frames containing selection lists. To navigate in reverse order, use Alt – →| or Shift – →| combinations. Navigation in Selection Lists Use the arrow keys ( ↑ and ↓ ) to navigate among the individual elements in an active frame containing a selection list. If individual entries within a frame exceed its width, use Shift – → or Shift – ← to scroll horizontally to the right and left. Alternatively, use Ctrl – E or Ctrl – A . This combination can also be used if using → or ← results in changing the active frame or the current selection list, as in the control center. Buttons, Radio Buttons, and Check Boxes To select buttons with empty square brackets (check boxes) or empty parentheses (radio buttons), press Space or Enter . Alternatively, radio buttons and check boxes can be selected directly with Alt – highlighted_letter . In this case, you do not need to conrm with Enter . If you navigate to an item with →| , press Enter to execute the selected action or activate the respective menu item. Function Keys 34 Navigation in Modules SLES 12 SP4The function keys ( F1 ... F12 ) enable quick access to the various buttons. Available function key combinations ( FX ) are shown in the bottom line of the YaST screen. Which function keys are actually mapped to which buttons depend on the active YaST module, because the dierent modules oer dierent buttons (Details, Info, Add, Delete, etc.). Use F10 for Accept, OK, Next, and Finish. Press F1 to access the YaST help. Using Navigation Tree in ncurses Mode Some YaST modules use a navigation tree in the left part of the window to select conguration dialogs. Use the arrow keys ( ↑ and ↓ ) to navigate in the tree. Use Space to open or close tree items. In ncurses mode, Enter must be pressed after a selection in the navigation tree to show the selected dialog. This is an intentional behavior to save time consuming redraws when browsing through the navigation tree. Selecting Software in the Software Installation Module Use the lters on the left side to limit the amount of displayed packages. Installed packages are marked with the letter i . To change the status of a package, press Space or Enter . Alternatively, use the Actions menu to select the needed status change (install, delete, update, taboo or lock). FIGURE 5.2: THE SOFTWARE INSTALLATION MODULE 35 Navigation in Modules SLES 12 SP45.2 Advanced Key Combinations YaST in text mode has a set of advanced key combinations. Shift – F1 Show a list of advanced hotkeys. Shift – F4 Change color schema. Ctrl – \ Quit the application. Ctrl – L Refresh screen. Ctrl – D F1 Show a list of advanced hotkeys. Ctrl – D Shift – D Dump dialog to the log le as a screenshot. Ctrl – D Shift – Y Open YDialogSpy to see the widget hierarchy. 5.3 Restriction of Key Combinations If your window manager uses global Alt combinations, the Alt combinations in YaST might not work. Keys like Alt or Shift can also be occupied by the settings of the terminal. Replacing Alt with Esc Alt shortcuts can be executed with Esc instead of Alt . For example, Esc – H replaces Alt – H . (First press Esc , then press H .) Backward and Forward Navigation with Ctrl – F and Ctrl – B If the Alt and Shift combinations are occupied by the window manager or the terminal, use the combinations Ctrl – F (forward) and Ctrl – B (backward) instead. Restriction of Function Keys 36 Advanced Key Combinations SLES 12 SP4The function keys ( F1 ... F12 ) are also used for functions. Certain function keys might be occupied by the terminal and may not be available for YaST. However, the Alt key combinations and function keys should always be fully available on a pure text console. 5.4 YaST Command Line Options Besides the text mode interface, YaST provides a pure command line interface. To get a list of YaST command line options, enter: yast -h 5.4.1 Starting the Individual Modules To save time, the individual YaST modules can be started directly. To start a module, enter: yast View a list of all module names available on your system with yast -l or yast --list . Start the network module, for example, with yast lan . 5.4.2 Installing Packages from the Command Line If you know a package name and the package is provided by any of your active installation repositories, you can use the command line option -i to install the package: yast -i or yast --install PACKAGE_NAME can be a single short package name (for example gvim ) installed with dependency checking, or the full path to an RPM package which is installed without dependency checking. If you need a command line based software management utility with functionality beyond what YaST provides, consider using Zypper. This utility uses the same software management library that is also the foundation for the YaST package manager. The basic usage of Zypper is covered in Section 6.1, “Using Zypper”. 37 YaST Command Line Options SLES 12 SP45.4.3 Command Line Parameters of the YaST Modules To use YaST functionality in scripts, YaST provides command line support for individual modules. Not all modules have command line support. To display the available options of a module, enter: yast help If a module does not provide command line support, the module is started in text mode and the following message appears: This YaST module does not support the command line interface. 38 Command Line Parameters of the YaST Modules SLES 12 SP46 Managing Software with Command Line Tools This chapter describes Zypper and RPM, two command line tools for managing software. For a denition of the terminology used in this context (for example, repository , patch , or update ) refer to Book “Deployment Guide”, Chapter 13 “Installing or Removing Software”, Section 13.1 “Definition of Terms”. 6.1 Using Zypper Zypper is a command line package manager for installing, updating and removing packages a well as for managing repositories. It is especially useful for accomplishing remote software management tasks or managing software from shell scripts. 6.1.1 General Usage The general syntax of Zypper is: zypper [--global-options] COMMAND  [--command-options] [arguments] The components enclosed in brackets are not required. See zypper help for a list of general options and all commands. To get help for a specic command, type zypper help COMMAND . Zypper Commands The simplest way to execute Zypper is to type its name, followed by a command. For example, to apply all needed patches to the system, use: tux > sudo zypper patch Global Options Additionally, you can choose from one or more global options by typing them immediately before the command: tux > sudo zypper --non-interactive patch In the above example, the option --non-interactive means that the command is run without asking anything (automatically applying the default answers). 39 Using Zypper SLES 12 SP4Command-Specific Options To use options that are specic to a particular command, type them immediately after the command: tux > sudo zypper patch --auto-agree-with-licenses In the above example, --auto-agree-with-licenses is used to apply all needed patches to a system without you being asked to conrm any licenses. Instead, license will be accepted automatically. Arguments Some commands require one or more arguments. For example, when using the command install , you need to specify which package or which packages you want to install: tux > sudo zypper install mplayer Some options also require a single argument. The following command will list all known patterns: tux > zypper search -t pattern You can combine all of the above. For example, the following command will install the aspell- de and aspell-fr packages from the factory repository while being verbose: tux > sudo zypper -v install --from factory aspell-de aspell-fr The --from option makes sure to keep all repositories enabled (for solving any dependencies) while requesting the package from the specied repository. Most Zypper commands have a dry-run option that does a simulation of the given command. It can be used for test purposes. tux > sudo zypper remove --dry-run MozillaFirefox Zypper supports the global --userdata STRING option. You can specify a string with this option, which gets written to Zypper''s log les and plug-ins (such as the Btrfs plug-in). It can be used to mark and identify transactions in log les. tux > sudo zypper --userdata STRING patch 40 General Usage SLES 12 SP46.1.2 Using Zypper Subcommands Zypper subcommands are executables that are stored in the zypper_execdir, /usr/lib/zypper/ commands . If a subcommand is not found in the zypper_execdir, Zypper automatically searches the rest of your $PATH for it. This enables writing your own local extensions and storing them in userspace. Executing subcommands in the Zypper shell, and using global Zypper options are not supported. List your available subcommands: tux > zypper help subcommand [...] Available zypper subcommands in ''/usr/lib/zypper/commands'' appstream-cache lifecycle migration search-packages Zypper subcommands available from elsewhere on your $PATH View the help screen for a subcommand: tux > zypper help appstream-cache 6.1.3 Installing and Removing Software with Zypper To install or remove packages, use the following commands: tux > sudo zypper install PACKAGE_NAME tux > sudo zypper remove PACKAGE_NAME Warning: Do Not Remove Mandatory System Packages Do not remove mandatory system packages like glibc , zypper , kernel . If they are removed, the system can become unstable or stop working altogether. 41 Using Zypper Subcommands SLES 12 SP46.1.3.1 Selecting Which Packages to Install or Remove There are various ways to address packages with the commands zypper install and zypper remove . By Exact Package Name tux > sudo zypper install MozillaFirefox By Exact Package Name and Version Number tux > sudo zypper install MozillaFirefox-52.2 By Repository Alias and Package Name tux > sudo zypper install mozilla:MozillaFirefox Where mozilla is the alias of the repository from which to install. By Package Name Using Wild Cards You can select all packages that have names starting or ending with a certain string. Use wild cards with care, especially when removing packages. The following command will install all packages starting with “Moz”: tux > sudo zypper install ''Moz*'' Tip: Removing all -debuginfo Packages When debugging a problem, you sometimes need to temporarily install a lot of - debuginfo packages which give you more information about running processes. After your debugging session nishes and you need to clean the environment, run the following: tux > sudo zypper remove ''*-debuginfo'' By Capability For example, if you want to install a Perl module without knowing the name of the package, capabilities come in handy: tux > sudo zypper install firefox By Capability, Hardware Architecture, or Version 42 Installing and Removing Software with Zypper SLES 12 SP4Together with a capability, you can specify a hardware architecture and a version: The name of the desired hardware architecture is appended to the capability after a full stop. For example, to specify the AMD64/Intel 64 architectures (which in Zypper is named x86_64 ), use: tux > sudo zypper install ''firefox.x86_64'' Versions must be appended to the end of the string and must be preceded by an operator: < (lesser than), <= (lesser than or equal), = (equal), >= (greater than or equal), > (greater than). tux > sudo zypper install ''firefox>=52.2'' You can also combine a hardware architecture and version requirement: tux > sudo zypper install ''firefox.x86_64>=52.2'' By Path to the RPM file You can also specify a local or remote path to a package: tux > sudo zypper install /tmp/install/MozillaFirefox.rpm tux > sudo zypper install http://download.example.com/MozillaFirefox.rpm 6.1.3.2 Combining Installation and Removal of Packages To install and remove packages simultaneously, use the +/- modiers. To install emacs and simultaneously remove vim , use: tux > sudo zypper install emacs -vim To remove emacs and simultaneously install vim , use: tux > sudo zypper remove emacs +vim To prevent the package name starting with the - being interpreted as a command option, always use it as the second argument. If this is not possible, precede it with -- : tux > sudo zypper install -emacs +vim # Wrong tux > sudo zypper install vim -emacs # Correct tux > sudo zypper install -- -emacs +vim # Correct tux > sudo zypper remove emacs +vim # Correct 43 Installing and Removing Software with Zypper SLES 12 SP46.1.3.3 Cleaning Up Dependencies of Removed Packages If (together with a certain package), you automatically want to remove any packages that become unneeded after removing the specied package, use the --clean-deps option: tux > sudo zypper rm --clean-deps PACKAGE_NAME 6.1.3.4 Using Zypper in Scripts By default, Zypper asks for a conrmation before installing or removing a selected package, or when a problem occurs. You can override this behavior using the --non-interactive option. This option must be given before the actual command ( install , remove , and patch ), as can be seen in the following: tux > sudo zypper --non-interactive install PACKAGE_NAME This option allows the use of Zypper in scripts and cron jobs. 6.1.3.5 Installing or Downloading Source Packages To install the corresponding source package of a package, use: tux > zypper source-install PACKAGE_NAME When executed as root , the default location to install source packages is /usr/src/ packages/ and ~/rpmbuild when run as user. These values can be changed in your local rpm conguration. This command will also install the build dependencies of the specied package. If you do not want this, add the switch -D : tux > sudo zypper source-install -D PACKAGE_NAME To install only the build dependencies use -d . tux > sudo zypper source-install -d PACKAGE_NAME Of course, this will only work if you have the repository with the source packages enabled in your repository list (it is added by default, but not enabled). See Section 6.1.6, “Managing Repositories with Zypper” for details on repository management. A list of all source packages available in your repositories can be obtained with: tux > zypper search -t srcpackage 44 Installing and Removing Software with Zypper SLES 12 SP4You can also download source packages for all installed packages to a local directory. To download source packages, use: tux > zypper source-download The default download directory is /var/cache/zypper/source-download . You can change it using the --directory option. To only show missing or extraneous packages without downloading or deleting anything, use the --status option. To delete extraneous source packages, use the --delete option. To disable deleting, use the --no-delete option. 6.1.3.6 Installing Packages from Disabled Repositories Normally you can only install or refresh packages from enabled repositories. The --plus- content TAG option helps you specify repositories to be refreshed, temporarily enabled during the current Zypper session, and disabled after it completes. For example, to enable repositories that may provide additional -debuginfo or -debugsource packages, use --plus-content debug . You can specify this option multiple times. To temporarily enable such ''debug'' repositories to install a specic -debuginfo package, use the option as follows: tux > sudo zypper --plus-content debug \ install "debuginfo(build-id)=eb844a5c20c70a59fc693cd1061f851fb7d046f4" The build-id string is reported by gdb for missing debuginfo packages. 6.1.3.7 Utilities To verify whether all dependencies are still fullled and to repair missing dependencies, use: tux > zypper verify In addition to dependencies that must be fullled, some packages “recommend” other packages. These recommended packages are only installed if actually available and installable. In case recommended packages were made available after the recommending package has been installed (by adding additional packages or hardware), use the following command: tux > sudo zypper install-new-recommends This command is very useful after plugging in a Web cam or Wi-Fi device. It will install drivers for the device and related software, if available. Drivers and related software are only installable if certain hardware dependencies are fullled. 45 Installing and Removing Software with Zypper SLES 12 SP46.1.4 Updating Software with Zypper There are three dierent ways to update software using Zypper: by installing patches, by installing a new version of a package or by updating the entire distribution. The latter is achieved with zypper dist-upgrade . Upgrading SUSE Linux Enterprise Server is discussed in Book “Deployment Guide”, Chapter 19 “Upgrading SUSE Linux Enterprise”. 6.1.4.1 Installing All Needed Patches To install all ocially released patches that apply to your system, run: tux > sudo zypper patch All patches available from repositories congured on your computer are checked for their relevance to your installation. If they are relevant (and not classied as optional or feature ), they are installed immediately. Note that the ocial update repository is only available after registering your SUSE Linux Enterprise Server installation. If a patch that is about to be installed includes changes that require a system reboot, you will be warned before. The plain zypper patch command does not apply patches from third party repositories. To update also the third party repositories, use the with-update command option as follows: tux > sudo zypper patch --with-update To install also optional patches, use: tux > sudo zypper patch --with-optional To install all patches relating to a specic Bugzilla issue, use: tux > sudo zypper patch --bugzilla=NUMBER To install all patches relating to a specic CVE database entry, use: tux > sudo zypper patch --cve=NUMBER For example, to install a security patch with the CVE number CVE-2010-2713 , execute: tux > sudo zypper patch --cve=CVE-2010-2713 46 Updating Software with Zypper SLES 12 SP4To install only patches which aect Zypper and the package management itself, use: tux > sudo zypper patch --updatestack-only Bear in mind that other command options that would also update other repositories will be dropped if you use the updatestack-only command option. 6.1.4.2 Listing Patches To nd out whether patches are available, Zypper allows viewing the following information: Number of Needed Patches To list the number of needed patches (patches that apply to your system but are not yet installed), use patch-check : tux > zypper patch-check Loading repository data... Reading installed packages... 5 patches needed (1 security patch) This command can be combined with the --updatestack-only option to list only the patches which aect Zypper and the package management itself. List of Needed Patches To list all needed patches (patches that apply to your system but are not yet installed), use list-patches : tux > zypper list-patches Loading repository data... Reading installed packages... Repository | Name | Version | Category | Status | Summary ---------------+-------------+---------+----------+---------+--------- SLES12-Updates | SUSE-2014-8 | 1 | security | needed | openssl: Update for OpenSSL List of All Patches To list all patches available for SUSE Linux Enterprise Server, regardless of whether they are already installed or apply to your installation, use zypper patches . It is also possible to list and install patches relevant to specic issues. To list specic patches, use the zypper list-patches command with the following options: By Bugzilla Issues 47 Updating Software with Zypper SLES 12 SP4To list all needed patches that relate to Bugzilla issues, use the option --bugzilla . To list patches for a specic bug, you can also specify a bug number: --bugzilla=NUMBER . To search for patches relating to multiple Bugzilla issues, add commas between the bug numbers, for example: tux > zypper list-patches --bugzilla=972197,956917 By CVE Number To list all needed patches that relate to an entry in the CVE database (Common Vulnerabilities and Exposures), use the option --cve . To list patches for a specic CVE database entry, you can also specify a CVE number: -- cve=NUMBER . To search for patches relating to multiple CVE database entries, add commas between the CVE numbers, for example: tux > zypper list-patches --bugzilla=CVE-2016-2315,CVE-2016-2324 To list all patches regardless of whether they are needed, use the option --all additionally. For example, to list all patches with a CVE number assigned, use: tux > zypper list-patches --all --cve Issue | No. | Patch | Category | Severity | Status ------+---------------+-------------------+-------------+-----------+---------- cve | CVE-2015-0287 | SUSE-SLE-Module.. | recommended | moderate | needed cve | CVE-2014-3566 | SUSE-SLE-SERVER.. | recommended | moderate | not needed [...] 6.1.4.3 Installing New Package Versions If a repository contains only new packages, but does not provide patches, zypper patch does not show any eect. To update all installed packages with newer available versions (while maintaining system integrity), use: tux > sudo zypper update To update individual packages, specify the package with either the update or install command: tux > sudo zypper update PACKAGE_NAME tux > sudo zypper install PACKAGE_NAME A list of all new installable packages can be obtained with the command: tux > zypper list-updates 48 Updating Software with Zypper SLES 12 SP4Note that this command only lists packages that match the following criteria: has the same vendor like the already installed package, is provided by repositories with at least the same priority than the already installed package, is installable (all dependencies are satised). A list of all new available packages (regardless whether installable or not) can be obtained with: tux > sudo zypper list-updates --all To nd out why a new package cannot be installed, use the zypper install or zypper update command as described above. 6.1.4.4 Identifying Orphaned Packages Whenever you remove a repository from Zypper or upgrade your system, some packages can get in an “orphaned” state. These orphaned packages belong to no active repository anymore. The following command gives you a list of these: tux > sudo zypper packages --orphaned With this list, you can decide if a package is still needed or can be removed safely. 6.1.5 Identifying Processes and Services Using Deleted Files When patching, updating or removing packages, there may be running processes on the system which continue to use les having been deleted by the update or removal. Use zypper ps to list processes using deleted les. In case the process belongs to a known service, the service name is listed, making it easy to restart the service. By default zypper ps shows a table: tux > zypper ps PID | PPID | UID | User | Command | Service | Files ------+------+-----+-------+--------------+--------------+------------------- 814 | 1 | 481 | avahi | avahi-daemon | avahi-daemon | /lib64/ld-2.19.s-> | | | | | | /lib64/libdl-2.1-> | | | | | | /lib64/libpthrea-> | | | | | | /lib64/libc-2.19-> [...] PID: ID of the process 49 Identifying Processes and Services Using Deleted Files SLES 12 SP4PPID: ID of the parent process UID: ID of the user running the process Login: Login name of the user running the process Command: Command used to execute the process Service: Service name (only if command is associated with a system service) Files: The list of the deleted les The output format of zypper ps can be controlled as follows: zypper ps -s Create a short table not showing the deleted les. tux > zypper ps -s PID | PPID | UID | User | Command | Service ------+------+------+---------+--------------+-------------- 814 | 1 | 481 | avahi | avahi-daemon | avahi-daemon 817 | 1 | 0 | root | irqbalance | irqbalance 1567 | 1 | 0 | root | sshd | sshd 1761 | 1 | 0 | root | master | postfix 1764 | 1761 | 51 | postfix | pickup | postfix 1765 | 1761 | 51 | postfix | qmgr | postfix 2031 | 2027 | 1000 | tux | bash | zypper ps -ss Show only processes associated with a system service. PID | PPID | UID | User | Command | Service ------+------+------+---------+--------------+-------------- 814 | 1 | 481 | avahi | avahi-daemon | avahi-daemon 817 | 1 | 0 | root | irqbalance | irqbalance 1567 | 1 | 0 | root | sshd | sshd 1761 | 1 | 0 | root | master | postfix 1764 | 1761 | 51 | postfix | pickup | postfix 1765 | 1761 | 51 | postfix | qmgr | postfix zypper ps -sss Only show system services using deleted les. avahi-daemon irqbalance postfix sshd zypper ps --print "systemctl status %s" Show the commands to retrieve status information for services which might need a restart. 50 Identifying Processes and Services Using Deleted Files SLES 12 SP4systemctl status avahi-daemon systemctl status irqbalance systemctl status postfix systemctl status sshd For more information about service handling refer to Chapter 13, The systemd Daemon. 6.1.6 Managing Repositories with Zypper All installation or patch commands of Zypper rely on a list of known repositories. To list all repositories known to the system, use the command: tux > zypper repos The result will look similar to the following output: EXAMPLE 6.1: ZYPPER—LIST OF KNOWN REPOSITORIES tux > zypper repos # | Alias | Name | Enabled | Refresh --+--------------+---------------+---------+-------- 1 | SLEHA-12-GEO | SLEHA-12-GEO | Yes | No 2 | SLEHA-12 | SLEHA-12 | Yes | No 3 | SLES12 | SLES12 | Yes | No When specifying repositories in various commands, an alias, URI or repository number from the zypper repos command output can be used. A repository alias is a short version of the repository name for use in repository handling commands. Note that the repository numbers can change after modifying the list of repositories. The alias will never change by itself. By default, details such as the URI or the priority of the repository are not displayed. Use the following command to list all details: tux > zypper repos -d 6.1.6.1 Adding Repositories To add a repository, run tux > sudo zypper addrepo URI ALIAS URI can either be an Internet repository, a network resource, a directory or a CD or DVD (see http://en.opensuse.org/openSUSE:Libzypp_URIs for details). The ALIAS is a shorthand and unique identier of the repository. You can freely choose it, with the only exception that it needs to be unique. Zypper will issue a warning if you specify an alias that is already in use. 51 Managing Repositories with Zypper SLES 12 SP46.1.6.2 Refreshing Repositories zypper enables you to fetch changes in packages from congured repositories. To fetch the changes, run: tux > sudo zypper refresh Note: Default Behavior of zypper By default, some commands perform refresh automatically, so you do not need to run the command explicitly. The refresh command enables you to view changes also in disabled repositories, by using the --plus-content option: tux > sudo zypper --plus-content refresh This option fetches changes in repositories, but keeps the disabled repositories in the same state —disabled. 6.1.6.3 Removing Repositories To remove a repository from the list, use the command zypper removerepo together with the alias or number of the repository you want to delete. For example, to remove the repository SLEHA-12-GEO from Example 6.1, “Zypper—List of Known Repositories”, use one of the following commands: tux > sudo zypper removerepo 1 tux > sudo zypper removerepo "SLEHA-12-GEO" 6.1.6.4 Modifying Repositories Enable or disable repositories with zypper modifyrepo . You can also alter the repository''s properties (such as refreshing behavior, name or priority) with this command. The following command will enable the repository named updates , turn on auto-refresh and set its priority to 20: tux > sudo zypper modifyrepo -er -p 20 ''updates'' 52 Managing Repositories with Zypper SLES 12 SP4Modifying repositories is not limited to a single repository—you can also operate on groups: -a : all repositories -l : local repositories -t : remote repositories -m TYPE : repositories of a certain type (where TYPE can be one of the following: http , https , ftp , cd , dvd , dir , file , cifs , smb , nfs , hd , iso ) To rename a repository alias, use the renamerepo command. The following example changes the alias from Mozilla Firefox to firefox : tux > sudo zypper renamerepo ''Mozilla Firefox'' firefox 6.1.7 Querying Repositories and Packages with Zypper Zypper oers various methods to query repositories or packages. To get lists of all products, patterns, packages or patches available, use the following commands: tux > zypper products tux > zypper patterns tux > zypper packages tux > zypper patches To query all repositories for certain packages, use search . To get information regarding particular packages, use the info command. 6.1.7.1 zypper search Usage The zypper search command works on package names, or, optionally, on package summaries and descriptions. String wrapped in / are interpreted as regular expressions. By default, the search is not case-sensitive. Simple search for a package name containing fire tux > zypper search "fire" Simple search for the exact package MozillaFirefox tux > zypper search --match-exact "MozillaFirefox" 53 Querying Repositories and Packages with Zypper SLES 12 SP4Also search in package descriptions and summaries tux > zypper search -d fire Only display packages not already installed tux > zypper search -u fire Display packages containing the string fir not followed be e tux > zypper se "/fir[^e]/" 6.1.7.2 zypper what-provides Usage To search for packages which provide a special capability, use the command what-provides . For example, if you want to know which package provides the Perl module SVN::Core , use the following command: tux > zypper what-provides ''perl(SVN::Core)'' The what-provides PACKAGE_NAME is similar to rpm -q --whatprovides PACKAGE_NAME , but RPM is only able to query the RPM database (that is the database of all installed packages). Zypper, on the other hand, will tell you about providers of the capability from any repository, not only those that are installed. 6.1.7.3 zypper info Usage To query single packages, use info with an exact package name as an argument. This displays detailed information about a package. In case the package name does not match any package name from repositories, the command outputs detailed information for non-package matches. If you request a specic type (by using the -t option) and the type does not exist, the command outputs other available matches but without detailed information. If you specify a source package, the command displays binary packages built from the source package. If you specify a binary package, the command outputs the source packages used to build the binary package. To also show what is required/recommended by the package, use the options --requires and --recommends : tux > zypper info --requires MozillaFirefox 54 Querying Repositories and Packages with Zypper SLES 12 SP46.1.8 Configuring Zypper Zypper now comes with a conguration le, allowing you to permanently change Zypper''s behavior (either system-wide or user-specic). For system-wide changes, edit /etc/zypp/ zypper.conf . For user-specic changes, edit ~/.zypper.conf . If ~/.zypper.conf does not yet exist, you can use /etc/zypp/zypper.conf as a template: copy it to ~/.zypper.conf and adjust it to your liking. Refer to the comments in the le for help about the available options. 6.1.9 Troubleshooting If you have trouble accessing packages from congured repositories (for example, Zypper cannot nd a certain package even though you know it exists in one of the repositories), refreshing the repositories may help: tux > sudo zypper refresh If that does not help, try tux > sudo zypper refresh -fdb This forces a complete refresh and rebuild of the database, including a forced download of raw metadata. 6.1.10 Zypper Rollback Feature on Btrfs File System If the Btrfs le system is used on the root partition and snapper is installed, Zypper automatically calls snapper when committing changes to the le system to create appropriate le system snapshots. These snapshots can be used to revert any changes made by Zypper. See Chapter 7, System Recovery and Snapshot Management with Snapper for more information. 6.1.11 For More Information For more information on managing software from the command line, enter zypper help , zypper help  COMMAND or refer to the zypper(8) man page. For a complete and detailed command reference, cheat sheets with the most important commands, and information on how to use Zypper in scripts and applications, refer to http://en.opensuse.org/ SDB:Zypper_usage . A list of software changes for the latest SUSE Linux Enterprise Server version can be found at http://en.opensuse.org/openSUSE:Zypper versions . 55 Configuring Zypper SLES 12 SP46.2 RPM—the Package Manager RPM (RPM Package Manager) is used for managing software packages. Its main commands are rpm and rpmbuild . The powerful RPM database can be queried by the users, system administrators and package builders for detailed information about the installed software. Essentially, rpm has ve modes: installing, uninstalling (or updating) software packages, rebuilding the RPM database, querying RPM bases or individual RPM archives, integrity checking of packages and signing packages. rpmbuild can be used to build installable packages from pristine sources. Installable RPM archives are packed in a special binary format. These archives consist of the program les to install and certain meta information used during the installation by rpm to congure the software package or stored in the RPM database for documentation purposes. RPM archives normally have the extension .rpm . Tip: Software Development Packages For several packages, the components needed for software development (libraries, headers, include les, etc.) have been put into separate packages. These development packages are only needed if you want to compile software yourself (for example, the most recent GNOME packages). They can be identied by the name extension -devel , such as the packages alsa-devel and gimp-devel . 6.2.1 Verifying Package Authenticity RPM packages have a GPG signature. To verify the signature of an RPM package, use the command rpm --checksig  PACKAGE -1.2.3.rpm to determine whether the package originates from SUSE or from another trustworthy facility. This is especially recommended for update packages from the Internet. While xing issues in the operating system, you might need to install a Problem Temporary Fix (PTF) into a production system. The packages provided by SUSE are signed against a special PTF key. However, in contrast to SUSE Linux Enterprise 11, this key is not imported by default on SUSE Linux Enterprise 12 systems. To manually import the key, use the following command: tux > sudo rpm --import \ /usr/share/doc/packages/suse-build-key/suse_ptf_key.asc After importing the key, you can install PTF packages on your system. 56 RPM—the Package Manager SLES 12 SP46.2.2 Managing Packages: Install, Update, and Uninstall Normally, the installation of an RPM archive is quite simple: rpm -i PACKAGE .rpm. With this command the package is installed, but only if its dependencies are fullled and if there are no conicts with other packages. With an error message, rpm requests those packages that need to be installed to meet dependency requirements. In the background, the RPM database ensures that no conicts arise—a specic le can only belong to one package. By choosing dierent options, you can force rpm to ignore these defaults, but this is only for experts. Otherwise, you risk compromising the integrity of the system and possibly jeopardize the ability to update the system. The options -U or --upgrade and -F or --freshen can be used to update a package (for example, rpm -F PACKAGE .rpm). This command removes the les of the old version and immediately installs the new les. The dierence between the two versions is that -U installs packages that previously did not exist in the system, while -F merely updates previously installed packages. When updating, rpm updates conguration les carefully using the following strategy: If a conguration le was not changed by the system administrator, rpm installs the new version of the appropriate le. No action by the system administrator is required. If a conguration le was changed by the system administrator before the update, rpm saves the changed le with the extension .rpmorig or .rpmsave (backup le) and installs the version from the new package. This is done only if the originally installed le and the newer version are dierent. If this is the case, compare the backup le ( .rpmorig or .rpmsave ) with the newly installed le and make your changes again in the new le. Afterward, delete all .rpmorig and .rpmsave les to avoid problems with future updates. .rpmnew les appear if the conguration le already exists and if the noreplace label was specied in the .spec le. Following an update, .rpmsave and .rpmnew les should be removed after comparing them, so they do not obstruct future updates. The .rpmorig extension is assigned if the le has not previously been recognized by the RPM database. Otherwise, .rpmsave is used. In other words, .rpmorig results from updating from a foreign format to RPM. .rpmsave results from updating from an older RPM to a newer RPM. .rpmnew does not disclose any information to whether the system administrator has made any changes 57 Managing Packages: Install, Update, and Uninstall SLES 12 SP4to the conguration le. A list of these les is available in /var/adm/rpmconfigcheck . Some conguration les (like /etc/httpd/httpd.conf ) are not overwritten to allow continued operation. The -U switch is not just an equivalent to uninstalling with the -e option and installing with the -i option. Use -U whenever possible. To remove a package, enter rpm -e PACKAGE . This command only deletes the package if there are no unresolved dependencies. It is theoretically impossible to delete Tcl/Tk, for example, as long as another application requires it. Even in this case, RPM calls for assistance from the database. If such a deletion is, for whatever reason, impossible (even if no additional dependencies exist), it may be helpful to rebuild the RPM database using the option -- rebuilddb . 6.2.3 Delta RPM Packages Delta RPM packages contain the dierence between an old and a new version of an RPM package. Applying a delta RPM onto an old RPM results in a completely new RPM. It is not necessary to have a copy of the old RPM because a delta RPM can also work with an installed RPM. The delta RPM packages are even smaller in size than patch RPMs, which is an advantage when transferring update packages over the Internet. The drawback is that update operations with delta RPMs involved consume considerably more CPU cycles than plain or patch RPMs. The makedeltarpm and applydelta binaries are part of the delta RPM suite (package deltarpm ) and help you create and apply delta RPM packages. With the following commands, you can create a delta RPM called new.delta.rpm . The following command assumes that old.rpm and new.rpm are present: tux > sudo makedeltarpm old.rpm new.rpm new.delta.rpm Using applydeltarpm , you can reconstruct the new RPM from the le system if the old package is already installed: tux > sudo applydeltarpm new.delta.rpm new.rpm To derive it from the old RPM without accessing the le system, use the -r option: tux > sudo applydeltarpm -r old.rpm new.delta.rpm new.rpm See /usr/share/doc/packages/deltarpm/README for technical details. 58 Delta RPM Packages SLES 12 SP46.2.4 RPM Queries With the -q option rpm initiates queries, making it possible to inspect an RPM archive (by adding the option -p ) and to query the RPM database of installed packages. Several switches are available to specify the type of information required. See Table 6.1, “The Most Important RPM Query Options”. TABLE 6.1: THE MOST IMPORTANT RPM QUERY OPTIONS -i Package information -l File list -f FILE Query the package that contains the le FILE (the full path must be specied with FILE ) -s File list with status information (implies -l ) -d List only documentation les (implies -l ) -c List only conguration les (implies -l ) --dump File list with complete details (to be used with -l , -c , or -d ) --provides List features of the package that another package can request with --requires --requires , -R Capabilities the package requires --scripts Installation scripts (preinstall, postinstall, uninstall) For example, the command rpm -q -i wget displays the information shown in Example 6.2, “rpm -q -i wget”. EXAMPLE 6.2: rpm -q -i wget Name : wget Version : 1.14 Release : 17.1 Architecture: x86_64 59 RPM Queries SLES 12 SP4Install Date: Mon 30 Jan 2017 14:01:29 CET Group : Productivity/Networking/Web/Utilities Size : 2046483 License : GPL-3.0+ Signature : RSA/SHA256, Thu 08 Dec 2016 07:48:44 CET, Key ID 70af9e8139db7c82 Source RPM : wget-1.14-17.1.src.rpm Build Date : Thu 08 Dec 2016 07:48:34 CET Build Host : sheep09 Relocations : (not relocatable) Packager : https://www.suse.com/ Vendor : SUSE LLC URL : http://www.gnu.org/software/wget/ Summary : A Tool for Mirroring FTP and HTTP Servers Description : Wget enables you to retrieve WWW documents or FTP files from a server. This can be done in script files or via the command line. Distribution: SUSE Linux Enterprise 12 The option -f only works if you specify the complete le name with its full path. Provide as many le names as desired. For example: tux > rpm -q -f /bin/rpm /usr/bin/wget rpm-4.11.2-15.1.x86_64 wget-1.14-17.1.x86_64 If only part of the le name is known, use a shell script as shown in Example 6.3, “Script to Search for Packages”. Pass the partial le name to the script shown as a parameter when running it. EXAMPLE 6.3: SCRIPT TO SEARCH FOR PACKAGES #! /bin/sh for i in $(rpm -q -a -l | grep $1); do echo "\"$i\" is in package:" rpm -q -f $i echo "" done The command rpm -q --changelog PACKAGE displays a detailed list of change information about a specic package, sorted by date. With the installed RPM database, verication checks can be made. Initiate these with -V , or --verify . With this option, rpm shows all les in a package that have been changed since installation. rpm uses eight character symbols to give some hints about the following changes: TABLE 6.2: RPM VERIFY OPTIONS 5 MD5 check sum 60 RPM Queries SLES 12 SP4S File size L Symbolic link T Modication time D Major and minor device numbers U Owner G Group M Mode (permissions and le type) In the case of conguration les, the letter c is printed. For example, for changes to /etc/ wgetrc ( wget package): tux > rpm -V wget S.5....T c /etc/wgetrc The les of the RPM database are placed in /var/lib/rpm . If the partition /usr has a size of 1 GB, this database can occupy nearly 30 MB, especially after a complete update. If the database is much larger than expected, it is useful to rebuild the database with the option --rebuilddb . Before doing this, make a backup of the old database. The cron script cron.daily makes daily copies of the database (packed with gzip) and stores them in /var/adm/backup/rpmdb . The number of copies is controlled by the variable MAX_RPMDB_BACKUPS (default: 5 ) in /etc/ sysconfig/backup . The size of a single backup is approximately 1 MB for 1 GB in /usr . 6.2.5 Installing and Compiling Source Packages All source packages carry a .src.rpm extension (source RPM). Note: Installed Source Packages Source packages can be copied from the installation medium to the hard disk and unpacked with YaST. They are not, however, marked as installed ( [i] ) in the package manager. This is because the source packages are not entered in the RPM database. Only installed operating system software is listed in the RPM database. When you “install” a source package, only the source code is added to the system. 61 Installing and Compiling Source Packages SLES 12 SP4The following directories must be available for rpm and rpmbuild in /usr/src/packages (unless you specied custom settings in a le like /etc/rpmrc ): SOURCES for the original sources ( .tar.bz2 or .tar.gz les, etc.) and for distribution-specic adjustments (mostly .diff or .patch les) SPECS for the .spec les, similar to a meta Makele, which control the build process BUILD all the sources are unpacked, patched and compiled in this directory RPMS where the completed binary packages are stored SRPMS here are the source RPMs When you install a source package with YaST, all the necessary components are installed in / usr/src/packages : the sources and the adjustments in SOURCES and the relevant .spec le in SPECS . Warning: System Integrity Do not experiment with system components ( glibc , rpm , etc.), because this endangers the stability of your system. The following example uses the wget.src.rpm package. After installing the source package, you should have les similar to those in the following list: /usr/src/packages/SOURCES/wget-1.11.4.tar.bz2 /usr/src/packages/SOURCES/wgetrc.patch /usr/src/packages/SPECS/wget.spec rpmbuild -bX /usr/src/packages/SPECS/wget.spec starts the compilation. X is a wild card for various stages of the build process (see the output of --help or the RPM documentation for details). The following is merely a brief explanation: -bp 62 Installing and Compiling Source Packages SLES 12 SP4Prepare sources in /usr/src/packages/BUILD : unpack and patch. -bc Do the same as -bp , but with additional compilation. -bi Do the same as -bp , but with additional installation of the built software. Caution: if the package does not support the BuildRoot feature, you might overwrite conguration les. -bb Do the same as -bi , but with the additional creation of the binary package. If the compile was successful, the binary should be in /usr/src/packages/RPMS . -ba Do the same as -bb , but with the additional creation of the source RPM. If the compilation was successful, the binary should be in /usr/src/packages/SRPMS . --short-circuit Skip some steps. The binary RPM created can now be installed with rpm -i or, preferably, with rpm -U . Installation with rpm makes it appear in the RPM database. Keep in mind, the BuildRoot directive in the spec le is deprecated since SUSE Linux Enterprise Server 12. If you still need this feature, use the --buildroot option as a workaround. For more detailed background information, see the support database at https://www.suse.com/support/kb/ doc?id=7017104 . 6.2.6 Compiling RPM Packages with build The danger with many packages is that unwanted les are added to the running system during the build process. To prevent this use build , which creates a dened environment in which the package is built. To establish this chroot environment, the build script must be provided with a complete package tree. This tree can be made available on the hard disk, via NFS, or from DVD. Set the position with build --rpms DIRECTORY . Unlike rpm , the build command looks for the .spec le in the source directory. To build wget (like in the above example) with the DVD mounted in the system under /media/dvd , use the following commands as root : root # cd /usr/src/packages/SOURCES/ root # mv ../SPECS/wget.spec . 63 Compiling RPM Packages with build SLES 12 SP4root # build --rpms /media/dvd/suse/ wget.spec Subsequently, a minimum environment is established at /var/tmp/build-root . The package is built in this environment. Upon completion, the resulting packages are located in /var/tmp/ build-root/usr/src/packages/RPMS . The build script oers several additional options. For example, cause the script to prefer your own RPMs, omit the initialization of the build environment or limit the rpm command to one of the above-mentioned stages. Access additional information with build --help and by reading the build man page. 6.2.7 Tools for RPM Archives and the RPM Database Midnight Commander ( mc ) can display the contents of RPM archives and copy parts of them. It represents archives as virtual le systems, oering all usual menu options of Midnight Commander. Display the HEADER with F3 . View the archive structure with the cursor keys and Enter . Copy archive components with F5 . A full-featured package manager is available as a YaST module. For details, see Book “Deployment Guide”, Chapter 13 “Installing or Removing Software”. 64 Tools for RPM Archives and the RPM Database SLES 12 SP47 System Recovery and Snapshot Management with Snapper Snapper allows creating and managing le system snapshots. File system snapshots allow keeping a copy of the state of a le system at a certain point of time. The standard setup of Snapper is designed to allow rolling back system changes. However, you can also use it to create on-disk backups of user data. As the basis for this functionality, Snapper uses the Btrfs le system or thinly-provisioned LVM volumes with an XFS or Ext4 le system. Snapper has a command-line interface and a YaST interface. Snapper lets you create and manage le system snapshots on the following types of le systems: Btrfs, a copy-on-write le system for Linux that natively supports le system snapshots of subvolumes. (Subvolumes are separately mountable le systems within a physical partition.) You can also boot from Btrfs snapshots. For more information, see Section 7.3, “System Rollback by Booting from Snapshots”. Thinly-provisioned LVM volumes formatted with XFS or Ext4. Using Snapper, you can perform the following tasks: Undo system changes made by zypper and YaST. See Section 7.2, “Using Snapper to Undo Changes” for details. Restore les from previous snapshots. See Section 7.2.2, “Using Snapper to Restore Files” for details. Do a system rollback by booting from a snapshot. See Section 7.3, “System Rollback by Booting from Snapshots” for details. Manually create and manage snapshots, within the running system. See Section  7.6, “Manually Creating and Managing Snapshots” for details. 65 SLES 12 SP47.1 Default Setup Snapper on SUSE Linux Enterprise Server is set up as an undo and recovery tool for system changes. By default, the root partition ( / ) of SUSE Linux Enterprise Server is formatted with Btrfs . Taking snapshots is automatically enabled if the root partition ( / ) is big enough (more than approximately 16 GB). By default, snapshots are disabled on partitions other than / . Tip: Enabling Snapper in the Installed System If you disabled Snapper during the installation, you can enable it at any time later. To do so, create a default Snapper conguration for the root le system by running: tux > sudo snapper -c root create-config / Afterward enable the dierent snapshot types as described in Section 7.1.3.1, “Disabling/ Enabling Snapshots”. Note that on a Btrfs root le system, snapshots require a le system with subvolumes set up as proposed by the installer and a partition size of at least 16 GB. When a snapshot is created, both the snapshot and the original point to the same blocks in the le system. So, initially a snapshot does not occupy additional disk space. If data in the original le system is modied, changed data blocks are copied while the old data blocks are kept for the snapshot. Therefore, a snapshot occupies the same amount of space as the data modied. So, over time, the amount of space a snapshot allocates, constantly grows. As a consequence, deleting les from a Btrfs le system containing snapshots may not free disk space! Note: Snapshot Location Snapshots always reside on the same partition or subvolume on which the snapshot has been taken. It is not possible to store snapshots on a dierent partition or subvolume. As a result, partitions containing snapshots need to be larger than partitions not containing snapshots. The exact amount depends strongly on the number of snapshots you keep and the amount of data modications. As a rule of thumb, give partitions twice as much space as you normally would. To prevent disks from running out of space, old snapshots are automatically cleaned up. Refer to Section 7.1.3.4, “Controlling Snapshot Archiving” for details. 66 Default Setup SLES 12 SP47.1.1 Types of Snapshots Although snapshots themselves do not dier in a technical sense, we distinguish between three types of snapshots, based on the events that trigger them: Timeline Snapshots A single snapshot is created every hour. Old snapshots are automatically deleted. By default, the rst snapshot of the last ten days, months, and years are kept. Timeline snapshots are disabled by default. Installation Snapshots Whenever one or more packages are installed with YaST or Zypper, a pair of snapshots is created: one before the installation starts (“Pre”) and another one after the installation has nished (“Post”). In case an important system component such as the kernel has been installed, the snapshot pair is marked as important ( important=yes ). Old snapshots are automatically deleted. By default the last ten important snapshots and the last ten “regular” (including administration snapshots) snapshots are kept. Installation snapshots are enabled by default. Administration Snapshots Whenever you administrate the system with YaST, a pair of snapshots is created: one when a YaST module is started (“Pre”) and another when the module is closed (“Post”). Old snapshots are automatically deleted. By default the last ten important snapshots and the last ten “regular” snapshots (including installation snapshots) are kept. Administration snapshots are enabled by default. 7.1.2 Directories That Are Excluded from Snapshots Some directories need to be excluded from snapshots for dierent reasons. The following list shows all directories that are excluded: /boot/grub2/i386-pc , /boot/grub2/x86_64-efi , /boot/grub2/powerpc-ieee1275 , / boot/grub2/s390x-emu A rollback of the boot loader conguration is not supported. The directories listed above are architecture-specic. The rst two directories are present on AMD64/Intel 64 machines, the latter two on IBM POWER and on IBM z Systems, respectively. /home 67 Types of Snapshots SLES 12 SP4If /home does not reside on a separate partition, it is excluded to avoid data loss on rollbacks. /opt , /var/opt Third-party products usually get installed to /opt . It is excluded to avoid uninstalling these applications on rollbacks. /srv Contains data for Web and FTP servers. It is excluded to avoid data loss on rollbacks. /tmp , /var/tmp , /var/cache , /var/crash All directories containing temporary les and caches are excluded from snapshots. /usr/local This directory is used when manually installing software. It is excluded to avoid uninstalling these installations on rollbacks. /var/lib/libvirt/images The default location for virtual machine images managed with libvirt. Excluded to ensure virtual machine images are not replaced with older versions during a rollback. By default, this subvolume is created with the option no copy on write . /var/lib/mailman , /var/spool Directories containing mails or mail queues are excluded to avoid a loss of mails after a rollback. /var/lib/named Contains zone data for the DNS server. Excluded from snapshots to ensure a name server can operate after a rollback. /var/lib/mariadb , /var/lib/mysql , /var/lib/pgqsl These directories contain database data. By default, these subvolumes are created with the option no copy on write . /var/log Log le location. Excluded from snapshots to allow log le analysis after the rollback of a broken system. 68 Directories That Are Excluded from Snapshots SLES 12 SP47.1.3 Customizing the Setup SUSE Linux Enterprise Server comes with a reasonable default setup, which should be sucient for most use cases. However, all aspects of taking automatic snapshots and snapshot keeping can be congured according to your needs. 7.1.3.1 Disabling/Enabling Snapshots Each of the three snapshot types (timeline, installation, administration) can be enabled or disabled independently. Disabling/Enabling Timeline Snapshots Enabling. snapper-c root set-config "TIMELINE_CREATE=yes" Disabling. snapper -c root set-config "TIMELINE_CREATE=no" Timeline snapshots are enabled by default, except for the root partition. Disabling/Enabling Installation Snapshots Enabling: Install the package snapper-zypp-plugin Disabling: Uninstall the package snapper-zypp-plugin Installation snapshots are enabled by default. Disabling/Enabling Administration Snapshots Enabling: Set USE_SNAPPER to yes in /etc/sysconfig/yast2 . Disabling: Set USE_SNAPPER to no in /etc/sysconfig/yast2 . Administration snapshots are enabled by default. 7.1.3.2 Controlling Installation Snapshots Taking snapshot pairs upon installing packages with YaST or Zypper is handled by the snapper- zypp-plugin . An XML conguration le, /etc/snapper/zypp-plugin.conf denes, when to make snapshots. By default the le looks like the following: 1 2 3 4 kernel-* 3 5 dracut 69 Customizing the Setup SLES 12 SP46 glibc 7 systemd* 8 udev 9 * 4 10 11 1 The match attribute denes whether the pattern is a Unix shell-style wild card ( w ) or a Python regular expression ( re ). 2 If the given pattern matches and the corresponding package is marked as important (for example kernel packages), the snapshot will also be marked as important. 3 Pattern to match a package name. Based on the setting of the match attribute, special characters are either interpreted as shell wild cards or regular expressions. This pattern matches all package names starting with kernel- . 4 This line unconditionally matches all packages. With this conguration snapshot, pairs are made whenever a package is installed (line 9). When the kernel, dracut, glibc, systemd, or udev packages marked as important are installed, the snapshot pair will also be marked as important (lines 4 to 8). All rules are evaluated. To disable a rule, either delete it or deactivate it using XML comments. To prevent the system from making snapshot pairs for every package installation for example, comment line 9: 1 2 3 4 kernel-* 5 dracut 6 glibc 7 systemd* 8 udev 9 10 11 7.1.3.3 Creating and Mounting New Subvolumes Creating a new subvolume underneath the / hierarchy and permanently mounting it is supported. Such a subvolume will be excluded from snapshots. You need to make sure not to create it inside an existing snapshot, since you would not be able to delete snapshots anymore after a rollback. 70 Customizing the Setup SLES 12 SP4SUSE Linux Enterprise Server is congured with the /@/ subvolume which serves as an independent root for permanent subvolumes such as /opt , /srv , /home and others. Any new subvolumes you create and permanently mount need to be created in this initial root le system. To do so, run the following commands. In this example, a new subvolume /usr/important is created from /dev/sda2 . tux > sudo mount /dev/sda2 -o subvol=@ /mnt tux > sudo btrfs subvolume create /mnt/usr/important tux > sudo umount /mnt The corresponding entry in /etc/fstab needs to look like the following: /dev/sda2 /usr/important btrfs subvol=@/usr/important 0 0 Tip: Disable Copy-On-Write (cow) A subvolume may contain les that constantly change, such as virtualized disk images, database les, or log les. If so, consider disabling the copy-on-write feature for this volume, to avoid duplication of disk blocks. Use the nodatacow mount option in /etc/ fstab to do so: /dev/sda2 /usr/important btrfs nodatacow,subvol=@/usr/important 0 0 To alternatively disable copy-on-write for single les or directories, use the command chattr +C PATH . 7.1.3.4 Controlling Snapshot Archiving Snapshots occupy disk space. To prevent disks from running out of space and thus causing system outages, old snapshots are automatically deleted. By default, up to ten important installation and administration snapshots and up to ten regular installation and administration snapshots are kept. If these snapshots occupy more than 50% of the root le system size, additional snapshots will be deleted. A minimum of four important and two regular snapshots are always kept. Refer to Section 7.5.1, “Managing Existing Configurations” for instructions on how to change these values. 71 Customizing the Setup SLES 12 SP47.1.3.5 Using Snapper on Thinly-Provisioned LVM Volumes Apart from snapshots on Btrfs le systems, Snapper also supports taking snapshots on thinly- provisioned LVM volumes (snapshots on regular LVM volumes are not supported) formatted with XFS, Ext4 or Ext3. For more information and setup instructions on LVM volumes, refer to Book “Deployment Guide”, Chapter 12 “Advanced Disk Setup”, Section 12.2 “LVM Configuration”. To use Snapper on a thinly-provisioned LVM volume you need to create a Snapper conguration for it. On LVM it is required to specify the le system with --fstype=lvm(FILESYSTEM) . ext3 , etx4 or xfs are valid values for FILESYSTEM . Example: tux > sudo snapper -c lvm create-config --fstype="lvm(xfs)" /thin_lvm You can adjust this conguration according to your needs as described in Section 7.5.1, “Managing Existing Configurations”. 7.2 Using Snapper to Undo Changes Snapper on SUSE Linux Enterprise Server is precongured to serve as a tool that lets you undo changes made by zypper and YaST. For this purpose, Snapper is congured to create a pair of snapshots before and after each run of zypper and YaST. Snapper also lets you restore system les that have been accidentally deleted or modied. Timeline snapshots for the root partition need to be enabled for this purpose—see Section 7.1.3.1, “Disabling/Enabling Snapshots” for details. By default, automatic snapshots as described above are congured for the root partition and its subvolumes. To make snapshots available for other partitions such as /home for example, you can create custom congurations. Important: Undoing Changes Compared to Rollback When working with snapshots to restore data, it is important to know that there are two fundamentally dierent scenarios Snapper can handle: Undoing Changes When undoing changes as described in the following, two snapshots are being compared and the changes between these two snapshots are made undone. Using this method also allows to explicitly select the les that should be restored. Rollback 72 Using Snapper to Undo Changes SLES 12 SP4When doing rollbacks as described in Section 7.3, “System Rollback by Booting from Snapshots”, the system is reset to the state at which the snapshot was taken. When undoing changes, it is also possible to compare a snapshot against the current system. When restoring all les from such a comparison, this will have the same result as doing a rollback. However, using the method described in Section 7.3, “System Rollback by Booting from Snapshots” for rollbacks should be preferred, since it is faster and allows you to review the system before doing the rollback. Warning: Data Consistency There is no mechanism to ensure data consistency when creating a snapshot. Whenever a le (for example, a database) is written at the same time as the snapshot is being created, it will result in a corrupted or partly written le. Restoring such a le will cause problems. Furthermore, some system les such as /etc/mtab must never be restored. Therefore it is strongly recommended to always closely review the list of changed les and their dis. Only restore les that really belong to the action you want to revert. 7.2.1 Undoing YaST and Zypper Changes If you set up the root partition with Btrfs during the installation, Snapper—precongured for doing rollbacks of YaST or Zypper changes—will automatically be installed. Every time you start a YaST module or a Zypper transaction, two snapshots are created: a “pre-snapshot” capturing the state of the le system before the start of the module and a “post-snapshot” after the module has been nished. Using the YaST Snapper module or the snapper command line tool, you can undo the changes made by YaST/Zypper by restoring les from the “pre-snapshot”. Comparing two snapshots the tools also allow you to see which les have been changed. You can also display the dierences between two versions of a le (di). PROCEDURE 7.1: UNDOING CHANGES USING THE YAST SNAPPER MODULE 1. Start the Snapper module from the Miscellaneous section in YaST or by entering yast2 snapper . 2. Make sure Current Conguration is set to root. This is always the case unless you have manually added own Snapper congurations. 73 Undoing YaST and Zypper Changes SLES 12 SP43. Choose a pair of pre- and post-snapshots from the list. Both, YaST and Zypper snapshot pairs are of the type Pre & Post. YaST snapshots are labeled as zypp(y2base) in the Description column; Zypper snapshots are labeled zypp(zypper) . 4. Click Show Changes to open the list of les that dier between the two snapshots. 74 Undoing YaST and Zypper Changes SLES 12 SP45. Review the list of les. To display a “di” between the pre- and post-version of a le, select it from the list. 6. To restore one or more les, select the relevant les or directories by activating the respective check box. Click Restore Selected and conrm the action by clicking Yes. To restore a single le, activate its di view by clicking its name. Click Restore From First and conrm your choice with Yes. 75 Undoing YaST and Zypper Changes SLES 12 SP4PROCEDURE 7.2: UNDOING CHANGES USING THE snapper COMMAND 1. Get a list of YaST and Zypper snapshots by running snapper list -t pre-post . YaST snapshots are labeled as yast MODULE_NAME in the Description column; Zypper snapshots are labeled zypp(zypper) . tux > sudo snapper list -t pre-post Pre # | Post # | Pre Date | Post Date | Description ------+--------+-------------------------------+-------------------------------+-------------- 311 | 312 | Tue 06 May 2014 14:05:46 CEST | Tue 06 May 2014 14:05:52 CEST | zypp(y2base) 340 | 341 | Wed 07 May 2014 16:15:10 CEST | Wed 07 May 2014 16:15:16 CEST | zypp(zypper) 342 | 343 | Wed 07 May 2014 16:20:38 CEST | Wed 07 May 2014 16:20:42 CEST | zypp(y2base) 344 | 345 | Wed 07 May 2014 16:21:23 CEST | Wed 07 May 2014 16:21:24 CEST | zypp(zypper) 346 | 347 | Wed 07 May 2014 16:41:06 CEST | Wed 07 May 2014 16:41:10 CEST | zypp(y2base) 348 | 349 | Wed 07 May 2014 16:44:50 CEST | Wed 07 May 2014 16:44:53 CEST | zypp(y2base) 350 | 351 | Wed 07 May 2014 16:46:27 CEST | Wed 07 May 2014 16:46:38 CEST | zypp(y2base) 2. Get a list of changed les for a snapshot pair with snapper status PRE .. POST . Files with content changes are marked with c, les that have been added are marked with + and deleted les are marked with -. tux > sudo snapper status 350..351 +..... /usr/share/doc/packages/mikachan-fonts +..... /usr/share/doc/packages/mikachan-fonts/COPYING +..... /usr/share/doc/packages/mikachan-fonts/dl.html c..... /usr/share/fonts/truetype/fonts.dir c..... /usr/share/fonts/truetype/fonts.scale +..... /usr/share/fonts/truetype/#####-p.ttf +..... /usr/share/fonts/truetype/#####-pb.ttf +..... /usr/share/fonts/truetype/#####-ps.ttf +..... /usr/share/fonts/truetype/#####.ttf c..... /var/cache/fontconfig/7ef2298fde41cc6eeb7af42e48b7d293-x86_64.cache-4 c..... /var/lib/rpm/Basenames c..... /var/lib/rpm/Dirnames c..... /var/lib/rpm/Group c..... /var/lib/rpm/Installtid c..... /var/lib/rpm/Name c..... /var/lib/rpm/Packages c..... /var/lib/rpm/Providename c..... /var/lib/rpm/Requirename c..... /var/lib/rpm/Sha1header c..... /var/lib/rpm/Sigmd5 3. To display the di for a certain le, run snapper diff PRE .. POST FILENAME . If you do not specify FILENAME , a di for all les will be displayed. tux > sudo snapper diff 350..351 /usr/share/fonts/truetype/fonts.scale 76 Undoing YaST and Zypper Changes SLES 12 SP4--- /.snapshots/350/snapshot/usr/share/fonts/truetype/fonts.scale 2014-04-23 15:58:57.000000000 +0200 +++ /.snapshots/351/snapshot/usr/share/fonts/truetype/fonts.scale 2014-05-07 16:46:31.000000000 +0200 @@ -1,4 +1,4 @@ -1174 +1486 ds=y:ai=0.2:luximr.ttf -b&h-luxi mono-bold-i-normal--0-0-0-0-c-0-iso10646-1 ds=y:ai=0.2:luximr.ttf -b&h-luxi mono-bold-i-normal--0-0-0-0-c-0-iso8859-1 [...] 4. To restore one or more les run snapper -v undochange PRE .. POST FILENAMES . If you do not specify a FILENAMES , all changed les will be restored. tux > sudo snapper -v undochange 350..351 create:0 modify:13 delete:7 undoing change... deleting /usr/share/doc/packages/mikachan-fonts deleting /usr/share/doc/packages/mikachan-fonts/COPYING deleting /usr/share/doc/packages/mikachan-fonts/dl.html deleting /usr/share/fonts/truetype/#####-p.ttf deleting /usr/share/fonts/truetype/#####-pb.ttf deleting /usr/share/fonts/truetype/#####-ps.ttf deleting /usr/share/fonts/truetype/#####.ttf modifying /usr/share/fonts/truetype/fonts.dir modifying /usr/share/fonts/truetype/fonts.scale modifying /var/cache/fontconfig/7ef2298fde41cc6eeb7af42e48b7d293-x86_64.cache-4 modifying /var/lib/rpm/Basenames modifying /var/lib/rpm/Dirnames modifying /var/lib/rpm/Group modifying /var/lib/rpm/Installtid modifying /var/lib/rpm/Name modifying /var/lib/rpm/Packages modifying /var/lib/rpm/Providename modifying /var/lib/rpm/Requirename modifying /var/lib/rpm/Sha1header modifying /var/lib/rpm/Sigmd5 undoing change done 77 Undoing YaST and Zypper Changes SLES 12 SP4Warning: Reverting User Additions Reverting user additions via undoing changes with Snapper is not recommended. Since certain directories are excluded from snapshots, les belonging to these users will remain in the le system. If a user with the same user ID as a deleted user is created, this user will inherit the les. Therefore it is strongly recommended to use the YaST User and Group Management tool to remove users. 7.2.2 Using Snapper to Restore Files Apart from the installation and administration snapshots, Snapper creates timeline snapshots. You can use these backup snapshots to restore les that have accidentally been deleted or to restore a previous version of a le. By using Snapper''s di feature you can also nd out which modications have been made at a certain point of time. Being able to restore les is especially interesting for data, which may reside on subvolumes or partitions for which snapshots are not taken by default. To be able to restore les from home directories, for example, create a separate Snapper conguration for /home doing automatic timeline snapshots. See Section 7.5, “Creating and Modifying Snapper Configurations” for instructions. Warning: Restoring Files Compared to Rollback Snapshots taken from the root le system (dened by Snapper''s root conguration), can be used to do a system rollback. The recommended way to do such a rollback is to boot from the snapshot and then perform the rollback. See Section 7.3, “System Rollback by Booting from Snapshots” for details. Performing a rollback would also be possible by restoring all les from a root le system snapshot as described below. However, this is not recommended. You may restore single les, for example a conguration le from the /etc directory, but not the complete list of les from the snapshot. This restriction only aects snapshots taken from the root le system! PROCEDURE 7.3: RESTORING FILES USING THE YAST SNAPPER MODULE 1. Start the Snapper module from the Miscellaneous section in YaST or by entering yast2 snapper . 2. Choose the Current Conguration from which to choose a snapshot. 78 Using Snapper to Restore Files SLES 12 SP43. Select a timeline snapshot from which to restore a le and choose Show Changes. Timeline snapshots are of the type Single with a description value of timeline. 4. Select a le from the text box by clicking the le name. The dierence between the snapshot version and the current system is shown. Activate the check box to select the le for restore. Do so for all les you want to restore. 5. Click Restore Selected and conrm the action by clicking Yes. PROCEDURE 7.4: RESTORING FILES USING THE snapper COMMAND 1. Get a list of timeline snapshots for a specic conguration by running the following command: tux > sudo snapper -c CONFIG list -t single | grep timeline CONFIG needs to be replaced by an existing Snapper conguration. Use snapper list- configs to display a list. 2. Get a list of changed les for a given snapshot by running the following command: tux > sudo snapper -c CONFIG status SNAPSHOT_ID..0 Replace SNAPSHOT_ID by the ID for the snapshot from which you want to restore the le(s). 3. Optionally list the dierences between the current le version and the one from the snapshot by running tux > sudo snapper -c CONFIG diff SNAPSHOT_ID..0 FILE NAME If you do not specify , the dierence for all les are shown. 4. To restore one or more les, run tux > sudo snapper -c CONFIG -v undochange SNAPSHOT_ID..0 FILENAME1 FILENAME2 If you do not specify le names, all changed les will be restored. 79 Using Snapper to Restore Files SLES 12 SP47.3 System Rollback by Booting from Snapshots The GRUB 2 version included on SUSE Linux Enterprise Server can boot from Btrfs snapshots. Together with Snapper''s rollback feature, this allows to recover a miscongured system. Only snapshots created for the default Snapper conguration ( root ) are bootable. Important: Supported Configuration As of SUSE Linux Enterprise Server 12 SP4 system rollbacks are only supported if the default subvolume conguration of the root partition has not been changed. When booting a snapshot, the parts of the le system included in the snapshot are mounted read-only; all other le systems and parts that are excluded from snapshots are mounted read- write and can be modied. Important: Undoing Changes Compared to Rollback When working with snapshots to restore data, it is important to know that there are two fundamentally dierent scenarios Snapper can handle: Undoing Changes When undoing changes as described in Section 7.2, “Using Snapper to Undo Changes”, two snapshots are compared and the changes between these two snapshots are reverted. Using this method also allows to explicitly exclude selected les from being restored. Rollback When doing rollbacks as described in the following, the system is reset to the state at which the snapshot was taken. To do a rollback from a bootable snapshot, the following requirements must be met. When doing a default installation, the system is set up accordingly. REQUIREMENTS FOR A ROLLBACK FROM A BOOTABLE SNAPSHOT The root le system needs to be Btrfs. Booting from LVM volume snapshots is not supported. 80 System Rollback by Booting from Snapshots SLES 12 SP4The root le system needs to be on a single device, a single partition and a single subvolume. Directories that are excluded from snapshots such as /srv (see Section 7.1.2, “Directories That Are Excluded from Snapshots” for a full list) may reside on separate partitions. The system needs to be bootable via the installed boot loader. To perform a rollback from a bootable snapshot, do as follows: 1. Boot the system. In the boot menu choose Bootable snapshots and select the snapshot you want to boot. The list of snapshots is listed by date—the most recent snapshot is listed rst. 2. Log in to the system. Carefully check whether everything works as expected. Note that you cannot write to any directory that is part of the snapshot. Data you write to other directories will not get lost, regardless of what you do next. 3. Depending on whether you want to perform the rollback or not, choose your next step: a. If the system is in a state where you do not want to do a rollback, reboot to boot into the current system state. You can then choose a dierent snapshot, or start the rescue system. b. To perform the rollback, run tux > sudo snapper rollback and reboot afterward. On the boot screen, choose the default boot entry to reboot into the reinstated system. A snapshot of the le system status before the rollback is created. The default subvolume for root will be replaced with a fresh read-write snapshot. For details, see Section 7.3.1, “Snapshots after Rollback”. It is useful to add a description for the snapshot with the -d option. For example: New file system root since rollback on DATE TIME Tip: Rolling Back to a Specific Installation State If snapshots are not disabled during installation, an initial bootable snapshot is created at the end of the initial system installation. You can go back to that state at any time by booting this snapshot. The snapshot can be identied by the description after installation . A bootable snapshot is also created when starting a system upgrade to a service pack or a new major release (provided snapshots are not disabled). 81 System Rollback by Booting from Snapshots SLES 12 SP47.3.1 Snapshots after Rollback Before a rollback is performed, a snapshot of the running le system is created. The description references the ID of the snapshot that was restored in the rollback. Snapshots created by rollbacks receive the value number for the Cleanup attribute. The rollback snapshots are therefore automatically deleted when the set number of snapshots is reached. Refer to Section 7.7, “Automatic Snapshot Clean-Up” for details. If the snapshot contains important data, extract the data from the snapshot before it is removed. 7.3.1.1 Example of Rollback Snapshot For example, after a fresh installation the following snapshots are available on the system: root # snapper --iso list Type | # | | Cleanup | Description | Userdata -------+---+ ... +---------+-----------------------+-------------- single | 0 | | | current | single | 1 | | | first root filesystem | single | 2 | | number | after installation | important=yes After running sudo snapper rollback snapshot 3 is created and contains the state of the system before the rollback was executed. Snapshot 4 is the new default Btrfs subvolume and thus the system after a reboot. root # snapper --iso list Type | # | | Cleanup | Description | Userdata -------+---+ ... +---------+-----------------------+-------------- single | 0 | | | current | single | 1 | | number | first root filesystem | single | 2 | | number | after installation | important=yes single | 3 | | number | rollback backup of #1 | important=yes single | 4 | | | | 7.3.2 Accessing and Identifying Snapshot Boot Entries To boot from a snapshot, reboot your machine and choose Start Bootloader from a read-only snapshot. A screen listing all bootable snapshots opens. The most recent snapshot is listed rst, the oldest last. Use the keys ↓ and ↑ to navigate and press Enter to activate the selected snapshot. Activating a snapshot from the boot menu does not reboot the machine immediately, but rather opens the boot loader of the selected snapshot. 82 Snapshots after Rollback SLES 12 SP4FIGURE 7.1: BOOT LOADER: SNAPSHOTS Each snapshot entry in the boot loader follows a naming scheme which makes it possible to identify it easily: [*] 1 OS 2 (KERNEL 3 ,DATE 4 TTIME 5 ,DESCRIPTION 6 ) 1 If the snapshot was marked important , the entry is marked with a * . 2 Operating system label. 4 Date in the format YYYY-MM-DD . 5 Time in the format HH:MM . 6 This eld contains a description of the snapshot. In case of a manually created snapshot this is the string created with the option --description or a custom string (see Tip: Setting a Custom Description for Boot Loader Snapshot Entries). In case of an automatically created snapshot, it is the tool that was called, for example zypp(zypper) or yast_sw_single . Long descriptions may be truncated, depending on the size of the boot screen. 83 Accessing and Identifying Snapshot Boot Entries SLES 12 SP4Tip: Setting a Custom Description for Boot Loader Snapshot Entries It is possible to replace the default string in the description eld of a snapshot with a custom string. This is for example useful if an automatically created description is not sucient, or a user-provided description is too long. To set a custom string STRING for snapshot NUMBER , use the following command: tux > sudo snapper modify --userdata "bootloader=STRING" NUMBER The description should be no longer than 25 characters—everything that exceeds this size will not be readable on the boot screen. 7.3.3 Limitations A complete system rollback, restoring the complete system to the identical state as it was in when a snapshot was taken, is not possible. 7.3.3.1 Directories Excluded from Snapshots Root le system snapshots do not contain all directories. See Section 7.1.2, “Directories That Are Excluded from Snapshots” for details and reasons. As a general consequence, data from these directories is not restored, resulting in the following limitations. Add-ons and Third Party Software may be Unusable after a Rollback Applications and add-ons installing data in subvolumes excluded from the snapshot, such as /opt , may not work after a rollback, if others parts of the application data are also installed on subvolumes included in the snapshot. Re-install the application or the add- on to solve this problem. File Access Problems If an application had changed le permissions and/or ownership in between snapshot and current system, the application may not be able to access these les. Reset permissions and/or ownership for the aected les after the rollback. Incompatible Data Formats 84 Limitations SLES 12 SP4If a service or an application has established a new data format in between snapshot and current system, the application may not be able to read the aected data les after a rollback. Subvolumes with a Mixture of Code and Data Subvolumes like /srv may contain a mixture of code and data. A rollback may result in non-functional code. A downgrade of the PHP version, for example, may result in broken PHP scripts for the Web server. User Data If a rollback removes users from the system, data that is owned by these users in directories excluded from the snapshot, is not removed. If a user with the same user ID is created, this user will inherit the les. Use a tool like find to locate and remove orphaned les. 7.3.3.2 No Rollback of Boot Loader Data A rollback of the boot loader is not possible, since all “stages” of the boot loader must t together. This cannot be guaranteed when doing rollbacks of /boot . 7.4 Enabling Snapper in User Home Directories You may enable snapshots for users'' /home directories, which supports a number of use cases: Individual users may manage their own snapshots and rollbacks. System users, for example database, system, and network admins who want to track copies of conguration les, documentation, and so on. Samba shares with home directories and Btrfs backend. Each user''s directory is a Btrfs subvolume of /home . It is possible to set this up manually (see Section 7.4.3, “Manually Enabling Snapshots in Home Directories”). However, a more convenient way is to use pam_snapper . The pam_snapper package installs the pam_snapper.so module and helper scripts, which automate user creation and Snapper conguration. pam_snapper provides integration with the useradd command, pluggable authentication modules (PAM), and Snapper. By default it creates snapshots at user login and logout, and also creates time-based snapshots as some users remain logged in for extended periods of time. You may change the defaults using the normal Snapper commands and conguration les. 85 Enabling Snapper in User Home Directories SLES 12 SP47.4.1 Installing pam_snapper and Creating Users The easiest way is to start with a new /home directory formatted with Btrfs, and no existing users. Install pam_snapper : root # zypper in pam_snapper Add this line to /etc/pam.d/common-session : session optional pam_snapper.so Use the /usr/lib/pam_snapper/pam_snapper_useradd.sh script to create a new user and home directory. By default the script performs a dry run. Edit the script to change DRYRUN=1 to DRYRUN=0 . Now you can create a new user: root # /usr/lib/pam_snapper/pam_snapper_useradd.sh \ username group passwd=password Create subvolume ''/home/username'' useradd: warning: the home directory already exists. Not copying any file from skel directory into it. The les from /etc/skel will be copied into the user''s home directory at their rst login. Verify that the user''s conguration was created by listing your Snapper congurations: root # snapper list --all Config: home_username, subvolume: /home/username Type | # | Pre # | Date | User | Cleanup | Description | Userdata -------+---+-------+------+------+---------+-------------+--------- single | 0 | | | root | | current | Over time, this output will become populated with a list of snapshots, which the user can manage with the standard Snapper commands. 7.4.2 Removing Users Remove users with the /usr/lib/pam_snapper/pam_snapper_userdel.sh script. By default it performs a dry run, so edit it to change DRYRUN=1 to DRYRUN=0 . This removes the user, the user''s home subvolume, Snapper conguration, and deletes all snapshots. root # /usr/lib/pam_snapper/pam_snapper_userdel.sh username 86 Installing pam_snapper and Creating Users SLES 12 SP47.4.3 Manually Enabling Snapshots in Home Directories These are the steps for manually setting up users'' home directories with Snapper. /home must be formatted with Btrfs, and the users not yet created. root # btrfs subvol create /home/username root # snapper -c home_username create-config /home/username root # sed -i -e "s/ALLOW_USERS=\"\"/ALLOW_USERS=\"username\"/g" \ /etc/snapper/configs/home_username root # yast users add username=username home=/home/username password=password root # chown username.group /home/username root # chmod 755 /home/username/.snapshots 7.5 Creating and Modifying Snapper Configurations The way Snapper behaves is dened in a conguration le that is specic for each partition or Btrfs subvolume. These conguration les reside under /etc/snapper/configs/ . In case the root le system is big enough (approximately 12 GB), snapshots are automatically enabled for the root le system / upon installation. The corresponding default conguration is named root . It creates and manages the YaST and Zypper snapshot. See Section  7.5.1.1, “Configuration Data” for a list of the default values. Note: Minimum Root File System Size for Enabling Snapshots As explained in Section 7.1, “Default Setup”, enabling snapshots requires additional free space in the root le system. The amount depends on the amount of packages installed and the amount of changes made to the volume that is included in snapshots. The snapshot frequency and the number of snapshots that get archived also matter. There is a minimum root le system size that is required in order to automatically enable snapshots during the installation. This size is approximately 12 GB. This value may change in the future, depending on architecture and the size of the base system. It depends on the values for the following tags in the le /control.xml from the installation media: It is calculated with the following formula: ROOT_BASE_SIZE * (1 + BTRFS_INCREASE_PERCENTAGE /100) 87 Manually Enabling Snapshots in Home Directories SLES 12 SP4Keep in mind that this value is a minimum size. Consider using more space for the root le system. As a rule of thumb, double the size you would use when not having enabled snapshots. You may create your own congurations for other partitions formatted with Btrfs or existing subvolumes on a Btrfs partition. In the following example we will set up a Snapper conguration for backing up the Web server data residing on a separate, Btrfs -formatted partition mounted at /srv/www . After a conguration has been created, you can either use snapper itself or the YaST Snapper module to restore les from these snapshots. In YaST you need to select your Current Conguration, while you need to specify your conguration for snapper with the global switch -c (for example, snapper -c myconfig list ). To create a new Snapper conguration, run snapper create-config : tux > sudo snapper -c www-data 1 create-config /srv/www 2 1 Name of conguration le. 2 Mount point of the partition or Btrfs subvolume on which to take snapshots. This command will create a new conguration le /etc/snapper/configs/www-data with reasonable default values (taken from /etc/snapper/config-templates/default ). Refer to Section 7.5.1, “Managing Existing Configurations” for instructions on how to adjust these defaults. Tip: Configuration Defaults Default values for a new conguration are taken from /etc/snapper/config- templates/default . To use your own set of defaults, create a copy of this le in the same directory and adjust it to your needs. To use it, specify the -t option with the create-cong command: tux > sudo snapper -c www-data create-config -t MY_DEFAULTS /srv/www 88 Creating and Modifying Snapper Configurations SLES 12 SP47.5.1 Managing Existing Configurations The snapper command oers several subcommands for managing existing congurations. You can list, show, delete and modify them: Listing Configurations Use the subcommand snapper list-configs to get all existing congurations: tux > sudo snapper list-configs Config | Subvolume -------+---------- root | / usr | /usr local | /local Showing a Configuration Use the subcommand snapper -c CONFIG get-config to display the specied conguration. Replace CONFIG with one of the conguration names shown by snapper list-configs . For more information about the conguration options, see Section 7.5.1.1, “Configuration Data”. To display the default conguration, run: tux > sudo snapper -c root get-config Modifying a Configuration Use the subcommand snapper -c CONFIG set-config OPTION=VALUE to modify an option in the specied conguration. Replace CONFIG with one of the conguration names shown by snapper list-configs . Possible values for OPTION and VALUE are listed in Section 7.5.1.1, “Configuration Data”. Deleting a Configuration Use the subcommand snapper -c CONFIG delete-config to delete a conguration. Replace CONFIG with one of the conguration names shown by snapper list-configs . 7.5.1.1 Configuration Data Each conguration contains a list of options that can be modied from the command line. The following list provides details for each option. To change a value, run snapper -c CONFIG set-config "KEY=VALUE" . ALLOW_GROUPS , ALLOW_USERS 89 Managing Existing Configurations SLES 12 SP4Granting permissions to use snapshots to regular users. See Section 7.5.1.2, “Using Snapper as Regular User” for more information. The default value is "" . BACKGROUND_COMPARISON Denes whether pre and post snapshots should be compared in the background after creation. The default value is "yes" . EMPTY_* Denes the clean-up algorithm for snapshots pairs with identical pre and post snapshots. See Section 7.7.3, “Cleaning Up Snapshot Pairs That Do Not Differ” for details. FSTYPE File system type of the partition. Do not change. The default value is "btrfs" . NUMBER_* Denes the clean-up algorithm for installation and admin snapshots. See Section  7.7.1, “Cleaning Up Numbered Snapshots” for details. QGROUP / SPACE_LIMIT Adds quota support to the clean-up algorithms. See Section 7.7.5, “Adding Disk Quota Support” for details. SUBVOLUME Mount point of the partition or subvolume to snapshot. Do not change. The default value is "/" . SYNC_ACL If Snapper is used by regular users (see Section 7.5.1.2, “Using Snapper as Regular User”), the users must be able to access the .snapshot directories and to read les within them. If SYNC_ACL is set to yes , Snapper automatically makes them accessible using ACLs for users and groups from the ALLOW_USERS or ALLOW_GROUPS entries. The default value is "no" . TIMELINE_CREATE If set to yes , hourly snapshots are created. Valid values: yes , no . The default value is "no" . TIMELINE_CLEANUP / TIMELINE_LIMIT_* 90 Managing Existing Configurations SLES 12 SP4Denes the clean-up algorithm for timeline snapshots. See Section 7.7.2, “Cleaning Up Timeline Snapshots” for details. 7.5.1.2 Using Snapper as Regular User By default Snapper can only be used by root . However, there are cases in which certain groups or users need to be able to create snapshots or undo changes by reverting to a snapshot: Web site administrators who want to take snapshots of /srv/www Users who want to take a snapshot of their home directory For these purposes, you can create Snapper congurations that grant permissions to users or/ and groups. The corresponding .snapshots directory needs to be readable and accessible by the specied users. The easiest way to achieve this is to set the SYNC_ACL option to yes . PROCEDURE 7.5: ENABLING REGULAR USERS TO USE SNAPPER Note that all steps in this procedure need to be run by root . 1. If a Snapper conguration does not exist yet, create one for the partition or subvolume on which the user should be able to use Snapper. Refer to Section 7.5, “Creating and Modifying Snapper Configurations” for instructions. Example: tux > sudo snapper --config web_data create /srv/www 2. The conguration le is created under /etc/snapper/configs/CONFIG , where CONFIG is the value you specied with -c/--config in the previous step (for example /etc/ snapper/configs/web_data ). Adjust it according to your needs. For more information, see Section 7.5.1, “Managing Existing Configurations”. 3. Set values for ALLOW_USERS and/or ALLOW_GROUPS to grant permissions to users and/or groups, respectively. Multiple entries need to be separated by Space . To grant permissions to the user www_admin for example, run: tux > sudo snapper -c web_data set-config "ALLOW_USERS=www_admin" SYNC_ACL="yes" 4. The given Snapper conguration can now be used by the specied user(s) and/or group(s). You can test it with the list command, for example: www_admin:~ > snapper -c web_data list 91 Managing Existing Configurations SLES 12 SP47.6 Manually Creating and Managing Snapshots Snapper is not restricted to creating and managing snapshots automatically by conguration; you can also create snapshot pairs (“before and after”) or single snapshots manually using either the command-line tool or the YaST module. All Snapper operations are carried out for an existing conguration (see Section 7.5, “Creating and Modifying Snapper Configurations” for details). You can only take snapshots of partitions or volumes for which a conguration exists. By default the system conguration ( root ) is used. If you want to create or manage snapshots for your own conguration you need to explicitly choose it. Use the Current Conguration drop-down box in YaST or specify the -c on the command line ( snapper -c MYCONFIG COMMAND ). 7.6.1 Snapshot Metadata Each snapshot consists of the snapshot itself and some metadata. When creating a snapshot you also need to specify the metadata. Modifying a snapshot means changing its metadata—you cannot modify its content. Use snapper list to show existing snapshots and their metadata: snapper --config home list Lists snapshots for the conguration home . To list snapshots for the default conguration (root), use snapper -c root list or snapper list . snapper list -a Lists snapshots for all existing congurations. snapper list -t pre-post Lists all pre and post snapshot pairs for the default ( root ) conguration. snapper list -t single Lists all snapshots of the type single for the default ( root ) conguration. The following metadata is available for each snapshot: Type: Snapshot type, see Section 7.6.1.1, “Snapshot Types” for details. This data cannot be changed. Number: Unique number of the snapshot. This data cannot be changed. Pre Number: Species the number of the corresponding pre snapshot. For snapshots of type post only. This data cannot be changed. 92 Manually Creating and Managing Snapshots SLES 12 SP4Description: A description of the snapshot. Userdata: An extended description where you can specify custom data in the form of a comma-separated key=value list: reason=testing, project=foo . This eld is also used to mark a snapshot as important ( important=yes ) and to list the user that created the snapshot (user=tux). Cleanup-Algorithm: Cleanup-algorithm for the snapshot, see Section  7.7, “Automatic Snapshot Clean-Up” for details. 7.6.1.1 Snapshot Types Snapper knows three dierent types of snapshots: pre, post, and single. Physically they do not dier, but Snapper handles them dierently. pre Snapshot of a le system before a modication. Each pre snapshot corresponds to a post snapshot. For example, this is used for the automatic YaST/Zypper snapshots. post Snapshot of a le system after a modication. Each post snapshot corresponds to a pre snapshot. For example, this is used for the automatic YaST/Zypper snapshots. single Stand-alone snapshot. For example, this is used for the automatic hourly snapshots. This is the default type when creating snapshots. 7.6.1.2 Cleanup Algorithms Snapper provides three algorithms to clean up old snapshots. The algorithms are executed in a daily cron job. It is possible to dene the number of dierent types of snapshots to keep in the Snapper conguration (see Section 7.5.1, “Managing Existing Configurations” for details). number Deletes old snapshots when a certain snapshot count is reached. timeline Deletes old snapshots having passed a certain age, but keeps several hourly, daily, monthly, and yearly snapshots. 93 Snapshot Metadata SLES 12 SP4empty-pre-post Deletes pre/post snapshot pairs with empty dis. 7.6.2 Creating Snapshots To create a snapshot, run snapper create or click Create in the YaST module Snapper. The following examples explain how to create snapshots from the command line. The YaST interface for Snapper is not explicitly described here but provides equivalent functionality. Tip: Snapshot Description Always specify a meaningful description to later be able to identify its purpose. You can also specify additional information via the option --userdata . snapper create --description "Snapshot for week 2 2014" Creates a stand-alone snapshot (type single) for the default ( root ) conguration with a description. Because no cleanup-algorithm is specied, the snapshot will never be deleted automatically. snapper --config home create --description "Cleanup in ~tux" Creates a stand-alone snapshot (type single) for a custom conguration named home with a description. Because no cleanup-algorithm is specied, the snapshot will never be deleted automatically. snapper --config home create --description "Daily data backup" --cleanup- algorithm timeline > Creates a stand-alone snapshot (type single) for a custom conguration named home with a description. The snapshot will automatically be deleted when it meets the criteria specied for the timeline cleanup-algorithm in the conguration. snapper create --type pre --print-number --description "Before the Apache config cleanup" --userdata "important=yes" Creates a snapshot of the type pre and prints the snapshot number. First command needed to create a pair of snapshots used to save a “before” and “after” state. The snapshot is marked as important. snapper create --type post --pre-number 30 --description "After the Apache config cleanup" --userdata "important=yes" 94 Creating Snapshots SLES 12 SP4Creates a snapshot of the type post paired with the pre snapshot number 30 . Second command needed to create a pair of snapshots used to save a “before” and “after” state. The snapshot is marked as important. snapper create --command COMMAND --description "Before and after COMMAND" Automatically creates a snapshot pair before and after running COMMAND . This option is only available when using snapper on the command line. 7.6.3 Modifying Snapshot Metadata Snapper allows you to modify the description, the cleanup algorithm, and the user data of a snapshot. All other metadata cannot be changed. The following examples explain how to modify snapshots from the command line. It should be easy to adopt them when using the YaST interface. To modify a snapshot on the command line, you need to know its number. Use snapper list to display all snapshots and their numbers. The YaST Snapper module already lists all snapshots. Choose one from the list and click Modify. snapper modify --cleanup-algorithm "timeline" 10 Modies the metadata of snapshot 10 for the default ( root ) conguration. The cleanup algorithm is set to timeline . snapper --config home modify --description "daily backup" -cleanup-algorithm "timeline" 120 Modies the metadata of snapshot 120 for a custom conguration named home . A new description is set and the cleanup algorithm is unset. 7.6.4 Deleting Snapshots To delete a snapshot with the YaST Snapper module, choose a snapshot from the list and click Delete. To delete a snapshot with the command-line tool, you need to know its number. Get it by running snapper list . To delete a snapshot, run snapper delete NUMBER . Deleting the current default subvolume snapshot is not allowed. 95 Modifying Snapshot Metadata SLES 12 SP4When deleting snapshots with Snapper, the freed space will be claimed by a Btrfs process running in the background. Thus the visibility and the availability of free space is delayed. In case you need space freed by deleting a snapshot to be available immediately, use the option --sync with the delete command. Tip: Deleting Snapshot Pairs When deleting a pre snapshot, you should always delete its corresponding post snapshot (and vice versa). snapper delete 65 Deletes snapshot 65 for the default ( root ) conguration. snapper -c home delete 89 90 Deletes snapshots 89 and 90 for a custom conguration named home . snapper delete --sync 23 Deletes snapshot 23 for the default ( root ) conguration and makes the freed space available immediately. Tip: Delete Unreferenced Snapshots Sometimes the Btrfs snapshot is present but the XML le containing the metadata for Snapper is missing. In this case the snapshot is not visible for Snapper and needs to be deleted manually: btrfs subvolume delete /.snapshots/SNAPSHOTNUMBER/snapshot rm -rf /.snapshots/SNAPSHOTNUMBER Tip: Old Snapshots Occupy More Disk Space If you delete snapshots to free space on your hard disk, make sure to delete old snapshots rst. The older a snapshot is, the more disk space it occupies. Snapshots are also automatically deleted by a daily cron job. Refer to Section 7.6.1.2, “Cleanup Algorithms” for details. 96 Deleting Snapshots SLES 12 SP47.7 Automatic Snapshot Clean-Up Over time snapshots grow in size, occupying an ever increasing amount disk space. To prevent disks from running out of space, Snapper oers algorithms to automatically delete old snapshots. These algorithms dierentiate between timeline snapshots and numbered snapshots (administration plus installation snapshot pairs). You can specify the number of snapshots to keep for each type. In addition to that, you can optionally specify a disk space quota, dening the maximum amount of disk space the snapshots may occupy. It is also possible to automatically delete pre and post snapshots pairs that do not dier. A clean-up algorithm is always bound to a single Snapper conguration, so you need to congure algorithms for each conguration. To prevent certain snapshots from being automatically deleted, refer to Q:. The default setup ( root ) is congured to do clean-up for numbered snapshots and empty pre and post snapshot pairs. In the default setup, the quota support is enabled, and snapshots must leave at least 20% of the available disk space on the root partition free. Timeline snapshots are disabled by default, therefore the timeline clean-up algorithm is also disabled. Note: Improved Clean-Up Algorithm Previous implementations of the clean-up algorithm only ensured that snapshots do not use more that the specied amount of disk space (default is 50%). In certain cases, this didn''t prevent the system running of disk space. Starting with SUSE Linux Enterprise Server 12 SP1, Snapper features an improved clean-up algorithm that keeps 20% of the available disk space free at all times. 7.7.1 Cleaning Up Numbered Snapshots Cleaning up numbered snapshots—administration plus installation snapshot pairs—is controlled by the following parameters of a Snapper conguration. NUMBER_CLEANUP Enables or disables clean-up of installation and admin snapshot pairs. If enabled, snapshot pairs are deleted when the total snapshot count exceeds a number specied with NUMBER_LIMIT and/or NUMBER_LIMIT_IMPORTANT and an age specied with NUMBER_MIN_AGE . Valid values: yes (enable), no (disable). 97 Automatic Snapshot Clean-Up SLES 12 SP4The default value is "yes" . Example command to change or set: tux > sudo snapper -c CONFIG set-config "NUMBER_CLEANUP=no" NUMBER_LIMIT / NUMBER_LIMIT_IMPORTANT Denes how many regular and/or important installation and administration snapshot pairs to keep. Only the youngest snapshots will be kept. Ignored if NUMBER_CLEANUP is set to "no" . The default value is "2-10" for NUMBER_LIMIT and "4-10" for NUMBER_LIMIT_IMPORTANT . Example command to change or set: tux > sudo snapper -c CONFIG set-config "NUMBER_LIMIT=10" Important: Ranged Compared to Constant Values In case quota support is enabled (see Section 7.7.5, “Adding Disk Quota Support”) the limit needs to be specied as a minimum-maximum range, for example 2-10 . If quota support is disabled, a constant value, for example 10 , needs to be provided, otherwise cleaning-up will fail with an error. NUMBER_MIN_AGE Denes the minimum age in seconds a snapshot must have before it can automatically be deleted. Snapshots younger than the value specied here will not be deleted, regardless of how many exist. The default value is "1800" . Example command to change or set: tux > sudo snapper -c CONFIG set-config "NUMBER_MIN_AGE=864000" Note: Limit and Age NUMBER_LIMIT , NUMBER_LIMIT_IMPORTANT and NUMBER_MIN_AGE are always evaluated. Snapshots are only deleted when all conditions are met. If you always want to keep the number of snapshots dened with NUMBER_LIMIT* regardless of their age, set NUMBER_MIN_AGE to 0 . 98 Cleaning Up Numbered Snapshots SLES 12 SP4The following example shows a conguration to keep the last 10 important and regular snapshots regardless of age: NUMBER_CLEANUP=yes NUMBER_LIMIT_IMPORTANT=10 NUMBER_LIMIT=10 NUMBER_MIN_AGE=0 On the other hand, if you do not want to keep snapshots beyond a certain age, set NUMBER_LIMIT* to 0 and provide the age with NUMBER_MIN_AGE . The following example shows a conguration to only keep snapshots younger than ten days: NUMBER_CLEANUP=yes NUMBER_LIMIT_IMPORTANT=0 NUMBER_LIMIT=0 NUMBER_MIN_AGE=864000 7.7.2 Cleaning Up Timeline Snapshots Cleaning up timeline snapshots is controlled by the following parameters of a Snapper conguration. TIMELINE_CLEANUP Enables or disables clean-up of timeline snapshots. If enabled, snapshots are deleted when the total snapshot count exceeds a number specied with TIMELINE_LIMIT_* and an age specied with TIMELINE_MIN_AGE . Valid values: yes , no . The default value is "yes" . Example command to change or set: tux > sudo snapper -c CONFIG set-config "TIMELINE_CLEANUP=yes" TIMELINE_LIMIT_DAILY , TIMELINE_LIMIT_HOURLY , TIMELINE_LIMIT_MONTHLY , TIMELINE_LIMIT_WEEKLY , TIMELINE_LIMIT_YEARLY Number of snapshots to keep for hour, day, month, week, and year. The default value for each entry is "10" , except for TIMELINE_LIMIT_WEEKLY , which is set to "0" by default. TIMELINE_MIN_AGE 99 Cleaning Up Timeline Snapshots SLES 12 SP4Denes the minimum age in seconds a snapshot must have before it can automatically be deleted. The default value is "1800" . EXAMPLE 7.1: EXAMPLE TIMELINE CONFIGURATION TIMELINE_CLEANUP="yes" TIMELINE_CREATE="yes" TIMELINE_LIMIT_DAILY="7" TIMELINE_LIMIT_HOURLY="24" TIMELINE_LIMIT_MONTHLY="12" TIMELINE_LIMIT_WEEKLY="4" TIMELINE_LIMIT_YEARLY="2" TIMELINE_MIN_AGE="1800" This example conguration enables hourly snapshots which are automatically cleaned up. TIMELINE_MIN_AGE and TIMELINE_LIMIT_* are always both evaluated. In this example, the minimum age of a snapshot before it can be deleted is set to 30 minutes (1800 seconds). Since we create hourly snapshots, this ensures that only the latest snapshots are kept. If TIMELINE_LIMIT_DAILY is set to not zero, this means that the rst snapshot of the day is kept, too. SNAPSHOTS TO BE KEPT Hourly: The last 24 snapshots that have been made. Daily: The rst daily snapshot that has been made is kept from the last seven days. Monthly: The rst snapshot made on the last day of the month is kept for the last twelve months. Weekly: The rst snapshot made on the last day of the week is kept from the last four weeks. Yearly: The rst snapshot made on the last day of the year is kept for the last two years. 100 Cleaning Up Timeline Snapshots SLES 12 SP47.7.3 Cleaning Up Snapshot Pairs That Do Not Differ As explained in Section 7.1.1, “Types of Snapshots”, whenever you run a YaST module or execute Zypper, a pre snapshot is created on start-up and a post snapshot is created when exiting. In case you have not made any changes there will be no dierence between the pre and post snapshots. Such “empty” snapshot pairs can be automatically be deleted by setting the following parameters in a Snapper conguration: EMPTY_PRE_POST_CLEANUP If set to yes , pre and post snapshot pairs that do not dier will be deleted. The default value is "yes" . EMPTY_PRE_POST_MIN_AGE Denes the minimum age in seconds a pre and post snapshot pair that does not dier must have before it can automatically be deleted. The default value is "1800" . 7.7.4 Cleaning Up Manually Created Snapshots Snapper does not oer custom clean-up algorithms for manually created snapshots. However, you can assign the number or timeline clean-up algorithm to a manually created snapshot. If you do so, the snapshot will join the “clean-up queue” for the algorithm you specied. You can specify a clean-up algorithm when creating a snapshot, or by modifying an existing snapshot: snapper create --description "Test" --cleanup-algorithm number Creates a stand-alone snapshot (type single) for the default (root) conguration and assigns the number clean-up algorithm. snapper modify --cleanup-algorithm "timeline" 25 Modies the snapshot with the number 25 and assigns the clean-up algorithm timeline . 7.7.5 Adding Disk Quota Support In addition to the number and/or timeline clean-up algorithms described above, Snapper supports quotas. You can dene what percentage of the available space snapshots are allowed to occupy. This percentage value always applies to the Btrfs subvolume dened in the respective Snapper conguration. 101 Cleaning Up Snapshot Pairs That Do Not Differ SLES 12 SP4If Snapper was enabled during the installation, quota support is automatically enabled. In case you manually enable Snapper at a later point in time, you can enable quota support by running snapper setup-quota . This requires a valid conguration (see Section 7.5, “Creating and Modifying Snapper Configurations” for more information). Note: Btrfs Quota Groups Can Incur Degraded Performance On SUSE Linux Enterprise Server 12 SP4, using Btrfs quota groups can degrade le system performance. Quota support is controlled by the following parameters of a Snapper conguration. QGROUP The Btrfs quota group used by Snapper. If not set, run snapper setup-quota . If already set, only change if you are familiar with man 8 btrfs-qgroup . This value is set with snapper setup-quota and should not be changed. SPACE_LIMIT Limit of space snapshots are allowed to use in fractions of 1 (100%). Valid values range from 0 to 1 (0.1 = 10%, 0.2 = 20%, ...). The following limitations and guidelines apply: Quotas are only activated in addition to an existing number and/or timeline clean-up algorithm. If no clean-up algorithm is active, quota restrictions are not applied. With quota support enabled, Snapper will perform two clean-up runs if required. The rst run will apply the rules specied for number and timeline snapshots. Only if the quota is exceeded after this run, the quota-specic rules will be applied in a second run. Even if quota support is enabled, Snapper will always keep the number of snapshots specied with the NUMBER_LIMIT* and TIMELINE_LIMIT* values, even if the quota will be exceeded. It is therefore recommended to specify ranged values ( MIN-MAX ) for NUMBER_LIMIT* and TIMELINE_LIMIT* to ensure the quota can be applied. If, for example, NUMBER_LIMIT=5-20 is set, Snapper will perform a rst clean-up run and reduce the number of regular numbered snapshots to 20. In case these 20 snapshots exceed the quota, Snapper will delete the oldest ones in a second run until the quota is met. A minimum of ve snapshots will always be kept, regardless of the amount of space they occupy. 102 Adding Disk Quota Support SLES 12 SP47.8 Frequently Asked Questions Q: Why does Snapper never show changes in /var/log , /tmp and other directories? A: For some directories we decided to exclude them from snapshots. See Section  7.1.2, “Directories That Are Excluded from Snapshots” for a list and reasons. To exclude a path from snapshots we create a subvolume for that path. Q: How much disk space is used by snapshots? How can I free disk space? A: Displaying the amount of disk space a snapshot allocates is currently not supported by the Btrfs tools. However, if you have quota enabled, it is possible to determine how much space would be freed if all snapshots would be deleted: 1. Get the quota group ID ( 1/0 in the following example): tux > sudo snapper -c root get-config | grep QGROUP QGROUP | 1/0 2. Rescan the subvolume quotas: tux > sudo btrfs quota rescan -w / 3. Show the data of the quota group ( 1/0 in the following example): tux > sudo btrfs qgroup show / | grep "1/0" 1/0 4.80GiB 108.82MiB The third column shows the amount of space that would be freed when deleting all snapshots ( 108.82MiB ). To free space on a Btrfs partition containing snapshots you need to delete unneeded snapshots rather than les. Older snapshots occupy more space than recent ones. See Section 7.1.3.4, “Controlling Snapshot Archiving” for details. Doing an upgrade from one service pack to another results in snapshots occupying a lot of disk space on the system subvolumes, because a lot of data gets changed (package updates). Manually deleting these snapshots after they are no longer needed is recommended. See Section 7.6.4, “Deleting Snapshots” for details. Q: Can I boot a snapshot from the boot loader? A: Yes—refer to Section 7.3, “System Rollback by Booting from Snapshots” for details. Q: Can a snapshot be protected from deletion? 103 Frequently Asked Questions SLES 12 SP4A: Currently Snapper does not oer means to prevent a snapshot from being deleted manually. However, you can prevent snapshots from being automatically deleted by clean-up algorithms. Manually created snapshots (see Section 7.6.2, “Creating Snapshots”) have no clean-up algorithm assigned unless you specify one with --cleanup-algorithm . Automatically created snapshots always either have the number or timeline algorithm assigned. To remove such an assignment from one or more snapshots, proceed as follows: 1. List all available snapshots: tux > sudo snapper list -a 2. Memorize the number of the snapshot(s) you want to prevent from being deleted. 3. Run the following command and replace the number placeholders with the number(s) you memorized: tux > sudo snapper modify --cleanup-algorithm "" #1 #2 #n 4. Check the result by running snapper list -a again. The entry in the column Cleanup should now be empty for the snapshots you modied. Q: Where can I get more information on Snapper? A: See the Snapper home page at http://snapper.io/ . 104 Frequently Asked Questions SLES 12 SP48 Remote Access with VNC Virtual Network Computing (VNC) enables you to control a remote computer via a graphical desktop (as opposed to a remote shell access). VNC is platform- independent and lets you access the remote machine from any operating system. SUSE Linux Enterprise Server supports two dierent kinds of VNC sessions: One- time sessions that “live” as long as the VNC connection from the client is kept up, and persistent sessions that “live” until they are explicitly terminated. Note: Session Types A machine can oer both kinds of sessions simultaneously on dierent ports, but an open session cannot be converted from one type to the other. 8.1 The vncviewer Client To connect to a VNC service provided by a server, a client is needed. The default in SUSE Linux Enterprise Server is vncviewer , provided by the tigervnc package. 8.1.1 Connecting Using the vncviewer CLI To start your VNC viewer and initiate a session with the server, use the command: tux > vncviewer jupiter.example.com:1 Instead of the VNC display number you can also specify the port number with two colons: tux > vncviewer jupiter.example.com::5901 Note: Display and Port Number The actual display or port number you specify in the VNC client must be the same as the display or port number picked by the vncserver command on the target machine. See Section 8.4, “Persistent VNC Sessions” for further info. 105 The vncviewer Client SLES 12 SP48.1.2 Connecting Using the vncviewer GUI By running vncviewer without specifying --listen or a host to connect to, it will show a window to ask for connection details. Enter the host into the VNC server eld like in Section 8.1.1, “Connecting Using the vncviewer CLI” and click Connect. FIGURE 8.1: VNCVIEWER 8.1.3 Notification of Unencrypted Connections The VNC protocol supports dierent kinds of encrypted connections, not to be confused with password authentication. If a connection does not use TLS, the text “(Connection not encrypted!)” can be seen in the window title of the VNC viewer. 8.2 Remmina: the Remote Desktop Client Remmina is a modern and feature-rich remote desktop client. It supports several access methods, for example VNC, SSH, RDP, or Spice. 8.2.1 Installation To use Remmina, verify whether the remmina package is installed on your system, and install it if not. Remember to install the VNC plug-in for Remmina as well: root # zypper in remmina remmina-plugin-vnc 106 Connecting Using the vncviewer GUI SLES 12 SP48.2.2 Main Window Run Remmina by entering the remmina command. FIGURE 8.2: REMMINA''S MAIN WINDOW The main application window shows the list of stored remote sessions. Here you can add and save a new remote session, quick-start a new session without saving it, start a previously saved session, or set Remmina''s global preferences. 8.2.3 Adding Remote Sessions To add and save a new remote session, click in the top left of the main window. The Remote Desktop Preference window opens. 107 Main Window SLES 12 SP4FIGURE 8.3: REMOTE DESKTOP PREFERENCE Complete the elds that specify your newly added remote session prole. The most important are: Name Name of the prole. It will be listed in the main window. Protocol The protocol to use when connecting to the remote session, for example VNC. Server The IP or DNS address and display number of the remote server. User name, Password Credentials to use for remote authentication. Leave empty for no authentication. Color depth, Quality Select the best options according to your connection speed and quality. Select the Advanced tab to enter more specic settings. 108 Adding Remote Sessions SLES 12 SP4Tip: Disable Encryption If the communication between the client and the remote server is not encrypted, activate Disable encryption, otherwise the connection fails. Select the SSH tab for advanced SSH tunneling and authentication options. Conrm with Save. Your new prole will be listed in the main window. 8.2.4 Starting Remote Sessions You can either start a previously saved session, or quick-start a remote session without saving the connection details. 8.2.4.1 Quick-starting Remote Sessions To start a remote session quickly without adding and saving connection details, use the drop- down box and text eld at the top of the main window. FIGURE 8.4: QUICK-STARTING Select the communication protocol from the drop-down box, for example ''VNC'', then enter the VNC server''s DNS or IP address followed by a colon and a display number, and conrm with Enter . 8.2.4.2 Opening Saved Remote Sessions To open a specic remote session, double-click it from the list of sessions. 8.2.4.3 Remote Sessions Window Remote sessions are opened in tabs of a separate window. Each tab hosts one session. The toolbar on the left of the window helps you manage the windows/sessions; for example toggle fullscreen mode, resize the window to match the display size of the session, send specic keystrokes to the session, take screenshots of the session, or set the image quality. 109 Starting Remote Sessions SLES 12 SP4FIGURE 8.5: REMMINA VIEWING SLES 15 REMOTE SESSION 8.2.5 Editing, Copying, and Deleting Saved Sessions To edit a saved remote session, right-click its name in Remmina''s main window and select Edit. Refer to Section 8.2.3, “Adding Remote Sessions” for the description of the relevant elds. To copy a saved remote session, right-click its name in Remmina''s main window and select Copy. In the Remote Desktop Preference window, change the name of the prole, optionally adjust relevant options, and conrm with Save. To delete a saved remote session, right-click its name in Remmina''s main window and select Delete. Conrm with Yes in the next dialog. 8.2.6 Running Remote Sessions from the Command Line If you need to open a remote session from the command line or from a batch le without rst opening the main application window, use the following syntax: tux > remmina -c profile_name.remmina 110 Editing, Copying, and Deleting Saved Sessions SLES 12 SP4Remmina''s prole les are stored in the .local/share/remmina/ directory in your home directory. To determine which prole le belongs to the session you want to open, run Remmina, click the session name in the main window, and read the path to the prole le in the window''s status line at the bottom. FIGURE 8.6: READING PATH TO THE PROFILE FILE While Remmina is not running, you can rename the prole le to to a more reasonable le name, such as sle15.remmina . You can even copy the prole le to your custom directory and run it using the remmina -c command from there. 