source: chapter09/usage.xml@ ee950a5e

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<sect1 id="ch-config-usage" revision="sysv">
  <?dbhtml filename="usage.html"?>

  <title>System V Bootscript Usage and Configuration</title>

  <indexterm zone="ch-config-usage">
    <primary sortas="a-Bootscripts">Bootscripts</primary>
    <secondary>usage</secondary>
  </indexterm>

  <sect2>
    <title>How Do the System V Bootscripts Work?</title>

    <para>This version of LFS uses a special booting facility named SysVinit, based on a
    series of <emphasis>run levels</emphasis>. The boot procedure can be quite different from one
    system to another; the fact that things worked one way in a particular Linux
    distribution does not guarantee they will work the same way in LFS. LFS has its
    own way of doing things, but it does respect generally accepted standards.</para>
  
    <para>There is an alternative boot procedure called <command>systemd</command>. We will
    not discuss that boot process any further here. For a detailed description visit
    <ulink url="https://www.linux.com/training-tutorials/understanding-and-using-systemd/"/>.</para>

    <para>SysVinit (which will be referred to as <quote>init</quote> from now on)
    uses a run levels scheme. There are seven run levels, numbered 0 to 6.
    (Actually, there are more run levels, but the others are for special cases and are
    generally not used. See <ulink role='man'
    url='&man;init.8'>init(8)</ulink> for more details.)
    Each one of the seven corresponds to actions the computer is supposed to
    perform when it starts up or shuts down. The default run level is 3. Here are the
    descriptions of the different run levels as they are implemented in LFS:</para>

<literallayout>0: halt the computer
1: single-user mode
2: reserved for customization, otherwise the same as 3
3: multi-user mode with networking
4: reserved for customization, otherwise the same as 3
5: same as 4, it is usually used for GUI login (like GNOME's <command>gdm</command> or LXDE's <command>lxdm</command>)
6: reboot the computer</literallayout>

    <note>
       <para>
         Classically, run level 2 above was defined as <quote>multi-user
         mode without networking,</quote> but this was only the case
         many years ago when multiple users could connect to a system via
         serial ports.  In today's environment it makes no sense, and
         we now say it is <quote>reserved.</quote>
       </para>
    </note>

  </sect2>

  <sect2 id="conf-sysvinit" role="configuration">
  <title>Configuring Sysvinit</title>

  <indexterm zone="conf-sysvinit">
    <primary sortas="a-Sysvinit">Sysvinit</primary>
    <secondary>configuring</secondary>
  </indexterm>

  <indexterm zone="conf-sysvinit">
    <primary sortas="e-/etc/inittab">/etc/inittab</primary>
  </indexterm>

  <para>During kernel initialization, the first program that is run
  (if not overridden on the command line) is
  <command>init</command>.  This program reads the initialization file
  <filename>/etc/inittab</filename>.  Create this file with:</para>

<screen><userinput>cat &gt; /etc/inittab &lt;&lt; "EOF"
<literal># Begin /etc/inittab

id:3:initdefault:

si::sysinit:/etc/rc.d/init.d/rc S

l0:0:wait:/etc/rc.d/init.d/rc 0
l1:S1:wait:/etc/rc.d/init.d/rc 1
l2:2:wait:/etc/rc.d/init.d/rc 2
l3:3:wait:/etc/rc.d/init.d/rc 3
l4:4:wait:/etc/rc.d/init.d/rc 4
l5:5:wait:/etc/rc.d/init.d/rc 5
l6:6:wait:/etc/rc.d/init.d/rc 6

ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now

su:S06:once:/sbin/sulogin
s1:1:respawn:/sbin/sulogin

1:2345:respawn:/sbin/agetty --noclear tty1 9600
2:2345:respawn:/sbin/agetty tty2 9600
3:2345:respawn:/sbin/agetty tty3 9600
4:2345:respawn:/sbin/agetty tty4 9600
5:2345:respawn:/sbin/agetty tty5 9600
6:2345:respawn:/sbin/agetty tty6 9600

