source: chapter08/systemd.xml@ 1e9ad78

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  <!ENTITY % general-entities SYSTEM "../general.ent">
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<sect1 id="ch-system-systemd" role="wrap" revision="systemd">
  <?dbhtml filename="systemd.html"?>

  <sect1info condition="script">
    <productname>systemd</productname>
    <productnumber>&systemd-version;</productnumber>
    <address>&systemd-url;</address>
  </sect1info>

  <title>Systemd-&systemd-version;</title>

  <indexterm zone="ch-system-systemd">
    <primary sortas="a-systemd">systemd</primary>
  </indexterm>

  <sect2 role="package">
    <title/>

    <para>The systemd package contains programs for controlling the startup,
    running, and shutdown of the system.</para>

    <segmentedlist>
      <segtitle>&buildtime;</segtitle>
      <segtitle>&diskspace;</segtitle>

      <seglistitem>
        <seg>&systemd-fin-sbu;</seg>
        <seg>&systemd-fin-du;</seg>
      </seglistitem>
    </segmentedlist>
  </sect2>

  <sect2 role="installation">
    <title>Installation of systemd</title>

    <para>Remove two unneeded groups,
    <systemitem class="groupname">render</systemitem> and
    <systemitem class="groupname">sgx</systemitem>, from the default udev
    rules:</para>

 <screen><userinput remap="pre">sed -i -e 's/GROUP="render"/GROUP="video"/' \
       -e 's/GROUP="sgx", //' rules.d/50-udev-default.rules.in</userinput></screen>

    <para>Prepare systemd for compilation:</para>

<screen><userinput remap="configure">mkdir -p build
cd       build

meson setup \
      --prefix=/usr                 \
      --buildtype=release           \
      -Ddefault-dnssec=no           \
      -Dfirstboot=false             \
      -Dinstall-tests=false         \
      -Dldconfig=false              \
      -Dsysusers=false              \
      -Drpmmacrosdir=no             \
      -Dhomed=false                 \
      -Duserdb=false                \
      -Dman=false                   \
      -Dmode=release                \
      -Dpamconfdir=no               \
      -Ddev-kvm-mode=0660           \
      -Ddocdir=/usr/share/doc/systemd-&systemd-version; \
      ..</userinput></screen>

    <variablelist>
      <title>The meaning of the meson options:</title>

      <varlistentry>
        <term><parameter>--buildtype=release</parameter></term>
        <listitem>
          <para>This switch overrides the default buildtype
          (<quote>debug</quote>), which produces unoptimized
          binaries.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Ddefault-dnssec=no</parameter></term>
        <listitem>
          <para>This switch turns off the experimental DNSSEC support.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Dfirstboot=false</parameter></term>
        <listitem>
          <para>This switch prevents installation of systemd
          services responsible for setting up the system for
          the first time. These are not useful in LFS, because
          everything is done manually.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Dinstall-tests=false</parameter></term>
        <listitem>
          <para>This switch prevents installation of the compiled tests.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Dldconfig=false</parameter></term>
        <listitem>
          <para>This switch prevents installation of a systemd unit that runs
          <command>ldconfig</command> at boot; this is not useful for source
          distributions such as LFS, and makes the boot time longer. Remove 
          this option to enable running <command>ldconfig</command> at boot.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Dsysusers=false</parameter></term>
        <listitem>
          <para>This switch prevents installation of systemd
          services responsible for setting up the
          <filename>/etc/group</filename> and
          <filename>/etc/passwd</filename> files. Both files
          were created in the previous chapter. This daemon is not useful
          on an LFS system since user accounts are manually created.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Drpmmacrosdir=no</parameter></term>
        <listitem>
          <para>This switch disables installation of RPM Macros
          for use with systemd, because LFS does not support RPM.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-D{userdb,homed}=false</parameter></term>
        <listitem>
          <para>Remove two daemons with dependencies that do not fit
          within the scope of LFS.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Dman=false</parameter></term>
        <listitem>
          <para>Prevent the generation of man pages to avoid extra
          dependencies.  We will install pre-generated man pages for systemd
          from a tarball.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Dmode=release</parameter></term>
        <listitem>
          <para>Disable some features considered experimental by upstream.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Dpamconfdir=no</parameter></term>
        <listitem>
          <para>Prevent the installation of a PAM configuration file not
          functional on LFS.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-Ddev-kvm-mode=0660</parameter></term>
        <listitem>
          <para>The default udev rule would allow all users to access
          <filename class='devicefile'>/dev/kvm</filename>.  The editors
          consider it dangerous.  This option overrides it.</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>Compile the package:</para>