8.3 One-time VNC Sessions A one-time session is initiated by the remote client. It starts a graphical login screen on the server. This way you can choose the user which starts the session and, if supported by the login manager, the desktop environment. When you terminate the client connection to such a VNC session, all applications started within that session will be terminated, too. One-time VNC sessions cannot be shared, but it is possible to have multiple sessions on a single host at the same time. PROCEDURE 8.1: ENABLING ONE-TIME VNC SESSIONS 1. Start YaST Network Services Remote Administration (VNC). 2. Check Allow Remote Administration Without Session Management. 3. Activate Enable access using a web browser if you plan to access the VNC session in a Web browser window. 4. If necessary, also check Open Port in Firewall (for example, when your network interface is congured to be in the External Zone). If you have more than one network interface, restrict opening the rewall ports to a specic interface via Firewall Details. 111 One-time VNC Sessions SLES 12 SP45. Conrm your settings with Next. 6. In case not all needed packages are available yet, you need to approve the installation of missing packages. Tip: Restart the Display Manager YaST makes changes to the display manager settings. You need to log out of your current graphical session and restart the display manager for the changes to take eect. FIGURE 8.7: REMOTE ADMINISTRATION 8.3.1 Available Configurations The default conguration on SUSE Linux Enterprise Server serves sessions with a resolution of 1024x768 pixels at a color depth of 16-bit. The sessions are available on ports 5901 for “regular” VNC viewers (equivalent to VNC display 1 ) and on port 5801 for Web browsers. Other congurations can be made available on dierent ports, see Section 8.3.3, “Configuring One- time VNC Sessions”. 112 Available Configurations SLES 12 SP4VNC display numbers and X display numbers are independent in one-time sessions. A VNC display number is manually assigned to every conguration that the server supports (:1 in the example above). Whenever a VNC session is initiated with one of the congurations, it automatically gets a free X display number. By default, both the VNC client and server try to communicate securely via a self-signed SSL certicate, which is generated after installation. You can either use the default one, or replace it with your own. When using the self-signed certicate, you need to conrm its signature before the rst connection. 8.3.2 Initiating a One-time VNC Session To connect to a one-time VNC session, a VNC viewer must be installed, see also Section 8.1, “The vncviewer Client”. 8.3.3 Configuring One-time VNC Sessions You can skip this section, if you do not need or want to modify the default conguration. One-time VNC sessions are started via the systemd socket xvnc.socket . By default it oers six conguration blocks: three for VNC viewers ( vnc1 to vnc3 ), and three serving a Java applet ( vnchttpd1 to vnchttpd3 ). By default only vnc1 and vnchttpd1 are active. To activate the VNC server socket at boot time, run the following command: sudo systemctl enable xvnc.socket To start the socket immediately, run: sudo systemctl start xvnc.socket The Xvnc server can be congured via the server_args option. For a list of options, see Xvnc --help . When adding custom congurations, make sure they are not using ports that are already in use by other congurations, other services, or existing persistent VNC sessions on the same host. Activate conguration changes by entering the following command: tux > sudo systemctl reload xvnc.socket 113 Initiating a One-time VNC Session SLES 12 SP4Important: Firewall and VNC Ports When activating Remote Administration as described in Procedure 8.1, “Enabling One-time VNC Sessions”, the ports 5801 and 5901 are opened in the rewall. If the network interface serving the VNC sessions is protected by a rewall, you need to manually open the respective ports when activating additional ports for VNC sessions. See Book “Security Guide”, Chapter 15 “Masquerading and Firewalls” for instructions. 8.4 Persistent VNC Sessions A persistent session can be accessed from multiple clients simultaneously. This is ideal for demonstration purposes where one client has full access and all other clients have view-only access. Another use case are trainings where the trainer might need access to the trainee''s desktop. Tip: Connecting to a Persistent VNC Session To connect to a persistent VNC session, a VNC viewer must be installed. Refer to Section 8.1, “The vncviewer Client” for more details. There are two types of persistent VNC sessions: VNC Session Initiated Using vncserver VNC Session Initiated Using vncmanager 8.4.1 VNC Session Initiated Using vncserver This type of persistent VNC session is initiated on the server. The session and all applications started in this session run regardless of client connections until the session is terminated. Access to persistent sessions is protected by two possible types of passwords: a regular password that grants full access or an optional view-only password that grants a non-interactive (view-only) access. A session can have multiple client connections of both kinds at once. 114 Persistent VNC Sessions SLES 12 SP4PROCEDURE 8.2: STARTING A PERSISTENT VNC SESSION USING vncserver 1. Open a shell and make sure you are logged in as the user that should own the VNC session. 2. If the network interface serving the VNC sessions is protected by a rewall, you need to manually open the port used by your session in the rewall. If starting multiple sessions you may alternatively open a range of ports. See Book “Security Guide”, Chapter 15 “Masquerading and Firewalls” for details on how to congure the rewall. vncserver uses the ports 5901 for display :1 , 5902 for display :2 , and so on. For persistent sessions, the VNC display and the X display usually have the same number. 3. To start a session with a resolution of 1024x769 pixel and with a color depth of 16-bit, enter the following command: vncserver -alwaysshared -geometry 1024x768 -depth 16 The vncserver command picks an unused display number when none is given and prints its choice. See man 1 vncserver for more options. When running vncserver for the rst time, it asks for a password for full access to the session. If needed, you can also provide a password for view-only access to the session. The password(s) you are providing here are also used for future sessions started by the same user. They can be changed with the vncpasswd command. Important: Security Considerations Make sure to use strong passwords of signicant length (eight or more characters). Do not share these passwords. To terminate the session shut down the desktop environment that runs inside the VNC session from the VNC viewer as you would shut it down if it was a regular local X session. 115 VNC Session Initiated Using vncserver SLES 12 SP4If you prefer to manually terminate a session, open a shell on the VNC server and make sure you are logged in as the user that owns the VNC session you want to terminate. Run the following command to terminate the session that runs on display :1 : vncserver -kill :1 8.4.1.1 Configuring Persistent VNC Sessions Persistent VNC sessions can be congured by editing $HOME/.vnc/xstartup . By default this shell script starts the same GUI/window manager it was started from. In SUSE Linux Enterprise Server this will either be GNOME or IceWM. If you want to start your session with a window manager of your choice, set the variable WINDOWMANAGER : WINDOWMANAGER=gnome vncserver -geometry 1024x768 WINDOWMANAGER=icewm vncserver -geometry 1024x768 Note: One Configuration for Each User Persistent VNC sessions are congured in a single per-user conguration. Multiple sessions started by the same user will all use the same start-up and password les. 8.4.2 VNC Session Initiated Using vncmanager PROCEDURE 8.3: ENABLING PERSISTENT VNC SESSIONS 1. Start YaST Network Services Remote Administration (VNC). 2. Activate Allow Remote Administration With Session Management. 3. Activate Enable access using a web browser if you plan to access the VNC session in a Web browser window. 4. If necessary, also check Open Port in Firewall (for example, when your network interface is congured to be in the External Zone). If you have more than one network interface, restrict opening the rewall ports to a specic interface via Firewall Details. 5. Conrm your settings with Next. 6. In case not all needed packages are available yet, you need to approve the installation of missing packages. 116 VNC Session Initiated Using vncmanager SLES 12 SP4Tip: Restart the Display Manager YaST makes changes to the display manager settings. You need to log out of your current graphical session and restart the display manager for the changes to take eect. 8.4.2.1 Configuring Persistent VNC Sessions After you enable the VNC session management as described in Procedure 8.3, “Enabling Persistent VNC Sessions”, you can normally connect to the remote session with your favorite VNC viewer, such as vncviewer or Remmina. You will be presented with the login screen. After you log in, the ''VNC'' icon will appear in the system tray of your desktop environment. Click the icon to open the VNC Session window. If it does not appear or if your desktop environment does not support icons in the system tray, run vncmanager-controller manually. FIGURE 8.8: VNC SESSION SETTINGS There are several settings that inuence the VNC session''s behavior: Non-persistent, private 117 VNC Session Initiated Using vncmanager SLES 12 SP4This is equivalent to a one-time session. It is not visible to others and will be terminated after you disconnect from it. Refer to Section  8.3, “One-time VNC Sessions” for more information. Persistent, visible The session is visible to other users and keeps running even after you disconnect from it. Session name Here you can specify the name of the persistent session so that it is easily identied when reconnecting. No password required The session will be freely accessible without having to log in under user credentials. Require user login You need to log in with a valid user name and password to access the session. List the valid user names in the Allowed users text box. Allow one client at a time Prevents multiple users from joining the session at the same time. Allow multiple clients at a time Allows multiple users to join the persistent session at the same time. Good for remote presentations or trainings. Conrm with OK. 118 VNC Session Initiated Using vncmanager SLES 12 SP48.4.2.2 Joining Persistent VNC Sessions After you set up a persistent VNC session as described in Section 8.4.2.1, “Configuring Persistent VNC Sessions”, you can join it with your VNC viewer. After your VNC client connects to the server, you will be prompted to choose whether you want to create a new session or join the existing one: FIGURE 8.9: JOINING A PERSISTENT VNC SESSION After you click the name of the existing session, you may be asked for login credentials, depending on the persistent session settings. 8.5 Encrypted VNC Communication If the VNC server is set up properly, all communication between the VNC server and the client is encrypted. The authentication happens at the beginning of the session; the actual data transfer only begins afterward. 119 Encrypted VNC Communication SLES 12 SP4Whether for a one-time or a persistent VNC session, security options are congured via the - securitytypes parameter of the /usr/bin/Xvnc command located on the server_args line. The -securitytypes parameter selects both authentication method and encryption. It has the following options: AUTHENTICATIONS None, TLSNone, X509None No authentication. VncAuth, TLSVnc, X509Vnc Authentication using custom password. Plain, TLSPlain, X509Plain Authentication using PAM to verify user''s password. ENCRYPTIONS None, VncAuth, Plain No encryption. TLSNone, TLSVnc, TLSPlain Anonymous TLS encryption. Everything is encrypted, but there is no verication of the remote host. So you are protected against passive attackers, but not against man-in-the- middle attackers. X509None, X509Vnc, X509Plain TLS encryption with certicate. If you use a self-signed certicate, you will be asked to verify it on the rst connection. On subsequent connections you will be warned only if the certicate changed. So you are protected against everything except man-in-the-middle on the rst connection (similar to typical SSH usage). If you use a certicate signed by a certicate authority matching the machine name, then you get full security (similar to typical HTTPS usage). Tip: Path to Certificate and Key With X509 based encryption, you need to specify the path to the X509 certicate and the key with -X509Cert and -X509Key options. 120 Encrypted VNC Communication SLES 12 SP4If you select multiple security types separated by comma, the rst one supported and allowed by both client and server will be used. That way you can congure opportunistic encryption on the server. This is useful if you need to support VNC clients that do not support encryption. On the client, you can also specify the allowed security types to prevent a downgrade attack if you are connecting to a server which you know has encryption enabled (although our vncviewer will warn you with the "Connection not encrypted!" message in that case). 121 Encrypted VNC Communication SLES 12 SP49 File Copying with RSync Today, a typical user has several computers: home and workplace machines, a laptop, a smartphone or a tablet. This makes the task of keeping les and documents in sync across multiple devices all more important. Warning: Risk of Data Loss Before you start using a synchronization tool, you should familiarize yourself with its features and functionality. Make sure to back up your important les. 9.1 Conceptual Overview For synchronizing a large amount of data over a slow network connection, Rsync oers a reliable method of transmitting only changes within les. This applies not only to text les but also binary les. To detect the dierences between les, Rsync subdivides the les into blocks and computes check sums over them. Detecting changes requires some computing power. So make sure that machines on both ends have enough resources, including RAM. Rsync can be particularly useful when large amounts of data containing only minor changes need to be transmitted regularly. This is often the case when working with backups. Rsync can also be useful for mirroring staging servers that store complete directory trees of Web servers to a Web server in a DMZ. Despite its name, Rsync is not a synchronization tool. Rsync is a tool that copies data only in one direction at a time. It does not and cannot do the reverse. If you need a bidirectional tool which is able to synchronize both source and destination, use Csync. 9.2 Basic Syntax Rsync is a command-line tool that has the following basic syntax: rsync [OPTION] SOURCE [SOURCE]... DEST 122 Conceptual Overview SLES 12 SP4You can use Rsync on any local or remote machine, provided you have access and write permissions. It is possible to have multiple SOURCE entries. The SOURCE and DEST placeholders can be paths, URLs, or both. Below are the most common Rsync options: -v Outputs more verbose text -a Archive mode; copies les recursively and preserves timestamps, user/group ownership, le permissions, and symbolic links -z Compresses the transmitted data Note: Trailing Slashes Count When working with Rsync, you should pay particular attention to trailing slashes. A trailing slash after the directory denotes the content of the directory. No trailing slash denotes the directory itself. 9.3 Copying Files and Directories Locally The following description assumes that the current user has write permissions to the directory /var/backup . To copy a single le from one directory on your machine to another path, use the following command: tux > rsync -avz backup.tar.xz /var/backup/ The le backup.tar.xz is copied to /var/backup/ ; the absolute path will be /var/backup/ backup.tar.xz . Do not forget to add the trailing slash after the /var/backup/ directory! If you do not insert the slash, the le backup.tar.xz is copied to /var/backup (le) not inside the directory / var/backup/ ! Copying a directory is similar to copying a single le. The following example copies the directory tux/ and its content into the directory /var/backup/ : tux > rsync -avz tux /var/backup/ 123 Copying Files and Directories Locally SLES 12 SP4Find the copy in the absolute path /var/backup/tux/ . 9.4 Copying Files and Directories Remotely The Rsync tool is required on both machines. To copy les from or to remote directories requires an IP address or a domain name. A user name is optional if your current user names on the local and remote machine are the same. To copy the le file.tar.xz from your local host to the remote host 192.168.1.1 with same users (being local and remote), use the following command: tux > rsync -avz file.tar.xz tux@192.168.1.1: Depending on what you prefer, these commands are also possible and equivalent: tux > rsync -avz file.tar.xz 192.168.1.1:~ tux > rsync -avz file.tar.xz 192.168.1.1:/home/tux In all cases with standard conguration, you will be prompted to enter your passphrase of the remote user. This command will copy file.tar.xz to the home directory of user tux (usually /home/tux ). Copying a directory remotely is similar to copying a directory locally. The following example copies the directory tux/ and its content into the remote directory /var/backup/ on the 192.168.1.1 host: tux > rsync -avz tux 192.168.1.1:/var/backup/ Assuming you have write permissions on the host 192.168.1.1 , you will nd the copy in the absolute path /var/backup/tux . 9.5 Configuring and Using an Rsync Server Rsync can run as a daemon ( rsyncd ) listening on default port 873 for incoming connections. This daemon can receive “copying targets”. 124 Copying Files and Directories Remotely SLES 12 SP4The following description explains how to create an Rsync server on jupiter with a backup target. This target can be used to store your backups. To create an Rsync server, do the following: PROCEDURE 9.1: SETTING UP AN RSYNC SERVER 1. On jupiter, create a directory to store all your backup les. In this example, we use / var/backup : root # mkdir /var/backup 2. Specify ownership. In this case, the directory is owned by user tux in group users : root # chown tux.users /var/backup 3. Congure the rsyncd daemon. We will separate the conguration le into a main le and some “modules” which hold your backup target. This makes it easier to add additional targets later. Global values can be stored in /etc/rsyncd.d/*.inc les, whereas your modules are placed in /etc/ rsyncd.d/*.conf les: a. Create a directory /etc/rsyncd.d/ : root # mkdir /etc/rsyncd.d/ b. In the main conguration le /etc/rsyncd.conf , add the following lines: # rsyncd.conf main configuration file log file = /var/log/rsync.log pid file = /var/lock/rsync.lock &merge /etc/rsyncd.d 1 &include /etc/rsyncd.d 2 1 Merges global values from /etc/rsyncd.d/*.inc les into the main conguration le. 2 Loads any modules (or targets) from /etc/rsyncd.d/*.conf les. These les should not contain any references to global values. c. Create your module (your backup target) in the le /etc/rsyncd.d/backup.conf with the following lines: # backup.conf: backup module [backup] 1 125 Configuring and Using an Rsync Server SLES 12 SP4uid = tux 2 gid = users 2 path = /var/backup 3 auth users = tux 4 secrets file = /etc/rsyncd.secrets 5 comment = Our backup target 1 The backup target. You can use any name you like. However, it is a good idea to name a target according to its purpose and use the same name in your *.conf le. 2 Species the user name or group name that is used when the le transfer takes place. 3 Denes the path to store your backups (from Step 1). 4 Species a comma-separated list of allowed users. In its simplest form, it contains the user names that are allowed to connect to this module. In our case, only user tux is allowed. 5 Species the path of a le that contains lines with user names and plain passwords. d. Create the /etc/rsyncd.secrets le with the following content and replace PASSPHRASE : # user:passwd tux:PASSPHRASE e. Make sure the le is only readable by root : root # chmod 0600 /etc/rsyncd.secrets 4. Start and enable the rsyncd daemon with: root # systemctl enable rsyncd root # systemctl start rsyncd 5. Test the access to your Rsync server: tux > rsync jupiter:: You should see a response that looks like this: backup Our backup target 126 Configuring and Using an Rsync Server SLES 12 SP4Otherwise, check your conguration le, rewall and network settings. The above steps create an Rsync server that can now be used to store backups. The example also creates a log le listing all connections. This le is stored in /var/log/rsyncd.log . This is useful if you want to debug your transfers. To list the content of your backup target, use the following command: rsync -avz jupiter::backup This command lists all les present in the directory /var/backup on the server. This request is also logged in the log le /var/log/rsyncd.log . To start an actual transfer, provide a source directory. Use . for the current directory. For example, the following command copies the current directory to your Rsync backup server: rsync -avz . jupiter::backup By default, Rsync does not delete les and directories when it runs. To enable deletion, the additional option --delete must be stated. To ensure that no newer les are deleted, the option --update can be used instead. Any conicts that arise must be resolved manually. 9.6 For More Information CSync Bidirectional le synchronizer, see https://www.csync.org/ . RSnapshot Creates incremental backups, see http://rsnapshot.org . Unison A le synchronizer similar to CSync but with a graphical interface, see http:// www.seas.upenn.edu/~bcpierce/unison/ . Rear A disaster recovery framework, see the Administration Guide of the SUSE Linux Enterprise High Availability Extension https://www.suse.com/documentation/sle-ha-12/ . 127 For More Information SLES 12 SP4II Booting a Linux System 10 Introduction to the Boot Process 129 11 UEFI (Unified Extensible Firmware Interface) 137 12 The Boot Loader GRUB 2 146 13 The systemd Daemon 16610 Introduction to the Boot Process Booting a Linux system involves dierent components and tasks. After a rmware and hardware initialization process, which depends on the machine''s architecture, the kernel is started by means of the boot loader GRUB 2. After this point, the boot process is completely controlled by the operating system and handled by systemd . systemd provides a set of “targets” that boot congurations for everyday usage, maintenance or emergencies. 10.1 Terminology This chapter uses terms that can be interpreted ambiguously. To understand how they are used here, read the denitions below: init Two dierent processes are commonly named “init”: The initramfs process mounting the root le system The operating system process that starts all other processes that is executed from the real root le system In both cases, the systemd program is taking care of this task. It is rst executed from the initramfs to mount the root le system. Once that has succeeded, it is re-executed from the root le system as the initial process. To avoid confusing these two systemd processes, we refer to the rst process as init on initramfs and to the second one as systemd. initrd / initramfs An initrd (initial RAM disk) is an image le containing a root le system image which is loaded by the kernel and mounted from /dev/ram as the temporary root le system. Mounting this le system requires a le system driver. Beginning with kernel 2.6.13, the initrd has been replaced by the initramfs (initial RAM le system), which does not require a le system driver to be mounted. SUSE Linux Enterprise Server exclusively uses an initramfs . However, since the initramfs is stored as /boot/initrd , it is often called “initrd”. In this chapter we exclusively use the name initramfs . 129 Terminology SLES 12 SP410.2 The Linux Boot Process The Linux boot process consists of several stages, each represented by a dierent component: 1. Section 10.2.1, “The Initialization and Boot Loader Phase” 2. Section 10.2.2, “The Kernel Phase” 3. Section 10.2.3, “The init on initramfs Phase” 4. Section 10.2.4, “The systemd Phase” 10.2.1 The Initialization and Boot Loader Phase During the initialization phase the machine''s hardware is set up and the devices are prepared. This process diers signicantly between hardware architectures. SUSE Linux Enterprise Server uses the boot loader GRUB 2 on all architectures. Depending on the architecture and rmware, starting the GRUB 2 boot loader can be a multi-step process. The purpose of the boot loader is to load the kernel and the initial, RAM-based le system (initramfs). For more information about GRUB 2, refer to Chapter 12, The Boot Loader GRUB 2. 10.2.1.1 Initialization and Boot Loader Phase on AArch64 and AMD64/ Intel 64 After turning on the computer, the BIOS or the UEFI initializes the screen and keyboard, and tests the main memory. Up to this stage, the machine does not access any mass storage media. Subsequently, the information about the current date, time, and the most important peripherals are loaded from the CMOS values. When the boot media and its geometry are recognized, the system control passes from the BIOS/UEFI to the boot loader. On a machine equipped with a traditional BIOS, only code from the rst physical 512-byte data sector (the Master Boot Record, MBR) of the boot disk can be loaded. Only a minimal GRUB 2 ts into the MBR. Its sole purpose is to load a GRUB 2 core image containing le system drivers from the gap between the MBR and the rst partition (MBR partition table) or from the BIOS boot partition (GPT partition table). This image contains le system drivers and therefore is able to access /boot located on the root le system. /boot contains additional modules for GRUB 2 core as well as the kernel and the initramfs image. Once it has access to this partition, GRUB 2 loads the kernel and the initramfs image into memory and hands control over to the kernel. 130 The Linux Boot Process SLES 12 SP4When booting a BIOS system from an encrypted le system that includes an encrypted /boot partition, you need to enter the password for decryption twice. It is rst needed by GRUB 2 to decrypt /boot and then for systemd to mount the encrypted volumes. On machines with UEFI the boot process is much simpler than on machines with a traditional BIOS. The rmware is able to read from a FAT formatted system partition of disks with a GPT partition table. This EFI system-partition (in the running system mounted as /boot/efi ) holds enough space to host a fully-edged GRUB 2 which is directly loaded and executed by the rmware. If the BIOS/UEFI supports network booting, it is also possible to congure a boot server that provides the boot loader. The system can then be booted via PXE. The BIOS/UEFI acts as the boot loader. It gets the boot image from the boot server and starts the system. This is completely independent of local hard disks. 10.2.1.2 Initialization and Boot Loader Phase on IBM z Systems On IBM z Systems the boot process must be initialized by a boot loader called zipl (z initial program load). Although zipl supports reading from various le systems, it does not support the SLE default le system (Btrfs) or booting from snapshots. SUSE Linux Enterprise Server therefore uses a two-stage boot process that ensures full Btrfs support at boot time: 1. zipl boots from the partition /boot/zipl that can be formatted with the Ext2, Ext3, Ext4, or XFS le system. This partition contains a minimal kernel and an initramfs that are loaded into memory. The initramfs contains a Btrfs driver (among others) and the boot loader GRUB 2. The kernel is started with a parameter initgrub , which tells it to start GRUB 2. 2. The kernel mounts the root le system, so /boot becomes accessible. Now GRUB 2 is started from the initramfs. It reads its conguration from /boot/grub2/grub.cfg and loads the nal kernel and initramfs from /boot . The new kernel now gets loaded via Kexec. 10.2.2 The Kernel Phase When the boot loader has passed on system control, the boot process is the same on all architectures. The boot loader loads both the kernel and an initial RAM-based le system ( initramfs ) into memory and the kernel takes over. 131 The Kernel Phase SLES 12 SP4After the kernel has set up memory management and has detected the CPU type and its features, it initializes the hardware and mounts the temporary root le system from the memory that was loaded with the initramfs . 10.2.2.1 The initramfs file initramfs (initial RAM le system) is a small cpio archive that the kernel can load into a RAM disk. It is located at /boot/initrd . It can be created with a tool called dracut—refer to man 8 dracut for details. The initramfs provides a minimal Linux environment that enables the execution of programs before the actual root le system is mounted. This minimal Linux environment is loaded into memory by BIOS or UEFI routines and does not have specic hardware requirements other than sucient memory. The initramfs archive must always provide an executable named init that executes the systemd daemon on the root le system for the boot process to proceed. Before the root le system can be mounted and the operating system can be started, the kernel needs the corresponding drivers to access the device on which the root le system is located. These drivers may include special drivers for certain kinds of hard disks or even network drivers to access a network le system. The needed modules for the root le system are loaded by init on initramfs . After the modules are loaded, udev provides the initramfs with the needed devices. Later in the boot process, after changing the root le system, it is necessary to regenerate the devices. This is done by the systemd unit systemd-udev-trigger.service . 10.2.2.1.1 Regenerating the initramfs Since the initramfs contains drivers, it needs to be updated whenever a new version of one of its drivers is available. This is done automatically when installing the package containing the driver update. YaST or zypper will inform you about this by showing the output of the command that generates the initramfs . However, there are some occasions when you need to regenerate an initramfs manually: Adding Drivers Because of Hardware Changes Moving System Directories to a RAID or LVM Adding Disks to an LVM Group or Btrfs RAID Containing the Root File System Changing Kernel Variables 132 The Kernel Phase SLES 12 SP4Adding Drivers Because of Hardware Changes If you need to change hardware (for example, hard disks), and this hardware requires dierent drivers to be in the kernel at boot time, you must update the initramfs le. Open or create /etc/dracut.conf.d/10-DRIVER.conf and add the following line (mind the leading whitespace): force_drivers+=" DRIVER1" Replace DRIVER1 with the module name of the driver. If you need to add more than one driver, list them space-separated: force_drivers+=" DRIVER1 DRIVER2" Proceed with Procedure 10.1, “Generate an initramfs”. Moving System Directories to a RAID or LVM Whenever you move swap les, or system directories like /usr in a running system to a RAID or logical volume, you need to create an initramfs that contains support for software RAID or LVM drivers. To do so, create the respective entries in /etc/fstab and mount the new entries (for example with mount -a and/or swapon -a ). Proceed with Procedure 10.1, “Generate an initramfs”. Adding Disks to an LVM Group or Btrfs RAID Containing the Root File System Whenever you add (or remove) a disk to a logical volume group or a Btrfs RAID containing the root le system, you need to create an initramfs that contains support for the enlarged volume. Follow the instructions at Procedure 10.1, “Generate an initramfs”. Proceed with Procedure 10.1, “Generate an initramfs”. Changing Kernel Variables If you change the values of kernel variables via the sysctl interface by editing related les ( /etc/sysctl.conf or /etc/sysctl.d/*.conf ), the change will be lost on the next system reboot. Even if you load the values with sysctl --system at runtime, the changes are not saved into the initramfs le. You need to update it by proceeding as outlined in Procedure 10.1, “Generate an initramfs”. PROCEDURE 10.1: GENERATE AN INITRAMFS Note that all commands in the following procedure need to be executed as user root . 1. Generate a new initramfs le by running 133 The Kernel Phase SLES 12 SP4dracut MY_INITRAMFS Replace MY_INITRAMFS with a le name of your choice. The new initramfs will be created as /boot/MY_INITRAMFS . Alternatively, run dracut -f . This will overwrite the currently used, existing le. 2. (Skip this step if you ran dracut -f in the previous step.) Create a link to the initramfs le you created in the previous step: (cd /boot && ln -sf MY_INITRAMFS initrd) 3. On the IBM z Systems architecture, additionally run grub2-install . 10.2.3 The init on initramfs Phase The temporary root le system mounted by the kernel from the initramfs contains the executable systemd (which is called init on initramfs in the following, also see Section 10.1, “Terminology”). This program performs all actions needed to mount the proper root le system. It provides kernel functionality for the needed le system and device drivers for mass storage controllers with udev . The main purpose of init on initramfs is to prepare the mounting of and access to the real root le system. Depending on your system conguration, init on initramfs is responsible for the following tasks. Loading Kernel Modules Depending on your hardware conguration, special drivers may be needed to access the hardware components of your computer (the most important component being your hard disk). To access the nal root le system, the kernel needs to load the proper le system drivers. Providing Block Special Files The kernel generates device events depending on loaded modules. udev handles these events and generates the required special block les on a RAM le system in /dev . Without those special les, the le system and other devices would not be accessible. Managing RAID and LVM Setups If you congured your system to hold the root le system under RAID or LVM, init on initramfs sets up LVM or RAID to enable access to the root le system later. 134 The init on initramfs Phase SLES 12 SP4Managing the Network Configuration If you congured your system to use a network-mounted root le system (mounted via NFS), init must make sure that the proper network drivers are loaded and that they are set up to allow access to the root le system. If the le system resides on a network block device like iSCSI or SAN, the connection to the storage server is also set up by init on initramfs . SUSE Linux Enterprise Server supports booting from a secondary iSCSI target if the primary target is not available. For more details regarding conguration of the booting iSCSI target refer to Book “Storage Administration Guide”, Chapter 14 “Mass Storage over IP Networks: iSCSI”, Section 14.3.1 “Using YaST for the iSCSI Initiator Configuration”. Note: Handling of Mount Failures If the root le system fails to mount from within the boot environment, it must be checked and repaired before the boot can continue. The le system checker will be automatically started for Ext3 and Ext4 le systems. The repair process is not automated for XFS and Btrfs le systems, and the user is presented with information describing the options available to repair the le system. When the le system has been successfully repaired, exiting the boot environment will cause the system to retry mounting the root le system. If successful, the boot will continue normally. 10.2.3.1 The init on initramfs Phase in the Installation Process When init on initramfs is called during the initial boot as part of the installation process, its tasks dier from those mentioned above. Note that the installation system does not start systemd from initramfs—these tasks are performed by linuxrc . Finding the Installation Medium When starting the installation process, your machine loads an installation kernel and a special init containing the YaST installer. The YaST installer is running in a RAM le system and needs to have information about the location of the installation medium to access it for installing the operating system. Initiating Hardware Recognition and Loading Appropriate Kernel Modules As mentioned in Section  10.2.2.1, “The initramfs file”, the boot process starts with a minimum set of drivers that can be used with most hardware congurations. On AArch64, POWER, and AMD64/Intel  64 machines, linuxrc starts an initial hardware scanning 135 The init on initramfs Phase SLES 12 SP4process that determines the set of drivers suitable for your hardware conguration. On IBM z Systems, a list of drivers and their parameters needs to be provided, for example via linuxrc or a parmle. These drivers are used to generate a custom initramfs that is needed to boot the system. If the modules are not needed for boot but for coldplug, the modules can be loaded with systemd ; for more information, see Section 13.6.4, “Loading Kernel Modules”. Loading the Installation System When the hardware is properly recognized, the appropriate drivers are loaded. The udev program creates the special device les and linuxrc starts the installation system with the YaST installer. Starting YaST Finally, linuxrc starts YaST, which starts the package installation and the system conguration. 10.2.4 The systemd Phase After the “real” root le system has been found, it is checked for errors and mounted. If this is successful, the initramfs is cleaned and the systemd daemon on the root le system is executed. systemd is Linux''s system and service manager. It is the parent process that is started as PID 1 and acts as an init system which brings up and maintains user space services. See Chapter 13, The systemd Daemon for details. 136 The systemd Phase SLES 12 SP411 UEFI (Unified Extensible Firmware Interface) UEFI (Unied Extensible Firmware Interface) is the interface between the rmware that comes with the system hardware, all the hardware components of the system, and the operating system. UEFI is becoming more and more available on PC systems and thus is replacing the traditional PC-BIOS. UEFI, for example, properly supports 64-bit systems and oers secure booting (“Secure Boot”, rmware version 2.3.1c or better required), which is one of its most important features. Lastly, with UEFI a standard rmware will become available on all x86 platforms. UEFI additionally oers the following advantages: Booting from large disks (over 2 TiB) with a GUID Partition Table (GPT). CPU-independent architecture and drivers. Flexible pre-OS environment with network capabilities. CSM (Compatibility Support Module) to support booting legacy operating systems via a PC-BIOS-like emulation. For more information, see http://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface . The following sections are not meant as a general UEFI overview; these are only hints about how some features are implemented in SUSE Linux Enterprise Server. 11.1 Secure Boot In the world of UEFI, securing the bootstrapping process means establishing a chain of trust. The “platform” is the root of this chain of trust; in the context of SUSE Linux Enterprise Server, the mainboard and the on-board rmware could be considered the “platform”. In other words, it is the hardware vendor, and the chain of trust ows from that hardware vendor to the component manufacturers, the OS vendors, etc. The trust is expressed via public key cryptography. The hardware vendor puts a so-called Platform Key (PK) into the rmware, representing the root of trust. The trust relationship with operating system vendors and others is documented by signing their keys with the Platform Key. Finally, security is established by requiring that no code will be executed by the rmware unless it has been signed by one of these “trusted” keys—be it an OS boot loader, some driver located in the ash memory of some PCI Express card or on disk, or be it an update of the rmware itself. 137 Secure Boot SLES 12 SP4To use Secure Boot, you need to have your OS loader signed with a key trusted by the rmware, and you need the OS loader to verify that the kernel it loads can be trusted. Key Exchange Keys (KEK) can be added to the UEFI key database. This way, you can use other certicates, as long as they are signed with the private part of the PK. 11.1.1 Implementation on SUSE Linux Enterprise Server Microsoft’s Key Exchange Key (KEK) is installed by default. Note: GUID Partitioning Table (GPT) Required The Secure Boot feature is enabled by default on UEFI/x86_64 installations. You can nd the Enable Secure Boot Support option in the Boot Code Options tab of the Boot Loader Settings dialog. It supports booting when the secure boot is activated in the rmware, while making it possible to boot when it is deactivated. FIGURE 11.1: SECURE BOOT SUPPORT The Secure Boot feature requires that a GUID Partitioning Table (GPT) replaces the old partitioning with a Master Boot Record (MBR). If YaST detects EFI mode during the installation, it will try to create a GPT partition. UEFI expects to nd the EFI programs on a FAT-formatted EFI System Partition (ESP). 138 Implementation on SUSE Linux Enterprise Server SLES 12 SP4Supporting UEFI Secure Boot essentially requires having a boot loader with a digital signature that the rmware recognizes as a trusted key. That key is trusted by the rmware a priori, without requiring any manual intervention. There are two ways of getting there. One is to work with hardware vendors to have them endorse a SUSE key, which SUSE then signs the boot loader with. The other way is to go through Microsoft’s Windows Logo Certication program to have the boot loader certied and have Microsoft recognize the SUSE signing key (that is, have it signed with their KEK). By now, SUSE got the loader signed by UEFI Signing Service (that is Microsoft in this case). FIGURE 11.2: UEFI: SECURE BOOT PROCESS At the implementation layer, SUSE uses the shim loader which is installed by default. It is a smart solution that avoids legal issues, and simplies the certication and signing step considerably. The shim loader’s job is to load a boot loader such as GRUB 2 and verify it; this boot loader in turn will load kernels signed by a SUSE key only. SUSE provides this functionality since SLE11 SP3 on fresh installations with UEFI Secure Boot enabled. There are two types of trusted users: First, those who hold the keys. The Platform Key (PK) allows almost everything. The Key Exchange Key (KEK) allows all a PK can except changing the PK. Second, anyone with physical access to the machine. A user with physical access can reboot the machine, and congure UEFI. 139 Implementation on SUSE Linux Enterprise Server SLES 12 SP4UEFI oers two types of variables to fulll the needs of those users: The rst is the so-called “Authenticated Variables”, which can be updated from both within the boot process (the so-called Boot Services Environment) and the running OS. This can be done only when the new value of the variable is signed with the same key that the old value of the variable was signed with. And they can only be appended to or changed to a value with a higher serial number. The second is the so-called “Boot Services Only Variables”. These variables are accessible to any code that runs during the boot process. After the boot process ends and before the OS starts, the boot loader must call the ExitBootServices call. After that, these variables are no longer accessible, and the OS cannot touch them. The various UEFI key lists are of the rst type, as this allows online updating, adding, and blacklisting of keys, drivers, and rmware ngerprints. It is the second type of variable, the “Boot Services Only Variable”, that helps to implement Secure Boot in a secure and open source- friendly manner, and thus compatible with GPLv3. SUSE starts with shim—a small and simple EFI boot loader signed by SUSE and Microsoft. This allows shim to load and execute. shim then goes on to verify that the boot loader it wants to load is trusted. In a default situation shim will use an independent SUSE certicate embedded in its body. In addition, shim will allow to “enroll” additional keys, overriding the default SUSE key. In the following, we call them “Machine Owner Keys” or MOKs for short. Next the boot loader will verify and then boot the kernel, and the kernel will do the same on the modules. 11.1.2 MOK (Machine Owner Key) If the user (“machine owner”) wants to replace any components of the boot process, Machine Owner Keys (MOKs) are to be used. The mokutils tool will help with signing components and managing MOKs. The enrollment process begins with rebooting the machine and interrupting the boot process (for example, pressing a key) when shim loads. shim will then go into enrollment mode, allowing the user to replace the default SUSE key with keys from a le on the boot partition. If the user 140 MOK (Machine Owner Key) SLES 12 SP4chooses to do so, shim will then calculate a hash of that le and put the result in a “Boot Services Only” variable. This allows shim to detect any change of the le made outside of Boot Services and thus avoid tampering with the list of user-approved MOKs. All of this happens during boot time—only veried code is executing now. Therefore, only a user present at the console can use the machine owner''s set of keys. It cannot be malware or a hacker with remote access to the OS because hackers or malware can only change the le, but not the hash stored in the “Boot Services Only” variable. The boot loader, after having been loaded and veried by shim , will call back to shim when it wants to verify the kernel—to avoid duplication of the verication code. Shim will use the same list of MOKs for this and tell the boot loader whether it can load the kernel. This way, you can install your own kernel or boot loader. It is only necessary to install a new set of keys and authorize them by being physically present during the rst reboot. Because MOKs are a list rather than single MOK, you can make shim trust keys from several vendors, allowing dual- and multi-boot from the boot loader. 11.1.3 Booting a Custom Kernel The following is based on http://en.opensuse.org/openSUSE:UEFI#Booting_a_custom_kernel . Secure Boot does not prevent you from using a self-compiled kernel. You must sign it with your own certicate and make that certicate known to the rmware or MOK. 1. Create a custom X.509 key and certicate used for signing: openssl req -new -x509 -newkey rsa:2048 -keyout key.asc \ -out cert.pem -nodes -days 666 -subj "/CN=$USER/" For more information about creating certicates, see http://en.opensuse.org/ openSUSE:UEFI_Image_File_Sign_Tools#Create_Your_Own_Certificate . 2. Package the key and the certicate as a PKCS#12 structure: openssl pkcs12 -export -inkey key.asc -in cert.pem \ -name kernel_cert -out cert.p12 3. Generate an NSS database for use with pesign : certutil -d . -N 141 Booting a Custom Kernel SLES 12 SP44. Import the key and the certicate contained in PKCS#12 into the NSS database: pk12util -d . -i cert.p12 5. “Bless” the kernel with the new signature using pesign : pesign -n . -c kernel_cert -i arch/x86/boot/bzImage \ -o vmlinuz.signed -s 6. List the signatures on the kernel image: pesign -n . -S -i vmlinuz.signed At that point, you can install the kernel in /boot as usual. Because the kernel now has a custom signature the certicate used for signing needs to be imported into the UEFI rmware or MOK. 7. Convert the certicate to the DER format for import into the rmware or MOK: openssl x509 -in cert.pem -outform der -out cert.der 8. Copy the certicate to the ESP for easier access: sudo cp cert.der /boot/efi/ 9. Use mokutil to launch the MOK list automatically. • a. Import the certicate to MOK: mokutil --root-pw --import cert.der The --root-pw option enables usage of the root user directly. b. Check the list of certicates that are prepared to be enrolled: mokutil --list-new c. Reboot the system; shim should launch MokManager. You need to enter the root password to conrm the import of the certicate to the MOK list. d. Check if the newly imported key was enrolled: mokutil --list-enrolled 142 Booting a Custom Kernel SLES 12 SP4• a. Alternatively, this is the procedure if you want to launch MOK manually: Reboot b. In the GRUB 2 menu press the '' c '' key. c. Type: chainloader $efibootdir/MokManager.efi boot d. Select Enroll key from disk. e. Navigate to the cert.der le and press Enter . f. Follow the instructions to enroll the key. Normally this should be pressing '' 0 '' and then '' y '' to conrm. Alternatively, the rmware menu may provide ways to add a new key to the Signature Database. 11.1.4 Using Non-Inbox Drivers There is no support for adding non-inbox drivers (that is, drivers that do not come with SUSE Linux Enterprise Server) during installation with Secure Boot enabled. The signing key used for SolidDriver/PLDP is not trusted by default. It is possible to install third party drivers during installation with Secure Boot enabled in two dierent ways. In both cases: Add the needed keys to the rmware database via rmware/system management tools before the installation. This option depends on the specic hardware you are using. Consult your hardware vendor for more information. Use a bootable driver ISO from https://drivers.suse.com/ or your hardware vendor to enroll the needed keys in the MOK list at rst boot. To use the bootable driver ISO to enroll the driver keys to the MOK list, follow these steps: 1. Burn the ISO image above to an empty CD/DVD medium. 2. Start the installation using the new CD/DVD medium, having the standard installation media at hand or a URL to a network installation server. 143 Using Non-Inbox Drivers SLES 12 SP4If doing a network installation, enter the URL of the network installation source on the boot command line using the install= option. If doing installation from optical media, the installer will rst boot from the driver kit and then ask to insert the rst installation disk of the product. 3. An initrd containing updated drivers will be used for installation. For more information, see https://drivers.suse.com/doc/Usage/Secure_Boot_Certificate.html . 11.1.5 Features and Limitations When booting in Secure Boot mode, the following features apply: Installation to UEFI default boot loader location, a mechanism to keep or restore the EFI boot entry. Reboot via UEFI. Xen hypervisor will boot with UEFI when there is no legacy BIOS to fall back to. UEFI IPv6 PXE boot support. UEFI video mode support, the kernel can retrieve video mode from UEFI to congure KMS mode with the same parameters. UEFI booting from USB devices is supported. When booting in Secure Boot mode, the following limitations apply: To ensure that Secure Boot cannot be easily circumvented, some kernel features are disabled when running under Secure Boot. Boot loader, kernel, and kernel modules must be signed. Kexec and Kdump are disabled. Hibernation (suspend on disk) is disabled. Access to /dev/kmem and /dev/mem is not possible, not even as root user. Access to the I/O port is not possible, not even as root user. All X11 graphical drivers must use a kernel driver. PCI BAR access through sysfs is not possible. 144 Features and Limitations SLES 12 SP4custom_method in ACPI is not available. debugfs for asus-wmi module is not available. the acpi_rsdp parameter does not have any eect on the kernel. 11.2 For More Information https://www.uefi.org —UEFI home page where you can nd the current UEFI specications. Blog posts by Olaf Kirch and Vojtěch Pavlík (the chapter above is heavily based on these posts): https://www.suse.com/c/uefi-secure-boot-plan/ https://www.suse.com/c/uefi-secure-boot-overview/ https://www.suse.com/c/uefi-secure-boot-details/ https://en.opensuse.org/openSUSE:UEFI —UEFI with openSUSE. 145 For More Information SLES 12 SP412 The Boot Loader GRUB 2 This chapter describes how to congure GRUB 2, the boot loader used in SUSE® Linux Enterprise Server. It is the successor to the traditional GRUB boot loader —now called “GRUB Legacy”. GRUB 2 has been the default boot loader in SUSE® Linux Enterprise Server since version 12. A YaST module is available for conguring the most important settings. The boot procedure as a whole is outlined in Chapter 10, Introduction to the Boot Process. For details on Secure Boot support for UEFI machines, see Chapter 11, UEFI (Unified Extensible Firmware Interface). 12.1 Main Differences between GRUB Legacy and GRUB 2 The conguration is stored in dierent les. More le systems are supported (for example, Btrfs). Can directly read les stored on LVM or RAID devices. The user interface can be translated and altered with themes. Includes a mechanism for loading modules to support additional features, such as le systems, etc. Automatically searches for and generates boot entries for other kernels and operating systems, such as Windows. Includes a minimal Bash-like console. 12.2 Configuration File Structure The conguration of GRUB 2 is based on the following les: /boot/grub2/grub.cfg This le contains the conguration of the GRUB 2 menu items. It replaces menu.lst used in GRUB Legacy. grub.cfg should not be edited—it is automatically generated by the command grub2-mkconfig -o /boot/grub2/grub.cfg . 146 Main Differences between GRUB Legacy and GRUB 2 SLES 12 SP4/boot/grub2/custom.cfg This optional le is directly sourced by grub.cfg at boot time and can be used to add custom items to the boot menu. Starting with SUSE Linux Enterprise Server these entries will also be parsed when using grub-once . /etc/default/grub This le controls the user settings of GRUB 2 and usually includes additional environmental settings such as backgrounds and themes. Scripts under /etc/grub.d/ The scripts in this directory are read during execution of the command grub2-mkconfig -o /boot/grub2/grub.cfg . Their instructions are integrated into the main conguration le /boot/grub/grub.cfg . /etc/sysconfig/bootloader This conguration le holds some basic settings like the boot loader type or whether to enable UEFI Secure Boot support. /boot/grub2/x86_64-efi , /boot/grub2/power-ieee1275 , /boot/grub2/s390x These conguration les contain architecture-specic options. GRUB 2 can be controlled in various ways. Boot entries from an existing conguration can be selected from the graphical menu (splash screen). The conguration is loaded from the le /boot/grub2/grub.cfg which is compiled from other conguration les (see below). All GRUB 2 conguration les are considered system les, and you need root privileges to edit them. Note: Activating Configuration Changes After having manually edited GRUB  2 conguration les, you need to run grub2- mkconfig -o /boot/grub2/grub.cfg to activate the changes. However, this is not necessary when changing the conguration with YaST, because YaST will automatically run this command. 147 Configuration File Structure SLES 12 SP412.2.1 The File /boot/grub2/grub.cfg The graphical splash screen with the boot menu is based on the GRUB 2 conguration le / boot/grub2/grub.cfg , which contains information about all partitions or operating systems that can be booted by the menu. Every time the system is booted, GRUB 2 loads the menu le directly from the le system. For this reason, GRUB 2 does not need to be re-installed after changes to the conguration le. grub.cfg is automatically rebuilt with kernel installations or removals. grub.cfg is compiled from the le /etc/default/grub and scripts found in the /etc/ grub.d/ directory when running the command grub2-mkconfig -o /boot/grub2/grub.cfg . Therefore you should never edit the le manually. Instead, edit the related source les or use the YaST Boot Loader module to modify the conguration as described in Section 12.3, “Configuring the Boot Loader with YaST”. 12.2.2 The File /etc/default/grub More general options of GRUB 2 belong here, such as the time the menu is displayed, or the default OS to boot. To list all available options, see the output of the following command: grep "export GRUB_DEFAULT" -A50 /usr/sbin/grub2-mkconfig | grep GRUB_ In addition to already dened variables, the user may introduce their own variables, and use them later in the scripts found in the /etc/grub.d directory. After having edited /etc/default/grub , update the main conguration le with grub2- mkconfig -o /boot/grub2/grub.cfg . Note: Scope All options set in this le are general options that aect all boot entries. Specic options for Xen kernels or the Xen hypervisor can be set via the GRUB_*_XEN_* conguration options. See below for details. GRUB_DEFAULT Sets the boot menu entry that is booted by default. Its value can be a numeric value, the complete name of a menu entry, or “saved”. GRUB_DEFAULT=2 boots the third (counted from zero) boot menu entry. GRUB_DEFAULT="2>0" boots the rst submenu entry of the third top-level menu entry. 148 The File /boot/grub2/grub.cfg SLES 12 SP4GRUB_DEFAULT="Example boot menu entry" boots the menu entry with the title “Example boot menu entry”. GRUB_DEFAULT=saved boots the entry specied by the grub2-once or grub2-set- default commands. While grub2-reboot sets the default boot entry for the next reboot only, grub2-set-default sets the default boot entry until changed. grub2-editenv list lists the next boot entry. GRUB_HIDDEN_TIMEOUT Waits the specied number of seconds for the user to press a key. During the period no menu is shown unless the user presses a key. If no key is pressed during the time specied, the control is passed to GRUB_TIMEOUT . GRUB_HIDDEN_TIMEOUT=0 rst checks whether Shift is pressed and shows the boot menu if yes, otherwise immediately boots the default menu entry. This is the default when only one bootable OS is identied by GRUB 2. GRUB_HIDDEN_TIMEOUT_QUIET If false is specied, a countdown timer is displayed on a blank screen when the GRUB_HIDDEN_TIMEOUT feature is active. GRUB_TIMEOUT Time period in seconds the boot menu is displayed before automatically booting the default boot entry. If you press a key, the timeout is cancelled and GRUB 2 waits for you to make the selection manually. GRUB_TIMEOUT=-1 will cause the menu to be displayed until you select the boot entry manually. GRUB_CMDLINE_LINUX Entries on this line are added at the end of the boot entries for normal and recovery mode. Use it to add kernel parameters to the boot entry. GRUB_CMDLINE_LINUX_DEFAULT Same as GRUB_CMDLINE_LINUX but the entries are appended in the normal mode only. GRUB_CMDLINE_LINUX_RECOVERY Same as GRUB_CMDLINE_LINUX but the entries are appended in the recovery mode only. GRUB_CMDLINE_LINUX_XEN_REPLACE This entry will completely replace the GRUB_CMDLINE_LINUX parameters for all Xen boot entries. GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT Same as GRUB_CMDLINE_LINUX_XEN_REPLACE but it will only replace parameters of GRUB_CMDLINE_LINUX_DEFAULT . 149 The File /etc/default/grub SLES 12 SP4GRUB_CMDLINE_XEN This entry species the kernel parameters for the Xen guest kernel only—the operation principle is the same as for GRUB_CMDLINE_LINUX . GRUB_CMDLINE_XEN_DEFAULT Same as GRUB_CMDLINE_XEN—the operation principle is the same as for GRUB_CMDLINE_LINUX_DEFAULT . GRUB_TERMINAL Enables and species an input/output terminal device. Can be console (PC BIOS and EFI consoles), serial (serial terminal), ofconsole (Open Firmware console), or the default gfxterm (graphics-mode output). It is also possible to enable more than one device by quoting the required options, for example GRUB_TERMINAL="console serial" . GRUB_GFXMODE The resolution used for the gfxterm graphical terminal. Note that you can only use modes supported by your graphics card (VBE). The default is ‘auto’, which tries to select a preferred resolution. You can display the screen resolutions available to GRUB 2 by typing videoinfo in the GRUB 2 command line. The command line is accessed by typing C when the GRUB 2 boot menu screen is displayed. You can also specify a color depth by appending it to the resolution setting, for example GRUB_GFXMODE=1280x1024x24 . GRUB_BACKGROUND Set a background image for the gfxterm graphical terminal. The image must be a le readable by GRUB 2 at boot time, and it must end with the .png , .tga , .jpg , or .jpeg sux. If necessary, the image will be scaled to t the screen. GRUB_DISABLE_OS_PROBER If this option is set to true , automatic searching for other operating systems is disabled. Only the kernel images in /boot/ and the options from your own scripts in /etc/grub.d/ are detected. SUSE_BTRFS_SNAPSHOT_BOOTING If this option is set to true , GRUB 2 can boot directly into Snapper snapshots. For more information, see Section 7.3, “System Rollback by Booting from Snapshots”. For a complete list of options, see the GNU GRUB manual (http://www.gnu.org/software/grub/ manual/grub.html#Simple-configuration) . For a complete list of possible parameters, see http:// en.opensuse.org/Linuxrc . 150 The File /etc/default/grub SLES 12 SP412.2.3 Scripts in /etc/grub.d The scripts in this directory are read during execution of the command grub2-mkconfig - o /boot/grub2/grub.cfg . Their instructions are incorporated into /boot/grub2/grub.cfg . The order of menu items in grub.cfg is determined by the order in which the les in this directory are run. Files with a leading numeral are executed rst, beginning with the lowest number. 00_header is run before 10_linux , which would run before 40_custom . If les with alphabetic names are present, they are executed after the numerically-named les. Only executable les generate output to grub.cfg during execution of grub2-mkconfig . By default all les in the /etc/grub.d directory are executable. Tip: Persistent Custom Content in grub.cfg Because /boot/grub2/grub.cfg is recompiled each time grub2-mkconfig is run, any custom content is lost. If you want to insert your lines directly into /boot/grub2/ grub.cfg without losing them after grub2-mkconfig is run, insert them between the ### BEGIN /etc/grub.d/90_persistent ### and ### END /etc/grub.d/90_persistent ### lines. The 90_persistent script ensures that such content will be preserved. A list of the most important scripts follows: 00_header Sets environmental variables such as system le locations, display settings, themes, and previously saved entries. It also imports preferences stored in the /etc/default/grub . Normally you do not need to make changes to this le. 10_linux Identies Linux kernels on the root device and creates relevant menu entries. This includes the associated recovery mode option if enabled. Only the latest kernel is displayed on the main menu page, with additional kernels included in a submenu. 30_os-prober 151 Scripts in /etc/grub.d SLES 12 SP4This script uses OS-prober to search for Linux and other operating systems and places the results in the GRUB 2 menu. There are sections to identify specic other operating systems, such as Windows or macOS. 40_custom This le provides a simple way to include custom boot entries into grub.cfg . Make sure that you do not change the exec tail -n +3 $0 part at the beginning. The processing sequence is set by the preceding numbers with the lowest number being executed rst. If scripts are preceded by the same number the alphabetical order of the complete name decides the order. Tip: /boot/grub2/custom.cfg If you create /boot/grub2/custom.cfg and ll it with content, it will be automatically included into /boot/grub2/grub.cfg just after 40_custom at boot time. 12.2.4 Mapping between BIOS Drives and Linux Devices In GRUB Legacy, the device.map conguration le was used to derive Linux device names from BIOS drive numbers. The mapping between BIOS drives and Linux devices cannot always be guessed correctly. For example, GRUB Legacy would get a wrong order if the boot sequence of IDE and SCSI drives is exchanged in the BIOS conguration. GRUB 2 avoids this problem by using device ID strings (UUIDs) or le system labels when generating grub.cfg . GRUB 2 utilities create a temporary device map on the y, which is usually sucient, particularly in the case of single-disk systems. However, if you need to override the GRUB 2''s automatic device mapping mechanism, create your custom mapping le /boot/grub2/device.map . The following example changes the mapping to make DISK 3 the boot disk. Note that GRUB 2 partition numbers start with 1 and not with 0 as in GRUB Legacy. (hd1) /dev/disk-by-id/DISK3 ID (hd2) /dev/disk-by-id/DISK1 ID (hd3) /dev/disk-by-id/DISK2 ID 152 Mapping between BIOS Drives and Linux Devices SLES 12 SP412.2.5 Editing Menu Entries during the Boot Procedure Being able to directly edit menu entries is useful when the system does not boot anymore because of a faulty conguration. It can also be used to test new settings without altering the system conguration. 1. In the graphical boot menu, select the entry you want to edit with the arrow keys. 2. Press E to open the text-based editor. 3. Use the arrow keys to move to the line you want to edit. FIGURE 12.1: GRUB 2 BOOT EDITOR Now you have two options: a. Add space-separated parameters to the end of the line starting with linux or linuxefi to edit the kernel parameters. A complete list of parameters is available at http://en.opensuse.org/Linuxrc . b. Or edit the general options to change for example the kernel version. The →| key suggests all possible completions. 4. Press F10 to boot the system with the changes you made or press Esc to discard your edits and return to the GRUB 2 menu. 153 Editing Menu Entries during the Boot Procedure SLES 12 SP4Changes made this way only apply to the current boot process and are not saved permanently. Important: Keyboard Layout During the Boot Procedure The US keyboard layout is the only one available when booting. See Figure  41.2, “US Keyboard Layout”. Note: Boot Loader on the Installation Media The Boot Loader of the installation media on systems with a traditional BIOS is still GRUB Legacy. To add boot options, select an entry and start typing. Additions you make to the installation boot entry will be permanently saved in the installed system. Note: Editing GRUB 2 Menu Entries on z Systems Cursor movement and editing commands on IBM z  Systems dier—see Section  12.4, “Differences in Terminal Usage on z Systems” for details. 12.2.6 Setting a Boot Password Even before the operating system is booted, GRUB 2 enables access to le systems. Users without root permissions can access les in your Linux system to which they have no access after the system is booted. To block this kind of access or to prevent users from booting certain menu entries, set a boot password. Important: Booting Requires Password If set, the boot password is required on every boot, which means the system does not boot automatically. Proceed as follows to set a boot password. Alternatively use YaST (Protect Boot Loader with Password ). 1. Encrypt the password using grub2-mkpasswd-pbkdf2: tux > sudo grub2-mkpasswd-pbkdf2 154 Setting a Boot Password SLES 12 SP4Password: **** Reenter password: **** PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A... 2. Paste the resulting string into the le /etc/grub.d/40_custom together with the set superusers command. set superusers="root" password_pbkdf2 root grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A... 3. To import the changes into the main conguration le, run: tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg After you reboot, you will be prompted for a user name and a password when trying to boot a menu entry. Enter root and the password you typed during the grub2-mkpasswd-pbkdf2 command. If the credentials are correct, the system will boot the selected boot entry. For more information, see https://www.gnu.org/software/grub/manual/grub.html#Security . 12.3 Configuring the Boot Loader with YaST The easiest way to congure general options of the boot loader in your SUSE Linux Enterprise Server system is to use the YaST module. In the YaST Control Center, select System Boot Loader. The module shows the current boot loader conguration of your system and allows you to make changes. Use the Boot Code Options tab to view and change settings related to type, location and advanced loader settings. You can choose whether to use GRUB 2 in standard or EFI mode. 155 Configuring the Boot Loader with YaST SLES 12 SP4FIGURE 12.2: BOOT CODE OPTIONS Important: EFI Systems require GRUB2-EFI If you have an EFI system you can only install GRUB2-EFI, otherwise your system is no longer bootable. Important: Reinstalling the Boot Loader To reinstall the boot loader, make sure to change a setting in YaST and then change it back. For example, to reinstall GRUB2-EFI, select GRUB2 rst and then immediately switch back to GRUB2-EFI. Otherwise, the boot loader may only be partially reinstalled. Note: Custom Boot Loader To use a boot loader other than the ones listed, select Do Not Install Any Boot Loader. Read the documentation of your boot loader carefully before choosing this option. 156 Configuring the Boot Loader with YaST SLES 12 SP412.3.1 Boot Loader Location and Boot Code Options The default location of the boot loader depends on the partition setup and is either the Master Boot Record (MBR) or the boot sector of the / partition. To modify the location of the boot loader, follow these steps: PROCEDURE 12.1: CHANGING THE BOOT LOADER LOCATION 1. Select the Boot Code Options tab and then choose one of the following options for Boot Loader Location: Boot from Master Boot Record This installs the boot loader in the MBR of the disk containing the directory /boot . Usually this will be the disk mounted to / , but if /boot is mounted to a separate partition on a dierent disk, the MBR of that disk will be used. Boot from Root Partition This installs the boot loader in the boot sector of the / partition. Custom Boot Partition Use this option to specify the location of the boot loader manually. 2. Click OK to apply your changes. FIGURE 12.3: CODE OPTIONS 157 Boot Loader Location and Boot Code Options SLES 12 SP4The Boot Code Options tab includes the following additional options: Set Active Flag in Partition Table for Boot Partition Activates the partition that contains the /boot directorythe PReP partition. Use this option on systems with old BIOS and/or legacy operating systems because they may fail to boot from a non-active partition. It is safe to leave this option active. Write Generic Boot Code to MBR If MBR contains a custom ''non-GRUB'' code, this option replaces it with a generic, operating system independent code. If you deactivate this option, the system may become unbootable. Enable Trusted Boot Support Starts TrustedGRUB2, which supports trusted computing functionality (Trusted Platform Module (TPM)). For more information refer to https://github.com/Sirrix-AG/ TrustedGRUB2 . 12.3.2 Adjusting the Disk Order If your computer has more than one hard disk, you can specify the boot sequence of the disks. The rst disk in the list is where GRUB 2 will be installed in the case of booting from MBR. It is the disk where SUSE Linux Enterprise Server is installed by default. The rest of the list is a hint for GRUB 2''s device mapper (see Section 12.2.4, “Mapping between BIOS Drives and Linux Devices”). Warning: Unbootable System The default value is usually valid for almost all deployments. If you change the boot order of disks wrongly, the system may become unbootable on the next reboot. For example, if the rst disk in the list is not part of the BIOS boot order, and the other disks in the list have empty MBRs. PROCEDURE 12.2: SETTING THE DISK ORDER 1. Open the Boot Code Options tab. 2. Click Edit Disk Boot Order. 3. If more than one disk is listed, select a disk and click Up or Down to reorder the displayed disks. 158 Adjusting the Disk Order SLES 12 SP44. Click OK two times to save the changes. 12.3.3 Configuring Advanced Options Advanced boot options can be congured via the Boot Loader Options tab. 12.3.3.1 Boot Loader Options Tab FIGURE 12.4: BOOT LOADER OPTIONS Boot Loader Time-Out Change the value of Time-Out in Seconds by typing in a new value and clicking the appropriate arrow key with your mouse. Probe Foreign OS When selected, the boot loader searches for other systems like Windows or other Linux installations. Hide Menu on Boot Hides the boot menu and boots the default entry. Adjusting the Default Boot Entry 159 Configuring Advanced Options SLES 12 SP4Select the desired entry from the “Default Boot Section” list. Note that the “>” sign in the boot entry name delimits the boot section and its subsection. Protect Boot Loader with Password Protects the boot loader and the system with an additional password. For more information, see Section 12.2.6, “Setting a Boot Password”. 12.3.3.2 Kernel Parameters Tab FIGURE 12.5: KERNEL PARAMETERS Console resolution The Console resolution option species the default screen resolution during the boot process. Kernel Command Line Parameter The optional kernel parameters are added at the end of the default parameters. For a list of all possible parameters, see http://en.opensuse.org/Linuxrc . Use graphical console When checked, the boot menu appears on a graphical splash screen rather than in a text mode. The resolution of the boot screen can be then set from the Console resolution list, and graphical theme denition le can be specied with the Console theme le-chooser. 160 Configuring Advanced Options SLES 12 SP4Use Serial Console If your machine is controlled via a serial console, activate this option and specify which COM port to use at which speed. See info grub or http://www.gnu.org/software/grub/ manual/grub.html#Serial-terminal 12.4 Differences in Terminal Usage on z Systems On 3215 and 3270 terminals there are some dierences and limitations on how to move the cursor and how to issue editing commands within GRUB 2. 12.4.1 Limitations Interactivity Interactivity is strongly limited. Typing often does not result in visual feedback. To see where the cursor is, type an underscore ( _ ). Note: 3270 Compared to 3215 The 3270 terminal is much better at displaying and refreshing screens than the 3215 terminal. Cursor Movement “Traditional” cursor movement is not possible. Alt , Meta , Ctrl and the cursor keys do not work. To move the cursor, use the key combinations listed in Section 12.4.2, “Key Combinations”. Caret The caret ( ^ ) is used as a control character. To type a literal ^ followed by a letter, type ^ , ^ , LETTER . Enter The Enter key does not work, use ^ – J instead. 161 Differences in Terminal Usage on z Systems SLES 12 SP412.4.2 Key Combinations Common Substitutes: ^ – J engage (“Enter”) ^ – L abort, return to previous “state” ^ – I tab completion (in edit and shell mode) Keys Available in Menu ^ – A rst entry Mode: ^ – E last entry ^ – P previous entry ^ – N next entry ^ – G previous page ^ – C next page ^ – F boot selected entry or enter submenu (same as ^ – J ) E edit selected entry C enter GRUB-Shell Keys Available in Edit Mode: ^ – P previous line ^ – N next line ^ – B backward char ^ – F forward char ^ – A beginning of line ^ – E end of line 162 Key Combinations SLES 12 SP4^ – H backspace ^ – D delete ^ – K kill line ^ – Y yank ^ – O open line ^ – L refresh screen ^ – X boot entry ^ – C enter GRUB-Shell Keys Available in Command ^ – P previous command Line Mode: ^ – N next command from history ^ – A beginning of line ^ – E end of line ^ – B backward char ^ – F forward char ^ – H backspace ^ – D delete ^ – K kill line ^ – U discard line ^ – Y yank 163 Key Combinations SLES 12 SP412.5 Helpful GRUB 2 Commands grub2-mkconfig Generates a new /boot/grub2/grub.cfg based on /etc/default/grub and the scripts from /etc/grub.d/ . EXAMPLE 12.1: USAGE OF GRUB2-MKCONFIG grub2-mkconfig -o /boot/grub2/grub.cfg Tip: Syntax Check Running grub2-mkconfig without any parameters prints the conguration to STDOUT where it can be reviewed. Use grub2-script-check after /boot/grub2/ grub.cfg has been written to check its syntax. Important: grub2-mkconfig Cannot Repair UEFI Secure Boot Tables If you are using UEFI Secure Boot and your system is not reaching GRUB 2 correctly anymore, you may need to additionally reinstall Shim and regenerate the UEFI boot table. To do so, use: root # shim-install --config-file=/boot/grub2/grub.cfg grub2-mkrescue Creates a bootable rescue image of your installed GRUB 2 conguration. EXAMPLE 12.2: USAGE OF GRUB2-MKRESCUE grub2-mkrescue -o save_path/name.iso iso grub2-script-check Checks the given le for syntax errors. EXAMPLE 12.3: USAGE OF GRUB2-SCRIPT-CHECK grub2-script-check /boot/grub2/grub.cfg grub2-once 164 Helpful GRUB 2 Commands SLES 12 SP4Set the default boot entry for the next boot only. To get the list of available boot entries use the --list option. EXAMPLE 12.4: USAGE OF GRUB2-ONCE grub2-once number_of_the_boot_entry Tip: grub2-once Help Call the program without any option to get a full list of all possible options. 12.6 More Information Extensive information about GRUB 2 is available at https://www.gnu.org/software/grub/ . Also refer to the grub info page. You can also search for the keyword “GRUB 2” in the Technical Information Search at https://www.suse.com/support to get information about special issues. 165 More Information SLES 12 SP413 The systemd Daemon The program systemd is the process with process ID 1. It is responsible for initializing the system in the required way. systemd is started directly by the kernel and resists signal 9, which normally terminates processes. All other programs are either started directly by systemd or by one of its child processes. Starting with SUSE Linux Enterprise Server 12 systemd is a replacement for the popular System V init daemon. systemd is fully compatible with System V init (by supporting init scripts). One of the main advantages of systemd is that it considerably speeds up boot time by aggressively paralleling service starts. Furthermore, systemd only starts a service when it is really needed. Daemons are not started unconditionally at boot time, but rather when being required for the rst time. systemd also supports Kernel Control Groups (cgroups), snapshotting and restoring the system state and more. See http://www.freedesktop.org/wiki/Software/systemd/ for details. 13.1 The systemd Concept This section will go into detail about the concept behind systemd. 13.1.1 What Is systemd systemd is a system and session manager for Linux, compatible with System V and LSB init scripts. The main features are: provides aggressive parallelization capabilities uses socket and D-Bus activation for starting services oers on-demand starting of daemons keeps track of processes using Linux cgroups supports snapshotting and restoring of the system state maintains mount and automount points implements an elaborate transactional dependency-based service control logic 166 The systemd Concept SLES 12 SP413.1.2 Unit File A unit conguration le contains information about a service, a socket, a device, a mount point, an automount point, a swap le or partition, a start-up target, a watched le system path, a timer controlled and supervised by systemd, a temporary system state snapshot, a resource management slice or a group of externally created processes. “Unit le” is a generic term used by systemd for the following: Service. Information about a process (for example running a daemon); le ends with .service Targets. Used for grouping units and as synchronization points during start-up; le ends with .target Sockets. Information about an IPC or network socket or a le system FIFO, for socket- based activation (like inetd ); le ends with .socket Path. Used to trigger other units (for example running a service when les change); le ends with .path Timer. Information about a timer controlled, for timer-based activation; le ends with .timer Mount point. Usually auto-generated by the fstab generator; le ends with .mount Automount point. Information about a le system automount point; le ends with .automount Swap. Information about a swap device or le for memory paging; le ends with .swap Device. Information about a device unit as exposed in the sysfs/udev(7) device tree; le ends with .device Scope / Slice. A concept for hierarchically managing resources of a group of processes; le ends with .scope/.slice For more information about systemd.unit see http://www.freedesktop.org/software/systemd/ man/systemd.unit.html 167 Unit File SLES 12 SP413.2 Basic Usage The System V init system uses several commands to handle services—the init scripts, insserv , telinit and others. systemd makes it easier to manage services, since there is only one command to memorize for the majority of service-handling tasks: systemctl . It uses the “command plus subcommand” notation like git or zypper : systemctl GENERAL OPTIONS SUBCOMMAND SUBCOMMAND OPTIONS See man 1 systemctl for a complete manual. Tip: Terminal Output and Bash Completion If the output goes to a terminal (and not to a pipe or a le, for example) systemd commands send long output to a pager by default. Use the --no-pager option to turn o paging mode. systemd also supports bash-completion, allowing you to enter the rst letters of a subcommand and then press →| to automatically complete it. This feature is only available in the bash shell and requires the installation of the package bash- completion . 13.2.1 Managing Services in a Running System Subcommands for managing services are the same as for managing a service with System V init ( start , stop , ...). The general syntax for service management commands is as follows: systemd systemctl reload|restart|start|status|stop|... MY_SERVICE(S) System V init rcMY_SERVICE(S) reload|restart|start|status|stop|... systemd allows you to manage several services in one go. Instead of executing init scripts one after the other as with System V init, execute a command like the following: systemctl start MY_1ST_SERVICE MY_2ND_SERVICE 168 Basic Usage SLES 12 SP4To list all services available on the system: systemctl list-unit-files --type=service The following table lists the most important service management commands for systemd and System V init: TABLE 13.1: SERVICE MANAGEMENT COMMANDS Task systemd Command System V init Command Starting. start start Stopping. stop stop Restarting. Shuts down services and starts restart restart them afterward. If a service is not yet running it will be started. Restarting conditionally. Restarts services if try-restart try-restart they are currently running. Does nothing for services that are not running. Reloading. Tells services to reload their reload reload conguration les without interrupting operation. Use case: Tell Apache to reload a modied httpd.conf conguration le. Note that not all services support reloading. Reloading or restarting. Reloads services reload-or-restart n/a if reloading is supported, otherwise restarts them. If a service is not yet running it will be started. Reloading or restarting conditionally. reload-or-try-restart n/a Reloads services if reloading is supported, otherwise restarts them if currently running. Does nothing for services that are not running. 169 Managing Services in a Running System SLES 12 SP4Task systemd Command System V init Command Getting detailed status information. Lists status status information about the status of services. The systemd command shows details such as description, executable, status, cgroup, and messages last issued by a service (see Section 13.6.8, “Debugging Services”). The level of details displayed with the System V init diers from service to service. Getting short status information. Shows is-active status whether services are active or not. 13.2.2 Permanently Enabling/Disabling Services The service management commands mentioned in the previous section let you manipulate services for the current session. systemd also lets you permanently enable or disable services, so they are automatically started when requested or are always unavailable. You can either do this by using YaST, or on the command line. 13.2.2.1 Enabling/Disabling Services on the Command Line The following table lists enabling and disabling commands for systemd and System V init: Important: Service Start When enabling a service on the command line, it is not started automatically. It is scheduled to be started with the next system start-up or runlevel/target change. To immediately start a service after having enabled it, explicitly run systemctl start MY_SERVICE or rc MY_SERVICE start . 170 Permanently Enabling/Disabling Services SLES 12 SP4TABLE 13.2: COMMANDS FOR ENABLING AND DISABLING SERVICES Task systemd Command System V init Command Enabling. systemctl enable insserv MY_SERVICE(S) MY_SERVICE(S) , chkconfig -a MY_SERVICE(S) Disabling. systemctl disable insserv -r MY_SERVICE(S).service MY_SERVICE(S) , chkconfig -d MY_SERVICE(S) Checking. Shows whether a systemctl is-enabled chkconfig service is enabled or not. MY_SERVICE MY_SERVICE Re-enabling. Similar to systemctl reenable n/a restarting a service, this MY_SERVICE command rst disables and then enables a service. Useful to re-enable a service with its defaults. Masking. After “disabling” systemctl mask MY_SERVICE n/a a service, it can still be started manually. To completely disable a service, you need to mask it. Use with care. Unmasking. A service that systemctl unmask MY_SERVICE n/a has been masked can only be used again after it has been unmasked. 171 Permanently Enabling/Disabling Services SLES 12 SP413.3 System Start and Target Management The entire process of starting the system and shutting it down is maintained by systemd. From this point of view, the kernel can be considered a background process to maintain all other processes and adjust CPU time and hardware access according to requests from other programs. 13.3.1 Targets Compared to Runlevels With System V init the system was booted into a so-called “Runlevel”. A runlevel denes how the system is started and what services are available in the running system. Runlevels are numbered; the most commonly known ones are 0 (shutting down the system), 3 (multiuser with network) and 5 (multiuser with network and display manager). systemd introduces a new concept by using so-called “target units”. However, it remains fully compatible with the runlevel concept. Target units are named rather than numbered and serve specic purposes. For example, the targets local-fs.target and swap.target mount local le systems and swap spaces. The target graphical.target provides a multiuser system with network and display manager capabilities and is equivalent to runlevel 5. Complex targets, such as graphical.target act as “meta” targets by combining a subset of other targets. Since systemd makes it easy to create custom targets by combining existing targets, it oers great exibility. The following list shows the most important systemd target units. For a full list refer to man 7 systemd.special . SELECTED SYSTEMD TARGET UNITS default.target The target that is booted by default. Not a “real” target, but rather a symbolic link to another target like graphic.target . Can be permanently changed via YaST (see Section  13.4, “Managing Services with YaST”). To change it for a session, use the kernel parameter systemd.unit=MY_TARGET.target at the boot prompt. emergency.target Starts an emergency shell on the console. Only use it at the boot prompt as systemd.unit=emergency.target . graphical.target Starts a system with network, multiuser support and a display manager. 172 System Start and Target Management SLES 12 SP4halt.target Shuts down the system. mail-transfer-agent.target Starts all services necessary for sending and receiving mails. multi-user.target Starts a multiuser system with network. reboot.target Reboots the system. rescue.target Starts a single-user system without network. To remain compatible with the System V init runlevel system, systemd provides special targets named runlevelX.target mapping the corresponding runlevels numbered X . If you want to know the current target, use the command: systemctl get-default TABLE 13.3: SYSTEM V RUNLEVELS AND systemd TARGET UNITS System V systemd target Purpose runlevel 0 runlevel0.target , System shutdown halt.target , poweroff.target 1, S runlevel1.target , Single-user mode rescue.target , 2 runlevel2.target , multi- Local multiuser without remote user.target , network 3 runlevel3.target , multi- Full multiuser with network user.target , 4 runlevel4.target Unused/User-dened 5 runlevel5.target , Full multiuser with network and graphical.target , display manager 173 Targets Compared to Runlevels SLES 12 SP4System V systemd target Purpose runlevel 6 runlevel6.target , System reboot reboot.target , Important: systemd Ignores /etc/inittab The runlevels in a System V init system are congured in /etc/inittab . systemd does not use this conguration. Refer to Section 13.5.3, “Creating Custom Targets” for instructions on how to create your own bootable target. 13.3.1.1 Commands to Change Targets Use the following commands to operate with target units: Task systemd Command System V init Command Change the systemctl isolate MY_TARGET .target telinit X current target/ runlevel Change to the systemctl default n/a default target/ runlevel Get the current systemctl list-units --type=target who -r target/runlevel With systemd there is usually more than one or active target. The command lists all currently runlevel active targets. persistently Use the Services Manager or run the Use the Services Manager change the following command: or change the line default runlevel ln -sf /usr/lib/systemd/system/ id: X :initdefault: MY_TARGET .target /etc/systemd/system/ in /etc/inittab default.target 174 Targets Compared to Runlevels SLES 12 SP4Task systemd Command System V init Command Change the Enter the following option at the boot Enter the desired runlevel default runlevel prompt number at the boot for the current systemd.unit= MY_TARGET .target prompt. boot process Show a target''s/ systemctl show -p "Requires" n/a runlevel''s MY_TARGET .target dependencies systemctl show -p "Wants" MY_TARGET .target “Requires” lists the hard dependencies (the ones that must be resolved), whereas “Wants” lists the soft dependencies (the ones that get resolved if possible). 13.3.2 Debugging System Start-Up systemd oers the means to analyze the system start-up process. You can review the list of all services and their status (rather than having to parse /varlog/ ). systemd also allows you to scan the start-up procedure to nd out how much time each service start-up consumes. 13.3.2.1 Review Start-Up of Services To review the complete list of services that have been started since booting the system, enter the command systemctl . It lists all active services like shown below (shortened). To get more information on a specic service, use systemctl status MY_SERVICE . EXAMPLE 13.1: LIST ACTIVE SERVICES root # systemctl UNIT LOAD ACTIVE SUB JOB DESCRIPTION [...] iscsi.service loaded active exited Login and scanning of iSC+ kmod-static-nodes.service loaded active exited Create list of required s+ libvirtd.service loaded active running Virtualization daemon nscd.service loaded active running Name Service Cache Daemon 175 Debugging System Start-Up SLES 12 SP4ntpd.service loaded active running NTP Server Daemon polkit.service loaded active running Authorization Manager postfix.service loaded active running Postfix Mail Transport Ag+ rc-local.service loaded active exited /etc/init.d/boot.local Co+ rsyslog.service loaded active running System Logging Service [...] LOAD = Reflects whether the unit definition was properly loaded. ACTIVE = The high-level unit activation state, i.e. generalization of SUB. SUB = The low-level unit activation state, values depend on unit type. 161 loaded units listed. Pass --all to see loaded but inactive units, too. To show all installed unit files use ''systemctl list-unit-files''. To restrict the output to services that failed to start, use the --failed option: EXAMPLE 13.2: LIST FAILED SERVICES root # systemctl --failed UNIT LOAD ACTIVE SUB JOB DESCRIPTION apache2.service loaded failed failed apache NetworkManager.service loaded failed failed Network Manager plymouth-start.service loaded failed failed Show Plymouth Boot Screen [...] 13.3.2.2 Debug Start-Up Time To debug system start-up time, systemd oers the systemd-analyze command. It shows the total start-up time, a list of services ordered by start-up time and can also generate an SVG graphic showing the time services took to start in relation to the other services. Listing the System Start-Up Time root # systemd-analyze Startup finished in 2666ms (kernel) + 21961ms (userspace) = 24628ms Listing the Services Start-Up Time root # systemd-analyze blame 6472ms systemd-modules-load.service 5833ms remount-rootfs.service 4597ms network.service 176 Debugging System Start-Up SLES 12 SP44254ms systemd-vconsole-setup.service 4096ms postfix.service 2998ms xdm.service 2483ms localnet.service 2470ms SuSEfirewall2_init.service 2189ms avahi-daemon.service 2120ms systemd-logind.service 1210ms xinetd.service 1080ms ntp.service [...] 75ms fbset.service 72ms purge-kernels.service 47ms dev-vda1.swap 38ms bluez-coldplug.service 35ms splash_early.service Services Start-Up Time Graphics root # systemd-analyze plot > jupiter.example.com-startup.svg 177 Debugging System Start-Up SLES 12 SP413.3.2.3 Review the Complete Start-Up Process The above-mentioned commands let you review the services that started and the time it took to start them. If you need to know more details, you can tell systemd to verbosely log the complete start-up procedure by entering the following parameters at the boot prompt: systemd.log_level=debug systemd.log_target=kmsg Now systemd writes its log messages into the kernel ring buer. View that buer with dmesg : dmesg -T | less 13.3.3 System V Compatibility systemd is compatible with System V, allowing you to still use existing System V init scripts. However, there is at least one known issue where a System V init script does not work with systemd out of the box: starting a service as a dierent user via su or sudo in init scripts will result in a failure of the script, producing an “Access denied” error. When changing the user with su or sudo , a PAM session is started. This session will be terminated after the init script is nished. As a consequence, the service that has been started by the init script will also be terminated. To work around this error, proceed as follows: 1. Create a service le wrapper with the same name as the init script plus the le name extension .service : [Unit] Description=DESCRIPTION After=network.target [Service] User=USER Type=forking 1 PIDFile=PATH TO PID FILE 1 ExecStart=PATH TO INIT SCRIPT start ExecStop=PATH TO INIT SCRIPT stop ExecStopPost=/usr/bin/rm -f PATH TO PID FILE 1 [Install] WantedBy=multi-user.target 2 Replace all values written in UPPERCASE LETTERS with appropriate values. 1 Optional—only use if the init script starts a daemon. 178 System V Compatibility SLES 12 SP42 multi-user.target also starts the init script when booting into graphical.target . If it should only be started when booting into the display manager, user graphical.target here. 2. Start the daemon with systemctl start APPLICATION . 13.4 Managing Services with YaST Basic service management can also be done with the YaST Services Manager module. It supports starting, stopping, enabling and disabling services. It also lets you show a service''s status and change the default target. Start the YaST module with YaST System Services Manager. FIGURE 13.1: SERVICES MANAGER Changing the Default System Target To change the target the system boots into, choose a target from the Default System Target drop-down box. The most often used targets are Graphical Interface (starting a graphical login screen) and Multi-User (starting the system in command line mode). Starting or Stopping a Service Select a service from the table. The Active column shows whether it is currently running (Active) or not (Inactive). Toggle its status by choosing Start/Stop. 179 Managing Services with YaST SLES 12 SP4Starting or stopping a service changes its status for the currently running session. To change its status throughout a reboot, you need to enable or disable it. Enabling or Disabling a Service Select a service from the table. The Enabled column shows whether it is currently Enabled or Disabled. Toggle its status by choosing Enable/Disable. By enabling or disabling a service you congure whether it is started during booting (Enabled) or not (Disabled). This setting will not aect the current session. To change its status in the current session, you need to start or stop it. View a Status Messages To view the status message of a service, select it from the list and choose Show Details. The output you will see is identical to the one generated by the command systemctl - l status MY_SERVICE . Warning: Faulty Runlevel Settings May Damage Your System Faulty runlevel settings may make your system unusable. Before applying your changes, make absolutely sure that you know their consequences. 13.5 Customization of systemd The following sections contain some examples for systemd customization. Warning: Avoiding Overwritten Customization Always do systemd customization in /etc/systemd/ , never in /usr/lib/systemd/ . Otherwise your changes will be overwritten by the next update of systemd. 13.5.1 Customizing Service Files The systemd service les are located in /usr/lib/systemd/system . If you want to customize them, proceed as follows: 1. Copy the les you want to modify from /usr/lib/systemd/system to /etc/systemd/ system . Keep the le names identical to the original ones. 2. Modify the copies in /etc/systemd/system according to your needs. 180 Customization of systemd SLES 12 SP43. For an overview of your conguration changes, use the systemd-delta command. It can compare and identify conguration les that override other conguration les. For details, refer to the systemd-delta man page. The modied les in /etc/systemd will take precedence over the original les in /usr/lib/ systemd/system , provided that their le name is the same. 13.5.2 Creating “Drop-in” Files If you only want to add a few lines to a conguration le or modify a small part of it, you can use so-called “drop-in” les. Drop-in les let you extend the conguration of unit les without having to edit or override the unit les themselves. For example, to change one value for the FOOBAR service located in /usr/lib/systemd/ system/FOOBAR.SERVICE , proceed as follows: 1. Create a directory called /etc/systemd/system/MY_SERVICE.service.d/ . Note the .d sux. The directory must otherwise be named like the service that you want to patch with the drop-in le. 2. In that directory, create a le WHATEVERMODIFICATION.conf . Make sure it only contains the line with the value that you want to modify. 3. Save your changes to the le. It will be used as an extension of the original le. 13.5.3 Creating Custom Targets On System V init SUSE systems, runlevel 4 is unused to allow administrators to create their own runlevel conguration. systemd allows you to create any number of custom targets. It is suggested to start by adapting an existing target such as graphical.target . 1. Copy the conguration le /usr/lib/systemd/system/graphical.target to /etc/ systemd/system/MY_TARGET.target and adjust it according to your needs. 2. The conguration le copied in the previous step already covers the required (“hard”) dependencies for the target. To also cover the wanted (“soft”) dependencies, create a directory /etc/systemd/system/MY_TARGET.target.wants . 3. For each wanted service, create a symbolic link from /usr/lib/systemd/system into / etc/systemd/system/MY_TARGET.target.wants . 181 Creating “Drop-in” Files SLES 12 SP44. Once you have nished setting up the target, reload the systemd conguration to make the new target available: systemctl daemon-reload 13.6 Advanced Usage The following sections cover advanced topics for system administrators. For even more advanced systemd documentation, refer to Lennart Pöttering''s series about systemd for administrators at http://0pointer.de/blog/projects . 13.6.1 Cleaning Temporary Directories systemd supports cleaning temporary directories regularly. The conguration from the previous system version is automatically migrated and active. tmpfiles.d—which is responsible for managing temporary les—reads its conguration from /etc/tmpfiles.d/ *.conf , /run/tmpfiles.d/*.conf , and /usr/lib/tmpfiles.d/*.conf les. Conguration placed in /etc/tmpfiles.d/*.conf overrides related congurations from the other two directories ( /usr/lib/tmpfiles.d/*.conf is where packages store their conguration les). The conguration format is one line per path containing action and path, and optionally mode, ownership, age and argument elds, depending on the action. The following example unlinks the X11 lock les: Type Path Mode UID GID Age Argument r /tmp/.X[0-9]*-lock To get the status the tmple timer: systemctl status systemd-tmpfiles-clean.timer systemd-tmpfiles-clean.timer - Daily Cleanup of Temporary Directories Loaded: loaded (/usr/lib/systemd/system/systemd-tmpfiles-clean.timer; static) Active: active (waiting) since Tue 2014-09-09 15:30:36 CEST; 1 weeks 6 days ago Docs: man:tmpfiles.d(5) man:systemd-tmpfiles(8) Sep 09 15:30:36 jupiter systemd[1]: Starting Daily Cleanup of Temporary Directories. Sep 09 15:30:36 jupiter systemd[1]: Started Daily Cleanup of Temporary Directories. For more information on temporary les handling, see man 5 tmpfiles.d . 182 Advanced Usage SLES 12 SP413.6.2 System Log Section  13.6.8, “Debugging Services” explains how to view log messages for a given service. However, displaying log messages is not restricted to service logs. You can also access and query the complete log messages written by systemd—the so-called “Journal”. Use the command journalctl to display the complete log messages starting with the oldest entries. Refer to man 1 journalctl for options such as applying lters or changing the output format. 13.6.3 Snapshots You can save the current state of systemd to a named snapshot and later revert to it with the isolate subcommand. This is useful when testing services or custom targets, because it allows you to return to a dened state at any time. A snapshot is only available in the current session and will automatically be deleted on reboot. A snapshot name must end in .snapshot . Create a Snapshot systemctl snapshot MY_SNAPSHOT.snapshot Delete a Snapshot systemctl delete MY_SNAPSHOT.snapshot View a Snapshot systemctl show MY_SNAPSHOT.snapshot Activate a Snapshot systemctl isolate MY_SNAPSHOT.snapshot 13.6.4 Loading Kernel Modules With systemd , kernel modules can automatically be loaded at boot time via a conguration le in /etc/modules-load.d . The le should be named MODULE .conf and have the following content: # load module MODULE at boot time MODULE 183 System Log SLES 12 SP4In case a package installs a conguration le for loading a kernel module, the le gets installed to /usr/lib/modules-load.d . If two conguration les with the same name exist, the one in /etc/modules-load.d tales precedence. For more information, see the modules-load.d(5) man page. 13.6.5 Performing Actions before Loading a Service With System V init actions that need to be performed before loading a service, needed to be specied in /etc/init.d/before.local . This procedure is no longer supported with systemd. If you need to do actions before starting services, do the following: Loading Kernel Modules Create a drop-in le in /etc/modules-load.d directory (see man modules-load.d for the syntax) Creating Files or Directories, Cleaning-up Directories, Changing Ownership Create a drop-in le in /etc/tmpfiles.d (see man tmpfiles.d for the syntax) Other Tasks Create a system service le, for example /etc/systemd/system/before.service , from the following template: [Unit] Before=NAME OF THE SERVICE YOU WANT THIS SERVICE TO BE STARTED BEFORE [Service] Type=oneshot RemainAfterExit=true ExecStart=YOUR_COMMAND # beware, executable is run directly, not through a shell, check the man pages # systemd.service and systemd.unit for full syntax [Install] # target in which to start the service WantedBy=multi-user.target #WantedBy=graphical.target When the service le is created, you should run the following commands (as root ): systemctl daemon-reload systemctl enable before Every time you modify the service le, you need to run: systemctl daemon-reload 184 Performing Actions before Loading a Service SLES 12 SP413.6.6 Kernel Control Groups (cgroups) On a traditional System V init system it is not always possible to clearly assign a process to the service that spawned it. Some services, such as Apache, spawn a lot of third-party processes (for example CGI or Java processes), which themselves spawn more processes. This makes a clear assignment dicult or even impossible. Additionally, a service may not terminate correctly, leaving some children alive. systemd solves this problem by placing each service into its own cgroup. cgroups are a kernel feature that allows aggregating processes and all their children into hierarchical organized groups. systemd names each cgroup after its service. Since a non-privileged process is not allowed to “leave” its cgroup, this provides an eective way to label all processes spawned by a service with the name of the service. To list all processes belonging to a service, use the command systemd-cgls . The result will look like the following (shortened) example: EXAMPLE 13.3: LIST ALL PROCESSES BELONGING TO A SERVICE root # systemd-cgls --no-pager ├─1 /usr/lib/systemd/systemd --switched-root --system --deserialize 20 ├─user.slice │ └─user-1000.slice │ ├─session-102.scope │ │ ├─12426 gdm-session-worker [pam/gdm-password] │ │ ├─15831 gdm-session-worker [pam/gdm-password] │ │ ├─15839 gdm-session-worker [pam/gdm-password] │ │ ├─15858 /usr/lib/gnome-terminal-server [...] └─system.slice ├─systemd-hostnamed.service │ └─17616 /usr/lib/systemd/systemd-hostnamed ├─cron.service │ └─1689 /usr/sbin/cron -n ├─ntpd.service │ └─1328 /usr/sbin/ntpd -p /var/run/ntp/ntpd.pid -g -u ntp:ntp -c /etc/ntp.conf ├─postfix.service │ ├─ 1676 /usr/lib/postfix/master -w │ ├─ 1679 qmgr -l -t fifo -u │ └─15590 pickup -l -t fifo -u ├─sshd.service │ └─1436 /usr/sbin/sshd -D 185 Kernel Control Groups (cgroups) SLES 12 SP4[...] See Book “System Analysis and Tuning Guide”, Chapter 9 “Kernel Control Groups” for more information about cgroups. 13.6.7 Terminating Services (Sending Signals) As explained in Section 13.6.6, “Kernel Control Groups (cgroups)”, it is not always possible to assign a process to its parent service process in a System V init system. This makes it dicult to terminate a service and all of its children. Child processes that have not been terminated will remain as zombie processes. systemd''s concept of conning each service into a cgroup makes it possible to clearly identify all child processes of a service and therefore allows you to send a signal to each of these processes. Use systemctl kill to send signals to services. For a list of available signals refer to man 7 signals . Sending SIGTERM to a Service SIGTERM is the default signal that is sent. systemctl kill MY_SERVICE Sending SIGNAL to a Service Use the -s option to specify the signal that should be sent. systemctl kill -s SIGNAL MY_SERVICE Selecting Processes By default the kill command sends the signal to all processes of the specied cgroup. You can restrict it to the control or the main process. The latter is for example useful to force a service to reload its conguration by sending SIGHUP : systemctl kill -s SIGHUP --kill-who=main MY_SERVICE Warning: Terminating or Restarting the D-Bus Service Is Not Supported The D-Bus service is the message bus for communication between systemd clients and the systemd manager that is running as pid 1. Even though dbus is a stand-alone daemon, it is an integral part of the init infrastructure. 186 Terminating Services (Sending Signals) SLES 12 SP4Terminating dbus or restarting it in the running system is similar to an attempt to terminate or restart pid 1. It will break systemd client/server communication and make most systemd functions unusable. Therefore, terminating or restarting dbus is neither recommended nor supported. 13.6.8 Debugging Services By default, systemd is not overly verbose. If a service was started successfully, no output will be produced. In case of a failure, a short error message will be displayed. However, systemctl status provides means to debug start-up and operation of a service. systemd comes with its own logging mechanism (“The Journal”) that logs system messages. This allows you to display the service messages together with status messages. The status command works similar to tail and can also display the log messages in dierent formats, making it a powerful debugging tool. Show Service Start-Up Failure Whenever a service fails to start, use systemctl status MY_SERVICE to get a detailed error message: root # systemctl start apache2 Job failed. See system journal and ''systemctl status'' for details. root # systemctl status apache2 Loaded: loaded (/usr/lib/systemd/system/apache2.service; disabled) Active: failed (Result: exit-code) since Mon, 04 Jun 2012 16:52:26 +0200; 29s ago Process: 3088 ExecStart=/usr/sbin/start_apache2 -D SYSTEMD -k start (code=exited, status=1/FAILURE) CGroup: name=systemd:/system/apache2.service Jun 04 16:52:26 g144 start_apache2[3088]: httpd2-prefork: Syntax error on line 205 of /etc/apache2/httpd.conf: Syntax error on li...alHost> Show Last N Service Messages The default behavior of the status subcommand is to display the last ten messages a service issued. To change the number of messages to show, use the --lines=N parameter: systemctl status ntp systemctl --lines=20 status ntp Show Service Messages in Append Mode 187 Debugging Services SLES 12 SP4To display a “live stream” of service messages, use the --follow option, which works like tail -f : systemctl --follow status ntp Messages Output Format The --output=MODE parameter allows you to change the output format of service messages. The most important modes available are: short The default format. Shows the log messages with a human readable time stamp. verbose Full output with all elds. cat Terse output without time stamps. 13.7 More Information For more information on systemd refer to the following online resources: Homepage http://www.freedesktop.org/wiki/Software/systemd systemd for Administrators Lennart Pöttering, one of the systemd authors, has written a series of blog entries (13 at the time of writing this chapter). Find them at http://0pointer.de/blog/projects . 188 More Information SLES 12 SP4III System 14 32-Bit and 64-Bit Applications in a 64-Bit System Environment 190 15 journalctl: Query the systemd Journal 192 16 Basic Networking 200 17 Printer Operation 273 18 The X Window System 287 19 Accessing File Systems with FUSE 300 20 Managing Kernel Modules 302 21 Dynamic Kernel Device Management with udev 306 22 Live Patching the Linux Kernel Using kGraft 318 23 Special System Features 325 24 Persistent Memory 33614 32-Bit and 64-Bit Applications in a 64-Bit System Environment SUSE® Linux Enterprise Server is available for several 64-bit platforms. This does not necessarily mean that all the applications included have already been ported to 64-bit platforms. SUSE Linux Enterprise Server supports the use of 32-bit applications in a 64-bit system environment. This chapter oers a brief overview of how this support is implemented on 64-bit SUSE Linux Enterprise Server platforms. SUSE Linux Enterprise Server for the 64-bit platforms POWER, z Systems and AMD64/Intel 64 is designed so that existing 32-bit applications run in the 64-bit environment “out-of-the-box.” The corresponding 32-bit platforms are ppc for POWER, and x86 for AMD64/Intel 64. This support means that you can continue to use your preferred 32-bit applications without waiting for a corresponding 64-bit port to become available. The current POWER system runs most applications in 32-bit mode, but you can run 64-bit applications. Note: No Support for Building 32-bit Applications SUSE Linux Enterprise Server does not support compiling 32-bit applications, it only oers runtime support for 32-bit binaries. 14.1 Runtime Support Important: Conflicts Between Application Versions If an application is available both for 32-bit and 64-bit environments, parallel installation of both versions is bound to lead to problems. In such cases, decide on one of the two versions and install and use this. An exception to this rule is PAM (pluggable authentication modules). SUSE Linux Enterprise Server uses PAM in the authentication process as a layer that mediates between user and application. On a 64-bit operating system that also runs 32-bit applications it is necessary to always install both versions of a PAM module. 190 Runtime Support SLES 12 SP4To be executed correctly, every application requires a range of libraries. Unfortunately, the names for the 32-bit and 64-bit versions of these libraries are identical. They must be dierentiated from each other in another way. To retain compatibility with the 32-bit version, the libraries are stored at the same place in the system as in the 32-bit environment. The 32-bit version of libc.so.6 is located under /lib/ libc.so.6 in both the 32-bit and 64-bit environments. All 64-bit libraries and object les are located in directories called lib64 . The 64-bit object les that you would normally expect to nd under /lib and /usr/lib are now found under /lib64 and /usr/lib64 . This means that there is space for the 32-bit libraries under /lib and /usr/lib , so the le name for both versions can remain unchanged. Subdirectories of 32-bit /lib directories which contain data content that does not depend on the word size are not moved. This scheme conforms to LSB (Linux Standards Base) and FHS (File System Hierarchy Standard). 14.2 Kernel Specifications The 64-bit kernels for AMD64/Intel  64, POWER and z  Systems oer both a 64-bit and a 32-bit kernel ABI (application binary interface). The latter is identical with the ABI for the corresponding 32-bit kernel. This means that the 32-bit application can communicate with the 64-bit kernel in the same way as with the 32-bit kernel. The 32-bit emulation of system calls for a 64-bit kernel does not support all the APIs used by system programs. This depends on the platform. For this reason, few applications, like lspci , must be compiled on non-POWER platforms as 64-bit programs to function properly. On IBM z Systems, not all ioctls are available in the 32-bit kernel ABI. A 64-bit kernel can only load 64-bit kernel modules that have been specially compiled for this kernel. It is not possible to use 32-bit kernel modules. Tip: Kernel-loadable Modules Some applications require separate kernel-loadable modules. If you intend to use such a 32-bit application in a 64-bit system environment, contact the provider of this application and SUSE to make sure that the 64-bit version of the kernel-loadable module and the 32- bit compiled version of the kernel API are available for this module. 191 Kernel Specifications SLES 12 SP415 journalctl: Query the systemd Journal When systemd replaced traditional init scripts in SUSE Linux Enterprise 12 (see Chapter 13, The systemd Daemon), it introduced its own logging system called journal. There is no need to run a syslog based service anymore, as all system events are written in the journal. The journal itself is a system service managed by systemd . Its full name is systemd- journald.service . It collects and stores logging data by maintaining structured indexed journals based on logging information received from the kernel, user processes, standard input, and system service errors. The systemd-journald service is on by default: # systemctl status systemd-journald systemd-journald.service - Journal Service Loaded: loaded (/usr/lib/systemd/system/systemd-journald.service; static) Active: active (running) since Mon 2014-05-26 08:36:59 EDT; 3 days ago Docs: man:systemd-journald.service(8) man:journald.conf(5) Main PID: 413 (systemd-journal) Status: "Processing requests..." CGroup: /system.slice/systemd-journald.service └─413 /usr/lib/systemd/systemd-journald [...] 15.1 Making the Journal Persistent The journal stores log data in /run/log/journal/ by default. Because the /run/ directory is volatile by nature, log data is lost at reboot. To make the log data persistent, the directory /var/log/journal/ with correct ownership and permissions must exist, where the systemd- journald service can store its data. systemd will create the directory for you—and switch to persistent logging—if you do the following: 1. As root , open /etc/systemd/journald.conf for editing. # vi /etc/systemd/journald.conf 2. Uncomment the line containing Storage= and change it to [...] [Journal] Storage=persistent #Compress=yes 192 Making the Journal Persistent SLES 12 SP4[...] 3. Save the le and restart systemd-journald: systemctl restart systemd-journald 15.2 journalctl Useful Switches This section introduces several common useful options to enhance the default journalctl behavior. All switches are described in the journalctl manual page, man 1 journalctl . Tip: Messages Related to a Specific Executable To show all journal messages related to a specic executable, specify the full path to the executable: journalctl /usr/lib/systemd/systemd -f Shows only the most recent journal messages, and prints new log entries as they are added to the journal. -e Prints the messages and jumps to the end of the journal, so that the latest entries are visible within the pager. -r Prints the messages of the journal in reverse order, so that the latest entries are listed rst. -k Shows only kernel messages. This is equivalent to the eld match _TRANSPORT=kernel (see Section 15.3.3, “Filtering Based on Fields”). -u Shows only messages for the specied systemd unit. This is equivalent to the eld match _SYSTEMD_UNIT=UNIT (see Section 15.3.3, “Filtering Based on Fields”). # journalctl -u apache2 [...] Jun 03 10:07:11 pinkiepie systemd[1]: Starting The Apache Webserver... 193 journalctl Useful Switches SLES 12 SP4Jun 03 10:07:12 pinkiepie systemd[1]: Started The Apache Webserver. 15.3 Filtering the Journal Output When called without switches, journalctl shows the full content of the journal, the oldest entries listed rst. The output can be ltered by specic switches and elds. 15.3.1 Filtering Based on a Boot Number journalctl can lter messages based on a specic system boot. To list all available boots, run # journalctl --list-boots -1 097ed2cd99124a2391d2cffab1b566f0 Mon 2014-05-26 08:36:56 EDT—Fri 2014-05-30 05:33:44 EDT 0 156019a44a774a0bb0148a92df4af81b Fri 2014-05-30 05:34:09 EDT—Fri 2014-05-30 06:15:01 EDT The rst column lists the boot oset: 0 for the current boot, -1 for the previous one, -2 for the one prior to that, etc. The second column contains the boot ID followed by the limiting time stamps of the specic boot. Show all messages from the current boot: # journalctl -b If you need to see journal messages from the previous boot, add an oset parameter. The following example outputs the previous boot messages: # journalctl -b -1 Another way is to list boot messages based on the boot ID. For this purpose, use the _BOOT_ID eld: # journalctl _BOOT_ID=156019a44a774a0bb0148a92df4af81b 15.3.2 Filtering Based on Time Interval You can lter the output of journalctl by specifying the starting and/or ending date. The date specication should be of the format "2014-06-30 9:17:16". If the time part is omitted, midnight is assumed. If seconds are omitted, ":00" is assumed. If the date part is omitted, the current day is assumed. Instead of numeric expression, you can specify the keywords "yesterday", "today", 194 Filtering the Journal Output SLES 12 SP4or "tomorrow". They refer to midnight of the day before the current day, of the current day, or of the day after the current day. If you specify "now", it refers to the current time. You can also specify relative times prexed with - or + , referring to times before or after the current time. Show only new messages since now, and update the output continuously: # journalctl --since "now" -f Show all messages since last midnight till 3:20am: # journalctl --since "today" --until "3:20" 15.3.3 Filtering Based on Fields You can lter the output of the journal by specic elds. The syntax of a eld to be matched is FIELD_NAME=MATCHED_VALUE , such as _SYSTEMD_UNIT=httpd.service . You can specify multiple matches in a single query to lter the output messages even more. See man 7 systemd.journal-fields for a list of default elds. Show messages produced by a specic process ID: # journalctl _PID=1039 Show messages belonging to a specic user ID: # journalctl _UID=1000 Show messages from the kernel ring buer (the same as dmesg produces): # journalctl _TRANSPORT=kernel Show messages from the service''s standard or error output: # journalctl _TRANSPORT=stdout Show messages produced by a specied service only: # journalctl _SYSTEMD_UNIT=avahi-daemon.service If two dierent elds are specied, only entries that match both expressions at the same time are shown: # journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=1488 If two matches refer to the same eld, all entries matching either expression are shown: # journalctl _SYSTEMD_UNIT=avahi-daemon.service _SYSTEMD_UNIT=dbus.service 195 Filtering Based on Fields SLES 12 SP4You can use the ''+'' separator to combine two expressions in a logical ''OR''. The following example shows all messages from the Avahi service process with the process ID 1480 together with all messages from the D-Bus service: # journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=1480 + _SYSTEMD_UNIT=dbus.service 15.4 Investigating systemd Errors This section introduces a simple example to illustrate how to nd and x the error reported by systemd during apache2 start-up. 1. Try to start the apache2 service: # systemctl start apache2 Job for apache2.service failed. See ''systemctl status apache2'' and ''journalctl -xn'' for details. 