source: chapter08/systemd.xml@ 871fd2f

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  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
  %general-entities;
]>

<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>First, apply a patch to fix the build with GCC-10 and fix a segfault:</para>

<screen><userinput remap="pre">patch -Np1 -i ../systemd-&systemd-version;-gcc_10-fixes-2.patch</userinput></screen>
-->

    <!-- For linux-5.11's API headers changing the rfkill_event structure -->
    <para>First, apply a patch to fix some build issues:</para>

<screen><userinput remap="pre">patch -Np1 -i ../systemd-&systemd-version;-upstream_fixes-1.patch</userinput></screen>

    <para>Remove tests that cannot be built in chroot:</para>

<screen><userinput remap="pre">sed '177,$ d' -i src/resolve/meson.build</userinput></screen>

    <para>Remove an unneeded group,
    <systemitem class="groupname">render</systemitem>, from the default udev
    rules:</para>

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

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

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

LANG=en_US.UTF-8                    \
meson --prefix=/usr                 \
      --sysconfdir=/etc             \
      --localstatedir=/var          \
      -Dblkid=true                  \
      -Dbuildtype=release           \
      -Ddefault-dnssec=no           \
      -Dfirstboot=false             \
      -Dinstall-tests=false         \
      -Dldconfig=false              \
      -Dsysusers=false              \
      -Db_lto=false                 \
      -Drpmmacrosdir=no             \
      -Dhomed=false                 \
      -Duserdb=false                \
      -Dman=false                   \
      -Dmode=release                \
      -Ddocdir=/usr/share/doc/systemd-&systemd-version; \
      ..</userinput></screen>

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

      <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. They are not useful for 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, which is not useful for source
          distributions such as LFS and makes the boot time longer. Remove it
          if the described feature is desired.</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 earlier in this chapter.</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 that have dependencies that do not fit
          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 later.</para>
        </listitem>
      </varlistentry>

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

    </variablelist>

    <para>Compile the package:</para>

<screen><userinput remap="make">LANG=en_US.UTF-8 ninja</userinput></screen>

    <para>Install the package:</para>

<screen><userinput remap="install">LANG=en_US.UTF-8 ninja install</userinput></screen>

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

<screen><userinput remap="install">tar -xf ../../systemd-man-pages-&systemd-man-version;.tar.xz --strip-components=1 -C /usr/share/man</userinput></screen>

    <para>Remove a useless directory:</para>

<screen><userinput remap="install">rm -rf /usr/lib/pam.d</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>Setup the basic target structure:</para>

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

    <para>Disable a service that is known to cause problems with systems that
    use a network configuration other than what is provided by
    systemd-networkd:</para>
    <!-- Observed halting startup with dhcpcd handling the primary NIC -->
 
<screen><userinput remap="adjust">systemctl disable systemd-time-wait-sync.service</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>bootctl, busctl, coredumpctl, halt (symlink to systemctl),
        hostnamectl, init, journalctl, kernel-install, localectl, loginctl,
        machinectl, 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-analyze,
        systemd-ask-password, systemd-cat, systemd-cgls, systemd-cgtop,
        systemd-cryptenroll, 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="bootctl">
        <term><command>bootctl</command></term>
        <listitem>
          <para>Is used to query the firmware and boot manager settings</para>
          <indexterm zone="ch-system-systemd bootctl">
            <primary sortas="b-bootctl">bootctl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <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,
          then 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 when the kernel has initialized
          the hardware which takes over the boot process and starts all 
          processes according to 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-analyze">
        <term><command>systemd-analyze</command></term>
        <listitem>
          <para>Is used to determine system startup performance of the current
          boot, 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 question message specified on the 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 load</para>
          <indexterm zone="ch-system-systemd systemd-cgtop">
            <primary sortas="b-systemd-cgtop">systemd-cgtop</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="systemd-cryptenroll">
        <term><command>systemd-cryptenroll</command></term>
        <listitem>
          <para>Is used to enroll or remove a system from full disk encryption,
          as well as set and query private keys and recovery keys</para>
          <indexterm zone="ch-system-systemd systemd-cryptenroll">
            <primary sortas="b-systemd-cryptenroll">systemd-cryptenroll</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 default
          counterparts 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 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 about 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 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 in 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>