lfs-book-zh_CN/chapter06/systemd.xml

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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-ch6-sbu;</seg>
        <seg>&systemd-ch6-du;</seg>
      </seglistitem>
    </segmentedlist>
  </sect2>

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

    <para>First, fix a build error when using Util-Linux built in
    Chapter 5:</para>

<screen><userinput remap="pre">sed -i "s:blkid/::" $(grep -rl "blkid/blkid.h")</userinput></screen>

<!-- Not needed as of 231. -renodr
    <para>Fix a potential security issue with framebuffer devices:</para>

<screen><userinput remap="pre">sed -e 's@DRI and frame buffer@DRI@'                  \
    -e '/SUBSYSTEM==\"graphics\", KERNEL==\"fb\*\"/d' \
    -i  src/login/70-uaccess.rules</userinput></screen>
-->

    <para>Disable two tests that always fail:</para>

<screen><userinput remap="pre">sed -e 's@test/udev-test.pl @@'  \
    -e 's@test-copy$(EXEEXT) @@' \
    -i Makefile.in</userinput></screen>

<!-- Not needed as of 232... anyone notice a pattern here? -renodr
    <para>Apply a patch to fix a security issue:</para>

<screen><userinput remap="pre">patch -Np1 -i ../systemd-231-security_fix-1.patch</userinput></screen>
-->

    <para>Create a file to allow systemd to build when using Util-Linux
    built in Chapter 5, to disable LTO by default, and to build without
    xlstproc:</para>

<screen><userinput remap="pre">cat &gt; config.cache &lt;&lt; "EOF"
<literal>KILL=/bin/kill
MOUNT_PATH=/bin/mount
UMOUNT_PATH=/bin/umount
HAVE_BLKID=1
BLKID_LIBS="-lblkid"
BLKID_CFLAGS="-I/tools/include/blkid"
HAVE_LIBMOUNT=1
MOUNT_LIBS="-lmount"
MOUNT_CFLAGS="-I/tools/include/libmount"
cc_cv_CFLAGS__flto=no
SULOGIN="/sbin/sulogin"
GPERF_LEN_TYPE=size_t
XSLTPROC="/usr/bin/xsltproc"</literal>
EOF</userinput></screen>

    <para>LTO is disabled by default because it causes
    <command>systemd</command> and other auxiliary programs to link to
    <filename class="libraryfile">libgcc_s.so</filename>, slows the build down
    and makes the compiled code larger.</para>

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

<screen><userinput remap="configure">./configure --prefix=/usr            \
            --sysconfdir=/etc        \
            --localstatedir=/var     \
            --config-cache           \
            --with-rootprefix=       \
            --with-rootlibdir=/lib   \
            --enable-split-usr       \
            --disable-firstboot      \
            --disable-ldconfig       \
            --disable-sysusers       \
            --without-python         \
            --with-default-dnssec=no \
            --docdir=/usr/share/doc/systemd-&systemd-version;</userinput></screen>

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

      <varlistentry>
        <term><parameter>--config-cache</parameter></term>
        <listitem>
          <para>This switch tells the build system to use
          the <filename>config.cache</filename> file which
          was created earlier.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--with-root*</parameter></term>
        <listitem>
          <para>These switches ensure that core programs and
          shared libraries are installed in the subdirectories
          of the root partition.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--enable-split-usr</parameter></term>
        <listitem>
          <para>This switch ensures that systemd will work on
          systems where /bin, /lib and /sbin directories are not
          symlinks to their /usr counterparts.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--without-python</parameter></term>
        <listitem>
          <para>This switch prevents <command>configure</command>
          from trying to use Python which isn't built
          in LFS.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-firstboot</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>--disable-ldconfig</parameter></term>
        <listitem>
          <para>This switch prevents installation of a systemd
          unit that runs <command>ldconfig</command> at
          boot, making the boot time longer. Remove it if the
          described feature is desired, even though it's not
          useful for source distributions such as LFS.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-sysusers</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 early in this chapter.</para>
        </listitem>
      </varlistentry>

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

    </variablelist>

    <para>Fix a generated file:</para>

<screen><userinput remap="pre">sed -i s/size_t/GPERF_LEN_TYPE/ src/resolve/dns_type-from-name.h</userinput></screen>

    <para>Compile the package:</para>

<screen><userinput remap="make">make LD_LIBRARY_PATH=/tools/lib</userinput></screen>

    <para>This package has a test suite, but it can only be run after the
    package has been installed.</para>

    <para>Install the package:</para>

<screen><userinput remap="install">make LD_LIBRARY_PATH=/tools/lib install</userinput></screen>