# End /etc/inittab</literal>
EOF</userinput></screen>

  <para>An explanation of this initialization file is in the man page for
  <emphasis>inittab</emphasis>.  In LFS, the key command is
  <command>rc</command>. The initialization file above instructs
  <command>rc</command> to run all the scripts starting with an S in the
  <filename class="directory">/etc/rc.d/rcS.d</filename> directory
  followed by all the scripts starting with an S in the <filename
  class="directory">/etc/rc.d/rc?.d</filename> directory where the question
  mark is specified by the initdefault value.</para>

  <para>As a convenience, the <command>rc</command> script reads a library of
  functions in <filename class="directory">/lib/lsb/init-functions</filename>.
  This library also reads an optional configuration file,
  <filename>/etc/sysconfig/rc.site</filename>.  Any of the system
  configuration parameters described in subsequent sections can be
  placed in this file, allowing consolidation of all system
  parameters in this one file.</para>

  <para>As a debugging convenience, the functions script also logs all output
  to <filename>/run/var/bootlog</filename>.  Since the <filename
  class="directory">/run</filename> directory is a tmpfs, this file is not
  persistent across boots; however, it is appended to the more permanent file
  <filename>/var/log/boot.log</filename> at the end of the boot process.</para>

  <sect3 id="init-levels" >
  <title>Changing Run Levels</title>

  <para>Changing run levels is done with <command>init
  <replaceable>&lt;runlevel&gt;</replaceable></command>, where
  <replaceable>&lt;runlevel&gt;</replaceable> is the target run level. For example, to
  reboot the computer, a user could issue the <command>init 6</command> command,
  which is an alias for the <command>reboot</command> command. Likewise,
  <command>init 0</command> is an alias for the <command>halt</command>
  command.</para>

  <para>There are a number of directories under <filename
  class="directory">/etc/rc.d</filename> that look like <filename
  class="directory">rc?.d</filename> (where ? is the number of the run level) and
  <filename class="directory">rcS.d</filename>, all containing a number of
  symbolic links. Some links begin with a <emphasis>K</emphasis>; the others begin with
  an <emphasis>S</emphasis>, and all of them have two numbers following the
  initial letter. The K means to stop (kill) a service and the S means to start a
  service. The numbers determine the order in which the scripts are run, from 00
  to 99&mdash;the smaller the number, the sooner the script runs. When
  <command>init</command> switches to another run level, the appropriate services
  are either started or stopped, depending on the run level chosen.</para>

  <para>The real scripts are in <filename
  class="directory">/etc/rc.d/init.d</filename>. They do the actual work, and
  the symlinks all point to them. K links and S links point to
  the same script in <filename class="directory">/etc/rc.d/init.d</filename>.
  This is because the scripts can be called with different parameters like
  <parameter>start</parameter>, <parameter>stop</parameter>,
  <parameter>restart</parameter>, <parameter>reload</parameter>, and
  <parameter>status</parameter>. When a K link is encountered, the appropriate
  script is run with the <parameter>stop</parameter> argument. When an S link
  is encountered, the appropriate script is run with the
  <parameter>start</parameter> argument.</para>
<!-- Changed for March 24th, 2022 version of bootscripts
  <para>There is one exception to this explanation. Links that start
  with an <emphasis>S</emphasis> in the <filename
  class="directory">rc0.d</filename> and <filename
  class="directory">rc6.d</filename> directories will not cause anything
  to be started. They will be called with the parameter
  <parameter>stop</parameter> to stop something. The logic behind this
  is that when a user is going to reboot or halt the system, nothing
  needs to be started, but the order of shutdown needs to be controlled.
  For these run levels, all <emphasis>K</emphasis> prefixed scripts will be
  run before any <emphasis>S</emphasis> prefixed scripts are run with the
  <parameter>stop</parameter> parameter.
  </para>
-->
  <para>These are descriptions of what the arguments make the scripts
  do:</para>

