man: grammar and wording improvements

[thirdparty/systemd.git] / man / systemctl.xml

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<refentry id="systemctl">

  <refentryinfo>
    <title>systemctl</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>Lennart</firstname>
        <surname>Poettering</surname>
        <email>lennart@poettering.net</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemctl</refentrytitle>
    <manvolnum>1</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemctl</refname>
    <refpurpose>Control the systemd system and service manager</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>systemctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">COMMAND</arg>
      <arg choice="opt" rep="repeat">NAME</arg>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><command>systemctl</command> may be used to
    introspect and control the state of the
    <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    system and service manager.</para>
  </refsect1>

  <refsect1>
    <title>Options</title>

    <para>The following options are understood:</para>

    <variablelist>
      <varlistentry>
        <term><option>-h</option></term>
        <term><option>--help</option></term>

        <listitem><para>Prints a short help
        text and exits.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--version</option></term>

        <listitem>
          <para>Prints a short version string and exits.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-t</option></term>
        <term><option>--type=</option></term>

        <listitem>
          <para>The argument should be a comma-separated list of unit
          types such as <option>service</option> and
          <option>socket</option>.
          </para>

          <para>If one of the arguments is a unit type, when listing
          units, limit display to certain unit types. Otherwise, units
          of all types will be shown.</para>

          <para>As a special case, if one of the arguments is
          <option>help</option>, a list of allowed values will be
          printed and the program will exit.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--state=</option></term>

        <listitem>
        <para>The argument should be a comma-separated list of unit LOAD,
        SUB, or ACTIVE states. When listing units, show only those
        in specified states.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-p</option></term>
        <term><option>--property=</option></term>

        <listitem>
          <para>When showing unit/job/manager properties with the
          <command>show</command> command, limit display to certain
          properties as specified as argument. If not specified, all
          set properties are shown. The argument should be a
          comma-separated list of property names, such as
          <literal>MainPID</literal>. If specified more than once, all
          properties with the specified names are shown.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-a</option></term>
        <term><option>--all</option></term>

        <listitem>
          <para>When listing units, show all loaded units, regardless
          of their state, including inactive units. When showing
          unit/job/manager properties, show all properties regardless
          whether they are set or not.</para>
          <para>To list all units installed on the system, use the
          <command>list-unit-files</command> command instead.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--reverse</option></term>

        <listitem>
          <para>Show reverse dependencies between units with
          <command>list-dependencies</command>, i.e. units with
          dependencies of type <varname>Wants=</varname> or
          <varname>Requires=</varname> on the given unit.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--after</option></term>
        <term><option>--before</option></term>

        <listitem>
          <para>Show which units are started after or before
          with <command>list-dependencies</command>, respectively.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-l</option></term>
        <term><option>--full</option></term>

        <listitem>
          <para>Do not ellipsize unit names, process tree entries,
          journal output, or truncate unit descriptions in the output
          of <command>status</command>, <command>list-units</command>,
          <command>list-jobs</command>, and
          <command>list-timers</command>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--show-types</option></term>

        <listitem>
          <para>When showing sockets, show the type of the socket.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--job-mode=</option></term>

        <listitem>
        <para>When queuing a new job, this option controls how to deal with
        already queued jobs. It takes one of <literal>fail</literal>,
        <literal>replace</literal>,
        <literal>replace-irreversibly</literal>,
        <literal>isolate</literal>,
        <literal>ignore-dependencies</literal>,
        <literal>ignore-requirements</literal> or
        <literal>flush</literal>. Defaults to
        <literal>replace</literal>, except when the
        <command>isolate</command> command is used which implies the
        <literal>isolate</literal> job mode.</para>

        <para>If <literal>fail</literal> is specified and a requested
        operation conflicts with a pending job (more specifically:
        causes an already pending start job to be reversed into a stop
        job or vice versa), cause the operation to fail.</para>

        <para>If <literal>replace</literal> (the default) is
        specified, any conflicting pending job will be replaced, as
        necessary.</para>

        <para>If <literal>replace-irreversibly</literal> is specified,
        operate like <literal>replace</literal>, but also mark the new
        jobs as irreversible. This prevents future conflicting
        transactions from replacing these jobs. The jobs can still be
        cancelled using the <command>cancel</command> command.</para>

        <para><literal>isolate</literal> is only valid for start
        operations and causes all other units to be stopped when the
        specified unit is started. This mode is always used when the
        <command>isolate</command> command is used.</para>

