lfs-book/chapter07/sysd-custom.xml

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<sect1 id="ch-scripts-sysd-custom">
  <?dbhtml filename="sysd-custom.html"?>

  <title>Systemd Customization</title>

  <indexterm zone="ch-scripts-sysd-custom">
    <primary sortas="e-Systemd">Systemd Customization</primary>
  </indexterm>

  <sect2>
    <title>Basic Configuration</title>

    <para>The <filename>/etc/systemd/system.conf</filename> file contains a set
    of items to control basic operations.  The default file has all entries
    commented out with the default settings indicated. This file is where the
    log level may be changed as well as some basic journal settings.</para>

  </sect2>

  <sect2>
    <title>Disabling Screen Clearing at Boot Time</title>

    <para>The normal behavior for systemd is to clear the secreen at
    the end of the boot sequence.  If desired, this behavior may be
    changed by the following:</para>

<screen role="nodump"><userinput>mkdir -p /etc/systemd/system/getty@tty1.service.d

cat > /etc/systemd/system/getty@tty1.service.d/noclear.conf &lt;&lt; EOF
[Service]
TTYVTDisallocate=no
EOF</userinput></screen>

    <para>The boot messages can always be revied by using the
    <userinput>journalctl -b</userinput> command as the root user.</para>

  </sect2>

  <sect2>
    <title>Disabling tmpfs for /tmp </title>

    <para>By default, <filename class="directory">/tmp</filename> is created as
    a tmpfs.  If this is not desired, it can be overridden by the following:</para>

<screen role="nodump"><userinput>ln -s /dev/null /etc/systemd/system/tmp.mount</userinput></screen>

    <para>This is not necessary if there is a separate partition for /tmp
    specified in <filename>/etc/fstab</filename>.</para>
  </sect2>

  <sect2>
    <title>Configuring Automatic File Creation and Deletion</title>

    <para>There are several services that create or delete files or
    directories:</para>

    <itemizedlist>
      <listitem><para>systemd-tmpfiles-clean.service</para></listitem>
      <listitem><para>systemd-tmpfiles-setup-dev.service</para></listitem>
      <listitem><para>systemd-tmpfiles-setup.service</para></listitem>
    </itemizedlist>
  
    <para>The system location for the configuration files is
    <filename>/usr/lib/tmpfiles.d/*.conf</filename>.  The local 
    configuration files are in <filename>/etc/tmpfiles.d/*.conf</filename>.
    Files in /etc/tmpfiles.d override files with the same name in 
    /usr/lib/tmpfiles.d.  See <userinput>man tmpfiles.d</userinput> 
    for file format details.</para>

  </sect2>

  <sect2>
    <title>Adding Custom Units and Services</title>

    <para>A custom service can be added by creating a directory and
    configuration file in <filename class="directory">/etc/systemd/system/</filename>.
    For example:</para>

<screen role="nodump"><userinput>mkdir -p /etc/systemd/system/foobar.service.d

cat > /etc/systemd/system/foobar.service.d/foobar.conf &lt;&lt; EOF
[Service]
Restart=always
RestartSec=30
EOF</userinput></screen>

     <para>See the man page for systemd.unit for more information.  After
     creating the configuration file, run <userinput>systemctl
     daemon-reload</userinput> and <userinput>systemctl restart
     foobar</userinput> to activate a service or changes to a service.</para>

  </sect2>

  <sect2>
    <title>Debugging the Boot Sequence</title>

    <para>There are several commands that can be used to help debug the systemd 
    boot process.  Here are some examples:</para>

    <itemizedlist>
       <listitem><para>systemctl list-units -t service [--all]</para></listitem>
       <listitem><para>systemctl list-units -t target  [--all]</para></listitem>
       <listitem><para>systemctl show -p Wants multi-user.target</para></listitem>
       <listitem><para>systemctl status sshd.service</para></listitem>
    </itemizedlist>

  </sect2>

</sect1>