  <variablelist>

    <varlistentry>
      <term><parameter>start</parameter></term>
      <listitem>
        <para>The service is started.</para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><parameter>stop</parameter></term>
      <listitem>
        <para>The service is stopped.</para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><parameter>restart</parameter></term>
      <listitem>
        <para>The service is stopped and then started again.</para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><parameter>reload</parameter></term>
      <listitem>
        <para>The configuration of the service is updated.
        This is used after the configuration file of a service was modified, when
        the service does not need to be restarted.</para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><parameter>status</parameter></term>
      <listitem>
        <para>Tells if the service is running and with which PIDs.</para>
      </listitem>
    </varlistentry>

  </variablelist>

  <para>Feel free to modify the way the boot process works (after all,
  it is your own LFS system). The files given here are an example of how
  it can be done.</para>

  </sect3>
  </sect2>

  <sect2>
    <title>Udev Bootscripts</title>

      <para>The <filename>/etc/rc.d/init.d/udev</filename> initscript starts
      <command>udevd</command>, triggers any "coldplug" devices that have
      already been created by the kernel, and waits for any rules to complete.
      The script also unsets the uevent handler from the default of
      <filename>/sbin/hotplug </filename>.  This is done because the kernel no
      longer needs to call an external binary.  Instead,
      <command>udevd</command> will listen on a netlink socket for uevents that
      the kernel raises.</para>

      <para>The <command>/etc/rc.d/init.d/udev_retry</command> script takes
      care of re-triggering events for subsystems whose rules may rely on
      file systems that are not mounted until the <command>mountfs</command>
      script is run (in particular, <filename class="directory">/usr</filename>
      and <filename class="directory">/var</filename> may cause this).  This
      script runs after the <command>mountfs</command> script, so those rules
      (if re-triggered) should succeed the second time around.  It is
      configured by the <filename>/etc/sysconfig/udev_retry</filename> file;
      any words in this file other than comments are considered subsystem names
      to trigger at retry time.  To find the subsystem of a device, use
      <command>udevadm info --attribute-walk &lt;device&gt;</command> where
      &lt;device&gt; is an absolute path in /dev or /sys, such as /dev/sr0, or
      /sys/class/rtc.</para>

      <para>For information on kernel module loading and udev, see
      <xref linkend="module-loading"/>.</para>
  </sect2>

  <sect2 id="ch-config-clock">
    <title>Configuring the System Clock</title>

    <indexterm zone="ch-config-clock">
      <primary sortas="d-setclock">setclock</primary>
    <secondary>configuring</secondary></indexterm>

    <para>The <command>setclock</command> script reads the time from the hardware
    clock, also known as the BIOS or Complementary Metal Oxide Semiconductor
    (CMOS) clock. If the hardware clock is set to UTC, this script will convert the
    hardware clock's time to the local time using the
    <filename>/etc/localtime</filename> file (which tells the
    <command>hwclock</command> program which time zone to use). There is no
    way to detect whether or not the hardware clock is set to UTC, so this
    must be configured manually.</para>

    <para>The <command>setclock</command> program is run via
    <application>udev</application> when the kernel detects the hardware
    capability upon boot.  It can also be run manually with the stop parameter to
    store the system time to the CMOS clock.</para>

    <para>If you cannot remember whether or not the hardware clock is set to UTC,
    find out by running the <userinput>hwclock --localtime --show</userinput>
    command. This will display what the current time is according to the hardware
    clock. If this time matches whatever your watch says, then the hardware clock is
    set to local time. If the output from <command>hwclock</command> is not local
    time, chances are it is set to UTC time. Verify this by adding or subtracting
    the proper number of hours for your time zone to the time shown by
    <command>hwclock</command>. For example, if you are currently in the MST
    time zone, which is also known as GMT -0700, add seven hours to the local
    time.</para>

    <para>Change the value of the <envar>UTC</envar> variable below
    to a value of <parameter>0</parameter> (zero) if the hardware clock
    is <emphasis>NOT</emphasis> set to UTC time.</para>