        <para><literal>flush</literal> will cause all queued jobs to
        be canceled when the new job is enqueued.</para>

        <para>If <literal>ignore-dependencies</literal> is specified,
        then all unit dependencies are ignored for this new job and
        the operation is executed immediately. If passed, no required
        units of the unit passed will be pulled in, and no ordering
        dependencies will be honored. This is mostly a debugging and
        rescue tool for the administrator and should not be used by
        applications.</para>

        <para><literal>ignore-requirements</literal> is similar to
        <literal>ignore-dependencies</literal>, but only causes the
        requirement dependencies to be ignored, the ordering
        dependencies will still be honoured.</para>
        </listitem>

      </varlistentry>

      <varlistentry>
        <term><option>-i</option></term>
        <term><option>--ignore-inhibitors</option></term>

        <listitem>
          <para>When system shutdown or a sleep state is requested,
          ignore inhibitor locks. Applications can establish inhibitor
          locks to avoid that certain important operations (such as CD
          burning or suchlike) are interrupted by system shutdown or a
          sleep state. Any user may take these locks and privileged
          users may override these locks. If any locks are taken,
          shutdown and sleep state requests will normally fail
          (regardless of whether privileged or not) and a list of active locks
          is printed. However, if <option>--ignore-inhibitors</option>
          is specified, the locks are ignored and not printed, and the
          operation attempted anyway, possibly requiring additional
          privileges.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-q</option></term>
        <term><option>--quiet</option></term>

        <listitem>
          <para>Suppress output to standard output in
          <command>snapshot</command>,
          <command>is-active</command>,
          <command>is-failed</command>,
          <command>enable</command> and
        <command>disable</command>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--no-block</option></term>

        <listitem>
          <para>Do not synchronously wait for the requested operation
          to finish. If this is not specified, the job will be
          verified, enqueued and <command>systemctl</command> will
          wait until it is completed. By passing this argument, it is
          only verified and enqueued.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--no-legend</option></term>

        <listitem>
          <para>Do not print the legend, i.e. the column headers and
          the footer with hints.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--no-pager</option></term>

        <listitem>
          <para>Do not pipe output into a pager.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--system</option></term>

        <listitem>
          <para>Talk to the systemd system manager. (Default)</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--user</option></term>

        <listitem>
          <para>Talk to the systemd manager of the calling
          user.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--no-wall</option></term>

        <listitem>
          <para>Do not send wall message before halt, power-off,
          reboot.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--global</option></term>

        <listitem>
          <para>When used with <command>enable</command> and
          <command>disable</command>, operate on the global user
          configuration directory, thus enabling or disabling a unit
          file globally for all future logins of all users.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--no-reload</option></term>

        <listitem>
          <para>When used with <command>enable</command> and
          <command>disable</command>, do not implicitly reload daemon
          configuration after executing the changes.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--no-ask-password</option></term>

        <listitem>
          <para>When used with <command>start</command> and related
          commands, disables asking for passwords. Background services
          may require input of a password or passphrase string, for
          example to unlock system hard disks or cryptographic
          certificates. Unless this option is specified and the
          command is invoked from a terminal,
          <command>systemctl</command> will query the user on the
          terminal for the necessary secrets. Use this option to
          switch this behavior off. In this case, the password must be
          supplied by some other means (for example graphical password
          agents) or the service might fail. This also disables
          querying the user for authentication for privileged
          operations.</para>
        </listitem>

      </varlistentry>

      <varlistentry>
        <term><option>--kill-who=</option></term>

        <listitem>
          <para>When used with <command>kill</command>, choose which
          processes to kill. Must be one of <option>main</option>,
          <option>control</option> or <option>all</option> to select
          whether to kill only the main process of the unit, the
          control process or all processes of the unit. If omitted,
          defaults to <option>all</option>.</para>
        </listitem>

      </varlistentry>

      <varlistentry>
        <term><option>-s</option></term>
        <term><option>--signal=</option></term>

        <listitem>
          <para>When used with <command>kill</command>, choose which
          signal to send to selected processes. Must be one of the
          well known signal specifiers such as <constant>SIGTERM</constant>, <constant>SIGINT</constant> or
          <constant>SIGSTOP</constant>. If omitted, defaults to
          <option>SIGTERM</option>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-f</option></term>
        <term><option>--force</option></term>

        <listitem>
          <para>When used with <command>enable</command>, overwrite
          any existing conflicting symlinks.</para>