2. Let us see what the service''s status says: # systemctl status apache2 apache2.service - The Apache Webserver Loaded: loaded (/usr/lib/systemd/system/apache2.service; disabled) Active: failed (Result: exit-code) since Tue 2014-06-03 11:08:13 CEST; 7min ago Process: 11026 ExecStop=/usr/sbin/start_apache2 -D SYSTEMD -DFOREGROUND \ -k graceful-stop (code=exited, status=1/FAILURE) The ID of the process causing the failure is 11026. 3. Show the verbose version of messages related to process ID 11026: # journalctl -o verbose _PID=11026 [...] MESSAGE=AH00526: Syntax error on line 6 of /etc/apache2/default-server.conf: [...] MESSAGE=Invalid command ''DocumenttRoot'', perhaps misspelled or defined by a module [...] 4. Fix the typo inside /etc/apache2/default-server.conf , start the apache2 service, and print its status: # systemctl start apache2 && systemctl status apache2 apache2.service - The Apache Webserver Loaded: loaded (/usr/lib/systemd/system/apache2.service; disabled) 196 Investigating systemd Errors SLES 12 SP4Active: active (running) since Tue 2014-06-03 11:26:24 CEST; 4ms ago Process: 11026 ExecStop=/usr/sbin/start_apache2 -D SYSTEMD -DFOREGROUND -k graceful-stop (code=exited, status=1/FAILURE) Main PID: 11263 (httpd2-prefork) Status: "Processing requests..." CGroup: /system.slice/apache2.service ├─11263 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -D [...] ├─11280 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -D [...] ├─11281 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -D [...] ├─11282 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -D [...] ├─11283 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -D [...] └─11285 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -D [...] 15.5 Journald Configuration The behavior of the systemd-journald service can be adjusted by modifying /etc/systemd/ journald.conf . This section introduces only basic option settings. For a complete le description, see man 5 journald.conf . Note that you need to restart the journal for the changes to take eect with # systemctl restart systemd-journald 15.5.1 Changing the Journal Size Limit If the journal log data is saved to a persistent location (see Section  15.1, “Making the Journal Persistent”), it uses up to 10% of the le system the /var/log/journal resides on. For example, if /var/log/journal is located on a 30 GB /var partition, the journal may use up to 3 GB of the disk space. To change this limit, change (and uncomment) the SystemMaxUse option: SystemMaxUse=50M 15.5.2 Forwarding the Journal to /dev/ttyX You can forward the journal to a terminal device to inform you about system messages on a preferred terminal screen, for example /dev/tty12 . Change the following journald options to ForwardToConsole=yes TTYPath=/dev/tty12 197 Journald Configuration SLES 12 SP415.5.3 Forwarding the Journal to Syslog Facility Journald is backward compatible with traditional syslog implementations such as rsyslog . Make sure the following is valid: rsyslog is installed. # rpm -q rsyslog rsyslog-7.4.8-2.16.x86_64 rsyslog service is enabled. # systemctl is-enabled rsyslog enabled Forwarding to syslog is enabled in /etc/systemd/journald.conf . ForwardToSyslog=yes 15.6 Using YaST to Filter the systemd Journal For an easy way of ltering the systemd journal (without having to deal with the journalctl syntax), you can use the YaST journal module. After installing it with sudo zypper in yast2- journal , start it from YaST by selecting System Systemd Journal. Alternatively, start it from command line by entering sudo yast2 journal . FIGURE 15.1: YAST SYSTEMD JOURNAL 198 Forwarding the Journal to Syslog Facility SLES 12 SP4The module displays the log entries in a table. The search box on top allows you to search for entries that contain certain characters, similar to using grep . To lter the entries by date and time, unit, le, or priority, click Change lters and set the respective options. 199 Using YaST to Filter the systemd Journal SLES 12 SP416 Basic Networking Linux oers the necessary networking tools and features for integration into all types of network structures. Network access using a network card can be congured with YaST. Manual conguration is also possible. In this chapter only the fundamental mechanisms and the relevant network conguration les are covered. Linux and other Unix operating systems use the TCP/IP protocol. It is not a single network protocol, but a family of network protocols that oer various services. The protocols listed in Several Protocols in the TCP/IP Protocol Family, are provided for exchanging data between two machines via TCP/IP. Networks combined by TCP/IP, comprising a worldwide network, are also called “the Internet.” RFC stands for Request for Comments. RFCs are documents that describe various Internet protocols and implementation procedures for the operating system and its applications. The RFC documents describe the setup of Internet protocols. For more information about RFCs, see https://datatracker.ietf.org/ . SEVERAL PROTOCOLS IN THE TCP/IP PROTOCOL FAMILY TCP Transmission Control Protocol: a connection-oriented secure protocol. The data to transmit is rst sent by the application as a stream of data and converted into the appropriate format by the operating system. The data arrives at the respective application on the destination host in the original data stream format it was initially sent. TCP determines whether any data has been lost or jumbled during the transmission. TCP is implemented wherever the data sequence matters. UDP User Datagram Protocol: a connectionless, insecure protocol. The data to transmit is sent in the form of packets generated by the application. The order in which the data arrives at the recipient is not guaranteed and data loss is possible. UDP is suitable for record-oriented applications. It features a smaller latency period than TCP. ICMP 200 SLES 12 SP4Internet Control Message Protocol: This is not a protocol for the end user, but a special control protocol that issues error reports and can control the behavior of machines participating in TCP/IP data transfer. In addition, it provides a special echo mode that can be viewed using the program ping. IGMP Internet Group Management Protocol: This protocol controls machine behavior when implementing IP multicast. As shown in Figure 16.1, “Simplified Layer Model for TCP/IP”, data exchange takes place in dierent layers. The actual network layer is the insecure data transfer via IP (Internet protocol). On top of IP, TCP (transmission control protocol) guarantees, to a certain extent, security of the data transfer. The IP layer is supported by the underlying hardware-dependent protocol, such as Ethernet. TCP/IP Model OSI Model Application Layer Application Layer Presentation Layer Session Layer Transport Layer Transport Layer Internet Layer Network Layer Data Link Layer Network Access Layer Physical Layer FIGURE 16.1: SIMPLIFIED LAYER MODEL FOR TCP/IP 201 SLES 12 SP4The diagram provides one or two examples for each layer. The layers are ordered according to abstraction levels. The lowest layer is very close to the hardware. The uppermost layer, however, is almost a complete abstraction from the hardware. Every layer has its own special function. The special functions of each layer are mostly implicit in their description. The data link and physical layers represent the physical network used, such as Ethernet. Almost all hardware protocols work on a packet-oriented basis. The data to transmit is collected into packets (it cannot be sent all at once). The maximum size of a TCP/IP packet is approximately 64 KB. Packets are normally quite smaller, as the network hardware can be a limiting factor. The maximum size of a data packet on an Ethernet is about fteen hundred bytes. The size of a TCP/IP packet is limited to this amount when the data is sent over an Ethernet. If more data is transferred, more data packets need to be sent by the operating system. For the layers to serve their designated functions, additional information regarding each layer must be saved in the data packet. This takes place in the header of the packet. Every layer attaches a small block of data, called the protocol header, to the front of each emerging packet. A sample TCP/IP data packet traveling over an Ethernet cable is illustrated in Figure 16.2, “TCP/ IP Ethernet Packet”. The proof sum is located at the end of the packet, not at the beginning. This simplies things for the network hardware. FIGURE 16.2: TCP/IP ETHERNET PACKET When an application sends data over the network, the data passes through each layer, all implemented in the Linux kernel except the physical layer. Each layer is responsible for preparing the data so it can be passed to the next layer. The lowest layer is ultimately responsible for sending the data. The entire procedure is reversed when data is received. Like the layers of an onion, in each layer the protocol headers are removed from the transported data. Finally, the transport layer is responsible for making the data available for use by the applications at the destination. In this manner, one layer only communicates with the layer directly above or below it. For applications, it is irrelevant whether data is transmitted via a 100 Mbit/s FDDI network or via a 56-Kbit/s modem line. Likewise, it is irrelevant for the data line which kind of data is transmitted, as long as packets are in the correct format. 202 SLES 12 SP416.1 IP Addresses and Routing The discussion in this section is limited to IPv4 networks. For information about IPv6 protocol, the successor to IPv4, refer to Section 16.2, “IPv6—The Next Generation Internet”. 16.1.1 IP Addresses Every computer on the Internet has a unique 32-bit address. These 32 bits (or 4 bytes) are normally written as illustrated in the second row in Example 16.1, “Writing IP Addresses”. EXAMPLE 16.1: WRITING IP ADDRESSES IP Address (binary): 11000000 10101000 00000000 00010100 IP Address (decimal): 192. 168. 0. 20 In decimal form, the four bytes are written in the decimal number system, separated by periods. The IP address is assigned to a host or a network interface. It can be used only once throughout the world. There are exceptions to this rule, but these are not relevant to the following passages. The points in IP addresses indicate the hierarchical system. Until the 1990s, IP addresses were strictly categorized in classes. However, this system proved too inexible and was discontinued. Now, classless routing (CIDR, classless interdomain routing) is used. 16.1.2 Netmasks and Routing Netmasks are used to dene the address range of a subnet. If two hosts are in the same subnet, they can reach each other directly. If they are not in the same subnet, they need the address of a gateway that handles all the trac for the subnet. To check if two IP addresses are in the same subnet, simply “AND” both addresses with the netmask. If the result is identical, both IP addresses are in the same local network. If there are dierences, the remote IP address, and thus the remote interface, can only be reached over a gateway. To understand how the netmask works, look at Example 16.2, “Linking IP Addresses to the Netmask”. The netmask consists of 32 bits that identify how much of an IP address belongs to the network. All those bits that are 1 mark the corresponding bit in the IP address as belonging to the network. All bits that are 0 mark bits inside the subnet. This means that the more bits are 1 , the smaller the subnet is. Because the netmask always consists of several successive 1 bits, it is also possible to count the number of bits in the netmask. In Example 16.2, “Linking IP Addresses to the Netmask” the rst net with 24 bits could also be written as 192.168.0.0/24 . 203 IP Addresses and Routing SLES 12 SP4EXAMPLE 16.2: LINKING IP ADDRESSES TO THE NETMASK IP address (192.168.0.20): 11000000 10101000 00000000 00010100 Netmask (255.255.255.0): 11111111 11111111 11111111 00000000 --------------------------------------------------------------- Result of the link: 11000000 10101000 00000000 00000000 In the decimal system: 192. 168. 0. 0 IP address (213.95.15.200): 11010101 10111111 00001111 11001000 Netmask (255.255.255.0): 11111111 11111111 11111111 00000000 --------------------------------------------------------------- Result of the link: 11010101 10111111 00001111 00000000 In the decimal system: 213. 95. 15. 0 To give another example: all machines connected with the same Ethernet cable are usually located in the same subnet and are directly accessible. Even when the subnet is physically divided by switches or bridges, these hosts can still be reached directly. IP addresses outside the local subnet can only be reached if a gateway is congured for the target network. In the most common case, there is only one gateway that handles all trac that is external. However, it is also possible to congure several gateways for dierent subnets. If a gateway has been congured, all external IP packets are sent to the appropriate gateway. This gateway then attempts to forward the packets in the same manner—from host to host— until it reaches the destination host or the packet''s TTL (time to live) expires. SPECIFIC ADDRESSES Base Network Address This is the netmask AND any address in the network, as shown in Example 16.2, “Linking IP Addresses to the Netmask” under Result . This address cannot be assigned to any hosts. Broadcast Address This could be paraphrased as: “Access all hosts in this subnet.” To generate this, the netmask is inverted in binary form and linked to the base network address with a logical OR. The above example therefore results in 192.168.0.255. This address cannot be assigned to any hosts. Local Host The address 127.0.0.1 is assigned to the “loopback device” on each host. A connection can be set up to your own machine with this address and with all addresses from the complete 127.0.0.0/8 loopback network as dened with IPv4. With IPv6 there is only one loopback address ( ::1 ). 204 Netmasks and Routing SLES 12 SP4Because IP addresses must be unique all over the world, you cannot select random addresses. There are three address domains to use if you want to set up a private IP-based network. These cannot get any connection from the rest of the Internet, because they cannot be transmitted over the Internet. These address domains are specied in RFC 1597 and listed in Table 16.1, “Private IP Address Domains”. TABLE 16.1: PRIVATE IP ADDRESS DOMAINS Network/Netmask Domain 10.0.0.0 / 255.0.0.0 10.x.x.x 172.16.0.0 / 255.240.0.0 172.16.x.x – 172.31.x.x 192.168.0.0 / 255.255.0.0 192.168.x.x 16.2 IPv6—The Next Generation Internet Important: IBM z Systems: IPv6 Support IPv6 is not supported by the CTC and IUCV network connections of the IBM z Systems hardware. Due to the emergence of the World Wide Web (WWW), the Internet has experienced explosive growth, with an increasing number of computers communicating via TCP/IP in the past fteen years. Since Tim Berners-Lee at CERN (http://public.web.cern.ch ) invented the WWW in 1990, the number of Internet hosts has grown from a few thousand to about a hundred million. As mentioned, an IPv4 address consists of only 32 bits. Also, quite a few IP addresses are lost —they cannot be used because of the way in which networks are organized. The number of addresses available in your subnet is two to the power of the number of bits, minus two. A subnet has, for example, 2, 6, or 14 addresses available. To connect 128 hosts to the Internet, for example, you need a subnet with 256 IP addresses, from which only 254 are usable, because two IP addresses are needed for the structure of the subnet itself: the broadcast and the base network address. Under the current IPv4 protocol, DHCP or NAT (network address translation) are the typical mechanisms used to circumvent the potential address shortage. Combined with the convention to keep private and public address spaces separate, these methods can certainly mitigate the 205 IPv6—The Next Generation Internet SLES 12 SP4shortage. The problem with them lies in their conguration, which is a chore to set up and a burden to maintain. To set up a host in an IPv4 network, you need several address items, such as the host''s own IP address, the subnetmask, the gateway address and maybe a name server address. All these items need to be known and cannot be derived from somewhere else. With IPv6, both the address shortage and the complicated conguration should be a thing of the past. The following sections tell more about the improvements and benets brought by IPv6 and about the transition from the old protocol to the new one. 16.2.1 Advantages The most important and most visible improvement brought by the new protocol is the enormous expansion of the available address space. An IPv6 address is made up of 128 bit values instead of the traditional 32 bits. This provides for as many as several quadrillion IP addresses. However, IPv6 addresses are not only dierent from their predecessors with regard to their length. They also have a dierent internal structure that may contain more specic information about the systems and the networks to which they belong. More details about this are found in Section 16.2.2, “Address Types and Structure”. The following is a list of other advantages of the new protocol: Autoconfiguration IPv6 makes the network “plug and play” capable, which means that a newly set up system integrates into the (local) network without any manual conguration. The new host uses its automatic conguration mechanism to derive its own address from the information made available by the neighboring routers, relying on a protocol called the neighbor discovery (ND) protocol. This method does not require any intervention on the administrator''s part and there is no need to maintain a central server for address allocation—an additional advantage over IPv4, where automatic address allocation requires a DHCP server. Nevertheless if a router is connected to a switch, the router should send periodic advertisements with ags telling the hosts of a network how they should interact with each other. For more information, see RFC 2462 and the radvd.conf(5) man page, and RFC 3315. Mobility IPv6 makes it possible to assign several addresses to one network interface at the same time. This allows users to access several networks easily, something that could be compared with the international roaming services oered by mobile phone companies. When you take 206 Advantages SLES 12 SP4your mobile phone abroad, the phone automatically logs in to a foreign service when it enters the corresponding area, so you can be reached under the same number everywhere and can place an outgoing call, as you would in your home area. Secure Communication With IPv4, network security is an add-on function. IPv6 includes IPsec as one of its core features, allowing systems to communicate over a secure tunnel to avoid eavesdropping by outsiders on the Internet. Backward Compatibility Realistically, it would be impossible to switch the entire Internet from IPv4 to IPv6 at one time. Therefore, it is crucial that both protocols can coexist not only on the Internet, but also on one system. This is ensured by compatible addresses (IPv4 addresses can easily be translated into IPv6 addresses) and by using several tunnels. See Section 16.2.3, “Coexistence of IPv4 and IPv6”. Also, systems can rely on a dual stack IP technique to support both protocols at the same time, meaning that they have two network stacks that are completely separate, such that there is no interference between the two protocol versions. Custom Tailored Services through Multicasting With IPv4, some services, such as SMB, need to broadcast their packets to all hosts in the local network. IPv6 allows a much more ne-grained approach by enabling servers to address hosts through multicasting, that is by addressing several hosts as parts of a group. This is dierent from addressing all hosts through broadcasting or each host individually through unicasting. Which hosts are addressed as a group may depend on the concrete application. There are some predened groups to address all name servers (the all name servers multicast group), for example, or all routers (the all routers multicast group). 16.2.2 Address Types and Structure As mentioned, the current IP protocol has two major limitations: there is an increasing shortage of IP addresses, and conguring the network and maintaining the routing tables is becoming a more complex and burdensome task. IPv6 solves the rst problem by expanding the address space to 128 bits. The second one is mitigated by introducing a hierarchical address structure combined with sophisticated techniques to allocate network addresses, and multihoming (the ability to assign several addresses to one device, giving access to several networks). When dealing with IPv6, it is useful to know about three dierent types of addresses: Unicast 207 Address Types and Structure SLES 12 SP4Addresses of this type are associated with exactly one network interface. Packets with such an address are delivered to only one destination. Accordingly, unicast addresses are used to transfer packets to individual hosts on the local network or the Internet. Multicast Addresses of this type relate to a group of network interfaces. Packets with such an address are delivered to all destinations that belong to the group. Multicast addresses are mainly used by certain network services to communicate with certain groups of hosts in a well- directed manner. Anycast Addresses of this type are related to a group of interfaces. Packets with such an address are delivered to the member of the group that is closest to the sender, according to the principles of the underlying routing protocol. Anycast addresses are used to make it easier for hosts to nd out about servers oering certain services in the given network area. All servers of the same type have the same anycast address. Whenever a host requests a service, it receives a reply from the server with the closest location, as determined by the routing protocol. If this server should fail for some reason, the protocol automatically selects the second closest server, then the third one, and so forth. An IPv6 address is made up of eight four-digit elds, each representing 16 bits, written in hexadecimal notation. They are separated by colons ( : ). Any leading zero bytes within a given eld may be dropped, but zeros within the eld or at its end may not. Another convention is that more than four consecutive zero bytes may be collapsed into a double colon. However, only one such :: is allowed per address. This kind of shorthand notation is shown in Example 16.3, “Sample IPv6 Address”, where all three lines represent the same address. EXAMPLE 16.3: SAMPLE IPV6 ADDRESS fe80 : 0000 : 0000 : 0000 : 0000 : 10 : 1000 : 1a4 fe80 : 0 : 0 : 0 : 0 : 10 : 1000 : 1a4 fe80 : : 10 : 1000 : 1a4 Each part of an IPv6 address has a dened function. The rst bytes form the prex and specify the type of address. The center part is the network portion of the address, but it may be unused. The end of the address forms the host part. With IPv6, the netmask is dened by indicating the length of the prex after a slash at the end of the address. An address, as shown in Example 16.4, “IPv6 Address Specifying the Prefix Length”, contains the information that the rst 64 bits form the network part of the address and the last 64 form its host part. In other words, the 64 means that 208 Address Types and Structure SLES 12 SP4the netmask is lled with 64 1-bit values from the left. As with IPv4, the IP address is combined with AND with the values from the netmask to determine whether the host is located in the same subnet or in another one. EXAMPLE 16.4: IPV6 ADDRESS SPECIFYING THE PREFIX LENGTH fe80::10:1000:1a4/64 IPv6 knows about several predened types of prexes. Some are shown in Various IPv6 Prefixes. VARIOUS IPV6 PREFIXES 00 IPv4 addresses and IPv4 over IPv6 compatibility addresses. These are used to maintain compatibility with IPv4. Their use still requires a router able to translate IPv6 packets into IPv4 packets. Several special addresses, such as the one for the loopback device, have this prex as well. 2 or 3 as the first digit Aggregatable global unicast addresses. As is the case with IPv4, an interface can be assigned to form part of a certain subnet. Currently, there are the following address spaces: 2001::/16 (production quality address space) and 2002::/16 (6to4 address space). fe80::/10 Link-local addresses. Addresses with this prex should not be routed and should therefore only be reachable from within the same subnet. fec0::/10 Site-local addresses. These may be routed, but only within the network of the organization to which they belong. In eect, they are the IPv6 equivalent of the current private network address space, such as 10.x.x.x . ff These are multicast addresses. A unicast address consists of three basic components: Public Topology The rst part (which also contains one of the prexes mentioned above) is used to route packets through the public Internet. It includes information about the company or institution that provides the Internet access. Site Topology 209 Address Types and Structure SLES 12 SP4The second part contains routing information about the subnet to which to deliver the packet. Interface ID The third part identies the interface to which to deliver the packet. This also allows for the MAC to form part of the address. Given that the MAC is a globally unique, xed identier coded into the device by the hardware maker, the conguration procedure is substantially simplied. In fact, the rst 64 address bits are consolidated to form the EUI-64 token, with the last 48 bits taken from the MAC, and the remaining 24 bits containing special information about the token type. This also makes it possible to assign an EUI-64 token to interfaces that do not have a MAC, such as those based on PPP. On top of this basic structure, IPv6 distinguishes between ve dierent types of unicast addresses: :: (unspecified) This address is used by the host as its source address when the interface is initialized for the rst time (at which point, the address cannot yet be determined by other means). ::1 (loopback) The address of the loopback device. IPv4 Compatible Addresses The IPv6 address is formed by the IPv4 address and a prex consisting of 96 zero bits. This type of compatibility address is used for tunneling (see Section 16.2.3, “Coexistence of IPv4 and IPv6”) to allow IPv4 and IPv6 hosts to communicate with others operating in a pure IPv4 environment. IPv4 Addresses Mapped to IPv6 This type of address species a pure IPv4 address in IPv6 notation. Local Addresses There are two address types for local use: link-local This type of address can only be used in the local subnet. Packets with a source or target address of this type should not be routed to the Internet or other subnets. These addresses contain a special prex ( fe80::/10 ) and the interface ID of the network card, with the middle part consisting of zero bytes. Addresses of this type are used during automatic conguration to communicate with other hosts belonging to the same subnet. 210 Address Types and Structure SLES 12 SP4site-local Packets with this type of address may be routed to other subnets, but not to the wider Internet—they must remain inside the organization''s own network. Such addresses are used for intranets and are an equivalent of the private address space dened by IPv4. They contain a special prex ( fec0::/10 ), the interface ID, and a 16 bit eld specifying the subnet ID. Again, the rest is lled with zero bytes. As a completely new feature introduced with IPv6, each network interface normally gets several IP addresses, with the advantage that several networks can be accessed through the same interface. One of these networks can be congured completely automatically using the MAC and a known prex with the result that all hosts on the local network can be reached when IPv6 is enabled (using the link-local address). With the MAC forming part of it, any IP address used in the world is unique. The only variable parts of the address are those specifying the site topology and the public topology, depending on the actual network in which the host is currently operating. For a host to go back and forth between dierent networks, it needs at least two addresses. One of them, the home address, not only contains the interface ID but also an identier of the home network to which it normally belongs (and the corresponding prex). The home address is a static address and, as such, it does not normally change. Still, all packets destined to the mobile host can be delivered to it, regardless of whether it operates in the home network or somewhere outside. This is made possible by the completely new features introduced with IPv6, such as stateless autoconguration and neighbor discovery. In addition to its home address, a mobile host gets one or more additional addresses that belong to the foreign networks where it is roaming. These are called care-of addresses. The home network has a facility that forwards any packets destined to the host when it is roaming outside. In an IPv6 environment, this task is performed by the home agent, which takes all packets destined to the home address and relays them through a tunnel. On the other hand, those packets destined to the care-of address are directly transferred to the mobile host without any special detours. 16.2.3 Coexistence of IPv4 and IPv6 The migration of all hosts connected to the Internet from IPv4 to IPv6 is a gradual process. Both protocols will coexist for some time to come. The coexistence on one system is guaranteed where there is a dual stack implementation of both protocols. That still leaves the question of how an IPv6 enabled host should communicate with an IPv4 host and how IPv6 packets should be transported by the current networks, which are predominantly IPv4-based. The best solutions oer tunneling and compatibility addresses (see Section 16.2.2, “Address Types and Structure”). 211 Coexistence of IPv4 and IPv6 SLES 12 SP4IPv6 hosts that are more or less isolated in the (worldwide) IPv4 network can communicate through tunnels: IPv6 packets are encapsulated as IPv4 packets to move them across an IPv4 network. Such a connection between two IPv4 hosts is called a tunnel. To achieve this, packets must include the IPv6 destination address (or the corresponding prex) and the IPv4 address of the remote host at the receiving end of the tunnel. A basic tunnel can be congured manually according to an agreement between the hosts'' administrators. This is also called static tunneling. However, the conguration and maintenance of static tunnels is often too labor-intensive to use them for daily communication needs. Therefore, IPv6 provides for three dierent methods of dynamic tunneling: 6over4 IPv6 packets are automatically encapsulated as IPv4 packets and sent over an IPv4 network capable of multicasting. IPv6 is tricked into seeing the whole network (Internet) as a huge local area network (LAN). This makes it possible to determine the receiving end of the IPv4 tunnel automatically. However, this method does not scale very well and is also hampered because IP multicasting is far from widespread on the Internet. Therefore, it only provides a solution for smaller corporate or institutional networks where multicasting can be enabled. The specications for this method are laid down in RFC 2529. 6to4 With this method, IPv4 addresses are automatically generated from IPv6 addresses, enabling isolated IPv6 hosts to communicate over an IPv4 network. However, several problems have been reported regarding the communication between those isolated IPv6 hosts and the Internet. The method is described in RFC 3056. IPv6 Tunnel Broker This method relies on special servers that provide dedicated tunnels for IPv6 hosts. It is described in RFC 3053. 16.2.4 Configuring IPv6 To congure IPv6, you normally do not need to make any changes on the individual workstations. IPv6 is enabled by default. To disable or enable IPv6 on an installed system, use the YaST Network Settings module. On the Global Options tab, select or deselect the Enable IPv6 option as necessary. To enable it temporarily until the next reboot, enter modprobe -i ipv6 as root . It is impossible to unload the IPv6 module after it has been loaded. 212 Configuring IPv6 SLES 12 SP4Because of the autoconguration concept of IPv6, the network card is assigned an address in the link-local network. Normally, no routing table management takes place on a workstation. The network routers can be queried by the workstation, using the router advertisement protocol, for what prex and gateways should be implemented. The radvd program can be used to set up an IPv6 router. This program informs the workstations which prex to use for the IPv6 addresses and which routers. Alternatively, use zebra/quagga for automatic conguration of both addresses and routing. For information about how to set up various types of tunnels using the /etc/sysconfig/ network les, see the man page of ifcfg-tunnel ( man ifcfg-tunnel ). 16.2.5 For More Information The above overview does not cover the topic of IPv6 comprehensively. For a more in-depth look at the new protocol, refer to the following online documentation and books: http://www.ipv6.org/ The starting point for everything about IPv6. http://www.ipv6day.org All information needed to start your own IPv6 network. http://www.ipv6-to-standard.org/ The list of IPv6-enabled products. http://www.bieringer.de/linux/IPv6/ Here, nd the Linux IPv6-HOWTO and many links related to the topic. RFC 2460 The fundamental RFC about IPv6. IPv6 Essentials A book describing all the important aspects of the topic is IPv6 Essentials by Silvia Hagen (ISBN 0-596-00125-8). 213 For More Information SLES 12 SP416.3 Name Resolution DNS assists in assigning an IP address to one or more names and assigning a name to an IP address. In Linux, this conversion is usually carried out by a special type of software known as bind. The machine that takes care of this conversion is called a name server. The names make up a hierarchical system in which each name component is separated by a period. The name hierarchy is, however, independent of the IP address hierarchy described above. Consider a complete name, such as jupiter.example.com , written in the format hostname.domain . A full name, called a fully qualied domain name (FQDN), consists of a host name and a domain name ( example.com ). The latter also includes the top level domain or TLD ( com ). TLD assignment has become quite confusing for historical reasons. Traditionally, three-letter domain names are used in the USA. In the rest of the world, the two-letter ISO national codes are the standard. In addition to that, longer TLDs were introduced in 2000 that represent certain spheres of activity (for example, .info , .name , .museum ). In the early days of the Internet (before 1990), the le /etc/hosts was used to store the names of all the machines represented over the Internet. This quickly proved to be impractical in the face of the rapidly growing number of computers connected to the Internet. For this reason, a decentralized database was developed to store the host names in a widely distributed manner. This database, similar to the name server, does not have the data pertaining to all hosts in the Internet readily available, but can dispatch requests to other name servers. The top of the hierarchy is occupied by root name servers. These root name servers manage the top level domains and are run by the Network Information Center (NIC). Each root name server knows about the name servers responsible for a given top level domain. Information about top level domain NICs is available at http://www.internic.net . DNS can do more than resolve host names. The name server also knows which host is receiving e-mails for an entire domain—the mail exchanger (MX). For your machine to resolve an IP address, it must know about at least one name server and its IP address. Easily specify such a name server using YaST. The conguration of name server access with SUSE® Linux Enterprise Server is described in Section 16.4.1.4, “Configuring Host Name and DNS”. Setting up your own name server is described in Chapter 26, The Domain Name System. The protocol whois is closely related to DNS. With this program, quickly nd out who is responsible for a given domain. 214 Name Resolution SLES 12 SP4Note: MDNS and .local Domain Names The .local top level domain is treated as link-local domain by the resolver. DNS requests are send as multicast DNS requests instead of normal DNS requests. If you already use the .local domain in your name server conguration, you must switch this option o in /etc/host.conf . For more information, see the host.conf manual page. If you want to switch o MDNS during installation, use nomdns=1 as a boot parameter. For more information on multicast DNS, see http://www.multicastdns.org . 16.4 Configuring a Network Connection with YaST There are many supported networking types on Linux. Most of them use dierent device names and the conguration les are spread over several locations in the le system. For a detailed overview of the aspects of manual network conguration, see Section 16.5, “Configuring a Network Connection Manually”. All network interfaces with link up (with a network cable connected) are automatically congured. Additional hardware can be congured any time on the installed system. The following sections describe the network conguration for all types of network connections supported by SUSE Linux Enterprise Server. Tip: IBM z Systems: Hotpluggable Network Cards On IBM z Systems platforms, hotpluggable network cards are supported, but not their automatic network integration via DHCP (as is the case on the PC). After detection, manually congure the interface. 16.4.1 Configuring the Network Card with YaST To congure your Ethernet or Wi-Fi/Bluetooth card in YaST, select System Network Settings. After starting the module, YaST displays the Network Settings dialog with four tabs: Global Options, Overview, Hostname/DNS and Routing. The Global Options tab allows you to set general networking options such as the network setup method, IPv6, and general DHCP options. For more information, see Section 16.4.1.1, “Configuring Global Networking Options”. 215 Configuring a Network Connection with YaST SLES 12 SP4The Overview tab contains information about installed network interfaces and congurations. Any properly detected network card is listed with its name. You can manually congure new cards, remove or change their conguration in this dialog. To manually congure a card that was not automatically detected, see Section 16.4.1.3, “Configuring an Undetected Network Card”. If you want to change the conguration of an already congured card, see Section 16.4.1.2, “Changing the Configuration of a Network Card”. The Hostname/DNS tab allows to set the host name of the machine and name the servers to be used. For more information, see Section 16.4.1.4, “Configuring Host Name and DNS”. The Routing tab is used for the conguration of routing. See Section 16.4.1.5, “Configuring Routing” for more information. FIGURE 16.3: CONFIGURING NETWORK SETTINGS 16.4.1.1 Configuring Global Networking Options The Global Options tab of the YaST Network Settings module allows you to set important global networking options, such as the use of NetworkManager, IPv6 and DHCP client options. These settings are applicable for all network interfaces. 216 Configuring the Network Card with YaST SLES 12 SP4Note: NetworkManager Provided by Workstation Extension NetworkManager is now provided by the Workstation Extension. To install NetworkManager, activate the Workstation Extension repository, and select the NetworkManager packages. In the Network Setup Method choose the way network connections are managed. If you want a NetworkManager desktop applet to manage connections for all interfaces, choose NetworkManager Service. NetworkManager is well suited for switching between multiple wired and wireless networks. If you do not run a desktop environment, or if your computer is a Xen server, virtual system, or provides network services such as DHCP or DNS in your network, use the Wicked Service method. If NetworkManager is used, nm-applet should be used to congure network options and the Overview, Hostname/DNS and Routing tabs of the Network Settings module are disabled. For more information on NetworkManager, see the SUSE Linux Enterprise Desktop documentation. In the IPv6 Protocol Settings choose whether to use the IPv6 protocol. It is possible to use IPv6 together with IPv4. By default, IPv6 is enabled. However, in networks not using IPv6 protocol, response times can be faster with IPv6 protocol disabled. To disable IPv6, deactivate Enable IPv6. If IPv6 is disabled, the kernel no longer loads the IPv6 module automatically. This setting will be applied after reboot. In the DHCP Client Options congure options for the DHCP client. The DHCP Client Identier must be dierent for each DHCP client on a single network. If left empty, it defaults to the hardware address of the network interface. However, if you are running several virtual machines using the same network interface and, therefore, the same hardware address, specify a unique free- form identier here. The Hostname to Send species a string used for the host name option eld when the DHCP client sends messages to DHCP server. Some DHCP servers update name server zones (forward and reverse records) according to this host name (Dynamic DNS). Also, some DHCP servers require the Hostname to Send option eld to contain a specic string in the DHCP messages from clients. Leave AUTO to send the current host name (that is the one dened in /etc/HOSTNAME ). Make the option eld empty for not sending any host name. If you do not want to change the default route according to the information from DHCP, deactivate Change Default Route via DHCP. 217 Configuring the Network Card with YaST SLES 12 SP416.4.1.2 Changing the Configuration of a Network Card To change the conguration of a network card, select a card from the list of the detected cards in Network Settings Overview in YaST and click Edit. The Network Card Setup dialog appears in which to adjust the card conguration using the General, Address and Hardware tabs. 16.4.1.2.1 Configuring IP Addresses You can set the IP address of the network card or the way its IP address is determined in the Address tab of the Network Card Setup dialog. Both IPv4 and IPv6 addresses are supported. The network card can have No IP Address (which is useful for bonding devices), a Statically Assigned IP Address (IPv4 or IPv6) or a Dynamic Address assigned via DHCP or Zeroconf or both. If using Dynamic Address, select whether to use DHCP Version 4 Only (for IPv4), DHCP Version 6 Only (for IPv6) or DHCP Both Version 4 and 6. If possible, the rst network card with link that is available during the installation is automatically congured to use automatic address setup via DHCP. Note: IBM z Systems and DHCP On IBM z Systems platforms, DHCP-based address conguration is only supported with network cards that have a MAC address. This is only the case with OSA and OSA Express cards. DHCP should also be used if you are using a DSL line but with no static IP assigned by the ISP (Internet Service Provider). If you decide to use DHCP, congure the details in DHCP Client Options in the Global Options tab of the Network Settings dialog of the YaST network card conguration module. If you have a virtual host setup where dierent hosts communicate through the same interface, an DHCP Client Identier is necessary to distinguish them. DHCP is a good choice for client conguration but it is not ideal for server conguration. To set a static IP address, proceed as follows: 1. Select a card from the list of detected cards in the Overview tab of the YaST network card conguration module and click Edit. 2. In the Address tab, choose Statically Assigned IP Address. 3. Enter the IP Address. Both IPv4 and IPv6 addresses can be used. Enter the network mask in Subnet Mask. If the IPv6 address is used, use Subnet Mask for prex length in format /64 . 218 Configuring the Network Card with YaST SLES 12 SP4Optionally, you can enter a fully qualied Hostname for this address, which will be written to the /etc/hosts conguration le. 4. Click Next. 5. To activate the conguration, click OK. Note: Interface Activation and Link Detection During activation of a network interface, wicked checks for a carrier and only applies the IP conguration when a link has been detected. If you need to apply the conguration regardless of the link status (for example, when you want to test a service listening to a certain address), you can skip link detection by adding the variable LINK_REQUIRED=no to the conguration le of the interface in /etc/sysconfig/network/ifcfg . Additionally, you can use the variable LINK_READY_WAIT=5 to specify the timeout for waiting for a link in seconds. For more information about the ifcfg-* conguration les, refer to Section 16.5.2.5, “/ etc/sysconfig/network/ifcfg-*” and man 5 ifcfg . If you use the static address, the name servers and default gateway are not congured automatically. To congure name servers, proceed as described in Section 16.4.1.4, “Configuring Host Name and DNS”. To congure a gateway, proceed as described in Section 16.4.1.5, “Configuring Routing”. 16.4.1.2.2 Configuring Multiple Addresses One network device can have multiple IP addresses. Note: Aliases Are a Compatibility Feature These so-called aliases or labels, respectively, work with IPv4 only. With IPv6 they will be ignored. Using iproute2 network interfaces can have one or more addresses. Using YaST to set additional addresses for your network card, proceed as follows: 1. Select a card from the list of detected cards in the Overview tab of the YaST Network Settings dialog and click Edit. 219 Configuring the Network Card with YaST SLES 12 SP42. In the Address Additional Addresses tab, click Add. 3. Enter IPv4 Address Label, IP Address, and Netmask. Do not include the interface name in the alias name. 4. To activate the conguration, conrm the settings. 16.4.1.2.3 Changing the Device Name and Udev Rules It is possible to change the device name of the network card when it is used. It is also possible to determine whether the network card should be identied by udev via its hardware (MAC) address or via the bus ID. The later option is preferable in large servers to simplify hotplugging of cards. To set these options with YaST, proceed as follows: 1. Select a card from the list of detected cards in the Overview tab of the YaST Network Settings dialog and click Edit. 2. Go to the Hardware tab. The current device name is shown in Udev Rules. Click Change. 3. Select whether udev should identify the card by its MAC Address or Bus ID. The current MAC address and bus ID of the card are shown in the dialog. 4. To change the device name, check the Change Device Name option and edit the name. 5. To activate the conguration, conrm the settings. 16.4.1.2.4 Changing Network Card Kernel Driver For some network cards, several kernel drivers may be available. If the card is already congured, YaST allows you to select a kernel driver to be used from a list of available suitable drivers. It is also possible to specify options for the kernel driver. To set these options with YaST, proceed as follows: 1. Select a card from the list of detected cards in the Overview tab of the YaST Network Settings module and click Edit. 2. Go to the Hardware tab. 3. Select the kernel driver to be used in Module Name. Enter any options for the selected driver in Options in the form = = VALUE . If more options are used, they should be space- separated. 220 Configuring the Network Card with YaST SLES 12 SP44. To activate the conguration, conrm the settings. 16.4.1.2.5 Activating the Network Device If you use the method with wicked , you can congure your device to either start during boot, on cable connection, on card detection, manually, or never. To change device start-up, proceed as follows: 1. In YaST select a card from the list of detected cards in System Network Settings and click Edit. 2. In the General tab, select the desired entry from Device Activation. Choose At Boot Time to start the device during the system boot. With On Cable Connection, the interface is watched for any existing physical connection. With On Hotplug, the interface is set when available. It is similar to the At Boot Time option, and only diers in that no error occurs if the interface is not present at boot time. Choose Manually to control the interface manually with ifup . Choose Never to not start the device. The On NFSroot is similar to At Boot Time, but the interface does not shut down with the systemctl stop network command; the network service also cares about the wicked service if wicked is active. Use this if you use an NFS or iSCSI root le system. 3. To activate the conguration, conrm the settings. Tip: NFS as a Root File System On (diskless) systems where the root partition is mounted via network as an NFS share, you need to be careful when conguring the network device with which the NFS share is accessible. When shutting down or rebooting the system, the default processing order is to turn o network connections, then unmount the root partition. With NFS root, this order causes problems as the root partition cannot be cleanly unmounted as the network connection to the NFS share is already not activated. To prevent the system from deactivating the relevant network device, open the network device conguration tab as described in Section 16.4.1.2.5, “Activating the Network Device” and choose On NFSroot in the Device Activation pane. 221 Configuring the Network Card with YaST SLES 12 SP416.4.1.2.6 Setting Up Maximum Transfer Unit Size You can set a maximum transmission unit (MTU) for the interface. MTU refers to the largest allowed packet size in bytes. A higher MTU brings higher bandwidth eciency. However, large packets can block up a slow interface for some time, increasing the lag for further packets. 1. In YaST select a card from the list of detected cards in System Network Settings and click Edit. 2. In the General tab, select the desired entry from the Set MTU list. 3. To activate the conguration, conrm the settings. 16.4.1.2.7 PCIe Multifunction Devices Multifunction devices that support LAN, iSCSI, and FCoE are supported. The YaST FCoE client ( yast2 fcoe-client ) shows the private ags in additional columns to allow the user to select the device meant for FCoE. The YaST network module ( yast2 lan ) excludes “storage only devices” for network conguration. For more information about FCoE, see Book “Storage Administration Guide”, Chapter  15 “Fibre Channel Storage over Ethernet Networks: FCoE”, Section 15.3 “Managing FCoE Services with YaST”. 16.4.1.2.8 Infiniband Configuration for IP-over-InfiniBand (IPoIB) 1. In YaST select the InniBand device in System Network Settings and click Edit. 2. In the General tab, select one of the IP-over-InniBand (IPoIB) modes: connected (default) or datagram. 3. To activate the conguration, conrm the settings. For more information about InniBand, see /usr/src/linux/Documentation/infiniband/ ipoib.txt . 222 Configuring the Network Card with YaST SLES 12 SP416.4.1.2.9 Configuring the Firewall Without having to enter the detailed rewall setup as described in Book “Security Guide”, Chapter 15 “Masquerading and Firewalls”, Section 15.4.1 “Configuring the Firewall with YaST”, you can determine the basic rewall conguration for your device as part of the device setup. Proceed as follows: 1. Open the YaST System Network Settings module. In the Overview tab, select a card from the list of detected cards and click Edit. 2. Enter the General tab of the Network Settings dialog. 3. Determine the Firewall Zone to which your interface should be assigned. The following options are available: Firewall Disabled This option is available only if the rewall is disabled and the rewall does not run. Only use this option if your machine is part of a greater network that is protected by an outer rewall. Automatically Assign Zone This option is available only if the rewall is enabled. The rewall is running and the interface is automatically assigned to a rewall zone. The zone which contains the keyword any or the external zone will be used for such an interface. Internal Zone (Unprotected) The rewall is running, but does not enforce any rules to protect this interface. Use this option if your machine is part of a greater network that is protected by an outer rewall. It is also useful for the interfaces connected to the internal network, when the machine has more network interfaces. Demilitarized Zone A demilitarized zone is an additional line of defense in front of an internal network and the (hostile) Internet. Hosts assigned to this zone can be reached from the internal network and from the Internet, but cannot access the internal network. External Zone The rewall is running on this interface and fully protects it against other— presumably hostile—network trac. This is the default option. 4. To activate the conguration, conrm the settings. 223 Configuring the Network Card with YaST SLES 12 SP416.4.1.3 Configuring an Undetected Network Card If a network card is not detected correctly, the card is not included in the list of detected cards. If you are sure that your system includes a driver for your card, you can congure it manually. You can also congure special network device types, such as bridge, bond, TUN or TAP. To congure an undetected network card (or a special device) proceed as follows: 1. In the System Network Settings Overview dialog in YaST click Add. 2. In the Hardware dialog, set the Device Type of the interface from the available options and Conguration Name. If the network card is a PCMCIA or USB device, activate the respective check box and exit this dialog with Next. Otherwise, you can dene the kernel Module Name to be used for the card and its Options, if necessary. In Ethtool Options, you can set ethtool options used by ifup for the interface. For information about available options, see the ethtool manual page. If the option string starts with a - (for example, -K INTERFACE_NAME rx on ), the second word in the string is replaced with the current interface name. Otherwise (for example, autoneg off speed 10 ) ifup adds -s INTERFACE_NAME to the beginning. 3. Click Next. 4. Congure any needed options, such as the IP address, device activation or rewall zone for the interface in the General, Address, and Hardware tabs. For more information about the conguration options, see Section 16.4.1.2, “Changing the Configuration of a Network Card”. 5. If you selected Wireless as the device type of the interface, congure the wireless connection in the next dialog. 6. To activate the new network conguration, conrm the settings. 16.4.1.4 Configuring Host Name and DNS If you did not change the network conguration during installation and the Ethernet card was already available, a host name was automatically generated for your computer and DHCP was activated. The same applies to the name service information your host needs to integrate into a network environment. If DHCP is used for network address setup, the list of domain name servers is automatically lled with the appropriate data. If a static setup is preferred, set these values manually. 224 Configuring the Network Card with YaST SLES 12 SP4To change the name of your computer and adjust the name server search list, proceed as follows: 1. Go to the Network Settings Hostname/DNS tab in the System module in YaST. 2. Enter the Hostname and, if needed, the Domain Name. The domain is especially important if the machine is a mail server. Note that the host name is global and applies to all set network interfaces. If you are using DHCP to get an IP address, the host name of your computer will be automatically set by the DHCP. You should disable this behavior if you connect to dierent networks, because they may assign dierent host names and changing the host name at runtime may confuse the graphical desktop. To disable using DHCP to get an IP address deactivate Change Hostname via DHCP. Assign Hostname to Loopback IP associates your host name with 127.0.0.2 (loopback) IP address in /etc/hosts . This is a useful option if you want to have the host name resolvable at all times, even without active network. 3. In Modify DNS Conguration, select the way the DNS conguration (name servers, search list, the content of the /etc/resolv.conf le) is modied. If the Use Default Policy option is selected, the conguration is handled by the netconfig script which merges the data dened statically (with YaST or in the conguration les) with data obtained dynamically (from the DHCP client or NetworkManager). This default policy is usually sucient. If the Only Manually option is selected, netconfig is not allowed to modify the /etc/ resolv.conf le. However, this le can be edited manually. If the Custom Policy option is selected, a Custom Policy Rule string dening the merge policy should be specied. The string consists of a comma-separated list of interface names to be considered a valid source of settings. Except for complete interface names, basic wild cards to match multiple interfaces are allowed, as well. For example, eth* ppp? will rst target all eth and then all ppp0-ppp9 interfaces. There are two special policy values that indicate how to apply the static settings dened in the /etc/sysconfig/network/config le: STATIC The static settings need to be merged together with the dynamic settings. STATIC_FALLBACK The static settings are used only when no dynamic conguration is available. For more information, see the man page of netconfig (8) ( man 8 netconfig ). 225 Configuring the Network Card with YaST SLES 12 SP44. Enter the Name Servers and ll in the Domain Search list. Name servers must be specied by IP addresses, such as 192.168.1.116, not by host names. Names specied in the Domain Search tab are domain names used for resolving host names without a specied domain. If more than one Domain Search is used, separate domains with commas or white space. 5. To activate the conguration, conrm the settings. It is also possible to edit the host name using YaST from the command line. The changes made by YaST take eect immediately (which is not the case when editing the /etc/HOSTNAME le manually). To change the host name, use the following command: yast dns edit hostname=HOSTNAME To change the name servers, use the following commands: yast dns edit nameserver1=192.168.1.116 yast dns edit nameserver2=192.168.1.117 yast dns edit nameserver3=192.168.1.118 16.4.1.5 Configuring Routing To make your machine communicate with other machines and other networks, routing information must be given to make network trac take the correct path. If DHCP is used, this information is automatically provided. If a static setup is used, this data must be added manually. 1. In YaST go to Network Settings Routing. 2. Enter the IP address of the Default Gateway (IPv4 and IPv6 if necessary). The default gateway matches every possible destination, but if a routing table entry exists that matches the required address, this will be used instead of the default route via the Default Gateway. 3. More entries can be entered in the Routing Table. Enter the Destination network IP address, Gateway IP address and the Netmask. Select the Device through which the trac to the dened network will be routed (the minus sign stands for any device). To omit any of these values, use the minus sign - . To enter a default gateway into the table, use default in the Destination eld. 226 Configuring the Network Card with YaST SLES 12 SP4Note: Route Prioritization If more default routes are used, it is possible to specify the metric option to determine which route has a higher priority. To specify the metric option, enter - metric NUMBER in Options. The route with the highest metric is used as default. If the network device is disconnected, its route will be removed and the next one will be used. 4. If the system is a router, enable IPv4 Forwarding and IPv6 Forwarding in the Network Settings as needed. 5. To activate the conguration, conrm the settings. 16.4.2 IBM z Systems: Configuring Network Devices SUSE Linux Enterprise Server for IBM z Systems supports several types of network interfaces. YaST can be used to congure all of them. 16.4.2.1 The qeth-hsi Device To add a qeth-hsi (Hipersockets) interface to the installed system, start the System Network Settings module in YaST. Select one of the devices marked Hipersocket to use as the READ device address and click Edit. Enter the device numbers for the read, write and control channels (example device number format: 0.0.0800 ). Then click next. In the Network Address Setup dialog, specify the IP address and netmask for the new interface and leave the network conguration by clicking Next and OK. 16.4.2.2 The qeth-ethernet Device To add a qeth-ethernet (IBM OSA Express Ethernet Card) interface to the installed system, start the System Network Settings module in YaST. Select one of the devices marked IBM OSA Express Ethernet Card to use as the READ device address and click Edit. Enter a device number for the read, write and control channels (example device number format: 0.0.0700 ). Enter the needed port name, port number (if applicable) and some additional options (see the Linux for 227 IBM z Systems: Configuring Network Devices SLES 12 SP4IBM z Systems: Device Drivers, Features, and Commands manual for reference, http://www.ibm.com/ developerworks/linux/linux390/documentation_suse.html ), your IP address, and an appropriate netmask. Leave the network conguration with Next and OK. 16.4.2.3 The ctc Device To add a ctc (IBM parallel CTC Adapter) interface to the installed system, start the System Network Settings module in YaST. Select one of the devices marked IBM Parallel CTC Adapter to use as your read channel and click Congure. Choose the Device Settings that t your devices (usually this would be Compatibility Mode). Specify both your IP address and the IP address of the remote partner. If needed, adjust the MTU size with Advanced Detailed Settings. Leave the network conguration with Next and OK. Warning: CTC is no Longer Supported The use of this interface is deprecated. This interface will not be supported in future versions of SUSE Linux Enterprise Server. 16.4.2.4 The lcs Device To add an lcs (IBM OSA-2 Adapter) interface to the installed system, start the System Network Settings module in YaST. Select one of the devices marked IBM OSA-2 Adapter and click Congure. Enter the needed port number, some additional options (see the Linux for IBM z Systems: Device Drivers, Features, and Commands manual for reference, http://www.ibm.com/developerworks/ linux/linux390/documentation_suse.html ), your IP address and an appropriate netmask. Leave the network conguration with Next and OK. 16.4.2.5 The IUCV Device To add an iucv (IUCV) interface to the installed system, start the System Network Settings module in YaST. Select a device marked IUCV and click Edit. YaST prompts you for the name of your IUCV partner (Peer). Enter the name (this entry is case-sensitive) and select Next. Specify both the IP Address and the Remote IP Address of your partner. If needed, Set MTU size on General tab. Leave the network conguration with Next and OK. 228 IBM z Systems: Configuring Network Devices SLES 12 SP4Warning: IUCV is no Longer Supported The use of this interface is deprecated. This interface will not be supported in future versions of SUSE Linux Enterprise Server. 16.5 Configuring a Network Connection Manually Manual conguration of the network software should be the last alternative. Using YaST is recommended. However, this background information about the network conguration can also assist your work with YaST. 16.5.1 The wicked Network Configuration The tool and library called wicked provides a new framework for network conguration. One of the challenges with traditional network interface management is that dierent layers of network management get jumbled together into one single script, or at most two dierent scripts. These scripts interact with each other in a way that is not well-dened. This leads to unpredictable issues, obscure constraints and conventions, etc. Several layers of special hacks for a variety of dierent scenarios increase the maintenance burden. Address conguration protocols are being used that are implemented via daemons like dhcpcd, which interact rather poorly with the rest of the infrastructure. Funky interface naming schemes that require heavy udev support are introduced to achieve persistent identication of interfaces. The idea of wicked is to decompose the problem in several ways. None of them is entirely novel, but trying to put ideas from dierent projects together is hopefully going to create a better solution overall. One approach is to use a client/server model. This allows wicked to dene standardized facilities for things like address conguration that are well integrated with the overall framework. For example, using a specic address conguration, the administrator may request that an interface should be congured via DHCP or IPv4 zeroconf. In this case, the address conguration service simply obtains the lease from its server and passes it on to the wicked server process that installs the requested addresses and routes. 229 Configuring a Network Connection Manually SLES 12 SP4The other approach to decomposing the problem is to enforce the layering aspect. For any type of network interface, it is possible to dene a dbus service that congures the network interface''s device layer—a VLAN, a bridge, a bonding, or a paravirtualized device. Common functionality, such as address conguration, is implemented by joint services that are layered on top of these device specic services without having to implement them specically. The wicked framework implements these two aspects by using a variety of dbus services, which get attached to a network interface depending on its type. Here is a rough overview of the current object hierarchy in wicked. Each network interface is represented via a child object of /org/opensuse/Network/ Interfaces . The name of the child object is given by its index. For example, the loopback interface, which usually gets index 1, is /org/opensuse/Network/Interfaces/1 , the rst Ethernet interface registered is /org/opensuse/Network/Interfaces/2 . Each network interface has a “class” associated with it, which is used to select the dbus interfaces it supports. By default, each network interface is of class netif , and wickedd will automatically attach all interfaces compatible with this class. In the current implementation, this includes the following interfaces: org.opensuse.Network.Interface Generic network interface functions, such as taking the link up or down, assigning an MTU, etc. org.opensuse.Network.Addrconf.ipv4.dhcp, org.opensuse.Network.Addrconf.ipv6.dhcp, org.opensuse.Network.Addrconf.ipv4.auto Address conguration services for DHCP, IPv4 zeroconf, etc. Beyond this, network interfaces may require or oer special conguration mechanisms. For an Ethernet device, for example, you should be able to control the link speed, ooading of checksumming, etc. To achieve this, Ethernet devices have a class of their own, called netif-ethernet , which is a subclass of netif . As a consequence, the dbus interfaces assigned to an Ethernet interface include all the services listed above, plus the org.opensuse.Network.Ethernet service available only to objects belonging to the netif- ethernet class. Similarly, there exist classes for interface types like bridges, VLANs, bonds, or innibands. 230 The wicked Network Configuration SLES 12 SP4How do you interact with an interface like VLAN (which is really a virtual network interface that sits on top of an Ethernet device) that needs to be created rst? For this, wicked denes factory interfaces, such as org.opensuse.Network.VLAN.Factory . Such a factory interface oers a single function that lets you create an interface of the requested type. These factory interfaces are attached to the /org/opensuse/Network/Interfaces list node. 16.5.1.1 wicked Architecture and Features The wicked service comprises several parts as depicted in Figure 16.4, “wicked architecture”. FIGURE 16.4: wicked ARCHITECTURE wicked currently supports the following: Conguration le back-ends to parse SUSE style /etc/sysconfig/network les. An internal conguration back-end to represent network interface conguration in XML. Bring up and shutdown of “normal” network interfaces such as Ethernet or InniBand, VLAN, bridge, bonds, tun, tap, dummy, macvlan, macvtap, hsi, qeth, iucv, and wireless (currently limited to one wpa-psk/eap network) devices. A built-in DHCPv4 client and a built-in DHCPv6 client. 231 The wicked Network Configuration SLES 12 SP4The nanny daemon (enabled by default) helps to automatically bring up congured interfaces when the device is available (interface hotplugging) and set up the IP conguration when a link (carrier) is detected. See Section  16.5.1.3, “Nanny” for more information. wicked was implemented as a group of DBus services that are integrated with systemd. So the usual systemctl commands will apply to wicked . 16.5.1.2 Using wicked On SUSE Linux Enterprise, wicked runs by default. If you want to check what is currently enabled and whether it is running, call: systemctl status network If wicked is enabled, you will see something along these lines: wicked.service - wicked managed network interfaces Loaded: loaded (/usr/lib/systemd/system/wicked.service; enabled) ... In case something dierent is running (for example, NetworkManager) and you want to switch to wicked , rst stop what is running and then enable wicked : systemctl is-active network && \ systemctl stop network systemctl enable --force wicked This enables the wicked services, creates the network.service to wicked.service alias link, and starts the network at the next boot. Starting the server process: systemctl start wickedd This starts wickedd (the main server) and associated supplicants: /usr/lib/wicked/bin/wickedd-auto4 --systemd --foreground /usr/lib/wicked/bin/wickedd-dhcp4 --systemd --foreground /usr/lib/wicked/bin/wickedd-dhcp6 --systemd --foreground /usr/sbin/wickedd --systemd --foreground /usr/sbin/wickedd-nanny --systemd --foreground 232 The wicked Network Configuration SLES 12 SP4Then bringing up the network: systemctl start wicked Alternatively use the network.service alias: systemctl start network These commands are using the default or system conguration sources as dened in /etc/ wicked/client.xml . To enable debugging, set WICKED_DEBUG in /etc/sysconfig/network/config , for example: WICKED_DEBUG="all" Or, to omit some: WICKED_DEBUG="all,-dbus,-objectmodel,-xpath,-xml" Use the client utility to display interface information for all interfaces or the interface specied with IFNAME : wicked show all wicked show IFNAME In XML output: wicked show-xml all wicked show-xml IFNAME Bringing up one interface: wicked ifup eth0 wicked ifup wlan0 ... Because there is no conguration source specied, the wicked client checks its default sources of conguration dened in /etc/wicked/client.xml : 1. firmware: iSCSI Boot Firmware Table (iBFT) 2. compat: ifcfg les—implemented for compatibility Whatever wicked gets from those sources for a given interface is applied. The intended order of importance is firmware , then compat—this may be changed in the future. 233 The wicked Network Configuration SLES 12 SP4For more information, see the wicked man page. 16.5.1.3 Nanny Nanny is an event and policy driven daemon that is responsible for asynchronous or unsolicited scenarios such as hotplugging devices. Thus the nanny daemon helps with starting or restarting delayed or temporarily gone devices. Nanny monitors device and link changes, and integrates new devices dened by the current policy set. Nanny continues to set up even if ifup already exited because of specied timeout constraints. By default, the nanny daemon is active on the system. It is enabled in the /etc/wicked/ common.xml conguration le: ... true This setting causes ifup and ifreload to apply a policy with the eective conguration to the nanny daemon; then, nanny congures wickedd and thus ensures hotplug support. It waits in the background for events or changes (such as new devices or carrier on). 16.5.1.4 Bringing Up Multiple Interfaces For bonds and bridges, it may make sense to dene the entire device topology in one le (ifcfg- bondX), and bring it up in one go. wicked then can bring up the whole conguration if you specify the top level interface names (of the bridge or bond): wicked ifup br0 This command automatically sets up the bridge and its dependencies in the appropriate order without the need to list the dependencies (ports, etc.) separately. To bring up multiple interfaces in one command: wicked ifup bond0 br0 br1 br2 Or also all interfaces: wicked ifup all 234 The wicked Network Configuration SLES 12 SP416.5.1.5 Using Tunnels with Wicked When you need to use tunnels with Wicked, the TUNNEL_DEVICE is used for this. It permits to specify an optional device name to bind the tunnel to the device. The tunneled packets will only be routed via this device. For more information, refer to man 5 ifcfg-tunnel . 16.5.1.6 Handling Incremental Changes With wicked , there is no need to actually take down an interface to recongure it (unless it is required by the kernel). For example, to add another IP address or route to a statically congured network interface, add the IP address to the interface denition, and do another “ifup” operation. The server will try hard to update only those settings that have changed. This applies to link-level options such as the device MTU or the MAC address, and network-level settings, such as addresses, routes, or even the address conguration mode (for example, when moving from a static conguration to DHCP). Things get tricky of course with virtual interfaces combining several real devices such as bridges or bonds. For bonded devices, it is not possible to change certain parameters while the device is up. Doing that will result in an error. However, what should still work, is the act of adding or removing the child devices of a bond or bridge, or choosing a bond''s primary interface. 16.5.1.7 Wicked Extensions: Address Configuration wicked is designed to be extensible with shell scripts. These extensions can be dened in the config.xml le. Currently, several classes of extensions are supported: link conguration: these are scripts responsible for setting up a device''s link layer according to the conguration provided by the client, and for tearing it down again. address conguration: these are scripts responsible for managing a device''s address conguration. Usually address conguration and DHCP are managed by wicked itself, but can be implemented by means of extensions. rewall extension: these scripts can apply rewall rules. 235 The wicked Network Configuration SLES 12 SP4Typically, extensions have a start and a stop command, an optional “pid le”, and a set of environment variables that get passed to the script. To illustrate how this is supposed to work, look at a rewall extension dened in etc/ server.xml : The extension is attached to the tag and denes commands to execute for the actions of this interface. Further, the declaration can dene and initialize environment variables passed to the actions. 16.5.1.8 Wicked Extensions: Configuration Files You can extend the handling of conguration les with scripts as well. For example, DNS updates from leases are ultimately handled by the extensions/resolver script, with behavior congured in server.xml : When an update arrives in wickedd , the system updater routines parse the lease and call the appropriate commands ( backup , install , etc.) in the resolver script. This in turn congures the DNS settings using /sbin/netconfig , or by manually writing /etc/resolv.conf as a fallback. 16.5.2 Configuration Files This section provides an overview of the network conguration les and explains their purpose and the format used. 236 Configuration Files SLES 12 SP416.5.2.1 /etc/wicked/common.xml The /etc/wicked/common.xml le contains common denitions that should be used by all applications. It is sourced/included by the other conguration les in this directory. Although you can use this le to enable debugging across all wicked components, we recommend to use the le /etc/wicked/local.xml for this purpose. After applying maintenance updates you might lose your changes as the /etc/wicked/common.xml might be overwritten. The /etc/ wicked/common.xml le includes the /etc/wicked/local.xml in the default installation, thus you typically do not need to modify the /etc/wicked/common.xml . In case you want to disable nanny by setting the to false , restart the wickedd.service and then run the following command to apply all congurations and policies: wicked ifup all Note: Configuration Files The wickedd , wicked , or nanny programs try to read /etc/wicked/common.xml if their own conguration les do not exist. 16.5.2.2 /etc/wicked/server.xml The le /etc/wicked/server.xml is read by the wickedd server process at start-up. The le stores extensions to the /etc/wicked/common.xml . On top of that this le congures handling of a resolver and receiving information from addrconf supplicants, for example DHCP. We recommend to add changes required to this le into a separate le /etc/wicked/server- local.xml , that gets included by /etc/wicked/server.xml . By using a separate le you avoid overwriting of your changes during maintenance updates. 16.5.2.3 /etc/wicked/client.xml The /etc/wicked/client.xml is used by the wicked command. The le species the location of a script used when discovering devices managed by ibft and congures locations of network interface congurations. We recommend to add changes required to this le into a separate le /etc/wicked/client- local.xml , that gets included by /etc/wicked/server.xml . By using a separate le you avoid overwriting of your changes during maintenance updates. 237 Configuration Files SLES 12 SP416.5.2.4 /etc/wicked/nanny.xml The /etc/wicked/nanny.xml congures types of link layers. We recommend to add specic conguration into a separate le: /etc/wicked/nanny-local.xml to avoid losing the changes during maintenance updates. 16.5.2.5 /etc/sysconfig/network/ifcfg-* These les contain the traditional congurations for network interfaces. In SUSE Linux Enterprise 11, this was the only supported format besides iBFT rmware. Note: wicked and the ifcfg-* Files wicked reads these les if you specify the compat: prex. According to the SUSE Linux Enterprise Server default conguration in /etc/wicked/client.xml , wicked tries these les before the XML conguration les in /etc/wicked/ifconfig . The --ifconfig switch is provided mostly for testing only. If specied, default conguration sources dened in /etc/wicked/ifconfig are not applied. The ifcfg-* les include information such as the start mode and the IP address. Possible parameters are described in the manual page of ifup . Additionally, most variables from the dhcp and wireless les can be used in the ifcfg-* les if a general setting should be used for only one interface. However, most of the /etc/sysconfig/network/config variables are global and cannot be overridden in ifcfg-les. For example, NETCONFIG_* variables are global. For conguring macvlan and macvtab interfaces, see the ifcfg-macvlan and ifcfg- macvtap man pages. For example, for a macvlan interface provide a ifcfg-macvlan0 with settings as follows: STARTMODE=''auto'' MACVLAN_DEVICE=''eth0'' #MACVLAN_MODE=''vepa'' #LLADDR=02:03:04:05:06:aa For ifcfg.template , see Section  16.5.2.6, “/etc/sysconfig/network/config, /etc/ sysconfig/network/dhcp, and /etc/sysconfig/network/wireless”. IBM Z IBM z Systems does not support USB. The names of the interface les and network aliases contain z Systems-specic elements like qeth . 238 Configuration Files SLES 12 SP416.5.2.6 /etc/sysconfig/network/config, /etc/sysconfig/network/ dhcp, and /etc/sysconfig/network/wireless The le config contains general settings for the behavior of ifup , ifdown and ifstatus . dhcp contains settings for DHCP and wireless for wireless LAN cards. The variables in all three conguration les are commented. Some variables from /etc/sysconfig/network/config can also be used in ifcfg-* les, where they are given a higher priority. The /etc/sysconfig/ network/ifcfg.template le lists variables that can be specied in a per interface scope. However, most of the /etc/sysconfig/network/config variables are global and cannot be overridden in ifcfg-les. For example, NETWORKMANAGER or NETCONFIG_* variables are global. Note: Using DHCPv6 In SUSE Linux Enterprise  11, DHCPv6 used to work even on networks where IPv6 Router Advertisements (RAs) were not congured properly. Starting with SUSE Linux Enterprise  12, DHCPv6 will correctly require that at least one of the routers on the network sends out RAs that indicate that this network is managed by DHCPv6. For networks where the router cannot be congured correctly, the ifcfg option allows the user to override this behavior by specifying DHCLIENT6_MODE=''managed'' in the ifcfg le. You can also activate this workaround with a boot parameter in the installation system: ifcfg=eth0=dhcp6,DHCLIENT6_MODE=managed 16.5.2.7 /etc/sysconfig/network/routes and /etc/sysconfig/ network/ifroute-* The static routing of TCP/IP packets is determined by the /etc/sysconfig/network/routes and /etc/sysconfig/network/ifroute-* les. All the static routes required by the various system tasks can be specied in /etc/sysconfig/network/routes : routes to a host, routes to a host via a gateway and routes to a network. For each interface that needs individual routing, dene an additional conguration le: /etc/sysconfig/network/ifroute-* . Replace the wild card ( * ) with the name of the interface. The entries in the routing conguration les look like this: # Destination Gateway Netmask Interface Options 239 Configuration Files SLES 12 SP4The route''s destination is in the rst column. This column may contain the IP address of a network or host or, in the case of reachable name servers, the fully qualied network or host name. The network should be written in CIDR notation (address with the associated routing prex-length) such as 10.10.0.0/16 for IPv4 or fc00::/7 for IPv6 routes. The keyword default indicates that the route is the default gateway in the same address family as the gateway. For devices without a gateway use explicit 0.0.0.0/0 or ::/0 destinations. The second column contains the default gateway or a gateway through which a host or network can be accessed. The third column is deprecated; it used to contain the IPv4 netmask of the destination. For IPv6 routes, the default route, or when using a prex-length (CIDR notation) in the rst column, enter a dash ( - ) here. The fourth column contains the name of the interface. If you leave it empty using a dash ( - ), it can cause unintended behavior in /etc/sysconfig/network/routes . For more information, see the routes man page. An (optional) fth column can be used to specify special options. For details, see the routes man page. EXAMPLE 16.5: COMMON NETWORK INTERFACES AND SOME STATIC ROUTES # --- IPv4 routes in CIDR prefix notation: # Destination [Gateway] - Interface 127.0.0.0/8 - - lo 204.127.235.0/24 - - eth0 default 204.127.235.41 - eth0 207.68.156.51/32 207.68.145.45 - eth1 192.168.0.0/16 207.68.156.51 - eth1 # --- IPv4 routes in deprecated netmask notation" # Destination [Dummy/Gateway] Netmask Interface # 127.0.0.0 0.0.0.0 255.255.255.0 lo 204.127.235.0 0.0.0.0 255.255.255.0 eth0 default 204.127.235.41 0.0.0.0 eth0 207.68.156.51 207.68.145.45 255.255.255.255 eth1 192.168.0.0 207.68.156.51 255.255.0.0 eth1 # --- IPv6 routes are always using CIDR notation: # Destination [Gateway] - Interface 2001:DB8:100::/64 - - eth0 240 Configuration Files SLES 12 SP42001:DB8:100::/32 fe80::216:3eff:fe6d:c042 - eth0 16.5.2.8 /etc/resolv.conf The domain to which the host belongs is specied in /etc/resolv.conf (keyword search ). Up to six domains with a total of 256 characters can be specied with the search option. When resolving a name that is not fully qualied, an attempt is made to generate one by attaching the individual search entries. Up to 3 name servers can be specied with the nameserver option, each on a line of its own. Comments are preceded by hash mark or semicolon signs ( # or ; ). As an example, see Example 16.6, “/etc/resolv.conf”. However, the /etc/resolv.conf should not be edited by hand. Instead, it is generated by the netconfig script. To dene static DNS conguration without using YaST, edit the appropriate variables manually in the /etc/sysconfig/network/config le: NETCONFIG_DNS_STATIC_SEARCHLIST list of DNS domain names used for host name lookup NETCONFIG_DNS_STATIC_SERVERS list of name server IP addresses to use for host name lookup NETCONFIG_DNS_FORWARDER the name of the DNS forwarder that needs to be congured, for example bind or resolver NETCONFIG_DNS_RESOLVER_OPTIONS arbitrary options that will be written to /etc/resolv.conf , for example: debug attempts:1 timeout:10 For more information, see the resolv.conf man page. NETCONFIG_DNS_RESOLVER_SORTLIST list of up to 10 items, for example: 130.155.160.0/255.255.240.0 130.155.0.0 For more information, see the resolv.conf man page. To disable DNS conguration using netcong, set NETCONFIG_DNS_POLICY='''' . For more information about netconfig , see the netconfig(8) man page ( man 8 netconfig ). 241 Configuration Files SLES 12 SP4EXAMPLE 16.6: /etc/resolv.conf # Our domain search example.com # # We use dns.example.com (192.168.1.116) as nameserver nameserver 192.168.1.116 16.5.2.9 /sbin/netconfig netconfig is a modular tool to manage additional network conguration settings. It merges statically dened settings with settings provided by autoconguration mechanisms as DHCP or PPP according to a predened policy. The required changes are applied to the system by calling the netcong modules that are responsible for modifying a conguration le and restarting a service or a similar action. netconfig recognizes three main actions. The netconfig modify and netconfig remove commands are used by daemons such as DHCP or PPP to provide or remove settings to netcong. Only the netconfig update command is available for the user: modify The netconfig modify command modies the current interface and service specic dynamic settings and updates the network conguration. Netcong reads settings from standard input or from a le specied with the --lease-file FILENAME option and internally stores them until a system reboot (or the next modify or remove action). Already existing settings for the same interface and service combination are overwritten. The interface is specied by the -i INTERFACE_NAME parameter. The service is specied by the -s SERVICE_NAME parameter. remove The netconfig remove command removes the dynamic settings provided by a modicatory action for the specied interface and service combination and updates the network conguration. The interface is specied by the -i INTERFACE_NAME parameter. The service is specied by the -s SERVICE_NAME parameter. update The netconfig update command updates the network conguration using current settings. This is useful when the policy or the static conguration has changed. Use the -m MODULE_TYPE parameter, if you want to update a specied service only ( dns , nis , or ntp ). 242 Configuration Files SLES 12 SP4The netcong policy and the static conguration settings are dened either manually or using YaST in the /etc/sysconfig/network/config le. The dynamic conguration settings provided by autoconguration tools such as DHCP or PPP are delivered directly by these tools with the netconfig modify and netconfig remove actions. When NetworkManager is enabled, netcong (in policy mode auto ) uses only NetworkManager settings, ignoring settings from any other interfaces congured using the traditional ifup method. If NetworkManager does not provide any setting, static settings are used as a fallback. A mixed usage of NetworkManager and the wicked method is not supported. For more information about netconfig , see man 8 netconfig . 16.5.2.10 /etc/hosts In this le, shown in Example 16.7, “/etc/hosts”, IP addresses are assigned to host names. If no name server is implemented, all hosts to which an IP connection will be set up must be listed here. For each host, enter a line consisting of the IP address, the fully qualied host name, and the host name into the le. The IP address must be at the beginning of the line and the entries separated by blanks and tabs. Comments are always preceded by the # sign. EXAMPLE 16.7: /etc/hosts 127.0.0.1 localhost 192.168.2.100 jupiter.example.com jupiter 192.168.2.101 venus.example.com venus 16.5.2.11 /etc/networks Here, network names are converted to network addresses. The format is similar to that of the hosts le, except the network names precede the addresses. See Example 16.8, “/etc/networks”. EXAMPLE 16.8: /etc/networks loopback 127.0.0.0 localnet 192.168.0.0 243 Configuration Files SLES 12 SP416.5.2.12 /etc/host.conf Name resolution—the translation of host and network names via the resolver library—is controlled by this le. This le is only used for programs linked to libc4 or libc5. For current glibc programs, refer to the settings in /etc/nsswitch.conf . Each parameter must always be entered on a separate line. Comments are preceded by a # sign. Table 16.2, “Parameters for /etc/ host.conf” shows the parameters available. A sample /etc/host.conf is shown in Example 16.9, “/etc/host.conf”. TABLE 16.2: PARAMETERS FOR /ETC/HOST.CONF order hosts, bind Species in which order the services are accessed for the name resolution. Available arguments are (separated by blank spaces or commas): hosts: searches the /etc/hosts le bind: accesses a name server nis: uses NIS multi on/o Denes if a host entered in /etc/hosts can have multiple IP addresses. nospoof on spoofalert on/o These parameters inuence the name server spoong but do not exert any inuence on the network conguration. trim domainname The specied domain name is separated from the host name after host name resolution (as long as the host name includes the domain name). This option is useful only if names from the local domain are in the /etc/ hosts le, but should still be recognized with the attached domain names. EXAMPLE 16.9: /etc/host.conf # We have named running order hosts bind 244 Configuration Files SLES 12 SP4# Allow multiple address multi on 16.5.2.13 /etc/nsswitch.conf The introduction of the GNU C Library 2.0 was accompanied by the introduction of the Name Service Switch (NSS). Refer to the nsswitch.conf(5) man page and The GNU C Library Reference Manual for details. The order for queries is dened in the le /etc/nsswitch.conf . A sample nsswitch.conf is shown in Example 16.10, “/etc/nsswitch.conf”. Comments are preceded by # signs. In this example, the entry under the hosts database means that a request is sent to /etc/hosts ( files ) via DNS (see Chapter 26, The Domain Name System). EXAMPLE 16.10: /etc/nsswitch.conf passwd: compat group: compat hosts: files dns networks: files dns services: db files protocols: db files rpc: files ethers: files netmasks: files netgroup: files nis publickey: files bootparams: files automount: files nis aliases: files nis shadow: compat The “databases” available over NSS are listed in Table  16.3, “Databases Available via /etc/ nsswitch.conf”. The conguration options for NSS databases are listed in Table 16.4, “Configuration Options for NSS “Databases””. TABLE 16.3: DATABASES AVAILABLE VIA /ETC/NSSWITCH.CONF aliases Mail aliases implemented by sendmail ; see man   5 aliases . 245 Configuration Files SLES 12 SP4ethers Ethernet addresses. netmasks List of networks and their subnet masks. Only needed, if you use subnetting. group User groups used by getgrent . See also the man page for group . hosts Host names and IP addresses, used by gethostbyname and similar functions. netgroup Valid host and user lists in the network for controlling access permissions; see the netgroup(5) man page. networks Network names and addresses, used by getnetent . publickey Public and secret keys for Secure_RPC used by NFS and NIS+. passwd User passwords, used by getpwent ; see the passwd(5) man page. protocols Network protocols, used by getprotoent ; see the protocols(5) man page. rpc Remote procedure call names and addresses, used by getrpcbyname and similar functions. services Network services, used by getservent . shadow Shadow passwords of users, used by getspnam ; see the shadow(5) man page. TABLE 16.4: CONFIGURATION OPTIONS FOR NSS “DATABASES” files directly access les, for example, /etc/ aliases 246 Configuration Files SLES 12 SP4db access via a database nis , nisplus NIS, see also Book “Security Guide”, Chapter 3 “Using NIS” dns can only be used as an extension for hosts and networks compat can only be used as an extension for passwd , shadow and group 16.5.2.14 /etc/nscd.conf This le is used to congure nscd (name service cache daemon). See the nscd(8) and nscd.conf(5) man pages. By default, the system entries of passwd , groups and hosts are cached by nscd. This is important for the performance of directory services, like NIS and LDAP, because otherwise the network connection needs to be used for every access to names, groups or hosts. If the caching for passwd is activated, it usually takes about fteen seconds until a newly added local user is recognized. Reduce this waiting time by restarting nscd with: systemctl restart nscd 16.5.2.15 /etc/HOSTNAME /etc/HOSTNAME contains the fully qualied host name (FQHN). The fully qualied host name is the host name with the domain name attached. This le must contain only one line (in which the host name is set). It is read while the machine is booting. 16.5.3 Testing the Configuration Before you write your conguration to the conguration les, you can test it. To set up a test conguration, use the ip command. To test the connection, use the ping command. 247 Testing the Configuration SLES 12 SP4The command ip changes the network conguration directly without saving it in the conguration le. Unless you enter your conguration in the correct conguration les, the changed network conguration is lost on reboot. Note: ifconfig and route Are Obsolete The ifconfig and route tools are obsolete. Use ip instead. ifconfig , for example, limits interface names to 9 characters. 16.5.3.1 Configuring a Network Interface with ip ip is a tool to show and congure network devices, routing, policy routing, and tunnels. ip is a very complex tool. Its common syntax is ip  OPTIONS OBJECT COMMAND . You can work with the following objects: link This object represents a network device. address This object represents the IP address of device. neighbor This object represents an ARP or NDISC cache entry. route This object represents the routing table entry. rule This object represents a rule in the routing policy database. maddress This object represents a multicast address. mroute This object represents a multicast routing cache entry. tunnel This object represents a tunnel over IP. If no command is given, the default command is used (usually list ). 248 Testing the Configuration SLES 12 SP4Change the state of a device with the command: tux > sudo ip link set DEV_NAME For example, to deactivate device eth0, enter tux > sudo ip link set eth0 down To activate it again, use tux > sudo ip link set eth0 up Tip: Disconnecting NIC Device If you deactivate a device with tux > sudo ip link set DEV_NAME down it disables the network interface on a software level. If you want to simulate losing the link as if the ethernet cable is unplugged or the connected switch is turned o, run tux > sudo ip link set DEV_NAME carrier off For example, while ip link set DEV_NAME down drops all routes using DEV_NAME , ip link set DEV carrier off does not. Be aware that carrier off requires support from the network device driver. To connect the device back to the physical network, run tux > sudo ip link set DEV_NAME carrier on After activating a device, you can congure it. To set the IP address, use tux > sudo ip addr add IP_ADDRESS + dev DEV_NAME For example, to set the address of the interface eth0 to 192.168.12.154/30 with standard broadcast (option brd ), enter tux > sudo ip addr add 192.168.12.154/30 brd + dev eth0 To have a working connection, you must also congure the default gateway. To set a gateway for your system, enter 249 Testing the Configuration SLES 12 SP4tux > sudo ip route add default via gateway_ip_address To display all devices, use tux > sudo ip link ls To display the running interfaces only, use tux > sudo ip link ls up To print interface statistics for a device, enter tux > sudo ip -s link ls DEV_NAME To view additional useful information, specically about virtual network devices, enter tux > sudo ip -d link ls DEV_NAME Moreover, to view network layer (IPv4, IPv6) addresses of your devices, enter tux > sudo ip addr In the output, you can nd information about MAC addresses of your devices. To show all routes, use tux > sudo ip route show For more information about using ip , enter ip   help or see the man 8 ip manual page. The help option is also available for all ip subcommands, such as: tux > sudo ip addr help Find the ip manual in /usr/share/doc/packages/iproute2/ip-cref.pdf . 16.5.3.2 Testing a Connection with ping The ping command is the standard tool for testing whether a TCP/IP connection works. It uses the ICMP protocol to send a small data packet, ECHO_REQUEST datagram, to the destination host, requesting an immediate reply. If this works, ping displays a message to that eect. This indicates that the network link is functioning. ping does more than only test the function of the connection between two computers: it also provides some basic information about the quality of the connection. In Example 16.11, “Output of the Command ping”, you can see an example of the ping output. The second-to-last line contains information about the number of transmitted packets, packet loss, and total time of ping running. 250 Testing the Configuration SLES 12 SP4As the destination, you can use a host name or IP address, for example, ping   example.com or ping   192.168.3.100 . The program sends packets until you press Ctrl – C . If you only need to check the functionality of the connection, you can limit the number of the packets with the -c option. For example to limit ping to three packets, enter ping   -c 3 example.com . EXAMPLE 16.11: OUTPUT OF THE COMMAND PING ping -c 3 example.com PING example.com (192.168.3.100) 56(84) bytes of data. 64 bytes from example.com (192.168.3.100): icmp_seq=1 ttl=49 time=188 ms 64 bytes from example.com (192.168.3.100): icmp_seq=2 ttl=49 time=184 ms 64 bytes from example.com (192.168.3.100): icmp_seq=3 ttl=49 time=183 ms --- example.com ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2007ms rtt min/avg/max/mdev = 183.417/185.447/188.259/2.052 ms The default interval between two packets is one second. To change the interval, ping provides the option -i . For example, to increase the ping interval to ten seconds, enter ping   -i 10 example.com . In a system with multiple network devices, it is sometimes useful to send the ping through a specic interface address. To do so, use the -I option with the name of the selected device, for example, ping   -I wlan1 example.com . For more options and information about using ping, enter ping   -h or see the ping (8) man page. Tip: Pinging IPv6 Addresses For IPv6 addresses use the ping6 command. Note, to ping link-local addresses, you must specify the interface with -I . The following command works, if the address is reachable via eth1 : ping6 -I eth1 fe80::117:21ff:feda:a425 251 Testing the Configuration SLES 12 SP416.5.4 Unit Files and Start-Up Scripts Apart from the conguration les described above, there are also systemd unit les and various scripts that load the network services while the machine is booting. These are started when the system is switched to the multi-user.target target. Some of these unit les and scripts are described in Some Unit Files and Start-Up Scripts for Network Programs. For more information about systemd , see Chapter 13, The systemd Daemon and for more information about the systemd targets, see the man page of systemd.special ( man systemd.special ). SOME UNIT FILES AND START-UP SCRIPTS FOR NETWORK PROGRAMS network.target network.target is the systemd target for networking, but its mean depends on the settings provided by the system administrator. For more information, see http://www.freedesktop.org/wiki/Software/systemd/ NetworkTarget/ . multi-user.target multi-user.target is the systemd target for a multiuser system with all required network services. xinetd Starts xinetd. xinetd can be used to make server services available on the system. For example, it can start vsftpd whenever an FTP connection is initiated. rpcbind Starts the rpcbind utility that converts RPC program numbers to universal addresses. It is needed for RPC services, such as an NFS server. ypserv Starts the NIS server. ypbind Starts the NIS client. /etc/init.d/nfsserver Starts the NFS server. /etc/init.d/postfix Controls the postx process. 252 Unit Files and Start-Up Scripts SLES 12 SP416.6 Basic Router Setup A router is a networking device that delivers and receives data (network packets) to or from more than one network back and forth. You often use a router to connect your local network to the remote network (Internet) or to connect local network segments. With SUSE Linux Enterprise Server you can build a router with features such as NAT (Network Address Translation) or advanced rewalling. The following are basic steps to turn SUSE Linux Enterprise Server into a router. 1. Enable forwarding, for example in /etc/sysctl.d/50-router.conf net.ipv4.conf.all.forwarding = 1 net.ipv6.conf.all.forwarding = 1 Then provide a static IPv4 and IPv6 IP setup for the interfaces. Enabling forwarding disables several mechanisms, for example IPv6 does not accept an IPv6 RA (router advertisement) anymore, which also prevents the creation of a default route. 2. In many situations (for example, when you can reach the same network via more than one interface, or when VPN usually is used and already on “normal multi-home hosts”), you must disable the IPv4 reverse path lter (this feature does not currently exist for IPv6): net.ipv4.conf.all.rp_filter = 0 You can also lter with rewall settings instead. 3. To accept an IPv6 RA (from the router on an external, uplink, or ISP interface) and create a default (or also a more specic) IPv6 route again, set: net.ipv6.conf.${ifname}.accept_ra = 2 net.ipv6.conf.${ifname}.autoconf = 0 (Note: “ eth0.42 ” needs to be written as eth0/42 in a dot-separated sysfs path.) More router behavior and forwarding dependencies are described in https://www.kernel.org/doc/ Documentation/networking/ip-sysctl.txt . To provide IPv6 on your internal (DMZ) interfaces, and announce yourself as an IPv6 router and “autoconf networks” to the clients, install and congure radvd in /etc/radvd.conf , for example: interface eth0 253 Basic Router Setup SLES 12 SP4{ IgnoreIfMissing on; # do not fail if interface missed AdvSendAdvert on; # enable sending RAs AdvManagedFlag on; # IPv6 addresses managed via DHCPv6 AdvOtherConfigFlag on; # DNS, NTP... only via DHCPv6 AdvDefaultLifetime 3600; # client default route lifetime of 1 hour prefix 2001:db8:0:1::/64 # (/64 is default and required for autoconf) { AdvAutonomous off; # Disable address autoconf (DHCPv6 only) AdvValidLifetime 3600; # prefix (autoconf addr) is valid 1 h AdvPreferredLifetime 1800; # prefix (autoconf addr) is prefered 1/2 h } } Lastly congure the rewall. In SuSErewall2, you need to set FW_ROUTE="yes" (otherwise it will also reset forwarding sysctl again) and dene the interfaces in the FW_DEV_INT , FW_DEV_EXT (and FW_DEV_DMZ ) zone variables as needed, perhaps also FW_MASQUERADE="yes" and FW_MASQ_DEV . 16.7 Setting Up Bonding Devices For some systems, there is a desire to implement network connections that comply to more than the standard data security or availability requirements of a typical Ethernet device. In these cases, several Ethernet devices can be aggregated to a single bonding device. The conguration of the bonding device is done by means of bonding module options. The behavior is mainly aected by the mode of the bonding device. By default, this is active- backup which means that a dierent slave device will become active if the active slave fails. The following bonding modes are available: 0 (balance-rr) Packets are transmitted in round-robin fashion from the rst to the last available interface. Provides fault tolerance and load balancing. 1 (active-backup) Only one network interface is active. If it fails, a dierent interface becomes active. This setting is the default for SUSE Linux Enterprise Server. Provides fault tolerance. 254 Setting Up Bonding Devices SLES 12 SP42 (balance-xor) Trac is split between all available interfaces based on the following policy: [(source MAC address XOR''d with destination MAC address XOR packet type ID) modulo slave count] Requires support from the switch. Provides fault tolerance and load balancing. 3 (broadcast) All trac is broadcast on all interfaces. Requires support from the switch. Provides fault tolerance. 4 (802.3ad) Aggregates interfaces into groups that share the same speed and duplex settings. Requires ethtool support in the interface drivers, and a switch that supports and is congured for IEEE 802.3ad Dynamic link aggregation. Provides fault tolerance and load balancing. 5 (balance-tlb) Adaptive transmit load balancing. Requires ethtool support in the interface drivers but not switch support. Provides fault tolerance and load balancing. 6 (balance-alb) Adaptive load balancing. Requires ethtool support in the interface drivers but not switch support. Provides fault tolerance and load balancing. For a more detailed description of the modes, see https://www.kernel.org/doc/Documentation/ networking/bonding.txt . Tip: Bonding and Xen Using bonding devices is only of interest for machines where you have multiple real network cards available. In most congurations, this means that you should use the bonding conguration only in Dom0. Only if you have multiple network cards assigned to a VM Guest system it may also be useful to set up the bond in a VM Guest. 255 Setting Up Bonding Devices SLES 12 SP4Note: IBM POWER: Bonding modes 5 and 6 (balance-tlb / balance-alb) unsupported by ibmveth There is a conict with the tlb/alb bonding conguration and Power rmware. In short, the bonding driver in tlb/alb mode sends Ethernet Loopback packets with both the source and destination MAC addresses listed as the Virtual Ethernet MAC address. These packets are not supported by Power rmware. Therefore bonding modes 5 and 6 are unsupported by ibmveth. To congure a bonding device, use the following procedure: 1. Run YaST System Network Settings. 2. Use Add and change the Device Type to Bond. Proceed with Next. 3. Select how to assign the IP address to the bonding device. Three methods are at your disposal: No IP Address Dynamic Address (with DHCP or Zeroconf) Statically assigned IP Address Use the method that is appropriate for your environment. 256 Setting Up Bonding Devices SLES 12 SP44. In the Bond Slaves tab, select the Ethernet devices that should be included into the bond by activating the related check box. 5. Edit the Bond Driver Options and choose a bonding mode. 6. Make sure that the parameter miimon=100 is added to the Bond Driver Options. Without this parameter, the data integrity is not checked regularly. 7. Click Next and leave YaST with OK to create the device. 16.7.1 Hotplugging of Bonding Slaves In specic network environments (such as High Availability), there are cases when you need to replace a bonding slave interface with another one. The reason may be a constantly failing network device. The solution is to set up hotplugging of bonding slaves. The bond is congured as usual (according to man 5 ifcfg-bonding ), for example: ifcfg-bond0 STARTMODE=''auto'' # or ''onboot'' BOOTPROTO=''static'' IPADDR=''192.168.0.1/24'' BONDING_MASTER=''yes'' BONDING_SLAVE_0=''eth0'' BONDING_SLAVE_1=''eth1'' BONDING_MODULE_OPTS=''mode=active-backup miimon=100'' The slaves are specied with STARTMODE=hotplug and BOOTPROTO=none : ifcfg-eth0 STARTMODE=''hotplug'' BOOTPROTO=''none'' ifcfg-eth1 STARTMODE=''hotplug'' BOOTPROTO=''none'' BOOTPROTO=none uses the ethtool options (when provided), but does not set the link up on ifup eth0 . The reason is that the slave interface is controlled by the bond master. STARTMODE=hotplug causes the slave interface to join the bond automatically when it is available. 257 Hotplugging of Bonding Slaves SLES 12 SP4The udev rules in /etc/udev/rules.d/70-persistent-net.rules need to be changed to match the device by bus ID (udev KERNELS keyword equal to "SysFS BusID" as visible in hwinfo --netcard ) instead of by MAC address. This allows replacement of defective hardware (a network card in the same slot but with a dierent MAC) and prevents confusion when the bond changes the MAC address of all its slaves. For example: SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", KERNELS=="0000:00:19.0", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0" At boot time, the systemd network.service does not wait for the hotplug slaves, but for the bond to become ready, which requires at least one available slave. When one of the slave interfaces gets removed (unbind from NIC driver, rmmod of the NIC driver or true PCI hotplug remove) from the system, the kernel removes it from the bond automatically. When a new card is added to the system (replacement of the hardware in the slot), udev renames it using the bus-based persistent name rule to the name of the slave, and calls ifup for it. The ifup call automatically joins it into the bond. 16.8 Setting Up Team Devices for Network Teaming The term “link aggregation” is the general term which describes combining (or aggregating) a network connection to provide a logical layer. Sometimes you nd the terms “channel teaming”, “Ethernet bonding”, “port truncating”, etc. which are synonyms and refer to the same concept. This concept is widely known as “bonding” and was originally integrated into the Linux kernel (see Section 16.7, “Setting Up Bonding Devices” for the original implementation). The term Network Teaming is used to refer to the new implementation of this concept. The main dierence between bonding and Network Teaming is that teaming supplies a set of small kernel modules responsible for providing an interface for teamd instances. Everything else is handled in user space. This is dierent from the original bonding implementation which contains all of its functionality exclusively in the kernel. For a comparison refer to Table 16.5, “Feature Comparison between Bonding and Team”. 258 Setting Up Team Devices for Network Teaming SLES 12 SP4TABLE 16.5: FEATURE COMPARISON BETWEEN BONDING AND TEAM Feature Bonding Team broadcast, round-robin TX yes yes policy active-backup TX policy yes yes LACP (802.3ad) support yes yes hash-based TX policy yes yes user can set hash function no yes TX load-balancing support yes yes (TLB) TX load-balancing support no yes for LACP Ethtool link monitoring yes yes ARP link monitoring yes yes NS/NA (IPV6) link no yes monitoring RCU locking on TX/RX paths no yes port prio and stickiness no yes separate per-port link no yes monitoring setup multiple link monitoring limited yes setup VLAN support yes yes multiple device stacking yes yes Source: http://libteam.org/files/teamdev.pp.pdf Both implementations, bonding and Network Teaming, can be used in parallel. Network Teaming is an alternative to the existing bonding implementation. It does not replace bonding. 259 Setting Up Team Devices for Network Teaming SLES 12 SP4Network Teaming can be used for dierent use cases. The two most important use cases are explained later and involve: Load balancing between dierent network devices. Failover from one network device to another in case one of the devices should fail. Currently, there is no YaST module to support creating a teaming device. You need to congure Network Teaming manually. The general procedure is shown below which can be applied for all your Network Teaming congurations: PROCEDURE 16.1: GENERAL PROCEDURE 1. Make sure you have all the necessary packages installed. Install the packages libteam- tools , libteamdctl0 , and python-libteam . 2. Create a conguration le under /etc/sysconfig/network/ . Usually it will be ifcfg- team0 . If you need more than one Network Teaming device, give them ascending numbers. This conguration le contains several variables which are explained in the man pages (see man ifcfg and man ifcfg-team ). An example conguration can be found in your system in the le /etc/sysconfig/network/ifcfg.template . 3. Remove the conguration les of the interfaces which will be used for the teaming device (usually ifcfg-eth0 and ifcfg-eth1 ). It is recommended to make a backup and remove both les. Wicked will re-create the conguration les with the necessary parameters for teaming. 4. Optionally, check if everything is included in Wicked''s conguration le: wicked show-config 5. Start the Network Teaming device team0 : wicked ifup all team0 In case you need additional debug information, use the option --debug all after the all subcommand. 260 Setting Up Team Devices for Network Teaming SLES 12 SP46. Check the status of the Network Teaming device. This can be done by the following commands: Get the state of the teamd instance from Wicked: wicked ifstatus --verbose team0 Get the state of the entire instance: teamdctl team0 state Get the systemd state of the teamd instance: systemctl status teamd@team0 Each of them shows a slightly dierent view depending on your needs. 7. In case you need to change something in the ifcfg-team0 le afterward, reload its conguration with: wicked ifreload team0 Do not use systemctl for starting or stopping the teaming device! Instead, use the wicked command as shown above. To completely remove the team device, use this procedure: PROCEDURE 16.2: REMOVING A TEAM DEVICE 1. Stop the Network Teaming device team0 : wicked ifdown team0 2. Rename the le /etc/sysconfig/network/ifcfg-team0 to /etc/sysconfig/ network/.ifcfg-team0 . Inserting a dot in front of the le name makes it “invisible” for wicked. If you really do not need the conguration anymore, you can also remove the le. 3. Reload the conguration: wicked ifreload all 261 Setting Up Team Devices for Network Teaming SLES 12 SP416.8.1 Use Case: Loadbalancing with Network Teaming Loadbalancing is used to improve bandwidth. Use the following conguration le to create a Network Teaming device with loadbalancing capabilities. Proceed with Procedure 16.1, “General Procedure” to set up the device. Check the output with teamdctl . EXAMPLE 16.12: CONFIGURATION FOR LOADBALANCING WITH NETWORK TEAMING STARTMODE=auto 1 BOOTPROTO=static 2 IPADDRESS="192.168.1.1/24" 2 IPADDR6="fd00:deca:fbad:50::1/64" 2 TEAM_RUNNER="loadbalance" 3 TEAM_LB_TX_HASH="ipv4,ipv6,eth,vlan" TEAM_LB_TX_BALANCER_NAME="basic" TEAM_LB_TX_BALANCER_INTERVAL="100" TEAM_PORT_DEVICE_0="eth0" 4 TEAM_PORT_DEVICE_1="eth1" 4 TEAM_LW_NAME="ethtool" 5 TEAM_LW_ETHTOOL_DELAY_UP="10" 6 TEAM_LW_ETHTOOL_DELAY_DOWN="10" 6 1 Controls the start of the teaming device. The value of auto means, the interface will be set up when the network service is available and will be started automatically on every reboot. In case you need to control the device yourself (and prevent it from starting automatically), set STARTMODE to manual . 2 Sets a static IP address (here 192.168.1.1 for IPv4 and fd00:deca:fbad:50::1 for IPv6). If the Network Teaming device should use a dynamic IP address, set BOOTPROTO="dhcp" and remove (or comment) the line with IPADDRESS and IPADDR6 . 3 Sets TEAM_RUNNER to loadbalance to activate the loadbalancing mode. 4 Species one or more devices which should be aggregated to create the Network Teaming device. 5 Denes a link watcher to monitor the state of subordinate devices. The default value ethtool checks only if the device is up and accessible. This makes this check fast enough. However, it does not check if the device can really send or receive packets. If you need a higher condence in the connection, use the arp_ping option. This sends pings to an arbitrary host (congured in the TEAM_LW_ARP_PING_TARGET_HOST variable). Only if the replies are received, the Network Teaming device is considered to be up. 262 Use Case: Loadbalancing with Network Teaming SLES 12 SP46 Denes the delay in milliseconds between the link coming up (or down) and the runner being notied. 16.8.2 Use Case: Failover with Network Teaming Failover is used to ensure high availability of a critical Network Teaming device by involving a parallel backup network device. The backup network device is running all the time and takes over if and when the main device fails. Use the following conguration le to create a Network Teaming device with failover capabilities. Proceed with Procedure 16.1, “General Procedure” to set up the device. Check the output with teamdctl . EXAMPLE 16.13: CONFIGURATION FOR DHCP NETWORK TEAMING DEVICE STARTMODE=auto 1 BOOTPROTO=static 2 IPADDR="192.168.1.2/24" 2 IPADDR6="fd00:deca:fbad:50::2/64" 2 TEAM_RUNNER=activebackup 3 TEAM_PORT_DEVICE_0="eth0" 4 TEAM_PORT_DEVICE_1="eth1" 4 TEAM_LW_NAME=ethtool 5 TEAM_LW_ETHTOOL_DELAY_UP="10" 6 TEAM_LW_ETHTOOL_DELAY_DOWN="10" 6 1 Controls the start of the teaming device. The value of auto means, the interface will be set up when the network service is available and will be started automatically on every reboot. In case you need to control the device yourself (and prevent it from starting automatically), set STARTMODE to manual . 2 Sets a static IP address (here 192.168.1.2 for IPv4 and fd00:deca:fbad:50::2 for IPv6). If the Network Teaming device should use a dynamic IP address, set BOOTPROTO="dhcp" and remove (or comment) the line with IPADDRESS and IPADDR6 . 3 Sets TEAM_RUNNER to activebackup to activate the failover mode. 4 Species one or more devices which should be aggregated to create the Network Teaming device. 263 Use Case: Failover with Network Teaming SLES 12 SP45 Denes a link watcher to monitor the state of subordinate devices. The default value ethtool checks only if the device is up and accessible. This makes this check fast enough. However, it does not check if the device can really send or receive packets. If you need a higher condence in the connection, use the arp_ping option. This sends pings to an arbitrary host (congured in the TEAM_LW_ARP_PING_TARGET_HOST variable). Only if the replies are received, the Network Teaming device is considered to be up. 6 Denes the delay in milliseconds between the link coming up (or down) and the runner being notied. 