    <para>Create a new file <filename>/etc/sysconfig/clock</filename> by running
    the following:</para>

<screen><userinput>cat &gt; /etc/sysconfig/clock &lt;&lt; "EOF"
<literal># Begin /etc/sysconfig/clock

UTC=1

# Set this to any options you might need to give to hwclock,
# such as machine hardware clock type for Alphas.
CLOCKPARAMS=

# End /etc/sysconfig/clock</literal>
EOF</userinput></screen>

    <para>A good hint explaining how to deal with time on LFS is available
    at <ulink url="&hints-root;time.txt"/>. It explains issues such as
    time zones, UTC, and the <envar>TZ</envar> environment variable.</para>

    <note><para>The CLOCKPARAMS and UTC parameters may also be set
    in the <filename>/etc/sysconfig/rc.site</filename> file.</para></note>

  </sect2>

  <sect2 id="ch-config-console">
  <?dbhtml filename="console.html"?>

  <title>Configuring the Linux Console</title>

  <indexterm zone="ch-config-console">
    <primary sortas="d-console">console</primary>
    <secondary>configuring</secondary>
  </indexterm>

  <para>This section discusses how to configure the <command>console</command>
  bootscript that sets up the keyboard map, console font, and console kernel log
  level. If non-ASCII characters (e.g., the copyright sign, the British pound
  sign, and the Euro symbol) will not be used and the keyboard is a U.S. one, much
  of this section can be skipped. Without the configuration file, (or
  equivalent settings in <filename>rc.site</filename>), the
  <command>console</command> bootscript will do nothing.</para>

  <para>The <command>console</command> script reads the
  <filename>/etc/sysconfig/console</filename> file for configuration
  information.  Decide which keymap and screen font will be used. Various
  language-specific HOWTOs can also help with this; see <ulink
  url="https://tldp.org/HOWTO/HOWTO-INDEX/other-lang.html"/>. If still in
  doubt, look in the <filename class="directory">/usr/share/keymaps</filename>
  and <filename class="directory">/usr/share/consolefonts</filename> directories
  for valid keymaps and screen fonts. Read the <ulink role='man'
  url='&man;loadkeys.1'>loadkeys(1)</ulink> and <ulink role='man'
  url='&man;setfont.8'>setfont(8)</ulink> manual pages to determine the
  correct arguments for these programs.</para>

  <para>The <filename>/etc/sysconfig/console</filename> file should contain lines
  of the form: <envar>VARIABLE=value</envar>. The following variables are recognized:</para>
  <variablelist>

    <varlistentry>
      <term>LOGLEVEL</term>
      <listitem>
        <para>This variable specifies the log level for kernel messages sent
        to the console as set by <command>dmesg -n</command>. Valid levels are
        from <literal>1</literal> (no messages) to <literal>8</literal>. The default level is <literal>7</literal>, which is quite verbose.</para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term>KEYMAP</term>
      <listitem>
        <para>This variable specifies the arguments for the
        <command>loadkeys</command> program, typically, the name of the keymap
        to load, e.g., <literal>it</literal>. If this variable is not set, the
        bootscript will not run the <command>loadkeys</command> program,
        and the default kernel keymap will be used.  Note that a few keymaps
        have multiple versions with the same name (cz and its variants in
        qwerty/ and qwertz/, es in olpc/ and qwerty/, and trf in fgGIod/ and
        qwerty/). In these cases the parent directory should also be specified
        (e.g. qwerty/es) to ensure the proper keymap is loaded.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term>KEYMAP_CORRECTIONS</term>
      <listitem>
        <para>This (rarely used) variable
        specifies the arguments for the second call to the
        <command>loadkeys</command> program. This is useful if the stock keymap
        is not completely satisfactory and a small adjustment has to be made. E.g.,
        to include the Euro sign into a keymap that normally doesn't have it,
        set this variable to <literal>euro2</literal>.</para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term>FONT</term>
      <listitem>
        <para>This variable specifies the arguments for the
        <command>setfont</command> program. Typically, this includes the font
        name, <literal>-m</literal>, and the name of the application character
        map to load. E.g., in order to load the <quote>lat1-16</quote> font
        together with the <quote>8859-1</quote> application character map
        (appropriate in the USA),
        <!-- because of the copyright sign -->
        set this variable to <literal>lat1-16 -m 8859-1</literal>.
        In UTF-8 mode, the kernel uses the application character map to
        convert 8-bit key codes to UTF-8. Therefore
        the argument of the "-m" parameter should be set to the encoding of the
        composed key codes in the keymap.</para>