          <para>When used with <command>halt</command>,
          <command>poweroff</command>, <command>reboot</command> or
          <command>kexec</command>, execute the selected operation
          without shutting down all units. However, all processes will
          be killed forcibly and all file systems are unmounted or
          remounted read-only. This is hence a drastic but relatively
          safe option to request an immediate reboot. If
          <option>--force</option> is specified twice for these
          operations, they will be executed immediately without
          terminating any processes or umounting any file
          systems. Warning: specifying <option>--force</option> twice
          with any of these operations might result in data
          loss.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--root=</option></term>

        <listitem>
          <para>When used with
          <command>enable</command>/<command>disable</command>/<command>is-enabled</command>
          (and related commands), use alternative root path when
          looking for unit files.</para>
        </listitem>

      </varlistentry>

      <varlistentry>
        <term><option>--runtime</option></term>

        <listitem>
          <para>When used with <command>enable</command>,
          <command>disable</command>,
          (and related commands), make changes only temporarily, so
          that they are lost on the next reboot. This will have the
          effect that changes are not made in subdirectories of
          <filename>/etc</filename> but in <filename>/run</filename>,
          with identical immediate effects, however, since the latter
          is lost on reboot, the changes are lost too.</para>

          <para>Similarly, when used with
          <command>set-property</command>, make changes only
          temporarily, so that they are lost on the next
          reboot.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-H</option></term>
        <term><option>--host</option></term>

        <listitem>
          <para>Execute the operation remotely. Specify a hostname, or
          username and hostname separated by <literal>@</literal>, to
          connect to. This will use SSH to talk to the remote systemd
          instance.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
          <term><option>-M</option></term>
          <term><option>--machine=</option></term>

          <listitem><para>Execute the operation on a local
          container. Specify a container name to connect
          to.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-n</option></term>
        <term><option>--lines=</option></term>

        <listitem>
          <para>When used with <command>status</command>, controls the
          number of journal lines to show, counting from the most
          recent ones. Takes a positive integer argument. Defaults to
          10.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-o</option></term>
        <term><option>--output=</option></term>

        <listitem>
          <para>When used with <command>status</command>, controls the
          formatting of the journal entries that are shown. For the
          available choices, see
          <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
          Defaults to <literal>short</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--plain</option></term>

        <listitem>
          <para>When used with <command>list-dependencies</command>,
          the output is printed as a list instead of a tree.</para>
        </listitem>
      </varlistentry>

    </variablelist>
  </refsect1>

  <refsect1>
    <title>Commands</title>

    <para>The following commands are understood:</para>

    <refsect2>
      <title>Unit Commands</title>

      <variablelist>
        <varlistentry>
          <term><command>list-units <optional><replaceable>PATTERN</replaceable>...</optional></command></term>

          <listitem>
            <para>List known units (subject to limitations specified
            with <option>-t</option>). If one or more
            <replaceable>PATTERN</replaceable>s are specified, only
            units matching one of them are shown.</para>

            <para>This is the default command.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>list-sockets <optional><replaceable>PATTERN</replaceable>...</optional></command></term>

          <listitem>
            <para>List socket units ordered by listening address.
            If one or more <replaceable>PATTERN</replaceable>s are
            specified, only socket units matching one of them are
            shown. Produces output similar to
            <programlisting>
LISTEN           UNIT                        ACTIVATES
/dev/initctl     systemd-initctl.socket      systemd-initctl.service
...
[::]:22          sshd.socket                 sshd.service
kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service

5 sockets listed.
            </programlisting>
            Note: because the addresses might contains spaces, this output
            is not suitable for programmatic consumption.
            </para>

            <para>See also the options <option>--show-types</option>,
            <option>--all</option>, and <option>--failed</option>.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>list-timers <optional><replaceable>PATTERN</replaceable>...</optional></command></term>

          <listitem>
            <para>List timer units ordered by the time they elapse
            next. If one or more <replaceable>PATTERN</replaceable>s
            are specified, only units matching one of them are shown.
            </para>

            <para>See also the options <option>--all</option> and
            <option>--failed</option>.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>start <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Start (activate) one or more units specified on the
            command line.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>stop <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Stop (deactivate) one or more units specified on the
            command line.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>reload <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Asks all units listed on the command line to reload
            their configuration. Note that this will reload the
            service-specific configuration, not the unit configuration
            file of systemd. If you want systemd to reload the
            configuration file of a unit, use the
            <command>daemon-reload</command> command. In other words:
            for the example case of Apache, this will reload Apache's
            <filename>httpd.conf</filename> in the web server, not the
            <filename>apache.service</filename> systemd unit
            file.</para>