16.8.3 Use Case: VLAN over Team Device VLAN is an abbreviation of Virtual Local Area Network. It allows the running of multiple logical (virtual) ethernets over one single physical ethernet. It logically splits the network into dierent broadcast domains so that packets are only switched between ports that are designated for the same VLAN. The following use case creates two static VLANs on top of a team device: vlan0 , bound to the IP address 192.168.10.1 vlan1 , bound to the IP address 192.168.20.1 Proceed as follows: 1. Enable the VLAN tags on your switch. If you want to use loadbalancing for your team device, your switch needs to be capable of Link Aggregation Control Protocol (LACP) (802.3ad). Consult your hardware manual about the details. 2. Decide if you want to use loadbalancing or failover for your team device. Set up your team device as described in Section 16.8.1, “Use Case: Loadbalancing with Network Teaming” or Section 16.8.2, “Use Case: Failover with Network Teaming”. 3. In /etc/sysconfig/network create a le ifcfg-vlan0 with the following content: STARTMODE="auto" BOOTPROTO="static" 1 IPADDR=''192.168.10.1/24'' 2 ETHERDEVICE="team0" 3 VLAN_ID="0" 4 VLAN=''yes'' 264 Use Case: VLAN over Team Device SLES 12 SP41 Denes a xed IP address, specied in IPADDR . 2 Denes the IP address, here with its netmask. 3 Contains the real interface to use for the VLAN interface, here our team device ( team0 ). 4 Species a unique ID for the VLAN. Preferably, the le name and the VLAN_ID corresponds to the name ifcfg-vlanVLAN_ID . In our case VLAN_ID is 0 which leads to the lename ifcfg-vlan0 . 4. Copy the le /etc/sysconfig/network/ifcfg-vlan0 to /etc/sysconfig/network/ ifcfg-vlan1 and change the following values: IPADDR from 192.168.10.1/24 to 192.168.20.1/24 . VLAN_ID from 0 to 1 . 5. Start the two VLANs: root # wicked ifup vlan0 vlan1 6. Check the output of ifconfig : root # ifconfig -a [...] vlan0 Link encap:Ethernet HWaddr 08:00:27:DC:43:98 inet addr:192.168.10.1 Bcast:192.168.10.255 Mask:255.255.255.0 inet6 addr: fe80::a00:27ff:fedc:4398/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:12 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 b) TX bytes:816 (816.0 b) vlan1 Link encap:Ethernet HWaddr 08:00:27:DC:43:98 inet addr:192.168.20.1 Bcast:192.168.20.255 Mask:255.255.255.0 inet6 addr: fe80::a00:27ff:fedc:4398/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:12 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 b) TX bytes:816 (816.0 b) 265 Use Case: VLAN over Team Device SLES 12 SP416.9 Software-Defined Networking with Open vSwitch Software-dened networking (SDN) means separating the system that controls where trac is sent (the control plane) from the underlying system that forwards trac to the selected destination (the data plane, also called the forwarding plane). This means that the functions previously fullled by a single, usually inexible switch can now be separated between a switch (data plane) and its controller (control plane). In this model, the controller is programmable and can be very exible and adapt quickly to changing network conditions. Open vSwitch is software that implements a distributed virtual multilayer switch that is compatible with the OpenFlow protocol. OpenFlow allows a controller application to modify the conguration of a switch. OpenFlow is layered onto the TCP protocol and is implemented in a range of hardware and software. A single controller can thus drive multiple, very dierent switches. 16.9.1 Advantages of Open vSwitch Software-dened networking with Open vSwitch brings several advantages with it, especially when you used together with virtual machines: Networking states can be identied easily. Networks and their live state can be moved from one host to another. Network dynamics are traceable and external software can be enabled to respond to them. You can apply and manipulate tags in network packets to identify which machine they are coming from or going to and maintain other networking context. Tagging rules can be congured and migrated. Open vSwitch implements the GRE protocol (Generic Routing Encapsulation). This allows you, for example, to connect private VM networks to each other. Open vSwitch can be used on its own, but is designed to integrate with networking hardware and can control hardware switches. 266 Software-Defined Networking with Open vSwitch SLES 12 SP416.9.2 Installing Open vSwitch 1. Install Open vSwitch and supplementary packages: root # zypper install openvswitch openvswitch-switch If you plan to use Open vSwitch together with the KVM hypervisor, additionally install tunctl . If you plan to use Open vSwitch together with the Xen hypervisor, additionally install openvswitch-kmp-xen . 2. Enable the Open vSwitch service: root # systemctl enable openvswitch 3. Either restart the computer or use systemctl to start the Open vSwitch service immediately: root # systemctl start openvswitch 4. To check whether Open vSwitch was activated correctly, use: root # systemctl status openvswitch 16.9.3 Overview of Open vSwitch Daemons and Utilities Open vSwitch consists of several components. Among them are a kernel module and various user space components. The kernel module is used for accelerating the data path, but is not necessary for a minimal Open vSwitch installation. 16.9.3.1 Daemons The central executables of Open vSwitch are its two daemons. When you start the openvswitch service, you are indirectly starting them. The main Open vSwitch daemon ( ovs-vswitchd ) provides the implementation of a switch. The Open vSwitch database daemon ( ovsdb-server ) serves the database that stores the conguration and state of Open vSwitch. 267 Installing Open vSwitch SLES 12 SP416.9.3.2 Utilities Open vSwitch also comes with several utilities that help you work with it. The following list is not exhaustive, but instead describes important commands only. ovsdb-tool Create, upgrade, compact, and query Open vSwitch databases. Do transactions on Open vSwitch databases. ovs-appctl Congure a running ovs-vswitchd or ovsdb-server daemon. ovs-dpctl , ovs-dpctl-top Create, modify, visualize, and delete data paths. Using this tool can interfere with ovs-vswitchd also performing data path management. Therefore, it is often used for diagnostics only. ovs-dpctl-top creates a top -like visualization for data paths. ovs-ofctl Manage any switches adhering to the OpenFlow protocol. ovs-ofctl is not limited to interacting with Open vSwitch. ovs-vsctl Provides a high-level interface to the conguration database. It can be used to query and modify the database. In eect, it shows the status of ovs-vswitchd and can be used to congure it. 16.9.4 Creating a Bridge with Open vSwitch The following example conguration uses the Wicked network service that is used by default on SUSE Linux Enterprise Server. To learn more about Wicked, see Section 16.5, “Configuring a Network Connection Manually”. When you have installed and started Open vSwitch, proceed as follows: 1. To congure a bridge for use by your virtual machine, create a le with content like this: STARTMODE=''auto'' 1 BOOTPROTO=''dhcp'' 2 OVS_BRIDGE=''yes'' 3 OVS_BRIDGE_PORT_DEVICE_1=''eth0'' 4 268 Creating a Bridge with Open vSwitch SLES 12 SP41 Set up the bridge automatically when the network service is started. 2 The protocol to use for conguring the IP address. 3 Mark the conguration as an Open vSwitch bridge. 4 Choose which device/devices should be added to the bridge. To add more devices, append additional lines for each of them to the le: OVS_BRIDGE_PORT_DEVICE_SUFFIX=''DEVICE'' The SUFFIX can be any alphanumeric string. However, to avoid overwriting a previous denition, make sure the SUFFIX of each device is unique. Save the le in the directory /etc/sysconfig/network under the name ifcfg-br0 . Instead of br0 , you can use any name you want. However, the le name needs to begin with ifcfg- . To learn about further options, refer to the man pages of ifcfg ( man 5 ifcfg ) and ifcfg-ovs-bridge ( man 5 ifcfg-ovs-bridge ). 2. Now start the bridge: root # wicked ifup br0 When Wicked is done, it should output the name of the bridge and next to it the state up . 16.9.5 Using Open vSwitch Directly with KVM After having created the bridge as described in Section 16.9.4, “Creating a Bridge with Open vSwitch”, you can use Open vSwitch to manage the network access of virtual machines created with KVM/ QEMU. 1. To be able to best use the capabilities of Wicked, make some further changes to the bridge congured before. Open the previously created /etc/sysconfig/network/ifcfg-br0 and append a line for another port device: OVS_BRIDGE_PORT_DEVICE_2=''tap0'' Additionally, set BOOTPROTO to none . The le should now look like this: STARTMODE=''auto'' BOOTPROTO=''none'' OVS_BRIDGE=''yes'' 269 Using Open vSwitch Directly with KVM SLES 12 SP4OVS_BRIDGE_PORT_DEVICE_1=''eth0'' OVS_BRIDGE_PORT_DEVICE_2=''tap0'' The new port device tap0 will be congured in the next step. 2. Now add a conguration le for the tap0 device: STARTMODE=''auto'' BOOTPROTO=''none'' TUNNEL=''tap'' Save the le in the directory /etc/sysconfig/network under the name ifcfg-tap0 . Tip: Allowing Other Users to Access the Tap Device To be able to use this tap device from a virtual machine started as a user who is not root , append: TUNNEL_SET_OWNER=USER_NAME To allow access for an entire group, append: TUNNEL_SET_GROUP=GROUP_NAME 3. Finally, open the conguration for the device dened as the rst OVS_BRIDGE_PORT_DEVICE . If you did not change the name, that should be eth0 . Therefore, open /etc/sysconfig/network/ifcfg-eth0 and make sure that the following options are set: STARTMODE=''auto'' BOOTPROTO=''none'' If the le does not exist yet, create it. 4. Restart the bridge interface using Wicked: root # wicked ifreload br0 This will also trigger a reload of the newly dened bridge port devices. 5. To start a virtual machine, use, for example: root # qemu-kvm \ -drive file=/PATH/TO/DISK-IMAGE 1 \ 270 Using Open vSwitch Directly with KVM SLES 12 SP4-m 512 -net nic,vlan=0,macaddr=00:11:22:EE:EE:EE \ -net tap,ifname=tap0,script=no,downscript=no 2 1 The path to the QEMU disk image you want to start. 2 Use the tap device ( tap0 ) created before. For further information on the usage of KVM/QEMU, see Book “Virtualization Guide”. 16.9.6 Using Open vSwitch with libvirt After having created the bridge as described before in Section 16.9.4, “Creating a Bridge with Open vSwitch”, you can add the bridge to an existing virtual machine managed with libvirt . Since libvirt has some support for Open vSwitch bridges already, you can use the bridge created in Section 16.9.4, “Creating a Bridge with Open vSwitch” without further changes to the networking conguration. 1. Open the domain XML le for the intended virtual machine: root # virsh edit VM_NAME Replace VM_NAME with the name of the desired virtual machine. This will open your default text editor. 2. Find the networking section of the document by looking for a section starting with and ending in . Replace the existing section with a networking section that looks somewhat like this: Important: Compatibility of virsh iface-* and Virtual Machine Manager with Open vSwitch At the moment, the Open vSwitch compatibility of libvirt is not exposed through the virsh iface-* tools and Virtual Machine Manager. If you use any of these tools, your conguration can break. 3. You can now start or restart the virtual machine as usual. 271 Using Open vSwitch with libvirt SLES 12 SP4For further information on the usage of libvirt , see Book “Virtualization Guide”. 16.9.7 For More Information http://openvswitch.org/support/ The documentation section of the Open vSwitch project Web site https://www.opennetworking.org/images/stories/downloads/sdn-resources/white-papers/wp- sdn-newnorm.pdf Whitepaper by the Open Networking Foundation about software-dened networking and the OpenFlow protocol 272 For More Information SLES 12 SP417 Printer Operation SUSE® Linux Enterprise Server supports printing with many types of printers, including remote network printers. Printers can be congured manually or with YaST. For conguration instructions, refer to Book “Deployment Guide”, Chapter 11 “Setting Up Hardware Components with YaST”, Section 11.3 “Setting Up a Printer”. Both graphical and command line utilities are available for starting and managing print jobs. If your printer does not work as expected, refer to Section 17.8, “Troubleshooting”. CUPS (Common Unix Printing System) is the standard print system in SUSE Linux Enterprise Server. Printers can be distinguished by interface, such as USB or network, and printer language. When buying a printer, make sure that the printer has an interface that is supported (USB, Ethernet, or Wi-Fi) and a suitable printer language. Printers can be categorized on the basis of the following three classes of printer languages: PostScript Printers PostScript is the printer language in which most print jobs in Linux and Unix are generated and processed by the internal print system. If PostScript documents can be processed directly by the printer and do not need to be converted in additional stages in the print system, the number of potential error sources is reduced. Currently PostScript is being replaced by PDF as the standard print job format. PostScript +PDF printers that can directly print PDF (in addition to PostScript) already exist. For traditional PostScript printers PDF needs to be converted to PostScript in the printing workow. Standard Printers (Languages Like PCL and ESC/P) In the case of known printer languages, the print system can convert PostScript jobs to the respective printer language with Ghostscript. This processing stage is called interpreting. The best-known languages are PCL (which is mostly used by HP printers and their clones) and ESC/P (which is used by Epson printers). These printer languages are usually supported by Linux and produce an adequate print result. Linux may not be able to address some special printer functions. Except for HP and Epson, there are currently no printer manufacturers who develop Linux drivers and make them available to Linux distributors under an open source license. Proprietary Printers (Also Called GDI Printers) 273 SLES 12 SP4These printers do not support any of the common printer languages. They use their own undocumented printer languages, which are subject to change when a new edition of a model is released. Usually only Windows drivers are available for these printers. See Section 17.8.1, “Printers without Standard Printer Language Support” for more information. Before you buy a new printer, refer to the following sources to check how well the printer you intend to buy is supported: http://www.openprinting.org/printers The OpenPrinting home page with the printer database. The database shows the latest Linux support status. However, a Linux distribution can only integrate the drivers available at production time. Accordingly, a printer currently rated as “perfectly supported” may not have had this status when the latest SUSE Linux Enterprise Server version was released. Thus, the databases may not necessarily indicate the correct status, but only provide an approximation. http://pages.cs.wisc.edu/~ghost/ The Ghostscript Web page. /usr/share/doc/packages/ghostscript/catalog.devices List of built-in Ghostscript drivers. 17.1 The CUPS Workflow The user creates a print job. The print job consists of the data to print plus information for the spooler. This includes the name of the printer or the name of the print queue, and optionally, information for the lter, such as printer-specic options. At least one dedicated print queue exists for every printer. The spooler holds the print job in the queue until the desired printer is ready to receive data. When the printer is ready, the spooler sends the data through the lter and back-end to the printer. The lter converts the data generated by the application that is printing (usually PostScript or PDF, but also ASCII, JPEG, etc.) into printer-specic data (PostScript, PCL, ESC/P, etc.). The features of the printer are described in the PPD les. A PPD le contains printer-specic options with the parameters needed to enable them on the printer. The lter system makes sure that options selected by the user are enabled. 274 The CUPS Workflow SLES 12 SP4If you use a PostScript printer, the lter system converts the data into printer-specic PostScript. This does not require a printer driver. If you use a non-PostScript printer, the lter system converts the data into printer-specic data. This requires a printer driver suitable for your printer. The back-end receives the printer-specic data from the lter then passes it to the printer. 17.2 Methods and Protocols for Connecting Printers There are various possibilities for connecting a printer to the system. The conguration of CUPS does not distinguish between a local printer and a printer connected to the system over the network. For more information about the printer connection, read the article CUPS in a Nutshell at http://en.opensuse.org/SDB:CUPS_in_a_Nutshell . IBM Z Printers and similar devices provided by the z/VM that connect locally with the IBM z Systems mainframes are not supported by CUPS. On these platforms, printing is only possible over the network. The cabling for network printers must be installed according to the instructions of the printer manufacturer. Warning: Changing Cable Connections in a Running System When connecting the printer to the machine, do not forget that only USB devices can be plugged in or unplugged during operation. To avoid damaging your system or printer, shut down the system before changing any connections that are not USB. 17.3 Installing the Software PPD (PostScript printer description) is the computer language that describes the properties, like resolution, and options, such as the availability of a duplex unit. These descriptions are required for using various printer options in CUPS. Without a PPD le, the print data would be forwarded to the printer in a “raw” state, which is usually not desired. To congure a PostScript printer, the best approach is to get a suitable PPD le. Many PPD les are available in the packages manufacturer-PPDs and OpenPrintingPPDs-postscript . See Section 17.7.3, “PPD Files in Various Packages” and Section 17.8.2, “No Suitable PPD File Available for a PostScript Printer”. 275 Methods and Protocols for Connecting Printers SLES 12 SP4New PPD les can be stored in the directory /usr/share/cups/model/ or added to the print system with YaST as described in Book “Deployment Guide”, Chapter  11 “Setting Up Hardware Components with YaST”, Section 11.3.1.1 “Adding Drivers with YaST”. Subsequently, the PPD le can be selected during the printer setup. Be careful if a printer manufacturer wants you to install entire software packages. This kind of installation may result in the loss of the support provided by SUSE Linux Enterprise Server. Also, print commands may work dierently and the system may no longer be able to address devices of other manufacturers. For this reason, the installation of manufacturer software is not recommended. 17.4 Network Printers A network printer can support various protocols, some even concurrently. Although most of the supported protocols are standardized, some manufacturers modify the standard. Manufacturers then provide drivers for only a few operating systems. Unfortunately, Linux drivers are rarely provided. The current situation is such that you cannot act on the assumption that every protocol works smoothly in Linux. Therefore, you may need to experiment with various options to achieve a functional conguration. CUPS supports the socket , LPD , IPP and smb protocols. socket Socket refers to a connection in which the plain print data is sent directly to a TCP socket. Some socket port numbers that are commonly used are 9100 or 35 . The device URI (uniform resource identier) syntax is: socket:// IP.OF.THE.PRINTER : PORT , for example: socket://192.168.2.202:9100/ . LPD (Line Printer Daemon) The LPD protocol is described in RFC 1179. Under this protocol, some job-related data, such as the ID of the print queue, is sent before the actual print data is sent. Therefore, a print queue must be specied when conguring the LPD protocol. The implementations of diverse printer manufacturers are exible enough to accept any name as the print queue. If necessary, the printer manual should indicate what name to use. LPT, LPT1, LP1 or similar names are often used. The port number for an LPD service is 515 . An example device URI is lpd://192.168.2.202/LPT1 . IPP (Internet Printing Protocol) 276 Network Printers SLES 12 SP4IPP is a relatively new protocol (1999) based on the HTTP protocol. With IPP, more job- related data is transmitted than with the other protocols. CUPS uses IPP for internal data transmission. The name of the print queue is necessary to congure IPP correctly. The port number for IPP is 631 . Example device URIs are ipp://192.168.2.202/ps and ipp://192.168.2.202/printers/ps . SMB (Windows Share) CUPS also supports printing on printers connected to Windows shares. The protocol used for this purpose is SMB. SMB uses the port numbers 137 , 138 and 139 . Example device URIs are smb://user:password@workgroup/ smb.example.com/printer , smb://user:password@smb.example.com/printer , and smb://smb.example.com/printer . The protocol supported by the printer must be determined before conguration. If the manufacturer does not provide the needed information, the command nmap (which comes with the nmap package) can be used to ascertain the protocol. nmap checks a host for open ports. For example: nmap -p 35,137-139,515,631,9100-10000 IP.OF.THE.PRINTER 17.5 Configuring CUPS with Command Line Tools CUPS can be congured with command line tools like lpinfo , lpadmin and lpoptions . You need a device URI consisting of a back-end, such as USB, and parameters. To determine valid device URIs on your system use the command lpinfo -v | grep ":/" : # lpinfo -v | grep ":/" direct usb://ACME/FunPrinter%20XL network socket://192.168.2.253 With lpadmin the CUPS server administrator can add, remove or manage print queues. To add a print queue, use the following syntax: lpadmin -p QUEUE -v DEVICE-URI -P PPD-FILE -E Then the device ( -v ) is available as QUEUE ( -p ), using the specied PPD le ( -P ). This means that you must know the PPD le and the device URI to congure the printer manually. 277 Configuring CUPS with Command Line Tools SLES 12 SP4Do not use -E as the rst option. For all CUPS commands, -E as the rst argument sets use of an encrypted connection. To enable the printer, -E must be used as shown in the following example: lpadmin -p ps -v usb://ACME/FunPrinter%20XL -P \ /usr/share/cups/model/Postscript.ppd.gz -E The following example congures a network printer: lpadmin -p ps -v socket://192.168.2.202:9100/ -P \ /usr/share/cups/model/Postscript-level1.ppd.gz -E For more options of lpadmin , see the man page of lpadmin(8) . During printer setup, certain options are set as default. These options can be modied for every print job (depending on the print tool used). Changing these default options with YaST is also possible. Using command line tools, set default options as follows: 1. First, list all options: lpoptions -p QUEUE -l Example: Resolution/Output Resolution: 150dpi *300dpi 600dpi The activated default option is identied by a preceding asterisk ( * ). 2. Change the option with lpadmin : lpadmin -p QUEUE -o Resolution=600dpi 3. Check the new setting: lpoptions -p QUEUE -l Resolution/Output Resolution: 150dpi 300dpi *600dpi When a normal user runs lpoptions , the settings are written to ~/.cups/lpoptions . However, root settings are written to /etc/cups/lpoptions . 278 Configuring CUPS with Command Line Tools SLES 12 SP417.6 Printing from the Command Line To print from the command line, enter lp -d QUEUENAME FILENAME , substituting the corresponding names for QUEUENAME and FILENAME . Some applications rely on the lp command for printing. In this case, enter the correct command in the application''s print dialog, usually without specifying FILENAME , for example, lp -d QUEUENAME . 17.7 Special Features in SUSE Linux Enterprise Server Several CUPS features have been adapted for SUSE Linux Enterprise Server. Some of the most important changes are covered here. 17.7.1 CUPS and Firewall After having performed a default installation of SUSE Linux Enterprise Server, SuSEFirewall2 is active and the network interfaces are congured to be in the External Zone which blocks incoming trac. More information about the SuSEFirewall2 conguration is available in Book “Security Guide”, Chapter 15 “Masquerading and Firewalls”, Section 15.4 “SuSEFirewall2” and at http:// en.opensuse.org/SDB:CUPS_and_SANE_Firewall_settings . 17.7.1.1 CUPS Client Normally, a CUPS client runs on a regular workstation located in a trusted network environment behind a rewall. In this case it is recommended to congure the network interface to be in the Internal Zone , so the workstation is reachable from within the network. 17.7.1.2 CUPS Server If the CUPS server is part of a trusted network environment protected by a rewall, the network interface should be congured to be in the Internal Zone of the rewall. It is not recommended to set up a CUPS server in an untrusted network environment unless you ensure that it is protected by special rewall rules and secure settings in the CUPS conguration. 279 Printing from the Command Line SLES 12 SP417.7.2 Browsing for Network Printers CUPS servers regularly announce the availability and status information of shared printers over the network. Clients can access this information to display a list of available printers in printing dialogs, for example. This is called “browsing”. CUPS servers announce their print queues over the network either via the traditional CUPS browsing protocol or via Bonjour/DND-SD. To be able to browse network print queues, the service cups-browsed needs to run on all clients that print via CUPS servers. cups-browsed is not started by default. To start it for the active session, use sudo systemctl start cups- browsed . To ensure it is automatically started after booting, enable it with sudo systemctl enable cups-browsed on all clients. In case browsing does not work after having started cups-browsed , the CUPS server(s) probably announce the network print queues via Bonjour/DND-SD. In this case you need to additionally install the package avahi and start the associated service with sudo systemctl start avahi- daemon on all clients. 17.7.3 PPD Files in Various Packages The YaST printer conguration sets up the queues for CUPS using the PPD les installed in / usr/share/cups/model . To nd the suitable PPD les for the printer model, YaST compares the vendor and model determined during hardware detection with the vendors and models in all PPD les. For this purpose, the YaST printer conguration generates a database from the vendor and model information extracted from the PPD les. The conguration using only PPD les and no other information sources has the advantage that the PPD les in /usr/share/cups/model can be modied freely. For example, if you have PostScript printers the PPD les can be copied directly to /usr/share/cups/model (if they do not already exist in the manufacturer-PPDs or OpenPrintingPPDs-postscript packages) to achieve an optimum conguration for your printers. Additional PPD les are provided by the following packages: gutenprint: the Gutenprint driver and its matching PPDs splix: the SpliX driver and its matching PPDs OpenPrintingPPDs-ghostscript: PPDs for Ghostscript built-in drivers OpenPrintingPPDs-hpijs: PPDs for the HPIJS driver for non-HP printers 280 Browsing for Network Printers SLES 12 SP417.8 Troubleshooting The following sections cover some of the most frequently encountered printer hardware and software problems and ways to solve or circumvent these problems. Among the topics covered are GDI printers, PPD les and port conguration. Common network printer problems, defective printouts, and queue handling are also addressed. 17.8.1 Printers without Standard Printer Language Support These printers do not support any common printer language and can only be addressed with special proprietary control sequences. Therefore they can only work with the operating system versions for which the manufacturer delivers a driver. GDI is a programming interface developed by Microsoft* for graphics devices. Usually the manufacturer delivers drivers only for Windows, and since the Windows driver uses the GDI interface these printers are also called GDI printers. The actual problem is not the programming interface, but that these printers can only be addressed with the proprietary printer language of the respective printer model. Some GDI printers can be switched to operate either in GDI mode or in one of the standard printer languages. See the manual of the printer whether this is possible. Some models require special Windows software to do the switch (note that the Windows printer driver may always switch the printer back into GDI mode when printing from Windows). For other GDI printers there are extension modules for a standard printer language available. Some manufacturers provide proprietary drivers for their printers. The disadvantage of proprietary printer drivers is that there is no guarantee that these work with the installed print system or that they are suitable for the various hardware platforms. In contrast, printers that support a standard printer language do not depend on a special print system version or a special hardware platform. Instead of spending time trying to make a proprietary Linux driver work, it may be more cost-eective to purchase a printer which supports a standard printer language (preferably PostScript). This would solve the driver problem once and for all, eliminating the need to install and congure special driver software and obtain driver updates that may be required because of new developments in the print system. 281 Troubleshooting SLES 12 SP417.8.2 No Suitable PPD File Available for a PostScript Printer If the manufacturer-PPDs or OpenPrintingPPDs-postscript packages do not contain a suitable PPD le for a PostScript printer, it should be possible to use the PPD le from the driver CD of the printer manufacturer or download a suitable PPD le from the Web page of the printer manufacturer. If the PPD le is provided as a zip archive (.zip) or a self-extracting zip archive ( .exe ), unpack it with unzip . First, review the license terms of the PPD le. Then use the cupstestppd utility to check if the PPD le complies with “Adobe PostScript Printer Description File Format Specication, version 4.3.” If the utility returns “FAIL,” the errors in the PPD les are serious and are likely to cause major problems. The problem spots reported by cupstestppd should be eliminated. If necessary, ask the printer manufacturer for a suitable PPD le. 17.8.3 Network Printer Connections Identifying Network Problems Connect the printer directly to the computer. For test purposes, congure the printer as a local printer. If this works, the problems are related to the network. Checking the TCP/IP Network The TCP/IP network and name resolution must be functional. Checking a Remote lpd Use the following command to test if a TCP connection can be established to lpd (port 515 ) on HOST : netcat -z HOST 515 && echo ok || echo failed If the connection to lpd cannot be established, lpd may not be active or there may be basic network problems. Provided that the respective lpd is active and the host accepts queries, run the following command as root to query a status report for QUEUE on remote HOST : echo -e "\004queue" \ | netcat -w 2 -p 722 HOST 515 If lpd does not respond, it may not be active or there may be basic network problems. If lpd responds, the response should show why printing is not possible on the queue on host . If you receive a response like that shown in Example 17.1, “Error Message from lpd”, the problem is caused by the remote lpd . 282 No Suitable PPD File Available for a PostScript Printer SLES 12 SP4EXAMPLE 17.1: ERROR MESSAGE FROM lpd lpd: your host does not have line printer access lpd: queue does not exist printer: spooling disabled printer: printing disabled Checking a Remote cupsd A CUPS network server can broadcast its queues by default every 30 seconds on UDP port 631 . Accordingly, the following command can be used to test whether there is a broadcasting CUPS network server in the network. Make sure to stop your local CUPS daemon before executing the command. netcat -u -l -p 631 & PID=$! ; sleep 40 ; kill $PID If a broadcasting CUPS network server exists, the output appears as shown in Example 17.2, “Broadcast from the CUPS Network Server”. EXAMPLE 17.2: BROADCAST FROM THE CUPS NETWORK SERVER ipp://192.168.2.202:631/printers/queue IBM Z Take into account that IBM z Systems Ethernet devices do not receive broadcasts by default. The following command can be used to test if a TCP connection can be established to cupsd (port 631 ) on HOST : netcat -z HOST 631 && echo ok || echo failed If the connection to cupsd cannot be established, cupsd may not be active or there may be basic network problems. lpstat -h HOST -l -t returns a (possibly very long) status report for all queues on HOST , provided the respective cupsd is active and the host accepts queries. The next command can be used to test if the QUEUE on HOST accepts a print job consisting of a single carriage-return character. Nothing should be printed. Possibly, a blank page may be ejected. echo -en "\r" \ | lp -d queue -h HOST Troubleshooting a Network Printer or Print Server Machine 283 Network Printer Connections SLES 12 SP4Spoolers running in a print server machine sometimes cause problems when they need to deal with multiple print jobs. Since this is caused by the spooler in the print server machine, there no way to resolve this issue. As a work-around, circumvent the spooler in the print server machine by addressing the printer connected to the print server machine directly with the TCP socket. See Section 17.4, “Network Printers”. In this way, the print server machine is reduced to a converter between the various forms of data transfer (TCP/IP network and local printer connection). To use this method, you need to know the TCP port on the print server machine. If the printer is connected to the print server machine and turned on, this TCP port can usually be determined with the nmap utility from the nmap package some time after the print server machine is powered up. For example, nmap  IP-address may deliver the following output for a print server machine: Port State Service 23/tcp open telnet 80/tcp open http 515/tcp open printer 631/tcp open cups 9100/tcp open jetdirect This output indicates that the printer connected to the print server machine can be addressed via TCP socket on port 9100 . By default, nmap only checks several commonly known ports listed in /usr/share/nmap/nmap-services . To check all possible ports, use the command nmap -p  FROM_PORT - TO_PORT   IP_ADDRESS . This may take some time. For further information, refer to the man page of nmap . Enter a command like echo -en "\rHello\r\f" | netcat -w 1 IP-address port cat file | netcat -w 1 IP-address port to send character strings or les directly to the respective port to test if the printer can be addressed on this port. 17.8.4 Defective Printouts without Error Message For the print system, the print job is completed when the CUPS back-end completes the data transfer to the recipient (printer). If further processing on the recipient fails (for example, if the printer is not able to print the printer-specic data) the print system does not notice this. If the printer cannot print the printer-specic data, select a PPD le that is more suitable for the printer. 284 Defective Printouts without Error Message SLES 12 SP417.8.5 Disabled Queues If the data transfer to the recipient fails entirely after several attempts, the CUPS back-end, such as USB or socket , reports an error to the print system (to cupsd ). The back-end determines how many unsuccessful attempts are appropriate until the data transfer is reported as impossible. As further attempts would be in vain, cupsd disables printing for the respective queue. After eliminating the cause of the problem, the system administrator must re-enable printing with the command cupsenable . 17.8.6 CUPS Browsing: Deleting Print Jobs If a CUPS network server broadcasts its queues to the client hosts via browsing and a suitable local cupsd is active on the client hosts, the client cupsd accepts print jobs from applications and forwards them to the cupsd on the server. When cupsd on the server accepts a print job, it is assigned a new job number. Therefore, the job number on the client host is dierent from the job number on the server. As a print job is usually forwarded immediately, it cannot be deleted with the job number on the client host This is because the client cupsd regards the print job as completed when it has been forwarded to the server cupsd . To delete the print job on the server, use a command such as lpstat -h cups.example.com -o to determine the job number on the server. This assumes that the server has not already completed the print job (that is, sent it completely to the printer). Use the obtained job number to delete the print job on the server as follows: cancel -h cups.example.com QUEUE-JOBNUMBER 17.8.7 Defective Print Jobs and Data Transfer Errors If you switch the printer o or shut down the computer during the printing process, print jobs remain in the queue. Printing resumes when the computer (or the printer) is switched back on. Defective print jobs must be removed from the queue with cancel . If a print job is corrupted or an error occurs in the communication between the host and the printer, the printer cannot process the data correctly and prints numerous sheets of paper with unintelligible characters. To x the problem, follow these steps: 1. To stop printing, remove all paper from ink jet printers or open the paper trays of laser printers. High-quality printers have a button for canceling the current printout. 285 Disabled Queues SLES 12 SP42. The print job may still be in the queue, because jobs are only removed after they are sent completely to the printer. Use lpstat -o or lpstat -h cups.example.com -o to check which queue is currently printing. Delete the print job with cancel QUEUE - JOBNUMBER or cancel -h cups.example.com QUEUE - JOBNUMBER . 3. Some data may still be transferred to the printer even though the print job has been deleted from the queue. Check if a CUPS back-end process is still running for the respective queue and terminate it. 4. Reset the printer completely by switching it o for some time. Then insert the paper and turn on the printer. 17.8.8 Debugging CUPS Use the following generic procedure to locate problems in CUPS: 1. Set LogLevel debug in /etc/cups/cupsd.conf . 2. Stop cupsd . 3. Remove /var/log/cups/error_log* to avoid having to search through very large log les. 4. Start cupsd . 5. Repeat the action that led to the problem. 6. Check the messages in /var/log/cups/error_log* to identify the cause of the problem. 17.8.9 For More Information In-depth information about printing on SUSE Linux is presented in the openSUSE Support Database at https://en.opensuse.org/Portal:Printing . Solutions to many specic problems are presented in the SUSE Knowledgebase (https://www.suse.com/support/ ). Locate the relevant articles with a text search for CUPS . 286 Debugging CUPS SLES 12 SP418 The X Window System The X Window System (X11) is the de facto standard for graphical user interfaces in Unix. X is network-based, enabling applications started on one host to be displayed on another host connected over any kind of network (LAN or Internet). This chapter provides basic information on the X conguration, and background information about the use of fonts in SUSE® Linux Enterprise Server. Usually, the X Window System needs no conguration. The hardware is dynamically detected during X start-up. The use of xorg.conf is therefore deprecated. If you still need to specify custom options to change the way X behaves, you can still do so by modifying conguration les under /etc/X11/xorg.conf.d/ . Tip: IBM z Systems: Configuring the Graphical User Interface IBM z Systems does not have any input or output devices supported by X.Org. Therefore, none of the conguration procedures described in this section apply. More relevant information for IBM z  Systems can be found in Book “Deployment Guide”, Chapter  4 “Installation on IBM z Systems”. 18.1 Installing and Configuring Fonts Fonts in Linux can be categorized into two parts: Outline or Vector Fonts Contains a mathematical description as drawing instructions about the shape of a glyph. As such, each glyph can be scaled to arbitrary sizes without loss of quality. Before such a font (or glyph) can be used, the mathematical descriptions need to be transformed into a raster (grid). This process is called font rasterization. Font hinting (embedded inside the font) improves and optimizes the rendering result for a particular size. Rasterization and hinting is done with the FreeType library. Common formats under Linux are PostScript Type 1 and Type 2, TrueType, and OpenType. Bitmap or Raster Fonts 287 Installing and Configuring Fonts SLES 12 SP4Consists of an array of pixels designed for a specic font size. Bitmap fonts are extremely fast and simple to render. However, compared to vector fonts, bitmap fonts cannot be scaled without losing quality. As such, these fonts are usually distributed in dierent sizes. These days, bitmap fonts are still used in the Linux console and sometimes in terminals. Under Linux, Portable Compiled Format (PCF) or Glyph Bitmap Distribution Format (BDF) are the most common formats. The appearance of these fonts can be inuenced by two main aspects: choosing a suitable font family, rendering the font with an algorithm that achieves results comfortable for the receiver''s eyes. The last point is only relevant to vector fonts. Although the above two points are highly subjective, some defaults need to be created. Linux font rendering systems consist of several libraries with dierent relations. The basic font rendering library is FreeType (http://www.freetype.org/) , which converts font glyphs of supported formats into optimized bitmap glyphs. The rendering process is controlled by an algorithm and its parameters (which may be subject to patent issues). Every program or library which uses FreeType should consult the Fontconfig (http:// www.fontconfig.org/) library. This library gathers font conguration from users and from the system. When a user amends his Fontcong setting, this change will result in Fontcong-aware applications. More sophisticated OpenType shaping needed for scripts such as Arabic, Han or Phags-Pa and other higher level text processing is done using Harfbuzz (http://www.harfbuzz.org/) or Pango (http://www.pango.org/) . 18.1.1 Showing Installed Fonts To get an overview about which fonts are installed on your system, ask the commands rpm or fc-list . Both will give you a good answer, but may return a dierent list depending on system and user conguration: rpm Invoke rpm to see which software packages containing fonts are installed on your system: rpm -qa ''*fonts*'' 288 Showing Installed Fonts SLES 12 SP4Every font package should satisfy this expression. However, the command may return some false positives like fonts-config (which is neither a font nor does it contain fonts). fc-list Invoke fc-list to get an overview about what font families can be accessed, whether they are installed on the system or in your home: fc-list '':'' family Note: Command fc-list The command fc-list is a wrapper to the Fontcong library. It is possible to query a lot of interesting information from Fontcong—or, to be more precise, from its cache. See man 1 fc-list for more details. 18.1.2 Viewing Fonts If you want to know what an installed font family looks like, either use the command ftview (package ft2demos ) or visit http://fontinfo.opensuse.org/ . For example, to display the FreeMono font in 14 point, use ftview like this: ftview 14 /usr/share/fonts/truetype/FreeMono.ttf If you need further information, go to http://fontinfo.opensuse.org/ to nd out which styles (regular, bold, italic, etc.) and languages are supported. 18.1.3 Querying Fonts To query which font is used when a pattern is given, use the fc-match command. For example, if your pattern contains an already installed font, fc-match returns the le name, font family, and the style: tux > fc-match ''Liberation Serif'' LiberationSerif-Regular.ttf: "Liberation Serif" "Regular" If the desired font does not exist on your system, Fontcong''s matching rules take place and try to nd the most similar fonts available. This means, your request is substituted: tux > fc-match ''Foo Family'' 289 Viewing Fonts SLES 12 SP4DejaVuSans.ttf: "DejaVu Sans" "Book" Fontcong supports aliases: a name is substituted with another family name. A typical example are the generic names such as “sans-serif”, “serif”, and “monospace”. These alias names can be substituted by real family names or even a preference list of family names: tux > for font in serif sans mono; do fc-match "$font" ; done DejaVuSerif.ttf: "DejaVu Serif" "Book" DejaVuSans.ttf: "DejaVu Sans" "Book" DejaVuSansMono.ttf: "DejaVu Sans Mono" "Book" The result may vary on your system, depending on which fonts are currently installed. Note: Similarity Rules according to Fontconfig Fontcong always returns a real family (if at least one is installed) according to the given request, as similar as possible. “Similarity” depends on Fontcong''s internal metrics and on the user''s or administrator''s Fontcong settings. 18.1.4 Installing Fonts To install a new font there are these major methods: 1. Manually install the font les such as *.ttf or *.otf to a known font directory. If it needs to be system-wide, use the standard directory /usr/share/fonts . For installation in your home directory, use ~/.config/fonts . If you want to deviate from the standard directories, Fontcong allows you to choose another one. Let Fontcong know by using the element, see Section 18.1.5.2, “Diving into Fontconfig XML” for details. 2. Install fonts using zypper . Lots of fonts are already available as a package, be it on your SUSE distribution or in the M17N:fonts (http://download.opensuse.org/repositories/M17N:/ fonts/) repository. Add the repository to your list using the following command. For example, to add a repository for SLE 12: sudo zypper ar http://download.opensuse.org/repositories/M17N:/fonts/SLE_12_SP4/ To search for your FONT_FAMILY_NAME use this command: sudo zypper se ''FONT_FAMILY_NAME*fonts'' 290 Installing Fonts SLES 12 SP418.1.5 Configuring the Appearance of Fonts Depending on the rendering medium, and font size, the result may be unsatisfactory. For example, an average monitor these days has a resolution of 100dpi which makes pixels too big and glyphs look clunky. There are several algorithms available to deal with low resolutions, such as anti-aliasing (grayscale smoothing), hinting (tting to the grid), or subpixel rendering (tripling resolution in one direction). These algorithms can also dier from one font format to another. Important: Patent Issues with Subpixel Rendering Subpixel rendering is not used in SUSE distributions. Although FreeType2 has support for this algorithm, it is covered by several patents expiring at the end of the year 2019. Therefore, setting subpixel rendering options in Fontcong has no eect unless the system has a FreeType2 library with subpixel rendering compiled in. Via Fontcong, it is possible to select a rendering algorithms for every font individually or for a set of fonts. 18.1.5.1 Configuring Fonts via sysconfig SUSE Linux Enterprise Server comes with a sysconfig layer above Fontcong. This is a good starting point for experimenting with font conguration. To change the default settings, edit the conguration le /etc/sysconfig/fonts-config . (or use the YaST syscong module). After you have edited the le, run fonts-config : sudo /usr/sbin/fonts-config Restart the application to make the eect visible. Keep in mind the following issues: A few applications do need not to be restarted. For example, Firefox re-reads Fontcong conguration from time to time. Newly created or reloaded tabs get new font congurations later. The fonts-config script is called automatically after every package installation or removal (if not, it is a bug of the font software package). Every syscong variable can be temporarily overridden by the fonts-config command line option. See fonts-config --help for details. 291 Configuring the Appearance of Fonts SLES 12 SP4There are several syscong variables which can be altered. See man 1 fonts-config or the help page of the YaST syscong module. The following variables are examples: Usage of Rendering Algorithms Consider FORCE_HINTSTYLE , FORCE_AUTOHINT , FORCE_BW , FORCE_BW_MONOSPACE , USE_EMBEDDED_BITMAPS and EMBEDDED_BITMAP_LANGAGES Preference Lists of Generic Aliases Use PREFER_SANS_FAMILIES , PREFER_SERIF_FAMILIES , PREFER_MONO_FAMILIES and SEARCH_METRIC_COMPATIBLE The following list provides some conguration examples, sorted from the “most readable” fonts (more contrast) to “most beautiful” (more smoothed). Bitmap Fonts Prefer bitmap fonts via the PREFER_*_FAMILIES variables. Follow the example in the help section for these variables. Be aware that these fonts are rendered black and white, not smoothed and that bitmap fonts are available in several sizes only. Consider using SEARCH_METRIC_COMPATIBLE="no" to disable metric compatibility-driven family name substitutions. Scalable Fonts Rendered Black and White Scalable fonts rendered without antialiasing can result in a similar outcome to bitmap fonts, while maintaining font scalability. Use well hinted fonts like the Liberation families. Unfortunately, there is a lack of well hinted fonts though. Set the following variable to force this method: FORCE_BW="yes" Monospaced Fonts Rendered Black and White Render monospaced fonts without antialiasing only, otherwise use default settings: FORCE_BW_MONOSPACE="yes" Default Settings All fonts are rendered with antialiasing. Well hinted fonts will be rendered with the byte code interpreter (BCI) and the rest with autohinter ( hintstyle=hintslight ). Leave all relevant syscong variables to the default setting. CFF Fonts 292 Configuring the Appearance of Fonts SLES 12 SP4Use fonts in CFF format. They can be considered also more readable than the default TrueType fonts given the current improvements in FreeType2. Try them out by following the example of PREFER_*_FAMILIES . Possibly make them more dark and bold with: SEARCH_METRIC_COMPATIBLE="no" as they are rendered by hintstyle=hintslight by default. Also consider using: SEARCH_METRIC_COMPATIBLE="no" Autohinter Exclusively Even for a well hinted font, use FreeType2''s autohinter. That can lead to thicker, sometimes fuzzier letter shapes with lower contrast. Set the following variable to activate this: FORCE_AUTOHINTER="yes" Use FORCE_HINTSTYLE to control the level of hinting. 18.1.5.2 Diving into Fontconfig XML Fontcong''s conguration format is the eXtensible Markup Language (XML). These few examples are not a complete reference, but a brief overview. Details and other inspiration can be found in man 5 fonts-conf or in /etc/fonts/conf.d/ . The central Fontcong conguration le is /etc/fonts/fonts.conf , which—along other work —includes the whole /etc/fonts/conf.d/ directory. To customize Fontcong, there are two places where you can insert your changes: FONTCONFIG CONFIGURATION FILES 1. System-wide changes. Edit the le /etc/fonts/local.conf (by default, it contains an empty fontconfig element). 2. User-specific changes. Edit the le ~/.config/fontconfig/fonts.conf . Place Fontcong conguration les in the ~/.config/fontconfig/conf.d/ directory. User-specic changes overwrite any system-wide settings. Note: Deprecated User Configuration File The le ~/.fonts.conf is marked as deprecated and should not be used anymore. Use ~/.config/fontconfig/fonts.conf instead. 293 Configuring the Appearance of Fonts SLES 12 SP4Every conguration le needs to have a fontconfig element. As such, the minimal le looks like this: If the default directories are not enough, insert the dir element with the respective directory: /usr/share/fonts2 Fontcong searches recursively for fonts. Font-rendering algorithms can be chosen with following Fontcong snippet (see Example 18.1, “Specifying Rendering Algorithms”): EXAMPLE 18.1: SPECIFYING RENDERING ALGORITHMS FAMILY_NAME true true false hintfull Various properties of fonts can be tested. For example, the element can test for the font family (as shown in the example), size interval, spacing, font format, and others. When abandoning completely, all elements will be applied to every font (global change). EXAMPLE 18.2: ALIASES AND FAMILY NAME SUBSTITUTIONS Rule 1 294 Configuring the Appearance of Fonts SLES 12 SP4 Alegreya SC serif Rule 2 serif Droid Serif Rule 3 serif STIXGeneral The rules from Example 18.2, “Aliases and Family Name Substitutions” create a prioritized family list (PFL). Depending on the element, dierent actions are performed: from Rule 1 This rule adds a serif family name at the end of the PFL. from Rule 2 This rule adds “Droid Serif” just before the rst occurrence of serif in the PFL, whenever Alegreya SC is in PFL. from Rule 3 This rule adds a “STIXGeneral” family name just after the rst occurrence of the serif family name in the PFL. Putting this together, when snippets occur in the order Rule 1 - Rule 2 - Rule 3 and the user requests “Alegreya SC”, then the PFL is created as depicted in Table 18.1, “Generating PFL from Fontconfig rules”. 295 Configuring the Appearance of Fonts SLES 12 SP4TABLE 18.1: GENERATING PFL FROM FONTCONFIG RULES Order Current PFL Request Alegreya SC Rule 1 Alegreya SC , serif Rule 2 Alegreya SC , Droid Serif , serif Rule 3 Alegreya SC , Droid Serif , serif , STIXGeneral In Fontcong''s metrics, the family name has the highest priority over other patterns, like style, size, etc. Fontcong checks which family is currently installed on the system. If “Alegreya SC” is installed, then Fontcong returns it. If not, it asks for “Droid Serif”, etc. Be careful. When the order of Fontcong snippets is changed, Fontcong can return dierent results, as depicted in Table 18.2, “Results from Generating PFL from Fontconfig Rules with Changed Order”. TABLE 18.2: RESULTS FROM GENERATING PFL FROM FONTCONFIG RULES WITH CHANGED ORDER Order Current PFL Note Request Alegreya SC Same request performed. Rule 2 Alegreya SC serif not in PFL, nothing is substituted Rule 3 Alegreya SC serif not in PFL, nothing is substituted Rule 1 Alegreya SC , serif Alegreya SC present in PFL, substitution is performed Note: Implication Think of the alias as a classication or inclusion of this group (if not installed). As the example shows, should always precede the and aliases of that group. 296 Configuring the Appearance of Fonts SLES 12 SP4 classication is not limited to the generic aliases serif, sans-serif and monospace. See /usr/share/fontconfig/conf.avail/30-metric-aliases.conf for a complex example. The following Fontcong snippet in Example 18.3, “Aliases and Family Name Substitutions” creates a serif group. Every family in this group could substitute others when a former font is not installed. EXAMPLE 18.3: ALIASES AND FAMILY NAME SUBSTITUTIONS Alegreya SC serif Droid Serif serif STIXGeneral serif serif Droid Serif STIXGeneral Alegreya SC Priority is given by the order in the alias. Similarly, stronger aliases can be used. Example 18.2, “Aliases and Family Name Substitutions” is expanded by Example 18.4, “Aliases and Family Names Substitutions”. EXAMPLE 18.4: ALIASES AND FAMILY NAMES SUBSTITUTIONS Rule 4 297 Configuring the Appearance of Fonts SLES 12 SP4 serif Liberation Serif Rule 5 serif DejaVu Serif The expanded conguration from Example 18.4, “Aliases and Family Names Substitutions” would lead to the following PFL evolution: TABLE 18.3: RESULTS FROM GENERATING PFL FROM FONTCONFIG RULES Order Current PFL Request Alegreya SC Rule 1 Alegreya SC , serif Rule 2 Alegreya SC , Droid Serif , serif Rule 3 Alegreya SC , Droid Serif , serif , STIXGeneral Rule 4 Alegreya SC , Droid Serif , serif , Liberation Serif , STIXGeneral Rule 5 Alegreya SC , Droid Serif , DejaVu Serif , serif , Liberation Serif , STIXGeneral 298 Configuring the Appearance of Fonts SLES 12 SP4Note: Implications. In case multiple declarations for the same generic name exist, the declaration that is parsed last “wins”. If possible, do not use after user ( /etc/fonts/conf.d/*-user.conf ) when creating a system-wide conguration. In case multiple before user in the system-wide conguration. Every declaration overwrites declarations for the same generic name. If the administrator wants to allow the user to utilize and not only , the administrator should not use in the system- wide conguration. On the other hand, as users mostly use , this should not have any detrimental eect. We also see the use of in system-wide congurations. 18.2 For More Information Install the packages xorg-docs to get more in-depth information about X11. man 5 xorg.conf tells you more about the format of the manual conguration (if needed). More information on the X11 development can be found on the project''s home page at http://www.x.org . Drivers are found in xf86-video-* packages, for example xf86-video-nv . Many of the drivers delivered with these packages are described in detail in the related manual page. For example, if you use the nv driver, nd more information about this driver in man 4 nv . Information about third-party drivers should be available in /usr/share/doc/packages/ . For example, the documentation of x11-video-nvidiaG03 is available in / usr/share/doc/packages/x11-video-nvidiaG03 after the package was installed. 299 For More Information SLES 12 SP419 Accessing File Systems with FUSE FUSE is the acronym for le system in user space. This means you can congure and mount a le system as an unprivileged user. Normally, you need to be root for this task. FUSE alone is a kernel module. Combined with plug-ins, it allows you to extend FUSE to access almost all le systems like remote SSH connections, ISO images, and more. 19.1 Configuring FUSE Before you can use FUSE, you need to install the package fuse . Depending which le system you want to use, you need additional plug-ins available as separate packages. Generally you do not need to congure FUSE. However, it is a good idea to create a directory where all your mount points are combined. For example, you can create a directory ~/mounts and insert your subdirectories for your dierent le systems there. 19.2 Mounting an NTFS Partition NTFS, the New Technology File System, is the default le system of Windows. Since under normal circumstances the unprivileged user cannot mount NTFS block devices using the external FUSE library, the process of mounting a Windows partition described below requires root privileges. 1. Become root and install the package ntfs-3g . It is available in SUSE Linux Enterprise Workstation Extension. 2. Create a directory that is to be used as a mount point, for example ~/mounts/windows . 3. Find out which Windows partition you need. Use YaST and start the partitioner module to see which partition belongs to Windows, but do not modify anything. Alternatively, become root and execute /sbin/fdisk -l . Look for partitions with a partition type of HPFS/NTFS . 4. Mount the partition in read-write mode. Replace the placeholder DEVICE with your respective Windows partition: ntfs-3g /dev/DEVICE MOUNT POINT 300 Configuring FUSE SLES 12 SP4To use your Windows partition in read-only mode, append -o ro : ntfs-3g /dev/DEVICE MOUNT POINT -o ro The command ntfs-3g uses the current user (UID) and group (GID) to mount the given device. If you want to set the write permissions to a dierent user, use the command id USER to get the output of the UID and GID values. Set it with: id tux uid=1000(tux) gid=100(users) groups=100(users),16(dialout),33(video) ntfs-3g /dev/DEVICE MOUNT POINT -o uid=1000,gid=100 Find additional options in the man page. To unmount the resource, run fusermount -u MOUNT POINT . 19.3 For More Information See the home page http://fuse.sourceforge.net of FUSE for more information. 301 For More Information SLES 12 SP420 Managing Kernel Modules Although Linux is a monolithic kernel, it can be extended using kernel modules. These are special objects that can be inserted into the kernel and removed on demand. In practical terms, kernel modules make it possible to add and remove drivers and interfaces that are not included in the kernel itself. Linux provides several commands for managing kernel modules. 20.1 Listing Loaded Modules with lsmod and modinfo Use the lsmod command to view what kernel modules are currently loaded. The output of the command may look as follows: tux > lsmod Module Size Used by snd_usb_audio 188416 2 snd_usbmidi_lib 36864 1 snd_usb_audio hid_plantronics 16384 0 snd_rawmidi 36864 1 snd_usbmidi_lib snd_seq_device 16384 1 snd_rawmidi fuse 106496 3 nfsv3 45056 1 nfs_acl 16384 1 nfsv3 The output is divided into three columns. The Module column lists the names of the loaded modules, while the Size column displays the size of each module. The Used by column shows the number of referring modules and their names. Note that this list may be incomplete. To view detailed information about a specic kernel module, use the modinfo MODULE_NAME command, where MODULE_NAME is the name of the desired kernel module. Note that the modinfo binary resides in the /sbin directory that is not in the user''s PATH environment variable. This means that you must specify the full path to the binary when running modinfo command as a regular user: $ /sbin/modinfo kvm filename: /lib/modules/4.12.14-94.37-default/kernel/arch/x86/kvm/kvm.ko license: GPL author: Qumranet srcversion: BDFD8098BEEA517CB75959B depends: irqbypass 302 Listing Loaded Modules with lsmod and modinfo SLES 12 SP4intree: Y vermagic: 4.4.57-18.3-default SMP mod_unload modversions signer: openSUSE Secure Boot Signkey sig_key: 03:32:FA:9C:BF:0D:88:BF:21:92:4B:0D:E8:2A:09:A5:4D:5D:EF:C8 sig_hashalgo: sha256 parm: ignore_msrs:bool parm: min_timer_period_us:uint parm: kvmclock_periodic_sync:bool parm: tsc_tolerance_ppm:uint parm: lapic_timer_advance_ns:uint parm: halt_poll_ns:uint parm: halt_poll_ns_grow:int parm: halt_poll_ns_shrink:int 20.2 Adding and Removing Kernel Modules While it is possible to use insmod and rmmod to add and remove kernel modules, it is recommended to use the modprobe tool instead. modprobe oers several important advantages, including automatic dependency resolution and blacklisting. When used without any parameters, the modprobe command installs a specied kernel module. modprobe must be run with root privileges: tux > sudo modprobe acpi To remove a kernel module, use the -r parameter: sudo modprobe -r acpi 20.2.1 Loading Kernel Modules Automatically on Boot Instead of loading kernel modules manually, you can load them automatically during the boot process using the system-modules-load.service service. To enable a kernel module, add a .conf le to the /etc/modules-load.d/ directory. It is good practice to give the conguration le the same name as the module, for example: /etc/modules-load.d/rt2800usb.conf The conguration le must contain the name of the desired kernel module (for example, rt2800usb ). 303 Adding and Removing Kernel Modules SLES 12 SP4The described technique allows you to load kernel modules without any parameters. If you need to load a kernel module with specic options, add a conguration le to the /etc/ modprobe.d/ directory instead. The le must have the .conf extension. The name of the le should adhere to the following naming convention: priority-modulename.conf , for example: 50-thinkfan.conf . The conguration le must contain the name of the kernel module and the desired parameters. You can use the example command below to create a conguration le containing the name of the kernel module and its parameters: echo "options thinkpad_acpi fan_control=1" | sudo tee /etc/modprobe.d/thinkfan.conf Note: Loading Kernel Modules Most kernel modules are loaded by the system automatically when a device is detected or user space requests specic functionality. Thus, adding modules manually to /etc/ modules-load.d/ is rarely required. 20.2.2 Blacklisting Kernel Modules with modprobe Blacklisting a kernel module prevents it from loading during the boot process. This can be useful when you want to disable a module that you suspect is causing problems on your system. Note that you can still load blacklisted kernel modules manually using the insmod or modprobe tools. To blacklist a module, add the blacklist MODULE_NAME line to the /etc/modprobe.d/50- blacklist.conf le. For example: blacklist nouveau Run the mkinitrd command as root to generate a new initrd image, then reboot your machine. These steps can be performed using the following command: su echo "blacklist nouveau" >> /etc/modprobe.d/50-blacklist.conf && mkinitrd && reboot To disable a kernel module temporarily only, blacklist it on-the-y during the boot. To do this, press the E key when you see the boot screen. This drops you into a minimal editor that allows you to modify boot parameters. Locate the line that looks as follows: linux /boot/vmlinuz...splash= silent quiet showopts 304 Blacklisting Kernel Modules with modprobe SLES 12 SP4Add the modprobe.blacklist=MODULE_NAME command to the end of the line. For example: linux /boot/vmlinuz...splash= silent quiet showopts modprobe.blacklist=nouveau Press F10 or Ctrl – X to boot with the specied conguration. To blacklist a kernel module permanently via GRUB, open the /etc/default/grub le for editing, and add the modprobe.blacklist=MODULE_NAME option to the GRUB_CMD_LINUX command. Then run the sudo grub2-mkconfig -o /boot/grub2/grub.cfg command to enable the changes. 305 Blacklisting Kernel Modules with modprobe SLES 12 SP421 Dynamic Kernel Device Management with udev The kernel can add or remove almost any device in a running system. Changes in the device state (whether a device is plugged in or removed) need to be propagated to user space. Devices need to be congured when they are plugged in and recognized. Users of a certain device need to be informed about any changes in this device''s recognized state. udev provides the needed infrastructure to dynamically maintain the device node les and symbolic links in the /dev directory. udev rules provide a way to plug external tools into the kernel device event processing. This allows you to customize udev device handling by adding certain scripts to execute as part of kernel device handling, or request and import additional data to evaluate during device handling. 21.1 The /dev Directory The device nodes in the /dev directory provide access to the corresponding kernel devices. With udev , the /dev directory reects the current state of the kernel. Every kernel device has one corresponding device le. If a device is disconnected from the system, the device node is removed. The content of the /dev directory is kept on a temporary le system and all les are rendered at every system start-up. Manually created or modied les do not, by design, survive a reboot. Static les and directories that should always be in the /dev directory regardless of the state of the corresponding kernel device can be created with systemd-tmples. The conguration les are found in /usr/lib/tmpfiles.d/ and /etc/tmpfiles.d/ ; for more information, see the systemd-tmpfiles(8) man page. 21.2 Kernel uevents and udev The required device information is exported by the sysfs le system. For every device the kernel has detected and initialized, a directory with the device name is created. It contains attribute les with device-specic properties. Every time a device is added or removed, the kernel sends a uevent to notify udev of the change. The udev daemon reads and parses all rules from the /usr/lib/udev/rules.d/*.rules and /etc/udev/rules.d/*.rules les at start-up and keeps them in memory. If rules les are 306 The /dev Directory SLES 12 SP4changed, added or removed, the daemon can reload their in-memory representation with the command udevadm control --reload . For more details on udev rules and their syntax, refer to Section 21.6, “Influencing Kernel Device Event Handling with udev Rules”. Every received event is matched against the set of provides rules. The rules can add or change event environment keys, request a specic name for the device node to create, add symbolic links pointing to the node or add programs to run after the device node is created. The driver core uevents are received from a kernel netlink socket. 21.3 Drivers, Kernel Modules and Devices The kernel bus drivers probe for devices. For every detected device, the kernel creates an internal device structure while the driver core sends a uevent to the udev daemon. Bus devices identify themselves by a specially-formatted ID, which tells what kind of device it is. Usually these IDs consist of vendor and product ID and other subsystem-specic values. Every bus has its own scheme for these IDs, called MODALIAS . The kernel takes the device information, composes a MODALIAS ID string from it and sends that string along with the event. For a USB mouse, it looks like this: MODALIAS=usb:v046DpC03Ed2000dc00dsc00dp00ic03isc01ip02 Every device driver carries a list of known aliases for devices it can handle. The list is contained in the kernel module le itself. The program depmod reads the ID lists and creates the le modules.alias in the kernel''s /lib/modules directory for all currently available modules. With this infrastructure, module loading is as easy as calling modprobe for every event that carries a MODALIAS key. If modprobe $MODALIAS is called, it matches the device alias composed for the device with the aliases provided by the modules. If a matching entry is found, that module is loaded. All this is automatically triggered by udev . 21.4 Booting and Initial Device Setup All device events happening during the boot process before the udev daemon is running are lost, because the infrastructure to handle these events resides on the root le system and is not available at that time. To cover that loss, the kernel provides a uevent le located in the device directory of every device in the sysfs le system. By writing add to that le, the kernel resends the same event as the one lost during boot. A simple loop over all uevent les in /sys triggers all events again to create the device nodes and perform device setup. 307 Drivers, Kernel Modules and Devices SLES 12 SP4As an example, a USB mouse present during boot may not be initialized by the early boot logic, because the driver is not available at that time. The event for the device discovery was lost and failed to nd a kernel module for the device. Instead of manually searching for connected devices, udev requests all device events from the kernel after the root le system is available, so the event for the USB mouse device runs again. Now it nds the kernel module on the mounted root le system and the USB mouse can be initialized. From user space, there is no visible dierence between a device coldplug sequence and a device discovery during runtime. In both cases, the same rules are used to match and the same congured programs are run. 21.5 Monitoring the Running udev Daemon The program udevadm monitor can be used to visualize the driver core events and the timing of the udev event processes. UEVENT[1185238505.276660] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1 (usb) UDEV [1185238505.279198] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1 (usb) UEVENT[1185238505.279527] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0 (usb) UDEV [1185238505.285573] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0 (usb) UEVENT[1185238505.298878] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/ input10 (input) UDEV [1185238505.305026] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/ input10 (input) UEVENT[1185238505.305442] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/ input10/mouse2 (input) UEVENT[1185238505.306440] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/ input10/event4 (input) UDEV [1185238505.325384] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/ input10/event4 (input) UDEV [1185238505.342257] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/ input10/mouse2 (input) The UEVENT lines show the events the kernel has sent over netlink. The UDEV lines show the nished udev event handlers. The timing is printed in microseconds. The time between UEVENT and UDEV is the time udev took to process this event or the udev daemon has delayed its execution to synchronize this event with related and already running events. For example, events for hard disk partitions always wait for the main disk device event to nish, because the partition events may rely on the data that the main disk event has queried from the hardware. 308 Monitoring the Running udev Daemon SLES 12 SP4udevadm monitor --env shows the complete event environment: ACTION=add DEVPATH=/devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10 SUBSYSTEM=input SEQNUM=1181 NAME="Logitech USB-PS/2 Optical Mouse" PHYS="usb-0000:00:1d.2-1/input0" UNIQ="" EV=7 KEY=70000 0 0 0 0 REL=103 MODALIAS=input:b0003v046DpC03Ee0110-e0,1,2,k110,111,112,r0,1,8,amlsfw udev also sends messages to syslog. The default syslog priority that controls which messages are sent to syslog is specied in the udev conguration le /etc/udev/udev.conf . The log priority of the running daemon can be changed with udevadm control --log_priority= LEVEL/ NUMBER . 21.6 Influencing Kernel Device Event Handling with udev Rules A udev rule can match any property the kernel adds to the event itself or any information that the kernel exports to sysfs . The rule can also request additional information from external programs. Events are matched against all rules provided in the directories /usr/lib/udev/ rules.d/ (for default rules) and /etc/udev/rules.d (system-specic conguration). Every line in the rules le contains at least one key value pair. There are two kinds of keys, match and assignment keys. If all match keys match their values, the rule is applied and the assignment keys are assigned the specied value. A matching rule may specify the name of the device node, add symbolic links pointing to the node or run a specied program as part of the event handling. If no matching rule is found, the default device node name is used to create the device node. Detailed information about the rule syntax and the provided keys to match or import data are described in the udev man page. The following example rules provide a basic introduction to udev rule syntax. The example rules are all taken from the udev default rule set /usr/lib/udev/rules.d/50-udev-default.rules . EXAMPLE 21.1: EXAMPLE udev RULES # console 309 Influencing Kernel Device Event Handling with udev Rules SLES 12 SP4KERNEL=="console", MODE="0600", OPTIONS="last_rule" # serial devices KERNEL=="ttyUSB*", ATTRS{product}=="[Pp]alm*Handheld*", SYMLINK+="pilot" # printer SUBSYSTEM=="usb", KERNEL=="lp*", NAME="usb/%k", SYMLINK+="usb%k", GROUP="lp" # kernel firmware loader SUBSYSTEM=="firmware", ACTION=="add", RUN+="firmware.sh" The console rule consists of three keys: one match key ( KERNEL ) and two assign keys ( MODE , OPTIONS ). The KERNEL match rule searches the device list for any items of the type console . Only exact matches are valid and trigger this rule to be executed. The MODE key assigns special permissions to the device node, in this case, read and write permissions to the owner of this device only. The OPTIONS key makes this rule the last rule to be applied to any device of this type. Any later rule matching this particular device type does not have any eect. The serial devices rule is not available in 50-udev-default.rules anymore, but it is still worth considering. It consists of two match keys ( KERNEL and ATTRS ) and one assign key ( SYMLINK ). The KERNEL key searches for all devices of the ttyUSB type. Using the * wild card, this key matches several of these devices. The second match key, ATTRS , checks whether the product attribute le in sysfs for any ttyUSB device contains a certain string. The assign key ( SYMLINK ) triggers the addition of a symbolic link to this device under /dev/pilot . The operator used in this key ( += ) tells udev to additionally perform this action, even if previous or later rules add other symbolic links. As this rule contains two match keys, it is only applied if both conditions are met. The printer rule deals with USB printers and contains two match keys which must both apply to get the entire rule applied ( SUBSYSTEM and KERNEL ). Three assign keys deal with the naming for this device type ( NAME ), the creation of symbolic device links ( SYMLINK ) and the group membership for this device type ( GROUP ). Using the * wild card in the KERNEL key makes it match several lp printer devices. Substitutions are used in both, the NAME and the SYMLINK keys to extend these strings by the internal device name. For example, the symbolic link to the rst lp USB printer would read /dev/usblp0 . The kernel firmware loader rule makes udev load additional rmware by an external helper script during runtime. The SUBSYSTEM match key searches for the firmware subsystem. The ACTION key checks whether any device belonging to the firmware subsystem has been added. The RUN+= key triggers the execution of the firmware.sh script to locate the rmware that is to be loaded. 310 Influencing Kernel Device Event Handling with udev Rules SLES 12 SP4Some general characteristics are common to all rules: Each rule consists of one or more key value pairs separated by a comma. A key''s operation is determined by the operator. udev rules support several operators. Each given value must be enclosed by quotation marks. Each line of the rules le represents one rule. If a rule is longer than one line, use \ to join the dierent lines as you would do in shell syntax. udev rules support a shell-style pattern that matches the * , ? , and [] patterns. udev rules support substitutions. 21.6.1 Using Operators in udev Rules Creating keys you can choose from several operators, depending on the type of key you want to create. Match keys will normally be used to nd a value that either matches or explicitly mismatches the search value. Match keys contain either of the following operators: == Compare for equality. If the key contains a search pattern, all results matching this pattern are valid. != Compare for non-equality. If the key contains a search pattern, all results matching this pattern are valid. Any of the following operators can be used with assign keys: = Assign a value to a key. If the key previously consisted of a list of values, the key resets and only the single value is assigned. += Add a value to a key that contains a list of entries. := Assign a nal value. Disallow any later change by later rules. 311 Using Operators in udev Rules SLES 12 SP421.6.2 Using Substitutions in udev Rules udev rules support the use of placeholders and substitutions. Use them in a similar fashion as you would do in any other scripts. The following substitutions can be used with udev rules: %r , $root The device directory, /dev by default. %p , $devpath The value of DEVPATH . %k , $kernel The value of KERNEL or the internal device name. %n , $number The device number. %N , $tempnode The temporary name of the device le. %M , $major The major number of the device. %m , $minor The minor number of the device. %s{ATTRIBUTE} , $attr{ATTRIBUTE} The value of a sysfs attribute (specied by ATTRIBUTE ). %E{VARIABLE} , $env{VARIABLE} The value of an environment variable (specied by VARIABLE ). %c , $result The output of PROGRAM . %% The % character. $$ The $ character. 312 Using Substitutions in udev Rules SLES 12 SP421.6.3 Using udev Match Keys Match keys describe conditions that must be met before a udev rule can be applied. The following match keys are available: ACTION The name of the event action, for example, add or remove when adding or removing a device. DEVPATH The device path of the event device, for example, DEVPATH=/bus/pci/drivers/ipw3945 to search for all events related to the ipw3945 driver. KERNEL The internal (kernel) name of the event device. SUBSYSTEM The subsystem of the event device, for example, SUBSYSTEM=usb for all events related to USB devices. ATTR{FILENAME} sysfs attributes of the event device. To match a string contained in the vendor attribute le name, you could use ATTR{vendor}=="On[sS]tream" , for example. KERNELS Let udev search the device path upwards for a matching device name. SUBSYSTEMS Let udev search the device path upwards for a matching device subsystem name. DRIVERS Let udev search the device path upwards for a matching device driver name. ATTRS{FILENAME} Let udev search the device path upwards for a device with matching sysfs attribute values. ENV{KEY} The value of an environment variable, for example, ENV{ID_BUS}="ieee1394 to search for all events related to the FireWire bus ID. PROGRAM 313 Using udev Match Keys SLES 12 SP4Let udev execute an external program. To be successful, the program must return with exit code zero. The program''s output, printed to STDOUT, is available to the RESULT key. RESULT Match the output string of the last PROGRAM call. Either include this key in the same rule as the PROGRAM key or in a later one. 21.6.4 Using udev Assign Keys In contrast to the match keys described above, assign keys do not describe conditions that must be met. They assign values, names and actions to the device nodes maintained by udev . NAME The name of the device node to be created. After a rule has set a node name, all other rules with a NAME key for this node are ignored. SYMLINK The name of a symbolic link related to the node to be created. Multiple matching rules can add symbolic links to be created with the device node. You can also specify multiple symbolic links for one node in one rule using the space character to separate the symbolic link names. OWNER, GROUP, MODE The permissions for the new device node. Values specied here overwrite anything that has been compiled in. ATTR{KEY} Specify a value to be written to a sysfs attribute of the event device. If the == operator is used, this key is also used to match against the value of a sysfs attribute. ENV{KEY} Tell udev to export a variable to the environment. If the == operator is used, this key is also used to match against an environment variable. RUN Tell udev to add a program to the list of programs to be executed for this device. Keep in mind to restrict this to very short tasks to avoid blocking further events for this device. LABEL Add a label where a GOTO can jump to. 314 Using udev Assign Keys SLES 12 SP4GOTO Tell udev to skip several rules and continue with the one that carries the label referenced by the GOTO key. IMPORT{TYPE} Load variables into the event environment such as the output of an external program. udev imports variables of several types. If no type is specied, udev tries to determine the type itself based on the executable bit of the le permissions. program tells udev to execute an external program and import its output. file tells udev to import a text le. parent tells udev to import the stored keys from the parent device. WAIT_FOR_SYSFS Tells udev to wait for the specied sysfs le to be created for a certain device. For example, WAIT_FOR_SYSFS="ioerr_cnt" informs udev to wait until the ioerr_cnt le has been created. OPTIONS The OPTION key may have several values: last_rule tells udev to ignore all later rules. ignore_device tells udev to ignore this event completely. ignore_remove tells udev to ignore all later remove events for the device. all_partitions tells udev to create device nodes for all available partitions on a block device. 21.7 Persistent Device Naming The dynamic device directory and the udev rules infrastructure make it possible to provide stable names for all disk devices—regardless of their order of recognition or the connection used for the device. Every appropriate block device the kernel creates is examined by tools with special knowledge about certain buses, drive types or le systems. Along with the dynamic kernel-provided device node name, udev maintains classes of persistent symbolic links pointing to the device: /dev/disk 315 Persistent Device Naming SLES 12 SP4|-- by-id | |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B -> ../../sda | |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B-part1 -> ../../sda1 | |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B-part6 -> ../../sda6 | |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B-part7 -> ../../sda7 | |-- usb-Generic_STORAGE_DEVICE_02773 -> ../../sdd | `-- usb-Generic_STORAGE_DEVICE_02773-part1 -> ../../sdd1 |-- by-label | |-- Photos -> ../../sdd1 | |-- SUSE10 -> ../../sda7 | `-- devel -> ../../sda6 |-- by-path | |-- pci-0000:00:1f.2-scsi-0:0:0:0 -> ../../sda | |-- pci-0000:00:1f.2-scsi-0:0:0:0-part1 -> ../../sda1 | |-- pci-0000:00:1f.2-scsi-0:0:0:0-part6 -> ../../sda6 | |-- pci-0000:00:1f.2-scsi-0:0:0:0-part7 -> ../../sda7 | |-- pci-0000:00:1f.2-scsi-1:0:0:0 -> ../../sr0 | |-- usb-02773:0:0:2 -> ../../sdd | |-- usb-02773:0:0:2-part1 -> ../../sdd1 `-- by-uuid |-- 159a47a4-e6e6-40be-a757-a629991479ae -> ../../sda7 |-- 3e999973-00c9-4917-9442-b7633bd95b9e -> ../../sda6 `-- 4210-8F8C -> ../../sdd1 21.8 Files used by udev /sys/* Virtual le system provided by the Linux kernel, exporting all currently known devices. This information is used by udev to create device nodes in /dev /dev/* Dynamically created device nodes and static content created with systemd-tmples; for more information, see the systemd-tmpfiles(8) man page. The following les and directories contain the crucial elements of the udev infrastructure: /etc/udev/udev.conf Main udev conguration le. /etc/udev/rules.d/* System-specic udev event matching rules. You can add custom rules here to modify or override the default rules from /usr/lib/udev/rules.d/* . 316 Files used by udev SLES 12 SP4Files are parsed in alphanumeric order. Rules from les with a higher priority modify or override rules with lower priority. The lower the number, the higher the priority. /usr/lib/udev/rules.d/* Default udev event matching rules. The les in this directory are owned by packages and will be overwritten by updates. Do not add, remove or edit les here, use /etc/udev/ rules.d instead. /usr/lib/udev/* Helper programs called from udev rules. /usr/lib/tmpfiles.d/ and /etc/tmpfiles.d/ Responsible for static /dev content. 21.9 For More Information For more information about the udev infrastructure, refer to the following man pages: udev General information about udev , keys, rules and other important conguration issues. udevadm udevadm can be used to control the runtime behavior of udev , request kernel events, manage the event queue and provide simple debugging mechanisms. udevd Information about the udev event managing daemon. 317 For More Information SLES 12 SP422 Live Patching the Linux Kernel Using kGraft This document describes the basic principles of the kGraft live patching technology and provides usage guidelines for the SLE Live Patching service. kGraft is a live patching technology for runtime patching of the Linux kernel, without stopping the kernel. This maximizes system uptime, and thus system availability, which is important for mission-critical systems. By allowing dynamic patching of the kernel, the technology also encourages users to install critical security updates without deferring them to a scheduled downtime. A kGraft patch is a kernel module, intended for replacing whole functions in the kernel. kGraft primarily oers in-kernel infrastructure for integration of the patched code with base kernel code at runtime. SLE Live Patching is a service provided on top of regular SUSE Linux Enterprise Server maintenance. kGraft patches distributed through SLE Live Patching supplement regular SLES maintenance updates. Common update stack and procedures can be used for SLE Live Patching deployment. The information provided in this document relates to the AMD64/Intel 64 and POWER architectures. In case you use a dierent architecture, the procedures may dier. 22.1 Advantages of kGraft Live kernel patching using kGraft is especially useful for quick response in emergencies (when serious vulnerabilities are known and should be xed when possible or there are serious system stability issues with a known x). It is not used for scheduled updates where time is not critical. Typical use cases for kGraft include systems like memory databases with huge amounts of RAM, where boot-up times of 15 minutes or more are not uncommon, large simulations that need weeks or months without a restart, or infrastructure building blocks providing continuous service to many consumers. The main advantage of kGraft is that it never requires stopping the kernel, not even for a short time period. 318 Advantages of kGraft SLES 12 SP4A kGraft patch is a .ko kernel module in a RPM package. It is inserted into the kernel using the insmod command when the package is installed or updated. kGraft replaces whole functions in the kernel, even if they are being executed. An updated kGraft module can replace an existing patch if necessary. kGraft is also lean—it contains only a small amount of code, because it leverages other standard Linux technologies. 22.2 Low-level Function of kGraft kGraft uses the ftrace infrastructure to perform patching. The following describes the implementation on the AMD64/Intel 64 architecture. To patch a kernel function, kGraft needs some space at the start of the function to insert a jump to a new function. This space is allocated during kernel compilation by GCC with function proling turned on. In particular, a 5-byte call instruction is injected to the start of kernel functions. When such instrumented kernel is booting, proling calls are replaced by 5-byte NOP (no operation) instructions. After patching starts, the rst byte is replaced by the INT3 (breakpoint) instruction. This ensures atomicity of the 5-byte instruction replacement. The other four bytes are replaced by the address to the new function. Finally, the rst byte is replaced by the JMP (long jump) opcode. Inter-processor non-maskable interrupts (IPI NMI) are used throughout the process to ush speculative decoding queues of other CPUs in the system. This allows switching to the new function without ever stopping the kernel, not even for a very short moment. The interruptions by IPI NMIs can be measured in microseconds and are not considered service interruptions as they happen while the kernel is running in any case. Callers are never patched. Instead, the caller''s NOPs are replaced by a JMP to the new function. JMP instructions remain forever. This takes care of function pointers, including in structures, and does not require saving any old data for the possibility of un-patching. However, these steps alone would not be good enough: since the functions would be replaced non-atomically, a new xed function in one part of the kernel could still be calling an old function elsewhere or vice versa. If the semantics of the function interfaces changed in the patch, chaos would ensue. Thus, until all functions are replaced, kGraft uses an approach based on trampolines and similar to RCU (read-copy-update), to ensure a consistent view of the world to each user space thread, kernel thread and kernel interrupt. A per-thread ag is set on each kernel entry and exit. This 319 Low-level Function of kGraft SLES 12 SP4way, an old function would always call another old function and a new function always a new one. Once all processes have the "new universe" ag set, patching is complete, trampolines can be removed and the code can operate at full speed without performance impact other than an extra-long jump for each patched function. 22.3 Installing kGraft Patches This section describes the activation of the SUSE Linux Enterprise Live Patching extension and the installation of kGraft patches. 22.3.1 Activation of SLE Live Patching To activate SLE Live Patching on your system, follow these steps: 1. If your SLES system is not yet registered, register it. Registration can be done during the system installation or later using the YaST Product Registration module ( yast2 registration ). After registration, click Yes to see the list of available online updates. If your SLES system is already registered, but SLE Live Patching is not yet activated, open the YaST Product Registration module ( yast2 registration ) and click Select Extensions. 2. Select SUSE Linux Enterprise Live Patching 12 in the list of available extensions and click Next. 3. Conrm the license terms and click Next. 4. Enter the SLE Live Patching registration code and click Next. 5. Check the Installation Summary and selected Patterns. The pattern Live Patching should be selected for installation. 6. Click Accept to complete the installation. This will install the base kGraft components on your system together with the initial live patch. 22.3.2 Updating System 1. SLE Live Patching updates are distributed in a form that allows using standard SLE update stack for patch application. The initial live patch can be updated using zypper patch , YaST Online Update or equivalent method. 320 Installing kGraft Patches SLES 12 SP42. The kernel is patched automatically during the package installation. However, invocations of the old kernel functions are not completely eliminated until all sleeping processes wake up and get out of the way. This can take a considerable amount of time. Despite this, sleeping processes that use the old kernel functions are not considered a security issue. Nevertheless, in the current version of kGraft, it is not possible to apply another kGraft patch until all processes cross the kernel-user space boundary to stop using patched functions from the previous patch. To see the global status of patching, check the ag in /sys/kernel/kgraft/ in_progress . The value 1 signies the existence of sleeping processes that still need to be woken (the patching is still in progress). The value 0 signies that all processes are using solely the patched functions and patching has nished already. Alternatively, use the kgr status command to obtain the same information. The ag can be checked on a per-process basis too. Check the number in /proc/ PROCESS_NUMBER/kgr_in_progress for each process individually. Again, the value 1 signies sleeping process that still needs to be woken. Alternatively, use the kgr blocking command to output the list of sleeping processes. 22.4 Patch Lifecycle Expiration dates of live patches can be accessed with zypper lifecycle . Make sure that the package lifecycle-data-sle-live-patching is installed. tux > zypper lifecycle Product end of support Codestream: SUSE Linux Enterprise Server 12 2024-10-31 SUSE Linux Enterprise Server 12 SP2 n/a* Extension end of support SUSE Linux Enterprise Live Patching 2017-10-31 Package end of support if different from product: SUSEConnect Now, installed 0.2.41-18.1, update available 0.2.42-19.3.1 apache2-utils Now *) See https://www.suse.com/lifecycle for latest information 321 Patch Lifecycle SLES 12 SP4When the expiration date of a patch is reached, no further live patches for this kernel version will be supplied. Plan an update of your kernel before the end of the live patch lifecycle period. 22.5 Removing a kGraft Patch To remove a kGraft patch, use the following procedure: 1. First remove the patch itself using Zypper: zypper rm kgraft-patch-3_12_32-25-default 2. Then reboot the machine. 22.6 Stuck Kernel Execution Threads Kernel threads need to be prepared to handle kGraft. Third-party software may not be ready for kGraft adoption and its kernel modules may spawn kernel execution threads. These threads will block the patching process indenitely. As an emergency measure kGraft oers the possibility to force nishing of the patching process without waiting for all execution threads to cross the safety checkpoint. This can be achieved by writing 0 into /sys/kernel/kgraft/in_progress . Consult SUSE Support before performing this procedure. 22.7 The kgr Tool Several kGraft management tasks can be simplied with the kgr tool. The available commands are: kgr status Displays the overall status of kGraft patching ( ready or in_progress ). kgr patches Displays the list of loaded kGraft patches. kgr blocking Lists processes that are preventing kGraft patching from nishing. By default only the PIDs are listed. Specifying -v prints command lines if available. Another -v displays also stack traces. 322 Removing a kGraft Patch SLES 12 SP4For detailed information, see man kgr . 22.8 Scope of kGraft Technology kGraft is based on replacing functions. Data structure alteration can be accomplished only indirectly with kGraft. As a result, changes to kernel data structure require special care and, if the change is too large, rebooting might be required. kGraft also might not be able to handle situations where one compiler is used to compile the old kernel and another compiler is used for compiling the patch. Because of the way kGraft works, support for third-party modules that are spawning kernel threads is limited. 22.9 Scope of SLE Live Patching Fixes for SUSE Common Vulnerability Scoring System (CVSS) level 7+ vulnerabilities and bug xes related to system stability or data corruption will be shipped in the scope of SLE Live Patching. It might not be possible to produce a live patch for all kinds of xes fullling the above criteria. SUSE reserves the right to skip xes where production of a kernel live patch is unviable because of technical reasons. For more information on CVSS 3.0, which is the base for the SUSE CVSS rating, see https://www.first.org/cvss/ . 22.10 Interaction with the Support Processes While resolving a technical diculty with SUSE Support, you may receive a so-called Program Temporary Fix (PTF). PTFs may be issued for various packages including those forming the base of SLE Live Patching. kGraft PTFs complying with the conditions described in the previous section can be installed as usual and SUSE will ensure that the system in question does not need to be rebooted and that future live updates are applied cleanly. PTFs issued for the base kernel disrupt the live patching process. First, installing the PTF kernel means a reboot as the kernel cannot be replaced as a whole at runtime. Second, another reboot is needed to replace the PTF with any regular maintenance updates for which the live patches are issued. 323 Scope of kGraft Technology SLES 12 SP4PTFs for other packages in SLE Live Patching can be treated like regular PTFs with the usual guarantees. 324 Interaction with the Support Processes SLES 12 SP423 Special System Features This chapter starts with information about various software packages, the virtual consoles and the keyboard layout. We talk about software components like bash , cron and logrotate , because they were changed or enhanced during the last release cycles. Even if they are small or considered of minor importance, users should change their default behavior, because these components are often closely coupled with the system. The chapter concludes with a section about language and country-specic settings (I18N and L10N). 23.1 Information about Special Software Packages The programs bash , cron , logrotate , locate , ulimit and free are very important for system administrators and many users. Man pages and info pages are two useful sources of information about commands, but both are not always available. GNU Emacs is a popular and very congurable text editor. 23.1.1 The bash Package and /etc/profile Bash is the default system shell. When used as a login shell, it reads several initialization les. Bash processes them in the order they appear in this list: 1. /etc/profile 2. ~/.profile 3. /etc/bash.bashrc 4. ~/.bashrc Make custom settings in ~/.profile or ~/.bashrc . To ensure the correct processing of these les, it is necessary to copy the basic settings from /etc/skel/.profile or /etc/ skel/.bashrc into the home directory of the user. It is recommended to copy the settings from /etc/skel after an update. Execute the following shell commands to prevent the loss of personal adjustments: mv ~/.bashrc ~/.bashrc.old 325 Information about Special Software Packages SLES 12 SP4cp /etc/skel/.bashrc ~/.bashrc mv ~/.profile ~/.profile.old cp /etc/skel/.profile ~/.profile Then copy personal adjustments back from the *.old les. 23.1.2 The cron Package Use cron to run commands automatically in the background at predened times. cron uses specially formatted time tables, and the tool comes with several default ones. Users can also specify custom tables, if needed. The cron tables are located in /var/spool/cron/tabs . /etc/crontab serves as a systemwide cron table. Enter the user name to run the command directly after the time table and before the command. In Example 23.1, “Entry in /etc/crontab”, root is entered. Package-specic tables, located in /etc/cron.d , have the same format. See the cron man page ( man cron ). EXAMPLE 23.1: ENTRY IN /ETC/CRONTAB 1-59/5 * * * * root test -x /usr/sbin/atrun && /usr/sbin/atrun You cannot edit /etc/crontab by calling the command crontab -e . This le must be loaded directly into an editor, then modied and saved. A number of packages install shell scripts to the directories /etc/cron.hourly , /etc/ cron.daily , /etc/cron.weekly and /etc/cron.monthly , whose execution is controlled by /usr/lib/cron/run-crons . /usr/lib/cron/run-crons is run every 15 minutes from the main table ( /etc/crontab ). This guarantees that processes that may have been neglected can be run at the proper time. To run the hourly , daily or other periodic maintenance scripts at custom times, remove the time stamp les regularly using /etc/crontab entries (see Example 23.2, “/etc/crontab: Remove Time Stamp Files”, which removes the hourly one before every full hour, the daily one once a day at 2:14 a.m., etc.). EXAMPLE 23.2: /ETC/CRONTAB: REMOVE TIME STAMP FILES 59 * * * * root rm -f /var/spool/cron/lastrun/cron.hourly 14 2 * * * root rm -f /var/spool/cron/lastrun/cron.daily 29 2 * * 6 root rm -f /var/spool/cron/lastrun/cron.weekly 326 The cron Package SLES 12 SP444 2 1 * * root rm -f /var/spool/cron/lastrun/cron.monthly Or you can set DAILY_TIME in /etc/sysconfig/cron to the time at which cron.daily should start. The setting of MAX_NOT_RUN ensures that the daily tasks get triggered to run, even if the user did not turn on the computer at the specied DAILY_TIME for a longer time. The maximum value of MAX_NOT_RUN is 14 days. The daily system maintenance jobs are distributed to various scripts for reasons of clarity. They are contained in the package aaa_base . /etc/cron.daily contains, for example, the components suse.de-backup-rpmdb , suse.de-clean-tmp or suse.de-cron-local . 23.1.3 Stopping Cron Status Messages To avoid the mail-ood caused by cron status messages, the default value of SEND_MAIL_ON_NO_ERROR in /etc/sysconfig/cron is set to " no " for new installations. Even with this setting to " no ", cron data output will still be sent to the MAILTO address, as documented in the cron man page. In the update case it is recommended to set these values according to your needs. 23.1.4 Log Files: Package logrotate There are several system services (daemons) that, along with the kernel itself, regularly record the system status and specic events onto log les. This way, the administrator can regularly check the status of the system at a certain point in time, recognize errors or faulty functions and troubleshoot them with pinpoint precision. These log les are normally stored in /var/log as specied by FHS and grow on a daily basis. The logrotate package helps control the growth of these les. For more details refer to Book “System Analysis and Tuning Guide”, Chapter 3 “Analyzing and Managing System Log Files”, Section 3.3 “Managing Log Files with logrotate”. 23.1.5 The locate Command locate , a command for quickly nding les, is not included in the standard scope of installed software. If desired, install the package mlocate , the successor of the package findutils- locate . The updatedb process is started automatically every night or about 15 minutes after booting the system. 327 Stopping Cron Status Messages SLES 12 SP423.1.6 The ulimit Command With the ulimit (user limits) command, it is possible to set limits for the use of system resources and to have these displayed. ulimit is especially useful for limiting available memory for applications. With this, an application can be prevented from co-opting too much of the system resources and slowing or even hanging up the operating system. ulimit can be used with various options. To limit memory usage, use the options listed in Table 23.1, “ulimit: Setting Resources for the User”. TABLE 23.1: ulimit: SETTING RESOURCES FOR THE USER -m The maximum resident set size -v The maximum amount of virtual memory available to the shell -s The maximum size of the stack -c The maximum size of core les created -a All current limits are reported Systemwide default entries are set in /etc/profile . Editing this le directly is not recommended, because changes will be overwritten during system upgrades. To customize systemwide prole settings, use /etc/profile.local . Per-user settings should be made in ~USER/.bashrc . EXAMPLE 23.3: ULIMIT: SETTINGS IN ~/.BASHRC # Limits maximum resident set size (physical memory): ulimit -m 98304 # Limits of virtual memory: ulimit -v 98304 Memory allocations must be specied in KB. For more detailed information, see man bash . Important: ulimit Support Not all shells support ulimit directives. PAM (for example, pam_limits ) oers comprehensive adjustment possibilities as an alternative to ulimit . 328 The ulimit Command SLES 12 SP423.1.7 The free Command The free command displays the total amount of free and used physical memory as well as swap space in the system and the buers and cache consumed by the kernel. The concept of available RAM dates back to before the days of unied memory management. The slogan free memory is bad memory applies well to Linux. As a result, Linux has always made the eort to balance out caches without actually allowing free or unused memory. The kernel does not have direct knowledge of any applications or user data. Instead, it manages applications and user data in a page cache. If memory runs short, parts of it are written to the swap partition or to les, from which they can initially be read using the mmap command (see man mmap ). The kernel also contains other caches, such as the slab cache, where the caches used for network access are stored. This may explain the dierences between the counters in /proc/meminfo . Most, but not all, of them can be accessed via /proc/slabinfo . However, if your goal is to nd out how much RAM is currently being used, nd this information in /proc/meminfo . 23.1.8 Man Pages and Info Pages For some GNU applications (such as tar), the man pages are no longer maintained. For these commands, use the --help option to get a quick overview of the info pages, which provide more in-depth instructions. Info is GNU''s hypertext system. Read an introduction to this system by entering info info . Info pages can be viewed with Emacs by entering emacs -f info or directly in a console with info . You can also use tkinfo, xinfo or the help system to view info pages. 23.1.9 Selecting Man Pages Using the man Command To read a man page enter man MAN_PAGE . If a man page with the same name exists in dierent sections, they will all be listed with the corresponding section numbers. Select the one to display. If you do not enter a section number within a few seconds, the rst man page will be displayed. To change this to the default system behavior, set MAN_POSIXLY_CORRECT=1 in a shell initialization le such as ~/.bashrc . 329 The free Command SLES 12 SP423.1.10 Settings for GNU Emacs GNU Emacs is a complex work environment. The following sections cover the conguration les processed when GNU Emacs is started. More information is available at http://www.gnu.org/ software/emacs/ . On start-up, Emacs reads several les containing the settings of the user, system administrator and distributor for customization or preconguration. The initialization le ~/.emacs is installed to the home directories of the individual users from /etc/skel . .emacs , in turn, reads the le /etc/skel/.gnu-emacs . To customize the program, copy .gnu-emacs to the home directory (with cp /etc/skel/.gnu-emacs ~/.gnu-emacs ) and make the desired settings there. .gnu-emacs denes the le ~/.gnu-emacs-custom as custom-file . If users make settings with the customize options in Emacs, the settings are saved to ~/.gnu-emacs-custom . With SUSE Linux Enterprise Server, the emacs package installs the le site-start.el in the directory /usr/share/emacs/site-lisp . The le site-start.el is loaded before the initialization le ~/.emacs . Among other things, site-start.el ensures that special conguration les distributed with Emacs add-on packages, such as psgml , are loaded automatically. Conguration les of this type are located in /usr/share/emacs/site- lisp , too, and always begin with suse-start- . The local system administrator can specify systemwide settings in default.el . More information about these les is available in the Emacs info le under Init File: info:/ emacs/InitFile . Information about how to disable the loading of these les (if necessary) is also provided at this location. The components of Emacs are divided into several packages: The base package emacs . emacs-x11 (usually installed): the program with X11 support. emacs-nox : the program without X11 support. emacs-info : online documentation in info format. 330 Settings for GNU Emacs SLES 12 SP4emacs-el : the uncompiled library les in Emacs Lisp. These are not required at runtime. Numerous add-on packages can be installed if needed: emacs-auctex (LaTeX), psgml (SGML and XML), gnuserv (client and server operation) and others. 23.2 Virtual Consoles Linux is a multiuser and multitasking system. The advantages of these features can be appreciated even on a stand-alone PC system. In text mode, there are six virtual consoles available. Switch between them using Alt – F1 through Alt – F6 . The seventh console is reserved for X and the tenth console shows kernel messages. To switch to a console from X without shutting it down, use Ctrl – Alt – F1 to Ctrl – Alt – F6 . To return to X, press Alt – F7 . 23.3 Keyboard Mapping To standardize the keyboard mapping of programs, changes were made to the following les: /etc/inputrc /etc/X11/Xmodmap /etc/skel/.emacs /etc/skel/.gnu-emacs /etc/skel/.vimrc /etc/csh.cshrc /etc/termcap /usr/share/terminfo/x/xterm /usr/share/X11/app-defaults/XTerm /usr/share/emacs/VERSION/site-lisp/term/*.el These changes only aect applications that use terminfo entries or whose conguration les are changed directly ( vi , emacs , etc.). Applications not shipped with the system should be adapted to these defaults. Under X, the compose key (multikey) can be enabled as explained in /etc/X11/Xmodmap . Further settings are possible using the X Keyboard Extension (XKB). This extension is also used by the desktop environment GNOME (gswitchit). 331 Virtual Consoles SLES 12 SP4Tip: For More Information Information about XKB is available in the documents listed in /usr/share/doc/ packages/xkeyboard-config (part of the xkeyboard-config package). 23.4 Language and Country-Specific Settings The system is, to a very large extent, internationalized and can be modied for local needs. Internationalization (I18N) allows specic localization (L10N). The abbreviations I18N and L10N are derived from the rst and last letters of the words and, in between, the number of letters omitted. Settings are made with LC_ variables dened in the le /etc/sysconfig/language . This refers not only to native language support, but also to the categories Messages (Language), Character Set, Sort Order, Time and Date, Numbers and Money. Each of these categories can be dened directly with its own variable or indirectly with a master variable in the le language (see the locale man page). RC_LC_MESSAGES , RC_LC_CTYPE , RC_LC_COLLATE , RC_LC_TIME , RC_LC_NUMERIC , RC_LC_MONETARY These variables are passed to the shell without the RC_ prex and represent the listed categories. The shell proles concerned are listed below. The current setting can be shown with the command locale . RC_LC_ALL This variable, if set, overwrites the values of the variables already mentioned. RC_LANG If none of the previous variables are set, this is the fallback. By default, only RC_LANG is set. This makes it easier for users to enter their own values. ROOT_USES_LANG A yes or no variable. If set to no , root always works in the POSIX environment. The variables can be set with the YaST syscong editor. The value of such a variable contains the language code, country code, encoding and modier. The individual components are connected by special characters: LANG=[[_].[@]] 332 Language and Country-Specific Settings SLES 12 SP423.4.1 Some Examples You should always set the language and country codes together. Language settings follow the standard ISO 639 available at http://www.evertype.com/standards/iso639/iso639-en.html and http://www.loc.gov/standards/iso639-2/ . Country codes are listed in ISO 3166, see http:// en.wikipedia.org/wiki/ISO_3166 . It only makes sense to set values for which usable description les can be found in /usr/lib/ locale . Additional description les can be created from the les in /usr/share/i18n using the command localedef . The description les are part of the glibc-i18ndata package. A description le for en_US.UTF-8 (for English and United States) can be created with: localedef -i en_US -f UTF-8 en_US.UTF-8 LANG=en_US.UTF-8 This is the default setting if American English is selected during installation. If you selected another language, that language is enabled but still with UTF-8 as the character encoding. LANG=en_US.ISO-8859-1 This sets the language to English, country to United States and the character set to ISO-8859-1 . This character set does not support the Euro sign, but it can be useful sometimes for programs that have not been updated to support UTF-8 . The string dening the charset ( ISO-8859-1 in this case) is then evaluated by programs like Emacs. LANG=en_IE@euro The above example explicitly includes the Euro sign in a language setting. This setting is obsolete now, as UTF-8 also covers the Euro symbol. It is only useful if an application supports ISO-8859-15 and not UTF-8. Changes to /etc/sysconfig/language are activated by the following process chain: For the Bash: /etc/profile reads /etc/profile.d/lang.sh which, in turn, analyzes /etc/sysconfig/language . For tcsh: At login, /etc/csh.login reads /etc/profile.d/lang.csh which, in turn, analyzes /etc/sysconfig/language . 333 Some Examples SLES 12 SP4This ensures that any changes to /etc/sysconfig/language are available at the next login to the respective shell, without having to manually activate them. Users can override the system defaults by editing their ~/.bashrc accordingly. For example, if you do not want to use the system-wide en_US for program messages, include LC_MESSAGES=es_ES so that messages are displayed in Spanish instead. 23.4.2 Locale Settings in ~/.i18n If you are not satised with locale system defaults, change the settings in ~/.i18n according to the Bash scripting syntax. Entries in ~/.i18n override system defaults from /etc/sysconfig/ language . Use the same variable names but without the RC_ name space prexes. For example, use LANG instead of RC_LANG : LANG=cs_CZ.UTF-8 LC_COLLATE=C 23.4.3 Settings for Language Support Files in the category Messages are, as a rule, only stored in the corresponding language directory (like en ) to have a fallback. If you set LANG to en_US and the message le in /usr/ share/locale/en_US/LC_MESSAGES does not exist, it falls back to /usr/share/locale/en/ LC_MESSAGES . A fallback chain can also be dened, for example, for Breton to French or for Galician to Spanish to Portuguese: LANGUAGE="br_FR:fr_FR" LANGUAGE="gl_ES:es_ES:pt_PT" If desired, use the Norwegian variants Nynorsk and Bokmål instead (with additional fallback to no ): LANG="nn_NO" LANGUAGE="nn_NO:nb_NO:no" or LANG="nb_NO" LANGUAGE="nb_NO:nn_NO:no" Note that in Norwegian, LC_TIME is also treated dierently. 334 Locale Settings in ~/.i18n SLES 12 SP4One problem that can arise is a separator used to delimit groups of digits not being recognized properly. This occurs if LANG is set to only a two-letter language code like de , but the denition le glibc uses is located in /usr/share/lib/de_DE/LC_NUMERIC . Thus LC_NUMERIC must be set to de_DE to make the separator denition visible to the system. 23.4.4 For More Information The GNU C Library Reference Manual, Chapter “Locales and Internationalization”. It is included in glibc-info . The package is available from the SUSE Linux Enterprise SDK. The SDK is a module for SUSE Linux Enterprise and is available via an online channel from the SUSE Customer Center. Alternatively, go to http://download.suse.com/ , search for SUSE Linux Enterprise Software Development Kit and download it from there. Refer to Book “Deployment Guide”, Chapter 14 “Installing Modules, Extensions, and Third Party Add-On Products” for details. Markus Kuhn, UTF-8 and Unicode FAQ for Unix/Linux, currently at http://www.cl.cam.ac.uk/ ~mgk25/unicode.html . Unicode-HOWTO by Bruno Haible, available at http://tldp.org/HOWTO/Unicode- HOWTO-1.html . 335 For More Information SLES 12 SP424 Persistent Memory This chapter contains additional information about using SUSE Linux Enterprise Server with non-volatile main memory, also known as Persistent Memory, comprising one or more NVDIMMs. 24.1 Introduction Persistent memory is a new type of computer storage, combining speeds approaching those of normal dynamic RAM (DRAM) along with RAM''s byte-by-byte addressability, plus the permanence of solid-state disks (SSDs). Like conventional RAM, it is installed directly into motherboard memory slots. As such, it is supplied in the same physical form factor as RAM—as DIMMs. These are known as NVDIMMs: non-volatile dual inline memory modules. Unlike RAM, though, persistent memory is also similar to ash-based SSDs in several ways. Both are based on forms of solid-state memory circuitry, but despite this, both provide non-volatile storage: their contents are retained when the system is powered o or restarted. For both forms of medium, writing data is slower than reading it, and both support a limited number of rewrite cycles. Finally, also like SSDs, sector-level access to persistent memory is possible if that is more suitable for a particular application. Dierent models use dierent forms of electronic storage medium, such as Intel 3D XPoint, or a combination of NAND-ash and DRAM. New forms of non-volatile RAM are also in development. This means that dierent vendors and models of NVDIMM oer dierent performance and durability characteristics. Because the storage technologies involved are in an early stage of development, dierent vendors'' hardware may impose dierent limitations. Thus, the following statements are generalizations. Persistent memory is up to ten times slower than DRAM, but around a thousand times faster than ash storage. It can be rewritten on a byte-by-byte basis rather than ash memory''s whole-sector erase-and-rewrite process. Finally, while rewrite cycles are limited, most forms of persistent memory can handle millions of rewrites, compared to the thousands of cycles of ash storage. 