LDP/LDP/retired/PLD-Guide/admin-manual/sysconfig.xml

  <chapter>
    <title>System configuration</title>
    <section id="modules">
      <title>Device support (kernel modules config)</title>
      <para>
	PLD contains highly modularized kernel.
	All kernel-supported device drivers that can be compiled as a module
	are compiled in this way. 
      </para>
      <para>
	To support devices available in the system, proper modules must be 
	loaded into the kernel. That can be done primarily in four ways:
	<orderedlist>
	  <listitem>
	    <para>
	      They can be loaded by hand with <command>modprobe</command> or
	      <command>insmod</command> command (the least convenient method)
	    </para>
	  </listitem>
	  <listitem>
	    <para>
	      They can be loaded at boot-up by some extra script
	      (e.g. /etc/rc.d/init/rc.local).
	    </para>
	  </listitem>
	  <listitem>
	    <para>
	      Some devices (mainly disk interfaces) 
	      need support at a very, very early stage of system boot-up.
	      Modules for these devices must be loaded from 
	      so-called <emphasis>initrd</emphasis>
	      (see more in <xref linkend="bootloaders"/>)
	    </para>
	  </listitem>
	  <listitem>
	    <para>
	      Finally, they can be loaded automatically, when they are
	      needed, by <command>kmod</command> daemon.
	    </para>
	  </listitem>
	</orderedlist>
	
	The latter method is most convenient, although not every device can be 
	supported like that.
      </para>
      <para>
	Kmod needs information what module should be associated to particular
	devices. 
      </para>
      <note>
	<para>
	  During installation process the installer takes care about 
	  setting proper <emphasis>initrd</emphasis>, and may also
	  put some entries into <filename>/etc/modules.conf</filename>.
	  (e.g. aliases for network devices), but in general this
	  file should be filled in by the administrator.
	</para>
      </note>
      <para>
	Some typical settings in <filename>/etc/modules.conf</filename>:
      </para>
      <programlisting>
# Use kernel module 3c509 (3Com 509/509b adapter) as a driver for
# first ethernet device (eth0):

alias eth0 3c509

# Use kernel module aic7xxx to handle SCSI hostadapter:

scsi_hostadapter aic7xxx
      </programlisting>
      <para>	  
	See 
	<citerefentry>
	  <refentrytitle>modules.conf</refentrytitle>
	  <manvolnum>5</manvolnum>
	</citerefentry>
	for details.
      </para>
    </section>
    <section id="disks">
      <title>Disks</title>
      <para>
      </para>
      <literallayout>
	fstab:
	disks 
	removable media: CD, diskettes etc
	user access
	automounter
	LVM?
	journaling?
	raid?
      </literallayout>
    </section>
    <section id="inittab">
      <title>Init control: /etc/inittab</title>
      <para>
	The file <filename>/etc/inittab</filename> is read by 
	<command>init</command> process to control
	system behavior in particular runlevel. Full description
	of this file can be found in 
	<citerefentry>
	  <refentrytitle>inittab</refentrytitle>
	  <manvolnum>5</manvolnum>
	</citerefentry>
      </para>
      <para>
      What this file usually contains:
	<itemizedlist>
	  <listitem>
	    <para>
	      <emphasis>Default runlevel</emphasis> - the runlevel used
	      when init is invoked without parameters (e.g. during system startup).
	      Runlevels are described in <xref linkend="runlevels"/>.
	      Default runlevel is given in the form:
	      <programlisting>id:3:initdefault:</programlisting>
	      Here the digit 3 indicates use of runlevel 3. This can be changed
	      to any other valid runlevel.
	    </para>
	  </listitem>
	  <listitem>
	    <para>
	      Instructions to run getty on consoles. They look like that:
	      <programlisting>1:12345:respawn:/sbin/mingetty --noclear tty1</programlisting>
	      One of possible situations when this needs to be changed is
	      when we want console on serial port (see e.g. <xref linkend="installer-serial"/>).
	    </para>
	  </listitem>
	  <listitem>
	    <para>
	      Invocation of proper init scripts. These are lines like this:
	      <programlisting>
si::sysinit:/etc/rc.d/rc.sysinit
l0:0:wait:/etc/rc.d/rc 0
</programlisting>
	      This rarely needs to be changed.
	    </para>
	  </listitem>
	  <listitem>
	    <para>
	      Handling special events like Ctrl-Alt-Del keystroke.
	      The line looks like this:
	      <programlisting>
ca::ctrlaltdel:/sbin/shutdown -t3 -r now
	      </programlisting>
	      The command run at Ctrl-Alt-Del event can be replaced here,
	      e.g. one can change <command>shutdown -r</command> 
	      to <command>shutdown -h</command> to get the halt instead reboot.
	    </para>
	  </listitem>
	</itemizedlist>
      </para>
    </section>
    <section id="etc-sysconfig">
      <title>Basic system configuration: <filename>/etc/sysconfig</filename></title>
      <section>
	<title>Intro</title>
	<para>
	  Directory <filename>/etc/sysconfig</filename> contains several files
	  that are used by rc-scripts (system startup scripts located in 
	  /etc/rc.d). Those files defines basic properties of the system.
	</para>
      </section>
      <section>
	<title>console</title>
	<para>
	  File <filename>/etc/sysconfig/console</filename>
	  contains basic console settings.
	</para>
	<para>
	  After modifying config file, issue 
	  <programlisting>/etc/rc.d/init.d/console restart</programlisting>
	  if you want the changes to take effect.
	</para>
      </section>
      <section>
	<title>mouse</title>
	<para>
	  File <filename>/etc/sysconfig/mouse</filename> contains
	  mouse settings for service <command>gpm</command> (General Purpose Mouse).
	  This service provides mouse support for console based
	  applications and may be also used by X Window System.
	  <!--  (see <xref linkend="x-repeater"/>) -->
	</para>
	<para>
	  After modifying config file, issue 
	  <programlisting>/etc/rc.d/init.d/gpm restart</programlisting>
	  if you want the changes to take effect.
	</para>
      </section>

      <section>
	<title>clock</title>
	<para>
	  File <filename>/etc/sysconfig/clock</filename> contains
	  clock settings.
	  Its content is used by /etc/rc.d/rc.sysinit script
	  at very early stage of system bootup.
	  This file contains very general clock properties.
	  Setting clock can be done with <command>date</command>
	  and <command>hwclock</command> commands.
	</para>
      </section>
      <section>
	<title>system</title>
	<para>
	  Its content is used by rc-scripts at very early stage of system bootup.
	  It contains some basic settings, e.g. system behavior in case of kernel
	  panic, etc.
	</para>
      </section>
    </section>

    <section id="printing">
      <title>Printing</title>
      <para>
      </para>
    </section>
    <section id="x-window">
      <title>X Window</title>
      <para>
      </para>
    </section>
  </chapter>


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