            <para>This command should not be confused with the
            <command>daemon-reload</command> or <command>load</command>
            commands.</para>
          </listitem>

        </varlistentry>
        <varlistentry>
          <term><command>restart <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Restart one or more units specified on the command
            line. If the units are not running yet, they will be
            started.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>try-restart <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Restart one or more units specified on the command
            line if the units are running. This does nothing if units are not
            running.  Note that, for compatibility with Red Hat init
            scripts, <command>condrestart</command> is equivalent to this
            command.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>reload-or-restart <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Reload one or more units if they support it. If not,
            restart them instead. If the units are not running yet, they
            will be started.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>reload-or-try-restart <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Reload one or more units if they support it. If not,
            restart them instead. This does nothing if the units are not
            running. Note that, for compatibility with SysV init scripts,
            <command>force-reload</command> is equivalent to this
            command.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>isolate <replaceable>NAME</replaceable></command></term>

          <listitem>
            <para>Start the unit specified on the command line and its
            dependencies and stop all others.</para>

            <para>This is similar to changing the runlevel in a
            traditional init system. The <command>isolate</command>
            command will immediately stop processes that are not enabled
            in the new unit, possibly including the graphical
            environment or terminal you are currently using.</para>

            <para>Note that this is allowed only on units where
            <option>AllowIsolate=</option> is enabled. See
            <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
            for details.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>kill <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Send a signal to one or more processes of the
            unit. Use <option>--kill-who=</option> to select which
            process to kill. Use <option>--kill-mode=</option> to select
            the kill mode and <option>--signal=</option> to select the
            signal to send.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>is-active <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Check whether any of the specified units are active
            (i.e. running). Returns an exit code 0 if at least one is
            active, or non-zero otherwise. Unless <option>--quiet</option>
            is specified, this will also print the current unit state to
            STDOUT.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>is-failed <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Check whether any of the specified units are in a "failed" state.
            Returns an exit code 0 if at least one has failed, non-zero
            otherwise. Unless <option>--quiet</option> is specified, this
            will also print the current unit state to
            STDOUT.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>status</command> <optional><replaceable>NAME</replaceable>...|<replaceable>PID</replaceable>...]</optional></term>

          <listitem>
            <para>Show terse runtime status information about one or
            more units, followed by most recent log data from the
            journal. If no units are specified, show all units (subject
            to limitations specified with <option>-t</option>). If a PID
            is passed, show information about the unit the process
            belongs to.</para>

            <para>This function is intended to generate human-readable
            output. If you are looking for computer-parsable output,
            use <command>show</command> instead. By default this
            function only shows 10 lines of output and ellipsizes
            lines to fit in the terminal window. This can be changes
            with <option>--lines</option> and <option>--full</option>,
            see above. In addition, <command>journalctl
            --unit=<replaceable>NAME</replaceable></command> or
            <command>journalctl
            --user-unit=<replaceable>NAME</replaceable></command> use
            a similar filter for messages and might be more
            convenient.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>show</command> <optional><replaceable>NAME</replaceable>...|<replaceable>JOB</replaceable>...</optional></term>

          <listitem>
            <para>Show properties of one or more units, jobs, or the
            manager itself. If no argument is specified, properties of
            the manager will be shown. If a unit name is specified,
            properties of the unit is shown, and if a job id is
            specified, properties of the job is shown. By default, empty
            properties are suppressed. Use <option>--all</option> to
            show those too. To select specific properties to show, use
            <option>--property=</option>. This command is intended to be
            used whenever computer-parsable output is required. Use
            <command>status</command> if you are looking for formatted
            human-readable output.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>cat <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Show backing files of one or more units. Prints the
            "fragment" and "drop-ins" (source files) of units. Each
            file is preceded by a comment which includes the file
            name.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>set-property <replaceable>NAME</replaceable> <replaceable>ASSIGNMENT</replaceable>...</command></term>

          <listitem>
            <para>Set the specified unit properties at runtime where
            this is supported. This allows changing configuration
            parameter properties such as resource control settings at
            runtime. Not all properties may be changed at runtime, but
            many resource control settings (primarily those in
            <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
            may. The changes are applied instantly, and stored on disk
            for future boots, unless <option>--runtime</option> is
            passed, in which case the settings only apply until the
            next reboot. The syntax of the property assignment follows
            closely the syntax of assignments in unit files.</para>