<screen><userinput remap="make">ninja</userinput></screen>

    <para>Install the package:</para>

<screen><userinput remap="install">ninja install</userinput></screen>

    <para>Install the man pages:</para>

    <!-- Please make sure systemd man pages tarball has a common leading
         component in the path.  -->
<screen><userinput remap="install">tar -xf ../../systemd-man-pages-&systemd-version;.tar.xz \
    --no-same-owner --strip-components=1   \
    -C /usr/share/man</userinput></screen>

    <para>Create the <filename>/etc/machine-id</filename> file needed by
    <command>systemd-journald</command>:</para>

<screen><userinput remap="adjust">systemd-machine-id-setup</userinput></screen>

    <para>Set up the basic target structure:</para>

<screen><userinput remap="adjust">systemctl preset-all</userinput></screen>

    <para>Disable two services for upgrading binary distros.  They are useless for
    a basic Linux system built from source, and each one will report an error if
    it's enabled but not configured:</para>

<screen><userinput remap="adjust">systemctl disable systemd-sysupdate{,-reboot}</userinput></screen>

<!-- dev: 50-pid-max.conf is not removed in BLFS, so I commented the following out.
          If it causes any trouble, we can add this back and also copy it into BLFS -->
<!--
    <para>Prevent systemd from resetting the maximum PID value which causes
    some problems with packages and units in BLFS:</para>

<screen><userinput remap="adjust">rm -f /usr/lib/sysctl.d/50-pid-max.conf</userinput></screen>
-->

  </sect2>

  <sect2 id="contents-systemd" role="content">
    <title>Contents of systemd</title>

    <segmentedlist>
      <segtitle>Installed programs</segtitle>
      <segtitle>Installed libraries</segtitle>
      <segtitle>Installed directories</segtitle>

      <seglistitem>
        <seg>busctl, coredumpctl, halt (symlink to systemctl),
        hostnamectl, init, journalctl, kernel-install, localectl, loginctl,
        machinectl, mount.ddi (symlink to systemd-dissect), networkctl,
        oomctl, portablectl, poweroff (symlink to
        systemctl), reboot (symlink to systemctl), resolvconf (symlink to
        resolvectl), resolvectl, runlevel (symlink to systemctl), shutdown
        (symlink to systemctl), systemctl, systemd-ac-power, systemd-analyze,
        systemd-ask-password, systemd-cat, systemd-cgls, systemd-cgtop,
        systemd-confext (symlink to systemd-sysext), systemd-creds,
        systemd-delta, systemd-detect-virt,
        systemd-dissect, systemd-escape, systemd-hwdb, systemd-id128,
        systemd-inhibit, systemd-machine-id-setup,
        systemd-mount, systemd-notify, systemd-nspawn, systemd-path,
        systemd-repart, systemd-resolve (symlink to resolvectl), systemd-run,
        systemd-socket-activate, systemd-stdio-bridge, systemd-sysext,
        systemd-tmpfiles, systemd-tty-ask-password-agent,
        systemd-umount (symlink to systemd-mount),
        telinit (symlink to systemctl), timedatectl, and udevadm</seg>
        <seg>libnss_myhostname.so.2, libnss_mymachines.so.2,
        libnss_resolve.so.2, libnss_systemd.so.2,
        libsystemd.so, libsystemd-shared-&systemd-version;.so (in /usr/lib/systemd),
        and libudev.so</seg>
        <seg>/etc/binfmt.d, /etc/init.d, /etc/kernel, /etc/modules-load.d,
        /etc/sysctl.d, /etc/systemd, /etc/tmpfiles.d, /etc/udev,
        /etc/xdg/systemd, /usr/lib/systemd, /usr/lib/udev, /usr/include/systemd,
        /usr/lib/binfmt.d, /usr/lib/environment.d, /usr/lib/kernel,
        /usr/lib/modules-load.d, /usr/lib/sysctl.d, /usr/lib/systemd,
        /usr/lib/tmpfiles.d,
        /usr/share/doc/systemd-&systemd-version;, /usr/share/factory,
        /usr/share/systemd, /var/lib/systemd, and /var/log/journal</seg>
      </seglistitem>
    </segmentedlist>