336 Introduction SLES 12 SP4This has two important consequences: It is not possible with current technology to run a system with only persistent memory and thus achieve completely non-volatile main memory. You must use a mixture of both conventional RAM and NVDIMMs. The operating system and applications will execute in conventional RAM, with the NVDIMMs providing very fast supplementary storage. The performance characteristics of dierent vendors'' persistent memory mean that it may be necessary for programmers to be aware of the hardware specications of the NVDIMMs in a particular server, including how many NVDIMMs there are and in which memory slots they are tted. This will obviously impact hypervisor use, migration of software between dierent host machines, and so on. This new storage subsystem is dened in version 6 of the ACPI standard. However, libnvdimm supports pre-standard NVDIMMs and they can be used in the same way. 24.2 Terms Region A region is a block of persistent memory that can be divided up into one or more namespaces. You cannot access the persistent memory of a region without rst allocating it to a namespace. Namespace A single contiguously-addressed range of non-volatile storage, comparable to NVM Express SSD namespaces, or to SCSI Logical Units (LUNs). Namespaces appear in the server''s / dev directory as separate block devices. Depending on the method of access required, namespaces can either amalgamate storage from multiple NVDIMMs into larger volumes, or allow it to be partitioned into smaller volumes. Mode Each namespace has a mode that denes which NVDIMM features are enabled for that namespace. Sibling namespaces of the same parent region will always have the same type, but might be congured to have dierent modes. Namespace modes include: raw A memory disk. Does not support DAX. Compatible with other operating systems. sector 337 Terms SLES 12 SP4For legacy le systems which do not checksum metadata. Suitable for small boot volumes. Compatible with other operating systems. fsdax File system-DAX mode. Default if no other mode is specied. Creates a block device ( /dev/pmemX [.Y] ) which supports DAX for ext4 or XFS . devdax Device-DAX mode. Creates a single-character device le ( /dev/daxX.Y ). Does not require le system creation. Type Each namespace and region has a type that denes the way in which the persistent memory associated with that namespace or region can be accessed. A namespace always has the same type as its parent region. There are two dierent types: Persistent Memory and Block Mode. Persistent Memory (PMEM) PMEM storage oers byte-level access, just like RAM. This enables Direct Access (DAX), meaning that accessing the memory bypasses the kernel''s page cache and goes direct to the medium. Additionally, using PMEM, a single namespace can include multiple interleaved NVDIMMs, allowing them all to be accessed as a single device. Block Mode (BLK) BLK access is in sectors, usually of 512 bytes, through a dened access window, the aperture. This behavior is more like a traditional disk drive. This also means that both reads and writes are cached by the kernel. With BLK access, each NVDIMM is accessed as a separate namespace. Some devices support both PMEM and BLK modes. Additionally, some allow the storage to be split into separate namespaces, so that some can be accessed using PMEM and some using BLK. Apart from devdax namespaces, all other types must be formatted with a le system such as ext2 , ext4 or XFS , just as with a conventional drive. Direct Access (DAX) DAX allows persistent memory to be directly mapped into a process''s address space, for example using the mmap system call. This is suitable for directly accessing large amounts of PMEM without using any additional RAM, for registering blocks of PMEM for RDMA, or for directly assigning it to virtual machines. 338 Terms SLES 12 SP4DIMM Physical Address (DPA) A memory address as an oset into a single DIMM''s memory; that is, starting from zero as the lowest addressable byte on that DIMM. Label Metadata stored on the NVDIMM, such as namespace denitions. This can be accessed using DSMs. Device-specific method (DSM) ACPI method to access the rmware on an NVDIMM. 24.3 Use Cases 24.3.1 PMEM with DAX It is important to note that this form of memory access is not transactional. In the event of a power outage or other system failure, data may not be completely written into storage. PMEM storage is only suitable if the application can handle the situation of partially-written data. 24.3.1.1 Applications that benefit from large amounts of byte-addressable storage. If the server will host an application that can directly use large amounts of fast storage on a byte-by-byte basis, the programmer can use the mmap system call to place blocks of persistent memory directly into the application''s address space, without using any additional system RAM. 24.3.1.2 Avoiding Use of the Kernel Page Cache If you wish to conserve the use of RAM for the page cache, and instead give it to your applications. For instance, non-volatile memory could be dedicated to holding virtual machine (VM) images. As these would not be cached, this would reduce the cache usage on the host, allowing more VMs per host. 339 Use Cases SLES 12 SP424.3.2 PMEM with BTT This is useful when you want to use the persistent memory on a set of NVDIMMs as a disk-like pool of very fast storage. To applications, such devices just appear as very fast SSDs and can be used like any other storage device. For example, LVM can be layered on top of the non-volatile storage and will work as normal. The advantage of BTT is that sector write atomicity is guaranteed, so even sophisticated applications that depend on data integrity will keep working. Media error reporting works through standard error-reporting channels. 24.3.3 BLK storage Although it is more robust against single-device failure, this requires additional management, as each NVDIMM appears as a separate device. Thus, PMEM with BTT is generally preferred. Note BLK storage is deprecated and is not supported in later versions of SUSE Linux Enterprise Server. 24.4 Tools for Managing Persistent Memory To manage persistent memory, it is necessary to install the ndctl package. This also installs the libndctl package, which provides a set of user-space libraries to congure NVDIMMs. These tools work via the libnvdimm library, which supports three types of NVDIMMs: PMEM BLK Simultaneous PMEM and BLK The ndctl utility has a helpful set of man pages, accessible with the command: ndctl help subcommand 340 PMEM with BTT SLES 12 SP4To see a list of available subcommands, use: ndctl --list-cmds The available subcommands include: version Displays the current version of the NVDIMM support tools. enable-namespace Makes the specied namespace available for use. disable-namespace Prevents the specied namespace from being used. create-namespace Creates a new namespace from the specied storage devices. destroy-namespace Removes the specied namespace. enable-region Makes the specied region available for use. disable-region Prevents the specied region from being used. zero-labels Erases the metadata from a device. read-labels Retrieves the metadata of the specied device. list Displays available devices. help Displays information about using the tool. 341 Tools for Managing Persistent Memory SLES 12 SP424.5 Setting Up Persistent Memory 24.5.1 Viewing Available NVDIMM Storage The ndctl list command can be used to list all available NVDIMMs in a system. In the following example, the system has three NVDIMMs which are in a single, triple-channel interleaved set. root # ndctl list --dimms [ { "dev":"nmem2", "id":"8089-00-0000-12325476" }, { "dev":"nmem1", "id":"8089-00-0000-11325476" }, { "dev":"nmem0", "id":"8089-00-0000-10325476" } ] With a dierent parameter, ndctl list will also list the available regions. Note Regions may not appear in numerical order. Note that although there are only three NVDIMMs, they appear as four regions. root # ndctl list --regions [ { "dev":"region1", "size":68182605824, "available_size":68182605824, "type":"blk" }, 342 Setting Up Persistent Memory SLES 12 SP4{ "dev":"region3", "size":202937204736, "available_size":202937204736, "type":"pmem", "iset_id":5903239628671731251 }, { "dev":"region0", "size":68182605824, "available_size":68182605824, "type":"blk" }, { "dev":"region2", "size":68182605824, "available_size":68182605824, "type":"blk" } ] The space is available in two dierent forms: either as three separate 64 GB regions of type BLK, or as one combined 189 GB region of type PMEM which presents all the space on the three interleaved NVDIMMs as a single volume. Note that the displayed value for available_size is the same as that for size . This means that none of the space has been allocated yet. 24.5.2 Configuring the Storage as a Single PMEM Namespace with DAX For the rst example, we will congure our three NVDIMMs into a single PMEM namespace with Direct Access (DAX). The rst step is to create a new namespace. root # ndctl create-namespace --type=pmem --mode=fsdax --map=memory { "dev":"namespace3.0", "mode":"memory", "size":199764213760, "uuid":"dc8ebb84-c564-4248-9e8d-e18543c39b69", "blockdev":"pmem3" } 343 Configuring the Storage as a Single PMEM Namespace with DAX SLES 12 SP4This creates a block device /dev/pmem3 , which supports DAX. The 3 in the device name is inherited from the parent region number, in this case region3 . The --map=memory option sets aside part of the PMEM storage space on the NVDIMMs so that it can be used to allocate internal kernel data structures called struct pages . This allows the new PMEM namespace to be used with features such as O_DIRECT I/O and RDMA . The reservation of some persistent memory for kernel data structures is why the resulting PMEM namespace has a smaller capacity than the parent PMEM region. Next, we verify that the new block device is available to the operating system: root # fdisk -l /dev/pmem3 Disk /dev/pmem3: 186 GiB, 199764213760 bytes, 390164480 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Before it can be used, like any other drive, it must be formatted. In this example, we format it with XFS: root # mkfs.xfs /dev/pmem3 meta-data=/dev/pmem3 isize=256 agcount=4, agsize=12192640 blks = sectsz=4096 attr=2, projid32bit=1 = crc=0 finobt=0, sparse=0 data = bsize=4096 blocks=48770560, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0 ftype=1 log =internal log bsize=4096 blocks=23813, version=2 = sectsz=4096 sunit=1 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 Next, we can mount the new drive onto a directory: root # mount -o dax /dev/pmem3 /mnt/pmem3 Then we can verify that we now have a DAX-capable device: root # mount | grep dax /dev/pmem3 on /mnt/pmem3 type xfs (rw,relatime,attr2,dax,inode64,noquota) The result is that we now have a PMEM namespace formatted with the XFS le system and mounted with DAX. Any mmap() calls to les in that le system will return virtual addresses that directly map to the persistent memory on our NVDIMMs, completely bypassing the page cache. 344 Configuring the Storage as a Single PMEM Namespace with DAX SLES 12 SP4Any fsync or msync calls on les in that le system will still ensure that modied data has been fully written to the NVDIMMs. These calls ush the processor cache lines associated with any pages that have been modied in userspace via mmap mappings. 24.5.2.1 Removing a Namespace Before creating any other type of volume that uses the same storage, we must unmount and then remove this PMEM volume. First, unmount it: root # umount /mnt/pmem3 Then disable the namespace: root # ndctl disable-namespace namespace3.0 disabled 1 namespace Then delete it: root # ndctl destroy-namespace namespace3.0 destroyed 1 namespace 24.5.3 Creating a PMEM Namespace with BTT In the next example, we create a PMEM namespace that uses BTT. root # ndctl create-namespace --type=pmem --mode=sector { "dev":"namespace3.0", "mode":"sector", "uuid":"51ab652d-7f20-44ea-b51d-5670454f8b9b", "sector_size":4096, "blockdev":"pmem3s" } Next, verify that the new device is present: root # fdisk -l /dev/pmem3s Disk /dev/pmem3s: 188.8 GiB, 202738135040 bytes, 49496615 sectors Units: sectors of 1 * 4096 = 4096 bytes Sector size (logical/physical): 4096 bytes / 4096 bytes 345 Creating a PMEM Namespace with BTT SLES 12 SP4I/O size (minimum/optimal): 4096 bytes / 4096 bytes Like the DAX-capable PMEM namespace we previously congured, this BTT-capable PMEM namespace consumes all the available storage on the NVDIMMs. Note The trailing s in the device name ( /dev/pmem3s ) stands for sector and can be used to easily distinguish PMEM and BLK namespaces that are congured to use the BTT. The volume can be formatted and mounted as in the previous example. The PMEM namespace shown here cannot use DAX. Instead it uses the BTT to provide sector write atomicity. On each sector write through the PMEM block driver, the BTT will allocate a new sector to receive the new data. The BTT atomically updates its internal mapping structures after the new data is fully written so the newly written data will be available to applications. If the power fails at any point during this process, the write will be completely lost and the application will have access to its old data, still intact. This prevents the condition known as "torn sectors". This BTT-enabled PMEM namespace can be formatted and used with a le system just like any other standard block device. It cannot be used with DAX. However, mmap mappings for les on this block device will use the page cache. Note In both these examples, space from all the NVDIMMs is combined into a single volume. Just as with a non-redundant disk array, this means that if any individual NVDIMM suers an error, the contents of the entire volume could be lost. The more NVDIMMs are included in the volume, the higher the chance of such an error. 24.5.3.1 Removing the PMEM Volume As in the previous example, before re-allocating the space, we must rst remove the volume and the namespace: root # ndctl disable-namespace namespace3.0 disabled 1 namespace root # ndctl destroy-namespace namespace3.0 destroyed 1 namespace 346 Creating a PMEM Namespace with BTT SLES 12 SP424.5.4 Creating BLK Namespaces In this example, we will create three separate BLK devices: one per NVDIMM. One advantage of this approach is that if any individual NVDIMM fails, the other volumes will be unaected. Note The commands must be repeated for each namespace. root # ndctl create-namespace --type=blk --mode=sector { "dev":"namespace1.0", "mode":"sector", "uuid":"fed466bd-90f6-460b-ac81-ad1f08716602", "sector_size":4096, "blockdev":"ndblk1.0s" } root # ndctl create-namespace --type=blk --mode=sector { "dev":"namespace0.0", "mode":"sector", "uuid":"12a29b6f-b951-4d08-8dbc-8dea1a2bb32d", "sector_size":4096, "blockdev":"ndblk0.0s" } root # ndctl create-namespace --type=blk --mode=sector { "dev":"namespace2.0", "mode":"sector", "uuid":"7c84dab5-cc08-452a-b18d-53e430bf8833", "sector_size":4096, "blockdev":"ndblk2.0s" } Next, we can verify that the new devices exist: root # fdisk -l /dev/ndblk* Disk /dev/ndblk0.0s: 63.4 GiB, 68115001344 bytes, 16629639 sectors Units: sectors of 1 * 4096 = 4096 bytes Sector size (logical/physical): 4096 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes 347 Creating BLK Namespaces SLES 12 SP4Disk /dev/ndblk1.0s: 63.4 GiB, 68115001344 bytes, 16629639 sectors Units: sectors of 1 * 4096 = 4096 bytes Sector size (logical/physical): 4096 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk /dev/ndblk2.0s: 63.4 GiB, 68115001344 bytes, 16629639 sectors Units: sectors of 1 * 4096 = 4096 bytes Sector size (logical/physical): 4096 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes The block devices generated for BLK namespaces are named /dev/ndblkX.Y where X is the parent region number and Y is a unique namespace number within that region. So, /dev/ ndblk2.0s is child namespace number 0 of region 2. As in the previous example, the trailing s means that this namespace is congured to use the BTT—in other words, for sector-based access. Because they are accessed via a block window , programs cannot use DAX, but accesses will be cached. As ever, these devices must all be formatted and mounted before they can be used. 24.6 For More Information More about this topic can be found in the following list: Persistent Memory Wiki (https://nvdimm.wiki.kernel.org/) Contains instructions for conguring NVDIMM systems, information about testing, and links to specications related to NVDIMM enabling. This site is developing as NVDIMM support in Linux is developing. Persistent Memory Programming (http://pmem.io/) Information about conguring, using and programming systems with non-volatile memory under Linux and other operating systems. Covers the NVM Library (NVML), which aims to provide useful APIs for programming with persistent memory in userspace. LIBNVDIMM: Non-Volatile Devices (https://www.kernel.org/doc/Documentation/nvdimm/ nvdimm.txt) Aimed at kernel developers, this is part of the Documentation folder in the current Linux kernel tree. It talks about the dierent kernel modules involved in NVDIMM enablement, lays out some technical details of the kernel implementation, and talks about the sysfs interface to the kernel that is used by the ndctl tool. GitHub: pmem/ndctl (https://github.com/pmem/ndctl) 348 For More Information SLES 12 SP4Utility library for managing the libnvdimm subsystem in the Linux kernel. Also contains userspace libraries, as well as unit tests and documentation. 349 For More Information SLES 12 SP4IV Services 25 Time Synchronization with NTP 351 26 The Domain Name System 357 27 DHCP 382 28 Sharing File Systems with NFS 398 29 Samba 410 30 On-Demand Mounting with Autofs 432 31 SLP 440 32 The Apache HTTP Server 444 33 Setting Up an FTP Server with YaST 486 34 The Proxy Server Squid 490 35 Web Based Enterprise Management Using SFCB 51425 Time Synchronization with NTP The NTP (network time protocol) mechanism is a protocol for synchronizing the system time over the network. First, a machine can obtain the time from a server that is a reliable time source. Second, a machine can itself act as a time source for other computers in the network. The goal is twofold—maintaining the absolute time and synchronizing the system time of all machines within a network. Maintaining an exact system time is important in many situations. The built-in hardware clock does often not meet the requirements of applications such as databases or clusters. Manual correction of the system time would lead to severe problems because, for example, a backward leap can cause malfunction of critical applications. Within a network, it is usually necessary to synchronize the system time of all machines, but manual time adjustment is a bad approach. NTP provides a mechanism to solve these problems. The NTP service continuously adjusts the system time with reliable time servers in the network. It further enables the management of local reference clocks, such as radio-controlled clocks. 25.1 Configuring an NTP Client with YaST The NTP daemon ( ntpd ) coming with the ntp package is preset to use the local computer clock as a time reference. Using the hardware clock, however, only serves as a fallback for cases where no time source of better precision is available. YaST simplies the conguration of an NTP client. 25.1.1 Basic Configuration The YaST NTP client conguration (Network Services NTP Conguration) consists of tabs. Set the start mode of ntpd and the server to query on the General Settings tab. Only Manually Select Only Manually, if you want to manually start the ntpd daemon. Synchronize without Daemon Select Synchronize without Daemon to set the system time periodically without a permanently running ntpd . You can set the Interval of the Synchronization in Minutes. Now and On Boot 351 Configuring an NTP Client with YaST SLES 12 SP4Select Now and On Boot to start ntpd automatically when the system is booted. This setting is recommended. 25.1.2 Changing Basic Configuration The servers and other time sources for the client to query are listed in the lower part of the General Settings tab. Modify this list as needed with Add, Edit, and Delete. Display Log provides the possibility to view the log les of your client. Click Add to add a new source of time information. In the following dialog, select the type of source with which the time synchronization should be made. The following options are available: FIGURE 25.1: YAST: NTP SERVER Server In the drop-down Select list (see Figure 25.1, “YaST: NTP Server”), determine whether to set up time synchronization using a time server from your local network (Local NTP Server) or an Internet-based time server that takes care of your time zone (Public NTP Server). For a local time server, click Lookup to start an SLP query for available time servers in your network. Select the most suitable time server from the list of search results and exit the dialog with OK. For a public time server, select your country (time zone) and a suitable 352 Changing Basic Configuration SLES 12 SP4server from the list under Public NTP Server then exit the dialog with OK. In the main dialog, test the availability of the selected server with Test. Options allows you to specify additional options for ntpd . Using Access Control Options, you can restrict the actions that the remote computer can perform with the daemon running on your computer. This eld is enabled only after checking Restrict NTP Service to Congured Servers Only on the Security Settings tab (see Figure 25.2, “Advanced NTP Configuration: Security Settings”). The options correspond to the restrict clauses in /etc/ntp.conf . For example, nomodify notrap noquery disallows the server to modify NTP settings of your computer and to use the trap facility (a remote event logging feature) of your NTP daemon. Using these restrictions is recommended for servers out of your control (for example, on the Internet). Refer to /usr/share/doc/packages/ntp-doc (part of the ntp-doc package) for detailed information. Peer A peer is a machine to which a symmetric relationship is established: it acts both as a time server and as a client. To use a peer in the same network instead of a server, enter the address of the system. The rest of the dialog is identical to the Server dialog. Radio Clock To use a radio clock in your system for the time synchronization, enter the clock type, unit number, device name, and other options in this dialog. Click Driver Calibration to ne-tune the driver. Detailed information about the operation of a local radio clock is available in /usr/share/doc/packages/ntp-doc/refclock.html . Outgoing Broadcast Time information and queries can also be transmitted by broadcast in the network. In this dialog, enter the address to which such broadcasts should be sent. Do not activate broadcasting unless you have a reliable time source like a radio controlled clock. Incoming Broadcast If you want your client to receive its information via broadcast, enter the address from which the respective packets should be accepted in this elds. 353 Changing Basic Configuration SLES 12 SP4FIGURE 25.2: ADVANCED NTP CONFIGURATION: SECURITY SETTINGS In the Security Settings tab (see Figure 25.2, “Advanced NTP Configuration: Security Settings”), determine whether ntpd should be started in a chroot jail. By default, Run NTP Daemon in Chroot Jail is not activated. The chroot jail option increases the security in the event of an attack over ntpd , as it prevents the attacker from compromising the entire system. Restrict NTP Service to Congured Servers Only increases the security of your system by disallowing remote computers to view and modify NTP settings of your computer and to use the trap facility for remote event logging. After being enabled, these restrictions apply to all remote computers, unless you override the access control options for individual computers in the list of time sources in the General Settings tab. For all other remote computers, only querying for local time is allowed. Enable Open Port in Firewall if SuSEFirewall2 is active (which it is by default). If you leave the port closed, it is not possible to establish a connection to the time server. 354 Changing Basic Configuration SLES 12 SP425.2 Manually Configuring NTP in the Network The easiest way to use a time server in the network is to set server parameters. For example, if a time server called ntp.example.com is reachable from the network, add its name to the le /etc/ntp.conf by adding the following line: server ntp.example.com To add more time servers, insert additional lines with the keyword server . After initializing ntpd with the command systemctl start ntp , it takes about one hour until the time is stabilized and the drift le for correcting the local computer clock is created. With the drift le, the systematic error of the hardware clock can be computed when the computer is powered on. The correction is used immediately, resulting in a higher stability of the system time. There are two possible ways to use the NTP mechanism as a client: First, the client can query the time from a known server in regular intervals. With many clients, this approach can cause a high load on the server. Second, the client can wait for NTP broadcasts sent out by broadcast time servers in the network. This approach has the disadvantage that the quality of the server is unknown and a server sending out wrong information can cause severe problems. If the time is obtained via broadcast, you do not need the server name. In this case, enter the line broadcastclient in the conguration le /etc/ntp.conf . To use one or more known time servers exclusively, enter their names in the line starting with servers . 25.3 Setting Up a Local Reference Clock The software package ntpd contains drivers for connecting local reference clocks. A list of supported clocks is available in the ntp-doc package in the le /usr/share/doc/packages/ ntp-doc/refclock.html . Every driver is associated with a number. In NTP, the actual conguration takes place by means of pseudo IP addresses. The clocks are entered in the le / etc/ntp.conf as though they existed in the network. For this purpose, they are assigned special IP addresses in the form 127.127.T.U . Here, T stands for the type of the clock and determines which driver is used and U for the unit, which determines the interface used. Normally, the individual drivers have special parameters that describe conguration details. The le /usr/share/doc/packages/ntp-doc/drivers/driverNN.html (where NN is the number of the driver) provides information about the particular type of clock. For example, the “type 8” clock (radio clock over serial interface) requires an additional mode that species the clock 355 Manually Configuring NTP in the Network SLES 12 SP4more precisely. The Conrad DCF77 receiver module, for example, has mode 5. To use this clock as a preferred reference, specify the keyword prefer . The complete server line for a Conrad DCF77 receiver module would be: server 127.127.8.0 mode 5 prefer Other clocks follow the same pattern. Following the installation of the ntp-doc package, the documentation for NTP is available in the directory /usr/share/doc/packages/ntp-doc . The le /usr/share/doc/packages/ntp-doc/refclock.html provides links to the driver pages describing the driver parameters. 25.4 Clock Synchronization to an External Time Reference (ETR) Support for clock synchronization to an external time reference (ETR) is available. The external time reference sends an oscillator signal and a synchronization signal every 2**20 (2 to the power of 20) microseconds to keep TOD clocks of all connected servers synchronized. For availability two ETR units can be connected to a machine. If the clock deviates for more than the sync-check tolerance all CPUs get a machine check that indicates that the clock is out of sync. If this happens, all DASD I/O to XRC enabled devices is stopped until the clock is synchronized again. The ETR support is activated via two sysfs attributes; run the following commands as root : echo 1 > /sys/devices/system/etr/etr0/online echo 1 > /sys/devices/system/etr/etr1/online 356 Clock Synchronization to an External Time Reference (ETR) SLES 12 SP426 The Domain Name System DNS (domain name system) is needed to resolve the domain names and host names into IP addresses. In this way, the IP address 192.168.2.100 is assigned to the host name jupiter , for example. Before setting up your own name server, read the general information about DNS in Section 16.3, “Name Resolution”. The following conguration examples refer to BIND, the default DNS server. 26.1 DNS Terminology Zone The domain name space is divided into regions called zones. For example, if you have example.com , you have the example section (or zone) of the com domain. DNS server The DNS server is a server that maintains the name and IP information for a domain. You can have a primary DNS server for master zone, a secondary server for slave zone, or a slave server without any zones for caching. Master zone DNS server The master zone includes all hosts from your network and a DNS server master zone stores up-to-date records for all the hosts in your domain. Slave zone DNS server A slave zone is a copy of the master zone. The slave zone DNS server obtains its zone data with zone transfer operations from its master server. The slave zone DNS server responds authoritatively for the zone as long as it has valid (not expired) zone data. If the slave cannot obtain a new copy of the zone data, it stops responding for the zone. Forwarder Forwarders are DNS servers to which your DNS server should send queries it cannot answer. To enable dierent conguration sources in one conguration, netconfig is used (see also man 8 netconfig ). Record 357 DNS Terminology SLES 12 SP4The record is information about name and IP address. Supported records and their syntax are described in BIND documentation. Some special records are: NS record An NS record tells name servers which machines are in charge of a given domain zone. MX record The MX (mail exchange) records describe the machines to contact for directing mail across the Internet. SOA record SOA (Start of Authority) record is the rst record in a zone le. The SOA record is used when using DNS to synchronize data between multiple computers. 26.2 Installation To install a DNS server, start YaST and select Software Software Management. Choose View Patterns and select DHCP and DNS Server. Conrm the installation of the dependent packages to nish the installation process. Alternatively use the following command on the command line: zypper in -t pattern dhcp_dns_server 26.3 Configuration with YaST Use the YaST DNS module to congure a DNS server for the local network. When starting the module for the rst time, a wizard starts, prompting you to make a few decisions concerning administration of the server. Completing this initial setup produces a basic server conguration. Use the expert mode to deal with more advanced conguration tasks, such as setting up ACLs, logging, TSIG keys, and other options. 26.3.1 Wizard Configuration The wizard consists of three steps or dialogs. At the appropriate places in the dialogs, you can enter the expert conguration mode. 358 Installation SLES 12 SP41. When starting the module for the rst time, the Forwarder Settings dialog, shown in Figure 26.1, “DNS Server Installation: Forwarder Settings”, opens. The Local DNS Resolution Policy allows to set the following options: Merging forwarders is disabled Automatic merging Merging forwarders is enabled Custom conguration—If Custom conguration is selected, Custom policy can be specied; by default (with Automatic merging selected), Custom policy is set to auto , but here you can either set interface names or select from the two special policy names STATIC and STATIC_FALLBACK . In Local DNS Resolution Forwarder, specify which service to use: Using system name servers, This name server (bind), or Local dnsmasq server. For more information about all these settings, see man 8 netconfig . FIGURE 26.1: DNS SERVER INSTALLATION: FORWARDER SETTINGS Forwarders are DNS servers to which your DNS server sends queries it cannot answer itself. Enter their IP address and click Add. 359 Wizard Configuration SLES 12 SP42. The DNS Zones dialog consists of several parts and is responsible for the management of zone les, described in Section 26.6, “Zone Files”. For a new zone, provide a name for it in Name. To add a reverse zone, the name must end in .in-addr.arpa . Finally, select the Type (master, slave, or forward). See Figure 26.2, “DNS Server Installation: DNS Zones”. Click Edit to congure other settings of an existing zone. To remove a zone, click Delete. FIGURE 26.2: DNS SERVER INSTALLATION: DNS ZONES 3. In the nal dialog, you can open the DNS port in the rewall by clicking Open Port in Firewall. Then decide whether to start the DNS server when booting (On or O). You can also activate LDAP support. See Figure 26.3, “DNS Server Installation: Finish Wizard”. 360 Wizard Configuration SLES 12 SP4FIGURE 26.3: DNS SERVER INSTALLATION: FINISH WIZARD 26.3.2 Expert Configuration After starting the module, YaST opens a window displaying several conguration options. Completing it results in a DNS server conguration with the basic functions in place: 26.3.2.1 Start-Up Under Start-Up, dene whether the DNS server should be started when the booting the system or manually. To start the DNS server immediately, click Start DNS Server Now. To stop the DNS server, click Stop DNS Server Now. To save the current settings, select Save Settings and Reload DNS Server Now. You can open the DNS port in the rewall with Open Port in Firewall and modify the rewall settings with Firewall Details. By selecting LDAP Support Active, the zone les are managed by an LDAP database. Any changes to zone data written to the LDAP database are picked up by the DNS server when it is restarted or prompted to reload its conguration. 361 Expert Configuration SLES 12 SP426.3.2.2 Forwarders If your local DNS server cannot answer a request, it tries to forward the request to a Forwarder, if congured so. This forwarder may be added manually to the Forwarder List. If the forwarder is not static like in dial-up connections, netcong handles the conguration. For more information about netcong, see man 8 netconfig . 26.3.2.3 Basic Options In this section, set basic server options. From the Option menu, select the desired item then specify the value in the corresponding text box. Include the new entry by selecting Add. 26.3.2.4 Logging To set what the DNS server should log and how, select Logging. Under Log Type, specify where the DNS server should write the log data. Use the system-wide log by selecting System Log or specify a dierent le by selecting File. In the latter case, additionally specify a name, the maximum le size in megabytes and the number of log le versions to store. Further options are available under Additional Logging. Enabling Log All DNS Queries causes every query to be logged, in which case the log le could grow extremely large. For this reason, it is not a good idea to enable this option for other than debugging purposes. To log the data trac during zone updates between DHCP and DNS server, enable Log Zone Updates. To log the data trac during a zone transfer from master to slave, enable Log Zone Transfer. See Figure 26.4, “DNS Server: Logging”. 362 Expert Configuration SLES 12 SP4FIGURE 26.4: DNS SERVER: LOGGING 26.3.2.5 ACLs Use this dialog to dene ACLs (access control lists) to enforce access restrictions. After providing a distinct name under Name, specify an IP address (with or without netmask) under Value in the following fashion: { 192.168.1/24; } The syntax of the conguration le requires that the address ends with a semicolon and is put into curly braces. 26.3.2.6 TSIG Keys The main purpose of TSIGs (transaction signatures) is to secure communications between DHCP and DNS servers. They are described in Section 26.8, “Secure Transactions”. To generate a TSIG key, enter a distinctive name in the eld labeled Key ID and specify the le where the key should be stored (Filename). Conrm your choices with Generate. To use a previously created key, leave the Key ID eld blank and select the le where it is stored under Filename. After that, conrm with Add. 363 Expert Configuration SLES 12 SP426.3.2.7 DNS Zones (Adding a Slave Zone) To add a slave zone, select DNS Zones, choose the zone type Slave, write the name of the new zone, and click Add. In the Zone Editor sub-dialog under Master DNS Server IP, specify the master from which the slave should pull its data. To limit access to the server, select one of the ACLs from the list. 26.3.2.8 DNS Zones (Adding a Master Zone) To add a master zone, select DNS Zones, choose the zone type Master, write the name of the new zone, and click Add. When adding a master zone, a reverse zone is also needed. For example, when adding the zone example.com that points to hosts in a subnet 192.168.1.0/24 , you should also add a reverse zone for the IP-address range covered. By denition, this should be named 1.168.192.in-addr.arpa . 26.3.2.9 DNS Zones (Editing a Master Zone) To edit a master zone, select DNS Zones, select the master zone from the table, and click Edit. The dialog consists of several pages: Basics (the one opened rst), NS Records, MX Records, SOA, and Records. The basic dialog, shown in Figure 26.5, “DNS Server: Zone Editor (Basics)”, lets you dene settings for dynamic DNS and access options for zone transfers to clients and slave name servers. To permit the dynamic updating of zones, select Allow Dynamic Updates as well as the corresponding TSIG key. The key must have been dened before the update action starts. To enable zone transfers, select the corresponding ACLs. ACLs must have been dened already. In the Basics dialog, select whether to enable zone transfers. Use the listed ACLs to dene who can download zones. 364 Expert Configuration SLES 12 SP4FIGURE 26.5: DNS SERVER: ZONE EDITOR (BASICS) Zone Editor (NS Records) The NS Records dialog allows you to dene alternative name servers for the zones specied. Make sure that your own name server is included in the list. To add a record, enter its name under Name Server to Add then conrm with Add. See Figure 26.6, “DNS Server: Zone Editor (NS Records)”. FIGURE 26.6: DNS SERVER: ZONE EDITOR (NS RECORDS) Zone Editor (MX Records) 365 Expert Configuration SLES 12 SP4To add a mail server for the current zone to the existing list, enter the corresponding address and priority value. After doing so, conrm by selecting Add. See Figure 26.7, “DNS Server: Zone Editor (MX Records)”. FIGURE 26.7: DNS SERVER: ZONE EDITOR (MX RECORDS) Zone Editor (SOA) This page allows you to create SOA (start of authority) records. For an explanation of the individual options, refer to Example  26.6, “The /var/lib/named/example.com.zone File”. Changing SOA records is not supported for dynamic zones managed via LDAP. 366 Expert Configuration SLES 12 SP4FIGURE 26.8: DNS SERVER: ZONE EDITOR (SOA) Zone Editor (Records) This dialog manages name resolution. In Record Key, enter the host name then select its type. The A type represents the main entry. The value for this should be an IP address (IPv4). Use AAAA for IPv6 addresses. CNAME is an alias. Use the types NS and MX for detailed or partial records that expand on the information provided in the NS Records and MX Records tabs. These three types resolve to an existing A record. PTR is for reverse zones. It is the opposite of an A record, for example: hostname.example.com. IN A 192.168.0.1 1.0.168.192.in-addr.arpa IN PTR hostname.example.com. 26.3.2.9.1 Adding Reverse Zones To add a reverse zone, follow this procedure: 1. Start YaST DNS Server DNS Zones. 2. If you have not added a master forward zone, add it and Edit it. 3. In the Records tab, ll the corresponding Record Key and Value, then add the record with Add and conrm with OK. If YaST complains about a non-existing record for a name server, add it in the NS Records tab. 367 Expert Configuration SLES 12 SP4FIGURE 26.9: ADDING A RECORD FOR A MASTER ZONE 4. Back in the DNS Zones window, add a reverse master zone. FIGURE 26.10: ADDING A REVERSE ZONE 5. Edit the reverse zone, and in the Records tab, you can see the PTR: Reverse translation record type. Add the corresponding Record Key and Value, then click Add and conrm with OK. 368 Expert Configuration SLES 12 SP4FIGURE 26.11: ADDING A REVERSE RECORD Add a name server record if needed. Tip: Editing the Reverse Zone After adding a forward zone, go back to the main menu and select the reverse zone for editing. There in the tab Basics activate the check box Automatically Generate Records From and select your forward zone. That way, all changes to the forward zone are automatically updated in the reverse zone. 26.4 Starting the BIND Name Server On a SUSE® Linux Enterprise Server system, the name server BIND (Berkeley Internet Name Domain) comes precongured, so it can be started right after installation without any problems. Normally, if you already have an Internet connection and entered 127.0.0.1 as the name server address for localhost in /etc/resolv.conf , you already have a working name resolution without needing to know the DNS of the provider. BIND carries out name resolution via the root name server, a notably slower process. Normally, the DNS of the provider should be entered with its IP address in the conguration le /etc/named.conf under forwarders to ensure 369 Starting the BIND Name Server SLES 12 SP4eective and secure name resolution. If this works so far, the name server runs as a pure caching- only name server. Only when you congure its own zones it becomes a proper DNS. Find a simple example documented in /usr/share/doc/packages/bind/config . Tip: Automatic Adaptation of the Name Server Information Depending on the type of Internet connection or the network connection, the name server information can automatically be adapted to the current conditions. To do this, set the NETCONFIG_DNS_POLICY variable in the /etc/sysconfig/network/config le to auto . However, do not set up an ocial domain until one is assigned to you by the responsible institution. Even if you have your own domain and it is managed by the provider, you are better o not using it, because BIND would otherwise not forward requests for this domain. The Web server at the provider, for example, would not be accessible for this domain. To start the name server, enter the command systemctl start named as root . Check with systemctl status named whether named (as the name server process is called) has been started successfully. Test the name server immediately on the local system with the host or dig programs, which should return localhost as the default server with the address 127.0.0.1 . If this is not the case, /etc/resolv.conf probably contains an incorrect name server entry or the le does not exist. For the rst test, enter host   127.0.0.1 , which should always work. If you get an error message, use systemctl status named to see whether the server is actually running. If the name server does not start or behaves unexpectedly, check the output of journalctl -e . To use the name server of the provider (or one already running on your network) as the forwarder, enter the corresponding IP address or addresses in the options section under forwarders . The addresses included in Example  26.1, “Forwarding Options in named.conf” are examples only. Adjust these entries to your own setup. EXAMPLE 26.1: FORWARDING OPTIONS IN NAMED.CONF options { directory "/var/lib/named"; forwarders { 10.11.12.13; 10.11.12.14; }; listen-on { 127.0.0.1; 192.168.1.116; }; allow-query { 127/8; 192.168/16 }; notify no; }; 370 Starting the BIND Name Server SLES 12 SP4The options entry is followed by entries for the zone, localhost , and 0.0.127.in- addr.arpa . The type hint entry under “.” should always be present. The corresponding les do not need to be modied and should work as they are. Also make sure that each entry is closed with a “;” and that the curly braces are in the correct places. After changing the conguration le /etc/named.conf or the zone les, tell BIND to reread them with systemctl reload named . Achieve the same by stopping and restarting the name server with systemctl restart named . Stop the server at any time by entering systemctl stop named . 26.5 The /etc/named.conf Configuration File All the settings for the BIND name server itself are stored in the /etc/named.conf le. However, the zone data for the domains to handle (consisting of the host names, IP addresses, and so on) are stored in separate les in the /var/lib/named directory. The details of this are described later. /etc/named.conf is roughly divided into two areas. One is the options section for general settings and the other consists of zone entries for the individual domains. A logging section and acl (access control list) entries are optional. Comment lines begin with a # sign or // . A minimal /etc/named.conf is shown in Example 26.2, “A Basic /etc/named.conf”. EXAMPLE 26.2: A BASIC /ETC/NAMED.CONF options { directory "/var/lib/named"; forwarders { 10.0.0.1; }; notify no; }; zone "localhost" in { type master; file "localhost.zone"; }; zone "0.0.127.in-addr.arpa" in { type master; file "127.0.0.zone"; }; zone "." in { type hint; file "root.hint"; }; 371 The /etc/named.conf Configuration File SLES 12 SP426.5.1 Important Configuration Options directory " FILENAME "; Species the directory in which BIND can nd the les containing the zone data. Usually, this is /var/lib/named . forwarders { IP-ADDRESS ; }; Species the name servers (mostly of the provider) to which DNS requests should be forwarded if they cannot be resolved directly. Replace IP-ADDRESS with an IP address like 192.168.1.116 . forward first; Causes DNS requests to be forwarded before an attempt is made to resolve them via the root name servers. Instead of forward first , forward only can be written to have all requests forwarded and none sent to the root name servers. This makes sense for rewall congurations. listen-on port 53 { 127.0.0.1; IP-ADDRESS ; }; Tells BIND on which network interfaces and port to accept client queries. port 53 does not need to be specied explicitly, because 53 is the default port. Enter 127.0.0.1 to permit requests from the local host. If you omit this entry entirely, all interfaces are used by default. listen-on-v6 port 53 {any; }; Tells BIND on which port it should listen for IPv6 client requests. The only alternative to any is none . As far as IPv6 is concerned, the server only accepts wild card addresses. query-source address * port 53; This entry is necessary if a rewall is blocking outgoing DNS requests. This tells BIND to post requests externally from port 53 and not from any of the high ports above 1024. query-source-v6 address * port 53; Tells BIND which port to use for IPv6 queries. allow-query { 127.0.0.1; NET ; }; Denes the networks from which clients can post DNS requests. Replace NET with address information like 192.168.2.0/24 . The /24 at the end is an abbreviated expression for the netmask (in this case 255.255.255.0 ). allow-transfer ! *;; 372 Important Configuration Options SLES 12 SP4Controls which hosts can request zone transfers. In the example, such requests are completely denied with ! * . Without this entry, zone transfers can be requested from anywhere without restrictions. statistics-interval 0; In the absence of this entry, BIND generates several lines of statistical information per hour in the system''s journal. Set it to 0 to suppress these statistics completely or set an interval in minutes. cleaning-interval 720; This option denes at which time intervals BIND clears its cache. This triggers an entry in the system''s journal each time it occurs. The time specication is in minutes. The default is 60 minutes. interface-interval 0; BIND regularly searches the network interfaces for new or nonexistent interfaces. If this value is set to 0 , this is not done and BIND only listens at the interfaces detected at start- up. Otherwise, the interval can be dened in minutes. The default is sixty minutes. notify no; no prevents other name servers from being informed when changes are made to the zone data or when the name server is restarted. For a list of available options, read the manual page man 5 named.conf . 26.5.2 Logging What, how, and where logging takes place can be extensively congured in BIND. Normally, the default settings should be sucient. Example 26.3, “Entry to Disable Logging”, shows the simplest form of such an entry and completely suppresses any logging. EXAMPLE 26.3: ENTRY TO DISABLE LOGGING logging { category default { null; }; }; 373 Logging SLES 12 SP426.5.3 Zone Entries EXAMPLE 26.4: ZONE ENTRY FOR EXAMPLE.COM zone "example.com" in { type master; file "example.com.zone"; notify no; }; After zone , specify the name of the domain to administer ( example.com ) followed by in and a block of relevant options enclosed in curly braces, as shown in Example 26.4, “Zone Entry for example.com”. To dene a slave zone, switch the type to slave and specify a name server that administers this zone as master (which, in turn, may be a slave of another master), as shown in Example 26.5, “Zone Entry for example.net”. EXAMPLE 26.5: ZONE ENTRY FOR EXAMPLE.NET zone "example.net" in { type slave; file "slave/example.net.zone"; masters { 10.0.0.1; }; }; The zone options: type master; By specifying master , tell BIND that the zone is handled by the local name server. This assumes that a zone le has been created in the correct format. type slave; This zone is transferred from another name server. It must be used together with masters . type hint; The zone . of the hint type is used to set the root name servers. This zone denition can be left as is. file example.com.zone or file “slave/example.net.zone”; This entry species the le where zone data for the domain is located. This le is not required for a slave, because this data is pulled from another name server. To dierentiate master and slave les, use the directory slave for the slave les. masters { SERVER_IP_ADDRESS ; }; 374 Zone Entries SLES 12 SP4This entry is only needed for slave zones. It species from which name server the zone le should be transferred. allow-update {! *; }; This option controls external write access, which would allow clients to make a DNS entry —something not normally desirable for security reasons. Without this entry, zone updates are not allowed. The above entry achieves the same because ! * eectively bans any such activity. 26.6 Zone Files Two types of zone les are needed. One assigns IP addresses to host names and the other does the reverse: it supplies a host name for an IP address. Tip: Using the Dot (Period, Fullstop) in Zone Files The "." has an important meaning in the zone les. If host names are given without a nal dot ( . ), the zone is appended. Complete host names specied with a full domain name must end with a dot ( . ) to avoid having the domain added to it again. A missing or wrongly placed "." is probably the most frequent cause of name server conguration errors. The rst case to consider is the zone le example.com.zone , responsible for the domain example.com , shown in Example 26.6, “The /var/lib/named/example.com.zone File”. EXAMPLE 26.6: THE /VAR/LIB/NAMED/EXAMPLE.COM.ZONE FILE 1. $TTL 2D 2. example.com. IN SOA dns root.example.com. ( 3. 2003072441 ; serial 4. 1D ; refresh 5. 2H ; retry 6. 1W ; expiry 7. 2D ) ; minimum 8. 9. IN NS dns 10. IN MX 10 mail 11. 12. gate IN A 192.168.5.1 13. IN A 10.0.0.1 14. dns IN A 192.168.1.116 375 Zone Files SLES 12 SP415. mail IN A 192.168.3.108 16. jupiter IN A 192.168.2.100 17. venus IN A 192.168.2.101 18. saturn IN A 192.168.2.102 19. mercury IN A 192.168.2.103 20. ntp IN CNAME dns 21. dns6 IN A6 0 2002:c0a8:174:: Line 1: $TTL denes the default time to live that should apply to all the entries in this le. In this example, entries are valid for a period of two days ( 2 D ). Line 2: This is where the SOA (start of authority) control record begins: The name of the domain to administer is example.com in the rst position. This ends with "." , because otherwise the zone would be appended a second time. Alternatively, @ can be entered here, in which case the zone would be extracted from the corresponding entry in /etc/named.conf . After IN SOA is the name of the name server in charge as master for this zone. The name is expanded from dns to dns.example.com , because it does not end with a "." . An e-mail address of the person in charge of this name server follows. Because the @ sign already has a special meaning, "." is entered here instead. For root@example.com the entry must read root.example.com. . The "." must be included at the end to prevent the zone from being added. The ( includes all lines up to ) into the SOA record. Line 3: The serial number is an arbitrary number that is increased each time this le is changed. It is needed to inform the secondary name servers (slave servers) of changes. For this, a 10 digit number of the date and run number, written as YYYYMMDDNN, has become the customary format. Line 4: The refresh rate species the time interval at which the secondary name servers verify the zone serial number . In this case, one day. Line 5: 376 Zone Files SLES 12 SP4The retry rate species the time interval at which a secondary name server, in case of error, attempts to contact the primary server again. Here, two hours. Line 6: The expiration time species the time frame after which a secondary name server discards the cached data if it has not regained contact to the primary server. Here, a week. Line 7: The last entry in the SOA record species the negative caching TTL—the time for which results of unresolved DNS queries from other servers may be cached. Line 9: The IN NS species the name server responsible for this domain. dns is extended to dns.example.com because it does not end with a "." . There can be several lines like this—one for the primary and one for each secondary name server. If notify is not set to no in /etc/named.conf , all the name servers listed here are informed of the changes made to the zone data. Line 10: The MX record species the mail server that accepts, processes, and forwards e-mails for the domain example.com . In this example, this is the host mail.example.com . The number in front of the host name is the preference value. If there are multiple MX entries, the mail server with the smallest value is taken rst. If mail delivery to this server fails, the next entry with higher value is used. Lines 12–19: These are the actual address records where one or more IP addresses are assigned to host names. The names are listed here without a "." because they do not include their domain, so example.com is added to all of them. Two IP addresses are assigned to the host gate , as it has two network cards. Wherever the host address is a traditional one (IPv4), the record is marked with A . If the address is an IPv6 address, the entry is marked with AAAA . Note: IPv6 Syntax The IPv6 record has a slightly dierent syntax than IPv4. Because of the fragmentation possibility, it is necessary to provide information about missed bits before the address. To ll up the IPv6 address with the needed number of “0”, add two colons at the correct place in the address. pluto AAAA 2345:00C1:CA11::1234:5678:9ABC:DEF0 377 Zone Files SLES 12 SP4pluto AAAA 2345:00D2:DA11::1234:5678:9ABC:DEF0 Line 20: The alias ntp can be used to address dns ( CNAME means canonical name). The pseudo domain in-addr.arpa is used for the reverse lookup of IP addresses into host names. It is appended to the network part of the address in reverse notation. So 192.168 is resolved into 168.192.in-addr.arpa . See Example 26.7, “Reverse Lookup”. EXAMPLE 26.7: REVERSE LOOKUP 1. $TTL 2D 2. 168.192.in-addr.arpa. IN SOA dns.example.com. root.example.com. ( 3. 2003072441 ; serial 4. 1D ; refresh 5. 2H ; retry 6. 1W ; expiry 7. 2D ) ; minimum 8. 9. IN NS dns.example.com. 10. 11. 1.5 IN PTR gate.example.com. 12. 100.3 IN PTR www.example.com. 13. 253.2 IN PTR cups.example.com. Line 1: $TTL denes the standard TTL that applies to all entries here. Line 2: The conguration le should activate reverse lookup for the network 192.168 . Given that the zone is called 168.192.in-addr.arpa , it should not be added to the host names. Therefore, all host names are entered in their complete form—with their domain and with a "." at the end. The remaining entries correspond to those described for the previous example.com example. Lines 3–7: See the previous example for example.com . Line 9: Again this line species the name server responsible for this zone. This time, however, the name is entered in its complete form with the domain and a "." at the end. 378 Zone Files SLES 12 SP4Lines 11–13: These are the pointer records hinting at the IP addresses on the respective hosts. Only the last part of the IP address is entered at the beginning of the line, without the "." at the end. Appending the zone to this (without the .in-addr.arpa ) results in the complete IP address in reverse order. Normally, zone transfers between dierent versions of BIND should be possible without any problems. 26.7 Dynamic Update of Zone Data The term dynamic update refers to operations by which entries in the zone les of a master server are added, changed, or deleted. This mechanism is described in RFC 2136. Dynamic update is congured individually for each zone entry by adding an optional allow-update or update- policy rule. Zones to update dynamically should not be edited by hand. Transmit the entries to update to the server with the command nsupdate . For the exact syntax of this command, check the manual page for nsupdate ( man  8 nsupdate ). For security reasons, any such update should be performed using TSIG keys as described in Section  26.8, “Secure Transactions”. 26.8 Secure Transactions Secure transactions can be made with transaction signatures (TSIGs) based on shared secret keys (also called TSIG keys). This section describes how to generate and use such keys. Secure transactions are needed for communication between dierent servers and for the dynamic update of zone data. Making the access control dependent on keys is much more secure than merely relying on IP addresses. Generate a TSIG key with the following command (for details, see man   dnssec-keygen ): dnssec-keygen -a hmac-md5 -b 128 -n HOST host1-host2 This creates two les with names similar to these: Khost1-host2.+157+34265.private Khost1-host2.+157+34265.key 379 Dynamic Update of Zone Data SLES 12 SP4The key itself (a string like ejIkuCyyGJwwuN3xAteKgg== ) is found in both les. To use it for transactions, the second le ( Khost1-host2.+157+34265.key ) must be transferred to the remote host, preferably in a secure way (using scp, for example). On the remote server, the key must be included in the /etc/named.conf le to enable a secure communication between host1 and host2 : key host1-host2 { algorithm hmac-md5; secret "ejIkuCyyGJwwuN3xAteKgg=="; }; Warning: File Permissions of /etc/named.conf Make sure that the permissions of /etc/named.conf are properly restricted. The default for this le is 0640 , with the owner being root and the group named . As an alternative, move the keys to an extra le with specially limited permissions, which is then included from /etc/named.conf . To include an external le, use: include "filename" Replace filename with an absolute path to your le with keys. To enable the server host1 to use the key for host2 (which has the address 10.1.2.3 in this example), the server''s /etc/named.conf must include the following rule: server 10.1.2.3 { keys { host1-host2. ;}; }; Analogous entries must be included in the conguration les of host2 . Add TSIG keys for any ACLs (access control lists, not to be confused with le system ACLs) that are dened for IP addresses and address ranges to enable transaction security. The corresponding entry could look like this: allow-update { key host1-host2. ;}; This topic is discussed in more detail in the BIND Administrator Reference Manual under update- policy . 380 Secure Transactions SLES 12 SP426.9 DNS Security DNSSEC, or DNS security, is described in RFC 2535. The tools available for DNSSEC are discussed in the BIND Manual. A zone considered secure must have one or several zone keys associated with it. These are generated with dnssec-keygen , as are the host keys. The DSA encryption algorithm is currently used to generate these keys. The public keys generated should be included in the corresponding zone le with an $INCLUDE rule. With the command dnssec-signzone , you can create sets of generated keys ( keyset- les), transfer them to the parent zone in a secure manner, and sign them. This generates the les to include for each zone in /etc/named.conf . 26.10 For More Information For more information, see the BIND Administrator Reference Manual from the bind- doc package, which is installed under /usr/share/doc/packages/bind/arm . Consider additionally consulting the RFCs referenced by the manual and the manual pages included with BIND. /usr/share/doc/packages/bind/README.SUSE contains up-to-date information about BIND in SUSE Linux Enterprise Server. 381 DNS Security SLES 12 SP427 DHCP The purpose of the Dynamic Host Conguration Protocol (DHCP) is to assign network settings centrally (from a server) rather than conguring them locally on every workstation. A host congured to use DHCP does not have control over its own static address. It is enabled to congure itself completely and automatically according to directions from the server. If you use the NetworkManager on the client side, you do not need to congure the client. This is useful if you have changing environments and only one interface active at a time. Never use NetworkManager on a machine that runs a DHCP server. Tip: IBM z Systems: DHCP Support On IBM z Systems platforms, DHCP only works on interfaces using the OSA and OSA Express network cards. These cards are the only ones with a MAC, which is required for the DHCP autoconguration features. One way to congure a DHCP server is to identify each client using the hardware address of its network card (which should be xed in most cases), then supply that client with identical settings each time it connects to the server. DHCP can also be congured to assign addresses to each relevant client dynamically from an address pool set up for this purpose. In the latter case, the DHCP server tries to assign the same address to the client each time it receives a request, even over extended periods. This works only if the network does not have more clients than addresses. DHCP makes life easier for system administrators. Any changes, even bigger ones, related to addresses and the network conguration in general can be implemented centrally by editing the server''s conguration le. This is much more convenient than reconguring numerous workstations. It is also much easier to integrate machines, particularly new machines, into the network, because they can be given an IP address from the pool. Retrieving the appropriate network settings from a DHCP server is especially useful in case of laptops regularly used in dierent networks. In this chapter, the DHCP server will run in the same subnet as the workstations, 192.168.2.0/24 with 192.168.2.1 as gateway. It has the xed IP address 192.168.2.254 and serves two address ranges, 192.168.2.10 to 192.168.2.20 and 192.168.2.100 to 192.168.2.200 . 382 SLES 12 SP4A DHCP server supplies not only the IP address and the netmask, but also the host name, domain name, gateway, and name server addresses for the client to use. In addition to that, DHCP allows several other parameters to be congured in a centralized way, for example, a time server from which clients may poll the current time or even a print server. 27.1 Configuring a DHCP Server with YaST To install a DHCP server, start YaST and select Software Software Management. Choose Filter Patterns and select DHCP and DNS Server. Conrm the installation of the dependent packages to nish the installation process. Important: LDAP Support The YaST DHCP module can be set up to store the server conguration locally (on the host that runs the DHCP server) or to have its conguration data managed by an LDAP server. To use LDAP, set up your LDAP environment before conguring the DHCP server. For more information about LDAP, see Book “Security Guide”, Chapter 5 “LDAP—A Directory Service”. The YaST DHCP module ( yast2-dhcp-server ) allows you to set up your own DHCP server for the local network. The module can run in wizard mode or expert conguration mode. 27.1.1 Initial Configuration (Wizard) When the module is started for the rst time, a wizard starts, prompting you to make a few basic decisions concerning server administration. Completing this initial setup produces a very basic server conguration that should function in its essential aspects. The expert mode can be used to deal with more advanced conguration tasks. Proceed as follows: 1. Select the interface from the list to which the DHCP server should listen and click Select. After this, select Open Firewall for Selected Interfaces to open the rewall for this interface, and click Next. See Figure 27.1, “DHCP Server: Card Selection”. 383 Configuring a DHCP Server with YaST SLES 12 SP4FIGURE 27.1: DHCP SERVER: CARD SELECTION 2. Use the check box to determine whether your DHCP settings should be automatically stored by an LDAP server. In the text boxes, provide the network specics for all clients the DHCP server should manage. These specics are the domain name, address of a time server, addresses of the primary and secondary name server, addresses of a print and a WINS server (for a mixed network with both Windows and Linux clients), gateway address, and lease time. See Figure 27.2, “DHCP Server: Global Settings”. 384 Initial Configuration (Wizard) SLES 12 SP4FIGURE 27.2: DHCP SERVER: GLOBAL SETTINGS 3. Congure how dynamic IP addresses should be assigned to clients. To do so, specify an IP range from which the server can assign addresses to DHCP clients. All these addresses must be covered by the same netmask. Also specify the lease time during which a client may keep its IP address without needing to request an extension of the lease. Optionally, specify the maximum lease time—the period during which the server reserves an IP address for a particular client. See Figure 27.3, “DHCP Server: Dynamic DHCP”. 385 Initial Configuration (Wizard) SLES 12 SP4FIGURE 27.3: DHCP SERVER: DYNAMIC DHCP 4. Dene how the DHCP server should be started. Specify whether to start the DHCP server automatically when the system is booted or manually when needed (for example, for testing purposes). Click Finish to complete the conguration of the server. See Figure 27.4, “DHCP Server: Start-Up”. 386 Initial Configuration (Wizard) SLES 12 SP4FIGURE 27.4: DHCP SERVER: START-UP 5. Instead of using dynamic DHCP in the way described in the preceding steps, you can also congure the server to assign addresses in quasi-static fashion. Use the text boxes provided in the lower part to specify a list of the clients to manage in this way. Specically, provide the Name and the IP Address to give to such a client, the Hardware Address, and the Network Type (token ring or Ethernet). Modify the list of clients, which is shown in the upper part with Add, Edit, and Delete from List. See Figure 27.5, “DHCP Server: Host Management”. 387 Initial Configuration (Wizard) SLES 12 SP4FIGURE 27.5: DHCP SERVER: HOST MANAGEMENT 27.1.2 DHCP Server Configuration (Expert) In addition to the conguration method discussed earlier, there is also an expert conguration mode that allows you to change the DHCP server setup in every detail. Start the expert conguration by clicking DHCP Server Expert Conguration in the Start-Up dialog (see Figure 27.4, “DHCP Server: Start-Up”). Chroot Environment and Declarations In this rst dialog, make the existing conguration editable by selecting Start DHCP Server. An important feature of the behavior of the DHCP server is its ability to run in a chroot environment, or chroot jail, to secure the server host. If the DHCP server should ever be compromised by an outside attack, the attacker will still be in the chroot jail, which prevents him from accessing the rest of the system. The lower part of the dialog displays a tree view with the declarations that have already been dened. Modify these with Add, Delete, and Edit. Selecting Advanced takes you to additional expert dialogs. See Figure 27.6, “DHCP Server: Chroot Jail and Declarations”. After selecting Add, dene the type of declaration to add. With Advanced, view the log le of the server, congure TSIG key management, and adjust the conguration of the rewall according to the setup of the DHCP server. 388 DHCP Server Configuration (Expert) SLES 12 SP4FIGURE 27.6: DHCP SERVER: CHROOT JAIL AND DECLARATIONS Selecting the Declaration Type The Global Options of the DHCP server are made up of several declarations. This dialog lets you set the declaration types Subnet, Host, Shared Network, Group, Pool of Addresses, and Class. This example shows the selection of a new subnet (see Figure 27.7, “DHCP Server: Selecting a Declaration Type”). 389 DHCP Server Configuration (Expert) SLES 12 SP4FIGURE 27.7: DHCP SERVER: SELECTING A DECLARATION TYPE Subnet Configuration This dialog allows you specify a new subnet with its IP address and netmask. In the middle part of the dialog, modify the DHCP server start options for the selected subnet using Add, Edit, and Delete. To set up dynamic DNS for the subnet, select Dynamic DNS. FIGURE 27.8: DHCP SERVER: CONFIGURING SUBNETS 390 DHCP Server Configuration (Expert) SLES 12 SP4TSIG Key Management If you chose to congure dynamic DNS in the previous dialog, you can now congure the key management for a secure zone transfer. Selecting OK takes you to another dialog in which to congure the interface for dynamic DNS (see Figure 27.10, “DHCP Server: Interface Configuration for Dynamic DNS”). FIGURE 27.9: DHCP SERVER: TSIG CONFIGURATION Dynamic DNS: Interface Configuration You can now activate dynamic DNS for the subnet by selecting Enable Dynamic DNS for This Subnet. After doing so, use the drop-down box to activate the TSIG keys for forward and reverse zones, making sure that the keys are the same for the DNS and the DHCP server. With Update Global Dynamic DNS Settings, enable the automatic update and adjustment of the global DHCP server settings according to the dynamic DNS environment. Finally, dene which forward and reverse zones should be updated per dynamic DNS, specifying the name of the primary name server for each of the two zones. Selecting OK returns to the subnet conguration dialog (see Figure 27.8, “DHCP Server: Configuring Subnets”). Selecting OK again returns to the original expert conguration dialog. 391 DHCP Server Configuration (Expert) SLES 12 SP4FIGURE 27.10: DHCP SERVER: INTERFACE CONFIGURATION FOR DYNAMIC DNS Network Interface Configuration To dene the interfaces the DHCP server should listen to and to adjust the rewall conguration, select Advanced Interface Conguration from the expert conguration dialog. From the list of interfaces displayed, select one or more that should be attended by the DHCP server. If clients in all subnets need to be able to communicate with the server and the server host also runs a rewall, adjust the rewall accordingly. To do so, select Adapt Firewall Settings. YaST then adjusts the rules of SuSEFirewall2 to the new conditions (see Figure 27.11, “DHCP Server: Network Interface and Firewall”), after which you can return to the original dialog by selecting OK. 392 DHCP Server Configuration (Expert) SLES 12 SP4FIGURE 27.11: DHCP SERVER: NETWORK INTERFACE AND FIREWALL After completing all conguration steps, close the dialog with OK. The server is now started with its new conguration. 27.2 DHCP Software Packages Both the DHCP server and the DHCP clients are available for SUSE Linux Enterprise Server. The DHCP server available is dhcpd (published by the Internet Systems Consortium). On the client side, there is dhcp-client (also from ISC) and tools coming with the wicked package. 393 DHCP Software Packages SLES 12 SP4By default, the wicked tools are installed with the services wickedd-dhcp4 and wickedd- dhcp6 . Both are launched automatically on each system boot to watch for a DHCP server. They do not need a conguration le to do their job and work out of the box in most standard setups. For more complex situations, use the ISC dhcp-client , which is controlled by means of the conguration les /etc/dhclient.conf and /etc/dhclient6.conf . 27.3 The DHCP Server dhcpd The core of any DHCP system is the dynamic host conguration protocol daemon. This server leases addresses and watches how they are used, according to the settings dened in the conguration le /etc/dhcpd.conf . By changing the parameters and values in this le, a system administrator can inuence the program''s behavior in numerous ways. Look at the basic sample /etc/dhcpd.conf le in Example 27.1, “The Configuration File /etc/dhcpd.conf”. EXAMPLE 27.1: THE CONFIGURATION FILE /ETC/DHCPD.CONF default-lease-time 600; # 10 minutes max-lease-time 7200; # 2 hours option domain-name "example.com"; option domain-name-servers 192.168.1.116; option broadcast-address 192.168.2.255; option routers 192.168.2.1; option subnet-mask 255.255.255.0; subnet 192.168.2.0 netmask 255.255.255.0 { range 192.168.2.10 192.168.2.20; range 192.168.2.100 192.168.2.200; } This simple conguration le should be sucient to get the DHCP server to assign IP addresses in the network. Make sure that a semicolon is inserted at the end of each line, because otherwise dhcpd is not started. The sample le can be divided into three sections. The rst one denes how many seconds an IP address is leased to a requesting client by default ( default-lease-time ) before it should apply for renewal. This section also includes a statement of the maximum period for which a machine may keep an IP address assigned by the DHCP server without applying for renewal ( max-lease-time ). 394 The DHCP Server dhcpd SLES 12 SP4In the second part, some basic network parameters are dened on a global level: The line option domain-name denes the default domain of your network. With the entry option domain-name-servers , specify up to three values for the DNS servers used to resolve IP addresses into host names and vice versa. Ideally, congure a name server on your machine or somewhere else in your network before setting up DHCP. That name server should also dene a host name for each dynamic address and vice versa. To learn how to congure your own name server, read Chapter 26, The Domain Name System. The line option broadcast-address denes the broadcast address the requesting client should use. With option routers , set where the server should send data packets that cannot be delivered to a host on the local network (according to the source and target host address and the subnet mask provided). Usually, especially in smaller networks, this router is identical to the Internet gateway. With option subnet-mask , specify the netmask assigned to clients. The last section of the le denes a network, including a subnet mask. To nish, specify the address range that the DHCP daemon should use to assign IP addresses to interested clients. In Example 27.1, “The Configuration File /etc/dhcpd.conf”, clients may be given any address between 192.168.2.10 and 192.168.2.20 or 192.168.2.100 and 192.168.2.200 . After editing these few lines, you should be able to activate the DHCP daemon with the command systemctl start dhcpd . It will be ready for use immediately. Use the command rcdhcpd   check-syntax to perform a brief syntax check. If you encounter any unexpected problems with your conguration (the server aborts with an error or does not return done on start), you should be able to nd out what has gone wrong by looking for information either in the main system log that can be queried with the command journalctl (see Chapter 15, journalctl: Query the systemd Journal for more information). 395 The DHCP Server dhcpd SLES 12 SP4On a default SUSE Linux Enterprise Server system, the DHCP daemon is started in a chroot environment for security reasons. The conguration les must be copied to the chroot environment so the daemon can nd them. Normally, there is no need to worry about this because the command systemctl start dhcpd automatically copies the les. 27.3.1 Clients with Fixed IP Addresses DHCP can also be used to assign a predened, static address to a specic client. Addresses assigned explicitly always take priority over dynamic addresses from the pool. A static address never expires in the way a dynamic address would, for example, if there were not enough addresses available and the server needed to redistribute them among clients. To identify a client congured with a static address, dhcpd uses the hardware address (which is a globally unique, xed numerical code consisting of six octet pairs) for the identication of all network devices (for example, 00:30:6E:08:EC:80 ). If the respective lines, like the ones in Example 27.2, “Additions to the Configuration File”, are added to the conguration le of Example 27.1, “The Configuration File /etc/dhcpd.conf”, the DHCP daemon always assigns the same set of data to the corresponding client. EXAMPLE 27.2: ADDITIONS TO THE CONFIGURATION FILE host jupiter { hardware ethernet 00:30:6E:08:EC:80; fixed-address 192.168.2.100; } The name of the respective client ( host HOSTNAME , here jupiter ) is entered in the rst line and the MAC address in the second line. On Linux hosts, nd the MAC address with the command ip link show followed by the network device (for example, eth0 ). The output should contain something like link/ether 00:30:6E:08:EC:80 In the preceding example, a client with a network card having the MAC address 00:30:6E:08:EC:80 is assigned the IP address 192.168.2.100 and the host name jupiter automatically. The type of hardware to enter is ethernet in nearly all cases, although token- ring , which is often found on IBM systems, is also supported. 396 Clients with Fixed IP Addresses SLES 12 SP427.3.2 The SUSE Linux Enterprise Server Version To improve security, the SUSE Linux Enterprise Server version of the ISC''s DHCP server comes with the non-root/chroot patch by Ari Edelkind applied. This enables dhcpd to run with the user ID nobody and run in a chroot environment ( /var/lib/dhcp ). To make this possible, the conguration le dhcpd.conf must be located in /var/lib/dhcp/etc . The init script automatically copies the le to this directory when starting. Control the server''s behavior regarding this feature by means of entries in the le / etc/sysconfig/dhcpd . To run dhcpd without the chroot environment, set the variable DHCPD_RUN_CHROOTED in /etc/sysconfig/dhcpd to “no”. To enable dhcpd to resolve host names even from within the chroot environment, some other conguration les must be copied as well: /etc/localtime /etc/host.conf /etc/hosts /etc/resolv.conf These les are copied to /var/lib/dhcp/etc/ when starting the init script. Take these copies into account for any changes that they require if they are dynamically modied by scripts like /etc/ppp/ip-up . However, there should be no need to worry about this if the conguration le only species IP addresses (instead of host names). If your conguration includes additional les that should be copied into the chroot environment, set these under the variable DHCPD_CONF_INCLUDE_FILES in the le /etc/sysconfig/dhcpd . To ensure that the DHCP logging facility keeps working even after a restart of the syslog daemon, there is an additional entry SYSLOGD_ADDITIONAL_SOCKET_DHCP in the le /etc/sysconfig/ syslog . 27.4 For More Information More information about DHCP is available at the Web site of the Internet Systems Consortium (https://www.isc.org/dhcp/ ). Information is also available in the dhcpd , dhcpd.conf , dhcpd.leases , and dhcp-options man pages. 397 The SUSE Linux Enterprise Server Version SLES 12 SP428 Sharing File Systems with NFS The Network File System (NFS) is a protocol that allows access to les on a server very similar to accessing local les. 28.1 Overview The Network File System (NFS) is a standardized, well-proven and widely supported network protocol that allows les to be shared between separate hosts. The Network Information Service (NIS) can be used to have a centralized user management in the network. Combining NFS and NIS allows using le and directory permissions for access control in the network. NFS with NIS makes a network transparent to the user. In the default conguration, NFS completely trusts the network and thus any machine that is connected to a trusted network. Any user with administrator privileges on any computer with physical access to any network the NFS server trusts can access any les that the server makes available. In many cases, this level of security is perfectly satisfactory, such as when the network that is trusted is truly private, often localized to a single cabinet or machine room, and no unauthorized access is possible. In other cases the need to trust a whole subnet as a unit is restrictive and there is a need for more ne-grained trust. To meet the need in these cases, NFS supports various security levels using the Kerberos infrastructure. Kerberos requires NFSv4, which is used by default. For details, see Book “Security Guide”, Chapter 6 “Network Authentication with Kerberos”. The following are terms used in the YaST module. Exports A directory exported by an NFS server, which clients can integrate it into their system. NFS Client The NFS client is a system that uses NFS services from an NFS server over the Network File System protocol. The TCP/IP protocol is already integrated into the Linux kernel; there is no need to install any additional software. NFS Server The NFS server provides NFS services to clients. A running server depends on the following daemons: nfsd (worker), idmapd (ID-to-name mapping for NFSv4, needed for certain scenarios only), statd (le locking), and mountd (mount requests). 398 Overview SLES 12 SP4NFSv3 NFSv3 is the version  3 implementation, the “old” stateless NFS that supports client authentication. NFSv4 NFSv4 is the new version 4 implementation that supports secure user authentication via kerberos. NFSv4 requires one single port only and thus is better suited for environments behind a rewall than NFSv3. The protocol is specied as https://datatracker.ietf.org/doc/html/rfc3530 . pNFS Parallel NFS, a protocol extension of NFSv4. Any pNFS clients can directly access the data on an NFS server. Important: Need for DNS In principle, all exports can be made using IP addresses only. To avoid time-outs, you need a working DNS system. DNS is necessary at least for logging purposes, because the mountd daemon does reverse lookups. 28.2 Installing NFS Server The NFS server is not part of the default installation. To install the NFS server using YaST, choose Software Software Management, select Patterns, and enable the File Server option in the Server Functions section. Press Accept to install the required packages. Like NIS, NFS is a client/server system. However, a machine can be both—it can supply le systems over the network (export) and mount le systems from other hosts (import). Note: Mounting NFS Volumes Locally on the Exporting Server Mounting NFS volumes locally on the exporting server is not supported on SUSE Linux Enterprise Server. 399 Installing NFS Server SLES 12 SP428.3 Configuring NFS Server Conguring an NFS server can be done either through YaST or manually. For authentication, NFS can also be combined with Kerberos. 28.3.1 Exporting File Systems with YaST With YaST, turn a host in your network into an NFS server—a server that exports directories and les to all hosts granted access to it or to all members of a group. Thus, the server can also provide applications without installing the applications locally on every host. To set up such a server, proceed as follows: PROCEDURE 28.1: SETTING UP AN NFS SERVER 1. Start YaST and select Network Services NFS Server; see Figure 28.1, “NFS Server Configuration Tool”. You may be prompted to install additional software. FIGURE 28.1: NFS SERVER CONFIGURATION TOOL 2. Activate the Start radio button. 3. If a rewall is active on your system (SuSEFirewall2), check Open Ports in Firewall. YaST adapts its conguration for the NFS server by enabling the nfs service. 400 Configuring NFS Server SLES 12 SP44. Check whether you want to Enable NFSv4. If you deactivate NFSv4, YaST will only support NFSv3. For information about enabling NFSv2, see Note: NFSv2. If NFSv4 is selected, additionally enter the appropriate NFSv4 domain name. This parameter is used by the idmapd daemon that is required for Kerberos setups or if clients cannot work with numeric user names. Leave it as localdomain (the default) if you do not run idmapd or do not have any special requirements. For more information on the idmapd daemon see /etc/idmapd.conf . 5. Click Enable GSS Security if you need secure access to the server. A prerequisite for this is to have Kerberos installed on your domain and to have both the server and the clients kerberized. Click Next to proceed with the next conguration dialog. 6. Click Add Directory in the upper half of the dialog to export your directory. 7. If you have not congured the allowed hosts already, another dialog for entering the client information and options pops up automatically. Enter the host wild card (usually you can leave the default settings as they are). There are four possible types of host wild cards that can be set for each host: a single host (name or IP address), netgroups, wild cards (such as * indicating all machines can access the server), and IP networks. For more information about these options, see the exports man page. 8. Click Finish to complete the conguration. 28.3.2 Exporting File Systems Manually The conguration les for the NFS export service are /etc/exports and /etc/sysconfig/ nfs . In addition to these les, /etc/idmapd.conf is needed for the NFSv4 server conguration with kerberized NFS or if the clients cannot work with numeric user names. To start or restart the services, run the command systemctl restart nfsserver . This also restarts the RPC portmapper that is required by the NFS server. To make sure the NFS server always starts at boot time, run sudo systemctl enable nfsserver . Note: NFSv4 NFSv4 is the latest version of NFS protocol available on SUSE Linux Enterprise Server. Conguring directories for export with NFSv4 is now the same as with NFSv3. 401 Exporting File Systems Manually SLES 12 SP4On SUSE Linux Enterprise Server 11, the bind mount in /etc/exports was mandatory. It is still supported, but now deprecated. /etc/exports The /etc/exports le contains a list of entries. Each entry indicates a directory that is shared and how it is shared. A typical entry in /etc/exports consists of: /SHARED/DIRECTORY HOST(OPTION_LIST) For example: /export/data 192.168.1.2(rw,sync) Here the IP address 192.168.1.2 is used to identify the allowed client. You can also use the name of the host, a wild card indicating a set of hosts ( *.abc.com , * , etc.), or netgroups ( @my-hosts ). For a detailed explanation of all options and their meaning, refer to the man page of exports ( man exports ). In case you have modied /etc/exports while the NFS server was running, you need to restart it for the changes to become active: sudo systemctl restart nfsserver . /etc/sysconfig/nfs The /etc/sysconfig/nfs le contains a few parameters that determine NFSv4 server daemon behavior. It is important to set the parameter NFS4_SUPPORT to yes (default). NFS4_SUPPORT determines whether the NFS server supports NFSv4 exports and clients. In case you have modied /etc/sysconfig/nfs while the NFS server was running, you need to restart it for the changes to become active: sudo systemctl restart nfsserver . Tip: Mount Options On SUSE Linux Enterprise Server 11, the --bind mount in /etc/exports was mandatory. It is still supported, but now deprecated. Conguring directories for export with NFSv4 is now the same as with NFSv3. Note: NFSv2 If NFS clients still depend on NFSv2, enable it on the server in /etc/sysconfig/ nfs by setting: NFSD_OPTIONS="-V2" 402 Exporting File Systems Manually SLES 12 SP4MOUNTD_OPTIONS="-V2" After restarting the service, check whether version 2 is available with the command: tux > cat /proc/fs/nfsd/versions +2 +3 +4 +4.1 -4.2 /etc/idmapd.conf Starting with SLE 12 SP1, the idmapd daemon is only required if Kerberos authentication is used, or if clients cannot work with numeric user names. Linux clients can work with numeric user names since Linux kernel 2.6.39. The idmapd daemon does the name-to-ID mapping for NFSv4 requests to the server and replies to the client. If required, idmapd needs to run on the NFSv4 server. Name-to-ID mapping on the client will be done by nfsidmap provided by the package nfs-client . Make sure that there is a uniform way in which user names and IDs (UIDs) are assigned to users across machines that might probably be sharing le systems using NFS. This can be achieved by using NIS, LDAP, or any uniform domain authentication mechanism in your domain. The parameter Domain must be set the same for both, client and server in the /etc/ idmapd.conf le. If you are not sure, leave the domain as localdomain in the server and client les. A sample conguration le looks like the following: [General] Verbosity = 0 Pipefs-Directory = /var/lib/nfs/rpc_pipefs Domain = localdomain [Mapping] Nobody-User = nobody Nobody-Group = nobody To start the idmapd daemon, run systemctl start nfs-idmapd . In case you have modied /etc/idmapd.conf while the daemon was running, you need to restart it for the changes to become active: systemctl start nfs-idmapd . For more information, see the man pages of idmapd and idmapd.conf ( man idmapd and man idmapd.conf ). 403 Exporting File Systems Manually SLES 12 SP428.3.3 NFS with Kerberos To use Kerberos authentication for NFS, Generic Security Services (GSS) must be enabled. Select Enable GSS Security in the initial YaST NFS Server dialog. You must have a working Kerberos server to use this feature. YaST does not set up the server but only uses the provided functionality. If you want to use Kerberos authentication in addition to the YaST conguration, complete at least the following steps before running the NFS conguration: 1. Make sure that both the server and the client are in the same Kerberos domain. They must access the same KDC (Key Distribution Center) server and share their krb5.keytab le (the default location on any machine is /etc/krb5.keytab ). For more information about Kerberos, see Book “Security Guide”, Chapter 6 “Network Authentication with Kerberos”. 2. Start the gssd service on the client with systemctl start rpc-gssd.service . 3. Start the svcgssd service on the server with systemctl start rpc-svcgssd.service . Kerberos authentication also requires the idmapd daemon to run on the server. For more information refer to /etc/idmapd.conf . For more information about conguring kerberized NFS, refer to the links in Section 28.5, “For More Information”. 28.4 Configuring Clients To congure your host as an NFS client, you do not need to install additional software. All needed packages are installed by default. 28.4.1 Importing File Systems with YaST Authorized users can mount NFS directories from an NFS server into the local le tree using the YaST NFS client module. Proceed as follows: PROCEDURE 28.2: IMPORTING NFS DIRECTORIES 1. Start the YaST NFS client module. 2. Click Add in the NFS Shares tab. Enter the host name of the NFS server, the directory to import, and the mount point at which to mount this directory locally. 404 NFS with Kerberos SLES 12 SP43. When using NFSv4, select Enable NFSv4 in the NFS Settings tab. Additionally, the NFSv4 Domain Name must contain the same value as used by the NFSv4 server. The default domain is localdomain . 4. To use Kerberos authentication for NFS, GSS security must be enabled. Select Enable GSS Security. 5. Enable Open Port in Firewall in the NFS Settings tab if you use a Firewall and want to allow access to the service from remote computers. The rewall status is displayed next to the check box. 6. Click OK to save your changes. The conguration is written to /etc/fstab and the specied le systems are mounted. When you start the YaST conguration client at a later time, it also reads the existing conguration from this le. Tip: NFS as a Root File System On (diskless) systems where the root partition is mounted via network as an NFS share, you need to be careful when conguring the network device with which the NFS share is accessible. When shutting down or rebooting the system, the default processing order is to turn o network connections, then unmount the root partition. With NFS root, this order causes problems as the root partition cannot be cleanly unmounted as the network connection to the NFS share is already not activated. To prevent the system from deactivating the relevant network device, open the network device conguration tab as described in Section 16.4.1.2.5, “Activating the Network Device” and choose On NFSroot in the Device Activation pane. 28.4.2 Importing File Systems Manually The prerequisite for importing le systems manually from an NFS server is a running RPC port mapper. The nfs service takes care to start it properly; thus, start it by entering systemctl start nfs as root . Then remote le systems can be mounted in the le system like local partitions using mount : tux > sudo mount HOST:REMOTE-PATHLOCAL-PATH 405 Importing File Systems Manually SLES 12 SP4To import user directories from the nfs.example.com machine, for example, use: tux > sudo mount nfs.example.com:/home /home The mount takes several mount options. Please bear in mind that all of the mount option stated below are mutually exclusive. nconnect The opton denes the count of TCP conncetions that the clients makes to the NFS server. You can specif any number from 1 to 16, where 1 is the default value if the mount option has not been specied. The nconnect setting is applied only during the rst mount process to the particular NFS server. If the same client executes the mount command to the same NFS server, all already established connections will be shared—no new connection will be established. To change the nconnect setting, you have to unmount all clients connections to the particular NFS server. Then you can dene a new value of the nconnect option. You can nd the current nconnect value in eect in output of the mount command or in the le /proc/mounts . If there is no value of the mount option, then the option has not been used during mounting and the default value 1 is in use. The option applies to NFS v2, v3, and all v4.x variants, Note: Different number of connections than defined by nconnect As you can close and open connections after the rst mount, the actual count of connections necessarily does not have to be the same as the value of nconnect . nosharetransport the option causes that a client uses to mount its own isolated TCP connection. The client will not share the TCP connection with any other mount done before or after. The option applies to NFS v2 and v3. sharetransport The option is a number that identies mounts sharing the same TCP connection. If two or more mounts to a particular NFS server have a dierent value of sharetransport , these mounts will use dierent connections. If you don''t specify the option value for mounts to a particular NFS server, all the mounts will shate one TCP connection. The option applies to NFS v4.x. 406 Importing File Systems Manually SLES 12 SP428.4.2.1 Using the Automount Service The autofs daemon can be used to mount remote le systems automatically. Add the following entry to the /etc/auto.master le: /nfsmounts /etc/auto.nfs Now the /nfsmounts directory acts as the root for all the NFS mounts on the client if the auto.nfs le is lled appropriately. The name auto.nfs is chosen for the sake of convenience —you can choose any name. In auto.nfs add entries for all the NFS mounts as follows: localdata -fstype=nfs server1:/data nfs4mount -fstype=nfs4 server2:/ Activate the settings with systemctl start autofs as root . In this example, /nfsmounts/ localdata , the /data directory of server1 , is mounted with NFS and /nfsmounts/ nfs4mount from server2 is mounted with NFSv4. If the /etc/auto.master le is edited while the service autofs is running, the automounter must be restarted for the changes to take eect with systemctl restart autofs . 28.4.2.2 Manually Editing /etc/fstab A typical NFSv3 mount entry in /etc/fstab looks like this: nfs.example.com:/data /local/path nfs rw,noauto 0 0 For NFSv4 mounts, use nfs4 instead of nfs in the third column: nfs.example.com:/data /local/pathv4 nfs4 rw,noauto 0 0 The noauto option prevents the le system from being mounted automatically at start-up. If you want to mount the respective le system manually, it is possible to shorten the mount command specifying the mount point only: tux > sudo mount /local/path Note: Mounting at Start-Up If you do not enter the noauto option, the init scripts of the system will handle the mount of those le systems at start-up. 407 Importing File Systems Manually SLES 12 SP428.4.3 Parallel NFS (pNFS) NFS is one of the oldest protocols, developed in the ''80s. As such, NFS is usually sucient if you want to share small les. However, when you want to transfer big les or large numbers of clients want to access data, an NFS server becomes a bottleneck and has a signicant impact on the system performance. This is because of les quickly getting bigger, whereas the relative speed of your Ethernet has not fully kept up. When you request a le from a regular NFS server, the server looks up the le metadata, collects all the data and transfers it over the network to your client. However, the performance bottleneck becomes apparent no matter how small or big the les are: With small les most of the time is spent collecting the metadata. With big les most of the time is spent on transferring the data from server to client. pNFS, or parallel NFS, overcomes this limitation as it separates the le system metadata from the location of the data. As such, pNFS requires two types of servers: A metadata or control server that handles all the non-data trac One or more storage server(s) that hold(s) the data The metadata and the storage servers form a single, logical NFS server. When a client wants to read or write, the metadata server tells the NFSv4 client which storage server to use to access the le chunks. The client can access the data directly on the server. SUSE Linux Enterprise Server supports pNFS on the client side only. 28.4.3.1 Configuring pNFS Client With YaST Proceed as described in Procedure 28.2, “Importing NFS Directories”, but click the pNFS (v4.1) check box and optionally NFSv4 share. YaST will do all the necessary steps and will write all the required options in the le /etc/exports . 408 Parallel NFS (pNFS) SLES 12 SP428.4.3.2 Configuring pNFS Client Manually Refer to Section 28.4.2, “Importing File Systems Manually” to start. Most of the conguration is done by the NFSv4 server. For pNFS, the only dierence is to add the minorversion option and the metadata server MDS_SERVER to your mount command: tux > sudo mount -t nfs4 -o minorversion=1 MDS_SERVER MOUNTPOINT To help with debugging, change the value in the /proc le system: tux > sudo echo 32767 > /proc/sys/sunrpc/nfsd_debug tux > sudo echo 32767 > /proc/sys/sunrpc/nfs_debug 28.5 For More Information In addition to the man pages of exports , nfs , and mount , information about conguring an NFS server and client is available in /usr/share/doc/packages/nfsidmap/README . For further documentation online refer to the following Web sites: Find the detailed technical documentation online at SourceForge (http:// nfs.sourceforge.net/) . For instructions for setting up kerberized NFS, refer to NFS Version 4 Open Source Reference Implementation (https://web.archive.org/web/20200628212157/http:// www.citi.umich.edu/projects/nfsv4/linux/krb5-setup.html) . If you have questions on NFSv4, refer to the Linux NFSv4 FAQ (https://web.archive.org/ web/20210506154823/http://www.citi.umich.edu/projects/nfsv4/linux/faq/) . 409 For More Information SLES 12 SP429 Samba Using Samba, a Unix machine can be congured as a le and print server for macOS, Windows, and OS/2 machines. Samba has developed into a fully-edged and rather complex product. Congure Samba with YaST, or by editing the conguration le manually. 29.1 Terminology The following are some terms used in Samba documentation and in the YaST module. SMB protocol Samba uses the SMB (server message block) protocol that is based on the NetBIOS services. Microsoft released the protocol so other software manufacturers could establish connections to a Microsoft domain network. With Samba, the SMB protocol works on top of the TCP/IP protocol, so the TCP/IP protocol must be installed on all clients. Tip: IBM z Systems: NetBIOS Support IBM z Systems merely supports SMB over TCP/IP. NetBIOS support is not available on these systems. CIFS protocol CIFS (common Internet le system) protocol is another protocol supported by Samba. CIFS denes a standard remote le system access protocol for use over the network, enabling groups of users to work together and share documents across the network. NetBIOS NetBIOS is a software interface (API) designed for communication between machines providing a name service. It enables machines connected to the network to reserve names for themselves. After reservation, these machines can be addressed by name. There is no central process that checks names. Any machine on the network can reserve as many names as it wants as long as the names are not already in use. The NetBIOS interface can be implemented for dierent network architectures. An implementation that works relatively 410 Terminology SLES 12 SP4closely with network hardware is called NetBEUI, but this is often called NetBIOS. Network protocols implemented with NetBIOS are IPX from Novell (NetBIOS via TCP/IP) and TCP/ IP. The NetBIOS names sent via TCP/IP have nothing in common with the names used in /etc/hosts or those dened by DNS. NetBIOS uses its own, completely independent naming convention. However, it is recommended to use names that correspond to DNS host names to make administration easier or use DNS natively. This is the default used by Samba. Samba server Samba server provides SMB/CIFS services and NetBIOS over IP naming services to clients. For Linux, there are three daemons for Samba server: smbd for SMB/CIFS services, nmbd for naming services, and winbind for authentication. Samba client The Samba client is a system that uses Samba services from a Samba server over the SMB protocol. Common operating systems, such as Windows and macOS support the SMB protocol. The TCP/IP protocol must be installed on all computers. Samba provides a client for the dierent Unix avors. For Linux, there is a kernel module for SMB that allows the integration of SMB resources on the Linux system level. You do not need to run any daemon for the Samba client. Shares SMB servers provide resources to the clients by means of shares. Shares are printers and directories with their subdirectories on the server. It is exported by means of a name and can be accessed by its name. The share name can be set to any name—it does not need to be the name of the export directory. A printer is also assigned a name. Clients can access the printer by its name. DC A domain controller (DC) is a server that handles accounts in a domain. For data replication, additional domain controllers are available in one domain. 29.2 Installing a Samba Server To install a Samba server, start YaST and select Software Software Management. Choose View Patterns and select File Server. Conrm the installation of the required packages to nish the installation process. 411 Installing a Samba Server SLES 12 SP429.3 Starting and Stopping Samba You can start or stop the Samba server automatically (during boot) or manually. Starting and stopping policy is a part of the YaST Samba server conguration described in Section 29.4.1, “Configuring a Samba Server with YaST”. From a command line, stop services required for Samba with systemctl stop smb nmb and start them with systemctl start nmb smb . The smb service cares about winbind if needed. Tip: winbind winbind is an independent service, and as such is also oered as an individual samba- winbind package. 29.4 Configuring a Samba Server A Samba server in SUSE® Linux Enterprise Server can be congured in two dierent ways: with YaST or manually. Manual conguration oers a higher level of detail, but lacks the convenience of the YaST GUI. 29.4.1 Configuring a Samba Server with YaST To congure a Samba server, start YaST and select Network Services Samba Server. 29.4.1.1 Initial Samba Configuration When starting the module for the rst time, the Samba Installation dialog starts, prompting you to make a few basic decisions concerning administration of the server. At the end of the conguration it prompts for the Samba administrator password (Samba Root Password). For later starts, the Samba Conguration dialog appears. The Samba Installation dialog consists of two steps and optional detailed settings: Workgroup or Domain Name Select an existing name from Workgroup or Domain Name or enter a new one and click Next. Samba Server Type 412 Starting and Stopping Samba SLES 12 SP4In the next step, specify whether your server should act as a primary domain controller (PDC), backup domain controller (BDC), or not act as a domain controller. Continue with Next. If you do not want to proceed with a detailed server conguration, conrm with OK. Then in the nal pop-up box, set the Samba root Password. You can change all settings later in the Samba Conguration dialog with the Start-Up, Shares, Identity, Trusted Domains, and LDAP Settings tabs. 29.4.1.2 Advanced Samba Configuration During the rst start of the Samba server module the Samba Conguration dialog appears directly after the two initial steps described in Section 29.4.1.1, “Initial Samba Configuration”. Use it to adjust your Samba server conguration. After editing your conguration, click OK to save your settings. 29.4.1.2.1 Starting the Server In the Start Up tab, congure the start of the Samba server. To start the service every time your system boots, select During Boot. To activate manual start, choose Manually. More information about starting a Samba server is provided in Section 29.3, “Starting and Stopping Samba”. In this tab, you can also open ports in your rewall. To do so, select Open Port in Firewall. If you have multiple network interfaces, select the network interface for Samba services by clicking Firewall Details, selecting the interfaces, and clicking OK. 29.4.1.2.2 Shares In the Shares tab, determine the Samba shares to activate. There are some predened shares, like homes and printers. Use Toggle Status to switch between Active and Inactive. Click Add to add new shares and Delete to delete the selected share. Allow Users to Share Their Directories enables members of the group in Permitted Group to share directories they own with other users. For example, users for a local scope or DOMAIN\Users for a domain scope. The user also must make sure that the le system permissions allow access. With Maximum Number of Shares, limit the total amount of shares that may be created. To permit access to user shares without authentication, enable Allow Guest Access. 413 Configuring a Samba Server with YaST SLES 12 SP429.4.1.2.3 Identity In the Identity tab, you can determine the domain with which the host is associated (Base Settings) and whether to use an alternative host name in the network (NetBIOS Hostname). It is also possible to use Microsoft Windows Internet Name Service (WINS) for name resolution. In this case, activate Use WINS for Hostname Resolution and decide whether to Retrieve WINS server via DHCP. To set expert global settings or set a user authentication source, for example LDAP instead of TDB database, click Advanced Settings. 29.4.1.2.4 Trusted Domains To enable users from other domains to access your domain, make the appropriate settings in the Trusted Domains tab. To add a new domain, click Add. To remove the selected domain, click Delete. 29.4.1.2.5 LDAP Settings In the tab LDAP Settings, you can determine the LDAP server to use for authentication. To test the connection to your LDAP server, click Test Connection. To set expert LDAP settings or use default values, click Advanced Settings. For more information about LDAP conguration, see Book “Security Guide”, Chapter 5 “LDAP—A Directory Service”. 29.4.2 Configuring the Server Manually If you intend to use Samba as a server, install samba . The main conguration le for Samba is /etc/samba/smb.conf . This le can be divided into two logical parts. The [global] section contains the central and global settings. The following default sections contain the individual le and printer shares: [homes] [proles] [users] [groups] 414 Configuring the Server Manually SLES 12 SP4[printers] [print$] Using this approach, options of the shares can be set dierently or globally in the [global] section, which makes the conguration le easier to understand. 29.4.2.1 The global Section The following parameters of the [global] section should be modied to match the requirements of your network setup, so other machines can access your Samba server via SMB in a Windows environment. workgroup = WORKGROUP This line assigns the Samba server to a workgroup. Replace WORKGROUP with an appropriate workgroup of your networking environment. Your Samba server appears under its DNS name unless this name has been assigned to some other machine in the network. If the DNS name is not available, set the server name using netbiosname=MYNAME . For more details about this parameter, see the smb.conf man page. os level = 20 This parameter triggers whether your Samba server tries to become LMB (local master browser) for its workgroup. Choose a very low value such as 2 to spare the existing Windows network from any interruptions caused by a miscongured Samba server. More information about this topic can be found in the Network Browsing chapter of the Samba 3 Howto; for more information on the Samba 3 Howto, see Section 29.9, “For More Information”. If no other SMB server is in your network (such as a Windows 2000 server) and you want the Samba server to keep a list of all systems present in the local environment, set the os level to a higher value (for example, 65 ). Your Samba server is then chosen as LMB for your local network. When changing this setting, consider carefully how this could aect an existing Windows network environment. First test the changes in an isolated network or at a noncritical time of day. wins support and wins server To integrate your Samba server into an existing Windows network with an active WINS server, enable the wins server option and set its value to the IP address of that WINS server. 415 Configuring the Server Manually SLES 12 SP4If your Windows machines are connected to separate subnets and need to still be aware of each other, you have to set up a WINS server. To turn a Samba server into such a WINS server, set the option wins support = Yes . Make sure that only one Samba server of the network has this setting enabled. The options wins server and wins support must never be enabled at the same time in your smb.conf le. 29.4.2.2 Shares The following examples illustrate how a CD-ROM drive and the user directories ( homes ) are made available to the SMB clients. [cdrom] To avoid having the CD-ROM drive accidentally made available, these lines are deactivated with comment marks (semicolons in this case). Remove the semicolons in the rst column to share the CD-ROM drive with Samba. EXAMPLE 29.1: A CD-ROM SHARE [cdrom] comment = Linux CD-ROM path = /media/cdrom locking = No [cdrom] and comment The [cdrom] section entry is the name of the share that can be seen by all SMB clients on the network. An additional comment can be added to further describe the share. path = /media/cdrom path exports the directory /media/cdrom . By means of a very restrictive default conguration, this kind of share is only made available to the users present on this system. If this share should be made available to everybody, add a line guest ok = yes to the conguration. This setting gives read permissions to anyone on the network. It is recommended to handle this parameter with great care. This applies even more to the use of this parameter in the [global] section. [homes] The [homes] share is of special importance here. If the user has a valid account and password for the Linux le server and his own home directory, he can be connected to it. EXAMPLE 29.2: [HOMES] SHARE [homes] 416 Configuring the Server Manually SLES 12 SP4comment = Home Directories valid users = %S browseable = No read only = No inherit acls = Yes [homes] As long as there is no other share using the share name of the user connecting to the SMB server, a share is dynamically generated using the [homes] share directives. The resulting name of the share is the user name. valid users = %S %S is replaced with the concrete name of the share when a connection has been successfully established. For a [homes] share, this is always the user name. As a consequence, access rights to a user''s share are restricted exclusively to that user. browseable = No This setting makes the share invisible in the network environment. read only = No By default, Samba prohibits write access to any exported share by means of the read only = Yes parameter. To make a share writable, set the value read only = No , which is synonymous with writable = Yes . create mask = 0640 Systems that are not based on MS Windows NT do not understand the concept of Unix permissions, so they cannot assign permissions when creating a le. The parameter create mask denes the access permissions assigned to newly created les. This only applies to writable shares. In eect, this setting means the owner has read and write permissions and the members of the owner''s primary group have read permissions. valid users = %S prevents read access even if the group has read permissions. For the group to have read or write access, deactivate the line valid users = %S . Warning: Do not share NFS mounts with Samba Sharing NFS mounts with samba may result in data loss and is not supported. Install Samba directly on the le server or consider using alternatives such as iSCSI . 417 Configuring the Server Manually SLES 12 SP429.4.2.3 Security Levels To improve security, each share access can be protected with a password. SMB oers the following ways of checking permissions: User Level Security ( security = user ) This variant introduces the concept of the user to SMB. Each user must register with the server with his or her own password. After registration, the server can grant access to individual exported shares dependent on user names. ADS Level Security ( security = ADS ) In this mode, Samba will act as a domain member in an Active Directory environment. To operate in this mode, the machine running Samba needs Kerberos installed and congured. You must join the machine using Samba to the ADS realm. This can be done using the YaST Windows Domain Membership module. Domain Level Security ( security = domain ) This mode will only work correctly if the machine has been joined into a Windows NT Domain. Samba will try to validate user name and password by passing it to a Windows NT Primary or Backup Domain Controller. The same way as a Windows NT Server would do. It expects the encrypted passwords parameter to be set to yes . The selection of share, user, server, or domain level security applies to the entire server. It is not possible to oer individual shares of a server conguration with share level security and others with user level security. However, you can run a separate Samba server for each congured IP address on a system. More information about this subject can be found in the Samba 3 HOWTO. For multiple servers on one system, pay attention to the options interfaces and bind interfaces only . 29.5 Configuring Clients Clients can only access the Samba server via TCP/IP. NetBEUI and NetBIOS via IPX cannot be used with Samba. 418 Configuring Clients SLES 12 SP429.5.1 Configuring a Samba Client with YaST Congure a Samba client to access resources (les or printers) on the Samba or Windows server. Enter the NT or Active Directory domain or workgroup in the dialog Network Services Windows Domain Membership. If you activate Also Use SMB Information for Linux Authentication, the user authentication runs over the Samba, NT or Kerberos server. Click Expert Settings for advanced conguration options. For example, use the Mount Server Directories table to enable mounting server home directory automatically with authentication. This way users can access their home directories when hosted on CIFS. For details, see the pam_mount man page. After completing all settings, conrm the dialog to nish the conguration. 29.6 Samba as Login Server In networks where predominantly Windows clients are found, it is often preferable that users may only register with a valid account and password. In a Windows-based network, this task is handled by a primary domain controller (PDC). You can use a Windows NT server congured as PDC, but this task can also be done with a Samba server. The entries that must be made in the [global] section of smb.conf are shown in Example 29.3, “Global Section in smb.conf”. EXAMPLE 29.3: GLOBAL SECTION IN SMB.CONF [global] workgroup = WORKGROUP domain logons = Yes domain master = Yes It is necessary to prepare user accounts and passwords in an encryption format that conforms with Windows. Do this with the command smbpasswd -a name . Create the domain account for the computers, required by the Windows domain concept, with the following commands: useradd hostname\$ smbpasswd -a -m hostname With the useradd command, a dollar sign is added. The command smbpasswd inserts this automatically when the parameter -m is used. The commented conguration example ( /usr/ share/doc/packages/samba/examples/smb.conf.SUSE ) contains settings that automate this task. 419 Configuring a Samba Client with YaST SLES 12 SP4add machine script = /usr/sbin/useradd -g nogroup -c "NT Machine Account" \ -s /bin/false %m\$ To make sure that Samba can execute this script correctly, choose a Samba user with the required administrator permissions and add it to the ntadmin group. Then all users belonging to this Linux group can be assigned Domain Admin status with the command: net groupmap add ntgroup="Domain Admins" unixgroup=ntadmin 29.7 Samba Server in the Network with Active Directory If you run Linux servers and Windows servers together, you can build two independent authentication systems and networks or connect servers to one network with one central authentication system. Because Samba can cooperate with an active directory domain, you can join your SUSE Linux Enterprise Server to Active Directory (AD). To join an AD domain proceed as follows: 1. Log in as root and start YaST. 2. Start Network Services Windows Domain Membership. 3. Enter the domain to join at Domain or Workgroup in the Windows Domain Membership screen. 420 Samba Server in the Network with Active Directory SLES 12 SP4FIGURE 29.1: DETERMINING WINDOWS DOMAIN MEMBERSHIP 4. Check Also Use SMB Information for Linux Authentication to use the SMB source for Linux authentication on your server. 5. Click OK and conrm the domain join when prompted for it. 6. Provide the password for the Windows Administrator on the AD server and click OK. Your server is now set up to pull in all authentication data from the Active Directory domain controller. Tip: Identity Mapping In an environment with more than one Samba server, UIDs and GIDs will not be created consistently. The UIDs that get assigned to users will be dependent on the order in which they rst log in, which results in UID conicts across servers. To x this, you need to use identity mapping. See https://www.samba.org/samba/docs/man/Samba-HOWTO- Collection/idmapper.html for more details. 421 Samba Server in the Network with Active Directory SLES 12 SP429.8 Advanced Topics This section introduces more advanced techniques to manage both the client and server part of the Samba suite. 29.8.1 Transparent File Compression on Btrfs Samba allows clients to remotely manipulate le and directory compression ags for shares placed on the Btrfs le system. Windows Explorer provides the ability to ag les/directories for transparent compression via the File Properties Advanced dialog: FIGURE 29.2: WINDOWS EXPLORER ADVANCED ATTRIBUTES DIALOG Files agged for compression are transparently compressed and decompressed by the underlying le system when accessed or modied. This normally results in storage capacity savings at the expense of extra CPU overhead when accessing the le. New les and directories inherit the compression ag from the parent directory, unless created with the FILE_NO_COMPRESSION option. Windows Explorer presents compressed les and directories visually dierently to those that are not compressed: FIGURE 29.3: WINDOWS EXPLORER DIRECTORY LISTING WITH COMPRESSED FILES You can enable Samba share compression either manually by adding vfs objects = btrfs to the share conguration in /etc/samba/smb.conf , or using YaST: Network Services Samba Server Add, and checking Utilize Btrfs Features. 