            <para>Example: <command>systemctl set-property foobar.service CPUShares=777</command></para>

            <para>Note that this command allows changing multiple
            properties at the same time, which is preferable over
            setting them individually. Like unit file configuration
            settings, assigning the empty list to list parameters will
            reset the list.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>help <replaceable>NAME</replaceable>...|<replaceable>PID</replaceable>...</command></term>

          <listitem>
            <para>Show manual pages for one or more units, if
            available. If a PID is given, the manual pages for the unit
            the process belongs to are shown.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>reset-failed [<replaceable>NAME</replaceable>...]</command></term>

          <listitem>
            <para>Reset the <literal>failed</literal> state of the
            specified units, or if no unit name is passed, reset the state of all
            units. When a unit fails in some way (i.e. process exiting
            with non-zero error code, terminating abnormally or timing
            out), it will automatically enter the
            <literal>failed</literal> state and its exit code and status
            is recorded for introspection by the administrator until the
            service is restarted or reset with this command.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>list-dependencies <replaceable>NAME</replaceable></command></term>

          <listitem>
            <para>Shows required and wanted units of the specified
            unit. If no unit is specified,
            <filename>default.target</filename> is implied. Target units
            are recursively expanded.  When <option>--all</option> is
            passed, all other units are recursively expanded as
            well.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Unit File Commands</title>

      <variablelist>
        <varlistentry>
          <term><command>list-unit-files <optional><replaceable>PATTERN...</replaceable></optional></command></term>

          <listitem>
            <para>List installed unit files. If one or more
            <replaceable>PATTERN</replaceable>s are specified, only
            units whose filename (just the last component of the path)
            matches one of them are shown.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>enable <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Enable one or more unit files or unit file instances,
            as specified on the command line. This will create a number
            of symlinks as encoded in the <literal>[Install]</literal>
            sections of the unit files. After the symlinks have been
            created, the systemd configuration is reloaded (in a way that
            is equivalent to <command>daemon-reload</command>) to ensure
            the changes are taken into account immediately. Note that
            this does <emphasis>not</emphasis> have the effect of also
            starting any of the units being enabled. If this
            is desired, a separate <command>start</command> command must
            be invoked for the unit. Also note that in case of instance
            enablement, symlinks named the same as instances are created in
            the install location, however they all point to the same
            template unit file.</para>

            <para>This command will print the actions executed. This
            output may be suppressed by passing <option>--quiet</option>.
            </para>

            <para>Note that this operation creates only the suggested
            symlinks for the units. While this command is the
            recommended way to manipulate the unit configuration
            directory, the administrator is free to make additional
            changes manually by placing or removing symlinks in the
            directory. This is particularly useful to create
            configurations that deviate from the suggested default
            installation. In this case, the administrator must make sure
            to invoke <command>daemon-reload</command> manually as
            necessary to ensure the changes are taken into account.
            </para>

            <para>Enabling units should not be confused with starting
            (activating) units, as done by the <command>start</command>
            command. Enabling and starting units is orthogonal: units
            may be enabled without being started and started without
            being enabled. Enabling simply hooks the unit into various
            suggested places (for example, so that the unit is
            automatically started on boot or when a particular kind of
            hardware is plugged in). Starting actually spawns the daemon
            process (in case of service units), or binds the socket (in
            case of socket units), and so on.</para>

            <para>Depending on whether <option>--system</option>,
            <option>--user</option>, <option>--runtime</option>,
            or <option>--global</option> is specified, this enables the unit
            for the system, for the calling user only, for only this boot of
            the system, or for all future logins of all users, or only this
            boot.  Note that in the last case, no systemd daemon
            configuration is reloaded.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>disable <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Disables one or more units. This removes all symlinks
            to the specified unit files from the unit configuration
            directory, and hence undoes the changes made by
            <command>enable</command>. Note however that this removes
            all symlinks to the unit files (i.e. including manual
            additions), not just those actually created by
            <command>enable</command>. This call implicitly reloads the
            systemd daemon configuration after completing the disabling
            of the units. Note that this command does not implicitly
            stop the units that are being disabled. If this is desired,
            an additional <command>stop</command> command should be
            executed afterwards.</para>

            <para>This command will print the actions executed. This
            output may be suppressed by passing <option>--quiet</option>.
            </para>