    <variablelist>
      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
      <?dbfo list-presentation="list"?>
      <?dbhtml list-presentation="table"?>

      <varlistentry id="busctl">
        <term><command>busctl</command></term>
        <listitem>
          <para>Is used to introspect and monitor the D-Bus bus</para>
          <indexterm zone="ch-system-systemd busctl">
            <primary sortas="b-busctl">busctl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="coredumpctl">
        <term><command>coredumpctl</command></term>
        <listitem>
          <para>Is used to retrieve coredumps from the systemd journal</para>
          <indexterm zone="ch-system-systemd coredumpctl">
            <primary sortas="b-coredumpctl">coredumpctl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="halt">
        <term><command>halt</command></term>
        <listitem>
          <para>Normally invokes <command>shutdown</command> with the
          <parameter>-h</parameter> option, except when already in run-level 0,
          when it tells the kernel to halt the system; it notes in the
          file <filename>/var/log/wtmp</filename> that the system is being
          brought down</para>
          <indexterm zone="ch-system-systemd halt">
            <primary sortas="b-halt">halt</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="hostnamectl">
        <term><command>hostnamectl</command></term>
        <listitem>
          <para>Is used to query and change the system hostname and related
          settings</para>
          <indexterm zone="ch-system-systemd hostnamectl">
            <primary sortas="b-hostnamectl">hostnamectl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="init">
        <term><command>init</command></term>
        <listitem>
          <para>Is the first process to be started after the kernel has initialized
          the hardware; <command>init</command> takes over the boot process and starts the
          processes specified by its configuration files; in this case, it starts
          systemd</para>
          <indexterm zone="ch-system-systemd init">
            <primary sortas="b-init">init</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="journalctl">
        <term><command>journalctl</command></term>
        <listitem>
          <para>Is used to query the contents of the systemd journal</para>
          <indexterm zone="ch-system-systemd journalctl">
            <primary sortas="b-journalctl">journalctl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="kernel-install">
        <term><command>kernel-install</command></term>
        <listitem>
          <para>Is used to add and remove kernel and initramfs images to and
          from /boot; in LFS, this is done manually</para>
          <indexterm zone="ch-system-systemd kernel-install">
            <primary sortas="b-kernel-install">kernel-install</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="localectl">
        <term><command>localectl</command></term>
        <listitem>
          <para>Is used to query and change the system locale and keyboard layout
          settings</para>
          <indexterm zone="ch-system-systemd localectl">
            <primary sortas="b-localectl">localectl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="loginctl">
        <term><command>loginctl</command></term>
        <listitem>
          <para>Is used to introspect and control the state of the systemd Login
          Manager</para>
          <indexterm zone="ch-system-systemd loginctl">
            <primary sortas="b-loginctl">loginctl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="machinectl">
        <term><command>machinectl</command></term>
        <listitem>
          <para>Is used to introspect and control the state of the systemd Virtual
          Machine and Container Registration Manager</para>
          <indexterm zone="ch-system-systemd machinectl">
            <primary sortas="b-machinectl">machinectl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="networkctl">
        <term><command>networkctl</command></term>
        <listitem>
          <para>Is used to introspect and configure the state of the network
          links configured by systemd-networkd</para>
          <indexterm zone="ch-system-systemd networkctl">
            <primary sortas="b-networkctl">networkctl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="oomctl">
        <term><command>oomctl</command></term>
        <listitem>
          <para>Controls the systemd Out Of Memory daemon</para>
          <indexterm zone="ch-system-systemd oomctl">
            <primary sortas="b-oomctl">oomctl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="portablectl">
        <term><command>portablectl</command></term>
        <listitem>
          <para>Is used to attach or detach portable services from the local
          system</para>
          <indexterm zone="ch-system-systemd portablectl">
            <primary sortas="b-portablectl">portablectl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="poweroff">
