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documentation.suse.com / SUSE Linux Enterprise Server Documentation / Administration Guide / System / Special system features
Applies to SUSE Linux Enterprise Server 15 SP5

30 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-specific settings (I18N and L10N).

30.1 Information about special software packages

The following chapter provides basic information about the following tools: bash, cron, logrotate, locate, ulimit and free.

30.1.1 The bash package and /etc/profile

Bash is the default system shell. When used as a login shell, it reads several initialization files. 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 files, 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
> cp /etc/skel/.bashrc ~/.bashrc
> mv ~/.profile ~/.profile.old
> cp /etc/skel/.profile ~/.profile

Then copy personal adjustments back from the *.old files.

30.1.2 The cron package

Use cron to automatically run commands in the background at predefined 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 30.1, “Entry in /etc/crontab”, root is entered. Package-specific tables, located in /etc/cron.d, have the same format. See the cron man page (man cron).

Example 30.1: 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 file must be loaded directly into an editor, then modified and saved.

Several 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 files regularly using /etc/crontab entries (see Example 30.2, “/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 30.2: /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
44 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 specified DAILY_TIME for a longer time. The maximum value of MAX_NOT_RUN is 14 days.

30.1.3 Stopping cron status messages

To avoid the mail flood 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.

30.1.4 Log files: package logrotate

There are several system services (daemons) that, along with the kernel itself, regularly record the system status and specific events onto log files. 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 files are normally stored in /var/log as specified by FHS and grow on a daily basis. The logrotate package helps control the growth of these files. For more details refer to Section 3.3, “Managing log files with logrotate.

30.1.5 The locate command

locate, a command for quickly finding files, 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.

30.1.6 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 30.1, “ulimit: Setting resources for the user”.

Table 30.1: ulimit: Setting resources for the user


The maximum resident set size


The maximum amount of virtual memory available to the shell


The maximum size of the stack


The maximum size of core files created


All current limits are reported

Systemwide default entries are set in /etc/profile. Editing this file directly is not recommended, because changes will be overwritten during system upgrades. To customize systemwide profile settings, use /etc/profile.local. Per-user settings should be made in ~USER/.profile.

Example 30.3: 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 specified in KB. For more detailed information, see man bash.

Important: ulimit support

Not all shells support ulimit directives. PAM (for example, pam_limits) offers comprehensive adjustment possibilities as an alternative to ulimit.

30.1.7 The free command

The free command displays the total amount of free and used physical memory and swap space in the system and the buffers and cache consumed by the kernel. The concept of available RAM dates back to before the days of unified memory management. The slogan free memory is bad memory applies well to Linux. As a result, Linux has always made the effort to balance out caches without 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 files, 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 differences between the counters in /proc/meminfo. Most, but not all, of them can be accessed via /proc/slabinfo.

However, if your goal is to find out how much RAM is currently being used, find this information in /proc/meminfo.

30.1.8 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.

30.1.9 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 different 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 first man page will be displayed.

To change this to the default system behavior, set MAN_POSIXLY_CORRECT=1 in a shell initialization file such as ~/.bashrc.

30.1.10 Settings for GNU Emacs

GNU Emacs is a complex work environment. The following sections cover the configuration files processed when GNU Emacs is started. More information is available at https://www.gnu.org/software/emacs/.

On start-up, Emacs reads several files containing the settings of the user, system administrator and distributor for customization or preconfiguration. The initialization file ~/.emacs is installed to the home directories of the individual users from /etc/skel. .emacs, in turn, reads the file /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 defines the file ~/.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 file site-start.el in the directory /usr/share/emacs/site-lisp. The file site-start.el is loaded before the initialization file ~/.emacs. Among other things, site-start.el ensures that special configuration files distributed with Emacs add-on packages, such as psgml, are loaded automatically. Configuration files 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 files is available in the Emacs info file under Init File: info:/emacs/InitFile. Information about how to disable the loading of these files (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.

  • emacs-el: the uncompiled library files 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.