            <para>This command honors <option>--system</option>,
            <option>--user</option>, <option>--runtime</option> and
            <option>--global</option> in a similar way as
            <command>enable</command>.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>is-enabled <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Checks whether any of the specified unit files are
            enabled (as with <command>enable</command>). Returns an
            exit code of 0 if at least one is enabled, non-zero
            otherwise. Prints the current enable status (see table).
            To suppress this output, use <option>--quiet</option>.
            </para>

            <table>
              <title>
                <command>is-enabled</command> output
              </title>

              <tgroup cols='3'>
                <thead>
                  <row>
                    <entry>Printed string</entry>
                    <entry>Meaning</entry>
                    <entry>Return value</entry>
                  </row>
                </thead>
                <tbody>
                  <row>
                    <entry><literal>enabled</literal></entry>
                    <entry morerows='1'>Enabled through a symlink in <filename>.wants</filename> directory (permanently or just in <filename>/run</filename>)</entry>
                    <entry morerows='1'>0</entry>
                  </row>
                  <row>
                    <entry><literal>enabled-runtime</literal></entry>
                  </row>
                  <row>
                    <entry><literal>linked</literal></entry>
                    <entry morerows='1'>Made available through a symlink to the unit file (permanently or just in <filename>/run</filename>)</entry>
                    <entry morerows='1'>1</entry>
                  </row>
                  <row>
                    <entry><literal>linked-runtime</literal></entry>
                  </row>
                  <row>
                    <entry><literal>masked</literal></entry>
                    <entry morerows='1'>Disabled entirely (permanently or just in <filename>/run</filename>)</entry>
                    <entry morerows='1'>1</entry>
                  </row>
                  <row>
                    <entry><literal>masked-runtime</literal></entry>
                  </row>
                  <row>
                    <entry><literal>static</literal></entry>
                    <entry>Unit is not enabled, but has no provisions for enabling in [Install] section</entry>
                    <entry>1</entry>
                  </row>
                  <row>
                    <entry><literal>disabled</literal></entry>
                    <entry>Unit is not enabled</entry>
                    <entry>1</entry>
                  </row>
                </tbody>
              </tgroup>
            </table>

          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>reenable <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Reenable one or more unit files, as specified on the
            command line. This is a combination of
            <command>disable</command> and <command>enable</command> and
            is useful to reset the symlinks a unit is enabled with to
            the defaults configured in the <literal>[Install]</literal>
            section of the unit file.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>preset <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Reset one or more unit files, as specified on the
            command line, to the defaults configured in the preset
            policy files. This has the same effect as
            <command>disable</command> or <command>enable</command>,
            depending how the unit is listed in the preset files. For
            more information on the preset policy format, see
            <citerefentry><refentrytitle>systemd.preset</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
            For more information on the concept of presets, please
            consult the
            <ulink url="http://freedesktop.org/wiki/Software/systemd/Preset">Preset</ulink>
            document.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>mask <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Mask one or more unit files, as specified on the
            command line. This will link these units to
            <filename>/dev/null</filename>, making it impossible to
            start them. This is a stronger version of
            <command>disable</command>, since it prohibits all kinds of
            activation of the unit, including manual activation. Use
            this option with care. This honors the
            <option>--runtime</option> option to only mask temporarily
            until the next reoobt of the system.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>unmask <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Unmask one or more unit files, as specified on the
            command line. This will undo the effect of
            <command>mask</command>.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>link <replaceable>FILENAME</replaceable>...</command></term>

          <listitem>
            <para>Link a unit file that is not in the unit file search
            paths into the unit file search path. This requires an
            absolute path to a unit file. The effect of this can be
            undone with <command>disable</command>. The effect of this
            command is that a unit file is available for
            <command>start</command> and other commands although it
            is not installed directly in the unit search path.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>get-default</command></term>

          <listitem>
            <para>Get the default target specified
            via <filename>default.target</filename> link.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><command>set-default <replaceable>NAME</replaceable></command></term>

          <listitem>
            <para>Set the default target to boot into. Command links
            <filename>default.target</filename> to the given unit.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Job Commands</title>

      <variablelist>
        <varlistentry>
          <term><command>list-jobs <optional><replaceable>PATTERN...</replaceable></optional></command></term>

          <listitem>
            <para>List jobs that are in progress. If one or more
            <replaceable>PATTERN</replaceable>s are specified, only
            jobs for units matching one of them are shown.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>cancel <replaceable>JOB</replaceable>...</command></term>

