16.3 System Configuration via /etc/sysconfig
The main configuration of SUSE Linux Enterprise is controlled by the configuration
files in /etc/sysconfig. The individual files in
/etc/sysconfig are only read by the scripts to which
they are relevant. This ensures that network settings, for example,
only need to
be parsed by network-related scripts. Many other system configuration
files are generated according to the settings in
/etc/sysconfig. This task is performed by SuSEconfig.
For example, if you change the network configuration, SuSEconfig
might make changes to the file /etc/host.conf
because this is one of the files relevant for the network configuration.
This concept allows most configurations to be made in one
central place without fiddling with different configuration files
at different places of the operating system.
There are two ways to edit the system configuration. Either use the
YaST sysconfig Editor or edit the configuration files manually.
16.3.1 Changing the System Configuration Using the YaST sysconfig
The YaST sysconfig editor provides an easy-to-use front-end to system
configuration. Without any knowledge of the actual location of the
configuration variable you need to change, you can just use the built-in
search function of this module, change the value of the configuration
variable as needed, and let YaST take care of applying these changes,
updating configurations that depend on the values set in
sysconfig and restarting services.
WARNING: Modifying /etc/sysconfig/* Files Can
Damage Your Installation
Do not modify the /etc/sysconfig
files if you lack previous experience and knowledge. It could do
considerable damage to your system. The files in
/etc/sysconfig include a short
comment for each variable to explain what effect they actually have.
Figure 16-2 System Configuration Using the sysconfig Editor
The YaST sysconfig dialog is split into three parts. The left part of the
dialog shows a tree view of all configurable variables. When you select a
variable, the right part displays both the current selection and the
current setting of this variable. Below, a third window displays a short
description of the variable's purpose, possible values, the default value,
and the actual configuration file from which this variable originates. The
dialog also provides information about which configuration script is
executed after changing the variable and which new service is started as a
result of the change. YaST prompts you to confirm your changes and
informs you which scripts will be executed after you leave the dialog by
selecting . Also select the services and scripts
to skip for now, so they are started later. YaST applies all changes
automatically and restarts any services involved for your changes to take
16.3.2 Changing the System Configuration Manually
To manually change the system configuration, proceed as follows
Bring the system into single user mode (runlevel 1) with
Change the configuration files as needed with an editor of your choice.
If you do not use YaST to change the configuration files in
/etc/sysconfig, make sure
that empty variable values are represented by two quotation marks
(KEYTABLE="") and that
values with blanks in them are enclosed in quotation marks. Values
consisting of one word only do not need to be quoted.
Execute SuSEconfig to make sure that the changes take
Bring your system back to the previous runlevel with a command like
default_runlevel with the default runlevel of
the system. Choose 5 if you want to return to
full multiuser with network and X or choose 3 if you
prefer to work in full multiuser with network.
This procedure is mainly relevant when changing systemwide settings, such
as the network configuration. Small changes should not require going into
single user mode, but you may still do so to make absolutely sure that
all the programs concerned are correctly restarted.
HINT: Configuring Automated System Configuration
To disable the automated system configuration by SuSEconfig,
set the variable ENABLE_SUSECONFIG in
/etc/sysconfig/suseconfig to no. Do
not disable SuSEconfig if you want to use the SUSE installation
support. It is also possible to disable the autoconfiguration partially.