      </listitem>
    </varlistentry>

    <varlistentry>
      <term>UNICODE</term>
      <listitem>
        <para>Set this variable to <literal>1</literal>, <literal>yes</literal>, or
        <literal>true</literal> in order to put the
        console into UTF-8 mode. This is useful in UTF-8 based locales and
        harmful otherwise.</para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term>LEGACY_CHARSET</term>
      <listitem>
        <para>For many keyboard layouts, there is no stock Unicode keymap in
        the Kbd package. The <command>console</command> bootscript will
        convert an available keymap to UTF-8 on the fly if this variable is
        set to the encoding of the available non-UTF-8 keymap.</para>
      </listitem>
    </varlistentry>

  </variablelist>

  <para>Some examples:</para>

  <itemizedlist>

    <listitem>
      <para>For a non-Unicode setup, only the KEYMAP and FONT variables are
      generally needed. E.g., for a Polish setup, one would use:</para>
<screen role="nodump"><userinput>cat &gt; /etc/sysconfig/console &lt;&lt; "EOF"
<literal># Begin /etc/sysconfig/console

KEYMAP="pl2"
FONT="lat2a-16 -m 8859-2"

# End /etc/sysconfig/console</literal>
EOF</userinput></screen>
    </listitem>

    <listitem>
      <para>As mentioned above, it is sometimes necessary to adjust a
      stock keymap slightly. The following example adds the Euro symbol to the
      German keymap:</para>

<screen role="nodump"><userinput>cat &gt; /etc/sysconfig/console &lt;&lt; "EOF"
<literal># Begin /etc/sysconfig/console

KEYMAP="de-latin1"
KEYMAP_CORRECTIONS="euro2"
FONT="lat0-16 -m 8859-15"
UNICODE="1"

# End /etc/sysconfig/console</literal>
EOF</userinput></screen>
    </listitem>

    <listitem>
      <para>The following is a Unicode-enabled example for Bulgarian, where a
      stock UTF-8 keymap exists:</para>
<!-- This is what is used by jhalfs for creating the console file: whenever
     you change the following, please inform the jhalfs maintainer(s). -->
<screen><userinput>cat &gt; /etc/sysconfig/console &lt;&lt; "EOF"
<literal># Begin /etc/sysconfig/console

UNICODE="1"
KEYMAP="bg_bds-utf8"
FONT="LatArCyrHeb-16"

# End /etc/sysconfig/console</literal>
EOF</userinput></screen>
    </listitem>

    <listitem>
      <para>Due to the use of a 512-glyph LatArCyrHeb-16 font in the previous
      example, bright colors are no longer available on the Linux console unless
      a framebuffer is used. If one wants to have bright colors without a
      framebuffer and can live without characters not belonging to his language,
      it is still possible to use a language-specific 256-glyph font, as
      illustrated below:</para>

<screen role="nodump"><userinput>cat &gt; /etc/sysconfig/console &lt;&lt; "EOF"
<literal># Begin /etc/sysconfig/console

UNICODE="1"
KEYMAP="bg_bds-utf8"
FONT="cyr-sun16"

# End /etc/sysconfig/console</literal>
EOF</userinput></screen>
    </listitem>

    <listitem>
      <para>The following example illustrates keymap autoconversion from
      ISO-8859-15 to UTF-8 and enabling dead keys in Unicode mode:</para>