          <listitem>
            <para>Cancel one or more jobs specified on the command line
            by their numeric job IDs. If no job ID is specified, cancel
            all pending jobs.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Snapshot Commands</title>

      <variablelist>
        <varlistentry>
          <term><command>snapshot <optional><replaceable>NAME</replaceable></optional></command></term>

          <listitem>
            <para>Create a snapshot. If a snapshot name is specified,
            the new snapshot will be named after it. If none is
            specified, an automatic snapshot name is generated. In either
            case, the snapshot name used is printed to STDOUT, unless
            <option>--quiet</option> is specified.</para>

            <para>A snapshot refers to a saved state of the systemd
            manager. It is implemented itself as a unit that is
            generated dynamically with this command and has dependencies
            on all units active at the time. At a later time, the user
            may return to this state by using the
            <command>isolate</command> command on the snapshot unit.
            </para>

            <para>Snapshots are only useful for saving and restoring
            which units are running or are stopped, they do not
            save/restore any other state. Snapshots are dynamic and lost
            on reboot.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>delete <replaceable>NAME</replaceable>...</command></term>

          <listitem>
            <para>Remove a snapshot previously created with
            <command>snapshot</command>.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Environment Commands</title>

      <variablelist>
        <varlistentry>
          <term><command>show-environment</command></term>

          <listitem>
            <para>Dump the systemd manager environment block. The
            environment block will be dumped in straight-forward form
            suitable for sourcing into a shell script. This environment
            block will be passed to all processes the manager
            spawns.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>set-environment <replaceable>VARIABLE=VALUE</replaceable>...</command></term>

          <listitem>
            <para>Set one or more systemd manager environment variables,
            as specified on the command line.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>unset-environment <replaceable>VARIABLE</replaceable>...</command></term>

          <listitem>
            <para>Unset one or more systemd manager environment
            variables. If only a variable name is specified, it will be
            removed regardless of its value. If a variable and a value
            are specified, the variable is only removed if it has the
            specified value.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Manager Lifecycle Commands</title>

      <variablelist>
        <varlistentry>
          <term><command>daemon-reload</command></term>

          <listitem>
            <para>Reload systemd manager configuration. This will reload
            all unit files and recreate the entire dependency
            tree. While the daemon is being reloaded, all sockets systemd
            listens on on behalf of user configuration will stay
            accessible.</para> <para>This command should not be confused
            with the <command>load</command> or
            <command>reload</command> commands.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>daemon-reexec</command></term>

          <listitem>
            <para>Reexecute the systemd manager. This will serialize the
            manager state, reexecute the process and deserialize the
            state again. This command is of little use except for
            debugging and package upgrades. Sometimes, it might be
            helpful as a heavy-weight <command>daemon-reload</command>.
            While the daemon is being reexecuted, all sockets systemd listening
            on behalf of user configuration will stay accessible.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>System Commands</title>

      <variablelist>
        <varlistentry>
          <term><command>default</command></term>

          <listitem>
            <para>Enter default mode. This is mostly equivalent to
            <command>isolate default.target</command>.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>rescue</command></term>

          <listitem>
            <para>Enter rescue mode. This is mostly equivalent to
            <command>isolate rescue.target</command>, but also prints a
            wall message to all users.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>emergency</command></term>

          <listitem>
            <para>Enter emergency mode. This is mostly equivalent to
            <command>isolate emergency.target</command>, but also prints
            a wall message to all users.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>halt</command></term>

          <listitem>
            <para>Shut down and halt the system. This is mostly equivalent to
            <command>start halt.target --irreversible</command>, but also
            prints a wall message to all users.  If combined with
            <option>--force</option>, shutdown of all running services is
            skipped, however all processes are killed and all file
            systems are unmounted or mounted read-only, immediately
            followed by the system halt.  If <option>--force</option> is
            specified twice, the operation is immediately executed
            without terminating any processes or unmounting any file
            systems. This may result in data loss.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>poweroff</command></term>

          <listitem>
            <para>Shut down and power-off the system. This is mostly
            equivalent to <command>start poweroff.target --irreversible</command>,
            but also prints a wall message to all users. If combined with
            <option>--force</option>, shutdown of all running services is
            skipped, however all processes are killed and all file
            systems are unmounted or mounted read-only, immediately
            followed by the powering off. If <option>--force</option> is
            specified twice, the operation is immediately executed
            without terminating any processes or unmounting any file
            systems. This may result in data loss.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>reboot <optional><replaceable>arg</replaceable></optional></command></term>