422 Advanced Topics SLES 12 SP4A general overview of compression on Btrfs can be found in Book “Storage Administration Guide”, Chapter 1 “Overview of File Systems in Linux”, Section 1.2.2.1 “Mounting Compressed Btrfs File Systems”. 29.8.2 Snapshots Snapshots, also called Shadow Copies, are copies of the state of a le system subvolume at a certain point of time. Snapper is the tool to manage these snapshots in Linux. Snapshots are supported on the Btrfs le system or thinly-provisioned LVM volumes. The Samba suite supports managing remote snapshots through the FSRVP protocol on both the server and client side. 29.8.2.1 Previous Versions Snapshots on a Samba server can be exposed to remote Windows clients as le or directory previous versions. To enable snapshots on a Samba server, the following conditions must be fullled: The SMB network share resides on a Btrfs subvolume. The SMB network share path has a related snapper conguration le. You can create the snapper le with snapper -c create-config /path/to/share For more information on snapper, see Chapter 7, System Recovery and Snapshot Management with Snapper. The snapshot directory tree must allow access for relevant users. For more information, see the PERMISSIONS section of the vfs_snapper manual page ( man 8 vfs_snapper ). To support remote snapshots, you need to modify the /etc/samba/smb.conf le. You can do it either with YaST Network Services Samba Server, or manually by enhancing the relevant share section with vfs objects = snapper Note that you need to restart the Samba service for manual smb.conf changes to take eect: systemctl restart nmb smb 423 Snapshots SLES 12 SP4FIGURE 29.4: ADDING A NEW SAMBA SHARE WITH SNAPSHOTTING ENABLED After being congured, snapshots created by snapper for the Samba share path can be accessed from Windows Explorer from a le or directory''s Previous Versions tab. 424 Snapshots SLES 12 SP4FIGURE 29.5: THE PREVIOUS VERSIONS TAB IN WINDOWS EXPLORER 29.8.2.2 Remote Share Snapshots By default, snapshots can only be created and deleted on the Samba server locally, via the snapper command line utility, or using snapper''s time line feature. Samba can be congured to process share snapshot creation and deletion requests from remote hosts using the File Server Remote VSS Protocol (FSRVP). 425 Snapshots SLES 12 SP4In addition to the conguration and prerequisites documented in Section  29.8.2.1, “Previous Versions”, the following global conguration is required in /etc/samba/smb.conf : [global] rpc_daemon:fssd = fork registry shares = yes include = registry FSRVP clients, including Samba''s rpcclient and Windows Server 2012 DiskShadow.exe , can then instruct Samba to create or delete a snapshot for a given share, and expose the snapshot as a new share. 29.8.2.3 Managing Snapshots Remotely from Linux with rpcclient The samba-client package contains an FSRVP client that can remotely request a Windows/ Samba server to create and expose a snapshot of a given share. You can then use existing tools in SUSE Linux Enterprise Server to mount the exposed share and back up its les. Requests to the server are sent using the rpcclient binary. EXAMPLE 29.4: USING rpcclient TO REQUEST A WINDOWS SERVER 2012 SHARE SNAPSHOT Connect to win-server.example.com server as an administrator in an EXAMPLE domain: # rpcclient -U ''EXAMPLE\Administrator'' ncacn_np:win-server.example.com[ndr64,sign] Enter EXAMPLE/Administrator''s password: Check that the SMB share is visible for rpcclient : rpcclient $> netshareenum netname: windows_server_2012_share remark: path: C:\Shares\windows_server_2012_share password: (null) Check that the SMB share supports snapshot creation: rpcclient $> fss_is_path_sup windows_server_2012_share \ UNC \\WIN-SERVER\windows_server_2012_share\ supports shadow copy requests Request the creation of a share snapshot: rpcclient $> fss_create_expose backup ro windows_server_2012_share 13fe880e-e232-493d-87e9-402f21019fb6: shadow-copy set created 13fe880e-e232-493d-87e9-402f21019fb6(1c26544e-8251-445f-be89-d1e0a3938777): \ 426 Snapshots SLES 12 SP4\\WIN-SERVER\windows_server_2012_share\ shadow-copy added to set 13fe880e-e232-493d-87e9-402f21019fb6: prepare completed in 0 secs 13fe880e-e232-493d-87e9-402f21019fb6: commit completed in 1 secs 13fe880e-e232-493d-87e9-402f21019fb6(1c26544e-8251-445f-be89-d1e0a3938777): \ share windows_server_2012_share@{1C26544E-8251-445F-BE89-D1E0A3938777} \ exposed as a snapshot of \\WIN-SERVER\windows_server_2012_share\ Conrm that the snapshot share is exposed by the server: rpcclient $> netshareenum netname: windows_server_2012_share remark: path: C:\Shares\windows_server_2012_share password: (null) netname: windows_server_2012_share@{1C26544E-8251-445F-BE89-D1E0A3938777} remark: (null) path: \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy{F6E6507E-F537-11E3-9404- B8AC6F927453}\Shares\windows_server_2012_share\ password: (null) Attempt to delete the snapshot share: rpcclient $> fss_delete windows_server_2012_share \ 13fe880e-e232-493d-87e9-402f21019fb6 1c26544e-8251-445f-be89-d1e0a3938777 13fe880e-e232-493d-87e9-402f21019fb6(1c26544e-8251-445f-be89-d1e0a3938777): \ \\WIN-SERVER\windows_server_2012_share\ shadow-copy deleted Conrm that the snapshot share has been removed by the server: rpcclient $> netshareenum netname: windows_server_2012_share remark: path: C:\Shares\windows_server_2012_share password: (null) 29.8.2.4 Managing Snapshots Remotely from Windows with DiskShadow.exe You can manage snapshots of SMB shares on the Linux Samba server from the Windows environment acting as a client as well. Windows Server 2012 includes the DiskShadow.exe utility that can manage remote shares similar to the rpcclient described in Section 29.8.2.3, “Managing Snapshots Remotely from Linux with rpcclient”. Note that you need to carefully set up the Samba server rst. 427 Snapshots SLES 12 SP4Following is an example procedure to set up the Samba server so that the Windows Server client can manage its share''s snapshots. Note that EXAMPLE is the Active Directory domain used in the testing environment, fsrvp-server.example.com is the host name of the Samba server, and /srv/smb is the path to the SMB share. PROCEDURE 29.1: DETAILED SAMBA SERVER CONFIGURATION 1. Join Active Directory domain via YaST. For more information, Section 29.7, “Samba Server in the Network with Active Directory”. 2. Ensure that the Active Domain DNS entry was correct: fsrvp-server:~ # net -U ''Administrator'' ads dns register \ fsrvp-server.example.com Successfully registered hostname with DNS 3. Create Btrfs subvolume at /srv/smb fsrvp-server:~ # btrfs subvolume create /srv/smb 4. Create snapper conguration le for path /srv/smb fsrvp-server:~ # snapper -c create-config /srv/smb 5. Create new share with path /srv/smb , and YaST Expose Snapshots check box enabled. Make sure to add the following snippets to the global section of /etc/samba/smb.conf as mentioned in Section 29.8.2.2, “Remote Share Snapshots”: [global] rpc_daemon:fssd = fork registry shares = yes include = registry 6. Restart Samba with systemctl restart nmb smb 7. Congure snapper permissions: fsrvp-server:~ # snapper -c set-config \ ALLOW_USERS="EXAMPLE\\\\Administrator EXAMPLE\\\\win-client$" Ensure that any ALLOW_USERS are also permitted traversal of the .snapshots subdirectory. fsrvp-server:~ # snapper -c set-config SYNC_ACL=yes 428 Snapshots SLES 12 SP4Important: Path Escaping Be careful about the ''\'' escapes! Escape twice to ensure that the value stored in / etc/snapper/configs/ is escaped once. "EXAMPLE\win-client$" corresponds to the Windows client computer account. Windows issues initial FSRVP requests while authenticated with this account. 8. Grant Windows client account necessary privileges: fsrvp-server:~ # net -U ''Administrator'' rpc rights grant \ "EXAMPLE\\win-client$" SeBackupPrivilege Successfully granted rights. The previous command is not needed for the "EXAMPLE\Administrator" user, which has privileges already granted. PROCEDURE 29.2: WINDOWS CLIENT SETUP AND DiskShadow.exe IN ACTION 1. Boot Windows Server 2012 (example host name WIN-CLIENT). 2. Join the same Active Directory domain EXAMPLE as with the SUSE Linux Enterprise Server. 3. Reboot. 4. Open Powershell. 5. Start DiskShadow.exe and begin the backup procedure: PS C:\Users\Administrator.EXAMPLE> diskshadow.exe Microsoft DiskShadow version 1.0 Copyright (C) 2012 Microsoft Corporation On computer: WIN-CLIENT, 6/17/2014 3:53:54 PM DISKSHADOW> begin backup 6. Specify that shadow copy persists across program exit, reset or reboot: DISKSHADOW> set context PERSISTENT 7. Check whether the specied share supports snapshots, and create one: DISKSHADOW> add volume \\fsrvp-server\sles_snapper 429 Snapshots SLES 12 SP4DISKSHADOW> create Alias VSS_SHADOW_1 for shadow ID {de4ddca4-4978-4805-8776-cdf82d190a4a} set as \ environment variable. Alias VSS_SHADOW_SET for shadow set ID {c58e1452-c554-400e-a266-d11d5c837cb1} \ set as environment variable. Querying all shadow copies with the shadow copy set ID \ {c58e1452-c554-400e-a266-d11d5c837cb1} * Shadow copy ID = {de4ddca4-4978-4805-8776-cdf82d190a4a} %VSS_SHADOW_1% - Shadow copy set: {c58e1452-c554-400e-a266-d11d5c837cb1} %VSS_SHADOW_SET% - Original count of shadow copies = 1 - Original volume name: \\FSRVP-SERVER\SLES_SNAPPER\ \ [volume not on this machine] - Creation time: 6/17/2014 3:54:43 PM - Shadow copy device name: \\FSRVP-SERVER\SLES_SNAPPER@{31afd84a-44a7-41be-b9b0-751898756faa} - Originating machine: FSRVP-SERVER - Service machine: win-client.example.com - Not exposed - Provider ID: {89300202-3cec-4981-9171-19f59559e0f2} - Attributes: No_Auto_Release Persistent FileShare Number of shadow copies listed: 1 8. Finish the backup procedure: DISKSHADOW> end backup 9. After the snapshot was created, try to delete it and verify the deletion: DISKSHADOW> delete shadows volume \\FSRVP-SERVER\SLES_SNAPPER\ Deleting shadow copy {de4ddca4-4978-4805-8776-cdf82d190a4a} on volume \ \\FSRVP-SERVER\SLES_SNAPPER\ from provider \ {89300202-3cec-4981-9171-19f59559e0f2} [Attributes: 0x04000009]... Number of shadow copies deleted: 1 DISKSHADOW> list shadows all Querying all shadow copies on the computer ... No shadow copies found in system. 430 Snapshots SLES 12 SP429.9 For More Information Documentation for Samba ships with the samba-doc package which is not installed by default. Install it with zypper install samba-doc . Enter apropos samba at the command line to display some manual pages or browse the /usr/share/doc/packages/samba directory for more online documentation and examples. Find a commented example conguration ( smb.conf.SUSE ) in the examples subdirectory. Another le to look for Samba related information is /usr/share/doc/packages/samba/README.SUSE . The Samba  HOWTO (see https://wiki.samba.org ) provided by the Samba team includes a section about troubleshooting. In addition to that, Part V of the document provides a step-by- step guide to checking your conguration. 431 For More Information SLES 12 SP430 On-Demand Mounting with Autofs autofs is a program that automatically mounts specied directories on an on- demand basis. It is based on a kernel module for high eciency, and can manage both local directories and network shares. These automatic mount points are mounted only when they are accessed, and unmounted after a certain period of inactivity. This on-demand behavior saves bandwidth and results in better performance than static mounts managed by /etc/fstab . While autofs is a control script, automount is the command (daemon) that does the actual auto- mounting. 30.1 Installation autofs is not installed on SUSE Linux Enterprise Server by default. To use its auto-mounting capabilities, rst install it with sudo zypper install autofs 30.2 Configuration You need to congure autofs manually by editing its conguration les with a text editor, such as vim . There are two basic steps to congure autofs—the master map le, and specic map les. 30.2.1 The Master Map File The default master conguration le for autofs is /etc/auto.master . You can change its location by changing the value of the DEFAULT_MASTER_MAP_NAME option in /etc/sysconfig/ autofs . Here is the content of the default one for SUSE Linux Enterprise Server: # # Sample auto.master file # This is an automounter map and it has the following format # key [ -mount-options-separated-by-comma ] location 432 Installation SLES 12 SP4# For details of the format look at autofs(5). 1 # #/misc /etc/auto.misc 2 #/net -hosts # # Include /etc/auto.master.d/*.autofs 3 # #+dir:/etc/auto.master.d # # Include central master map if it can be found using # nsswitch sources. # # Note that if there are entries for /net or /misc (as # above) in the included master map any keys that are the # same will not be seen as the first read key seen takes # precedence. # +auto.master 4 1 The autofs manual page ( man 5 autofs ) oers a lot of valuable information on the format of the automounter maps. 2 Although commented out (#) by default, this is an example of a simple automounter mapping syntax. 3 In case you need to split the master map into several les, uncomment the line, and put the mappings (suxed with .autofs ) in the /etc/auto.master.d/ directory. 4 +auto.master ensures that those using NIS (see Book “Security Guide”, Chapter 3 “Using NIS”, Section 3.1 “Configuring NIS Servers” for more information on NIS) will still nd their master map. Entries in auto.master have three elds with the following syntax: mount point map name options mount point The base location where to mount the autofs le system, such as /home . map name The name of a map source to use for mounting. For the syntax of the maps les, see Section 30.2.2, “Map Files”. options These options (if specied) will apply as defaults to all entries in the given map. 433 The Master Map File SLES 12 SP4Tip: For More Information For more detailed information on the specic values of the optional map-type , format , and options , see the auto.master manual page ( man 5 auto.master ). The following entry in auto.master tells autofs to look in /etc/auto.smb , and create mount points in the /smb directory. /smb /etc/auto.smb 30.2.1.1 Direct Mounts Direct mounts create a mount point at the path specied inside the relevant map le. Instead of specifying the mount point in auto.master , replace the mount point eld with /- . For example, the following line tells autofs to create a mount point at the place specied in auto.smb : /- /etc/auto.smb Tip: Maps without Full Path If the map le is not specied with its full local or network path, it is located using the Name Service Switch (NSS) conguration: /- auto.smb 30.2.2 Map Files Important: Other Types of Maps Although les are the most common types of maps for auto-mounting with autofs , there are other types as well. A map specication can be the output of a command, or a result of a query in LDAP or database. For more detailed information on map types, see the manual page man 5 auto.master . 434 Map Files SLES 12 SP4Map les specify the (local or network) source location, and the mount point where to mount the source locally. The general format of maps is similar to the master map. The dierence is that the options appear between the mount point and the location instead of at the end of the entry: mount point options location Make sure that map les are not marked as executable. You can remove the executable bits by executing chmod -x MAP_FILE . mount point Species where to mount the source location. This can be either a single directory name (so-called indirect mount) to be added to the base mount point specied in auto.master , or the full path of the mount point (direct mount, see Section 30.2.1.1, “Direct Mounts”). options Species optional comma-separated list of mount options for the relevant entries. If auto.master contains options for this map le as well, theses are appended. location Species from where the le system is to be mounted. It is usually an NFS or SMB volume in the usual notation host_name:path_name . If the le system to be mounted begins with a ''/'' (such as local /dev entries or smbfs shares), a colon symbol '':'' needs to be prexed, such as :/dev/sda1 . 30.3 Operation and Debugging This section introduces information on how to control the autofs service operation, and how to view more debugging information when tuning the automounter operation. 30.3.1 Controlling the autofs Service The operation of the autofs service is controlled by systemd . The general syntax of the systemctl command for autofs is sudo systemctl SUB_COMMAND autofs where SUB_COMMAND is one of: enable 435 Operation and Debugging SLES 12 SP4Starts the automounter daemon at boot. start Starts the automounter daemon. stop Stops the automounter daemon. Automatic mount points are not accessible. status Prints the current status of the autofs service together with a part of a relevant log le. restart Stops and starts the automounter, terminating all running daemons and starting new ones. reload Checks the current auto.master map, restarts those daemons whose entries have changed, and starts new ones for new entries. 30.3.2 Debugging the Automounter Problems If you experience problems when mounting directories with autofs , it is useful to run the automount daemon manually and watch its output messages: 1. Stop autofs . sudo systemctl stop autofs 2. From one terminal, run automount manually in the foreground, producing verbose output. sudo automount -f -v 3. From another terminal, try to mount the auto-mounting le systems by accessing the mount points (for example by cd or ls ). 4. Check the output of automount from the rst terminal for more information why the mount failed, or why it was not even attempted. 436 Debugging the Automounter Problems SLES 12 SP430.4 Auto-Mounting an NFS Share The following procedure illustrates how to congure autofs to auto-mount an NFS share available on your network. It makes use of the information mentioned above, and assumes you are familiar with NFS exports. For more information on NFS, see Chapter 28, Sharing File Systems with NFS. 1. Edit the master map le /etc/auto.master : sudo vim /etc/auto.master Add a new entry for the new NFS mount at the end of /etc/auto.master : /nfs /etc/auto.nfs --timeout=10 It tells autofs that the base mount point is /nfs , the NFS shares are specied in the /etc/auto.nfs map, and that all shares in this map will be automatically unmounted after 10 seconds of inactivity. 2. Create a new map le for NFS shares: sudo vim /etc/auto.nfs /etc/auto.nfs normally contains a separate line for each NFS share. Its format is described in Section 30.2.2, “Map Files”. Add the line describing the mount point and the NFS share network address: export jupiter.com:/home/geeko/doc/export The above line means that the /home/geeko/doc/export directory on the jupiter.com host will be auto-mounted to the /nfs/export directory on the local host ( /nfs is taken from the auto.master map) when requested. The /nfs/export directory will be created automatically by autofs . 3. Optionally comment out the related line in /etc/fstab if you previously mounted the same NFS share statically. The line should look similar to this: #jupiter.com:/home/geeko/doc/export /nfs/export nfs defaults 0 0 4. Reload autofs and check if it works: sudo systemctl restart autofs 437 Auto-Mounting an NFS Share SLES 12 SP4# ls -l /nfs/export total 20 drwxr-xr-x 6 1001 users 4096 Oct 25 08:56 ./ drwxr-xr-x 3 root root 0 Apr 1 09:47 ../ drwxr-xr-x 5 1001 users 4096 Jan 14 2013 .images/ drwxr-xr-x 10 1001 users 4096 Aug 16 2013 .profiled/ drwxr-xr-x 3 1001 users 4096 Aug 30 2013 .tmp/ drwxr-xr-x 4 1001 users 4096 Oct 25 08:56 SLE-12-manual/ If you can see the list of les on the remote share, then autofs is functioning. 30.5 Advanced Topics This section describes topics that are beyond the basic introduction to autofs—auto-mounting of NFS shares that are available on your network, using wild cards in map les, and information specic to the CIFS le system. 30.5.1 /net Mount Point This helper mount point is useful if you use a lot of NFS shares. /net auto-mounts all NFS shares on your local network on demand. The entry is already present in the auto.master le, so all you need to do is uncomment it and restart autofs : /net -hosts systemctl restart autofs For example, if you have a server named jupiter with an NFS share called /export , you can mount it by typing # cd /net/jupiter/export on the command line. 30.5.2 Using Wild Cards to Auto-Mount Subdirectories If you have a directory with subdirectories that you need to auto-mount individually—the typical case is the /home directory with individual users'' home directories inside— autofs oers a clever solution for that. 438 Advanced Topics SLES 12 SP4In case of home directories, add the following line in auto.master : /home /etc/auto.home Now you need to add the correct mapping to the /etc/auto.home le, so that the users'' home directories are mounted automatically. One solution is to create separate entries for each directory: wilber jupiter.com:/home/wilber penguin jupiter.com:/home/penguin tux jupiter.com:/home/tux [...] This is very awkward as you need to manage the list of users inside auto.home . You can use the asterisk ''*'' instead of the mount point, and the ampersand ''&'' instead of the directory to be mounted: * jupiter:/home/& 30.5.3 Auto-Mounting CIFS File System If you want to auto-mount an SMB/CIFS share (see Chapter 29, Samba for more information on the SMB/CIFS protocol), you need to modify the syntax of the map le. Add -fstype=cifs in the option eld, and prex the share location with a colon '':''. mount point -fstype=cifs ://jupiter.com/export 439 Auto-Mounting CIFS File System SLES 12 SP431 SLP Conguring a network client requires detailed knowledge about services provided over the network (such as printing or LDAP, for example). To make it easier to congure such services on a network client, the “service location protocol” (SLP) was developed. SLP makes the availability and conguration data of selected services known to all clients in the local network. Applications that support SLP can use this information to be congured automatically. SUSE® Linux Enterprise Server supports installation using installation sources provided with SLP and contains many system services with integrated support for SLP. You can use SLP to provide networked clients with central functions, such as an installation server, le server, or print server on your system. Services that oer SLP support include cupsd, login, ntp, openldap2, postx, rpasswd, rsyncd, saned, sshd (via sh), vnc, and ypserv. All packages necessary to use SLP services on a network client are installed by default. However, if you want to provide services via SLP, check that the openslp-server package is installed. 31.1 The SLP Front-End slptool slptool is a command line tool to query and register SLP services. The query functions are useful for diagnostic purposes. The most important slptool subcommands are listed below. slptool   --help lists all available options and functions. findsrvtypes List all service types available on the network. tux > slptool findsrvtypes service:install.suse:nfs service:install.suse:ftp service:install.suse:http service:install.suse:smb service:ssh service:fish service:YaST.installation.suse:vnc service:smtp service:domain service:management-software.IBM:hardware-management-console service:rsync 440 The SLP Front-End slptool SLES 12 SP4service:ntp service:ypserv findsrvs SERVICE_TYPE List all servers providing SERVICE_TYPE tux > slptool findsrvs service:ntp service:ntp://ntp.example.com:123,57810 service:ntp://ntp2.example.com:123,57810 findattrs SERVICE_TYPE // HOST List attributes for SERVICE_TYPE on HOST tux > slptool findattrs service:ntp://ntp.example.com (owner=tux),(email=tux@example.com) register SERVICE type // HOST : PORT "( ATTRIBUTE=VALUE ),( ATTRIBUTE=VALUE )" Registers SERVICE_TYPE on HOST with an optional list of attributes slptool register service:ntp://ntp.example.com:57810 \ "(owner=tux),(email=tux@example.com)" deregister SERVICE_TYPE // host De-registers SERVICE_TYPE on HOST slptool deregister service:ntp://ntp.example.com For more information run slptool --help . 31.2 Providing Services via SLP To provide SLP services, the SLP daemon ( slpd ) must be running. Like most system services in SUSE Linux Enterprise Server, slpd is controlled by means of a separate start script. After the installation, the daemon is inactive by default. To activate it for the current session, run sudo systemctl start slpd . If slpd should be activated on system start-up, run sudo systemctl enable slpd . Many applications in SUSE Linux Enterprise Server have integrated SLP support via the libslp library. If a service has not been compiled with SLP support, use one of the following methods to make it available via SLP: Static Registration with /etc/slp.reg.d 441 Providing Services via SLP SLES 12 SP4Create a separate registration le for each new service. The following example registers a scanner service: ## Register a saned service on this system ## en means english language ## 65535 disables the timeout, so the service registration does ## not need refreshes service:scanner.sane://$HOSTNAME:6566,en,65535 watch-port-tcp=6566 description=SANE scanner daemon The most important line in this le is the service URL, which begins with service: . This contains the service type ( scanner.sane ) and the address under which the service is available on the server. $HOSTNAME is automatically replaced with the full host name. The name of the TCP port on which the relevant service can be found follows, separated by a colon. Then enter the language in which the service should appear and the duration of registration in seconds. These should be separated from the service URL by commas. Set the value for the duration of registration between 0 and 65535 . 0 prevents registration. 65535 removes all restrictions. The registration le also contains the two variables watch-port-tcp and description . watch-port-tcp links the SLP service announcement to whether the relevant service is active by having slpd check the status of the service. The second variable contains a more precise description of the service that is displayed in suitable browsers. Tip: YaST and SLP Some services brokered by YaST, such as an installation server or YOU server, perform this registration automatically when you activate SLP in the module dialogs. YaST then creates registration les for these services. Static Registration with /etc/slp.reg The only dierence between this method and the procedure with /etc/slp.reg.d is that all services are grouped within a central le. Dynamic Registration with slptool If a service needs to be registered dynamically without the need of conguration les, use the slptool command line utility. The same utility can also be used to de-register an existing service oering without restarting slpd . See Section 31.1, “The SLP Front-End slptool” for details. 442 Providing Services via SLP SLES 12 SP431.2.1 Setting up an SLP Installation Server Announcing the installation data via SLP within your network makes the network installation much easier, since the installation data such as IP address of the server or the path to the installation media are automatically required via SLP query. Refer to Book “Deployment Guide”, Chapter 8 “Setting Up the Server Holding the Installation Sources” for instructions. 31.3 For More Information RFC 2608, 2609, 2610 RFC 2608 generally deals with the denition of SLP. RFC 2609 deals with the syntax of the service URLs used in greater detail and RFC 2610 deals with DHCP via SLP. http://www.openslp.org The home page of the OpenSLP project. /usr/share/doc/packages/openslp This directory contains the documentation for SLP coming with the openslp-server package, including a README.SUSE containing the SUSE Linux Enterprise Server details, the RFCs, and two introductory HTML documents. Programmers who want to use the SLP functions will nd more information in the Programmers Guide that is included in the openslp-devel package that is provided with the SUSE Software Development Kit. 443 Setting up an SLP Installation Server SLES 12 SP432 The Apache HTTP Server According to the survey from http://www.netcraft.com/ , the Apache HTTP Server (Apache) is the world''s most widely-used Web server. Developed by the Apache Software Foundation (http://www.apache.org/ ), it is available for most operating systems. SUSE® Linux Enterprise Server includes Apache version 2.4. In this chapter, learn how to install, congure and set up a Web server; how to use SSL, CGI, and additional modules; and how to troubleshoot Apache. 32.1 Quick Start With this section, quickly set up and start Apache. You must be root to install and congure Apache. 32.1.1 Requirements Make sure the following requirements are met before trying to set up the Apache Web server: 1. The machine''s network is congured properly. For more information about this topic, refer to Chapter 16, Basic Networking. 2. The machine''s exact system time is maintained by synchronizing with a time server. This is necessary because parts of the HTTP protocol depend on the correct time. See Chapter 25, Time Synchronization with NTP to learn more about this topic. 3. The latest security updates are installed. If in doubt, run a YaST Online Update. 4. The default Web server port ( 80 ) is opened in the rewall. For this, congure the SuSEFirewall2 to allow the service HTTP Server in the external zone. This can be done using YaST. See Book “Security Guide”, Chapter 15 “Masquerading and Firewalls”, Section 15.4.1 “Configuring the Firewall with YaST” for details. 444 Quick Start SLES 12 SP432.1.2 Installation Apache on SUSE Linux Enterprise Server is not installed by default. To install it with a standard, predened conguration that runs “out of the box”, proceed as follows: PROCEDURE 32.1: INSTALLING APACHE WITH THE DEFAULT CONFIGURATION 1. Start YaST and select Software Software Management. 2. Choose View Patterns and select Web and LAMP Server. 3. Conrm the installation of the dependent packages to nish the installation process. 32.1.3 Start You can start Apache automatically at boot time or start it manually. To make sure that Apache is automatically started during boot in the targets multi- user.target and graphical.target , execute the following command: root # systemctl enable apache2 For more information about the systemd targets in SUSE Linux Enterprise Server and a description of the YaST Services Manager, refer to Section 13.4, “Managing Services with YaST”. To manually start Apache using the shell, run systemctl start apache2 . PROCEDURE 32.2: CHECKING IF APACHE IS RUNNING If you do not receive error messages when starting Apache, this usually indicates that the Web server is running. To test this: 1. Start a browser and open http://localhost/ . If Apache is up and running, you get a test page stating “It works!”. 2. If you do not see this page, refer to Section 32.9, “Troubleshooting”. Now that the Web server is running, you can add your own documents, adjust the conguration according to your needs, or add functionality by installing modules. 445 Installation SLES 12 SP432.2 Configuring Apache SUSE Linux Enterprise Server oers two conguration options: Configuring Apache Manually Configuring Apache with YaST Manual conguration oers a higher level of detail, but lacks the convenience of the YaST GUI. Important: Reload or Restart Apache after Configuration Changes Most conguration changes require a reload (some also a restart) of Apache to take eect. Manually reload Apache with systemctl reload apache2 or use one of the restart options as described in Section 32.3, “Starting and Stopping Apache”. If you congure Apache with YaST, this can be taken care of automatically if you set HTTP Service to Enabled as described in Section 32.2.3.2, “HTTP Server Configuration”. 32.2.1 Apache Configuration Files This section gives an overview of the Apache conguration les. If you use YaST for conguration, you do not need to touch these les—however, the information might be useful for you if you want to switch to manual conguration later on. Apache conguration les can be found in two dierent locations: /etc/sysconfig/apache2 /etc/apache2/ 32.2.1.1 /etc/sysconfig/apache2 /etc/sysconfig/apache2 controls some global settings of Apache, like modules to load, additional conguration les to include, ags with which the server should be started, and ags that should be added to the command line. Every conguration option in this le is extensively documented and therefore not mentioned here. For a general-purpose Web server, the settings in /etc/sysconfig/apache2 should be sucient for any conguration needs. 446 Configuring Apache SLES 12 SP432.2.1.2 /etc/apache2/ /etc/apache2/ hosts all conguration les for Apache. In the following, the purpose of each le is explained. Each le includes several conguration options (also called directives). Every conguration option in these les is extensively documented and therefore not mentioned here. The Apache conguration les are organized as follows: /etc/apache2/ | |- charset.conv |- conf.d/ | | | |- *.conf | |- default-server.conf |- errors.conf |- httpd.conf |- listen.conf |- magic |- mime.types |- mod_*.conf |- server-tuning.conf |- ssl.* |- ssl-global.conf |- sysconfig.d | | | |- global.conf | |- include.conf | |- loadmodule.conf . . | |- uid.conf |- vhosts.d | |- *.conf APACHE CONFIGURATION FILES IN /ETC/APACHE2/ charset.conv Species which character sets to use for dierent languages. Do not edit this le. conf.d/*.conf Conguration les added by other modules. These conguration les can be included into your virtual host conguration where needed. See vhosts.d/vhost.template for examples. By doing so, you can provide dierent module sets for dierent virtual hosts. default-server.conf 447 Apache Configuration Files SLES 12 SP4Global conguration for all virtual hosts with reasonable defaults. Instead of changing the values, overwrite them with a virtual host conguration. errors.conf Denes how Apache responds to errors. To customize these messages for all virtual hosts, edit this le. Otherwise overwrite these directives in your virtual host congurations. httpd.conf The main Apache server conguration le. Avoid changing this le. It primarily contains include statements and global settings. Overwrite global settings in the pertinent conguration les listed here. Change host-specic settings (such as document root) in your virtual host conguration. listen.conf Binds Apache to specic IP addresses and ports. Name-based virtual hosting is also congured here. For details, see Section 32.2.2.1.1, “Name-Based Virtual Hosts”. magic Data for the mime_magic module that helps Apache automatically determine the MIME type of an unknown le. Do not change this le. mime.types MIME types known by the system (this actually is a link to /etc/mime.types ). Do not edit this le. If you need to add MIME types not listed here, add them to mod_mime- defaults.conf . mod_*.conf Conguration les for the modules that are installed by default. Refer to Section  32.4, “Installing, Activating, and Configuring Modules” for details. Note that conguration les for optional modules reside in the directory conf.d . server-tuning.conf Contains conguration directives for the dierent MPMs (see Section 32.4.4, “Multiprocessing Modules”) and general conguration options that control Apache''s performance. Properly test your Web server when making changes here. ssl-global.conf and ssl.* Global SSL conguration and SSL certicate data. Refer to Section 32.6, “Setting Up a Secure Web Server with SSL” for details. sysconfig.d/*.conf 448 Apache Configuration Files SLES 12 SP4Conguration les automatically generated from /etc/sysconfig/apache2 . Do not change any of these les—edit /etc/sysconfig/apache2 instead. Do not put other conguration les in this directory. uid.conf Species under which user and group ID Apache runs. Do not change this le. vhosts.d/*.conf Your virtual host conguration should be located here. The directory contains template les for virtual hosts with and without SSL. Every le in this directory ending with .conf is automatically included in the Apache conguration. Refer to Section 32.2.2.1, “Virtual Host Configuration” for details. 32.2.2 Configuring Apache Manually Conguring Apache manually involves editing plain text conguration les as user root . 32.2.2.1 Virtual Host Configuration The term virtual host refers to Apache''s ability to serve multiple universal resource identiers (URIs) from the same physical machine. This means that several domains, such as www.example.com and www.example.net, are run by a single Web server on one physical machine. It is common practice to use virtual hosts to save administrative eort (only a single Web server needs to be maintained) and hardware expenses (each domain does not require a dedicated server). Virtual hosts can be name based, IP based, or port based. To list all existing virtual hosts, use the command apache2ctl -S . This outputs a list showing the default server and all virtual hosts together with their IP addresses and listening ports. Furthermore, the list also contains an entry for each virtual host showing its location in the conguration les. Virtual hosts can be congured via YaST as described in Section 32.2.3.1.4, “Virtual Hosts” or by manually editing a conguration le. By default, Apache in SUSE Linux Enterprise Server is prepared for one conguration le per virtual host in /etc/apache2/vhosts.d/ . All les in this directory with the extension .conf are automatically included to the conguration. A basic template for a virtual host is provided in this directory ( vhost.template or vhost- ssl.template for a virtual host with SSL support). 449 Configuring Apache Manually SLES 12 SP4Tip: Always Create a Virtual Host Configuration It is recommended to always create a virtual host conguration le, even if your Web server only hosts one domain. By doing so, you not only have the domain-specic conguration in one le, but you can always fall back to a working basic conguration by simply moving, deleting, or renaming the conguration le for the virtual host. For the same reason, you should also create separate conguration les for each virtual host. When using name-based virtual hosts it is recommended to set up a default conguration that will be used when a domain name does not match a virtual host conguration. The default virtual host is the one whose conguration is loaded rst. Since the order of the conguration les is determined by le name, start the le name of the default virtual host conguration with an underscore character ( _ ) to make sure it is loaded rst (for example: _default_vhost.conf ). The block holds the information that applies to a particular domain. When Apache receives a client request for a dened virtual host, it uses the directives enclosed in this section. Almost all directives can be used in a virtual host context. See http:// httpd.apache.org/docs/2.4/mod/quickreference.html for further information about Apache''s conguration directives. 32.2.2.1.1 Name-Based Virtual Hosts With name-based virtual hosts, more than one Web site is served per IP address. Apache uses the host eld in the HTTP header that is sent by the client to connect the request to a matching ServerName entry of one of the virtual host declarations. If no matching ServerName is found, the rst specied virtual host is used as a default. The rst step is to create a block for each dierent name-based host that you want to serve. Inside each block, you will need at minimum a ServerName directive to designate which host is served and a DocumentRoot directive to show where in the le system the content for that host resides. EXAMPLE 32.1: BASIC EXAMPLES OF NAME-BASED VirtualHost ENTRIES # This first-listed virtual host is also the default for *:80 ServerName www.example.com ServerAlias example.com DocumentRoot /srv/www/htdocs/domain 450 Configuring Apache Manually SLES 12 SP4 ServerName other.example.com DocumentRoot /srv/www/htdocs/otherdomain The opening VirtualHost tag takes the IP address (or fully qualied domain name) as an argument in a name-based virtual host conguration. A port number directive is optional. The wild card * is also allowed as a substitute for the IP address. When using IPv6 addresses, the address must be included in square brackets. EXAMPLE 32.2: NAME-BASED VirtualHost DIRECTIVES ... ... ... ... ... 32.2.2.1.2 IP-Based Virtual Hosts This alternative virtual host conguration requires the setup of multiple IPs for a machine. One instance of Apache hosts several domains, each of which is assigned a dierent IP. The physical server must have one IP address for each IP-based virtual host. If the machine does not have multiple network cards, virtual network interfaces (IP aliasing) can also be used. The following example shows Apache running on a machine with the IP 192.168.3.100 , hosting two domains on the additional IPs 192.168.3.101 and 192.168.3.102 . A separate VirtualHost block is needed for every virtual server. 451 Configuring Apache Manually SLES 12 SP4EXAMPLE 32.3: IP-BASED VirtualHost DIRECTIVES ... ... Here, VirtualHost directives are only specied for interfaces other than 192.168.3.100 . When a Listen directive is also congured for 192.168.3.100 , a separate IP-based virtual host must be created to answer HTTP requests to that interface—otherwise the directives found in the default server conguration ( /etc/apache2/default-server.conf ) are applied. 32.2.2.1.3 Basic Virtual Host Configuration At least the following directives should be in each virtual host conguration to set up a virtual host. See /etc/apache2/vhosts.d/vhost.template for more options. ServerName The fully qualied domain name under which the host should be addressed. DocumentRoot Path to the directory from which Apache should serve les for this host. For security reasons, access to the entire le system is forbidden by default, so you must explicitly unlock this directory within a Directory container. ServerAdmin E-mail address of the server administrator. This address is, for example, shown on error pages Apache creates. ErrorLog The error log le for this virtual host. Although it is not necessary to create separate error log les for each virtual host, it is common practice to do so, because it makes the debugging of errors much easier. /var/log/apache2/ is the default directory for Apache''s log les. CustomLog 452 Configuring Apache Manually SLES 12 SP4The access log le for this virtual host. Although it is not necessary to create separate access log les for each virtual host, it is common practice to do so, because it allows the separate analysis of access statistics for each host. /var/log/apache2/ is the default directory for Apache''s log les. As mentioned above, access to the whole le system is forbidden by default for security reasons. Therefore, explicitly unlock the directories in which you have placed the les Apache should serve—for example the DocumentRoot : Require all granted Note: Require all granted In previous versions of Apache, the statement Require all granted was expressed as: Order allow,deny Allow from all This old syntax is still supported by the mod_access_compat module. The complete conguration le looks like this: EXAMPLE 32.4: BASIC VirtualHost CONFIGURATION ServerName www.example.com DocumentRoot /srv/www/www.example.com/htdocs ServerAdmin webmaster@example.com ErrorLog /var/log/apache2/www.example.com_log CustomLog /var/log/apache2/www.example.com-access_log common Require all granted 453 Configuring Apache Manually SLES 12 SP4 32.2.3 Configuring Apache with YaST To congure your Web server with YaST, start YaST and select Network Services HTTP Server. When starting the module for the rst time, the HTTP Server Wizard starts, prompting you to make a few basic decisions concerning administration of the server. After having nished the wizard, the HTTP Server Conguration dialog starts each time you call the HTTP Server module. For more information, see Section 32.2.3.2, “HTTP Server Configuration”. 32.2.3.1 HTTP Server Wizard The HTTP Server Wizard consists of ve steps. In the last step of the dialog, you may enter the expert conguration mode to make even more specic settings. 32.2.3.1.1 Network Device Selection Here, specify the network interfaces and ports Apache uses to listen for incoming requests. You can select any combination of existing network interfaces and their respective IP addresses. Ports from all three ranges (well-known ports, registered ports, and dynamic or private ports) that are not reserved by other services can be used. The default setting is to listen on all network interfaces (IP addresses) on port 80 . Check Open Port In Firewall to open the ports in the rewall that the Web server listens on. This is necessary to make the Web server available on the network, which can be a LAN, WAN, or the public Internet. Keeping the port closed is only useful in test situations where no external access to the Web server is necessary. If you have multiple network interfaces, click Firewall Details to specify on which interface(s) the port(s) should be opened. Click Next to continue with the conguration. 32.2.3.1.2 Modules The Modules conguration option allows for the activation or deactivation of the script languages that the Web server should support. For the activation or deactivation of other modules, refer to Section 32.2.3.2.2, “Server Modules”. Click Next to advance to the next dialog. 454 Configuring Apache with YaST SLES 12 SP432.2.3.1.3 Default Host This option pertains to the default Web server. As explained in Section  32.2.2.1, “Virtual Host Configuration”, Apache can serve multiple virtual hosts from a single physical machine. The rst declared virtual host in the conguration le is commonly called the default host. Each virtual host inherits the default host''s conguration. To edit the host settings (also called directives), select the appropriate entry in the table then click Edit. To add new directives, click Add. To delete a directive, select it and click Delete. FIGURE 32.1: HTTP SERVER WIZARD: DEFAULT HOST Here is list of the default settings of the server: Document Root Path to the directory from which Apache serves les for this host. /srv/www/htdocs is the default location. Alias Using Alias directives, URLs can be mapped to physical le system locations. This means that a certain path even outside the Document Root in the le system can be accessed via a URL aliasing that path. The default SUSE Linux Enterprise Server Alias /icons points to /usr/share/apache2/ icons for the Apache icons displayed in the directory index view. 455 Configuring Apache with YaST SLES 12 SP4ScriptAlias Similar to the Alias directive, the ScriptAlias directive maps a URL to a le system location. The dierence is that ScriptAlias designates the target directory as a CGI location, meaning that CGI scripts should be executed in that location. Directory With Directory settings, you can enclose a group of conguration options that will only apply to the specied directory. Access and display options for the directories /srv/www/htdocs , /usr/share/apache2/ icons and /srv/www/cgi-bin are congured here. It should not be necessary to change the defaults. Include With include, additional conguration les can be specied. Two Include directives are already precongured: /etc/apache2/conf.d/ is the directory containing the conguration les that come with external modules. With this directive, all les in this directory ending in .conf are included. With the second directive, /etc/apache2/ conf.d/apache2-manual.conf , the apache2-manual conguration le is included. Server Name This species the default URL used by clients to contact the Web server. Use a fully qualied domain name (FQDN) to reach the Web server at http://FQDN/ or its IP address. You cannot choose an arbitrary name here—the server must be “known” under this name. Server Administrator E-Mail E-mail address of the server administrator. This address is, for example, shown on error pages Apache creates. After nishing with the Default Host step, click Next to continue with the conguration. 32.2.3.1.4 Virtual Hosts In this step, the wizard displays a list of already congured virtual hosts (see Section 32.2.2.1, “Virtual Host Configuration”). If you have not made manual changes prior to starting the YaST HTTP wizard, no virtual host is present. To add a host, click Add to open a dialog in which to enter basic information about the host, such as Server Name, Server Contents Root ( DocumentRoot ), and the Administrator E-Mail. Server Resolution is used to determine how a host is identied (name based or IP based). Specify the name or IP address with Change Virtual Host ID 456 Configuring Apache with YaST SLES 12 SP4Clicking Next advances to the second part of the virtual host conguration dialog. In part two of the virtual host conguration you can specify whether to enable CGI scripts and which directory to use for these scripts. It is also possible to enable SSL. If you do so, you must specify the path to the certicate as well. See Section 32.6.2, “Configuring Apache with SSL” for details on SSL and certicates. With the Directory Index option, you can specify which le to display when the client requests a directory (by default, index.html ). Add one or more le names (space-separated) to change this. With Enable Public HTML, the content of the users public directories ( ~USER/public_html/ ) is made available on the server under http:// www.example.com/~USER . Important: Creating Virtual Hosts It is not possible to add virtual hosts at will. If using name-based virtual hosts, each host name must be resolved on the network. If using IP-based virtual hosts, you can assign only one host to each IP address available. 32.2.3.1.5 Summary This is the nal step of the wizard. Here, determine how and when the Apache server is started: when booting or manually. Also see a short summary of the conguration made so far. If you are satised with your settings, click Finish to complete conguration. To change something, click Back until you have reached the desired dialog. Clicking HTTP Server Expert Conguration opens the dialog described in Section 32.2.3.2, “HTTP Server Configuration”. 457 Configuring Apache with YaST SLES 12 SP4FIGURE 32.2: HTTP SERVER WIZARD: SUMMARY 32.2.3.2 HTTP Server Configuration The HTTP Server Conguration dialog also lets you make even more adjustments to the conguration than the wizard (which only runs if you congure your Web server for the rst time). It consists of four tabs described in the following. No conguration option you change here is eective immediately—you always must conrm your changes with Finish to make them eective. Clicking Abort leaves the conguration module and discards your changes. 32.2.3.2.1 Listen Ports and Addresses In HTTP Service, select whether Apache should be running (Enabled) or stopped (Disabled). In Listen on Ports, Add, Edit, or Delete addresses and ports on which the server should be available. The default is to listen on all interfaces on port 80 . You should always check Open Port In Firewall, because otherwise the Web server is not reachable from outside. Keeping the port closed is only useful in test situations where no external access to the Web server is necessary. If you have multiple network interfaces, click Firewall Details to specify on which interface(s) the port(s) should be opened. 458 Configuring Apache with YaST SLES 12 SP4With Log Files, watch either the access log le or the error log le. This is useful if you want to test your conguration. The log le opens in a separate window from which you can also restart or reload the Web server. For details, see Section 32.3, “Starting and Stopping Apache”. These commands are eective immediately and their log messages are also displayed immediately. FIGURE 32.3: HTTP SERVER CONFIGURATION: LISTEN PORTS AND ADDRESSES 32.2.3.2.2 Server Modules You can change the status (enabled or disabled) of Apache2 modules by clicking Toggle Status. Click Add Module to add a new module that is already installed but not yet listed. Learn more about modules in Section 32.4, “Installing, Activating, and Configuring Modules”. 459 Configuring Apache with YaST SLES 12 SP4FIGURE 32.4: HTTP SERVER CONFIGURATION: SERVER MODULES 32.2.3.2.3 Main Host or Hosts These dialogs are identical to the ones already described. Refer to Section 32.2.3.1.3, “Default Host” and Section 32.2.3.1.4, “Virtual Hosts”. 32.3 Starting and Stopping Apache If congured with YaST as described in Section 32.2.3, “Configuring Apache with YaST”, Apache is started at boot time in the multi-user.target and graphical.target . You can change this behavior using YaST''s Services Manager or with the systemctl command line tool ( systemctl enable or systemctl disable ). To start, stop, or manipulate Apache on a running system, use either the systemctl or the apachectl commands as described below. For general information about systemctl commands, refer to Section 13.2.1, “Managing Services in a Running System”. systemctl status apache2 460 Starting and Stopping Apache SLES 12 SP4Checks if Apache is started. systemctl start apache2 Starts Apache if it is not already running. systemctl stop apache2 Stops Apache by terminating the parent process. systemctl restart apache2 Stops and then restarts Apache. Starts the Web server if it was not running before. systemctl try-restart apache2 Stops then restarts Apache only if it is already running. systemctl reload apache2 Stops the Web server by advising all forked Apache processes to rst nish their requests before shutting down. As each process dies, it is replaced by a newly started one, resulting in a complete “restart” of Apache. Tip: Restarting Apache in Production Environments This command allows activating changes in the Apache conguration without causing connection break-os. systemctl stop apache2 Stops the Web server after a dened period of time congured with GracefulShutdownTimeout to ensure that existing requests can be nished. apachectl configtest Checks the syntax of the conguration les without aecting a running Web server. Because this check is forced every time the server is started, reloaded, or restarted, it is usually not necessary to run the test explicitly (if a conguration error is found, the Web server is not started, reloaded, or restarted). apachectl status and apachectl fullstatus Dumps a short or full status screen, respectively. Requires the module mod_status to be enabled and a text-based browser (such as links or w3m ) installed. In addition to that, status must be added to APACHE_SERVER_FLAGS in the le /etc/sysconfig/apache2 . 461 Starting and Stopping Apache SLES 12 SP4Tip: Additional Flags If you specify additional ags to the commands, these are passed through to the Web server. 32.4 Installing, Activating, and Configuring Modules The Apache software is built in a modular fashion: all functionality except some core tasks are handled by modules. This has progressed so far that even HTTP is processed by a module ( http_core ). Apache modules can be compiled into the Apache binary at build time or be dynamically loaded at runtime. Refer to Section 32.4.2, “Activation and Deactivation” for details of how to load modules dynamically. Apache modules can be divided into four dierent categories: Base Modules Base modules are compiled into Apache by default. Apache in SUSE Linux Enterprise Server has only mod_so (needed to load other modules) and http_core compiled in. All others are available as shared objects: rather than being included in the server binary itself, they can be included at runtime. Extension Modules In general, modules labeled as extensions are included in the Apache software package, but are usually not compiled into the server statically. In SUSE Linux Enterprise Server, they are available as shared objects that can be loaded into Apache at runtime. External Modules Modules labeled external are not included in the ocial Apache distribution. However, SUSE Linux Enterprise Server provides several of them. Multiprocessing Modules (MPMs) MPMs are responsible for accepting and handling requests to the Web server, representing the core of the Web server software. 462 Installing, Activating, and Configuring Modules SLES 12 SP432.4.1 Module Installation If you have done a default installation as described in Section 32.1.2, “Installation”, the following modules are already installed: all base and extension modules, the multiprocessing module Prefork MPM, and the external module mod_python . You can install additional external modules by starting YaST and choosing Software Software Management. Now choose View Search and search for apache. Among other packages, the results list contains all available external Apache modules. 32.4.2 Activation and Deactivation Activate or deactivate particular modules either manually or with YaST. In YaST, script language modules (PHP5, Perl, and Python) need to be enabled or disabled with the module conguration described in Section 32.2.3.1, “HTTP Server Wizard”. All other modules can be enabled or disabled as described in Section 32.2.3.2.2, “Server Modules”. If you prefer to activate or deactivate the modules manually, use the commands a2enmod MODULE or a2dismod MODULE , respectively. a2enmod -l outputs a list of all currently active modules. Important: Including Configuration Files for External Modules If you have activated external modules manually, make sure to load their conguration les in all virtual host congurations. Conguration les for external modules are located under /etc/apache2/conf.d/ and are loaded in /etc/apache2/default- server.conf by default. For more ne-grained control you can comment out the inclusion in /etc/apache2/default-server.conf and add it to specic virtual hosts only. See /etc/apache2/vhosts.d/vhost.template for examples. 32.4.3 Base and Extension Modules All base and extension modules are described in detail in the Apache documentation. Only a brief description of the most important modules is available here. Refer to http://httpd.apache.org/ docs/2.4/mod/ to learn details about each module. mod_actions 463 Module Installation SLES 12 SP4Provides methods to execute a script whenever a certain MIME type (such as application/pdf ), a le with a specic extension (like .rpm ), or a certain request method (such as GET ) is requested. This module is enabled by default. mod_alias Provides Alias and Redirect directives with which you can map a URl to a specic directory ( Alias ) or redirect a requested URL to another location. This module is enabled by default. mod_auth* The authentication modules provide dierent authentication methods: basic authentication with mod_auth_basic or digest authentication with mod_auth_digest . mod_auth_basic and mod_auth_digest must be combined with an authentication provider module, mod_authn_* (for example, mod_authn_file for text le–based authentication) and with an authorization module mod_authz_* (for example, mod_authz_user for user authorization). More information about this topic is available in the Authentication HOWTO at http:// httpd.apache.org/docs/2.4/howto/auth.html . mod_autoindex Autoindex generates directory listings when no index le (for example, index.html ) is present. The look and feel of these indexes is congurable. This module is enabled by default. However, directory listings are disabled by default via the Options directive— overwrite this setting in your virtual host conguration. The default conguration le for this module is located at /etc/apache2/mod_autoindex-defaults.conf . mod_cgi mod_cgi is needed to execute CGI scripts. This module is enabled by default. mod_deflate Using this module, Apache can be congured to compress given le types on the y before delivering them. mod_dir mod_dir provides the DirectoryIndex directive with which you can congure which les are automatically delivered when a directory is requested ( index.html by default). It also provides an automatic redirect to the correct URL when a directory request does not contain a trailing slash. This module is enabled by default. mod_env 464 Base and Extension Modules SLES 12 SP4Controls the environment that is passed to CGI scripts or SSI pages. Environment variables can be set or unset or passed from the shell that invoked the httpd process. This module is enabled by default. mod_expires With mod_expires , you can control how often proxy and browser caches refresh your documents by sending an Expires header. This module is enabled by default. mod_http2 With mod_http2 , Apache gains support for the HTTP/2 protocol. It can be enabled by specifying Protocols h2 http/1.1 in a VirtualHost . mod_include mod_include lets you use Server Side Includes (SSI), which provide a basic functionality to generate HTML pages dynamically. This module is enabled by default. mod_info Provides a comprehensive overview of the server conguration under http://localhost/ server-info/. For security reasons, you should always limit access to this URL. By default only localhost is allowed to access this URL. mod_info is congured at /etc/apache2/ mod_info.conf . mod_log_config With this module, you can congure the look of the Apache log les. This module is enabled by default. mod_mime The mime module ensures that a le is delivered with the correct MIME header based on the le name''s extension (for example text/html for HTML documents). This module is enabled by default. mod_negotiation Necessary for content negotiation. See http://httpd.apache.org/docs/2.4/content- negotiation.html for more information. This module is enabled by default. mod_rewrite Provides the functionality of mod_alias , but oers more features and exibility. With mod_rewrite , you can redirect URLs based on multiple rules, request headers, and more. mod_setenvif 465 Base and Extension Modules SLES 12 SP4Sets environment variables based on details of the client''s request, such as the browser string the client sends, or the client''s IP address. This module is enabled by default. mod_spelling mod_spelling attempts to automatically correct typographical errors in URLs, such as capitalization errors. mod_ssl Enables encrypted connections between Web server and clients. See Section 32.6, “Setting Up a Secure Web Server with SSL” for details. This module is enabled by default. mod_status Provides information on server activity and performance under http://localhost/server- status/. For security reasons, you should always limit access to this URL. By default, only localhost is allowed to access this URL. mod_status is congured at /etc/apache2/ mod_status.conf . mod_suexec mod_suexec lets you run CGI scripts under a dierent user and group. This module is enabled by default. mod_userdir Enables user-specic directories available under ~USER/ . The UserDir directive must be specied in the conguration. This module is enabled by default. 32.4.4 Multiprocessing Modules SUSE Linux Enterprise Server provides two dierent multiprocessing modules (MPMs) for use with Apache: Prefork MPM Worker MPM 32.4.4.1 Prefork MPM The prefork MPM implements a non-threaded, preforking Web server. It makes the Web server behave similarly to Apache version 1.x. In this version it isolates each request and handles it by forking a separate child process. Thus problematic requests cannot aect others, avoiding a lockup of the Web server. 466 Multiprocessing Modules SLES 12 SP4While providing stability with this process-based approach, the prefork MPM consumes more system resources than its counterpart, the worker MPM. The prefork MPM is considered the default MPM for Unix-based operating systems. Important: MPMs in This Document This document assumes Apache is used with the prefork MPM. 32.4.4.2 Worker MPM The worker MPM provides a multi-threaded Web server. A thread is a “lighter” form of a process. The advantage of a thread over a process is its lower resource consumption. Instead of only forking child processes, the worker MPM serves requests by using threads with server processes. The preforked child processes are multi-threaded. This approach makes Apache perform better by consuming fewer system resources than the prefork MPM. One major disadvantage is the stability of the worker MPM: if a thread becomes corrupt, all threads of a process can be aected. In the worst case, this may result in a server crash. Especially when using the Common Gateway Interface (CGI) with Apache under heavy load, internal server errors might occur because of threads being unable to communicate with system resources. Another argument against using the worker MPM with Apache is that not all available Apache modules are thread-safe and thus cannot be used with the worker MPM. Warning: Using PHP Modules with MPMs Not all available PHP modules are thread-safe. Using the worker MPM with mod_php is strongly discouraged. 32.4.5 External Modules Find a list of all external modules shipped with SUSE Linux Enterprise Server here. Find the module''s documentation in the listed directory. mod_apparmor Adds support to Apache to provide AppArmor connement to individual CGI scripts handled by modules like mod_php5 and mod_perl . 467 External Modules SLES 12 SP4Package Name: apache2-mod_apparmor More Information: Book “Security Guide” mod_perl mod_perl enables you to run Perl scripts in an embedded interpreter. The persistent interpreter embedded in the server avoids the overhead of starting an external interpreter and the penalty of Perl start-up time. Package Name: apache2-mod_perl Conguration File: /etc/apache2/conf.d/mod_perl.conf More Information: /usr/share/doc/packages/apache2-mod_perl mod_php5 PHP is a server-side, cross-platform HTML embedded scripting language. Package Name: apache2-mod_php5 Conguration File: /etc/apache2/conf.d/php5.conf More Information: /usr/share/doc/packages/apache2-mod_php5 mod_python mod_python allows embedding Python within the Apache HTTP server for a considerable boost in performance and added exibility in designing Web-based applications. Package Name: apache2-mod_python More Information: /usr/share/doc/packages/apache2-mod_python mod_security mod_security provides a Web application rewall to protect Web applications from a range of attacks. It also enables HTTP trac monitoring and real-time analysis. Package Name: apache2-mod_security2 Conguration File: /etc/apache2/conf.d/mod_security2.conf More Information: /usr/share/doc/packages/apache2-mod_security2 Documentation: http://modsecurity.org/documentation/ 468 External Modules SLES 12 SP432.4.6 Compilation Apache can be extended by advanced users by writing custom modules. To develop modules for Apache or compile third-party modules, the package apache2-devel is required along with the corresponding development tools. apache2-devel also contains the apxs2 tools, which are necessary for compiling additional modules for Apache. apxs2 enables the compilation and installation of modules from source code (including the required changes to the conguration les), which creates dynamic shared objects (DSOs) that can be loaded into Apache at runtime. The apxs2 binaries are located under /usr/sbin : /usr/sbin/apxs2—suitable for building an extension module that works with any MPM. The installation location is /usr/lib64/apache2 . /usr/sbin/apxs2-prefork—suitable for prefork MPM modules. The installation location is /usr/lib64/apache2-prefork . /usr/sbin/apxs2-worker—suitable for worker MPM modules. The installation location is /usr/lib64/apache2-worker . Install and activate a module from source code with the following commands: cd /path/to/module/source apxs2 -cia MODULE.c where -c compiles the module, -i installs it, and -a activates it. Other options of apxs2 are described in the apxs2(1) man page. 32.5 Enabling CGI Scripts Apache''s Common Gateway Interface (CGI) lets you create dynamic content with programs or scripts usually called CGI scripts. CGI scripts can be written in any programming language. Usually, script languages such as Perl or PHP are used. To enable Apache to deliver content created by CGI scripts, mod_cgi needs to be activated. mod_alias is also needed. Both modules are enabled by default. Refer to Section 32.4.2, “Activation and Deactivation” for details on activating modules. 469 Compilation SLES 12 SP4Warning: CGI Security Allowing the server to execute CGI scripts is a potential security hole. Refer to Section 32.8, “Avoiding Security Problems” for additional information. 32.5.1 Apache Configuration In SUSE Linux Enterprise Server, the execution of CGI scripts is only allowed in the directory /srv/www/cgi-bin/ . This location is already congured to execute CGI scripts. If you have created a virtual host conguration (see Section 32.2.2.1, “Virtual Host Configuration”) and want to place your scripts in a host-specic directory, you must unlock and congure this directory. EXAMPLE 32.5: VIRTUALHOST CGI CONFIGURATION ScriptAlias /cgi-bin/ "/srv/www/www.example.com/cgi-bin/" 1 Options +ExecCGI 2 AddHandler cgi-script .cgi .pl 3 Require all granted 4 1 Tells Apache to handle all les within this directory as CGI scripts. 2 Enables CGI script execution 3 Tells the server to treat les with the extensions .pl and .cgi as CGI scripts. Adjust according to your needs. 4 The Require directive controls the default access state. In this case, access is granted to the specied directory without limitation. For more information on authentication and authorization, see http://httpd.apache.org/docs/2.4/howto/auth.html . 32.5.2 Running an Example Script CGI programming diers from "regular" programming in that the CGI programs and scripts must be preceded by a MIME-Type header such as Content-type: text/html . This header is sent to the client, so it understands what kind of content it receives. Secondly, the script''s output must be something the client, usually a Web browser, understands—HTML usually, or plain text or images, for example. 470 Apache Configuration SLES 12 SP4A simple test script available under /usr/share/doc/packages/apache2/test-cgi is part of the Apache package. It outputs the content of some environment variables as plain text. Copy this script to either /srv/www/cgi-bin/ or the script directory of your virtual host ( /srv/ www/www.example.com/cgi-bin/ ) and name it test.cgi . Edit the le to have #!/bin/sh as the rst line. Files accessible by the Web server should be owned by the user root . For additional information see Section 32.8, “Avoiding Security Problems”. Because the Web server runs with a dierent user, the CGI scripts must be world-executable and world-readable. Change into the CGI directory and use the command chmod 755 test.cgi to apply the proper permissions. Now call http://localhost/cgi-bin/test.cgi or http://www.example.com/cgi-bin/ test.cgi . You should see the “CGI/1.0 test script report”. 32.5.3 CGI Troubleshooting If you do not see the output of the test program but an error message instead, check the following: CGI TROUBLESHOOTING Have you reloaded the server after having changed the conguration? If not, reload with systemctl reload apache2 If you have congured your custom CGI directory, is it congured properly? If in doubt, try the script within the default CGI directory /srv/www/cgi-bin/ and call it with http:// localhost/cgi-bin/test.cgi . Are the le permissions correct? Change into the CGI directory and execute ls -l test.cgi . The output should start with -rwxr-xr-x 1 root root Make sure that the script does not contain programming errors. If you have not changed test.cgi , this should not be the case, but if you are using your own programs, always make sure that they do not contain programming errors. 471 CGI Troubleshooting SLES 12 SP432.6 Setting Up a Secure Web Server with SSL Whenever sensitive data, such as credit card information, is transferred between Web server and client, it is desirable to have a secure, encrypted connection with authentication. mod_ssl provides strong encryption using the secure sockets layer (SSL) and transport layer security (TLS) protocols for HTTP communication between a client and the Web server. Using SSL/TLS, a private connection between Web server and client is established. Data integrity is ensured and client and server can authenticate each other. For this purpose, the server sends an SSL certicate that holds information proving the server''s valid identity before any request to a URL is answered. In turn, this guarantees that the server is the uniquely correct end point for the communication. Additionally, the certicate generates an encrypted connection between client and server that can transport information without the risk of exposing sensitive, plain-text content. mod_ssl does not implement the SSL/TLS protocols itself, but acts as an interface between Apache and an SSL library. In SUSE Linux Enterprise Server, the OpenSSL library is used. OpenSSL is automatically installed with Apache. The most visible eect of using mod_ssl with Apache is that URLs are prexed with https:// instead of http:// . 32.6.1 Creating an SSL Certificate To use SSL/TLS with the Web server, you need to create an SSL certicate. This certicate is needed for the authorization between Web server and client, so that each party can clearly identify the other party. To ensure the integrity of the certicate, it must be signed by a party every user trusts. There are three types of certicates you can create: a “dummy” certicate for testing purposes only, a self-signed certicate for a dened circle of users that trust you, and a certicate signed by an independent, publicly-known certicate authority (CA). Creating a certicate is a two step process. First, a private key for the certicate authority is generated then the server certicate is signed with this key. Tip: For More Information To learn more about concepts and denitions of SSL/TLS, refer to http://httpd.apache.org/ docs/2.4/ssl/ssl_intro.html . 472 Setting Up a Secure Web Server with SSL SLES 12 SP432.6.1.1 Creating a “Dummy” Certificate To generate a dummy certicate, call the script /usr/bin/gensslcert . It creates or overwrites the les listed below. Use gensslcert ''s optional switches to ne-tune the certicate. Call / usr/bin/gensslcert -h for more information. /etc/apache2/ssl.crt/ca.crt /etc/apache2/ssl.crt/server.crt /etc/apache2/ssl.key/server.key /etc/apache2/ssl.csr/server.csr A copy of ca.crt is also placed at /srv/www/htdocs/CA.crt for download. Important: For Testing Purposes Only A dummy certicate should never be used on a production system. Only use it for testing purposes. 32.6.1.2 Creating a Self-Signed Certificate If you are setting up a secure Web server for an intranet or for a dened circle of users, it is probably sucient if you sign a certicate with your own certicate authority (CA). Note that visitors to such a site will see a warning like “this is an untrusted site”, as Web browsers do not recognize self-signed certicates. Important: Self-Signed Certificates Only use a self-signed certicate on a Web server that is accessed by people who know and trust you as a certicate authority. It is not recommended to use such a certicate for a public shop, for example. First you need to generate a certicate signing request (CSR). You are going to use openssl , with PEM as the certicate format. During this step, you will be asked for a passphrase, and to answer several questions. Remember the passphrase you enter as you will need it in the future. sudo openssl req -new > new.cert.csr Generating a 1024 bit RSA private key ..++++++ 473 Creating an SSL Certificate SLES 12 SP4.........++++++ writing new private key to ''privkey.pem'' Enter PEM pass phrase: 1 Verifying - Enter PEM pass phrase: 2 ----- You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter ''.'', the field will be left blank. ----- Country Name (2 letter code) [AU]: 3 State or Province Name (full name) [Some-State]: 4 Locality Name (eg, city) []: 5 Organization Name (eg, company) [Internet Widgits Pty Ltd]: 6 Organizational Unit Name (eg, section) []: 7 Common Name (for example server FQDN, or YOUR name) []: 8 Email Address []: 9 Please enter the following ''extra'' attributes to be sent with your certificate request A challenge password []: 10 An optional company name []: 11 1 Fill in your passphrase, 2 ...ll it in once more (and remember it). 3 Fill in your 2 letter country code, such as GB or CZ . 4 Fill in the name of the state where you live. 5 Fill in the city name, such as Prague . 6 Fill in the name of the organization you work for. 7 Fill in your organization unit, or leave blank if you have none. 8 Fill in either the domain name of the server, or your rst and last name. 9 Fill in your work e-mail address. 10 Leave the challenge password empty, otherwise you will need to enter it every time you restart the Apache Web server. 11 Fill in the optional company name, or leave blank. Now you can generate the certicate. You are going to use openssl again, and the format of the certicate is the default PEM . 474 Creating an SSL Certificate SLES 12 SP4PROCEDURE 32.3: GENERATING THE CERTIFICATE 1. Export the private part of the key to new.cert.key . You will be prompted for the passphrase you entered when creating the certicate signing request (CSR). sudo openssl rsa -in privkey.pem -out new.cert.key 2. Generate the public part of the certicate according to the information you lled out in the signing request. The -days option species the length of time before the certicate expires. You can revoke a certicate, or replace one before it expires. sudo openssl x509 -in new.cert.csr -out new.cert.cert -req \ -signkey new.cert.key -days 365 3. Copy the certicate les to the relevant directories, so that the Apache server can read them. Make sure that the private key /etc/apache2/ssl.key/server.key is not world- readable, while the public PEM certicate /etc/apache2/ssl.crt/server.crt is. sudo cp new.cert.cert /etc/apache2/ssl.crt/server.crt sudo cp new.cert.key /etc/apache2/ssl.key/server.key Tip: Public Certificate Location The last step is to copy the public certicate le from /etc/apache2/ssl.crt/ server.crt to a location where your users can access it to incorporate it into the list of known and trusted CAs in their Web browsers. Otherwise a browser complains that the certicate was issued by an unknown authority. 32.6.1.3 Getting an Officially Signed Certificate There are several ocial certicate authorities that sign your certicates. The certicate is signed by a trustworthy third party, so can be fully trusted. Publicly operating secure Web servers usually have an ocially signed certicate. A list of the most used Certicate Authorities (CAs) is available at https://en.wikipedia.org/wiki/Certificate_authority#Providers . When requesting an ocially signed certicate, you do not send a certicate to the CA. Instead, issue a Certicate Signing Request (CSR). To create a CSR, run the following command: openssl req -new -newkey rsa:2048 -nodes -keyout newkey.pem -out newreq.pem 475 Creating an SSL Certificate SLES 12 SP4You are asked to enter a distinguished name. This requires you to answer a few questions, such as country name or organization name. Enter valid data—everything you enter here later shows up in the certicate and is checked. You do not need to answer every question. If one does not apply to you or you want to leave it blank, use “.”. Common name is the name of the CA itself—choose a signicant name, such as My company CA. Last, a challenge password and an alternative company name must be entered. Find the CSR in the directory from which you called the script. The le is named newreq.pem . 32.6.2 Configuring Apache with SSL The default port for SSL and TLS requests on the Web server side is 443. There is no conict between a “regular” Apache listening on port 80 and an SSL/TLS-enabled Apache listening on port 443. In fact, HTTP and HTTPS can be run with the same Apache instance. Usually separate virtual hosts are used to dispatch requests to port 80 and port 443 to separate virtual servers. Important: Firewall Configuration Do not forget to open the rewall for SSL-enabled Apache on port 443. This can be done with YaST as described in Book “Security Guide”, Chapter 15 “Masquerading and Firewalls”, Section 15.4.1 “Configuring the Firewall with YaST”. The SSL module is enabled by default in the global server conguration. In case it has been disabled on your host, activate it with the following command: a2enmod ssl . To nally enable SSL, the server needs to be started with the ag “SSL”. To do so, call a2enflag SSL (case- sensitive!). If you have chosen to encrypt your server certicate with a password, you should also increase the value for APACHE_TIMEOUT in /etc/sysconfig/apache2 , so you have enough time to enter the passphrase when Apache starts. Restart the server to make these changes active. A reload is not sucient. The virtual host conguration directory contains a template /etc/apache2/vhosts.d/ vhost-ssl.template with SSL-specic directives that are extensively documented. Refer to Section 32.2.2.1, “Virtual Host Configuration” for the general virtual host conguration. 476 Configuring Apache with SSL SLES 12 SP4To get started, copy the template to /etc/apache2/vhosts.d/MYSSL-HOST.conf and edit it. Adjusting the values for the following directives should be sucient: DocumentRoot ServerName ServerAdmin ErrorLog TransferLog 32.6.2.1 Name-Based Virtual Hosts and SSL By default it is not possible to run multiple SSL-enabled virtual hosts on a server with only one IP address. Name-based virtual hosting requires that Apache knows which server name has been requested. The problem with SSL connections is, that such a request can only be read after the SSL connection has already been established (by using the default virtual host). As a result, users will receive a warning message stating that the certicate does not match the server name. SUSE Linux Enterprise Server comes with an extension to the SSL protocol called Server Name Indication (SNI) addresses this issue by sending the name of the virtual domain as part of the SSL negotiation. This enables the server to “switch” to the correct virtual domain early and present the browser the correct certicate. SNI is enabled by default on SUSE Linux Enterprise Server. To enable Name-Based Virtual Hosts for SSL, congure the server as described in Section 32.2.2.1.1, “Name-Based Virtual Hosts” (note that you need to use port 443 rather than port 80 with SSL). Important: SNI Browser Support SNI must also be supported on the client side. However, SNI is supported by most browsers, except for certain older browsers. For more information, see https:// en.wikipedia.org/wiki/Server_Name_Indication#Support . To congure handling of non-SNI capable browsers, use the directive SSLStrictSNIVHostCheck . When set to on in the server conguration, non-SNI capable browser will be rejected for all virtual hosts. When set to on within a VirtualHost directive, access to this particular host will be rejected. 477 Configuring Apache with SSL SLES 12 SP4When set to off in the server conguration, the server will behave as if not having SNI support. SSL requests will be handled by the rst virtual host dened (for port 443). 32.7 Running Multiple Apache Instances on the Same Server As of SUSE® Linux Enterprise Server 12 SP1, you can run multiple Apache instances on the same server. This has several advantages over running multiple virtual hosts (see Section 32.2.2.1, “Virtual Host Configuration”): When a virtual host needs to be disabled for some time, you need to change the Web server conguration and restart it so that the change takes eect. In case of problems with one virtual host, you need to restart all of them. You can run the default Apache instance as usual: sytemctl start apache2 It reads the default /etc/sysconfig/apache2 le. If the le is not present, or it is present but it does not set the APACHE_HTTPD_CONF variable, it reads /etc/apache2/httpd.conf . To activate another Apache instance, run: systemctl start apache2@INSTANCE_NAME For example: systemctl start apache2@example_web.org By default, the instance uses /etc/apache2@example_web.org/httpd.conf as a main conguration le, which can be overwritten by setting APACHE_HTTPD_CONF in /etc/ sysconfig/apache2@example_web.org . An example to set up an additional instance of Apache follows. Note that you need to execute all the commands as root . 478 Running Multiple Apache Instances on the Same Server SLES 12 SP4PROCEDURE 32.4: CONFIGURING AN ADDITIONAL APACHE INSTANCE 1. Create a new conguration le based on /etc/sysconfig/apache2 , for example /etc/ sysconfig/apache2@example_web.org : cp /etc/sysconfig/apache2 /etc/sysconfig/apache2@example_web.org 2. Edit the le /etc/sysconfig/apache2@example_web.org and change the line containing APACHE_HTTPD_CONF to APACHE_HTTPD_CONF="/etc/apache2/httpd@example_web.org.conf" 3. Create the le /etc/apache2/httpd@example_web.org.conf based on /etc/apache2/ httpd.conf . cp /etc/apache2/httpd.conf /etc/apache2/httpd@example_web.org.conf 4. Edit /etc/apache2/httpd@example_web.org.conf and change Include /etc/apache2/listen.conf to Include /etc/apache2/listen@example_web.org.conf Review all the directives and change them to t your needs. You will probably want to change Include /etc/apache2/global.conf and create new global@example_web.org.conf for each instance. We suggest to change ErrorLog /var/log/apache2/error_log to ErrorLog /var/log/apache2/error@example_web.org_log to have separate logs for each instance. 479 Running Multiple Apache Instances on the Same Server SLES 12 SP45. Create /etc/apache2/listen@example_web.org.conf based on /etc/apache2/ listen.conf . cp /etc/apache2/listen.conf /etc/apache2/listen@example_web.org.conf 6. Edit /etc/apache2/listen@example_web.org.conf and change Listen 80 to the port number you want the new instance to run on, for example 82: Listen 82 To run the new Apache instance over a secured protocol (see Section 32.6, “Setting Up a Secure Web Server with SSL”), change also the line Listen 443 for example to Listen 445 7. Start the new Apache instance: systemctl start apache2@example_web.org 8. Check if the server is running by pointing your Web browser at http://server_name:82 . If you previously changed the name of the error log le for the new instance, you can check it: tail -f /var/log/apache2/error@example_web.org_log Here are several points to consider when setting up more Apache instances on the same server: The le /etc/sysconfig/apache2@INSTANCE_NAME can include the same variables as / etc/sysconfig/apache2 , including module loading and MPM setting. The default Apache instance does not need to be running while other instances run. The Apache helper utilities a2enmod , a2dismod and apachectl operate on the default Apache instance if not specied otherwise with the HTTPD_INSTANCE environment variable. The following example export HTTPD_INSTANCE=example_web.org 480 Running Multiple Apache Instances on the Same Server SLES 12 SP4a2enmod access_compat a2enmod status apachectl start will add access_compat and status modules to the APACHE_MODULES variable of /etc/ sysconfig/apache2@example_web.org , and then start the example_web.org instance. 32.8 Avoiding Security Problems A Web server exposed to the public Internet requires an ongoing administrative eort. It is inevitable that security issues appear, both related to the software and to accidental misconguration. Here are some tips for how to deal with them. 32.8.1 Up-to-Date Software If there are vulnerabilities found in the Apache software, a security advisory will be issued by SUSE. It contains instructions for xing the vulnerabilities, which in turn should be applied when possible. The SUSE security announcements are available from the following locations: Web Page. https://www.suse.com/support/security/ Mailing List Archive. https://lists.opensuse.org/opensuse-security-announce/ List of Security Announcements. https://www.suse.com/support/update/ 32.8.2 DocumentRoot Permissions By default in SUSE Linux Enterprise Server, the DocumentRoot directory /srv/www/htdocs and the CGI directory /srv/www/cgi-bin belong to the user and group root . You should not change these permissions. If the directories are writable for all, any user can place les into them. These les might then be executed by Apache with the permissions of wwwrun , which may give the user unintended access to le system resources. Use subdirectories of /srv/www to place the DocumentRoot and CGI directories for your virtual hosts and make sure that directories and les belong to user and group root . 481 Avoiding Security Problems SLES 12 SP432.8.3 File System Access By default, access to the whole le system is denied in /etc/apache2/httpd.conf . You should never overwrite these directives, but specically enable access to all directories Apache should be able to read. For details, see Section 32.2.2.1.3, “Basic Virtual Host Configuration”. In doing so, ensure that no critical les, such as password or system conguration les, can be read from the outside. 32.8.4 CGI Scripts Interactive scripts in Perl, PHP, SSI, or any other programming language can essentially run arbitrary commands and therefore present a general security issue. Scripts that will be executed from the server should only be installed from sources the server administrator trusts—allowing users to run their own scripts is generally not a good idea. It is also recommended to do security audits for all scripts. To make the administration of scripts as easy as possible, it is common practice to limit the execution of CGI scripts to specic directories instead of globally allowing them. The directives ScriptAlias and Option ExecCGI are used for conguration. The SUSE Linux Enterprise Server default conguration does not allow execution of CGI scripts from everywhere. All CGI scripts run as the same user, so dierent scripts can potentially conict with each other. The module suEXEC lets you run CGI scripts under a dierent user and group. 32.8.5 User Directories When enabling user directories (with mod_userdir or mod_rewrite ) you should strongly consider not allowing .htaccess les, which would allow users to overwrite security settings. At least you should limit the user''s engagement by using the directive AllowOverRide . In SUSE Linux Enterprise Server, .htaccess les are enabled by default, but the user is not allowed to overwrite any Option directives when using mod_userdir (see the /etc/apache2/ mod_userdir.conf conguration le). 482 File System Access SLES 12 SP432.9 Troubleshooting If Apache does not start, the Web page is not accessible, or users cannot connect to the Web server, it is important to nd the cause of the problem. Here are some typical places to look for error explanations and important things to check: Output of the apache2.service subcommand: Instead of starting and stopping the Web server with the binary /usr/sbin/apache2ctl , rather use the systemctl commands instead (described in Section  32.3, “Starting and Stopping Apache”). systemctl status apache2 is verbose about errors, and it even provides tips and hints for xing conguration errors. Log Files and Verbosity In case of both fatal and nonfatal errors, check the Apache log les for causes, mainly the error log le located at /var/log/apache2/error_log by default. Additionally, you can control the verbosity of the logged messages with the LogLevel directive if more detail is needed in the log les. Tip: A Simple Test Watch the Apache log messages with the command tail -F /var/log/apache2/ MY_ERROR_LOG . Then run systemctl restart apache2 . Now, try to connect with a browser and check the output. Firewall and Ports A common mistake is to not open the ports for Apache in the rewall conguration of the server. If you congure Apache with YaST, there is a separate option available to take care of this specic issue (see Section 32.2.3, “Configuring Apache with YaST”). If you are conguring Apache manually, open rewall ports for HTTP and HTTPS via YaST''s rewall module. If the error cannot be tracked down with any of these, check the online Apache bug database at http://httpd.apache.org/bug_report.html . Additionally, the Apache user community can be reached via a mailing list available at http://httpd.apache.org/userslist.html . 483 Troubleshooting SLES 12 SP432.10 For More Information The package apache2-doc contains the complete Apache manual in various localizations for local installation and reference. It is not installed by default—the quickest way to install it is to use the command zypper in apache2-doc . having been installed, the Apache manual is available at http://localhost/manual/ . You may also access it on the Web at http:// httpd.apache.org/docs-2.4/ . SUSE-specic conguration hints are available in the directory / usr/share/doc/packages/apache2/README.* . 32.10.1 Apache 2.4 For a list of new features in Apache 2.4, refer to http://httpd.apache.org/docs/2.4/ new_features_2_4.html . Information about upgrading from version 2.2 to 2.4 is available at http://httpd.apache.org/docs-2.4/upgrading.html . 32.10.2 Apache Modules More information about external Apache modules that are briey described in Section 32.4.5, “External Modules” is available at the following locations: mod_apparmor http://en.opensuse.org/SDB:AppArmor mod_auth_kerb http://modauthkerb.sourceforge.net/ mod_perl http://perl.apache.org/ mod_php5 http://www.php.net/manual/en/install.unix.apache2.php mod_python http://www.modpython.org/ mod_security http://modsecurity.org/ 484 For More Information SLES 12 SP432.10.3 Development More information about developing Apache modules or about getting involved in the Apache Web server project are available at the following locations: Apache Developer Information http://httpd.apache.org/dev/ Apache Developer Documentation http://httpd.apache.org/docs/2.4/developer/ 32.10.4 Miscellaneous Sources If you experience diculties specic to Apache in SUSE Linux Enterprise Server, take a look at the Technical Information Search at https://www.suse.com/support . The history of Apache is provided at https://httpd.apache.org/ABOUT_APACHE.html . This page also explains why the server is called Apache. 485 Development SLES 12 SP433 Setting Up an FTP Server with YaST Using the YaST FTP Server module, you can congure your machine to function as an FTP (File Transfer Protocol) server. Anonymous and/or authenticated users can connect to your machine and download les using the FTP protocol. Depending on the conguration, they can also upload les to the FTP server. YaST uses vsftpd (Very Secure FTP Daemon). If the YaST FTP Server module is not available in your system, install the yast2-ftp-server package. To congure the FTP server using YaST, follow these steps: 1. Open the YaST control center and choose Network Services FTP Server or run the yast2 ftp-server command as root . 2. If there is not any FTP server installed in your system, you will be asked which server to install when the YaST FTP Server module starts. Choose the vsftpd server and conrm the dialog. 3. In the Start-Up dialog, congure the options for starting of the FTP server. For more information, see Section 33.1, “Starting the FTP Server”. In the General dialog, congure FTP directories, welcome message, le creation masks and other parameters. For more information, see Section 33.2, “FTP General Settings”. In the Performance dialog, set the parameters that aect the load on the FTP server. For more information, see Section 33.3, “FTP Performance Settings”. In the Authentication dialog, set whether the FTP server should be available for anonymous and/or authenticated users. For more information, see Section 33.4, “Authentication”. In the Expert Settings dialog, congure the operation mode of the FTP server, SSL connections and rewall settings. For more information, see Section 33.5, “Expert Settings”. 4. Press Finish to save the congurations. 486 SLES 12 SP433.1 Starting the FTP Server In the Service Start frame of the FTP Start-Up dialog set the way the FTP server is started up. You can choose between starting the server automatically during the system boot and starting it manually. If the FTP server should be started only after an FTP connection request, choose Via xinetd. The current status of the FTP server is shown in the Switch On and O frame of the FTP Start-Up dialog. Start the FTP server by clicking Start FTP Now. To stop the server, click Stop FTP Now. After having changed the settings of the server click Save Settings and Restart FTP Now. Your congurations will be saved by leaving the conguration module with Finish. FIGURE 33.1: FTP SERVER CONFIGURATION — START-UP 33.2 FTP General Settings In the General Settings frame of the FTP General Settings dialog you can set the Welcome message which is shown after connecting to the FTP server. If you check the Chroot Everyone option, all local users will be placed in a chroot jail in their home directory after login. This option has security implications, especially if the users have upload permission or shell access, so be careful enabling this option. 487 Starting the FTP Server SLES 12 SP4If you check the Verbose Logging option, all FTP requests and responses are logged. You can limit permissions of les created by anonymous and/or authenticated users with umask. Set the le creation mask for anonymous users in Umask for Anonymous and the le creation mask for authenticated users in Umask for Authenticated Users. The masks should be entered as octal numbers with a leading zero. For more information about umask, see the umask man page ( man 1p umask ). In the FTP Directories frame set the directories used for anonymous and authorized users. With Browse, you can select a directory to be used from the local le system. The default FTP directory for anonymous users is /srv/ftp . Note that vsftpd does not allow this directory to be writable for all users. The subdirectory upload with write permissions for anonymous users is created instead. 33.3 FTP Performance Settings In the Performance dialog set the parameters which aect the load on the FTP server. Max Idle Time is the maximum time (in minutes) the remote client may spend between FTP commands. In case of longer inactivity, the remote client is disconnected. Max Clients for One IP determines the maximum number of clients which can be connected from a single IP address. Max Clients determines the maximum number of clients which may be connected. Any additional clients will get an error message. The maximum data transfer rate (in KB/s) is set in Local Max Rate for local authenticated users, and in Anonymous Max Rate for anonymous clients respectively. The default value for the rate settings is 0 , which means unlimited data transfer rate. 33.4 Authentication In the Enable/Disable Anonymous and Local Users frame of the Authentication dialog, you can set which users are allowed to access your FTP server. You can choose between the following options: granting access to anonymous users only, to authenticated users only (with accounts on the system) or to both types of users. To allow users to upload les to the FTP server, check Enable Upload in the Uploading frame of the Authentication dialog. Here you can allow uploading or creating directories even for anonymous users by checking the respective box. 488 FTP Performance Settings SLES 12 SP4Note: vsftp—Allowing File Upload for Anonymous Users If a vsftpd server is used and you want anonymous users to be able to upload les or create directories, a subdirectory with writing permissions for all users needs to be created in the anonymous FTP directory. 33.5 Expert Settings An FTP server can run in active or in passive mode. By default the server runs in passive mode. To switch into active mode, deselect the Enable Passive Mode option in the Expert Settings dialog. You can also change the range of ports on the server used for the data stream by tweaking the Min Port for Pas. Mode and Max Port for Pas. Mode options. If you want encrypted communication between clients and the server, you can Enable SSL. Check the versions of the protocol to be supported and specify the DSA certicate to be used for SSL encrypted connections. If your system is protected by a rewall, check Open Port in Firewall to enable a connection to the FTP server. 33.6 For More Information For more information about the FTP server read the manual pages of vsftpd and vsftpd.conf . 489 Expert Settings SLES 12 SP434 The Proxy Server Squid Squid is a widely-used proxy cache for Linux and Unix platforms. This means that it stores requested Internet objects, such as data on a Web or FTP server, on a machine that is closer to the requesting workstation than the server. It can be set up in multiple hierarchies to assure optimal response times and low bandwidth usage, even in modes that are transparent to end users. Additional software like squidGuard can be used to lter Web content. Squid acts as a proxy cache. It redirects object requests from clients (in this case, from Web browsers) to the server. When the requested objects arrive from the server, it delivers the objects to the client and keeps a copy of them in the hard disk cache. An advantage of caching is that several clients requesting the same object can be served from the hard disk cache. This enables clients to receive the data much faster than from the Internet. This procedure also reduces the network trac. Along with actual caching, Squid oers a wide range of features: Distributing load over intercommunicating hierarchies of proxy servers Dening strict access control lists for all clients accessing the proxy Allowing or denying access to specic Web pages using other applications Generating statistics about frequently-visited Web pages for the assessment of surng habits Squid is not a generic proxy. It normally proxies only HTTP connections. It supports the protocols FTP, Gopher, SSL, and WAIS, but it does not support other Internet protocols, such as the news protocol, or video conferencing protocols. Because Squid only supports the UDP protocol to provide communication between dierent caches, many multimedia programs are not supported. 34.1 Some Facts about Proxy Caches As a proxy cache, Squid can be used in several ways. When combined with a rewall, it can help with security. Multiple proxies can be used together. It can also determine what types of objects should be cached and for how long. 490 Some Facts about Proxy Caches SLES 12 SP434.1.1 Squid and Security It is possible to use Squid together with a rewall to secure internal networks from the outside using a proxy cache. The rewall denies all clients access to external services except Squid. All Web connections must be established by the proxy. With this conguration, Squid completely controls Web access. If the rewall conguration includes a DMZ, the proxy should operate within this zone. Section 34.6, “Configuring a Transparent Proxy” describes how to implement a transparent proxy. This simplies the conguration of the clients, because in this case, they do not need any information about the proxy. 34.1.2 Multiple Caches Several instances of Squid can be congured to exchange objects between them. This reduces the total system load and increases the chances of retrieving an object from the local network. It is also possible to congure cache hierarchies, so a cache can forward object requests to sibling caches or to a parent cache—causing it to request objects from another cache in the local network or directly from the source. Choosing the appropriate topology for the cache hierarchy is very important, because it is not desirable to increase the overall trac on the network. For a very large network, it would make sense to congure a proxy server for every subnet and connect them to a parent proxy, which in turn is connected to the proxy cache of the ISP. All this communication is handled by ICP (Internet cache protocol) running on top of the UDP protocol. Data transfers between caches are handled using HTTP (hypertext transmission protocol) based on TCP. To nd the most appropriate server from which to request objects, a cache sends an ICP request to all sibling proxies. The sibling proxies answer these requests via ICP responses. If the object was detected, they use the code HIT , if not, they use MISS . If multiple HIT responses were found, the proxy server decides from which server to download, depending on factors such as which cache sent the fastest answer or which one is closer. If no satisfactory responses are received, the request is sent to the parent cache. 491 Squid and Security SLES 12 SP4Note: How Squid Avoids Duplication of Objects To avoid duplication of objects in dierent caches in the network, other ICP protocols are used, such as CARP (cache array routing protocol) or HTCP (hypertext cache protocol). The more objects maintained in the network, the greater the possibility of nding the desired one. 34.1.3 Caching Internet Objects Many objects available in the network are not static, such as dynamically generated pages and TLS/SSL-encrypted content. Objects like these are not cached because they change each time they are accessed. To determine how long objects should remain in the cache, objects are assigned one of several states. Web and proxy servers nd out the status of an object by adding headers to these objects, such as “Last modied” or “Expires” and the corresponding date. Other headers specifying that objects must not be cached can be used as well. Objects in the cache are normally replaced, because of a lack of free disk space, using algorithms such as LRU (last recently used). This means that the proxy expunges those objects that have not been requested for the longest time. 34.2 System Requirements System requirements largely depend on the maximum network load that the system must bear. Therefore, examine load peaks, as during those times, load might be more than four times the day''s average. When in doubt, slightly overestimate the system''s requirements. Having Squid working close to the limit of its capabilities can lead to a severe loss in quality of service. The following sections point to system factors in order of signicance: 1. RAM size 2. CPU speed/physical CPU cores 3. Size of the disk cache 4. Hard disks/SSDs and their architecture 492 Caching Internet Objects SLES 12 SP434.2.1 RAM The amount of memory (RAM) required by Squid directly correlates with the number of objects in the cache. Random access memory is much faster than a hard disk/SSD. Therefore, it is very important to have sucient memory for the Squid process, because system performance is dramatically reduced if the swap disk is used. Squid also stores cache object references and frequently requested objects in the main memory to speed up retrieval of this data. In addition to that, there is other data that Squid needs to keep in memory, such as a table with all the IP addresses handled, an exact domain name cache, the most frequently requested objects, access control lists, buers, and more. 34.2.2 CPU Squid is tuned to work best with lower processor core counts (4–8 physical cores), with each providing high performance. Technologies providing virtual cores such as hyperthreading can hurt performance. To make the best use of multiple CPU cores, it is necessary to set up multiple worker threads writing to dierent caching devices. By default, multi-core support is mostly disabled. 34.2.3 Size of the Disk Cache In a small cache, the probability of a HIT (nding the requested object already located there) is small, because the cache is easily lled and less requested objects are replaced by newer ones. If, for example, 1 GB is available for the cache and the users use up only 10 MB per day surng, it would take more than one hundred days to ll the cache. The easiest way to determine the necessary cache size is to consider the maximum transfer rate of the connection. With a 1 Mbit/s connection, the maximum transfer rate is 128 KB/s. If all this trac ended up in the cache, in one hour it would add up to 460 MB. Assuming that all this trac is generated in only eight working hours, it would reach 3.6 GB in one day. Because the connection is normally not used to its upper volume limit, it can be assumed that the total data volume handled by the cache is approximately 2 GB. Hence, in this example, 2 GB of disk space is required for Squid to keep one day''s worth of browsing data cached. 493 RAM SLES 12 SP434.2.4 Hard Disk/SSD Architecture Speed plays an important role in the caching process, so this factor deserves special attention. For hard disks/SSDs, this parameter is described as random seek time or random read performance, measured in milliseconds. Because the data blocks that Squid reads from or writes to the hard disk/SSD tend to be small, the seek time/read performance of the hard disk/SSD is more important than its data throughput. For use as a proxy, hard disks with high rotation speeds or SSDs are the best choice. When using hard disks, it can be better to use multiple smaller hard disks, each with a single cache directory to avoid excessive read times. Using a RAID system allows increasing reliability at expense of speed. However, for performance reasons, avoid (software) RAID5 and similar settings. File system choice is usually not decisive. However, using the mount option noatime can improve performance—Squid provides its own time stamps and thus does not need the le system to track access times. 34.3 Basic Usage of Squid If not already installed, install the package squid . squid is not among the packages installed by default on SUSE® Linux Enterprise Server. Squid is already precongured in SUSE Linux Enterprise Server, you can start it directly after the installation. To ensure a smooth start-up, the network should be congured in a way that at least one name server and the Internet can be reached. Problems can arise if a dial-up connection is used with a dynamic DNS conguration. In this case, at least the name server should be specied, because Squid does not start if it does not detect a DNS server in /etc/resolv.conf . 34.3.1 Starting Squid To start Squid, use: tux > sudo systemctl start squid If you want Squid to start together with the system, enable the service with systemctl enable squid . 494 Hard Disk/SSD Architecture SLES 12 SP434.3.2 Checking Whether Squid Is Working To check whether Squid is running, choose one of the following ways: Using systemctl : tux > systemctl status squid The output of this command should indicate that Squid is loaded and active (running) . Using Squid itself: tux > sudo squid -k check | echo $? The output of this command should be 0 , but may contain additional warnings or messages. To test the functionality of Squid on the local system, choose one of the following ways: To test, you can use squidclient , a command-line tool that can output the response to a Web request, similar to wget or curl . Unlike those tools, squidclient will automatically connect to the default proxy setup of Squid, localhost:3128 . However, if you changed the conguration of Squid, you need to congure squidclient to use dierent settings using command line options. For more information, see squidclient --help . EXAMPLE 34.1: A REQUEST WITH squidclient tux > squidclient http://www.example.org HTTP/1.1 200 OK Cache-Control: max-age=604800 Content-Type: text/html Date: Fri, 22 Jun 2016 12:00:00 GMT Expires: Fri, 29 Jun 2016 12:00:00 GMT Last-Modified: Fri, 09 Aug 2013 23:54:35 GMT Server: ECS (iad/182A) Vary: Accept-Encoding X-Cache: HIT x-ec-custom-error: 1 Content-Length: 1270 X-Cache: MISS from moon 1 X-Cache-Lookup: MISS from moon:3128 Via: 1.1 moon (squid/3.5.16) 2 Connection: close 495 Checking Whether Squid Is Working SLES 12 SP4 [...] The output shown in Example 34.1, “A Request With squidclient” can be split into two parts: 1. The protocol headers of the response: the lines before the blank line. 2. The actual content of the response: the lines after the blank line. To verify that Squid is used, refer to the selected header lines: 1 The value of the header X-Cache tells you that the requested document was not in the Squid cache ( MISS ) of the computer moon . The example above contains two X-Cache lines. You can ignore the rst X- Cache header. It is produced by the internal caching software of the originating Web server. 2 The value of the header Via tells you the HTTP version, the name of the computer, and the version of Squid in use. Using a browser: Set up localhost as the proxy and 3128 as the port. You can then load a page and check the response headers in the Network panel of the browser''s Inspector or Developer Tools. The headers should be reproduced similarly to the way shown in Example 34.1, “A Request With squidclient”. To allow users from the local system and other systems to access Squid and the Internet, change the entry in the conguration les /etc/squid/squid.conf from http_access deny all to http_access allow all . However, in doing so, consider that Squid is made completely accessible to anyone by this action. Therefore, dene ACLs (access control lists) that control access to the proxy. After modifying the conguration le, Squid must be reloaded or restarted. For more information on ACLs, see Section 34.5.2, “Options for Access Controls”. If Squid quits after a short period of time even though it was started successfully, check whether there is a faulty name server entry or whether the /etc/resolv.conf le is missing. Squid logs the cause of a start-up failure in the le /var/log/squid/cache.log . 496 Checking Whether Squid Is Working SLES 12 SP434.3.3 Stopping, Reloading, and Restarting Squid To reload Squid, choose one of the following ways: Using systemctl : root # systemctl reload squid or root # systemctl restart squid Using YaST: In the Squid module, click the Save Settings and Restart Squid Now. button. To stop Squid, choose one of the following ways: Using systemctl : root # systemctl stop squid Using YaST In the Squid module click the Stop Squid Now. button. Shutting down Squid can take a while, because Squid waits up to half a minute before dropping the connections to the clients and writing its data to the disk (see shutdown_lifetime option in /etc/squid/squid.conf ), Warning: Terminating Squid Terminating Squid with kill or killall can damage the cache. To be able to restart Squid, damaged caches must be deleted. 34.3.4 Removing Squid Removing Squid from the system does not remove the cache hierarchy and log les. To remove these, delete the /var/cache/squid directory manually. 497 Stopping, Reloading, and Restarting Squid SLES 12 SP434.3.5 Local DNS Server Setting up a local DNS server makes sense even if it does not manage its own domain. It then simply acts as a caching-only name server and is also able to resolve DNS requests via the root name servers without requiring any special conguration (see Section 26.4, “Starting the BIND Name Server”). How this can be done depends on whether you chose dynamic DNS during the conguration of the Internet connection. Dynamic DNS Normally, with dynamic DNS, the DNS server is set by the provider during the establishment of the Internet connection and the local /etc/resolv.conf le is adjusted automatically. This behavior is controlled in the /etc/sysconfig/network/config le with the NETCONFIG_DNS_POLICY syscong variable. Set NETCONFIG_DNS_POLICY to "" with the YaST syscong editor. Then, add the local DNS server in the /etc/resolv.conf le with the IP address 127.0.0.1 for localhost . This way, Squid can always nd the local name server when it starts. To make the provider''s name server accessible, specify it in the conguration le /etc/ named.conf under forwarders along with its IP address. With dynamic DNS, this can be achieved automatically when establishing the connection by setting the syscong variable NETCONFIG_DNS_POLICY to auto . Static DNS With static DNS, no automatic DNS adjustments take place while establishing a connection, so there is no need to change any syscong variables. However, you must specify the local DNS server in the le /etc/resolv.conf as described in Dynamic DNS. Additionally, the provider''s static name server must be specied manually in the /etc/named.conf le under forwarders along with its IP address. Tip: DNS and Firewall If you have a rewall running, make sure DNS requests can pass it. 498 Local DNS Server SLES 12 SP434.4 The YaST Squid Module The YaST Squid module contains the following tabs: Start-Up Species how Squid is started and which Firewall port is open on which interfaces. HTTP Ports Dene all ports where Squid will listen for clients'' HTTP requests. Refresh Patterns Denes how Squid treats objects in the cache. Cache Settings Denes settings in regard to cache memory, maximum and minimum object size, and more. Cache Directory Denes the top-level directory where Squid stores all cache swap les. Access Control Controls the access to the Squid server via ACL groups. Logging and Timeout Dene paths to access, cache, and cache store log les in addition with connection timeouts and client lifetime. Miscellaneous Sets language and mail address of administrator. 34.5 The Squid Configuration File All Squid proxy server settings are made in the /etc/squid/squid.conf le. To start Squid for the rst time, no changes are necessary in this le, but external clients are initially denied access. The proxy is available for localhost . The default port is 3128 . The preinstalled conguration le /etc/squid/squid.conf provides detailed information about the options and many examples. Many entries are commented and therefore begin with the comment character # . The relevant specications can be found at the end of the line. The given values usually correlate with the default values, so removing the comment signs without changing any of the parameters usually 499 The YaST Squid Module SLES 12 SP4has no eect. If possible, leave the commented lines as they are and insert the options along with the modied values in the line below. This way, the default values may easily be recovered and compared with the changes. Tip: Adapting the Configuration File After an Update If you have updated from an earlier Squid version, it is recommended to edit the new / etc/squid/squid.conf and only apply the changes made in the previous le. Sometimes, Squid options are added, removed, or modied. Therefore, if you try to use the old squid.conf , Squid might stop working properly. 