<screen role="nodump"><userinput>cat &gt; /etc/sysconfig/console &lt;&lt; "EOF"
<literal># Begin /etc/sysconfig/console

UNICODE="1"
KEYMAP="de-latin1"
KEYMAP_CORRECTIONS="euro2"
LEGACY_CHARSET="iso-8859-15"
FONT="LatArCyrHeb-16 -m 8859-15"

# End /etc/sysconfig/console</literal>
EOF</userinput></screen>
    </listitem>

    <listitem>
      <para>Some keymaps have dead keys (i.e., keys that don't produce a
      character by themselves, but put an accent on the character produced
      by the next key) or define composition rules (such as: <quote>press
      Ctrl+. A E to get &AElig;</quote> in the default keymap).
      Linux-&linux-version; interprets dead keys and composition rules in the
      keymap correctly only when the source characters to be composed together
      are not multibyte. This deficiency doesn't affect keymaps for European
      languages, because there accents are added to unaccented ASCII
      characters, or two ASCII characters are composed together. However, in
      UTF-8 mode it is a problem; e.g., for the Greek language, where one
      sometimes needs to put an accent on the letter α.
      The solution is either to avoid the use of UTF-8, or to install the
      X window system, which doesn't have this limitation, in its input
      handling.</para>
    </listitem>

    <listitem>
      <para>For Chinese, Japanese, Korean, and some other languages, the Linux
      console cannot be configured to display the needed characters. Users
      who need such languages should install the X Window System, fonts that
      cover the necessary character ranges, and the proper input method (e.g.,
      SCIM supports a wide variety of languages).</para>
    </listitem>

  </itemizedlist>

  <!-- Added because folks keep posting their console file with X questions
  to blfs-support list -->
  <note>
    <para>The <filename>/etc/sysconfig/console</filename> file only controls
    the Linux text console localization. It has nothing to do with setting
    the proper keyboard layout and terminal fonts in the X Window System, with
    ssh sessions, or with a serial console. In such situations, limitations
    mentioned in the last two list items above do not apply.</para>
  </note>

  </sect2>

  <sect2 id="ch-config-createfiles">
    <title>Creating Files at Boot</title>

    <indexterm zone="ch-config-createfiles">
      <primary sortas="d-createfiles">File creation at boot</primary>
      <secondary>configuring</secondary>
    </indexterm>

    <para>At times, it is desirable to create files at boot time.  For instance,
    the <filename class="directory">/tmp/.ICE-unix</filename> directory
    is often needed.  This can be done by creating an entry in the
    <filename>/etc/sysconfig/createfiles</filename> configuration script.
    The format of this file is embedded in the comments of the default
    configuration file.</para>
  </sect2>

  <sect2 id="ch-config-sysklogd">
    <title>Configuring the Sysklogd Script</title>

    <indexterm zone="ch-config-sysklogd">
      <primary sortas="d-sysklogd">sysklogd</primary>
      <secondary>configuring</secondary>
    </indexterm>

    <para>The <filename>sysklogd</filename> script invokes the
    <command>syslogd</command> program as a part of System V initialization.  The
    <parameter>-m 0</parameter> option turns off the periodic timestamp mark that
    <command>syslogd</command> writes to the log files every 20 minutes by
    default.  If you want to turn on this periodic timestamp mark, edit
    <filename>/etc/sysconfig/rc.site</filename> and define the variable
    SYSKLOGD_PARMS to the desired value.  For instance, to remove all parameters,
    set the variable to a null value:</para>

<screen role="nodump">SYSKLOGD_PARMS=</screen>

    <para>See <userinput>man syslogd</userinput> for more options.</para>

  </sect2>

  <sect2 id="ch-config-site">
    <title>The rc.site File</title>

    <indexterm zone="ch-config-site">
      <primary sortas="a-rc.site">rc.site</primary>
    </indexterm>