        <term><command>poweroff</command></term>
        <listitem>
          <para>Instructs the kernel to halt the system and switch off the computer
          (see <command>halt</command>)</para>
          <indexterm zone="ch-system-systemd poweroff">
            <primary sortas="b-poweroff">poweroff</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="reboot">
        <term><command>reboot</command></term>
        <listitem>
          <para>Instructs the kernel to reboot the system (see
          <command>halt</command>)</para>
          <indexterm zone="ch-system-systemd reboot">
            <primary sortas="b-reboot">reboot</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="resolvconf">
        <term><command>resolvconf</command></term>
        <listitem>
          <para>Registers DNS server and domain configuration with
          <command>systemd-resolved</command></para>
          <indexterm zone="ch-system-systemd resolvconf">
            <primary sortas="b-resolvconf">resolvconf</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="resolvectl">
        <term><command>resolvectl</command></term>
        <listitem>
          <para>Sends control commands to the network name resolution
          manager, or resolves domain names, IPv4 and IPv6 addresses,
          DNS records, and services</para>
          <indexterm zone="ch-system-systemd resolvectl">
            <primary sortas="b-resolvectl">resolvectl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="runlevel">
        <term><command>runlevel</command></term>
        <listitem>
          <para>Outputs the previous and the current run-level, as noted in the
          last run-level record in <filename>/run/utmp</filename></para>
          <indexterm zone="ch-system-systemd runlevel">
            <primary sortas="b-runlevel">runlevel</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="shutdown">
        <term><command>shutdown</command></term>
        <listitem>
          <para>Brings the system down in a safe and secure manner, signaling
          all processes and notifying all logged-in users</para>
          <indexterm zone="ch-system-systemd shutdown">
            <primary sortas="b-shutdown">shutdown</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemctl">
        <term><command>systemctl</command></term>
        <listitem>
          <para>Is used to introspect and control the state of the systemd system
          and service manager</para>
          <indexterm zone="ch-system-systemd systemctl">
            <primary sortas="b-systemctl">systemctl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-ac-power">
        <term><command>systemd-ac-power</command></term>
        <listitem>
          <para>Reports whether the system is connected to an external
          power source.</para>
          <indexterm zone="ch-system-systemd systemd-ac-power">
            <primary sortas="b-systemd-ac-power">systemd-ac-power</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-analyze">
        <term><command>systemd-analyze</command></term>
        <listitem>
          <para>Is used to analyze system startup performance,
          as well as identify troublesome systemd units</para>
          <indexterm zone="ch-system-systemd systemd-analyze">
            <primary sortas="b-systemd-analyze">systemd-analyze</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-ask-password">
        <term><command>systemd-ask-password</command></term>
        <listitem>
          <para>Is used to query a system password or passphrase from the user,
          using a message specified on the Linux command line</para>
          <indexterm zone="ch-system-systemd systemd-ask-password">
            <primary sortas="b-systemd-ask-password">systemd-ask-password</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-cat">
        <term><command>systemd-cat</command></term>
        <listitem>
          <para>Is used to connect the STDOUT and STDERR outputs of a process
          with the systemd journal
          </para>
          <indexterm zone="ch-system-systemd systemd-cat">
            <primary sortas="b-systemd-cat">systemd-cat</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-cgls">
        <term><command>systemd-cgls</command></term>
        <listitem>
          <para>Recursively shows the contents of the selected Linux control
          group hierarchy in a tree</para>
          <indexterm zone="ch-system-systemd systemd-cgls">
            <primary sortas="b-systemd-cgls">systemd-cgls</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-cgtop">
        <term><command>systemd-cgtop</command></term>
        <listitem>
          <para>Shows the top control groups of the local Linux control group
          hierarchy, ordered by their CPU, memory and disk I/O loads</para>
          <indexterm zone="ch-system-systemd systemd-cgtop">
            <primary sortas="b-systemd-cgtop">systemd-cgtop</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-creds">