34.5.1 General Configuration Options The following is a list of a selection of conguration options for Squid. It is not exhaustive. The Squid package contains a full, lightly documented list of options in /etc/squid/ squid.conf.documented . http_port PORT This is the port on which Squid listens for client requests. The default port is 3128 , but 8080 is also common. cache_peer HOST_NAME TYPE PROXY_PORT ICP_PORT This option allows creating a network of caches that work together. The cache peer is a computer that also hosts a network cache and stands in a relationship to your own. The type of relationship is specied as the TYPE . The type can either be parent or sibling . As the HOST_NAME , specify the name or IP address of the proxy to use. For PROXY_PORT , specify the port number for use in a browser (usually 8080 ). Set ICP_PORT to 7 or, if the ICP port of the parent is not known and its use is irrelevant to the provider, to 0 . To make Squid behave like a Web browser instead of like a proxy, prohibit the use of the ICP protocol. You can do so by appending the options default and no-query . cache_mem SIZE This option denes the amount of memory Squid can use for very popular replies. The default is 8 MB . This does not specify the memory usage of Squid and may be exceeded. cache_dir STORAGE_TYPE CACHE_DIRECTORY CACHE_SIZE LEVEL_1_DIRECTORIES LEVEL_2_DIRECTORIES 500 General Configuration Options SLES 12 SP4The option cache_dir denes the directory for the disk cache. In the default conguration on SUSE Linux Enterprise Server, Squid does not create a disk cache. The placeholder STORAGE_TYPE can be one of the following: Directory-based storage types: ufs , aufs (the default), diskd . All three are variations of the storage format ufs . However, while ufs runs as part of the core Squid thread, aufs runs in a separate thread, and diskd uses a separate process. This means that the latter two types avoid blocking Squid because of disk I/O. Database-based storage systems: rock . This storage format relies on a single database le, in which each object takes up one or more memory units of a xed size (“slots”). In the following, only the parameters for storage types based on ufs will be discussed. rock has somewhat dierent parameters. The CACHE_DIRECTORY is the directory for the disk cache. By default, that is /var/cache/ squid . CACHE_SIZE is the maximum size of that directory in megabytes; by default, this is set to 100 MB. Set it to between 50% and a maximum of 80% of available disk space. The nal two values, LEVEL_1_DIRECTORIES and LEVEL_2_DIRECTORIES specify how many subdirectories are created in the CACHE_DIRECTORY . By default, 16 subdirectories are created at the rst level below CACHE_DIRECTORY and 256 within each of these. These values should only be increased with caution, because creating too many directories can lead to performance problems. If you have several disks that share a cache, specify several cache_dir lines. cache_access_log LOG_FILE , cache_log LOG_FILE , cache_store_log LOG_FILE These three options specify the paths where Squid logs all its actions. Normally, nothing needs to be changed here. If Squid is burdened by heavy usage, it might make sense to distribute the cache and the log les over several disks. client_netmask NETMASK This option allows masking IP addresses of clients in the log les by applying a subnet mask. For example, to set the last digit of the IP address to 0 , specify 255.255.255.0 . ftp_user E-MAIL This option allows setting the password that Squid should use for anonymous FTP login. Specify a valid e-mail address here, because some FTP servers check these for validity. cache_mgr E-MAIL 501 General Configuration Options SLES 12 SP4If it unexpectedly crashes, Squid sends a message to this e-mail address. The default is webmaster. logfile_rotate VALUE If you run squid   -k rotate , Squid can rotate log les. The les are numbered in this process and, after reaching the specied value, the oldest le is overwritten. The default value is 10 which rotates log les with the numbers 0 to 9. However, on SUSE Linux Enterprise Server, rotating log les is performed automatically using logrotate and the conguration le /etc/logrotate.d/squid . append_domain DOMAIN Use append_domain to specify which domain to append automatically when none is given. Usually, your own domain is specied here, so specifying www in the browser accesses your own Web server. forwarded_for STATE If this option is set to on , it adds a line to the header similar to this: X-Forwarded-For: 192.168.0.1 If you set this option to off , Squid removes the IP address and the system name of the client from HTTP requests. negative_ttl TIME , negative_dns_ttl TIME If these options are set, Squid will cache some types of failures, such as 404 responses. It will then refuse to issue new requests, even if the resource would be available then. By default, negative_ttl is set to 0 , negative_dns_ttl is set to 1 minutes . This means that negative responses to Web requests are not cached by default, while negative responses to DNS requests are cached for 1 minute. never_direct allow ACL_NAME To prevent Squid from taking requests directly from the Internet, use the option never_direct to force connection to another proxy. This must have previously been specied in cache_peer . If all is specied as the ACL_NAME , all requests are forwarded directly to the parent . This can be necessary, for example, if you are using a provider that dictates the use of its proxies or denies its rewall direct Internet access. 502 General Configuration Options SLES 12 SP434.5.2 Options for Access Controls Squid provides a detailed system for controlling the access to the proxy. These Access Control Lists (ACL) are lists with rules that are processed sequentially. ACLs must be dened before they can be used. Some default ACLs, such as all and localhost , already exist. However, the mere denition of an ACL does not mean that it is actually applied. This only happens when there is a corresponding http_access rule. The syntax for the option acl is as follows: acl ACL_NAME TYPE DATA The placeholders within this syntax stand for the following: The name ACL_NAME can be chosen arbitrarily. For TYPE , select from a variety of dierent options which can be found in the ACCESS CONTROLS section in the /etc/squid/squid.conf le. The specication for DATA depends on the individual ACL type and can also be read from a le. For example, “via” host names, IP addresses, or URLs. To add rules in the YaST squid module, open the module and click the Access Control tab. Click Add under the ACL Groups list and enter the name of your rule, the type, and its parameters. For more information on types of ACL rules, see the Squid documentation at http://www.squid- cache.org/Versions/v3/3.5/cfgman/acl.html . EXAMPLE 34.2: DEFINING ACL RULES acl mysurfers srcdomain .example.com 1 acl teachers src 192.168.1.0/255.255.255.0 2 acl students src 192.168.7.0-192.168.9.0/255.255.255.0 3 acl lunch time MTWHF 12:00-15:00 4 1 This ACL denes mysurfers to be all users coming from within .example.com (as determined by a reverse lookup for the IP). 2 This ACL denes teachers to be the users of computers with IP addresses starting with 192.168.1. . 3 This ACL denes students to be the users of the computer with IP addresses starting with 192.168.7. , 192.168.8. , or 192.168.9. . 503 Options for Access Controls SLES 12 SP44 This ACL denes lunch as a time on the days Monday, Tuesday, ... Friday between noon and 3 p.m. http_access allow ACL_NAME http_access denes who is allowed to use the proxy and who can access what on the Internet. For this, ACLs must be dened. localhost and all have already been dened above for which you can deny or allow access via deny or allow . A list containing any number of http_access entries can be created, processed from top to bottom. Depending on which occurs rst, access is allowed or denied to the respective URL. The last entry should always be http_access deny all . In the following example, localhost has free access to everything while all other hosts are denied access completely: http_access allow localhost http_access deny all In another example using these rules, the group teachers always has access to the Internet. The group students only has access between Monday and Friday during lunch time: http_access deny localhost http_access allow teachers http_access allow students lunch time http_access deny all For readability, within the conguration le /etc/squid/squid.conf , specify all http_access options as a block. url_rewrite_program PATH With this option, specify a URL rewriter. For example, this can be squidGuard ( /usr/ sbin/squidGuard ) which allows blocking unwanted URLs. With it, Internet access can be individually controlled for various user groups using proxy authentication and the appropriate ACLs. For more information on squidGuard, see Section 34.8, “squidGuard”. auth_param basic program PATH If users must be authenticated on the proxy, set a corresponding program, such as /usr/ sbin/pam_auth . When accessing pam_auth for the rst time, the user sees a login window in which they need to specify a user name and a password. In addition, you need an ACL, so only clients with a valid login can use the Internet: acl password proxy_auth REQUIRED 504 Options for Access Controls SLES 12 SP4http_access allow password http_access deny all In the acl proxy_auth option, using REQUIRED means that all valid user names are accepted. REQUIRED can also be replaced with a list of permitted user names. ident_lookup_access allow ACL_NAME With this option, have an ident request run to nd each user''s identity for all clients dened by an ACL of the type src . Alternatively, use this for all clients, apply the predened ACL all as the ACL_NAME . All clients covered by ident_lookup_access must run an ident daemon. On Linux, you can use pidentd (package pidentd ) as the ident daemon. For other operating systems, free software is usually available. To ensure that only clients with a successful ident lookup are permitted, dene a corresponding ACL: acl identhosts ident REQUIRED http_access allow identhosts http_access deny all In the acl identhosts ident option, using REQUIRED means that all valid user names are accepted. REQUIRED can also be replaced with a list of permitted user names. Using ident can slow down access time, because ident lookups are repeated for each request. 34.6 Configuring a Transparent Proxy The usual way of working with proxy servers is as follows: the Web browser sends requests to a certain port of the proxy server and the proxy always provides these required objects, regardless of whether they are in its cache. However, in some cases the transparent proxy mode of Squid makes sense: If, for security reasons, it is recommended that all clients use a proxy to surf the Internet. If all clients must use a proxy, regardless of whether they are aware of it. If the proxy in a network is moved, but the existing clients need to retain their old conguration. 505 Configuring a Transparent Proxy SLES 12 SP4A transparent proxy intercepts and answers the requests of the Web browser, so the Web browser receives the requested pages without knowing where they are coming from. As the name indicates, the entire process is transparent to the user. PROCEDURE 34.1: SQUID AS A TRANSPARENT PROXY (COMMAND LINE) 1. In /etc/squid/squid.conf , on the line of the option http_port add the parameter transparent : http_port 3128 transparent 2. Restart Squid: tux > sudo systemctl restart squid 3. Set up SuSEFirewall2 to redirect HTTP trac to the port given in http_proxy (in the example above, that was port 3128). To do so, edit the conguration le /etc/ sysconfig/SuSEfirewall2 . This example assumes that you are using the following devices: Device pointing to the Internet: FW_DEV_EXT="eth1" Device pointing to the network: FW_DEV_INT="eth0" Dene ports and services (see /etc/services ) on the rewall that are accessed from untrusted (external) networks such as the Internet. In this example, only Web services are oered to the outside: FW_SERVICES_EXT_TCP="www" Dene ports or services (see /etc/services ) on the rewall that are accessed from the secure (internal) network, both via TCP and UDP: FW_SERVICES_INT_TCP="domain www 3128" FW_SERVICES_INT_UDP="domain" This allows accessing Web services and Squid (whose default port is 3128 ). The service “domain” stands for DNS (domain name service). This service is commonly used. Otherwise, simply remove domain from the above entries and set the following option to no : FW_SERVICE_DNS="yes" 506 Configuring a Transparent Proxy SLES 12 SP4The option FW_REDIRECT is very important, as it is used for the actual redirection of HTTP trac to a specic port. The conguration le explains the syntax in a comment above the option: # Format: # list of [,,[,dport[:lport]] # Where protocol is either tcp or udp. dport is the original # destination port and lport the port on the local machine to # redirect the traffic to # # An exclamation mark in front of source or destination network # means everything EXCEPT the specified network That is: 1. Specify the IP address and the netmask of the internal networks accessing the proxy rewall. 2. Specify the IP address and the netmask to which these clients send their requests. In the case of Web browsers, specify the networks 0/0 , a wild card that means “to everywhere.” 3. Specify the original port to which these requests are sent. 4. Specify the port to which all these requests are redirected. In the example below, only Web services (port 80 ) are redirected to the proxy port (port 3128 ). If there are more networks or services to add, separate them with a space in the respective entry. Because Squid supports protocols other than HTTP, you can also redirect requests from other ports to the proxy. For example, you can also redirect port 21 (FTP) and port 443 (HTTPS or SSL). Therefore, for a Squid conguration, you could use: FW_REDIRECT="192.168.0.0/16,0/0,tcp,80,3128" 4. In the conguration le /etc/sysconfig/SuSEfirewall2 , make sure that the entry START_FW is set to "yes" . 5. Restart SuSEFirewall2: tux > sudo systemctl restart SuSEfirewall2 507 Configuring a Transparent Proxy SLES 12 SP46. To verify that everything is working properly, check the Squid log les in /var/log/ squid/access.log . To verify that all ports are correctly congured, perform a port scan on the machine from any computer outside your network. Only the Web services (port 80) should be open. To scan the ports with nmap , use: nmap -O IP_ADDRESS PROCEDURE 34.2: SQUID AS A TRANSPARENT PROXY (YAST) 1. Start the YaST Squid module: a. In the Start-Up tab, enable Open Ports in Firewall. Click Firewall Details to select the interfaces on which to open the port. This option is available only if the Firewall is enabled. b. In the HTTP Ports tab, select the rst line with the port 3128 . c. Click the Edit button. A small window appear where you can edit the current HTTP port. Select Transparent. d. Finish with Ok. 2. Congure the Firewall settings as described in Step 3 of Procedure  34.1, “Squid as a Transparent Proxy (Command Line)”. 34.7 Using the Squid Cache Manager CGI Interface (cachemgr.cgi) The Squid cache manager CGI interface ( cachemgr.cgi ) is a CGI utility for displaying statistics about the memory usage of a running Squid process. It is also a convenient way to manage the cache and view statistics without logging the server. PROCEDURE 34.3: SETTING UP cachemgr.cgi 1. Make sure the Apache Web server is running on your system. Congure Apache as described in Chapter 32, The Apache HTTP Server. In particular, see Section 32.5, “Enabling CGI Scripts”. To check whether Apache is already running, use: tux > sudo systemctl status apache2 508 Using the Squid Cache Manager CGI Interface (cachemgr.cgi) SLES 12 SP4If inactive is shown, you can start Apache with the SUSE Linux Enterprise Server default settings: tux > sudo systemctl start apache2 2. Now enable cachemgr.cgi in Apache. To do so, create a conguration le for a ScriptAlias . Create the le in the directory /etc/apache2/conf.d and name it cachemgr.conf . In it, add the following: ScriptAlias /squid/cgi-bin/ /usr/lib64/squid/ Options +ExecCGI AddHandler cgi-script .cgi Require host HOST_NAME Replace HOST_NAME with the host name of the computer you want to access cachemgr.cgi from. This allows only your computer to access cachemgr.cgi . To allow access from anywhere, use Require all granted instead. 3. If Squid and your Apache Web server run on the same computer, there should be no changes that need to be made to /etc/squid/squid.conf . However, verify that / etc/squid/squid.conf contains the following lines: http_access allow manager localhost http_access deny manager These lines allow you to access the manager interface from your own computer ( localhost ) but not from elsewhere. If Squid and your Apache Web server run on dierent computers, you need to add extra rules to allow access from the CGI script to Squid. Dene an ACL for your server (replace WEB_SERVER_IP with the IP address of your Web server): acl webserver src WEB_SERVER_IP/255.255.255.255 Make sure the following rules are in the conguration le. Compared to the default conguration, only the rule in the middle is new. However, the sequence is important. 509 Using the Squid Cache Manager CGI Interface (cachemgr.cgi) SLES 12 SP4http_access allow manager localhost http_access allow manager webserver http_access deny manager 4. (Optional) Optionally, you can congure one or more passwords for cachemgr.cgi . This also allows access to more actions such as closing the cache remotely or viewing more information about the cache. For this, congure the options cache_mgr and cachemgr_passwd with one or more password for the manager and a list of allowed actions. For example, to explicitly enable viewing the index page, the menu, 60-minute average of counters without authentication, to enable toggling oine mode using the password secretpassword , and to completely disable everything else, use the following conguration: cache_mgr user cachemgr_passwd none index menu 60min cachemgr_passwd secretpassword offline_toggle cachemgr_passwd disable all cache_mgr denes a user name. cache_mgr denes which actions are allowed using which password. The keywords none and disable are special: none removes the need for a password, disable disables functionality outright. The full list of actions can be best seen after logging in to cachemgr.cgi . To nd out how the operation needs to be referenced in the conguration le, see the string after &operation= in the URL of the action page. all is a special keyword meaning all actions. 5. Reload Squid and Apache after the conguration le changes: tux > sudo systemctl reload squid 6. To view the statistics, go to the cachemgr.cgi page that you set up before. For example, it could be http://webserver.example.org/squid/cgi-bin/cachemgr.cgi . Choose the right server, and, if set, specify user name and password. Then click Continue and browse through the dierent statistics. 510 Using the Squid Cache Manager CGI Interface (cachemgr.cgi) SLES 12 SP434.8 squidGuard This section is not intended to explain an extensive conguration of squidGuard, only to introduce it and give some advice for using it. For more in-depth conguration issues, refer to the squidGuard Web site at http://www.squidguard.org . squidGuard is a free (GPL), exible, and fast lter, redirector, and access controller plug-in for Squid. It lets you dene multiple access rules with dierent restrictions for dierent user groups on a Squid cache. squidGuard uses Squid''s standard redirector interface. squidGuard can do the following: Limit Web access for some users to a list of accepted or well-known Web servers or URLs. Block access to some listed or blacklisted Web servers or URLs for some users. Block access to URLs matching a list of regular expressions or words for some users. Redirect blocked URLs to an “intelligent” CGI-based information page. Redirect unregistered users to a registration form. Redirect banners to an empty GIF. Use dierent access rules based on time of day, day of the week, date, etc. Use dierent rules for dierent user groups. squidGuard and Squid cannot be used to: Edit, lter, or censor text inside documents. Edit, lter, or censor HTML-embedded scripts such as JavaScript. PROCEDURE 34.4: SETTING UP SQUIDGUARD 1. Before it can be used, install squidGuard . 2. Provide a minimal conguration le as /etc/squidguard.conf . Find conguration examples in http://www.squidguard.org/Doc/examples.html . Experiment later with more complicated conguration settings. 3. Next, create an “access denied” HTML page or CGI page that Squid can redirect to if the client requests a blacklisted Web site. Using Apache is strongly recommended. 511 squidGuard SLES 12 SP44. Now, congure Squid to use squidGuard. Use the following entry in the /etc/squid/ squid.conf le: redirect_program /usr/bin/squidGuard 5. Another option called redirect_children congures the number of “redirect” (in this case squidGuard) processes running on the machine. The more processes you set, the more RAM is required. Try low numbers rst, for example, 4 : redirect_children 4 6. Last, have Squid load the new conguration by running systemctl reload squid . Now, test your settings with a browser. 34.9 Cache Report Generation with Calamaris Calamaris is a Perl script used to generate reports of cache activity in ASCII or HTML format. It works with native Squid access log les. The Calamaris home page is located at http://cord.de/ calamaris-english . This tool does not belong to the SUSE Linux Enterprise Server default installation scope—to use it, install the calamaris package. Log in as root , then enter: cat access1.log [access2.log access3.log] | calamaris OPTIONS > reportfile When using more than one log le, make sure they are chronologically ordered, with older les listed rst. This can be achieved by either listing the les one after the other as in the example above, or by using access{1..3}.log . calamaris takes the following options: -a output all available reports -w output as HTML report -l include a message or logo in report header More information about the various options can be found in the program''s manual page with man   calamaris . 512 Cache Report Generation with Calamaris SLES 12 SP4A typical example is: cat access.log.{10..1} access.log | calamaris -a -w \ > /usr/local/httpd/htdocs/Squid/squidreport.html This puts the report in the directory of the Web server. Apache is required to view the reports. 34.10 For More Information Visit the home page of Squid at http://www.squid-cache.org/ . Here, nd the “Squid User Guide” and a very extensive collection of FAQs on Squid. In addition, mailing lists are available for Squid at http://www.squid-cache.org/Support/mailing- lists.html . 513 For More Information SLES 12 SP435 Web Based Enterprise Management Using SFCB 35.1 Introduction and Basic Concept SUSE® Linux Enterprise Server (SLES) provides a collection of open standards based tools for the unied management of disparate computing systems and environments. Our enterprise solutions implement the standards proposed by the Distributed Management Task Force. The following paragraphs describe their basic components. Distributed Management Task Force, Inc (DMTF) is the industry organization which leads the development of management standards for enterprise and Internet environments. Their goal is to unify management standards and initiatives, and to enable more integrated, cost eective and interoperable management solutions. DMTF standards provide common system management components for control and communication. Their solutions are independent of platforms and technologies. Web Based Enterprise Management and Common Information Model are one of their key technologies. Web Based Enterprise Management (WBEM) is a set of management and Internet standard technologies. WBEM is developed to unify the management of enterprise computing environments. It provides the ability for the industry to deliver a well-integrated collection of management tools using Web technologies. WBEM consists of the following standards: A data model: the Common Information Model (CIM) standard An encoding specication: CIM-XML Encoding Specication A transport mechanism: CIM operations over HTTP Common Information Model is a conceptual information model that describes system management. It is not bound to a particular implementation and enables the interchange of management information between management systems, networks, services and applications. There are two parts to CIM — the CIM Specication and the CIM Schema. 514 Introduction and Basic Concept SLES 12 SP4The CIM Specication describes the language, naming and meta schema. The meta schema is a formal denition of the model. It denes the terms used to express the model and their usage and semantics. The elements of the meta schema are classes, properties, and methods. The meta schema also supports indications and associations as types of classes, and references as types of properties. The CIM Schema provides the actual model descriptions. It supplies a set of classes with properties and associations that provide a well understood conceptual framework within which it is possible to organize the available information about the managed environment. The Common Information Model Object Manager (CIMOM) is a CIM object manager or, more specically, an application that manages objects according to the CIM standard. CIMOM manages communication between CIMOM providers and a CIM client, where the administrator manages the system. CIMOM providers are software performing specic tasks within the CIMOM that are requested by client applications. Each provider instruments one or more aspects of the CIMOM''s schema. These providers interact directly with the hardware. Standards Based Linux Instrumentation for Manageability (SBLIM) is a collection of tools designed to support Web-Based Enterprise Management (WBEM). SUSE® Linux Enterprise Server uses the open source CIMOM (or CIM server) from the SBLIM project called Small Footprint CIM Broker . Small Footprint CIM Broker is a CIM server intended for use in resource-limited or embedded environments. It is designed to be modular and lightweight at the same time. Its based on open standards and it supports CMPI providers, CIM-XML encoding, and Managed Object Format (MOF). It is highly congurable and performs stability even if the provider crashes. It is also easily accessible as it supports various transport protocols, such as HTTP, HTTPS, Unix domain sockets, Service Location Protocol (SLP), and Java Database Connectivity (JDBC). 35.2 Setting Up SFCB To set up the Small Footprint CIM Broker (SFCB) environment, make sure the Web-Based Enterprise Management pattern in YaST is selected during SUSE Linux Enterprise Server installation. Alternatively, select it as a component to install on a server that is already running. Make sure the following packages are installed on your system: cim-schema, Common Information Model (CIM) Schema 515 Setting Up SFCB SLES 12 SP4Contains the Common Information Model (CIM). CIM is a model for describing overall management information in a network or enterprise environments. CIM consists of a specication and a schema. The specication denes the details for integration with other management models. The schema provides the actual model descriptions. cmpi-bindings-pywbem Contains an adapter to write and run CMPI-type CIM providers in Python. cmpi-pywbem-base Contains base system CIM providers. cmpi-pywbem-power-management Contains power management providers based on DSP1027. python-pywbem Contains a Python module for making CIM operation calls through the WBEM protocol to query and update managed objects. cmpi-provider-register, CIMOM neutral provider registration utility Contains a utility allowing CMPI provider packages to register with whatever CIMOM happens to be present on the system. sblim-sfcb, Small Footprint CIM Broker Contains Small Footprint CIM Broker. It is a CIM server conforming to the CIM Operations over HTTP protocol. It is robust, with low resource consumption and, therefore, specically suited for embedded and resource constrained environments. SFCB supports providers written against the Common Manageability Programming Interface (CMPI). sblim-sfcc Contains Small Footprint CIM Client library runtime libraries. sblim-wbemcli Contains WBEM command line interface. It is a stand-alone command line WBEM client especially suited for basic systems management tasks. smis-providers Contains providers to instrument the volumes and snapshots on the Linux le system. These are based on SNIA''s SMI-S volume management prole and Copy Services prole respectively. 516 Setting Up SFCB SLES 12 SP4FIGURE 35.1: PACKAGE SELECTION FOR WEB-BASED ENTERPRISE MANAGEMENT PATTERN 35.2.1 Installing Additional Providers SUSE® Linux Enterprise Server software repository includes additional CIM providers that are not found in the Web-Based Enterprise Management installation pattern. You can easily get their list and installation status by searching the pattern sblim-cmpi- in the YaST software installation module. These providers cover various tasks of system management, such as DHCP, NFS, or kernel parameters setting. It is useful to install those providers which you are going to use with SFCB. 517 Installing Additional Providers SLES 12 SP4FIGURE 35.2: PACKAGE SELECTION OF ADDITIONAL CIM PROVIDERS 35.2.2 Starting, Stopping and Checking Status for SFCB CIM server sfcbd daemon is installed together with Web-Based Enterprise Management software and is started by default at system start-up. The following table explains how to start, stop and check status for sfcbd. TABLE 35.1: COMMANDS FOR MANAGING SFCBD Task Linux Command Start sfcbd Enter systemctl start sfcb as root in the command line. Stop sfcbd Enter systemctl stop sfcb as root in the command line. Check sfcbd status Enter systemctl status sfcb as root in the command line. 518 Starting, Stopping and Checking Status for SFCB SLES 12 SP435.2.3 Ensuring Secure Access The default setup of SFCB is relatively secure. However, check that the access to SFCB components is as secure as required for your organization. 35.2.3.1 Certificates Secure Socket Layers (SSL) transports require a certicate for secure communication to occur. When SFCB is installed, it has a self-signed certicate generated. You can replace the path to the default certicate with a path to a commercial or self-signed one by changing the sslCertificateFilePath: PATH_FILENAME setting in /etc/sfcb/ sfcb.cfg . The le must be in PEM format. By default, SFCB expects a server certicate in the following location: /etc/sfcb/server.pem To generate a new certicate, run the following command: tux > sudo sh /usr/share/sfcb/genSslCert.sh Generating SSL certificates in . Generating a 2048 bit RSA private key ...................................................................+++ .+++ writing new private key to ''/var/tmp/sfcb.0Bjt69/key.pem'' ----- By default, the script generates certicates client.pem , file.pem and server.pem in the current working directory. If you want the script to generate the certicates in /etc/sfcb directory, you need to append it to the command. If these les already exist, a warning message is displayed and the old certicates are not overwritten. tux > sudo sh /usr/share/sfcb/genSslCert.sh /etc/sfcb Generating SSL certificates in . WARNING: server.pem SSL Certificate file already exists. old file will be kept intact. WARNING: client.pem SSL Certificate trust store already exists. old file will be kept intact. You must remove the old certicates from the le system and run the command again. To change the way SFCB uses certicates, see Section 35.2.3.3, “Authentication”. 519 Ensuring Secure Access SLES 12 SP435.2.3.2 Ports By default, SFCB is congured to accept all communications through the secure port 5989. The following paragraphs explain the communication port setup and recommended conguration. Port 5989 (secure) The secure port that SFCB communications use via HTTPS services. This is the default. With this setting, all communications between the CIMOM and client applications are encrypted when sent over the Internet between servers and workstations. Users must authenticate with the client application to reach SFCB server. We recommend that you keep this setting. For the SFCB CIMOM to communicate with the necessary applications, this port must be open on routers and rewalls if they are present between the client application and the nodes being monitored. Port 5988 (insecure) The insecure port that SFCB communications use via HTTP services. This setting is disabled by default. With this setting, all communications between the CIMOM and client applications are open for review when sent over the Internet between servers and workstations by anyone, without any authentication. We recommend that you use this setting only when attempting to debug a problem with the CIMOM. When the problem is resolved, disable the non-secure port option back. For the SFCB CIMOM to communicate with the necessary applications that require non-secure access, this port must be open in routers and rewalls between the client application and the nodes being monitored. If you want to change the default port assignments, see Section 35.2.3.2, “Ports”. 35.2.3.3 Authentication SFCB supports HTTP basic authentication and authentication based on client certicates (HTTP over SSL connections). Basic HTTP authentication is enabled by specifying doBasicAuth=true in the SFCB conguration le ( /etc/sfcb/sfcb.cfg by default). SUSE® Linux Enterprise Server installation of SFCB supports Pluggable Authentication Modules (PAM) approach; therefore the local root user can authenticate to the SFCB CIMOM with local root user credentials. 520 Ensuring Secure Access SLES 12 SP4If the sslClientCertificate conguration property is set to accept or require , the SFCB HTTP adapter will request a certicate from clients when connecting via HTTP over SSL (HTTPS). If require is specied, the client must provide a valid certicate (according to the client trust store specied via sslClientTrustStore ). If the client fails to do so, the connection will be rejected by the CIM server. The setting sslClientCertificate=accept may not be obvious. It is very useful if both basic and client certicate authentication are allowed. If the client can provide a valid certicate, HTTPS connection will be established and the basic authentication procedure will not be executed. If this function cannot verify the certicate, the HTTP basic authentication will take place instead. 35.3 SFCB CIMOM Configuration SFCB is a lightweight implementation of the CIM server, but it is also highly congurable. Several options can control its behavior. You can control the SFCB server in three ways: by setting appropriate environment variables by using command line options by changing its conguration le 35.3.1 Environment Variables Several environment variables directly aect the behavior of SFCB. You need to restart the SFCB daemon by systemctl restart sfcb for these changes to take eect. PATH Species the path to the sfcbd daemon and utilities. LD_LIBRARY_PATH Species the path to the sfcb runtime libraries. Alternatively, you can add this path to the system-wide dynamic loader conguration le /etc/ld.so.conf . SFCB_PAUSE_PROVIDER Species the provider name. The SFCB server pauses after the provider is loaded for the rst time. You can then attach a runtime debugger to the provider''s process for debugging purposes. 521 SFCB CIMOM Configuration SLES 12 SP4SFCB_PAUSE_CODEC Species the name of the SFCB codec (currently supports only http . The SFCB server pauses after the codec is loaded for the rst time. You can then attach a runtime debugger to the process. SFCB_TRACE Species the level of debug messages for SFCB. Valid values are 0 (no debug messages), or 1 (key debug messages) to 4 (all debug messages). Default is 1. SFCB_TRACE_FILE By default, SFCB outputs its debug messages to standard error output (STDERR). Setting this variable causes the debug messages to be written to a specied le instead. SBLIM_TRACE Species the level of debug messages for SBLIM providers. Valid values are 0 (no debug messages), or 1 (key debug messages) to 4 (all debug messages). SBLIM_TRACE_FILE By default, SBLIM provider outputs its trace messages to STDERR. Setting this variable causes the trace messages to be written to a specied le instead. 35.3.2 Command Line Options sfcbd , the SFCB daemon, has several command line options that switch particular runtime features on or o. Enter these options when SFCB daemon starts. -c, --config-file = FILE When SFCB daemon starts, it reads its conguration from /etc/sfcb/sfcb.cfg by default. With this option, you can specify an alternative conguration le. -d, --daemon Forces sfcbd and its child processes to run in the background. -s, --collect-stats Turns on runtime statistics collecting. Various sfcbd runtime statistics will be written to the sfcbStat le in the current working directory. By default, no statistics are collected. -l, --syslog-level = LOGLEVEL Species the level of verbosity for the system logging facility. LOGLEVEL can be one of LOG_INFO, LOG_DEBUG, or LOG_ERR, which is the default. 522 Command Line Options SLES 12 SP4-k, --color-trace = LOGLEVEL Prints trace output in a dierent color per process for easier debugging. -t, --trace-components = NUM Activates component-level tracing messages, where NUM is an OR-ed bitmask integer that denes which component to trace. After you specify -t ? , it lists all the components and their associated integer bitmask: tux > sfcbd -t ? --- Traceable Components: Int Hex --- providerMgr: 1 0x0000001 --- providerDrv: 2 0x0000002 --- cimxmlProc: 4 0x0000004 --- httpDaemon: 8 0x0000008 --- upCalls: 16 0x0000010 --- encCalls: 32 0x0000020 --- ProviderInstMgr: 64 0x0000040 --- providerAssocMgr: 128 0x0000080 --- providers: 256 0x0000100 --- indProvider: 512 0x0000200 --- internalProvider: 1024 0x0000400 --- objectImpl: 2048 0x0000800 --- xmlIn: 4096 0x0001000 --- xmlOut: 8192 0x0002000 --- sockets: 16384 0x0004000 --- memoryMgr: 32768 0x0008000 --- msgQueue: 65536 0x0010000 --- xmlParsing: 131072 0x0020000 --- responseTiming: 262144 0x0040000 --- dbpdaemon: 524288 0x0080000 --- slp: 1048576 0x0100000 A useful value that reveals the internal functions of sfcbd but does not generate too many messages, is -t 2019 . 35.3.3 SFCB Configuration File SFCB reads its runtime conguration from conguration le /etc/sfcb/sfcb.cfg after starting up. This behavior can be overridden using -c option at start-up. The conguration le contains option : VALUE pairs, one per line. When making changes to this le, you can use any text editor that saves the le in a format that is native to the environment you are using. 523 SFCB Configuration File SLES 12 SP4Any setting that has the options commented out with a number sign (#) uses the default setting. The following list of options may not be complete. See the content of /etc/sfcb/sfcb.cfg and /usr/share/doc/packages/sblim-sfcb/README for their complete list. 35.3.3.1 httpPort Purpose Species the local port value that sfcbd should listen to receive HTTP (insecure) requests from CIM clients. Default is 5988 . Syntax httpPort: PORT_NUMBER 35.3.3.2 enableHttp Purpose Species whether SFCB should accept HTTP client connections. Default is false . Syntax enableHttp: OPTION Option Description true Enables HTTP connections. false Disables HTTP connections. 524 SFCB Configuration File SLES 12 SP435.3.3.3 httpProcs Purpose Species the maximum number of simultaneous HTTP client connections before new incoming HTTP requests are blocked. Default is 8 . Syntax httpProcs: MAX_NUMBER_OF_CONNECTIONS 35.3.3.4 httpUserSFCB, httpUser Purpose These options control what user the HTTP server will run under. If httpUserSFCB is true , HTTP will run under the same user as the SFCB main process. If it is false the user name specied for httpUser will be used. This setting is used for both HTTP and HTTPS servers. httpUser must be specied if httpUserSFCB is set to false . the default is true . Syntax httpUserSFCB: true 35.3.3.5 httpLocalOnly Purpose Species whether to limit HTTP requests to localhost only. Default is false . Syntax httpLocalOnly: false 525 SFCB Configuration File SLES 12 SP435.3.3.6 httpsPort Purpose Species the local port value where sfcbd listens for HTTPS requests from CIM clients. Default is 5989 . Syntax httpsPort: port_number 35.3.3.7 enableHttps Purpose Species if SFCB will accept HTTPS client connections. Default is true . Syntax enableHttps: option Option Description true Enables HTTPS connections. false Disables HTTPS connections. 35.3.3.8 httpsProcs Purpose Species the maximum number of simultaneous HTTPS client connections before new incoming HTTPS requests are blocked. Default is 8 . 526 SFCB Configuration File SLES 12 SP4Syntax httpsProcs:   MAX_NUMBER_OF_CONNECTIONS 35.3.3.9 enableInterOp Purpose Species if SFCB will provide the interop namespace for indication support. Default is true . Syntax enableInterOp:   OPTION Option Description true Enables interop namespace. false Disables interop namespace. 35.3.3.10 provProcs Purpose Species the maximum number of simultaneous provider processes. After this point, if a new incoming request requires loading a new provider, then one of the existing providers will rst be automatically unloaded. Default is 32 . Syntax provProcs:   MAX_NUMBER_OF_PROCS 527 SFCB Configuration File SLES 12 SP435.3.3.11 doBasicAuth Purpose Switches basic authentication on or o based on the client user identier before it accepts the request. Default value is true which means that basic client authentication is performed. Syntax doBasicAuth:   OPTION Option Description true Enables basic authentication. false Disables basic authentication. 35.3.3.12 basicAuthLib Purpose Species the local library name. The SFCB server loads the library to authenticate the client user identier. Default is sfcBasicPAMAuthentication . Syntax provProcs:   MAX_NUMBER_OF_PROCS 35.3.3.13 useChunking Purpose This option switches the use of HTTP/HTTPS “chunking” on or o. If switched on, the server will return large volumes of response data to the client in smaller “chunks”, rather than buer the data and send it back all in one chunk. Default is true . 528 SFCB Configuration File SLES 12 SP4Syntax useChunking:   OPTION Option Description true Enables HTTP/HTTPS data chunking. false Disables HTTP/HTTPS data chunking. 35.3.3.14 keepaliveTimeout Purpose Species the maximum time in seconds that SFCB HTTP process waits between two requests on one connection before it terminates. Setting it to 0 disables HTTP keep-alive. Default is 0 . Syntax keepaliveTimeout:   SECS 35.3.3.15 keepaliveMaxRequest Purpose Species the maximum number of consecutive requests on one connection. Setting it to 0 disables HTTP keep-alive. Default value is 10 . Syntax keepaliveMaxRequest:   NUMBER_OF_CONNECTIONS 529 SFCB Configuration File SLES 12 SP435.3.3.16 registrationDir Purpose Species the registration directory, which contains the provider registration data, the staging area, and the static repository. Default is /var/lib/sfcb/registration . Syntax registrationDir:   DIR 35.3.3.17 providerDirs Purpose Species a space-separated list of directories where SFCB is searching for provider libraries. Default is /usr/lib64 /usr/lib64 /usr/lib64/cmpi . Syntax providerDirs:   DIR 35.3.3.18 providerSampleInterval Purpose Species the interval in seconds at which the provider manager is checking for idle providers. Default is 30 . Syntax providerSampleInterval:   SECS 530 SFCB Configuration File SLES 12 SP435.3.3.19 providerTimeoutInterval Purpose Species the interval in seconds before an idle provider gets unloaded by the provider manager. Default is 60 . Syntax providerTimeoutInterval:   SECS 35.3.3.20 providerAutoGroup Purpose If the provider registration le does not specify any other group, and the option is set to true , all providers in the same shared library are executed in the same process. Syntax providerAutoGroup:   OPTION Option Description true Enables grouping of providers. false Disables grouping of providers. 35.3.3.21 sslCertificateFilePath Purpose Species the name of the le that contains the server certicate. The le must be in PEM (Privacy Enhanced Mail, RFC 1421 and RFC 1424) format. This le is only required if enableHttps is set to true . Default is /etc/sfcb/server.pem . 531 SFCB Configuration File SLES 12 SP4Syntax sslCertificateFilePath:   PATH 35.3.3.22 sslKeyFilePath Purpose Species the name of the le that contains the private key for the server certicate. The le must be in PEM format and may not be protected by passphrase. This le is only required if enableHttps is set to true . Default is /etc/sfcb/file.pem . Syntax sslKeyFilePath:   PATH 35.3.3.23 sslClientTrustStore Purpose Species the name of the le that contains either the CA or self-signed certicates of the clients. This le must be in PEM format and is only required if sslClientCertificate is set to accept or require . Default is /etc/sfcb/client.pem . Syntax sslClientTrustStore:   PATH 532 SFCB Configuration File SLES 12 SP435.3.3.24 sslClientCertificate Purpose Species the way SFCB handles client certicate based authentication. If set to ignore , it will not request a certicate from the client. If set to accept it will request a certicate from the client but will not fail if the client does not present one. If set to require , it will refuse the client connection if the client does not present a certicate. Default value is ignore . Syntax sslClientCertificate:   OPTION Option Description ignore Disables requesting a client certicate. accept Disables requesting a client certicate. Will not fail if no certicate is present. require Refuses the client connection without a valid certicate. 35.3.3.25 certificateAuthLib Purpose Species the name of the local library to request for the user authentication based on client certicate. This is only requested if sslClientCertificate is not set to ignore . Default value is sfcCertificateAuthentication . Syntax certificateAuthLib:   FILE 533 SFCB Configuration File SLES 12 SP435.3.3.26 traceLevel Purpose Species the trace level for SFCB. You can override it by setting environment variable SFCB_TRACE_LEVEL . Default value is 0 . Syntax traceLevel:   NUM_LEVEL 35.3.3.27 traceMask Purpose Species the trace mask for SFCB. you can override it by the command line option --trace- components . Default value is 0 . Syntax traceMask:   MASK 35.3.3.28 traceFile Purpose Species the trace le for SFCB. You can override it by setting environment variable SFCB_TRACE_FILE . Default value is stderr (standard error output). Syntax traceFile:   OUTPUT 534 SFCB Configuration File SLES 12 SP435.4 Advanced SFCB Tasks This chapter covers more advanced topics related to SFCB usage. To understand them, you need to have basic knowledge of the Linux le system and experience with the Linux command line. This chapter includes the following tasks: Installing CMPI providers Testing SFCB Using wbemcli CIM client 35.4.1 Installing CMPI Providers To install a CMPI provider, you need to make sure that its shared library is copied into one of the directories specied by providerDirs conguration option, see Section 35.3.3.17, “providerDirs”. The provider must also be properly registered using sfcbstage and sfcbrepos commands. The provider package is usually prepared for SFCB, so that its installation takes care of the proper registration. Most SBLIM providers are prepared for SFCB. 35.4.1.1 Class Repository Class repository is a place where SFCB stores information about CIM classes. It usually consists of a directory tree with namespace components. Typical CIM namespaces are root/cimv2 or root/interop , which respectively translate to the class repository directory path on the le system /var/lib/sfcb/registration/repository/root/cimv2 and /var/lib/sfcb/registration/repository/root/interop Each namespace directory contains the le classSchemas . The le has a compiled binary representation of all the CIM classes registered under that namespace. It also contains necessary information about their CIM superclasses. 535 Advanced SFCB Tasks SLES 12 SP4In addition, each namespace directory may contain a le qualifiers which contains all qualiers for the namespace. When sfcbd restarts, the class provider will scan the directory /var/lib/sfcb/registration/repository/ and all its subdirectories to determine the registered namespaces. Then classSchemas les are decoded and the class hierarchy for each namespace is built. 35.4.1.2 Adding New Classes SFCB cannot make live CIM class manipulations. You need to add, change or remove classes oine and restart SFCB service with systemctl restart sfcb to register the changes. To store providers class and registration information, SFCB uses a place called staging area. On SUSE® Linux Enterprise Server systems, it is the directory structure under /var/lib/sfcb/ stage/ . To add a new provider, you need to: Copy the provider class denition les to the ./mofs subdirectory of staging area directory ( /var/lib/sfcb/stage/mofs ). Copy a registration le which contains the name of the class or classes and type of provider, and the name of the executable library le into the ./regs subdirectory. There are two default “mof” (class denition) les in the staging directory: indication.mof and interop.mof . MOF les under the root stage directory /var/lib/sfcb/stage/mofs will be copied into each namespace after running sfcbrepos command. The interop.mof will only be compiled into the interop namespace. The directory layout may look like the following example: tux > ls /var/lib/sfcb/stage default.reg mofs regs tux > ls /var/lib/sfcb/stage/mofs indication.mof root tux > ls /var/lib/sfcb/stage/mofs/root cimv2 interop suse virt tux > ls -1 /var/lib/sfcb/stage/mofs/root/cimv2 | less Linux_ABIParameter.mof 536 Installing CMPI Providers SLES 12 SP4Linux_BaseIndication.mof Linux_Base.mof Linux_DHCPElementConformsToProfile.mof Linux_DHCPEntity.mof [..] OMC_StorageSettingWithHints.mof OMC_StorageVolumeDevice.mof OMC_StorageVolume.mof OMC_StorageVolumeStorageSynchronized.mof OMC_SystemStorageCapabilities.mof tux > ls -1 /var/lib/sfcb/stage/mofs/root/interop ComputerSystem.mof ElementConformsToProfile.mof HostSystem.mof interop.mof Linux_DHCPElementConformsToProfile.mof [..] OMC_SMIElementSoftwareIdentity.mof OMC_SMISubProfileRequiresProfile.mof OMC_SMIVolumeManagementSoftware.mof ReferencedProfile.mof RegisteredProfile.mof tux > ls -1 /var/lib/sfcb/stage/regs AllocationCapabilities.reg Linux_ABIParameter.reg Linux_BaseIndication.reg Linux_DHCPGlobal.reg Linux_DHCPRegisteredProfile.reg [..] OMC_Base.sfcb.reg OMC_CopyServices.sfcb.reg OMC_PowerManagement.sfcb.reg OMC_Server.sfcb.reg RegisteredProfile.reg tux > cat /var/lib/sfcb/stage/regs/Linux_DHCPRegisteredProfile.reg [Linux_DHCPRegisteredProfile] provider: Linux_DHCPRegisteredProfileProvider location: cmpiLinux_DHCPRegisteredProfile type: instance namespace: root/interop # [Linux_DHCPElementConformsToProfile] provider: Linux_DHCPElementConformsToProfileProvider location: cmpiLinux_DHCPElementConformsToProfile 537 Installing CMPI Providers SLES 12 SP4type: instance association namespace: root/cimv2 # [Linux_DHCPElementConformsToProfile] provider: Linux_DHCPElementConformsToProfileProvider location: cmpiLinux_DHCPElementConformsToProfile type: instance association namespace: root/interop SFCB uses a custom provider registration le for each provider. Note: SBLIM Providers Registration Files All SBLIM providers on the SBLIM Web site already include a registration le that is used to generate the .reg le for SFCB. The format of SFCB registration le is: [] provider: location: type: [instance] [association] [method] [indication] group: unload: never namespace: ... where: The CIM class name (required) The CMPI provider name (required) The name of the provider library (required) type The type of the provider (required). This can be any combination of: instance , association , method or indication . 538 Installing CMPI Providers SLES 12 SP4Multiple providers can be grouped together and run under a single process to further minimize runtime resources. All providers registered under the same will be executed under the same process. By default each provider will be run as a separate process. unload Species the unload policy for the provider. Currently the only supported option is never , which species that the provider will not be monitored for idle times and will never be unloaded. By default each provider will be unloaded when its idle times exceed the value specied in the conguration le. namespace List of namespaces for which this provider can be executed. This is required, although for most providers this will be root/cimv2 . Once all the class denitions and provider registration les are stored in the staging area, you need to rebuild the SFCB class repository with the command sfcbrepos -f . You can add, change or remove classes this way. After rebuilding the class repository, restart SFCB with command systemctl restart sfcb . Alternatively, the SFCB package contains a utility that will copy provider class mof les and registration les to the correct locations in the staging area. sfcbstage -r [provider.reg] [class1.mof] [class2.mof] ... After running this command you still need to rebuild the class repository and restart SFCB service. 35.4.2 Testing SFCB The SFCB package includes two testing scripts: wbemcat and xmltest . wbemcat sends raw CIM-XML data via HTTP protocol to the specied SFCB host (localhost by default) listening on port 5988. Then it displays the returned results. The following le contains the CIM-XML representation of a standard EnumerateClasses request: 539 Testing SFCB SLES 12 SP4 TRUE FALSE FALSE TRUE Sending this request to SFCB CIMOM returns a list of all supported classes for which there is a registered provider. Suppose you save the le as cim_xml_test.xml . tux > wbemcat cim_xml_test.xml | less HTTP/1.1 200 OK Content-Type: application/xml; charset="utf-8" Content-Length: 337565 Cache-Control: no-cache CIMOperation: MethodResponse [..] 540 Testing SFCB SLES 12 SP4 The classes listed will vary depending on what providers are installed on your system. The second script xmltest is also used to send a raw CIM-XML test le to the SFCB CIMOM. It then compares the returned results against a previously saved “OK” result le. If there does not yet exist a corresponding “OK” le, it will be created for later use: tux > xmltest cim_xml_test.xml Running test cim_xml_test.xml ... OK Saving response as cim_xml_test.OK root # xmltest cim_xml_test.xml Running test cim_xml_test.xml ... Passed 35.4.3 Command Line CIM Client: wbemcli In addition to wbemcat and xmltest , the SBLIM project includes a more advanced command line CIM client wbemcli . The client is used to send CIM requests to SFCB server and display returned results. It is independent of CIMOM library and can be used with all WBEM compliant implementations. For example, if you need to list all the classes implemented by SBLIM providers registered to your SFCB, send the “EnumerateClasses” (ec) request to SFCB: tux > wbemcli -dx ec http://localhost/root/cimv2 To server: \ \ TRUE \ FALSE FALSE \ TRUE \ From server: Content-Type: application/xml; charset="utf-8" From server: Content-Length: 337565 541 Command Line CIM Client: wbemcli SLES 12 SP4From server: Cache-Control: no-cache From server: CIMOperation: MethodResponse From server: [..] 0 0 [..] The -dx option shows you the actual XML sent to SFCB by wbemcli and the actual XML received. In the above example, the rst of many returned classes was CIM_ResourcePool followed by Linux_ReiserFileSystem . Similar entries will appear for all of the other registered classes. If you omit the -dx option, wbemcli will display only a compact representation of the returned data: tux > wbemcli ec http://localhost/root/cimv2 localhost:5988/root/cimv2:CIM_ResourcePool Generation=,ElementName=, \ Description=,Caption=,InstallDate=,Name=,OperationalStatus=, \ StatusDescriptions=,Status=,HealthState=,PrimaryStatus=, \ 542 Command Line CIM Client: wbemcli SLES 12 SP4DetailedStatus=,OperatingStatus=,CommunicationStatus=,InstanceID=, \ PoolID=,Primordial=,Capacity=,Reserved=,ResourceType=, \ OtherResourceType=,ResourceSubType=, \AllocationUnits= localhost:5988/root/cimv2:Linux_ReiserFileSystem FSReservedCapacity=, \ TotalInodes=,FreeInodes=,ResizeIncrement=,IsFixedSize=,NumberOfFiles=, \ OtherPersistenceType=,PersistenceType=,FileSystemType=,ClusterSize=, \ MaxFileNameLength=,CodeSet=,CasePreserved=,CaseSensitive=, \ CompressionMethod=,EncryptionMethod=,ReadOnly=,AvailableSpace=, \ FileSystemSize=,BlockSize=,Root=,Name=,CreationClassName=,CSName=, \ CSCreationClassName=,Generation=,ElementName=,Description=,Caption=, \ InstanceID=,InstallDate=,OperationalStatus=,StatusDescriptions=, \ Status=,HealthState=,PrimaryStatus=,DetailedStatus=,OperatingStatus= \ ,CommunicationStatus=,EnabledState=,OtherEnabledState=,RequestedState= \ ,EnabledDefault=,TimeOfLastStateChange=,AvailableRequestedStates=, \ TransitioningToState=,PercentageSpaceUse= [..] 35.5 For More Information FOR MORE DETAILS ABOUT WBEM AND SFCB, SEE THE FOLLOWING SOURCES: https://www.dmtf.org Distributed Management Task Force Web site https://www.dmtf.org/standards/wbem/ Web-Based Enterprise Management (WBEM) Web site https://www.dmtf.org/standards/cim/ Common Information Model (CIM) Web site http://sblim.sourceforge.net/wiki/index.php/Main_Page Standards Based Linux Instrumentation (SBLIM) Web site http://sblim.sourceforge.net/wiki/index.php/Sfcb Small Footprint CIM Broker (SFCB) Web site http://sblim.sourceforge.net/wiki/index.php/Providers SBLIM providers packages 543 For More Information SLES 12 SP4V Mobile Computers 36 Mobile Computing with Linux 545 37 Using NetworkManager 556 38 Power Management 56636 Mobile Computing with Linux Mobile computing is mostly associated with laptops, PDAs and cellular phones (and the data exchange between them). Mobile hardware components, such as external hard disks, ash disks, or digital cameras, can be connected to laptops or desktop systems. A number of software components are involved in mobile computing scenarios and some applications are tailor-made for mobile use. 36.1 Laptops The hardware of laptops diers from that of a normal desktop system. This is because criteria like exchangeability, space requirements and power consumption must be taken into account. The manufacturers of mobile hardware have developed standard interfaces like PCMCIA (Personal Computer Memory Card International Association), Mini PCI and Mini PCIe that can be used to extend the hardware of laptops. The standards cover memory cards, network interface cards, and external hard disks. 36.1.1 Power Conservation The inclusion of energy-optimized system components during laptop manufacturing contributes to their suitability for use without access to the electrical power grid. Their contribution to conservation of power is at least as important as that of the operating system. SUSE® Linux Enterprise Server supports various methods that control the power consumption of a laptop and have varying eects on the operating time under battery power. The following list is in descending order of contribution to power conservation: Throttling the CPU speed. Switching o the display illumination during pauses. Manually adjusting the display illumination. Disconnecting unused, hotplug-enabled accessories (USB CD-ROM, external mouse, unused PCMCIA cards, Wi-Fi, etc.). Spinning down the hard disk when idling. 545 Laptops SLES 12 SP4Detailed background information about power management in SUSE Linux Enterprise Server is provided in Chapter 38, Power Management. 36.1.2 Integration in Changing Operating Environments Your system needs to adapt to changing operating environments when used for mobile computing. Many services depend on the environment and the underlying clients must be recongured. SUSE Linux Enterprise Server handles this task for you. FIGURE 36.1: INTEGRATING A MOBILE COMPUTER IN AN EXISTING ENVIRONMENT 546 Integration in Changing Operating Environments SLES 12 SP4The services aected in the case of a laptop commuting back and forth between a small home network and an oce network are: Network This includes IP address assignment, name resolution, Internet connectivity and connectivity to other networks. Printing A current database of available printers and an available print server must be present, depending on the network. E-Mail and Proxies As with printing, the list of the corresponding servers must be current. X (Graphical Environment) If your laptop is temporarily connected to a projector or an external monitor, dierent display congurations must be available. SUSE Linux Enterprise Server oers several ways of integrating laptops into existing operating environments: NetworkManager NetworkManager is especially tailored for mobile networking on laptops. It provides a means to easily and automatically switch between network environments or dierent types of networks such as mobile broadband (such as GPRS, EDGE, or 3G), wireless LAN, and Ethernet. NetworkManager supports WEP and WPA-PSK encryption in wireless LANs. It also supports dial-up connections. The GNOME desktop includes a front-end for NetworkManager. For more information, see Section 37.3, “Configuring Network Connections”. TABLE 36.1: USE CASES FOR NETWORKMANAGER My computer… Use NetworkManager is a laptop Yes is sometimes attached to dierent Yes networks provides network services (such as DNS or No DHCP) 547 Integration in Changing Operating Environments SLES 12 SP4My computer… Use NetworkManager only uses a static IP address No Use the YaST tools to congure networking whenever NetworkManager should not handle network conguration. Tip: DNS Configuration and Various Types of Network Connections If you travel frequently with your laptop and change dierent types of network connections, NetworkManager works ne when all DNS addresses are assigned correctly assigned with DHCP. If some connections use static DNS address(es), add it to the NETCONFIG_DNS_STATIC_SERVERS option in /etc/sysconfig/network/ config . SLP The service location protocol (SLP) simplies the connection of a laptop to an existing network. Without SLP, the administrator of a laptop usually requires detailed knowledge of the services available in a network. SLP broadcasts the availability of a certain type of service to all clients in a local network. Applications that support SLP can process the information dispatched by SLP and be congured automatically. SLP can also be used to install a system, minimizing the eort of searching for a suitable installation source. Find detailed information about SLP in Chapter 31, SLP. 36.1.3 Software Options There are various task areas in mobile use that are covered by dedicated software: system monitoring (especially the battery charge), data synchronization, and wireless communication with peripherals and the Internet. The following sections cover the most important applications that SUSE Linux Enterprise Server provides for each task. 548 Software Options SLES 12 SP436.1.3.1 System Monitoring Two system monitoring tools are provided by SUSE Linux Enterprise Server: Power Management Power Management is an application that lets you adjust the energy saving related behavior of the GNOME desktop. You can typically access it via Computer Control Center System Power Management. System Monitor The System Monitor gathers measurable system parameters into one monitoring environment. It presents the output information in three tabs by default. Processes gives detailed information about currently running processes, such as CPU load, memory usage, or process ID number and priority. The presentation and ltering of the collected data can be customized—to add a new type of process information, left-click the process table header and choose which column to hide or add to the view. It is also possible to monitor dierent system parameters in various data pages or collect the data of various machines in parallel over the network. The Resources tab shows graphs of CPU, memory and network history and the File System tab lists all partitions and their usage. 36.1.3.2 Synchronizing Data When switching between working on a mobile machine disconnected from the network and working at a networked workstation in an oce, it is necessary to keep processed data synchronized across all instances. This could include e-mail folders, directories and individual les that need to be present for work on the road and at the oce. The solution in both cases is as follows: Synchronizing E-Mail Use an IMAP account for storing your e-mails in the oce network. Then access the e-mails from the workstation using any disconnected IMAP-enabled e-mail client, like Mozilla Thunderbird or Evolution as described in Book “GNOME User Guide”. The e-mail client must be congured so that the same folder is always accessed for Sent messages . This ensures that all messages are available along with their status information after the synchronization process has completed. Use an SMTP server implemented in the mail client for sending messages instead of the system-wide MTA postx or sendmail to receive reliable feedback about unsent mail. 549 Software Options SLES 12 SP4Synchronizing Files and Directories There are several utilities suitable for synchronizing data between a laptop and a workstation. One of the most widely used is a command-line tool called rsync . For more information, see its manual page ( man 1 rsync ). 36.1.3.3 Wireless Communication: Wi-Fi With the largest range of these wireless technologies, Wi-Fi is the only one suitable for the operation of large and sometimes even spatially separate networks. Single machines can connect with each other to form an independent wireless network or access the Internet. Devices called access points act as base stations for Wi-Fi-enabled devices and act as intermediaries for access to the Internet. A mobile user can switch among access points depending on location and which access point is oering the best connection. Like in cellular telephony, a large network is available to Wi-Fi users without binding them to a specic location for accessing it. Wi-Fi cards communicate using the 802.11 standard, prepared by the IEEE organization. Originally, this standard provided for a maximum transmission rate of 2 Mbit/s. Meanwhile, several supplements have been added to increase the data rate. These supplements dene details such as the modulation, transmission output, and transmission rates (see Table 36.2, “Overview of Various Wi-Fi Standards”). Additionally, many companies implement hardware with proprietary or draft features. TABLE 36.2: OVERVIEW OF VARIOUS WI-FI STANDARDS Name (802.11) Frequency (GHz) Maximum Note Transmission Rate (Mbit/s) a 5 54 Less interference- prone b 2.4 11 Less common g 2.4 54 Widespread, backward-compatible with 11b n 2.4 and/or 5 300 Common 550 Software Options SLES 12 SP4Name (802.11) Frequency (GHz) Maximum Note Transmission Rate (Mbit/s) ac 5 up to ~865 Expected to be common in 2015 ad 60 up to appr. 7000 Released 2012, currently less common; not supported in SUSE Linux Enterprise Server 802.11 Legacy cards are not supported by SUSE® Linux Enterprise Server. Most cards using 802.11 a/b/g/n are supported. New cards usually comply with the 802.11n standard, but cards using 802.11g are still available. 36.1.3.3.1 Operating Modes In wireless networking, various techniques and congurations are used to ensure fast, high- quality, and secure connections. Usually your Wi-Fi card operates in managed mode. However, dierent operating types need dierent setups. Wireless networks can be classied into four network modes: Managed Mode (Infrastructure Mode), via Access Point (default mode) Managed networks have a managing element: the access point. In this mode (also called infrastructure or default mode), all connections of the Wi-Fi stations in the network run through the access point, which may also serve as a connection to an Ethernet. To make sure only authorized stations can connect, various authentication mechanisms (WPA, etc.) are used. This is also the main mode that consumes the least amount of energy. Ad-hoc Mode (Peer-to-Peer Network) Ad-hoc networks do not have an access point. The stations communicate directly with each other, therefore an ad-hoc network is usually slower than a managed network. However, the transmission range and number of participating stations are greatly limited in ad-hoc networks. They also do not support WPA authentication. Additionally, not all cards support ad-hoc mode reliably. 551 Software Options SLES 12 SP4Master Mode In master mode, your Wi-Fi card is used as the access point, assuming your card supports this mode. Find out the details of your Wi-Fi card at http://linux-wless.passys.nl . Mesh Mode Wireless mesh networks are organized in a mesh topology. A wireless mesh network''s connection is spread among all wireless mesh nodes. Each node belonging to this network is connected to other nodes to share the connection, possibly over a large area. (Not supported in SLE12). 36.1.3.3.2 Authentication Because a wireless network is much easier to intercept and compromise than a wired network, the various standards include authentication and encryption methods. Old Wi-Fi cards support only WEP (Wired Equivalent Privacy). However, because WEP has proven to be insecure, the Wi-Fi industry has dened an extension called WPA, which is supposed to eliminate the weaknesses of WEP. WPA, sometimes synonymous with WPA2, should be the default authentication method. Usually the user cannot choose the authentication method. For example, when a card operates in managed mode the authentication is set by the access point. NetworkManager shows the authentication method. 36.1.3.3.3 Encryption There are various encryption methods to ensure that no unauthorized person can read the data packets that are exchanged in a wireless network or gain access to the network: WEP (defined in IEEE 802.11) This standard uses the RC4 encryption algorithm, originally with a key length of 40 bits, later also with 104 bits. Often, the length is declared as 64 bits or 128 bits, depending on whether the 24 bits of the initialization vector are included. However, this standard has some weaknesses. Attacks against the keys generated by this system may be successful. Nevertheless, it is better to use WEP than not to encrypt the network. Some vendors have implemented the non-standard “Dynamic WEP”. It works exactly as WEP and shares the same weaknesses, except that the key is periodically changed by a key management service. 552 Software Options SLES 12 SP4TKIP (defined in WPA/IEEE 802.11i) This key management protocol dened in the WPA standard uses the same encryption algorithm as WEP, but eliminates its weakness. Because a new key is generated for every data packet, attacks against these keys are fruitless. TKIP is used together with WPA-PSK. CCMP (defined in IEEE 802.11i) CCMP describes the key management. Usually, it is used in connection with WPA-EAP, but it can also be used with WPA-PSK. The encryption takes place according to AES and is stronger than the RC4 encryption of the WEP standard. 36.1.3.4 Wireless Communication: Bluetooth Bluetooth has the broadest application spectrum of all wireless technologies. It can be used for communication between computers (laptops) and PDAs or cellular phones, as can IrDA. It can also be used to connect various computers within range. Bluetooth is also used to connect wireless system components, like a keyboard or a mouse. The range of this technology is, however, not sucient to connect remote systems to a network. Wi-Fi is the technology of choice for communicating through physical obstacles like walls. 36.1.3.5 Wireless Communication: IrDA IrDA is the wireless technology with the shortest range. Both communication parties must be within viewing distance of each other. Obstacles like walls cannot be overcome. One possible application of IrDA is the transmission of a le from a laptop to a cellular phone. The short path from the laptop to the cellular phone is then covered using IrDA. Long-range transmission of the le to the recipient is handled by the mobile network. Another application of IrDA is the wireless transmission of printing jobs in the oce. 36.1.4 Data Security Ideally, you protect data on your laptop against unauthorized access in multiple ways. Possible security measures can be taken in the following areas: Protection against Theft Always physically secure your system against theft whenever possible. Various securing tools (like chains) are available in retail stores. 553 Data Security SLES 12 SP4Strong Authentication Use biometric authentication in addition to standard authentication via login and password. SUSE Linux Enterprise Server supports ngerprint authentication. Securing Data on the System Important data should not only be encrypted during transmission, but also on the hard disk. This ensures its safety in case of theft. The creation of an encrypted partition with SUSE Linux Enterprise Server is described in Book “Security Guide”, Chapter 11 “Encrypting Partitions and Files”. Another possibility is to create encrypted home directories when adding the user with YaST. Important: Data Security and Suspend to Disk Encrypted partitions are not unmounted during a suspend to disk event. Thus, all data on these partitions is available to any party who manages to steal the hardware and issue a resume of the hard disk. Network Security Any transfer of data should be secured, no matter how the transfer is done. Find general security issues regarding Linux and networks in Book “Security Guide”, Chapter 1 “Security and Confidentiality”. 36.2 Mobile Hardware SUSE Linux Enterprise Server supports the automatic detection of mobile storage devices over FireWire (IEEE 1394) or USB. The term mobile storage device applies to any kind of FireWire or USB hard disk, ash disk, or digital camera. These devices are automatically detected and congured when they are connected with the system over the corresponding interface. The le manager of GNOME oers exible handling of mobile hardware items. To unmount any of these media safely, use the Unmount Volume (GNOME) feature of the le manager. For more details refer to Book “GNOME User Guide”. External Hard Disks (USB and FireWire) When an external hard disk is correctly recognized by the system, its icon appears in the le manager. Clicking the icon displays the contents of the drive. It is possible to create directories and les here and edit or delete them. To rename a hard disk, select 554 Mobile Hardware SLES 12 SP4the corresponding menu item from the right-click contextual menu. This name change is limited to display in the le manager. The descriptor by which the device is mounted in /media remains unaected. USB Flash Disks These devices are handled by the system like external hard disks. It is similarly possible to rename the entries in the le manager. 36.3 Cellular Phones and PDAs A desktop system or a laptop can communicate with a cellular phone via Bluetooth or IrDA. Some models support both protocols and some only one of the two. The usage areas for the two protocols and the corresponding extended documentation has already been mentioned in Section 36.1.3.3, “Wireless Communication: Wi-Fi”. The conguration of these protocols on the cellular phones themselves is described in their manuals. 36.4 For More Information The central point of reference for all questions regarding mobile devices and Linux is http:// tuxmobil.org/ . Various sections of that Web site deal with the hardware and software aspects of laptops, PDAs, cellular phones and other mobile hardware. A similar approach to that of http://tuxmobil.org/ is made by http://www.linux-on- laptops.com/ . Information about laptops and handhelds can be found here. SUSE maintains a mailing list in German dedicated to the subject of laptops. See http:// lists.opensuse.org/opensuse-mobile-de/ . On this list, users and developers discuss all aspects of mobile computing with SUSE Linux Enterprise Server. Postings in English are answered, but the majority of the archived information is only available in German. Use http://lists.opensuse.org/ opensuse-mobile/ for English postings. 555 Cellular Phones and PDAs SLES 12 SP437 Using NetworkManager NetworkManager is the ideal solution for laptops and other portable computers. It supports state-of-the-art encryption types and standards for network connections, including connections to 802.1X protected networks. 802.1X is the “IEEE Standard for Local and Metropolitan Area Networks—Port-Based Network Access Control”. With NetworkManager, you need not worry about conguring network interfaces and switching between wired or wireless networks when you are moving. NetworkManager can automatically connect to known wireless networks or manage several network connections in parallel—the fastest connection is then used as default. Furthermore, you can manually switch between available networks and manage your network connection using an applet in the system tray. Instead of only one connection being active, multiple connections may be active at once. This enables you to unplug your laptop from an Ethernet and remain connected via a wireless connection. 37.1 Use Cases for NetworkManager NetworkManager provides a sophisticated and intuitive user interface, which enables users to easily switch their network environment. However, NetworkManager is not a suitable solution in the following cases: Your computer provides network services for other computers in your network, for example, it is a DHCP or DNS server. Your computer is a Xen server or your system is a virtual system inside Xen. 37.2 Enabling or Disabling NetworkManager On laptop computers, NetworkManager is enabled by default. However, it can be at any time enabled or disabled in the YaST Network Settings module. 1. Run YaST and go to System Network Settings. 2. The Network Settings dialog opens. Go to the Global Options tab. 556 Use Cases for NetworkManager SLES 12 SP43. To congure and manage your network connections with NetworkManager: a. In the Network Setup Method eld, select User Controlled with NetworkManager. b. Click OK and close YaST. c. Congure your network connections with NetworkManager as described in Section 37.3, “Configuring Network Connections”. 4. To deactivate NetworkManager and control the network with your own conguration a. In the Network Setup Method eld, choose Controlled by wicked. b. Click OK. c. Set up your network card with YaST using automatic conguration via DHCP or a static IP address. Find a detailed description of the network conguration with YaST in Section 16.4, “Configuring a Network Connection with YaST”. 37.3 Configuring Network Connections After having enabled NetworkManager in YaST, congure your network connections with the NetworkManager front-end available in GNOME. It shows tabs for all types of network connections, such as wired, wireless, mobile broadband, DSL, and VPN connections. To open the network conguration dialog in GNOME, open the settings menu via the status menu and click the Network entry. Note: Availability of Options Depending on your system setup, you may not be allowed to congure connections. In a secured environment, some options may be locked or require root permission. Ask your system administrator for details. 557 Configuring Network Connections SLES 12 SP4FIGURE 37.1: GNOME NETWORK CONNECTIONS DIALOG PROCEDURE 37.1: ADDING AND EDITING CONNECTIONS 1. Open the NetworkManager conguration dialog. 2. To add a Connection: a. Click the + icon in the lower left corner. b. Select your preferred connection type and follow the instructions. c. When you are nished click Add. d. After having conrmed your changes, the newly congured network connection appears in the list of available networks you get by opening the Status Menu. 3. To edit a connection: a. Select the entry to edit. b. Click the gear icon to open the Connection Settings dialog. c. Insert your changes and click Apply to save them. d. To Make your connection available as system connection go to the Identity tab and set the check box Make available to other users. For more information about User and System Connections, see Section 37.4.1, “User and System Connections”. 558 Configuring Network Connections SLES 12 SP437.3.1 Managing Wired Network Connections If your computer is connected to a wired network, use the NetworkManager applet to manage the connection. 1. Open the Status Menu and click Wired to change the connection details or to switch it o. 2. To change the settings click Wired Settings and then click the gear icon. 3. To switch o all network connections, activate the Airplane Mode setting. 37.3.2 Managing Wireless Network Connections Visible wireless networks are listed in the GNOME NetworkManager applet menu under Wireless Networks. The signal strength of each network is also shown in the menu. Encrypted wireless networks are marked with a shield icon. PROCEDURE 37.2: CONNECTING TO A VISIBLE WIRELESS NETWORK 1. To connect to a visible wireless network, open the Status Menu and click Wi-Fi. 2. Click Turn On to enable it. 3. Click Select Network, select your Wi-Fi Network and click Connect. 4. If the network is encrypted, a conguration dialog opens. It shows the type of encryption the network uses and text boxes for entering the login credentials. PROCEDURE 37.3: CONNECTING TO AN INVISIBLE WIRELESS NETWORK 1. To connect to a network that does not broadcast its service set identier (SSID or ESSID) and therefore cannot be detected automatically, open the Status Menu and click Wi-Fi. 2. Click Wi-Fi Settings to open the detailed settings menu. 3. Make sure your Wi-Fi is enabled and click Connect to Hidden Network. 4. In the dialog that opens, enter the SSID or ESSID in Network Name and set encryption parameters if necessary. A wireless network that has been chosen explicitly will remain connected as long as possible. If a network cable is plugged in during that time, any connections that have been set to Stay connected when possible will be connected, while the wireless connection remains up. 559 Managing Wired Network Connections SLES 12 SP437.3.3 Configuring Your Wi-Fi/Bluetooth Card as an Access Point If your Wi-Fi/Bluetooth card supports access point mode, you can use NetworkManager for the conguration. 1. Open the Status Menu and click Wi-Fi. 2. Click Wi-Fi Settings to open the detailed settings menu. 3. Click Use as Hotspot and follow the instructions. 4. Use the credentials shown in the resulting dialog to connect to the hotspot from a remote machine. 37.3.4 NetworkManager and VPN NetworkManager supports several Virtual Private Network (VPN) technologies. For each technology, SUSE Linux Enterprise Server comes with a base package providing the generic support for NetworkManager. In addition to that, you also need to install the respective desktop- specic package for your applet. OpenVPN To use this VPN technology, install: NetworkManager-openvpn NetworkManager-openvpn-gnome vpnc (Cisco AnyConnect) To use this VPN technology, install: NetworkManager-vpnc NetworkManager-vpnc-gnome PPTP (Point-to-Point Tunneling Protocol) To use this VPN technology, install: NetworkManager-pptp NetworkManager-pptp-gnome 560 Configuring Your Wi-Fi/Bluetooth Card as an Access Point SLES 12 SP4The following procedure describes how to set up your computer as an OpenVPN client using NetworkManager. Setting up other types of VPNs works analogously. Before you begin, make sure that the package NetworkManager-openvpn-gnome is installed and all dependencies have been resolved. PROCEDURE 37.4: SETTING UP OPENVPN WITH NETWORKMANAGER 1. Open the application Settings by clicking the status icons at the right end of the panel and clicking the wrench and screwdriver icon. In the window All Settings, choose Network. 2. Click the + icon. 3. Select VPN and then OpenVPN. 4. Choose the Authentication type. Depending on the setup of your OpenVPN server, choose Certicates (TLS) or Password with Certicates (TLS). 5. Insert the necessary values into the respective text boxes. For our example conguration, these are: Gateway The remote endpoint of the VPN server User name The user (only available when you have selected Password with Certicates (TLS)) Password The password for the user (only available when you have selected Password with Certicates (TLS)) User Certicate /etc/openvpn/client1.crt CA Certicate /etc/openvpn/ca.crt Private Key /etc/openvpn/client1.key 6. Finish the conguration with Add. 7. To enable the connection, in the Network panel of the Settings application click the switch button. Alternatively, click the status icons at the right end of the panel, click the name of your VPN and then Connect. 561 NetworkManager and VPN SLES 12 SP437.4 NetworkManager and Security NetworkManager distinguishes two types of wireless connections, trusted and untrusted. A trusted connection is any network that you explicitly selected in the past. All others are untrusted. Trusted connections are identied by the name and MAC address of the access point. Using the MAC address ensures that you cannot use a dierent access point with the name of your trusted connection. NetworkManager periodically scans for available wireless networks. If multiple trusted networks are found, the most recently used is automatically selected. NetworkManager waits for your selection in case that all networks are untrusted. If the encryption setting changes but the name and MAC address remain the same, NetworkManager attempts to connect, but rst you are asked to conrm the new encryption settings and provide any updates, such as a new key. If you switch from using a wireless connection to oine mode, NetworkManager blanks the SSID or ESSID. This ensures that the card is disconnected. 37.4.1 User and System Connections NetworkManager knows two types of connections: user and system connections. User connections are connections that become available to NetworkManager when the rst user logs in. Any required credentials are asked from the user and when the user logs out, the connections are disconnected and removed from NetworkManager. Connections that are dened as system connection can be shared by all users and are made available right after NetworkManager is started—before any users log in. In case of system connections, all credentials must be provided at the time the connection is created. Such system connections can be used to automatically connect to networks that require authorization. For information how to congure user or system connections with NetworkManager, refer to Section 37.3, “Configuring Network Connections”. 37.4.2 Storing Passwords and Credentials If you do not want to re-enter your credentials each time you want to connect to an encrypted network, you can use the GNOME Keyring Manager to store your credentials encrypted on the disk, secured by a master password. 562 NetworkManager and Security SLES 12 SP4NetworkManager can also retrieve its certicates for secure connections (for example, encrypted wired, wireless or VPN connections) from the certicate store. For more information, refer to Book “Security Guide”, Chapter 12 “Certificate Store”. 37.5 Frequently Asked Questions In the following, nd some frequently asked questions about conguring special network options with NetworkManager. Q: 1. How to tie a connection to a specific device? By default, connections in NetworkManager are device type-specic: they apply to all physical devices with the same type. If more than one physical device per connection type is available (for example, your machine is equipped with two Ethernet cards), you can tie a connection to a certain device. To do this in GNOME, rst look up the MAC address of your device (use the Connection Information available from the applet, or use the output of command line tools like nm- tool or wicked show all ). Then start the dialog for conguring network connections and choose the connection you want to modify. On the Wired or Wireless tab, enter the MAC Address of the device and conrm your changes. Q: 2. How to specify a certain access point in case multiple access points with the same ESSID are detected? When multiple access points with dierent wireless bands (a/b/g/n) are available, the access point with the strongest signal is automatically chosen by default. To override this, use the BSSID eld when conguring wireless connections. The Basic Service Set Identier (BSSID) uniquely identies each Basic Service Set. In an infrastructure Basic Service Set, the BSSID is the MAC address of the wireless access point. In an independent (ad-hoc) Basic Service Set, the BSSID is a locally administered MAC address generated from a 46-bit random number. Start the dialog for conguring network connections as described in Section  37.3, “Configuring Network Connections”. Choose the wireless connection you want to modify and click Edit. On the Wireless tab, enter the BSSID. Q: 3. How to share network connections to other computers? 563 Frequently Asked Questions SLES 12 SP4The primary device (the device which is connected to the Internet) does not need any special conguration. However, you need to congure the device that is connected to the local hub or machine as follows: 1. Start the dialog for conguring network connections as described in Section 37.3, “Configuring Network Connections”. Choose the connection you want to modify and click Edit. Switch to the IPv4 Settings tab and from the Method drop-down box, activate Shared to other computers. That will enable IP trac forwarding and run a DHCP server on the device. Conrm your changes in NetworkManager. 2. As the DCHP server uses port 67 , make sure that it is not blocked by the rewall: On the machine sharing the connections, start YaST and select Security and Users Firewall. Switch to the Allowed Services category. If DCHP Server is not already shown as Allowed Service, select DCHP Server from Services to Allow and click Add. Conrm your changes in YaST. Q: 4. How to provide static DNS information with automatic (DHCP, PPP, VPN) addresses? In case a DHCP server provides invalid DNS information (and/or routes), you can override it. Start the dialog for conguring network connections as described in Section  37.3, “Configuring Network Connections”. Choose the connection you want to modify and click Edit. Switch to the IPv4 Settings tab, and from the Method drop-down box, activate Automatic (DHCP) addresses only. Enter the DNS information in the DNS Servers and Search Domains elds. To Ignore automatically obtained routes click Routes and activate the respective check box. Conrm your changes. Q: 5. How to make NetworkManager connect to password protected networks before a user logs in? Dene a system connection that can be used for such purposes. For more information, refer to Section 37.4.1, “User and System Connections”. 37.6 Troubleshooting Connection problems can occur. Some common problems related to NetworkManager include the applet not starting or a missing VPN option. Methods for resolving and preventing these problems depend on the tool used. NetworkManager Desktop Applet Does Not Start 564 Troubleshooting SLES 12 SP4The applets starts automatically if the network is set up for NetworkManager control. If the applet does not start, check if NetworkManager is enabled in YaST as described in Section 37.2, “Enabling or Disabling NetworkManager”. Then make sure that the NetworkManager-gnome package is also installed. If the desktop applet is installed but is not running for some reason, start it manually. If the desktop applet is installed but is not running for some reason, start it manually with the command nm-applet . NetworkManager Applet Does Not Include the VPN Option Support for NetworkManager, applets, and VPN for NetworkManager is distributed in separate packages. If your NetworkManager applet does not include the VPN option, check if the packages with NetworkManager support for your VPN technology are installed. For more information, see Section 37.3.4, “NetworkManager and VPN”. No Network Connection Available If you have congured your network connection correctly and all other components for the network connection (router, etc.) are also up and running, it sometimes helps to restart the network interfaces on your computer. To do so, log in to a command line as root and run systemctl restart wickeds . 37.7 For More Information More information about NetworkManager can be found on the following Web sites and directories: NetworkManager Project Page http://projects.gnome.org/NetworkManager/ Package Documentation Also check out the information in the following directories for the latest information about NetworkManager and the GNOME applet: /usr/share/doc/packages/NetworkManager/ , /usr/share/doc/packages/NetworkManager-gnome/ . 565 For More Information SLES 12 SP438 Power Management IBM Z The features and hardware described in this chapter do not exist on IBM z Systems, making this chapter irrelevant for these platforms. Power management is especially important on laptop computers, but is also useful on other systems. ACPI (Advanced Conguration and Power Interface) is available on all modern computers (laptops, desktops, and servers). Power management technologies require suitable hardware and BIOS routines. Most laptops and many modern desktops and servers meet these requirements. It is also possible to control CPU frequency scaling to save power or decrease noise. 38.1 Power Saving Functions Power saving functions are not only signicant for the mobile use of laptops, but also for desktop systems. The main functions and their use in ACPI are: Standby not supported. Suspend (to memory) This mode writes the entire system state to the RAM. Subsequently, the entire system except the RAM is put to sleep. In this state, the computer consumes very little power. The advantage of this state is the possibility of resuming work at the same point within a few seconds without having to boot and restart applications. This function corresponds to the ACPI state S3 . Hibernation (suspend to disk) In this operating mode, the entire system state is written to the hard disk and the system is powered o. There must be a swap partition at least as big as the RAM to write all the active data. Reactivation from this state takes about 30 to 90 seconds. The state prior to the suspend is restored. Some manufacturers oer useful hybrid variants of this mode, such as RediSafe in IBM Thinkpads. The corresponding ACPI state is S4 . In Linux, suspend to disk is performed by kernel routines that are independent from ACPI. 566 Power Saving Functions SLES 12 SP4Note: Changed UUID for Swap Partitions when Formatting via mkswap Do not reformat existing swap partitions with mkswap if possible. Reformatting with mkswap will change the UUID value of the swap partition. Either reformat via YaST (will update /etc/fstab ) or adjust /etc/fstab manually. Battery Monitor ACPI checks the battery charge status and provides information about it. Additionally, it coordinates actions to perform when a critical charge status is reached. Automatic Power-Off Following a shutdown, the computer is powered o. This is especially important when an automatic shutdown is performed shortly before the battery is empty. Processor Speed Control In connection with the CPU, energy can be saved in three dierent ways: frequency and voltage scaling (also known as PowerNow! or Speedstep), throttling and putting the processor to sleep (C-states). Depending on the operating mode of the computer, these methods can also be combined. 38.2 Advanced Configuration and Power Interface (ACPI) ACPI was designed to enable the operating system to set up and control the individual hardware components. ACPI supersedes both Power Management Plug and Play (PnP) and Advanced Power Management (APM). It delivers information about the battery, AC adapter, temperature, fan and system events, like “close lid” or “battery low.” The BIOS provides tables containing information about the individual components and hardware access methods. The operating system uses this information for tasks like assigning interrupts or activating and deactivating components. Because the operating system executes commands stored in the BIOS, the functionality depends on the BIOS implementation. The tables ACPI can detect and load are reported in journald. See Chapter 15, journalctl: Query the systemd Journal for more information on viewing the journal log messages. See Section 38.2.2, “Troubleshooting” for more information about troubleshooting ACPI problems. 567 Advanced Configuration and Power Interface (ACPI) SLES 12 SP438.2.1 Controlling the CPU Performance The CPU can save energy in three ways: Frequency and Voltage Scaling Throttling the Clock Frequency (T-states) Putting the Processor to Sleep (C-states) Depending on the operating mode of the computer, these methods can be combined. Saving energy also means that the system heats up less and the fans are activated less frequently. Frequency scaling and throttling are only relevant if the processor is busy, because the most economic C-state is applied anyway when the processor is idle. If the CPU is busy, frequency scaling is the recommended power saving method. Often the processor only works with a partial load. In this case, it can be run with a lower frequency. Usually, dynamic frequency scaling controlled by the kernel on-demand governor is the best approach. Throttling should be used as the last resort, for example, to extend the battery operation time despite a high system load. However, some systems do not run smoothly when they are throttled too much. Moreover, CPU throttling does not make sense if the CPU has little to do. For in-depth information, refer to Book “System Analysis and Tuning Guide”, Chapter 11 “Power Management”. 38.2.2 Troubleshooting There are two dierent types of problems. On one hand, the ACPI code of the kernel may contain bugs that were not detected in time. In this case, a solution will be made available for download. More often, the problems are caused by the BIOS. Sometimes, deviations from the ACPI specication are purposely integrated in the BIOS to circumvent errors in the ACPI implementation of other widespread operating systems. Hardware components that have serious errors in the ACPI implementation are recorded in a blacklist that prevents the Linux kernel from using ACPI for these components. The rst thing to do when problems are encountered is to update the BIOS. If the computer does not boot, one of the following boot parameters may be helpful: pci=noacpi Do not use ACPI for conguring the PCI devices. 568 Controlling the CPU Performance SLES 12 SP4acpi=ht Only perform a simple resource conguration. Do not use ACPI for other purposes. acpi=off Disable ACPI. Warning: Problems Booting without ACPI Some newer machines (especially SMP systems and AMD64 systems) need ACPI for conguring the hardware correctly. On these machines, disabling ACPI can cause problems. Sometimes, the machine is confused by hardware that is attached over USB or FireWire. If a machine refuses to boot, unplug all unneeded hardware and try again. Monitor the boot messages of the system with the command dmesg -T | grep -2i acpi (or all messages, because the problem may not be caused by ACPI) after booting. If an error occurs while parsing an ACPI table, the most important table—the DSDT (Dierentiated System Description Table)—can be replaced with an improved version. In this case, the faulty DSDT of the BIOS is ignored. The procedure is described in Section 38.4, “Troubleshooting”. In the kernel conguration, there is a switch for activating ACPI debug messages. If a kernel with ACPI debugging is compiled and installed, detailed information is issued. If you experience BIOS or hardware problems, it is always advisable to contact the manufacturers. Especially if they do not always provide assistance for Linux, they should be confronted with the problems. Manufacturers will only take the issue seriously if they realize that an adequate number of their customers use Linux. 569 Troubleshooting SLES 12 SP438.2.2.1 For More Information http://tldp.org/HOWTO/ACPI-HOWTO/ (detailed ACPI HOWTO, contains DSDT patches) http://www.acpi.info (Advanced Conguration & Power Interface Specication) http://acpi.sourceforge.net/dsdt/index.php (DSDT patches by Bruno Ducrot) 38.3 Rest for the Hard Disk In Linux, the hard disk can be put to sleep entirely if it is not needed or it can be run in a more economic or quieter mode. On modern laptops, you do not need to switch o the hard disks manually, because they automatically enter an economic operating mode whenever they are not needed. However, if you want to maximize power savings, test some of the following methods, using the hdparm command. It can be used to modify various hard disk settings. The option -y instantly switches the hard disk to the standby mode. -Y puts it to sleep. hdparm -S X causes the hard disk to be spun down after a certain period of inactivity. Replace X as follows: 0 disables this mechanism, causing the hard disk to run continuously. Values from 1 to 240 are multiplied by 5 seconds. Values from 241 to 251 correspond to 1 to 11 times 30 minutes. Internal power saving options of the hard disk can be controlled with the option -B . Select a value from 0 to 255 for maximum saving to maximum throughput. The result depends on the hard disk used and is dicult to assess. To make a hard disk quieter, use the option -M . Select a value from 128 to 254 for quiet to fast. Often, it is not so easy to put the hard disk to sleep. In Linux, numerous processes write to the hard disk, waking it up repeatedly. Therefore, it is important to understand how Linux handles data that needs to be written to the hard disk. First, all data is buered in the RAM. This buer is monitored by the pdflush daemon. When the data reaches a certain age limit or when the buer is lled to a certain degree, the buer content is ushed to the hard disk. The buer size is dynamic and depends on the size of the memory and the system load. By default, pdush is set to short intervals to achieve maximum data integrity. It checks the buer every 5 seconds and writes the data to the hard disk. The following variables are interesting: /proc/sys/vm/dirty_writeback_centisecs Contains the delay until a pdush thread wakes up (in hundredths of a second). /proc/sys/vm/dirty_expire_centisecs 570 Rest for the Hard Disk SLES 12 SP4Denes after which timeframe a dirty page should be written out latest. Default is 3000 , which means 30 seconds. /proc/sys/vm/dirty_background_ratio Maximum percentage of dirty pages until pdush begins to write them. Default is 5%. /proc/sys/vm/dirty_ratio When the dirty page exceeds this percentage of the total memory, processes are forced to write dirty buers during their time slice instead of continuing to write. Warning: Impairment of the Data Integrity Changes to the pdflush daemon settings endanger the data integrity. Apart from these processes, journaling le systems, like Btrfs , Ext3 , Ext4 and others write their metadata independently from pdflush , which also prevents the hard disk from spinning down. Another important factor is the way active programs behave. For example, good editors regularly write hidden backups of the currently modied le to the hard disk, causing the disk to wake up. Features like this can be disabled at the expense of data integrity. In this connection, the mail daemon postx uses the variable POSTFIX_LAPTOP . If this variable is set to yes , postx accesses the hard disk far less frequently. 38.4 Troubleshooting All error messages and alerts are logged in the system journal that can be queried with the command journalctl (see Chapter 15, journalctl: Query the systemd Journal for more information). The following sections cover the most common problems. 38.4.1 CPU Frequency Does Not Work Refer to the kernel sources to see if your processor is supported. You may need a special kernel module or module option to activate CPU frequency control. If the kernel-source package is installed, this information is available in /usr/src/linux/Documentation/cpu-freq/* . 571 Troubleshooting SLES 12 SP438.5 For More Information http://en.opensuse.org/SDB:Suspend_to_RAM —How to get Suspend to RAM working http://old-en.opensuse.org/Pm-utils —How to modify the general suspend framework 572 For More Information SLES 12 SP4VI Troubleshooting 39 Help and Documentation 574 40 Gathering System Information for Support 579 41 Common Problems and Their Solutions 60439 Help and Documentation SUSE® Linux Enterprise Server comes with various sources of information and documentation, many of which are already integrated into your installed system. Documentation in /usr/share/doc This traditional help directory holds various documentation les and release notes for your system. It contains also information of installed packages in the subdirectory packages . Find more detailed information in Section 39.1, “Documentation Directory”. Man Pages and Info Pages for Shell Commands When working with the shell, you do not need to know the options of the commands by heart. Traditionally, the shell provides integrated help by means of man pages and info pages. Read more in Section 39.2, “Man Pages” and Section 39.3, “Info Pages”. Desktop Help Center The help center of the GNOME desktop (Help) provides central access to the most important documentation resources on your system in searchable form. These resources include online help for installed applications, man pages, info pages, and the SUSE manuals delivered with your product. Separate Help Packages for Some Applications When installing new software with YaST, the software documentation is usually installed automatically and appears in the help center of your desktop. However, some applications, such as GIMP, may have dierent online help packages that can be installed separately with YaST and do not integrate into the help centers. 39.1 Documentation Directory The traditional directory to nd documentation on your installed Linux system is /usr/share/ doc . Usually, the directory contains information about the packages installed on your system, plus release notes, manuals, and more. 574 Documentation Directory SLES 12 SP4Note: Contents Depends on Installed Packages In the Linux world, many manuals and other kinds of documentation are available in the form of packages, like software. How much and which information you nd in /usr/ share/docs also depends on the (documentation) packages installed. If you cannot nd the subdirectories mentioned here, check if the respective packages are installed on your system and add them with YaST, if needed. 39.1.1 SUSE Manuals We provide HTML and PDF versions of our books in dierent languages. In the manual subdirectory, nd HTML versions of most of the SUSE manuals available for your product. For an overview of all documentation available for your product refer to the preface of the manuals. If more than one language is installed, /usr/share/doc/manual may contain dierent language versions of the manuals. The HTML versions of the SUSE manuals are also available in the help center of both desktops. For information on where to nd the PDF and HTML versions of the books on your installation media, refer to the SUSE Linux Enterprise Server Release Notes. They are available on your installed system under /usr/share/doc/release-notes/ or online at your product-specic Web page at http://www.suse.com/releasenotes/ . 39.1.2 Package Documentation Under packages , nd the documentation that is included in the software packages installed on your system. For every package, a subdirectory /usr/share/doc/packages/PACKAGENAME is created. It often contains README les for the package and sometimes examples, conguration les, or additional scripts. The following list introduces typical les to be found under /usr/ share/doc/packages . None of these entries are mandatory and many packages might only include a few of them. AUTHORS List of the main developers. BUGS Known bugs or malfunctions. Might also contain a link to a Bugzilla Web page where you can search all bugs. 575 SUSE Manuals SLES 12 SP4CHANGES , ChangeLog Summary of changes from version to version. Usually interesting for developers, because it is very detailed. COPYING , LICENSE Licensing information. FAQ Question and answers collected from mailing lists or newsgroups. INSTALL How to install this package on your system. As the package is already installed by the time you get to read this le, you can safely ignore the contents of this le. README , README.* General information on the software. For example, for what purpose and how to use it. TODO Things that are not implemented yet, but probably will be in the future. MANIFEST List of les with a brief summary. NEWS Description of what is new in this version. 39.2 Man Pages Man pages are an essential part of any Linux system. They explain the usage of a command and all available options and parameters. Man pages can be accessed with man followed by the name of the command, for example, man ls . Man pages are displayed directly in the shell. To navigate them, move up and down with Page ↑ and Page ↓ . Move between the beginning and the end of a document with Home and End . End this viewing mode by pressing Q . Learn more about the man command itself with man man . Man pages are sorted in categories as shown in Table 39.1, “Man Pages—Categories and Descriptions” (taken from the man page for man itself). 576 Man Pages SLES 12 SP4TABLE 39.1: MAN PAGES—CATEGORIES AND DESCRIPTIONS Number Description 1 Executable programs or shell commands 2 System calls (functions provided by the kernel) 3 Library calls (functions within program libraries) 4 Special les (usually found in /dev ) 5 File formats and conventions ( /etc/fstab ) 6 Games 7 Miscellaneous (including macro packages and conventions), for example, man(7), gro(7) 8 System administration commands (usually only for root ) 9 Kernel routines (nonstandard) Each man page consists of several parts labeled NAME , SYNOPSIS , DESCRIPTION , SEE ALSO , LICENSING , and AUTHOR . There may be additional sections available depending on the type of command. 39.3 Info Pages Info pages are another important source of information on your system. Usually, they are more detailed than man pages. They consist of more than command line options and contain sometimes whole tutorials or reference documentation. To view the info page for a certain command, enter info followed by the name of the command, for example, info ls . You can browse an info page with a viewer directly in the shell and display the dierent sections, called “nodes”. Use Space to move forward and <— to move backward. Within a node, you can also 577 Info Pages SLES 12 SP4browse with Page ↑ and Page ↓ but only Space and <— will take you also to the previous or subsequent node. Press Q to end the viewing mode. Not every command comes with an info page and vice versa. 39.4 Online Resources In addition to the online versions of the SUSE manuals installed under /usr/share/doc , you can also access the product-specic manuals and documentation on the Web. For an overview of all documentation available for SUSE Linux Enterprise Server check out your product-specic documentation Web page at https://documentation.suse.com/ . If you are searching for additional product-related information, you can also refer to the following Web sites: SUSE Technical Support The SUSE Technical Support can be found at https://www.suse.com/support/ if you have questions or need solutions for technical problems. SUSE Linux Enterprise Server User Community SUSE and Rancher Community (https://community.suse.com/) SUSE Blog The SUSE blog oers articles, tips, Q and A: https://www.suse.com/c/blog/ GNOME Documentation Documentation for GNOME users, administrators and developers is available at https:// library.gnome.org/ . The Linux Documentation Project The Linux Documentation Project (TLDP) is run by a team of volunteers who write Linux- related documentation (see https://www.tldp.org ). It is probably the most comprehensive documentation resource for Linux. The set of documents contains tutorials for beginners, but is mainly focused on experienced users and professional system administrators. TLDP publishes Howtos, FAQs, and guides (handbooks) under a free license. Parts of the documentation from TLDP are also available on SUSE Linux Enterprise Server. You can also try general-purpose search engines. For example, use the search terms Linux CD- RW help or OpenOffice file conversion problem if you have trouble with burning CDs or LibreOce le conversion. 578 Online Resources SLES 12 SP440 Gathering System Information for Support For a quick overview of all relevant system information of a machine, SUSE Linux Enterprise Server oers the hostinfo package. It also helps system administrators to check for tainted kernels (that are not supported) or any third-party packages installed on a machine. In case of problems, a detailed system report may be created with either the supportconfig command line tool or the YaST Support module. Both will collect information about the system such as: current kernel version, hardware, installed packages, partition setup, and much more. The result is a TAR archive of les. After opening a Service Request (SR), you can upload the TAR archive to Global Technical Support. It will help to locate the issue you reported and to assist you in solving the problem. Additionally, you can analyze the supportconfig output for known issues to help resolve problems faster. For this purpose, SUSE Linux Enterprise Server provides both an appliance and a command line tool for Supportconfig Analysis (SCA). 40.1 Displaying Current System Information For a quick and easy overview of all relevant system information when logging in to a server, use the package hostinfo . After it has been installed on a machine, the console displays the following information to any root user that logs in to this machine: EXAMPLE 40.1: OUTPUT OF hostinfo WHEN LOGGING IN AS root Hostname: earth Current As Of: Fri 28 Sep 2018 03:18:57 PM CEST Distribution: SUSE Linux Enterprise Server 12 -Service Pack: 4 Architecture: x86_64 Kernel Version: 4.12.14-94.37-default -Installed: Mon 24 Sep 2018 10:43:46 AM CEST -Status: Not Tainted Last Updated Package: Fri 28 Sep 2018 03:18:55 PM CEST -Patches Needed: 0 579 Displaying Current System Information SLES 12 SP4-Security: 0 -3rd Party Packages: 0 IPv4 Address: eth0 192.168.1.1 Total/Free/+Cache Memory: 1812/360/1275 MB (70% Free) Hard Disk: /dev/sda 32 GB In case the output shows a tainted kernel status, see Section 40.6, “Support of Kernel Modules” for more details. 40.2 Collecting System Information with Supportconfig To create a TAR archive with detailed system information that you can hand over to Global Technical Support, use either the supportconfig command line tool directly or the YaST Support module. The command line tool is provided by the package supportutils which is installed by default. The YaST Support module is also based on the command line tool. 40.2.1 Creating a Service Request Number Supportcong archives can be generated at any time. However, for handing over the supportcong data to Global Technical Support, you need to generate a service request number rst. You will need it to upload the archive to support. To create a service request, go to https://scc.suse.com/support/requests and follow the instructions on the screen. Write down your 12-digit service request number. Note: Privacy Statement SUSE and Micro Focus treat system reports as condential data. For details about our privacy commitment, see https://www.suse.com/company/policies/privacy/ . 580 Collecting System Information with Supportconfig SLES 12 SP440.2.2 Upload Targets After having created a service request number, you can upload your supportcong archives to Global Technical Support as described in Procedure 40.1, “Submitting Information to Support with YaST” or Procedure 40.2, “Submitting Information to Support from Command Line”. Use one of the following upload targets: US customers: ftp://ftp.novell.com/incoming EMEA, Europe, the Middle East, and Africa: ftp://support-ftp.suse.com/in Alternatively, you can manually attach the TAR archive to your service request using the service request URL: https://scc.suse.com/support/requests . 40.2.3 Creating a Supportconfig Archive with YaST To use YaST to gather your system information, proceed as follows: 1. Start YaST and open the Support module. 2. Click Create report tarball. 581 Upload Targets SLES 12 SP43. In the next window, select one of the supportcong options from the radio button list. Use Custom (Expert) Settings is preselected by default. If you want to test the report function rst, use Only gather a minimum amount of info. For some background information on the other options, refer to the supportconfig man page. Proceed with Next. 4. Enter your contact information. It will be written to a le called basic-environment.txt and included in the archive to be created. 5. If you want to submit the archive to Global Technical Support at the end of the information collection process, Upload Information is required. YaST automatically proposes an upload server. If you want to modify it, refer to Section 40.2.2, “Upload Targets” for details of which upload servers are available. If you want to submit the archive later on, you can leave the Upload Information empty for now. 6. Proceed with Next. 7. The information gathering begins. After the process is nished, continue with Next. 582 Creating a Supportconfig Archive with YaST SLES 12 SP48. Review the data collection: Select the File Name of a log le to view its contents in YaST. To remove any les you want excluded from the TAR archive before submitting it to support, use Remove from Data. Continue with Next. 9. Save the TAR archive. If you started the YaST module as root user, by default YaST proposes to save the archive to /var/log (otherwise, to your home directory). The le name format is nts_HOST_DATE_TIME.tbz . 10. If you want to upload the archive to support directly, make sure Upload log les tarball to URL is activated. The Upload Target shown here is the one that YaST proposes in Step 5. If you want to modify the upload target, nd detailed information of which upload servers are available in Section 40.2.2, “Upload Targets”. 11. If you want to skip the upload, deactivate Upload log les tarball to URL. 12. Conrm your changes to close the YaST module. 40.2.4 Creating a Supportconfig Archive from Command Line The following procedure shows how to create a supportcong archive, but without submitting it to support directly. For uploading it, you need to run the command with certain options as described in Procedure 40.2, “Submitting Information to Support from Command Line”. 1. Open a shell and become root . 2. Run supportconfig without any options. This gathers the default system information. 3. Wait for the tool to complete the operation. 4. The default archive location is /var/log , with the le name format being nts_HOST_DATE_TIME.tbz 40.2.5 Common Supportconfig Options The supportconfig utility is usually called without any options. Display a list of all options with supportconfig -h or refer to the man page. The following list gives a brief overview of some common use cases: Reducing the Size of the Information Being Gathered 583 Creating a Supportconfig Archive from Command Line SLES 12 SP4Use the minimal option ( -m ): supportconfig -m Limiting the Information to a Specific Topic If you have already localized a problem with the default supportconfig output and have found that it relates to a specic area or feature set only, you should limit the collected information to the specic area for the next supportconfig run. For example, if you detected problems with LVM and want to test a recent change that you did to the LVM conguration, it makes sense to gather the minimum supportcong information around LVM only: supportconfig -i LVM For a complete list of feature keywords that you can use for limiting the collected information to a specic area, run supportconfig -F Including Additional Contact Information in the Output: supportconfig -E tux@example.org -N "Tux Penguin" -O "Penguin Inc." ... (all in one line) Collecting Already Rotated Log Files supportconfig -l This is especially useful in high logging environments or after a kernel crash when syslog rotates the log les after a reboot. 40.3 Submitting Information to Global Technical Support Use the YaST Support module or the supportconfig command line utility to submit system information to the Global Technical Support. When you experience a server issue and want the support''s assistance, you will need to open a service request rst. For details, see Section 40.2.1, “Creating a Service Request Number”. The following examples use 12345678901 as a placeholder for your service request number. Replace 12345678901 with the service request number you created in Section 40.2.1, “Creating a Service Request Number”. 584 Submitting Information to Global Technical Support SLES 12 SP4PROCEDURE 40.1: SUBMITTING INFORMATION TO SUPPORT WITH YAST The following procedure assumes that you have already created a supportcong archive, but have not uploaded it yet. Make sure to have included your contact information in the archive as described in Section 40.2.3, “Creating a Supportconfig Archive with YaST”, Step 4. For instructions on how to generate and submit a supportcong archive in one go, see Section 40.2.3, “Creating a Supportconfig Archive with YaST”. 1. Start YaST and open the Support module. 2. Click Upload. 3. In Package with log les specify the path to the existing supportcong archive or Browse for it. 4. YaST automatically proposes an upload server. If you want to modify it, refer to Section 40.2.2, “Upload Targets” for details of which upload servers are available. Proceed with Next. 5. Click Finish. PROCEDURE 40.2: SUBMITTING INFORMATION TO SUPPORT FROM COMMAND LINE The following procedure assumes that you have already created a supportcong archive, but have not uploaded it yet. For instructions on how to generate and submit a supportcong archive in one go, see Section 40.2.3, “Creating a Supportconfig Archive with YaST”. 