    <para>The optional <filename>/etc/sysconfig/rc.site</filename> file contains
    settings that are automatically set for each SystemV boot script.  It can
    alternatively set the values specified in the <filename>hostname</filename>,
    <filename>console</filename>, and <filename>clock</filename> files in the
    <filename class='directory'>/etc/sysconfig/</filename> directory.  If the
    associated variables are present in both these separate files and
    <filename>rc.site</filename>, the values in the script-specific files take
    effect. </para>

    <para><filename>rc.site</filename> also contains parameters that can
    customize other aspects of the boot process.  Setting the IPROMPT variable
    will enable selective running of bootscripts.  Other options are described
    in the file comments.  The default version of the file is as follows:</para>

    <!-- Use role to fix a pdf generation problem -->
    <screen role="auto">&site;</screen>

    <sect3>
      <title>Customizing the Boot and Shutdown Scripts</title>

      <para>The LFS boot scripts boot and shut down a system in a fairly
      efficient manner, but there are a few tweaks you can make in the
      rc.site file to improve speed even more, and to adjust messages according
      to your preferences. To do this, adjust the settings in
      the <filename>/etc/sysconfig/rc.site</filename> file above.</para>

      <itemizedlist>

      <listitem><para>During the boot script <filename>udev</filename>, there is
      a call to <command>udev settle</command> that requires some time to
      complete. This time may or may not be required depending on the devices
      in the system.  If you only have simple partitions and a single ethernet
      card, the boot process will probably not need to wait for this command.  To
      skip it, set the variable OMIT_UDEV_SETTLE=y.</para></listitem>

      <listitem><para>The boot script <filename>udev_retry</filename> also runs
      <command>udev settle</command> by default.  This command is only needed
      if the <filename class='directory'>/var</filename> directory is
      separately mounted, because the clock needs the
      <filename>/var/lib/hwclock/adjtime</filename> file.  Other customizations may
      also need to wait for udev to complete, but in many installations it is not
      necessary.  Skip the command by setting the variable OMIT_UDEV_RETRY_SETTLE=y.
      </para></listitem>

      <listitem><para>By default, the file system checks are silent.  This can
      appear to be a delay during the bootup process.  To turn on the
      <command>fsck</command> output, set the variable VERBOSE_FSCK=y.
      </para></listitem>

      <listitem><para>When rebooting, you may want to skip the filesystem check,
      <command>fsck</command>, completely.  To do this, either create the file
      <filename>/fastboot</filename> or reboot the system with the command
      <command>/sbin/shutdown -f -r now</command>.  On the other hand, you can
      force all file systems to be checked by creating
      <filename>/forcefsck</filename> or running <command>shutdown</command> with
      the <parameter>-F</parameter> parameter instead of <parameter>-f</parameter>.
      </para>

      <para>Setting the variable FASTBOOT=y will disable <command>fsck</command>
      during the boot process until it is removed.  This is not recommended
      on a permanent basis.</para></listitem>

      <listitem><para>Normally, all files in the <filename
      class='directory'>/tmp</filename> directory are deleted at boot time.
      Depending on the number of files or directories present, this can cause a
      noticeable delay in the boot process.  To skip removing these files set the
      variable SKIPTMPCLEAN=y.</para></listitem>

      <listitem><para>During shutdown, the <command>init</command> program sends
      a TERM signal to each program it has started (e.g. agetty), waits for a set
      time (default 3 seconds), then sends each process a KILL signal and waits
      again.  This process is repeated in the <command>sendsignals</command>
      script for any processes that are not shut down by their own scripts.  The
      delay for <command>init</command> can be set by passing a parameter.  For
      example to remove the delay in <command>init</command>, pass the -t0
      parameter when shutting down or rebooting (e.g.  <command>/sbin/shutdown
      -t0 -r now</command>).  The delay for the  <command>sendsignals</command>
      script can be skipped by setting the parameter
      KILLDELAY=0.</para></listitem>

      </itemizedlist>

    </sect3>
  </sect2>
</sect1>