        <term><command>systemd-creds</command></term>
        <listitem>
          <para>Displays and processes credentials</para>
          <indexterm zone="ch-system-systemd systemd-creds">
            <primary sortas="b-systemd-creds">systemd-creds</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-delta">
        <term><command>systemd-delta</command></term>
        <listitem>
          <para>Is used to identify and compare configuration files in
          <filename class="directory">/etc</filename> that override the defaults
          in <filename class="directory">/usr</filename></para>
          <indexterm zone="ch-system-systemd systemd-delta">
            <primary sortas="b-systemd-delta">systemd-delta</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-detect-virt">
        <term><command>systemd-detect-virt</command></term>
        <listitem>
          <para>Detects whether the system is being run in a virtual
          environment, and adjusts udev accordingly</para>
          <indexterm zone="ch-system-systemd systemd-detect-virt">
            <primary sortas="b-systemd-detect-virt">systemd-detect-virt</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-dissect">
        <term><command>systemd-dissect</command></term>
        <listitem>
          <para>Is used to inspect OS disk images</para>
          <indexterm zone="ch-system-systemd systemd-dissect">
            <primary sortas="b-systemd-dissect">systemd-dissect</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-escape">
        <term><command>systemd-escape</command></term>
        <listitem>
          <para>Is used to escape strings for inclusion in systemd unit
          names</para>
          <indexterm zone="ch-system-systemd systemd-escape">
            <primary sortas="b-systemd-escape">systemd-escape</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-hwdb">
        <term><command>systemd-hwdb</command></term>
        <listitem>
          <para>Is used to manage the hardware database (hwdb)</para>
          <indexterm zone="ch-system-systemd systemd-hwdb">
            <primary sortas="b-systemd-hwdb">systemd-hwdb</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-id128">
        <term><command>systemd-id128</command></term>
        <listitem>
          <para>Generates and prints id128 (UUID) strings</para>
          <indexterm zone="ch-system-systemd systemd-id128">
            <primary sortas="b-systemd-id128">systemd-id128</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-inhibit">
        <term><command>systemd-inhibit</command></term>
        <listitem>
          <para>Is used to execute a program with a shutdown, sleep or idle
          inhibitor lock taken, preventing an action such as a system shutdown
          until the process is completed</para>
          <indexterm zone="ch-system-systemd systemd-inhibit">
            <primary sortas="b-systemd-inhibit">systemd-inhibit</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-machine-id-setup">
        <term><command>systemd-machine-id-setup</command></term>
        <listitem>
          <para>Is used by system installer tools to initialize the machine ID
          stored in <filename>/etc/machine-id</filename> at install time with a
          randomly generated ID</para>
          <indexterm zone="ch-system-systemd systemd-machine-id-setup">
            <primary sortas="b-systemd-machine-id-setup">systemd-machine-id-setup</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-mount">
        <term><command>systemd-mount</command></term>
        <listitem>
          <para>Is used to temporarily mount or automount disks</para>
          <indexterm zone="ch-system-systemd systemd-mount">
            <primary sortas="b-systemd-mount">systemd-mount</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-notify">
        <term><command>systemd-notify</command></term>
        <listitem>
          <para>Is used by daemon scripts to notify the init system of status
          changes</para>
          <indexterm zone="ch-system-systemd systemd-notify">
            <primary sortas="b-systemd-notify">systemd-notify</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-nspawn">
        <term><command>systemd-nspawn</command></term>
        <listitem>
          <para>Is used to run a command, or an entire OS, in a light-weight namespace
          container</para>
          <indexterm zone="ch-system-systemd systemd-nspawn">
            <primary sortas="b-systemd-nspawn">systemd-nspawn</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-path">
        <term><command>systemd-path</command></term>
        <listitem>
          <para>Is used to query system and user paths</para>
          <indexterm zone="ch-system-systemd systemd-path">
            <primary sortas="b-systemd-path">systemd-path</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-repart">
        <term><command>systemd-repart</command></term>
        <listitem>
          <para>Is used to grow and add partitions to a partition table when