<!-- These get installed into /lib now by default.
    <para>Move the NSS libraries to <filename class="directory">/lib</filename>:</para>

<screen><userinput remap="install">mv -v /usr/lib/libnss_{myhostname,mymachines,resolve}.so.2 /lib</userinput></screen>
-->

    <para>Remove an unnecessary directory:</para>

<screen><userinput remap="install">rm -rfv /usr/lib/rpm</userinput></screen>

    <para>Create the Sysvinit compatibility symlinks, so systemd is used
    as the default init system:</para>

<screen><userinput remap="install">for tool in runlevel reboot shutdown poweroff halt telinit; do
     ln -sfv ../bin/systemctl /sbin/${tool}
done
ln -sfv ../lib/systemd/systemd /sbin/init</userinput></screen>

<!--
    <para>Remove a reference to a non-existent group:</para>

<screen><userinput remap="install">sed -i "s:0775 root lock:0755 root root:g" /usr/lib/tmpfiles.d/legacy.conf</userinput></screen>
-->

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

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

    <para>Since the testsuite largely depends on the host system kernel
    configuration, some tests may fail. It also needs a modification in
    order not to look for a program that will be installed by Util-Linux
    package later in this chapter. To test the results, issue:</para>

<screen><userinput remap="test">sed -i "s:minix:ext4:g" src/test/test-path-util.c
make LD_LIBRARY_PATH=/tools/lib -k check</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, hostnamectl, init, journalctl,
        kernel-install, localectl, loginctl, machinectl, networkctl, poweroff,
        reboot, runlevel, shutdown, systemctl, systemd-analyze,
        systemd-ask-password, systemd-cat, systemd-cgls, systemd-cgtop,
        systemd-delta, systemd-detect-virt, systemd-escape, systemd-hwdb,
        systemd-inhibit, systemd-machine-id-setup, systemd-mount, 
        systemd-notify, systemd-nspawn, systemd-path, systemd-resolve, 
        systemd-run, systemd-socket-activate,
        systemd-stdio-bridge, systemd-tmpfiles, systemd-tty-ask-password-agent,
        telinit, 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-231.so,
        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, /lib/systemd, /lib/udev, /usr/include/systemd,
        /usr/lib/binfmt.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>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>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>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>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>The first process to be started when the kernel has initialized
          the hardware which takes over the boot process and starts all the
          proceses it is instructed to</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>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>Used to add and remove kernel and initramfs images to and
          from /boot</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>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>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>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>Used to introspect the state of the network links as seen by
          systemd-networkd</para>
          <indexterm zone="ch-system-systemd networkctl">
            <primary sortas="b-networkctl">networkctl</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="poweroff">
        <term><command>poweroff</command></term>
        <listitem>
          <para>Tells 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>Tells 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="runlevel">
        <term><command>runlevel</command></term>
        <listitem>
          <para>Reports the previous and the current run-level, as noted in the
          last run-level record in <filename>/var/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 secure way, 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>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>Used to determine system boot-up performance of the current
          boot</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>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>Used to connect STDOUT and STDERR of a process with the 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-delta">
        <term><command>systemd-delta</command></term>
        <listitem>
          <para>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 execution in a virtualized environment</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-escape">
        <term><command>systemd-escape</command></term>
        <listitem>
          <para>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>Used to manage 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-inhibit">
        <term><command>systemd-inhibit</command></term>
        <listitem>
          <para>Used to execute a program with a shutdown, sleep or idle
          inhibitor lock taken</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>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 a tool to temporarily mount or auto-mount a drive.</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>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>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>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-resolve">
        <term><command>systemd-resolve</command></term>
        <listitem>
          <para>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>Used to create and start a transient .service or a .scope unit
          and run the specified command in it</para>
          <indexterm zone="ch-system-systemd systemd-run">
            <primary sortas="b-systemd-run">systemd-run</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <!-- <varlistentry id="systemd-stdio-bridge">
        <term><command>systemd-stdio-bridge</command></term>
        <listitem>
          <para>To be completed</para>
          <indexterm zone="ch-system-systemd systemd-stdio-bridge">
            <primary sortas="b-systemd-stdio-bridge">systemd-stdio-bridge</primary>
          </indexterm>
        </listitem>
      </varlistentry> -->

      <varlistentry id="systemd-socket-activate">
        <term><command>systemd-socket-activate</command></term>
        <listitem>
          <para>is a tool to listen on socket devices and launch a process upon
          connection.</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-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-tty-ask-password-agent">
        <term><command>systemd-tty-ask-password-agent</command></term>
        <listitem>
          <para>Used to list 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>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>Generic Udev administration tool: controls the udevd daemon,
          provides info from the Udev 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>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>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>