30.2 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 AltF1 through AltF6. 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 CtrlAltF1 to CtrlAltF6. To return to X, press AltF7.

30.3 Keyboard mapping

To standardize the keyboard mapping of programs, changes were made to the following files:


These changes only affect applications that use terminfo entries or whose configuration files 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).

Tip: More information

Information about XKB is available in the documents listed in /usr/share/doc/packages/xkeyboard-config (part of the xkeyboard-config package).

30.4 Language and country-specific settings

The system is, to a very large extent, internationalized and can be modified for local needs. Internationalization (I18N) allows specific localization (L10N). The abbreviations I18N and L10N are derived from the first and last letters of the words and, in between, the number of letters omitted.

Settings are made with LC_ variables defined in the file /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 defined directly with its own variable or indirectly with a master variable in the file language (see the locale man page).

List of variables

These variables are passed to the shell without the RC_ prefix and represent the listed categories. The shell profiles concerned are listed below. The current setting can be shown with the command locale.


This variable, if set, overwrites the values of the variables already mentioned.


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.


This variable can be set to yes or ctype (default). If set to yes, root uses language and country-specific settings, otherwise the system administrator always works in a POSIX environment.

The variables can be set with the YaST sysconfig editor. The value of such a variable contains the language code, country code, encoding and modifier. The individual components are joined by special characters:


30.4.1 System-wide locale settings

systemd reads /etc/locale.conf at early boot. The locale settings configured in this file are inherited by every service or user, unless there are individual settings.

Note: Behavior of older configuration files under SUSE Linux Enterprise Server SUSE Linux Enterprise Server

Earlier versions of SUSE Linux Enterprise Server read locale settings from /etc/sysconfig/language, /etc/sysconfig/keyboard, and /etc/sysconfig/console. Starting with SUSE Linux Enterprise Server 15 GA, these files are considered obsolete. systemd does not read settings from these files anymore. Instead, systemd reads /etc/locale.conf.

However, variables defined in /etc/sysconfig/language will still be used: They override the system-wide locale and can be used to define different locale settings for user shells (see Section 30.4.2, “Some examples”).

To set the system-wide locale, you can either:

  • Write your settings in /etc/locale.conf. Each line is a environment-like variable assignment (see man 5 locale.conf for a list of variables):


    To fine-tune the settings, you can add additional variables, one variable per line.

  • Use the command localectl:

    # localectl set-locale LANG=de_DE.UTF-8

    Same here, you can also specify additional variables after the localectl set-locale command.

To keep backward compatibility with old systems during the update of the systemd package, all variables mentioned will be migrated from sysconfig to their final destinations if they are not already defined there.

30.4.2 Some examples

You should always set the language and country codes together. Language settings follow the standard ISO 639 available at https://www.evertype.com/standards/iso639/iso639-en.html and https://www.loc.gov/standards/iso639-2/. Country codes are listed in ISO 3166, see https://en.wikipedia.org/wiki/ISO_3166.

It only makes sense to set values for which usable description files can be found in /usr/lib/locale. Additional description files can be created from the files in /usr/share/i18n using the command localedef. The description files are part of the glibc-i18ndata package. A description file 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

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.


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 defining the charset (ISO-8859-1 in this case) is then evaluated by programs like Emacs.


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.

This 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.

30.4.3 Locale settings in ~/.i18n

If you are not satisfied 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_ namespace prefixes. For example, use LANG instead of RC_LANG:


30.4.4 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 file 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 defined, for example, for Breton to French or for Galician to Spanish to Portuguese:



If desired, use the Norwegian variants Nynorsk and Bokmål instead (with additional fallback to no):






In Norwegian, LC_TIME is also treated differently.

One 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 definition file 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 definition visible to the system.

30.4.5 More information

  • The GNU C Library Reference Manual, Chapter Locales and Internationalization. It is included in the package glibc-info.

  • Markus Kuhn, UTF-8 and Unicode FAQ for Unix/Linux, currently at https://www.cl.cam.ac.uk/~mgk25/unicode.html.