585 Submitting Information to Global Technical Support SLES 12 SP41. Servers with Internet connectivity: a. To use the default upload target, run: supportconfig -ur 12345678901 b. For the secure upload target, use the following: supportconfig -ar 12345678901 2. Servers without Internet connectivity a. Run the following: supportconfig -r 12345678901 b. Manually upload the /var/log/nts_SR12345678901*tbz archive to one of our FTP servers. Which one to use depends on your location in the world. For an overview, see Section 40.2.2, “Upload Targets”. 3. After the TAR archive arrives in the incoming directory of our FTP server, it becomes automatically attached to your service request. 40.4 Analyzing System Information System reports created with supportconfig can be analyzed for known issues to help resolve problems faster. For this purpose, SUSE Linux Enterprise Server provides both an appliance and a command line tool for Supportconfig Analysis (SCA). The SCA appliance is a server-side tool which is non-interactive. The SCA tool ( scatool ) runs on the client-side and is executed from command line. Both tools analyze supportcong archives from aected servers. The initial server analysis takes place on the SCA appliance or the workstation on which scatool is running. No analysis cycles happen on the production server. Both the appliance and the command line tool additionally need product-specic patterns that enable them to analyze the supportcong output for the associated products. Each pattern is a script that parses and evaluates a supportcong archive for one known issue. The patterns are available as RPM packages. 586 Analyzing System Information SLES 12 SP4For example, if you want to analyze supportcong archives that have been generated on a SUSE Linux Enterprise 11 machine, you need to install the package sca-patterns-sle11 together with the SCA tool (or on the machine that you want to use as the SCA appliance server). To analyze supportcong archives generated on a SUSE Linux Enterprise 10 machine, you need the package sca-patterns-sle10 . You can also develop your own patterns as briey described in Section 40.4.3, “Developing Custom Analysis Patterns”. 40.4.1 SCA Command Line Tool The SCA command line tool lets you analyze a local machine using both supportconfig and the analysis patterns for the specic product that is installed on the local machine. The tool creates an HTML report showing its analysis results. For an example, see Figure 40.1, “HTML Report Generated by SCA Tool”. FIGURE 40.1: HTML REPORT GENERATED BY SCA TOOL 587 SCA Command Line Tool SLES 12 SP4The scatool command is provided by the sca-server-report package. It is not installed by default. Additionally, you need the sca-patterns-base package and any of the product- specic sca-patterns-* packages that matches the product installed on the machine where you want to run the scatool command. Execute the scatool command either as root user or with sudo . When calling the SCA tool, you can either analyze an existing supportconfig TAR archive or you can let it generate and analyze a new archive in one go. The tool also provides an interactive console (with tab completion) and the possibility to run supportconfig on an external machine and to execute the subsequent analysis on the local machine. Find some example commands below: sudo scatool -s Calls supportconfig and generates a new supportcong archive on the local machine. Analyzes the archive for known issues by applying the SCA analysis patterns that match the installed product. Displays the path to the HTML report that is generated from the results of the analysis. It is usually written to the same directory where the supportcong archive can be found. sudo scatool  -s   -o   /opt/sca/reports/ Same as sudo scatool -s , only that the HTML report is written to the path specied with -o . sudo scatool  -a   PATH_TO_TARBALL_OR_DIR Analyzes the specied supportcong archive le (or the specied directory to where the supportcong archive has been extracted). The generated HTML report is saved in the same location as the supportcong archive or directory. sudo scatool  -a   SLES_SERVER.COMPANY.COM Establishes an SSH connection to an external server SLES_SERVER.COMPANY.COM and runs supportconfig on the server. The supportcong archive is then copied back to the local machine and is analyzed there. The generated HTML report is saved to the default /var/log directory. (Only the supportcong archive is created on SLES_SERVER.COMPANY.COM ). sudo scatool -c Starts the interactive console for scatool . Press →| twice to see the available commands. For further options and information, run sudo scatool -h or see the scatool man page. 588 SCA Command Line Tool SLES 12 SP440.4.2 SCA Appliance If you decide to use the SCA appliance for analyzing the supportcong archives, you need to congure a dedicated server (or virtual machine) as the SCA appliance server. The SCA appliance server can then be used to analyze supportcong archives from all machines in your enterprise running SUSE Linux Enterprise Server or SUSE Linux Enterprise Desktop. You can simply upload supportcong archives to the appliance server for analysis. Interaction is not required. In a MariaDB database, the SCA appliance keeps track of all supportcong archives that have been analyzed . You can read the SCA reports directly from the appliance Web interface. Alternatively, you can have the appliance send the HTML report to any administrative user via e-mail. For details, see Section 40.4.2.5.4, “Sending SCA Reports via E-Mail”. 40.4.2.1 Installation Quick Start To install and set up the SCA appliance in a very fast way from the command line, follow the instructions here. The procedure is intended for experts and focuses on the bare installation and setup commands. For more information, refer to the more detailed description in Section 40.4.2.2, “Prerequisites” to Section 40.4.2.3, “Installation and Basic Setup”. PREREQUISITES Web and LAMP Pattern Web and Scripting Module (you must register the machine to be able to select this module). Note: root Privileges Required All commands in the following procedure must be run as root . PROCEDURE 40.3: INSTALLATION USING ANONYMOUS FTP FOR UPLOAD After the appliance is set up and running, no more manual interaction is required. This way of setting up the appliance is therefore ideal for using cron jobs to create and upload supportcong archives. 1. On the machine on which to install the appliance, log in to a console and execute the following commands: zypper install sca-appliance-* sca-patterns-* vsftpd systemctl enable apache2 589 SCA Appliance SLES 12 SP4systemctl start apache2 systemctl enable vsftpd systemctl start vsftpd yast ftp-server 2. In YaST FTP Server, select Authentication Enable Upload Anonymous Can Upload Finish Yes to Create /srv/ftp/upload. 3. Execute the following commands: systemctl enable mysql systemctl start mysql mysql_secure_installation setup-sca -f The mysql_secure_installation will create a MariaDB root password. PROCEDURE 40.4: INSTALLATION USING SCP/TMP FOR UPLOAD This way of setting up the appliance requires manual interaction when typing the SSH password. 1. On the machine on which to install the appliance, log in to a console. 2. Execute the following commands: zypper install sca-appliance-* sca-patterns-* systemctl enable apache2 systemctl start apache2 sudo systemctl enable mysql systemctl start mysql mysql_secure_installation setup-sca 40.4.2.2 Prerequisites To run an SCA appliance server, you need the following prerequisites: All sca-appliance-* packages. The sca-patterns-base package. Additionally, any of the product-specic sca- patterns-* for the type of supportcong archives that you want to analyze with the appliance. Apache 590 SCA Appliance SLES 12 SP4PHP MariaDB anonymous FTP server (optional) 40.4.2.3 Installation and Basic Setup As listed in Section 40.4.2.2, “Prerequisites”, the SCA appliance has several dependencies on other packages. Therefore you need do so some preparations before installing and setting up the SCA appliance server: 1. For Apache and MariaDB, install the Web and LAMP installation patterns. 2. Set up Apache, MariaDB, and optionally an anonymous FTP server. For more information, see Chapter 32, The Apache HTTP Server and Chapter 33, Setting Up an FTP Server with YaST. 3. Congure Apache and MariaDB to start at boot time: sudo systemctl enable apache2 mysql 4. Start both services: sudo systemctl start apache2 mysql Now you can install the SCA appliance and set it up as described in Procedure 40.5, “Installing and Configuring the SCA Appliance”. PROCEDURE 40.5: INSTALLING AND CONFIGURING THE SCA APPLIANCE After installing the packages, use the setup-sca script for the basic conguration of the MariaDB administration and report database that is used by the SCA appliance. It can be used to congure the following options you have for uploading the supportcong archives from your machines to the SCA appliance: scp anonymous FTP server 1. Install the appliance and the SCA base-pattern library: sudo zypper install sca-appliance-* sca-patterns-base 591 SCA Appliance SLES 12 SP42. Additionally, install the pattern packages for the types of supportcong archives you want to analyze. For example, if you have SUSE Linux Enterprise Server 11 and SUSE Linux Enterprise Server 12 servers in your environment, install both the sca-patterns-sle11 and sca-patterns-sle12 packages. To install all available patterns: zypper install sca-patterns-* 3. For basic setup of the SCA appliance, use the setup-sca script. How to call it depends on how you want to upload the supportcong archives to the SCA appliance server: If you have congured an anonymous FTP server that uses the /srv/ftp/upload directory, execute the setup script with the -f option and follow the instructions on the screen: setup-sca -f Note: FTP Server Using Another Directory If your FTP server uses another directory than /srv/ftp/upload , adjust the following conguration les rst to make them point to the correct directory: /etc/sca/sdagent.conf and /etc/sca/sdbroker.conf . If you want to upload supportcong les to the /tmp directory of the SCA appliance server via scp , call the setup script without any parameters and follow the instructions on the screen: setup-sca The setup script runs a few checks regarding its requirements and congures the needed components. It will prompt you for two passwords: the MySQL root password of the MariaDB that you have set up, and a Web user password with which to log in to the Web interface of the SCA appliance. 4. Enter the existing MariaDB root password. It will allow the SCA appliance to connect to the MariaDB. 592 SCA Appliance SLES 12 SP45. Dene a password for the Web user. It will be written to /srv/www/htdocs/sca/web- config.php and will be set as the password for the user scdiag . Both user name and password can be changed at any time later, see Section 40.4.2.5.1, “Password for the Web Interface”. After successful installation and setup, the SCA appliance is ready for use, see Section 40.4.2.4, “Using the SCA Appliance”. However, you should modify some options such as changing the password for the Web interface, changing the source for the SCA pattern updates, enabling archiving mode or conguring e-mail notications. For details on that, see Section  40.4.2.5, “Customizing the SCA Appliance”. Warning: Data Protection As the reports on the SCA appliance server contain security-relevant information of the machines whose supportcong archives have been analyzed, make sure to protect the data on the SCA appliance server against unauthorized access. 40.4.2.4 Using the SCA Appliance You can upload existing supportcong archives to the SCA appliance manually or create new supportcong archives and upload them to the SCA appliance in one step. Uploading can be done via FTP or SCP. For both, you need to know the URL where the SCA appliance can be reached. For upload via FTP, an FTP server needs to be congured for the SCA appliance, see Procedure 40.5, “Installing and Configuring the SCA Appliance”. 40.4.2.4.1 Uploading Supportconfig Archives to the SCA Appliance For creating a supportcong archive and uploading it via (anonymous) FTP: sudo supportconfig -U “ftp://SCA-APPLIANCE.COMPANY.COM/upload” For creating a supportcong archive and uploading it via SCP: sudo supportconfig -U “scp://SCA-APPLIANCE.COMPANY.COM/tmp” 593 SCA Appliance SLES 12 SP4You will be prompted for the root user password of the server running the SCA appliance. If you want to manually upload one or multiple archives, copy the existing archive les (usually located at /var/log/nts_*.tbz ) to the SCA appliance. As target, use either the appliance server''s /tmp directory or the /srv/ftp/upload directory (if FTP is congured for the SCA appliance server). 40.4.2.4.2 Viewing SCA Reports SCA reports can be viewed from any machine that has a browser installed and can access the report index page of the SCA appliance. 1. Start a Web browser and make sure that JavaScript and cookies are enabled. 2. As a URL, enter the report index page of the SCA appliance. https://sca-appliance.company.com/sca If in doubt, ask your system administrator. 3. You will be prompted for a user name and a password to log in. FIGURE 40.2: HTML REPORT GENERATED BY SCA APPLIANCE 594 SCA Appliance SLES 12 SP44. After logging in, click the date of the report you want to read. 5. Click the Basic Health category rst to expand it. 6. In the Message column, click an individual entry. This opens the corresponding article in the SUSE Knowledgebase. Read the proposed solution and follow the instructions. 7. If the Solutions column of the Supportcong Analysis Report shows any additional entries, click them. Read the proposed solution and follow the instructions. 8. Check the SUSE Knowledge base (https://www.suse.com/support/kb/ ) for results that directly relate to the problem identied by SCA. Work at resolving them. 9. Check for results that can be addressed proactively to avoid future problems. 40.4.2.5 Customizing the SCA Appliance The following sections show how to change the password for the Web interface, how to change the source for the SCA pattern updates, how to enable archiving mode, and how to congure e-mail notications. 40.4.2.5.1 Password for the Web Interface The SCA Appliance Web interface requires a user name and password for logging in. The default user name is scdiag and the default password is linux (if not specied otherwise, see Procedure 40.5, “Installing and Configuring the SCA Appliance”). Change the default password to a secure password at the earliest possibility. You can also modify the user name. PROCEDURE 40.6: CHANGING USER NAME OR PASSWORD FOR THE WEB INTERFACE 1. Log in as root user at the system console of the SCA appliance server. 2. Open /srv/www/htdocs/sca/web-config.php in an editor. 3. Change the values of $username and $password as desired. 4. Save the le and exit. 595 SCA Appliance SLES 12 SP440.4.2.5.2 Updates of SCA Patterns By default, all sca-patterns-* packages are updated regularly by a root cron job that executes the sdagent-patterns script nightly, which in turn runs zypper update sca- patterns-* . A regular system update will update all SCA appliance and pattern packages. To update the SCA appliance and patterns manually, run: sudo zypper update sca-* The updates are installed from the SUSE Linux Enterprise 12 SP4 update repository by default. You can change the source for the updates to an SMT server, if desired. When sdagent- patterns runs zypper update sca-patterns-* , it gets the updates from the currently congured update channel. If that channel is located on an SMT server, the packages will be pulled from there. PROCEDURE 40.7: DISABLING AUTOMATIC UPDATES OF SCA PATTERNS 1. Log in as root user at the system console of the SCA appliance server. 2. Open /etc/sca/sdagent-patterns.conf in an editor. 3. Change the entry UPDATE_FROM_PATTERN_REPO=1 to UPDATE_FROM_PATTERN_REPO=0 4. Save the le and exit. The machine does not require any restart to apply the change. 40.4.2.5.3 Archiving Mode All supportcong archives are deleted from the SCA appliance after they have been analyzed and their results have been stored in the MariaDB database. However, for troubleshooting purposes it can be useful to keep copies of supportcong archives from a machine. By default, archiving mode is disabled. PROCEDURE 40.8: ENABLING ARCHIVING MODE IN THE SCA APPLIANCE 1. Log in as root user at the system console of the SCA appliance server. 596 SCA Appliance SLES 12 SP42. Open /etc/sca/sdagent.conf in an editor. 3. Change the entry ARCHIVE_MODE=0 to ARCHIVE_MODE=1 4. Save the le and exit. The machine does not require any restart to apply the change. After having enabled archive mode, the SCA appliance will save the supportcong les to the /var/log/archives/saved directory, instead of deleting them. 40.4.2.5.4 Sending SCA Reports via E-Mail The SCA appliance can e-mail a report HTML le for each supportcong analyzed. This feature is disabled by default. When enabling it, you can dene a list of e-mail addresses to which the reports should be sent, and dene a level of status messages that trigger the sending of reports ( STATUS_NOTIFY_LEVEL ). POSSIBLE VALUES FOR STATUS_NOTIFY_LEVEL $STATUS_OFF Deactivate sending of HTML reports. $STATUS_CRITICAL Send only SCA reports that include a CRITICAL. $STATUS_WARNING Send only SCA reports that include a WARNING or CRITICAL. $STATUS_RECOMMEND Send only SCA reports that include a RECOMMEND, WARNING or CRITICAL. $STATUS_SUCCESS Send SCA reports that include a SUCCESS, RECOMMEND, WARNING or CRITICAL. PROCEDURE 40.9: CONFIGURING E-MAIL NOTIFICATIONS FOR SCA REPORTS 1. Log in as root user at the system console of the SCA appliance server. 597 SCA Appliance SLES 12 SP42. Open /etc/sca/sdagent.conf in an editor. 3. Search for the entry STATUS_NOTIFY_LEVEL . By default, it is set to $STATUS_OFF (e-mail notications are disabled). 4. To enable e-mail notications, change $STATUS_OFF to the level of status messages that you want to have e-mail reports for, for example: STATUS_NOTIFY_LEVEL=$STATUS_SUCCESS For details, see Possible Values for STATUS_NOTIFY_LEVEL. 5. To dene the list of recipients to which the reports should be sent: a. Search for the entry EMAIL_REPORT=''root'' . b. Replace root with a list of e-mail addresses to which SCA reports should be sent. The e-mail addresses must be separated by spaces. For example: EMAIL_REPORT=''tux@my.company.com wilber@your.company.com'' 6. Save the le and exit. The machine does not require any restart to apply the changes. All future SCA reports will be e-mailed to the specied addresses. 40.4.2.6 Backing Up and Restoring the Database To back up and restore the MariaDB database that stores the SCA reports, use the scadb command as described below. PROCEDURE 40.10: BACKING UP THE DATABASE 1. Log in as root user at the system console of the server running the SCA appliance. 2. Put the appliance into maintenance mode by executing: scadb maint 3. Start the backup with: scadb backup The data is saved to a TAR archive: sca-backup-*sql.gz . 598 SCA Appliance SLES 12 SP44. If you are using the pattern creation database to develop your own patterns (see Section 40.4.3, “Developing Custom Analysis Patterns”), back up this data, too: sdpdb backup The data is saved to a TAR archive: sdp-backup-*sql.gz . 5. Copy the following data to another machine or an external storage medium: sca-backup-*sql.gz sdp-backup-*sql.gz /usr/lib/sca/patterns/local (only needed if you have created custom patterns) 6. Reactivate the SCA appliance with: scadb reset agents PROCEDURE 40.11: RESTORING THE DATABASE To restore the database from your backup, proceed as follows: 1. Log in as root user at the system console of the server running the SCA appliance. 2. Copy the newest sca-backup-*sql.gz and sdp-backup-*sql.gz TAR archives to the SCA appliance server. 3. To decompress the les, run: gzip -d *-backup-*sql.gz 4. To import the data into the database, execute: scadb import sca-backup-*sql 5. If you are using the pattern creation database to create your own patterns, also import the following data with: sdpdb import sdp-backup-*sql 6. If you are using custom patterns, also restore /usr/lib/sca/patterns/local from your backup data. 7. Reactivate the SCA appliance with: scadb reset agents 599 SCA Appliance SLES 12 SP48. Update the pattern modules in the database with: sdagent-patterns -u 40.4.3 Developing Custom Analysis Patterns The SCA appliance comes with a complete pattern development environment (the SCA Pattern Database) that enables you to develop your own, custom patterns. Patterns can be written in any programming language. To make them available for the supportcong analysis process, they need to be saved to /usr/lib/sca/patterns/local and to be made executable. Both the SCA appliance and the SCA tool will then run the custom patterns against new supportcong archives as part of the analysis report. For detailed instructions on how to create (and test) your own patterns, see https://www.suse.com/c/blog/sca-pattern-development/ . 40.5 Gathering Information during the Installation During the installation, supportconfig is not available. However, you can collect log les from YaST by using save_y2logs . This command will create a .tar.xz archive in the directory /tmp . If issues appear very early during installation, you may be able to gather information from the log le created by linuxrc . linuxrc is a small command that runs before YaST starts. This log le is available at /var/log/linuxrc.log . Important: Installation Log Files Not Available in the Installed System The log les available during the installation are not available in the installed system anymore. Properly save the installation log les while the installer is still running. 600 Developing Custom Analysis Patterns SLES 12 SP440.6 Support of Kernel Modules An important requirement for every enterprise operating system is the level of support you receive for your environment. Kernel modules are the most relevant connector between hardware (“controllers”) and the operating system. Every kernel module in SUSE Linux Enterprise has a supported ag that can take three possible values: “yes”, thus supported “external”, thus supported “” (empty, not set), thus unsupported The following rules apply: All modules of a self-recompiled kernel are by default marked as unsupported. Kernel modules supported by SUSE partners and delivered using SUSE SolidDriver Program are marked “external”. If the supported ag is not set, loading this module will taint the kernel. Tainted kernels are not supported. Unsupported Kernel modules are included in an extra RPM package ( kernel-FLAVOR-extra ) that is only available for SUSE Linux Enterprise Desktop and the SUSE Linux Enterprise Workstation Extension. Those kernels will not be loaded by default ( FLAVOR= default | xen |...). In addition, these unsupported modules are not available in the installer, and the kernel-FLAVOR-extra package is not part of the SUSE Linux Enterprise media. Kernel modules not provided under a license compatible to the license of the Linux kernel will also taint the kernel. For details, see /usr/src/linux/Documentation/sysctl/ kernel.txt and the state of /proc/sys/kernel/tainted . 601 Support of Kernel Modules SLES 12 SP440.6.1 Technical Background Linux kernel: The value of /proc/sys/kernel/unsupported defaults to 2 on SUSE Linux Enterprise 12 SP4 ( do not warn in syslog when loading unsupported modules ). This default is used in the installer and in the installed system. See /usr/src/linux/ Documentation/sysctl/kernel.txt for more information. modprobe : The modprobe utility for checking module dependencies and loading modules appropriately checks for the value of the supported ag. If the value is “yes” or “external” the module will be loaded, otherwise it will not. For information on how to override this behavior, see Section 40.6.2, “Working with Unsupported Modules”. Note: Support SUSE does not generally support the removal of storage modules via modprobe -r . 40.6.2 Working with Unsupported Modules While general supportability is important, situations can occur where loading an unsupported module is required (for example, for testing or debugging purposes, or if your hardware vendor provides a hotx). To override the default, edit /etc/modprobe.d/10-unsupported-modules.conf and change the value of the variable allow_unsupported_modules to 1 . If an unsupported module is needed in the initrd, do not forget to run dracut -f to update the initrd. If you only want to try loading a module once, you can use the --allow-unsupported- modules option with modprobe . For more information, see the modprobe man page. During installation, unsupported modules may be added through driver update disks, and they will be loaded. To enforce loading of unsupported modules during boot and afterward, use the kernel command line option oem-modules . While installing and initializing the suse-module-tools package, the kernel ag TAINT_NO_SUPPORT ( /proc/sys/kernel/tainted ) will be evaluated. If the kernel is already tainted, allow_unsupported_modules will be enabled. This will prevent unsupported modules from failing in the system being installed. If no unsupported modules are present during installation and the other special kernel command line option ( oem-modules=1 ) is not used, the default still is to disallow unsupported modules. 602 Technical Background SLES 12 SP4Remember that loading and running unsupported modules will make the kernel and the whole system unsupported by SUSE. 40.7 For More Information man supportconfig—The supportconfig man page. man supportconfig.conf—The man page of the supportcong conguration le. man scatool—The scatool man page. man scadb—The scadb man page. man setup-sca—The setup-sca man page. https://mariadb.com/kb/en/ —The MariaDB documentation. http://httpd.apache.org/docs/ and Chapter  32, The Apache HTTP Server—Documentation about the Apache Web server. Chapter 33, Setting Up an FTP Server with YaST—Documentation of how to set up an FTP server. https://www.suse.com/c/blog/sca-pattern-development/ —Instructions on how to create (and test) your own SCA patterns. https://www.suse.com/c/blog/basic-server-health-check-supportconfig/ —A Basic Server Health Check with Supportcong. https://community.microfocus.com/t5/GroupWise-Tips-Information/Create-Your-Own- Supportconfig-Plugin/ta-p/1783289 —Create Your Own Supportcong Plugin. https://www.suse.com/c/blog/creating-a-central-supportconfig-repository/ —Creating a Central Supportcong Repository. 603 For More Information SLES 12 SP441 Common Problems and Their Solutions This chapter describes a range of potential problems and their solutions. Even if your situation is not precisely listed here, there may be one similar enough to oer hints to the solution of your problem. 41.1 Finding and Gathering Information Linux reports things in a very detailed way. There are several places to look when you encounter problems with your system, most of which are standard to Linux systems in general, and some are relevant to SUSE Linux Enterprise Server systems. Most log les can be viewed with YaST (Miscellaneous Start-Up Log). YaST oers the possibility to collect all system information needed by the support team. Use Other Support and select the problem category. When all information is gathered, attach it to your support request. A list of the most frequently checked log les follows with the description of their typical purpose. Paths containing ~ refer to the current user''s home directory. TABLE 41.1: LOG FILES Log File Description ~/.xsession-errors Messages from the desktop applications currently running. /var/log/apparmor/ Log les from AppArmor, see Book “Security Guide” for detailed information. /var/log/audit/audit.log Log le from Audit to track any access to les, directories, or resources of your system, and trace system calls. See Book “Security Guide” for detailed information. /var/log/mail.* Messages from the mail system. /var/log/NetworkManager Log le from NetworkManager to collect problems with network connectivity 604 Finding and Gathering Information SLES 12 SP4Log File Description /var/log/samba/ Directory containing Samba server and client log messages. /var/log/warn All messages from the kernel and system log daemon with the “warning” level or higher. /var/log/wtmp Binary le containing user login records for the current machine session. View it with last . /var/log/Xorg.*.log Various start-up and runtime log les from the X Window System. It is useful for debugging failed X start-ups. /var/log/YaST2/ Directory containing YaST''s actions and their results. /var/log/zypper.log Log le of Zypper. Apart from log les, your machine also supplies you with information about the running system. See Table 41.2: System Information With the /proc File System TABLE 41.2: SYSTEM INFORMATION WITH THE /proc FILE SYSTEM File Description /proc/cpuinfo Contains processor information, including its type, make, model, and performance. /proc/dma Shows which DMA channels are currently being used. /proc/interrupts Shows which interrupts are in use, and how many of each have been in use. /proc/iomem Displays the status of I/O (input/output) memory. 605 Finding and Gathering Information SLES 12 SP4File Description /proc/ioports Shows which I/O ports are in use at the moment. /proc/meminfo Displays memory status. /proc/modules Displays the individual modules. /proc/mounts Displays devices currently mounted. /proc/partitions Shows the partitioning of all hard disks. /proc/version Displays the current version of Linux. Apart from the /proc le system, the Linux kernel exports information with the sysfs module, an in-memory le system. This module represents kernel objects, their attributes and relationships. For more information about sysfs , see the context of udev in Chapter 21, Dynamic Kernel Device Management with udev. Table 41.3 contains an overview of the most common directories under /sys . TABLE 41.3: SYSTEM INFORMATION WITH THE /sys FILE SYSTEM File Description /sys/block Contains subdirectories for each block device discovered in the system. Generally, these are mostly disk type devices. /sys/bus Contains subdirectories for each physical bus type. /sys/class Contains subdirectories grouped together as a functional types of devices (like graphics, net, printer, etc.) /sys/device Contains the global device hierarchy. Linux comes with several tools for system analysis and monitoring. See Book “System Analysis and Tuning Guide”, Chapter 2 “System Monitoring Utilities” for a selection of the most important ones used in system diagnostics. 606 Finding and Gathering Information SLES 12 SP4Each of the following scenarios begins with a header describing the problem followed by a paragraph or two oering suggested solutions, available references for more detailed solutions, and cross-references to other scenarios that are related. 41.2 Installation Problems Installation problems are situations when a machine fails to install. It may fail entirely or it may not be able to start the graphical installer. This section highlights some typical problems you may run into, and oers possible solutions or workarounds for these kinds of situations. 41.2.1 Checking Media If you encounter any problems using the SUSE Linux Enterprise Server installation media, check the integrity of your installation media. Boot from the media and choose Check Installation Media from the boot menu. In a running system, start YaST and choose Software Media Check. To check the SUSE Linux Enterprise Server medium, insert it into the drive and click Start Check in the Media Check screen of YaST. This may take several minutes. If errors are detected, do not use this medium for installation. Media problems may occur when having burned the medium yourself. Burning the media at a low speed (4x) helps to avoid problems. 607 Installation Problems SLES 12 SP4FIGURE 41.1: CHECKING MEDIA 41.2.2 No Bootable DVD Drive Available If your computer does not contain a bootable DVD-ROM drive or if the one you have is not supported by Linux, there are several options you can install your machine without a built-in DVD drive: Using an External Boot Device If it is supported by your BIOS and the installation kernel, boot from external DVD drives or USB storage devices. Refer to Book “Deployment Guide”, Chapter 6 “Installation with YaST”, Section 6.2.2 “PC (AMD64/Intel 64/ARM AArch64): System Start-up” for instructions on how to create a bootable USB storage device. Network Boot via PXE If a machine lacks a DVD drive, but provides a working Ethernet connection, perform a completely network-based installation. See Book “Deployment Guide”, Chapter 10 “Remote Installation”, Section 10.1.3 “Remote Installation via VNC—PXE Boot and Wake on LAN” and Book “Deployment Guide”, Chapter 10 “Remote Installation”, Section 10.1.6 “Remote Installation via SSH —PXE Boot and Wake on LAN” for details. 608 No Bootable DVD Drive Available SLES 12 SP441.2.2.1 External Boot Devices Linux supports most existing DVD drives. If the system has no DVD drive, it is still possible that an external DVD drive, connected through USB, FireWire, or SCSI, can be used to boot the system. This depends mainly on the interaction of the BIOS and the hardware used. Sometimes a BIOS update may help if you encounter problems. When installing from a Live CD, you can also create a “Live ash disk” to boot from. 41.2.3 Booting from Installation Media Fails One reason a machine does not boot the installation media can be an incorrect boot sequence setting in BIOS. The BIOS boot sequence must have DVD drive set as the rst entry for booting. Otherwise the machine would try to boot from another medium, typically the hard disk. Guidance for changing the BIOS boot sequence can be found the documentation provided with your mainboard, or in the following paragraphs. The BIOS is the software that enables the very basic functions of a computer. Motherboard vendors provide a BIOS specically made for their hardware. Normally, the BIOS setup can only be accessed at a specic time—when the machine is booting. During this initialization phase, the machine performs several diagnostic hardware tests. One of them is a memory check, indicated by a memory counter. When the counter appears, look for a line, usually below the counter or somewhere at the bottom, mentioning the key to press to access the BIOS setup. Usually the key to press is one of Del , F1 , or Esc . Press this key until the BIOS setup screen appears. PROCEDURE 41.1: CHANGING THE BIOS BOOT SEQUENCE 1. Enter the BIOS using the proper key as announced by the boot routines and wait for the BIOS screen to appear. 2. To change the boot sequence in an AWARD BIOS, look for the BIOS FEATURES SETUP entry. Other manufacturers may have a dierent name for this, such as ADVANCED CMOS SETUP. When you have found the entry, select it and conrm with Enter . 3. In the screen that opens, look for a subentry called BOOT SEQUENCE or BOOT ORDER. Change the settings by pressing Page ↑ or Page ↓ until the DVD drive is listed rst. 4. Leave the BIOS setup screen by pressing Esc . To save the changes, select SAVE & EXIT SETUP, or press F10 . To conrm that your settings should be saved, press Y . 609 Booting from Installation Media Fails SLES 12 SP4PROCEDURE 41.2: CHANGING THE BOOT SEQUENCE IN AN SCSI BIOS (ADAPTEC HOST ADAPTER) 1. Open the setup by pressing Ctrl – A . 2. Select Disk Utilities. The connected hardware components are now displayed. Make note of the SCSI ID of your DVD drive. 3. Exit the menu with Esc . 4. Open Congure Adapter Settings. Under Additional Options, select Boot Device Options and press Enter . 5. Enter the ID of the DVD drive and press Enter again. 6. Press Esc twice to return to the start screen of the SCSI BIOS. 7. Exit this screen and conrm with Yes to boot the computer. Regardless of what language and keyboard layout your nal installation will be using, most BIOS congurations use the US keyboard layout as shown in the following gure: FIGURE 41.2: US KEYBOARD LAYOUT 41.2.4 Fails to Boot Some hardware types, mainly very old or very recent ones, fail to install. Often this may happen because support for this type of hardware is missing in the installation kernel, or because of certain functionality included in this kernel, such as ACPI, that can still cause problems on some hardware. 610 Fails to Boot SLES 12 SP4If your system fails to install using the standard Installation mode from the rst installation boot screen, try the following: 1. With the DVD still in the drive, reboot the machine with Ctrl – Alt – Del or using the hardware reset button. 2. When the boot screen appears, press F5 , use the arrow keys of your keyboard to navigate to No ACPI and press Enter to launch the boot and installation process. This option disables the support for ACPI power management techniques. 3. Proceed with the installation as described in Book “Deployment Guide”, Chapter 6 “Installation with YaST”. If this fails, proceed as above, but choose Safe Settings instead. This option disables ACPI and DMA support. Most hardware will boot with this option. If both of these options fail, use the boot options prompt to pass any additional parameters needed to support this type of hardware to the installation kernel. For more information about the parameters available as boot options, refer to the kernel documentation located in /usr/ src/linux/Documentation/kernel-parameters.txt . Tip: Obtaining Kernel Documentation Install the kernel-source package to view the kernel documentation. There are other ACPI-related kernel parameters that can be entered at the boot prompt prior to booting for installation: acpi=off This parameter disables the complete ACPI subsystem on your computer. This may be useful if your computer cannot handle ACPI or if you think ACPI in your computer causes trouble. acpi=force Always enable ACPI even if your computer has an old BIOS dated before the year 2000. This parameter also enables ACPI if it is set in addition to acpi=off . acpi=noirq Do not use ACPI for IRQ routing. acpi=ht 611 Fails to Boot SLES 12 SP4Run only enough ACPI to enable hyper-threading. acpi=strict Be less tolerant of platforms that are not strictly ACPI specication compliant. pci=noacpi Disable PCI IRQ routing of the new ACPI system. pnpacpi=off This option is for serial or parallel problems when your BIOS setup contains wrong interrupts or ports. notsc Disable the time stamp counter. This option can be used to work around timing problems on your systems. It is a recent feature, if you see regressions on your machine, especially time related or even total hangs, this option is worth a try. nohz=off Disable the nohz feature. If your machine hangs, this option may help. Otherwise it is of no use. Once you have determined the right parameter combination, YaST automatically writes them to the boot loader conguration to make sure that the system boots properly next time. If unexplainable errors occur when the kernel is loaded or during the installation, select Memory Test in the boot menu to check the memory. If Memory Test returns an error, it is usually a hardware error. 41.2.5 Fails to Launch Graphical Installer After you insert the medium into your drive and reboot your machine, the installation screen comes up, but after you select Installation, the graphical installer does not start. There are several ways to deal with this situation: Try to select another screen resolution for the installation dialogs. Select Text Mode for installation. Do a remote installation via VNC using the graphical installer. PROCEDURE 41.3: CHANGE SCREEN RESOLUTION FOR INSTALLATION 1. Boot for installation. 612 Fails to Launch Graphical Installer SLES 12 SP42. Press F3 to open a menu from which to select a lower resolution for installation purposes. 3. Select Installation and proceed with the installation as described in Book “Deployment Guide”, Chapter 6 “Installation with YaST”. PROCEDURE 41.4: INSTALLATION IN TEXT MODE 1. Boot for installation. 2. Press F3 and select Text Mode. 3. Select Installation and proceed with the installation as described in Book “Deployment Guide”, Chapter 6 “Installation with YaST”. PROCEDURE 41.5: VNC INSTALLATION 1. Boot for installation. 2. Enter the following text at the boot options prompt: vnc=1 vncpassword=SOME_PASSWORD Replace SOME_PASSWORD with the password to use for VNC installation. 3. Select Installation then press Enter to start the installation. Instead of starting right into the graphical installation routine, the system continues to run in a text mode, then halts, displaying a message containing the IP address and port number at which the installer can be reached via a browser interface or a VNC viewer application. 4. If using a browser to access the installer, launch the browser and enter the address information provided by the installation routines on the future SUSE Linux Enterprise Server machine and press Enter : http://IP_ADDRESS_OF_MACHINE:5801 A dialog opens in the browser window prompting you for the VNC password. Enter it and proceed with the installation as described in Book “Deployment Guide”, Chapter 6 “Installation with YaST”. Important: Cross-platform Support Installation via VNC works with any browser under any operating system, provided Java support is enabled. 613 Fails to Launch Graphical Installer SLES 12 SP4Provide the IP address and password to your VNC viewer when prompted. A window opens, displaying the installation dialogs. Proceed with the installation as usual. 41.2.6 Only Minimalistic Boot Screen Started You inserted the medium into the drive, the BIOS routines are nished, but the system does not start with the graphical boot screen. Instead it launches a very minimalistic text-based interface. This may happen on any machine not providing sucient graphics memory for rendering a graphical boot screen. Although the text boot screen looks minimalistic, it provides nearly the same functionality as the graphical one: Boot Options Unlike the graphical interface, the dierent boot options cannot be selected using the cursor keys of your keyboard. The boot menu of the text mode boot screen oers some keywords to enter at the boot prompt. These keywords map to the options oered in the graphical version. Enter your choice and press Enter to launch the boot process. Custom Boot Options After selecting a boot option, enter the appropriate keyword at the boot prompt or enter some custom boot options as described in Section  41.2.4, “Fails to Boot”. To launch the installation process, press Enter . Screen Resolutions Use the function keys ( F1 ... F12 ) to determine the screen resolution for installation. If you need to boot in text mode, choose F3 . 41.2.7 Log Files For more information about log les that are created during installation, see Section  40.5, “Gathering Information during the Installation”. 614 Only Minimalistic Boot Screen Started SLES 12 SP441.3 Boot Problems Boot problems are situations when your system does not boot properly (does not boot to the expected target and login screen). 41.3.1 The GRUB 2 Boot Loader Fails to Load If the hardware is functioning properly, it is possible that the boot loader is corrupted and Linux cannot start on the machine. In this case, it is necessary to repair the boot loader. To do so, you need to start the Rescue System as described in Section 41.6.2, “Using the Rescue System” and follow the instructions in Section 41.6.2.4, “Modifying and Re-installing the Boot Loader”. Alternatively, you can use the Rescue System to x the boot loader as follows. Boot your machine from the installation media. In the boot screen, choose More Boot Linux System. Select the disk containing the installed system and kernel with the default kernel options. When the system is booted, start YaST and switch to System Boot Loader. Make sure that the Write generic Boot Code to MBR option is enabled, and click OK. This xes the corrupted boot loader by overwriting it, or installs the boot loader if it is missing. Other reasons for the machine not booting may be BIOS-related: BIOS Settings Check your BIOS for references to your hard disk. GRUB 2 may simply not be started if the hard disk itself cannot be found with the current BIOS settings. BIOS Boot Order Check whether your system''s boot order includes the hard disk. If the hard disk option was not enabled, your system may install properly, but fails to boot when access to the hard disk is required. 41.3.2 No Graphical Login If the machine starts, but does not boot into the graphical login manager, anticipate problems either with the choice of the default systemd target or the conguration of the X Window System. To check the current systemd default target run the command sudo systemctl get-default . If the value returned is not graphical.target , run the command sudo systemctl isolate 615 Boot Problems SLES 12 SP4graphical.target . If the graphical login screen starts, log in and start YaST System Services Manager and set the Default System Target to Graphical Interface. From now on the system should boot into the graphical login screen. If the graphical login screen does not start even if having booted or switched to the graphical target, your desktop or X Window software is probably miscongured or corrupted. Examine the log les at /var/log/Xorg.*.log for detailed messages from the X server as it attempted to start. If the desktop fails during start, it may log error messages to the system journal that can be queried with the command journalctl (see Chapter 15, journalctl: Query the systemd Journal for more information). If these error messages hint at a conguration problem in the X server, try to x these issues. If the graphical system still does not come up, consider reinstalling the graphical desktop. 41.3.3 Root Btrfs Partition Cannot Be Mounted If a btrfs root partition becomes corrupted, try the following options: Mount the partition with the -o recovery option. If that fails, run btrfs-zero-log on your root partition. 41.3.4 Force Checking Root Partitions If the root partition becomes corrupted, use the parameter forcefsck on the boot prompt. This passes the option -f (force) to the fsck command. 41.4 Login Problems Login problems occur when your machine does boot to the expected welcome screen or login prompt, but refuses to accept the user name and password, or accepts them but then does not behave properly (fails to start the graphic desktop, produces errors, drops to a command line, etc.). 616 Root Btrfs Partition Cannot Be Mounted SLES 12 SP441.4.1 Valid User Name and Password Combinations Fail This usually occurs when the system is congured to use network authentication or directory services and, for some reason, cannot retrieve results from its congured servers. The root user, as the only local user, is the only user that can still log in to these machines. The following are some common reasons a machine appears functional but cannot process logins correctly: The network is not working. For further directions on this, turn to Section 41.5, “Network Problems”. DNS is not working at the moment (which prevents GNOME from working and the system from making validated requests to secure servers). One indication that this is the case is that the machine takes an extremely long time to respond to any action. Find more information about this topic in Section 41.5, “Network Problems”. If the system is congured to use Kerberos, the system''s local time may have drifted past the accepted variance with the Kerberos server time (this is typically 300 seconds). If NTP (network time protocol) is not working properly or local NTP servers are not working, Kerberos authentication ceases to function because it depends on common clock synchronization across the network. The system''s authentication conguration is miscongured. Check the PAM conguration les involved for any typographical errors or misordering of directives. For additional background information about PAM and the syntax of the conguration les involved, refer to Book “Security Guide”, Chapter 2 “Authentication with PAM”. The home partition is encrypted. Find more information about this topic in Section 41.4.3, “Login to Encrypted Home Partition Fails”. In all cases that do not involve external network problems, the solution is to reboot the system into single-user mode and repair the conguration before booting again into operating mode and attempting to log in again. To boot into single-user mode: 1. Reboot the system. The boot screen appears, oering a prompt. 2. Press Esc to exit the splash screen and get to the GRUB 2 text-based menu. 3. Press B to enter the GRUB 2 editor. 4. Add the following parameter to the line containing the kernel parameters: systemd.unit=rescue.target 617 Valid User Name and Password Combinations Fail SLES 12 SP45. Press F10 . 6. Enter the user name and password for root . 7. Make all the necessary changes. 8. Boot into the full multiuser and network mode by entering systemctl isolate graphical.target at the command line. 41.4.2 Valid User Name and Password Not Accepted This is by far the most common problem users encounter, because there are many reasons this can occur. Depending on whether you use local user management and authentication or network authentication, login failures occur for dierent reasons. Local user management can fail for the following reasons: The user may have entered the wrong password. The user''s home directory containing the desktop conguration les is corrupted or write protected. There may be problems with the X Window System authenticating this particular user, especially if the user''s home directory has been used with another Linux distribution prior to installing the current one. To locate the reason for a local login failure, proceed as follows: 1. Check whether the user remembered his password correctly before you start debugging the whole authentication mechanism. If the user may not remember his password correctly, use the YaST User Management module to change the user''s password. Pay attention to the Caps Lock key and unlock it, if necessary. 2. Log in as root and check the system journal with journalctl -e for error messages of the login process and of PAM. 3. Try to log in from a console (using Ctrl – Alt – F1 ). If this is successful, the blame cannot be put on PAM, because it is possible to authenticate this user on this machine. Try to locate any problems with the X Window System or the GNOME desktop. 618 Valid User Name and Password Not Accepted SLES 12 SP44. If the user''s home directory has been used with another Linux distribution, remove the Xauthority le in the user''s home. Use a console login via Ctrl – Alt – F1 and run rm .Xauthority as this user. This should eliminate X authentication problems for this user. Try graphical login again. In the following, common reasons a network authentication for a particular user may fail on a specic machine are listed: The user may have entered the wrong password. The user name exists in the machine''s local authentication les and is also provided by a network authentication system, causing conicts. The home directory exists but is corrupt or unavailable. Perhaps it is write protected or is on a server that is inaccessible at the moment. The user does not have permission to log in to that particular host in the authentication system. The machine has changed host names, for whatever reason, and the user does not have permission to log in to that host. The machine cannot reach the authentication server or directory server that contains that user''s information. There may be problems with the X Window System authenticating this particular user, especially if the user''s home has been used with another Linux distribution prior to installing the current one. To locate the cause of the login failures with network authentication, proceed as follows: 1. Check whether the user remembered their password correctly before you start debugging the whole authentication mechanism. 2. Determine the directory server which the machine relies on for authentication and make sure that it is up and running and properly communicating with the other machines. 3. Determine that the user''s user name and password work on other machines to make sure that his authentication data exists and is properly distributed. 619 Valid User Name and Password Not Accepted SLES 12 SP44. See if another user can log in to the misbehaving machine. If another user can log in without diculty or if root can log in, log in and examine the system journal with journalctl -e> le. Locate the time stamps that correspond to the login attempts and determine if PAM has produced any error messages. 5. Try to log in from a console (using Ctrl – Alt – F1 ). If this is successful, the problem is not with PAM or the directory server on which the user''s home is hosted, because it is possible to authenticate this user on this machine. Try to locate any problems with the X Window System or the GNOME desktop. 6. If the user''s home directory has been used with another Linux distribution, remove the Xauthority le in the user''s home. Use a console login via Ctrl – Alt – F1 and run rm .Xauthority as this user. This should eliminate X authentication problems for this user. Try graphical login again. 41.4.3 Login to Encrypted Home Partition Fails It is recommended to use an encrypted home partition for laptops. If you cannot log in to your laptop, the reason is usually simple: your partition could not be unlocked. During the boot time, you need to enter the passphrase to unlock your encrypted partition. If you do not enter it, the boot process continues, leaving the partition locked. To unlock your encrypted partition, proceed as follows: 1. Switch to the text console with Ctrl – Alt – F1 . 2. Become root . 3. Restart the unlocking process again with: systemctl restart home.mount 4. Enter your passphrase to unlock your encrypted partition. 5. Exit the text console and switch back to the login screen with Alt – F7 . 6. Log in as usual. 620 Login to Encrypted Home Partition Fails SLES 12 SP441.5 Network Problems Many problems of your system may be network-related, even though they do not seem to be at rst. For example, the reason for a system not allowing users to log in may be a network problem of some kind. This section introduces a simple checklist you can apply to identify the cause of any network problem encountered. PROCEDURE 41.6: HOW TO IDENTIFY NETWORK PROBLEMS When checking the network connection of your machine, proceed as follows: 1. If you use an Ethernet connection, check the hardware rst. Make sure that your network cable is properly plugged into your computer and router (or hub, etc.). The control lights next to your Ethernet connector are normally both be active. If the connection fails, check whether your network cable works with another machine. If it does, your network card causes the failure. If hubs or switches are included in your network setup, they may be faulty, as well. 2. If using a wireless connection, check whether the wireless link can be established by other machines. If not, contact the wireless network''s administrator. 3. Once you have checked your basic network connectivity, try to nd out which service is not responding. Gather the address information of all network servers needed in your setup. Either look them up in the appropriate YaST module or ask your system administrator. The following list gives some typical network servers involved in a setup together with the symptoms of an outage. DNS (Name Service) A broken or malfunctioning name service aects the network''s functionality in many ways. If the local machine relies on any network servers for authentication and these servers cannot be found because of name resolution issues, users would not even be able to log in. Machines in the network managed by a broken name server would not be able to “see” each other and communicate. NTP (Time Service) A malfunctioning or completely broken NTP service could aect Kerberos authentication and X server functionality. NFS (File Service) 621 Network Problems SLES 12 SP4If any application needs data stored in an NFS mounted directory, it cannot start or function properly if this service was down or miscongured. In the worst case scenario, a user''s personal desktop conguration would not come up if their home directory containing the .gconf subdirectory could not be found because of a faulty NFS server. Samba (File Service) If any application needs data stored in a directory on a faulty Samba server, it cannot start or function properly. NIS (User Management) If your SUSE Linux Enterprise Server system relies on a faulty NIS server to provide the user data, users cannot log in to this machine. LDAP (User Management) If your SUSE Linux Enterprise Server system relies on a faulty LDAP server to provide the user data, users cannot log in to this machine. Kerberos (Authentication) Authentication will not work and login to any machine fails. CUPS (Network Printing) Users cannot print. 4. Check whether the network servers are running and whether your network setup allows you to establish a connection: Important: Limitations The debugging procedure described below only applies to a simple network server/ client setup that does not involve any internal routing. It assumes both server and client are members of the same subnet without the need for additional routing. a. Use ping IP_ADDRESS/HOSTNAME (replace with the host name or IP address of the server) to check whether each one of them is up and responding to the network. If this command is successful, it tells you that the host you were looking for is up and running and that the name service for your network is congured correctly. 622 Network Problems SLES 12 SP4If ping fails with destination host unreachable , either your system or the desired server is not properly congured or down. Check whether your system is reachable by running ping IP address or YOUR_HOSTNAME from another machine. If you can reach your machine from another machine, it is the server that is not running or not congured correctly. If ping fails with unknown host , the name service is not congured correctly or the host name used was incorrect. For further checks on this matter, refer to Step 4.b. If ping still fails, either your network card is not congured correctly or your network hardware is faulty. b. Use host HOSTNAME to check whether the host name of the server you are trying to connect to is properly translated into an IP address and vice versa. If this command returns the IP address of this host, the name service is up and running. If the host command fails, check all network conguration les relating to name and address resolution on your host: /etc/resolv.conf This le is used to keep track of the name server and domain you are currently using. It can be modied manually or automatically adjusted by YaST or DHCP. Automatic adjustment is preferable. However, make sure that this le has the following structure and all network addresses and domain names are correct: search FULLY_QUALIFIED_DOMAIN_NAME nameserver IPADDRESS_OF_NAMESERVER This le can contain more than one name server address, but at least one of them must be correct to provide name resolution to your host. If needed, adjust this le using the YaST Network Settings module (Hostname/DNS tab). If your network connection is handled via DHCP, enable DHCP to change host name and name service information by selecting Set Hostname via DHCP (can be set globally for any interface or per interface) and Update Name Servers and Search List via DHCP in the YaST Network Settings module (Hostname/DNS tab). /etc/nsswitch.conf This le tells Linux where to look for name service information. It should look like this: ... 623 Network Problems SLES 12 SP4hosts: files dns networks: files dns ... The dns entry is vital. It tells Linux to use an external name server. Normally, these entries are automatically managed by YaST, but it would be prudent to check. If all the relevant entries on the host are correct, let your system administrator check the DNS server conguration for the correct zone information. For detailed information about DNS, refer to Chapter 26, The Domain Name System. If you have made sure that the DNS conguration of your host and the DNS server are correct, proceed with checking the conguration of your network and network device. c. If your system cannot establish a connection to a network server and you have excluded name service problems from the list of possible culprits, check the conguration of your network card. Use the command ip addr show NETWORK_DEVICE to check whether this device was properly congured. Make sure that the inet address with the netmask ( /MASK ) is congured correctly. An error in the IP address or a missing bit in your network mask would render your network conguration unusable. If necessary, perform this check on the server as well. d. If the name service and network hardware are properly congured and running, but some external network connections still get long time-outs or fail entirely, use traceroute FULLY_QUALIFIED_DOMAIN_NAME (executed as root ) to track the network route these requests are taking. This command lists any gateway (hop) that a request from your machine passes on its way to its destination. It lists the response time of each hop and whether this hop is reachable. Use a combination of traceroute and ping to track down the culprit and let the administrators know. Once you have identied the cause of your network trouble, you can resolve it yourself (if the problem is located on your machine) or let the system administrators of your network know about your ndings so they can recongure the services or repair the necessary systems. 624 Network Problems SLES 12 SP441.5.1 NetworkManager Problems If you have a problem with network connectivity, narrow it down as described in Procedure 41.6, “How to Identify Network Problems”. If NetworkManager seems to be the culprit, proceed as follows to get logs providing hints on why NetworkManager fails: 1. Open a shell and log in as root . 2. Restart the NetworkManager: systemctl restart Network.Manager 3. Open a Web page, for example, http://www.opensuse.org as normal user to see, if you can connect. 4. Collect any information about the state of NetworkManager in /var/log/ NetworkManager . For more information about NetworkManager, refer to Chapter 37, Using NetworkManager. 41.6 Data Problems Data problems are when the machine may or may not boot properly but, in either case, it is clear that there is data corruption on the system and that the system needs to be recovered. These situations call for a backup of your critical data, enabling you to recover the system state from before your system failed. 41.6.1 Managing Partition Images Sometimes you need to perform a backup from an entire partition or even hard disk. Linux comes with the dd tool which can create an exact copy of your disk. Combined with gzip you save some space. PROCEDURE 41.7: BACKING UP AND RESTORING HARD DISKS 1. Start a Shell as user root . 2. Select your source device. Typically this is something like /dev/sda (labeled as SOURCE ). 625 NetworkManager Problems SLES 12 SP43. Decide where you want to store your image (labeled as BACKUP_PATH ). It must be dierent from your source device. In other words: if you make a backup from /dev/sda , your image le must not to be stored under /dev/sda . 4. Run the commands to create a compressed image le: dd if=/dev/SOURCE | gzip > /BACKUP_PATH/image.gz 5. Restore the hard disk with the following commands: gzip -dc /BACKUP_PATH/image.gz | dd of=/dev/SOURCE If you only need to back up a partition, replace the SOURCE placeholder with your respective partition. In this case, your image le can lie on the same hard disk, but on a dierent partition. 41.6.2 Using the Rescue System There are several reasons a system could fail to come up and run properly. A corrupted le system following a system crash, corrupted conguration les, or a corrupted boot loader conguration are the most common ones. To help you to resolve these situations, SUSE Linux Enterprise Server contains a rescue system that you can boot. The rescue system is a small Linux system that can be loaded into a RAM disk and mounted as root le system, allowing you to access your Linux partitions from the outside. Using the rescue system, you can recover or modify any important aspect of your system. Manipulate any type of conguration le. Check the le system for defects and start automatic repair processes. Access the installed system in a “change root” environment. Check, modify, and re-install the boot loader conguration. Recover from a badly installed device driver or unusable kernel. Resize partitions using the parted command. Find more information about this tool at the GNU Parted Web site http://www.gnu.org/software/parted/parted.html . The rescue system can be loaded from various sources and locations. The simplest option is to boot the rescue system from the original installation medium. 626 Using the Rescue System SLES 12 SP4Note: IBM z Systems Starting the Rescue System On IBM z Systems the installation system can be used for rescue purposes. To start the rescue system follow the instructions in Section 41.7, “IBM z Systems: Using initrd as a Rescue System”. 1. Insert the installation medium into your DVD drive. 2. Reboot the system. 3. At the boot screen, press F4 and choose DVD-ROM. Then choose Rescue System from the main menu. 4. Enter root at the Rescue: prompt. A password is not required. If your hardware setup does not include a DVD drive, you can boot the rescue system from a network source. The following example applies to a remote boot scenario—if using another boot medium, such as a DVD, modify the info le accordingly and boot as you would for a normal installation. 1. Enter the conguration of your PXE boot setup and add the lines install=PROTOCOL:// INSTSOURCE and rescue=1 . If you need to start the repair system, use repair=1 instead. As with a normal installation, PROTOCOL stands for any of the supported network protocols (NFS, HTTP, FTP, etc.) and INSTSOURCE for the path to your network installation source. 2. Boot the system using “Wake on LAN”, as described in Book “Deployment Guide”, Chapter 9 “Preparing the Boot of the Target System”, Section 9.7 “Using Wake-on-LAN for Remote Wakeups”. 3. Enter root at the Rescue: prompt. A password is not required. Once you have entered the rescue system, you can use the virtual consoles that can be reached with Alt – F1 to Alt – F6 . A shell and other useful utilities, such as the mount program, are available in the /bin directory. The /sbin directory contains important le and network utilities for reviewing and repairing the le system. This directory also contains the most important binaries for system maintenance, such as fdisk , mkfs , mkswap , mount , and shutdown , ip and ss for maintaining the network. The directory /usr/bin contains the vi editor, nd, less, and SSH. To see the system messages, either use the command dmesg or view the system log with journalctl . 627 Using the Rescue System SLES 12 SP441.6.2.1 Checking and Manipulating Configuration Files As an example for a conguration that might be xed using the rescue system, imagine you have a broken conguration le that prevents the system from booting properly. You can x this using the rescue system. To manipulate a conguration le, proceed as follows: 1. Start the rescue system using one of the methods described above. 2. To mount a root le system located under /dev/sda6 to the rescue system, use the following command: mount /dev/sda6 /mnt All directories of the system are now located under /mnt 3. Change the directory to the mounted root le system: cd /mnt 4. Open the problematic conguration le in the vi editor. Adjust and save the conguration. 5. Unmount the root le system from the rescue system: umount /mnt 6. Reboot the machine. 41.6.2.2 Repairing and Checking File Systems Generally, le systems cannot be repaired on a running system. If you encounter serious problems, you may not even be able to mount your root le system and the system boot may end with a “kernel panic”. In this case, the only way is to repair the system from the outside. The system contains the utilities to check and repair the btrfs , ext2 , ext3 , ext4 , reiserfs , xfs , dosfs , and vfat le systems. Look for the command fsck. FILESYSTEM , for example, if you need a le system check for btrfs , use fsck.btrfs . 628 Using the Rescue System SLES 12 SP441.6.2.3 Accessing the Installed System If you need to access the installed system from the rescue system, you need to do this in a change root environment. For example, to modify the boot loader conguration, or to execute a hardware conguration utility. To set up a change root environment based on the installed system, proceed as follows: 1. Tip: Import LVM Volume Groups If you are using an LVM setup (refer to Book “Storage Administration Guide” for more general details), import all existing volume groups in order to be able to nd and mount the device(s): rootvgimport -a Run lsblk to check which node corresponds to the root partition. It is /dev/sda2 in our example: lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 149,1G 0 disk ├─sda1 8:1 0 2G 0 part [SWAP] ├─sda2 8:2 0 20G 0 part / └─sda3 8:3 0 127G 0 part └─cr_home 254:0 0 127G 0 crypt /home 2. Mount the root partition from the installed system: mount /dev/sda2 /mnt 3. Mount /proc , /dev , and /sys partitions: mount -t proc none /mnt/proc mount --rbind /dev /mnt/dev mount --rbind /sys /mnt/sys 4. Now you can “change root” into the new environment, keeping the bash shell: chroot /mnt /bin/bash 629 Using the Rescue System SLES 12 SP45. Finally, mount the remaining partitions from the installed system: mount -a 6. Now you have access to the installed system. Before rebooting the system, unmount the partitions with umount -a and leave the “change root” environment with exit . Warning: Limitations Although you have full access to the les and applications of the installed system, there are some limitations. The kernel that is running is the one that was booted with the rescue system, not with the change root environment. It only supports essential hardware and it is not possible to add kernel modules from the installed system unless the kernel versions are identical. Always check the version of the currently running (rescue) kernel with uname -r and then nd out if a matching subdirectory exists in the /lib/modules directory in the change root environment. If yes, you can use the installed modules, otherwise you need to supply their correct versions on other media, such as a ash disk. Most often the rescue kernel version diers from the installed one — then you cannot simply access a sound card, for example. It is also not possible to start a graphical user interface. Also note that you leave the “change root” environment when you switch the console with Alt – F1 to Alt – F6 . 41.6.2.4 Modifying and Re-installing the Boot Loader Sometimes a system cannot boot because the boot loader conguration is corrupted. The start- up routines cannot, for example, translate physical drives to the actual locations in the Linux le system without a working boot loader. To check the boot loader conguration and re-install the boot loader, proceed as follows: 1. Perform the necessary steps to access the installed system as described in Section 41.6.2.3, “Accessing the Installed System”. 2. Check that the GRUB 2 boot loader is installed on the system. If not, install the package grub2 and run grub2-install /dev/sda 630 Using the Rescue System SLES 12 SP43. Check whether the following les are correctly congured according to the GRUB  2 conguration principles outlined in Chapter 12, The Boot Loader GRUB 2 and apply xes if necessary. /etc/default/grub /boot/grub2/device.map (optional le, only present if created manually) /boot/grub2/grub.cfg (this le is generated, do not edit) /etc/sysconfig/bootloader 4. Re-install the boot loader using the following command sequence: grub2-mkconfig -o /boot/grub2/grub.cfg 5. Unmount the partitions, log out from the “change root” environment, and reboot the system: umount -a exit reboot 41.6.2.5 Fixing Kernel Installation A kernel update may introduce a new bug which can impact the operation of your system. For example a driver for a piece of hardware in your system may be faulty, which prevents you from accessing and using it. In this case, revert to the last working kernel (if available on the system) or install the original kernel from the installation media. Tip: How to Keep Last Kernels after Update To prevent failures to boot after a faulty kernel update, use the kernel multiversion feature and tell libzypp which kernels you want to keep after the update. For example to always keep the last two kernels and the currently running one, add multiversion.kernels = latest,latest-1,running to the /etc/zypp/zypp.conf le. See Book “Deployment Guide”, Chapter  15 “Installing Multiple Kernel Versions” for more information. 631 Using the Rescue System SLES 12 SP4A similar case is when you need to re-install or update a broken driver for a device not supported by SUSE Linux Enterprise Server. For example when a hardware vendor uses a specic device, such as a hardware RAID controller, which needs a binary driver to be recognized by the operating system. The vendor typically releases a Driver Update Disk (DUD) with the xed or updated version of the required driver. In both cases you need to access the installed system in the rescue mode and x the kernel related problem, otherwise the system may fail to boot correctly: 1. Boot from the SUSE Linux Enterprise Server installation media. 2. If you are recovering after a faulty kernel update, skip this step. If you need to use a driver update disk (DUD), press F6 to load the driver update after the boot menu appears, and choose the path or URL to the driver update and conrm with Yes. 3. Choose Rescue System from the boot menu and press Enter . If you chose to use DUD, you will be asked to specify where the driver update is stored. 4. Enter root at the Rescue: prompt. A password is not required. 5. Manually mount the target system and “change root” into the new environment. For more information, see Section 41.6.2.3, “Accessing the Installed System”. 6. If using DUD, install/re-install/update the faulty device driver package. Always make sure the installed kernel version exactly matches the version of the driver you are installing. If xing faulty kernel update installation, you can install the original kernel from the installation media with the following procedure. a. Identify your DVD device with hwinfo --cdrom and mount it with mount /dev/ sr0 /mnt . b. Navigate to the directory where your kernel les are stored on the DVD, for example cd /mnt/suse/x86_64/ . c. Install required kernel-* , kernel-*-base , and kernel-*-extra packages of your avor with the rpm -i command. 7. Update conguration les and reinitialize the boot loader if needed. For more information, see Section 41.6.2.4, “Modifying and Re-installing the Boot Loader”. 8. Remove any bootable media from the system drive and reboot. 632 Using the Rescue System SLES 12 SP441.7 IBM z Systems: Using initrd as a Rescue System If the kernel of the SUSE® Linux Enterprise Server for IBM z Systems is upgraded or modied, it is possible to reboot the system accidentally in an inconsistent state, so standard procedures of IPLing the installed system fail. In such a case, you may use the installation system for rescue purposes. IPL the SUSE Linux Enterprise Server for IBM z Systems installation system as described in Book “Deployment Guide”, Chapter 4 “Installation on IBM z Systems”, Section 4.2 “Preparing for Installation”. Choose Start Installation and enter all required parameters. After the installation system has loaded and you are asked which display type to use to control the installation, select SSH . Now you can log in to the system with SSH as root without a password. In this state, no disks are congured. You need to congure them before you can proceed. PROCEDURE 41.8: CONFIGURING DASDS 1. Congure DASDs with the following command: dasd_configure 0.0.0150 1 0 0.0.0150 is the channel to which the DASD is connected. The 1 means activate the disk (a 0 at this place would deactivate the disk). The 0 stands for “no DIAG mode” for the disk (a 1 here would enable DAIG access to the disk). 2. Now the DASD is online (check with cat /proc/partitions ) and can used for subsequent commands. PROCEDURE 41.9: CONFIGURING A ZFCP DISK 1. To congure a zFCP disk, it is necessary to rst congure the zFCP adapter. Do this with the following command: zfcp_host_configure 0.0.4000 1 0.0.4000 is the channel to which the adapter is attached and 1 stands for activate (a 0 here would deactivate the adapter). 2. After the adapter is activated, a disk can be congured. Do this with the following command: zfcp_disk_configure 0.0.4000 1234567887654321 8765432100000000 1 633 IBM z Systems: Using initrd as a Rescue System SLES 12 SP40.0.4000 is the previously-used channel ID, 1234567887654321 is the WWPN (World wide Port Number), and 8765432100000000 is the LUN (logical unit number). The 1 stands for activating the disk (a 0 here would deactivate the disk). 3. Now the zFCP disk is online (check with cat /proc/partitions ) and can used for subsequent commands. Now the rescue system is fully set up and you can start repairing the installed system. See Section 41.6.2, “Using the Rescue System” for instructions on how to repair the most common issues. 634 IBM z Systems: Using initrd as a Rescue System SLES 12 SP4A Documentation Updates This chapter lists content changes for this document. This manual was updated on the following dates: Section A.2, “December 2018 (Initial Release of SUSE Linux Enterprise Server 12 SP4)” Section A.3, “October 2018 (Documentation Maintenance Update for SUSE Linux Enterprise Server 12 SP3)” Section A.4, “September 2017 (Initial Release of SUSE Linux Enterprise Server 12 SP3)” Section A.5, “November 2016 (Initial Release of SUSE Linux Enterprise Server 12 SP2)” Section A.6, “March 2016 (Documentation Maintenance Update for SUSE Linux Enterprise Server 12 SP1)” Section A.7, “December 2015 (Initial Release of SUSE Linux Enterprise Server 12 SP1)” Section A.8, “February 2015 (Documentation Maintenance Update)” Section A.9, “October 2014 (Initial Release of SUSE Linux Enterprise Server 12)” A.1 February 2019 (Documentation Maintenance Update for SUSE Linux Enterprise Server 12 SP4) Bugfixes Added a note about unsupported bonding modes on IBM POWER to Section  16.7, “Setting Up Bonding Devices” (https://bugzilla.suse.com/show_bug.cgi?id=1070446 ). A.2 December 2018 (Initial Release of SUSE Linux Enterprise Server 12 SP4) Chapter 24, Persistent Memory New chapter (Fate #326330). Bugfixes February 2019 (Documentation Maintenance Update for SUSE Linux Enterprise Server 12 635 SP4) SLES 12 SP4Adding drivers to /etc/dracut.conf.d/01-dist.conf overrides dracut default settings (https://bugzilla.suse.com/show_bug.cgi?id=1112786 ). In Chapter 12, The Boot Loader GRUB 2, claried the function of /etc/sysconfig/ bootloader (https://bugzilla.suse.com/show_bug.cgi?id=1079418 ). A.3 October 2018 (Documentation Maintenance Update for SUSE Linux Enterprise Server 12 SP3) General Changes to the Documentation Improved consistency of Docker terminology throughout the documentation. This includes renaming a guide to Docker Open Source Engine Guide. Chapter 10, Introduction to the Boot Process Completely rewrote the chapter and added IBM z  Systems-Specic information (https://bugzilla.suse.com/show_bug.cgi?id=1046514 ). Chapter 12, The Boot Loader GRUB 2 Added Section 8.4.2, “VNC Session Initiated Using vncmanager” (Fate #319319). Updated command to list video modes in grub to videoinfo , vbeinfo is outdated. See Section 12.2.2, “The File /etc/default/grub” (https://bugzilla.suse.com/ show_bug.cgi?id=1074026 ). Replaced grub2-reboot with grub2-once to set the default boot entry for the next boot only, see Section 12.2.2, “The File /etc/default/grub” (https://bugzilla.suse.com/ show_bug.cgi?id=1071210 ). Chapter 14, 32-Bit and 64-Bit Applications in a 64-Bit System Environment Removed documentation about compiling 32-bit applications on a 64-bit system. This is not supported with SUSE Linux Enterprise Server (https://bugzilla.suse.com/ show_bug.cgi?id=1092434 ). Chapter 16, Basic Networking October 2018 (Documentation Maintenance Update for SUSE Linux Enterprise Server 12 636 SP3) SLES 12 SP4Added descriptions for all bonding modes to Section 16.7, “Setting Up Bonding Devices” (Doc Comment #35319). Chapter 21, Dynamic Kernel Device Management with udev Explained dierent locations for udev rule les, see Section  21.6, “Influencing Kernel Device Event Handling with udev Rules” (https://bugzilla.suse.com/show_bug.cgi? id=1103082 ). Fixed a variable name in Section  21.6.2, “Using Substitutions in udev Rules” (https:// bugzilla.suse.com/show_bug.cgi?id=1061131 ). Chapter 22, Live Patching the Linux Kernel Using kGraft POWER is supported for kGraft live patching, see Chapter 22, Live Patching the Linux Kernel Using kGraft (https://bugzilla.suse.com/show_bug.cgi?id=1074844 ). kGraft patches are available for CVSS 7+ vulnerabilities, see Section 22.9, “Scope of SLE Live Patching” (https://bugzilla.suse.com/show_bug.cgi?id=1068181 ). Chapter 28, Sharing File Systems with NFS Added Kerberos performance tuning information (Fate #315348). Bugfixes Adding drivers to /etc/dracut.conf.d/01-dist.conf overrides dracut default settings (https://bugzilla.suse.com/show_bug.cgi?id=1112786 ). Fixed location of 50-udev-default.rules in Section 21.6, “Influencing Kernel Device Event Handling with udev Rules” (https://bugzilla.suse.com/show_bug.cgi?id=1103082 ). Corrected command and its man page reference in Section 13.6.2, “System Log” (https:// bugzilla.suse.com/show_bug.cgi?id=1104266 ). Improved tip about /boot/grub2/custom.cfg in Section  12.2.3, “Scripts in /etc/ grub.d” (https://bugzilla.suse.com/show_bug.cgi?id=1102514 ). Removed references to pure-ftpd from Chapter 33, Setting Up an FTP Server with YaST (https://bugzilla.suse.com/show_bug.cgi?id=1101631 ). October 2018 (Documentation Maintenance Update for SUSE Linux Enterprise Server 12 637 SP3) SLES 12 SP4Removed documentation about compiling 32-bit applications on a 64-bit system in Chapter  14, 32-Bit and 64-Bit Applications in a 64-Bit System Environment. This is not supported with SUSE Linux Enterprise Server (https://bugzilla.suse.com/ show_bug.cgi?id=1092434 ). Added the -alwaysshared option for persistent VNC connection in Procedure 8.2, “Starting a Persistent VNC Session using vncserver” (https://bugzilla.suse.com/ show_bug.cgi?id=1081409 ). Added a tip to Section 30.2.2, “Map Files” that autofs map-les must not be executable (https://bugzilla.suse.com/show_bug.cgi?id=1081377 ). POWER is supported for kGraft live patching, see Chapter 22, Live Patching the Linux Kernel Using kGraft. (https://bugzilla.suse.com/show_bug.cgi?id=1074844 ). List video modes in grub with videoinfo , vbeinfo is outdated. See Section 12.2.2, “The File /etc/default/grub” (https://bugzilla.suse.com/show_bug.cgi? id=1074026 ). Replaced grub2-reboot with grub2-once to set the default boot entry for the next boot only, see Section 12.2.2, “The File /etc/default/grub” (https://bugzilla.suse.com/ show_bug.cgi?id=1071210 ). kGraft patches are available for CVSS 7+ vulnerabilities, see Section 22.9, “Scope of SLE Live Patching” (https://bugzilla.suse.com/show_bug.cgi?id=1068181 ). Added ~/.alias in Section  1.1.1, “Knowing the Bash Configuration Files” (https:// bugzilla.suse.com/show_bug.cgi?id=1062209 ). Fixed a variable name in Section  21.6.2, “Using Substitutions in udev Rules” (https:// bugzilla.suse.com/show_bug.cgi?id=1061131 ). Added tip on importing volume groups in Section 41.6.2.3, “Accessing the Installed System” (https://bugzilla.suse.com/show_bug.cgi?id=1051369 ). Completely rewrote Chapter  10, Introduction to the Boot Process and added IBM z  Systems-specic information (https://bugzilla.suse.com/show_bug.cgi? id=1046514 ). Replaced VGA mode in Figure  12.5, “Kernel Parameters” (https://bugzilla.suse.com/ show_bug.cgi?id=1017753 ). October 2018 (Documentation Maintenance Update for SUSE Linux Enterprise Server 12 638 SP3) SLES 12 SP4Aligned sections and provided more details in Section 12.3.1, “Boot Loader Location and Boot Code Options” (https://bugzilla.suse.com/show_bug.cgi?id=1017737 ). Described boot disk order in Section  12.3.2, “Adjusting the Disk Order” (https:// bugzilla.suse.com/show_bug.cgi?id=1017731 ). Removed a note referencing YaST for *DEFAULT options in Section 12.2.2, “The File / etc/default/grub” (https://bugzilla.suse.com/show_bug.cgi?id=1017728 ). Updated and simplied Section  12.2.3, “Scripts in /etc/grub.d” (https:// bugzilla.suse.com/show_bug.cgi?id=1017726 ). A.4 September 2017 (Initial Release of SUSE Linux Enterprise Server 12 SP3) General Numerous small xes and additions to the documentation, based on technical feedback. Removed all references to the faillog package, which is no longer shipped (https:// bugzilla.suse.com/show_bug.cgi?id=710788 ). Chapter 4, YaST Added a new chapter about the YaST GUI and mentioned advanced key combinations (https://bugzilla.suse.com/show_bug.cgi?id=1010039 ). Chapter 5, YaST in Text Mode Added Section  5.2, “Advanced Key Combinations” (https://bugzilla.suse.com/ show_bug.cgi?id=1010039 ). Chapter 6, Managing Software with Command Line Tools Added Section 6.1.6.2, “Refreshing Repositories” (Fate #319486). Updated Section 6.1.4.1, “Installing All Needed Patches” (Fate #320653). Added Section 6.1.7.3, “zypper info Usage” (Fate #321104). 639 September 2017 (Initial Release of SUSE Linux Enterprise Server 12 SP3) SLES 12 SP4Chapter 7, System Recovery and Snapshot Management with Snapper Mentioned that snapper rollback snapshots are automatically deleted. See Section 7.3, “System Rollback by Booting from Snapshots” and Section 7.3.1, “Snapshots after Rollback” (Fate #321773). In Section  7.5, “Creating and Modifying Snapper Configurations”, added in-depth information on how the minimum root le system size for enabling snapshots is calculated (https://bugzilla.suse.com/show_bug.cgi?id=1036175 ). Mentioned Btrfs default subvolume and its restrictions (https://bugzilla.suse.com/ show_bug.cgi?id=1045884 ). Chapter 8, Remote Access with VNC Fixed information about encrypted communication and added Section 8.5, “Encrypted VNC Communication” on how to set it up (https://bugzilla.suse.com/show_bug.cgi? id=1029117 ). Chapter 9, File Copying with RSync Completely revised former File Synchronization chapter and focused on Rsync. Chapter 13, The systemd Daemon Added the System V init command chkconfig to the comparison table in Section  13.2.2.1, “Enabling/Disabling Services on the Command Line” (Doc Comment #30251). Chapter 16, Basic Networking Fixed several doc comments in Section  16.8, “Setting Up Team Devices for Network Teaming”. Chapter 21, Dynamic Kernel Device Management with udev Fixed udevadm commands. Chapter 22, Live Patching the Linux Kernel Using kGraft Updated Section 22.4, “Patch Lifecycle” (Fate #322212). 640 September 2017 (Initial Release of SUSE Linux Enterprise Server 12 SP3) SLES 12 SP4Chapter 23, Special System Features Removed duplicate content from Section 23.1.4, “Log Files: Package logrotate”. Part II, “Booting a Linux System” Reordered included chapters so that they follow the boot process order. Chapter 34, The Proxy Server Squid Explained the YaST Squid module. Bugfixes Replaced the command to start Apache2, httpd2 , with apache2ctl (https:// bugzilla.suse.com/show_bug.cgi?id=1042437 ). In Section 16.2.5, “For More Information”, corrected a typo in a referenced RFC document (https://bugzilla.suse.com/show_bug.cgi?id=1045881 ). In Section 41.6, “Data Problems”, removed a reference to a YaST module that is no longer shipped (https://bugzilla.suse.com/show_bug.cgi?id=1052675 ). A.5 November 2016 (Initial Release of SUSE Linux Enterprise Server 12 SP2) General The e-mail address for documentation feedback has changed to doc- team@suse.com . The documentation for Docker Open Source Engine has been enhanced and renamed to Docker Guide. Chapter 3, YaST Online Update Mentioned in Section 3.3, “Automatic Online Update” that the automatic online update does not automatically restart the system afterward (Doc Comment #30116). Chapter 6, Managing Software with Command Line Tools 641 November 2016 (Initial Release of SUSE Linux Enterprise Server 12 SP2) SLES 12 SP4zypper patch no longer installs optional patches by default. To install optional patches, use the --with-optional parameter (FATE#320447). Chapter 7, System Recovery and Snapshot Management with Snapper Added /var/cache and /var/lib/libvirt/images to Section 7.1.2, “Directories That Are Excluded from Snapshots” (Fate #320834). Added Section 7.7, “Automatic Snapshot Clean-Up”, which also includes documentation on Snapper''s new quota support (Fate #312751). Added Q: (Fate #318799). Chapter 10, Introduction to the Boot Process Advised users to repair le system in case root le system fails on boot time (FATE#320443). Chapter 12, The Boot Loader GRUB 2 Added a hint on grub-once support of /boot/grub2/custom.cfg to Section 12.2, “Configuration File Structure” (Fate #319632). Added Section 7.3.2, “Accessing and Identifying Snapshot Boot Entries” (Fate #317972 and #318101). Added information about trusted boot support to Section 12.3.1, “Boot Loader Location and Boot Code Options” (Fate #316553). Chapter 16, Basic Networking Added section about Network Teaming (FATE#320468), see Section 16.8, “Setting Up Team Devices for Network Teaming”. Mentioned TUNNEL_DEVICE for Wicked (FATE#317977, Section  16.5.1.5, “Using Tunnels with Wicked”). Chapter 25, Time Synchronization with NTP Added information on the Synchronize without Daemon start-up option. Chroot jail is no longer the default (FATE #320392). Note: NFSv2 642 November 2016 (Initial Release of SUSE Linux Enterprise Server 12 SP2) SLES 12 SP4Added a note about enabling NFSv2 (https://bugzilla.suse.com/show_bug.cgi? id=919708 ). Chapter 34, The Proxy Server Squid Updated chapter for Squid 3.5 (FATE#319674). Section 40.5, “Gathering Information during the Installation” Added section about log les created during installation (FATE#320015). Bugfixes Wrong service names for NFS with Kerberos (https://bugzilla.suse.com/show_bug.cgi? id=983230 ). Live patches are released based on the SUSE CVSS score (https://bugzilla.suse.com/ show_bug.cgi?id=992101 ). A.6 March 2016 (Documentation Maintenance Update for SUSE Linux Enterprise Server 12 SP1) Chapter 10, Introduction to the Boot Process Added a note about initramfs migration from swap to LVM. A.7 December 2015 (Initial Release of SUSE Linux Enterprise Server 12 SP1) General Book “Subscription Management Tool for SLES 12 SP4” is now part of the documentation for SUSE Linux Enterprise Server. Add-ons provided by SUSE have been renamed as modules and extensions. The manuals have been updated to reect this change. Numerous small xes and additions to the documentation, based on technical feedback. March 2016 (Documentation Maintenance Update for SUSE Linux Enterprise Server 12 643 SP1) SLES 12 SP4The registration service has been changed from Novell Customer Center to SUSE Customer Center. In YaST, you will now reach Network Settings via the System group. Network Devices is gone (https://bugzilla.suse.com/show_bug.cgi?id=867809 ). Chapter 7, System Recovery and Snapshot Management with Snapper Added information about the new --sync switch for snapper delete to Section 7.6.4, “Deleting Snapshots” (Fate #317066). Added Section 7.3.2, “Accessing and Identifying Snapshot Boot Entries” (Fate #317972 and Fate #318101). Added a tip to Section 7.3, “System Rollback by Booting from Snapshots” on how to do a rollback to the initial installation state or the state before a system update (Fate #317973 and Fate #317900). Added Section 7.1.3.3, “Creating and Mounting New Subvolumes” (Fate #318805, https:// bugzilla.suse.com/show_bug.cgi?id=910602 ). Chapter 8, Remote Access with VNC Turned a note into a section, added information about VNC using secured protocol by default (Fate #318936), and removed tightvnc as it is fully replaced by tigervnc . All in Section 8.3.1, “Available Configurations”. Chapter 6, Managing Software with Command Line Tools Added Section  6.1.5, “Identifying Processes and Services Using Deleted Files” (Fate #318827). Added more examples of zypper list-patches --cve in Section 6.1.4.1, “Installing All Needed Patches” (Fate #319053). Added Section  6.1.3.6, “Installing Packages from Disabled Repositories” and a tip on removing all debuginfo packages in Section 6.1.3, “Installing and Removing Software with Zypper” (Fate #316287). Added a sentence on announcing the need for the system reboot after specic patch is applied. (Fate #317872). 644 December 2015 (Initial Release of SUSE Linux Enterprise Server 12 SP1) SLES 12 SP4Chapter 15, journalctl: Query the systemd Journal Added section Section 15.6, “Using YaST to Filter the systemd Journal” (Fate #318486). Chapter 12, The Boot Loader GRUB 2 Updated/simplied the whole chapter to match the latest GRUB version, both command line and YaST version. Chapter 11, UEFI (Unified Extensible Firmware Interface) Added Section 11.1.4, “Using Non-Inbox Drivers” (Fate #317593). Chapter 16, Basic Networking Nanny is now on by default in Section 16.5.1.3, “Nanny” (Fate #318977). Added Section  16.6, “Basic Router Setup” (Fate #317121, https://bugzilla.suse.com/ show_bug.cgi?id=870132 ). Added Section 16.9, “Software-Defined Networking with Open vSwitch” (Fate #318497). Chapter 26, The Domain Name System Added Section 26.3.2.9.1, “Adding Reverse Zones” (Doc Comment #1356). Chapter 28, Sharing File Systems with NFS Added tip saying that --bind mount is no longer necessary for NFSv4 mounts in Section 28.3.2, “Exporting File Systems Manually” (Fate #316311). Available Data Synchronization Software Mentioned cloud computing for le synchronization. Chapter 32, The Apache HTTP Server Replaced CA.sh with the explicit openssl command in Section 32.6.1.3, “Getting an Officially Signed Certificate” (Doc Comment #28367). Added Section  32.7, “Running Multiple Apache Instances on the Same Server” (Fate #317786). Updated the chapter to match the latest Apache version 2.4 (Fate #319012). 645 December 2015 (Initial Release of SUSE Linux Enterprise Server 12 SP1) SLES 12 SP4Chapter 41, Common Problems and Their Solutions Improved GRUB 2 re-installation procedure in Section  41.6.2.4, “Modifying and Re- installing the Boot Loader”. Part III, “System” Added Chapter 22, Live Patching the Linux Kernel Using kGraft (Fate #313296 and Fate #313438). Bugfixes Removed obsolete acpid.service (https://bugzilla.suse.com/show_bug.cgi? id=918655 ). Fixed wrong title in Chapter  22, Live Patching the Linux Kernel Using kGraft (https:// bugzilla.suse.com/show_bug.cgi?id=954250 ). Fixed wrong path name in Chapter  32, The Apache HTTP Server (https:// bugzilla.suse.com/show_bug.cgi?id=949395 ). Added a paragraph on secure boot enabled by default in Section 11.1.1, “Implementation on SUSE Linux Enterprise Server” (https://bugzilla.suse.com/show_bug.cgi?id=879486 ). Removed documentation about VNC view-only passwords in Section 8.4, “Persistent VNC Sessions” because they are not available in SUSE Linux Enterprise Server (https:// bugzilla.suse.com/show_bug.cgi?id=941307 ). Fixed procedure to access the installed system in a rescue mode in Section 41.6.2.3, “Accessing the Installed System” (https://bugzilla.suse.com/show_bug.cgi?id=918217 ). Added a new tip on updating the initramfs le after changing the default sysctl conguration in Section  10.2.2.1, “The initramfs file” (https://bugzilla.suse.com/ show_bug.cgi?id=927506 ). Added a tip on preventing wicked from deactivating the network device on NFS roots in Section 28.4.1, “Importing File Systems with YaST” and Section 16.4.1.2.5, “Activating the Network Device” (https://bugzilla.suse.com/show_bug.cgi?id=938152 ). Fixed misleading statement about kernel-FLAVOR-extra in Section 40.6, “Support of Kernel Modules” (http://bugzilla.suse.com/show_bug.cgi?id=922976 ). 646 December 2015 (Initial Release of SUSE Linux Enterprise Server 12 SP1) SLES 12 SP4Btrfs/Snapper: Snapshots with new Subvolumes will not be Deleted ( https:// bugzilla.suse.com/show_bug.cgi?id=910602 ). Btrfs Documentation on Separate Subvolume on /var/lib and Supportability ( https:// bugzilla.suse.com/show_bug.cgi?id=930424 ). A.8 February 2015 (Documentation Maintenance Update) Chapter 13, The systemd Daemon A typo in a command has been xed (https://bugzilla.suse.com/show_bug.cgi?id=900219 ). A.9 October 2014 (Initial Release of SUSE Linux Enterprise Server 12) General Removed all KDE documentation and references because KDE is no longer shipped. Removed all references to SuSEcong, which is no longer supported (Fate #100011). Move from System V init to systemd (Fate #310421). Updated aected parts of the documentation. YaST Runlevel Editor has changed to Services Manager (Fate #312568). Updated aected parts of the documentation. Removed all references to ISDN support, as ISDN support has been removed (Fate #314594). Removed all references to the YaST DSL module as it is no longer shipped (Fate #316264). Removed all references to the YaST Modem module as it is no longer shipped (Fate #316264). Btrfs has become the default le system for the root partition (Fate #315901). Updated aected parts of the documentation. 647 February 2015 (Documentation Maintenance Update) SLES 12 SP4The dmesg now provides human-readable time stamps in ctime() -like format (Fate #316056). Updated aected parts of the documentation. syslog and syslog-ng have been replaced by rsyslog (Fate #316175). Updated aected parts of the documentation. MariaDB is now shipped as the relational database instead of MySQL (Fate #313595). Updated aected parts of the documentation. SUSE-related products are no longer available from http://download.novell.com but from http://download.suse.com . Adjusted links accordingly. Novell Customer Center has been replaced with SUSE Customer Center. Updated aected parts of the documentation. /var/run is mounted as tmpfs (Fate #303793). Updated aected parts of the documentation. The following architectures are no longer supported: IA64 and x86. Updated aected parts of the documentation. The traditional method for setting up the network with ifconfig has been replaced by wicked . Updated aected parts of the documentation. A lot of networking commands are deprecated and have been replaced by newer commands (usually ip ). Updated aected parts of the documentation. arp : ip neighbor ifconfig : ip addr , ip link iptunnel : ip tunnel iwconfig : iw nameif : ip link , ifrename netstat : ss , ip route , ip -s link , ip maddr route : ip route Numerous small xes and additions to the documentation, based on technical feedback. Chapter 3, YaST Online Update 648 October 2014 (Initial Release of SUSE Linux Enterprise Server 12) SLES 12 SP4YaST provides an option to enable or disable the use of delta RPMs (Fate #314867). Before installing patches that require a reboot, you are notied by YaST and can choose how to proceed. Chapter 40, Gathering System Information for Support Added the section Section 40.1, “Displaying Current System Information” (Fate #315869). Added a section about the Supportcong Analysis (SCA) tool and appliance: Section 40.4, “Analyzing System Information” (Fate #315699). Added the section Section 40.6, “Support of Kernel Modules” (http://bugzilla.suse.com/ show_bug.cgi?id=869159 ). Updated and restructured the chapter. Chapter 5, YaST in Text Mode Added information on how to lter and select packages in the software installation module. Chapter 6, Managing Software with Command Line Tools Removed documentation about Zypper''s rug compatibility mode (Fate #317708). Rewrote Section 6.1.7, “Querying Repositories and Packages with Zypper”. Chapter 7, System Recovery and Snapshot Management with Snapper Updated the chapter and added new features (Fate #312751, Fate #316238, Fate #316233, Fate #316232, Fate #316222, Fate #316203, Fate #316222). Added the section Section  7.3, “System Rollback by Booting from Snapshots” (Fate #316231, Fate #316221, Fate #316541, Fate #316522). Chapter 8, Remote Access with VNC The default VNC viewer is now tigervnc . Added corrections on window manager start-up in persistent VNC sessions. Chapter 10, Introduction to the Boot Process 649 October 2014 (Initial Release of SUSE Linux Enterprise Server 12) SLES 12 SP4Signicantly shortened the chapter, because System V init has been replaced by systemd. systemd is now described in a separate chapter: Chapter 13, The systemd Daemon. Chapter 13, The systemd Daemon Added a new chapter on systemd and the YaST Services Manager (Fate #316631, Fate #312568). New section on loading kernel modules (http://bugzilla.suse.com/show_bug.cgi? id=892349 ). Chapter 15, journalctl: Query the systemd Journal Added a new chapter (http://bugzilla.suse.com/show_bug.cgi?id=878352 ). Chapter 12, The Boot Loader GRUB 2 Replaced the GRUB Legacy documentation with a new chapter on GRUB 2. Support for LILO has been dropped. Added new section Section 12.4, “Differences in Terminal Usage on z Systems”. Chapter 11, UEFI (Unified Extensible Firmware Interface) Updated the chapter and added new features (Fate #314510, Fate #316365). Added instructions on where to nd the SUSE Key certicate (Doc Comment #25080). Chapter 17, Printer Operation Updated chapter and section according to new CUPS version and with PDF now being a common printing data format (Fate #314630). Chapter 18, The X Window System Updated the chapter to reect dynamic conguration during each start-up. Updated Section 18.1, “Installing and Configuring Fonts”. Chapter 16, Basic Networking 650 October 2014 (Initial Release of SUSE Linux Enterprise Server 12) SLES 12 SP4NetworkManager is now part of the Workstation Extension: Section  16.4.1.1, “Configuring Global Networking Options” (Fate #316888). Added section about new wicked framework for network conguration: Section 16.5, “Configuring a Network Connection Manually” (Fate #316649). Mentioned additional options that can be added to /etc/resolv.conf : Section 16.5.2, “Configuration Files” (Fate #316048). Chapter 31, SLP Re-wrote chapter to provide signicantly more information on the slptool command. Chapter 26, The Domain Name System The YaST DNS module now supports conguring forwarders (Fate #309036). Chapter 27, DHCP Removed dhcpcd as it is no longer shipped (Fate #316111). Chapter 29, Samba Added section Section 29.8, “Advanced Topics”. Added section Section 29.8.1, “Transparent File Compression on Btrfs”. Added section Section 29.8.2, “Snapshots”. Chapter 28, Sharing File Systems with NFS Conguring NFSv4 shares is now mostly similar to NFSv3, especially the previously required bind mount setting is now deprecated (Fate #315589). Mounting NFS volumes locally on the exporting server is not supported. Chapter 30, On-Demand Mounting with Autofs Added a chapter on autofs (Fate #316185). Chapter 32, The Apache HTTP Server 651 October 2014 (Initial Release of SUSE Linux Enterprise Server 12) SLES 12 SP4Removed references to mono and mod_mono as it was removed from the distribution. Updated the chapter to Apache version 2.4 (Fate #316067). Removed deprecated directive NameVirtualHost and updated Section  32.2.2.1, “Virtual Host Configuration” accordingly. Updated Order , Allow , and Deny directives with standard Require . Removed virtual "Snake Oil" company from Section 32.6, “Setting Up a Secure Web Server with SSL”. Chapter 33, Setting Up an FTP Server with YaST pure-ftpd was dropped (Fate #315176, Fate #316308). Chapter 38, Power Management Removed obsolete references to the pm-utils package. Chapter 41, Common Problems and Their Solutions Added new section Section  41.3.3, “Root Btrfs Partition Cannot Be Mounted” (Fate #308679, Fate #315126). Removed section about deprecated YaST Repair module (Fate #308679). Wi-Fi Configuration Removed chapter about Wi-Fi conguration with YaST as Wi-Fi conguration can be done with NetworkManager: Chapter 37, Using NetworkManager. Tablet PCs Removed deprecated chapter about tablet PCs. Bugfixes Added the section Section 40.6, “Support of Kernel Modules” (http://bugzilla.suse.com/ show_bug.cgi?id=869159 ). Added a new chapter Chapter  15, journalctl: Query the systemd Journal (http:// bugzilla.suse.com/show_bug.cgi?id=878352 ). 652 October 2014 (Initial Release of SUSE Linux Enterprise Server 12) SLES 12 SP4B An Example Network This example network is used across all network-related chapters of the SUSE® Linux Enterprise Server documentation. 653 SLES 12 SP4C GNU Licenses XML for which the DTD and/or processing tools are not generally available, and the machine- This appendix contains the GNU Free generated HTML, PostScript or PDF produced by some word processors for output purposes only. Documentation License version 1.2. The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the GNU Free Documentation License most prominent appearance of the work''s title, preceding the beginning of the body of the text. A section "Entitled XYZ" means a named subunit of the Document whose title either is precisely Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc. 51 Franklin St, Fifth Floor, XYZ or contains XYZ in parentheses following text that translates XYZ in another language. Boston, MA 02110-1301 USA. Everyone is permitted to copy and distribute verbatim copies (Here XYZ stands for a specic section name mentioned below, such as "Acknowledgements", of this license document, but changing it is not allowed. "Dedications", "Endorsements", or "History".) To "Preserve the Title" of such a section when you modify the Document means that it remains a section "Entitled XYZ" according to this 0. PREAMBLE denition. The Document may include Warranty Disclaimers next to the notice which states that this The purpose of this License is to make a manual, textbook, or other functional and useful License applies to the Document. These Warranty Disclaimers are considered to be included document "free" in the sense of freedom: to assure everyone the eective freedom to copy by reference in this License, but only as regards disclaiming warranties: any other implication and redistribute it, with or without modifying it, either commercially or non-commercially. that these Warranty Disclaimers may have is void and has no eect on the meaning of this Secondarily, this License preserves for the author and publisher a way to get credit for their License. work, while not being considered responsible for modications made by others. This License is a kind of "copyleft", which means that derivative works of the document must 2. VERBATIM COPYING themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software. You may copy and distribute the Document in any medium, either commercially or non- We have designed this License to use it for manuals for free software, because free software commercially, provided that this License, the copyright notices, and the license notice saying needs free documentation: a free program should come with manuals providing the same this License applies to the Document are reproduced in all copies, and that you add no other freedoms that the software does. But this License is not limited to software manuals; it can conditions whatsoever to those of this License. You may not use technical measures to obstruct be used for any textual work, regardless of subject matter or whether it is published as a or control the reading or further copying of the copies you make or distribute. However, you printed book. We recommend this License principally for works whose purpose is instruction may accept compensation in exchange for copies. If you distribute a large enough number of or reference. copies you must also follow the conditions in section 3. You may also lend copies, under the same conditions stated above, and you may publicly 1. APPLICABILITY AND DEFINITIONS display copies. This License applies to any manual or other work, in any medium, that contains a notice placed 3. COPYING IN QUANTITY by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under If you publish printed copies (or copies in media that commonly have printed covers) of the the conditions stated herein. The "Document", below, refers to any such manual or work. Any Document, numbering more than 100, and the Document''s license notice requires Cover Texts, member of the public is a licensee, and is addressed as "you". You accept the license if you you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: copy, modify or distribute the work in a way requiring permission under copyright law. Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers A "Modied Version" of the Document means any work containing the Document or a portion must also clearly and legibly identify you as the publisher of these copies. The front cover of it, either copied verbatim, or with modications and/or translated into another language. must present the full title with all words of the title equally prominent and visible. You may A "Secondary Section" is a named appendix or a front-matter section of the Document that add other material on the covers in addition. Copying with changes limited to the covers, as deals exclusively with the relationship of the publishers or authors of the Document to the long as they preserve the title of the Document and satisfy these conditions, can be treated Document''s overall subject (or to related matters) and contains nothing that could fall directly as verbatim copying in other respects. within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a If the required texts for either cover are too voluminous to t legibly, you should put the Secondary Section may not explain any mathematics.) The relationship could be a matter rst ones listed (as many as t reasonably) on the actual cover, and continue the rest onto of historical connection with the subject or with related matters, or of legal, commercial, adjacent pages. philosophical, ethical or political position regarding them. If you publish or distribute Opaque copies of the Document numbering more than 100, you The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being must either include a machine-readable Transparent copy along with each Opaque copy, those of Invariant Sections, in the notice that says that the Document is released under this or state in or with each Opaque copy a computer-network location from which the general License. If a section does not t the above denition of Secondary then it is not allowed to be network-using public has access to download using public-standard network protocols a designated as Invariant. The Document may contain zero Invariant Sections. If the Document complete Transparent copy of the Document, free of added material. If you use the latter does not identify any Invariant Sections then there are none. option, you must take reasonably prudent steps, when you begin distribution of Opaque copies The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or in quantity, to ensure that this Transparent copy will remain thus accessible at the stated Back-Cover Texts, in the notice that says that the Document is released under this License. A location until at least one year after the last time you distribute an Opaque copy (directly or Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words. through your agents or retailers) of that edition to the public. A "Transparent" copy of the Document means a machine-readable copy, represented in a It is requested, but not required, that you contact the authors of the Document well before format whose specication is available to the general public, that is suitable for revising redistributing any large number of copies, to give them a chance to provide you with an the document straightforwardly with generic text editors or (for images composed of pixels) updated version of the Document. generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent le format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modication by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not "Transparent" is called "Opaque". Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modication. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or 654 SLES 12 SP44. MODIFICATIONS The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modied Version. You may copy and distribute a Modied Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modied Version under precisely this 5. COMBINING DOCUMENTS License, with the Modied Version lling the role of the Document, thus licensing distribution and modication of the Modied Version to whoever possesses a copy of it. In addition, you You may combine the Document with other documents released under this License, under must do these things in the Modied Version: the terms dened in section 4 above for modied versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodied, and A. Use in the Title Page (and on the covers, if any) a title distinct from that of the list them all as Invariant Sections of your combined work in its license notice, and that you Document, and from those of previous versions (which should, if there were any, preserve all their Warranty Disclaimers. be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission. The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections B. List on the Title Page, as authors, one or more persons or entities responsible for with the same name but dierent contents, make the title of each such section unique by authorship of the modications in the Modied Version, together with at least ve adding at the end of it, in parentheses, the name of the original author or publisher of that of the principal authors of the Document (all of its principal authors, if it has fewer section if known, or else a unique number. Make the same adjustment to the section titles in than ve), unless they release you from this requirement. the list of Invariant Sections in the license notice of the combined work. C. State on the Title page the name of the publisher of the Modied Version, as the In the combination, you must combine any sections Entitled "History" in the various original publisher. documents, forming one section Entitled "History"; likewise combine any sections Entitled "Acknowledgements", and any sections Entitled "Dedications". You must delete all sections D. Preserve all the copyright notices of the Document. Entitled "Endorsements". E. Add an appropriate copyright notice for your modications adjacent to the other copyright notices. 6. COLLECTIONS OF DOCUMENTS F. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modied Version under the terms of this License, in the form You may make a collection consisting of the Document and other documents released under shown in the Addendum below. this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License G. Preserve in that license notice the full lists of Invariant Sections and required Cover for verbatim copying of each of the documents in all other respects. Texts given in the Document''s license notice. You may extract a single document from such a collection, and distribute it individually under H. Include an unaltered copy of this License. this License, provided you insert a copy of this License into the extracted document, and follow I. Preserve the section Entitled "History", Preserve its Title, and add to it an item this License in all other respects regarding verbatim copying of that document. stating at least the title, year, new authors, and publisher of the Modied Version as given on the Title Page. If there is no section Entitled "History" in the Document, 7. AGGREGATION WITH INDEPENDENT WORKS create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modied Version as stated in A compilation of the Document or its derivatives with other separate and independent the previous sentence. documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights J. Preserve the network location, if any, given in the Document for public access to of the compilation''s users beyond what the individual works permit. When the Document is a Transparent copy of the Document, and likewise the network locations given in included in an aggregate, this License does not apply to the other works in the aggregate the Document for previous versions it was based on. These may be placed in the which are not themselves derivative works of the Document. "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the If the Cover Text requirement of section 3 is applicable to these copies of the Document, then version it refers to gives permission. if the Document is less than one half of the entire aggregate, the Document''s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic K. For any section Entitled "Acknowledgements" or "Dedications", Preserve the Title equivalent of covers if the Document is in electronic form. Otherwise they must appear on of the section, and preserve in the section all the substance and tone of each of the printed covers that bracket the whole aggregate. contributor acknowledgements and/or dedications given therein. L. Preserve all the Invariant Sections of the Document, unaltered in their text and 8. TRANSLATION in their titles. Section numbers or the equivalent are not considered part of the section titles. Translation is considered a kind of modication, so you may distribute translations of the M. Delete any section Entitled "Endorsements". Such a section may not be included Document under the terms of section 4. Replacing Invariant Sections with translations requires in the Modied Version. special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You N. Do not retitle any existing section to be Entitled "Endorsements" or to conict in may include a translation of this License, and all the license notices in the Document, and title with any Invariant Section. any Warranty Disclaimers, provided that you also include the original English version of this O. Preserve any Warranty Disclaimers. License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the If the Modied Version includes new front-matter sections or appendices that qualify as original version will prevail. Secondary Sections and contain no material copied from the Document, you may at your If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the option designate some or all of these sections as invariant. To do this, add their titles to the requirement (section 4) to Preserve its Title (section 1) will typically require changing the list of Invariant Sections in the Modied Version''s license notice. These titles must be distinct actual title. from any other section titles. You may add a section Entitled "Endorsements", provided it contains nothing but endorsements of your Modied Version by various parties--for example, statements of peer 9. TERMINATION review or that the text has been approved by an organization as the authoritative denition You may not copy, modify, sublicense, or distribute the Document except as expressly of a standard. provided for under this License. Any other attempt to copy, modify, sublicense or distribute the You may add a passage of up to ve words as a Front-Cover Text, and a passage of up to 25 Document is void, and will automatically terminate your rights under this License. However, words as a Back-Cover Text, to the end of the list of Cover Texts in the Modied Version. Only parties who have received copies, or rights, from you under this License will not have their one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through licenses terminated so long as such parties remain in full compliance. arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one. 655 SLES 12 SP410. FUTURE REVISIONS OF THIS LICENSE The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may dier in detail to address new problems or concerns. See http:// www.gnu.org/copyleft/ . Each version of the License is given a distinguishing version number. If the Document species that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specied version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. ADDENDUM: How to use this License for your documents Copyright (c) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”. If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this: with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation. If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software. 656 SLES 12 SP4">