          <listitem>
            <para>Shut down and reboot the system. This is mostly
            equivalent to <command>start reboot.target --irreversible</command>,
            but also prints a wall message to all users. If combined with
            <option>--force</option>, shutdown of all running services is
            skipped, however all processes are killed and all file
            systems are unmounted or mounted read-only, immediately
            followed by the reboot. If <option>--force</option> is
            specified twice, the operation is immediately executed
            without terminating any processes or unmounting any file
            systems. This may result in data loss.</para>

            <para>If the optional argument
            <replaceable>arg</replaceable> is given, it will be passed
            as the optional argument to the
            <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
            system call. The value is architecture and firmware
            specific. As an example, <literal>recovery</literal> might
            be used to trigger system recovery, and
            <literal>fota</literal> might be used to trigger a
            <quote>firmware over the air</quote> update.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>kexec</command></term>

          <listitem>
            <para>Shut down and reboot the system via kexec. This is
            mostly equivalent to <command>start kexec.target --irreversible</command>,
            but also prints a wall message to all users. If combined
            with <option>--force</option>, shutdown of all running
            services is skipped, however all processes are killed and
            all file systems are unmounted or mounted read-only,
            immediately followed by the reboot.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>exit</command></term>

          <listitem>
            <para>Ask the systemd manager to quit. This is only
            supported for user service managers (i.e. in conjunction
            with the <option>--user</option> option) and will fail
            otherwise.</para>
          </listitem>

        </varlistentry>
        <varlistentry>
          <term><command>suspend</command></term>

          <listitem>
            <para>Suspend the system. This will trigger activation of
            the special <filename>suspend.target</filename> target.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>hibernate</command></term>

          <listitem>
            <para>Hibernate the system. This will trigger activation of
            the special <filename>hibernate.target</filename> target.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>hybrid-sleep</command></term>

          <listitem>
            <para>Hibernate and suspend the system. This will trigger
            activation of the special
            <filename>hybrid-sleep.target</filename> target.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><command>switch-root <replaceable>ROOT</replaceable> <optional><replaceable>INIT</replaceable></optional></command></term>

          <listitem>
            <para>Switches to a different root directory and executes a
            new system manager process below it. This is intended for
            usage in initial RAM disks ("initrd"), and will transition
            from the initrd's system manager process (a.k.a "init"
            process) to the main system manager process. This call takes two
            arguments: the directory that is to become the new root directory, and
            the path to the new system manager binary below it to
            execute as PID 1. If the latter is omitted or the empty
            string, a systemd binary will automatically be searched for
            and used as init. If the system manager path is omitted or
            equal to the empty string, the state of the initrd's system
            manager process is passed to the main system manager, which
            allows later introspection of the state of the services
            involved in the initrd boot.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </refsect2>

    <refsect2>
      <title>Parameter Syntax</title>

    <para>For unit commands, the specified
    <replaceable>NAME</replaceable> should be the full name of the
    unit, or an abbreviated name which is automatically extended with
    the <literal>.service</literal> suffix.
    <programlisting># systemctl start foo.service</programlisting> is equivalent to:
    <programlisting># systemctl start foo</programlisting>
    Note that (absolute) paths to device nodes are automatically converted to device unit names, and other (absolute) paths to mount unit names.
    <programlisting># systemctl status /dev/sda
# systemctl status /home</programlisting> is equivalent to:
    <programlisting># systemctl status dev-sda.device
# systemctl status home.mount</programlisting></para>

    <para>For unit file commands, the
    specified <replaceable>NAME</replaceable> should be the full name
    of the unit file, or the absolute path to the unit file.
    <programlisting># systemctl link /path/to/foo.service</programlisting>
    </para>
    </refsect2>

  </refsect1>

  <refsect1>
    <title>Exit status</title>

    <para>On success, 0 is returned, a non-zero failure
    code otherwise.</para>
  </refsect1>

  <refsect1>
    <title>Environment</title>

    <variablelist class='environment-variables'>
      <varlistentry>
        <term><varname>$SYSTEMD_PAGER</varname></term>

        <listitem>
          <para>Pager to use when <option>--no-pager</option> is not
          given; overrides <varname>$PAGER</varname>.  Setting this to
          an empty string or the value <literal>cat</literal> is
          equivalent to passing
          <option>--no-pager</option>.</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemadm</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.resource-management</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>wall</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.preset</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>