          systemd is used with an OS image (e.g. a container)</para>
          <indexterm zone="ch-system-systemd systemd-repart">
            <primary sortas="b-systemd-repart">systemd-repart</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-resolve">
        <term><command>systemd-resolve</command></term>
        <listitem>
          <para>Is used to resolve domain names, IPV4 and IPv6 addresses, DNS
          resource records, and services</para>
          <indexterm zone="ch-system-systemd systemd-resolve">
            <primary sortas="b-systemd-resolve">systemd-resolve</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-run">
        <term><command>systemd-run</command></term>
        <listitem>
          <para>Is used to create and start a transient .service or a .scope
          unit and run the specified command in it; this is useful for
          validating systemd units</para>
          <indexterm zone="ch-system-systemd systemd-run">
            <primary sortas="b-systemd-run">systemd-run</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-socket-activate">
        <term><command>systemd-socket-activate</command></term>
        <listitem>
          <para>Is used to listen on socket devices and launch a process upon
          a successful connection to the socket</para>
          <indexterm zone="ch-system-systemd systemd-socket-activate">
            <primary sortas="b-systemd-socket-activate">systemd-socket-activate</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-sysext">
        <term><command>systemd-sysext</command></term>
        <listitem>
          <para>Activates system extension images</para>
          <indexterm zone="ch-system-systemd systemd-sysext">
            <primary sortas="b-systemd-sysext">systemd-sysext</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-tmpfiles">
        <term><command>systemd-tmpfiles</command></term>
        <listitem>
          <para>Creates, deletes, and cleans up volatile and temporary files and
          directories, based on the configuration file format and location
          specified in
          <filename class="directory">tmpfiles.d</filename> directories</para>
          <indexterm zone="ch-system-systemd systemd-tmpfiles">
            <primary sortas="b-systemd-tmpfiles">systemd-tmpfiles</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-umount">
        <term><command>systemd-umount</command></term>
        <listitem>
          <para>Unmounts mount points</para>
          <indexterm zone="ch-system-systemd systemd-umount">
            <primary sortas="b-systemd-umount">systemd-umount</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-tty-ask-password-agent">
        <term><command>systemd-tty-ask-password-agent</command></term>
        <listitem>
          <para>Is used to list and/or process pending systemd password
          requests</para>
          <indexterm zone="ch-system-systemd systemd-tty-ask-password-agent">
            <primary sortas="b-systemd-tty-ask-password-agent">systemd-tty-ask-password-agent</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="telinit">
        <term><command>telinit</command></term>
        <listitem>
          <para>Tells <command>init</command> which run-level to change
          to</para>
          <indexterm zone="ch-system-systemd telinit">
            <primary sortas="b-telinit">telinit</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="timedatectl">
        <term><command>timedatectl</command></term>
        <listitem>
          <para>Is used to query and change the system clock and its settings
          </para>
          <indexterm zone="ch-system-systemd timedatectl">
            <primary sortas="b-timedatectl">timedatectl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="udevadm">
        <term><command>udevadm</command></term>
        <listitem>
          <para>Is a generic udev administration tool which controls the udevd
          daemon, provides info from the udev hardware database, monitors
          uevents, waits for uevents to finish, tests udev configuration, and
          triggers uevents for a given device</para>
          <indexterm zone="ch-system-systemd udevadm">
            <primary sortas="b-udevadm">udevadm</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libsystemd">
        <term><filename class="libraryfile">libsystemd</filename></term>
        <listitem>
          <para>Is the main systemd utility library</para>
          <indexterm zone="ch-system-systemd libsystemd">
            <primary sortas="c-libsystemd">libsystemd</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libudev">
        <term><filename class="libraryfile">libudev</filename></term>
        <listitem>
          <para>Is a library to access Udev device information</para>
          <indexterm zone="ch-system-systemd libudev">
            <primary sortas="c-libudev">libudev</primary>
          </indexterm>
        </listitem>
      </varlistentry>

    </variablelist>

  </sect2>

</sect1>