kernel-install: add default install scripts

[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>, or unit load states such as
          <option>loaded</option> and <option>masked</option>
          (types and states can be mixed).</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>If one of the arguments is a unit load state, when
          listing units, limit display to certain unit
          types. Otherwise units of in all load states 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>-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, resp. before
          with <command>list-dependencies</command>.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--failed</option></term>

        <listitem>
          <para>When listing units, show only failed units. Do not
          confuse with <option>--fail</option>.</para>
        </listitem>
      </varlistentry>

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

        <listitem>
          <para>Do not ellipsize unit names, cgroup members, and
          truncate unit descriptions in the output of
          <command>list-units</command> and
          <command>list-jobs</command>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--fail</option></term>

        <listitem>
          <para>If the requested operation conflicts with a pending
          unfinished job, fail the command. If this is not specified
          the requested operation will replace the pending job, if
          necessary. Do not confuse with
          <option>--failed</option>.</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>--irreversible</option></term>

        <listitem>
          <para>Mark this transaction's 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>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--ignore-dependencies</option></term>

        <listitem>
          <para>When enqueuing a new job ignore all its dependencies
          and execute it 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>
        </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 if 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 a 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>Don't 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 SIGTERM, SIGINT or
          SIGSTOP. 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>, <command>is-enabled</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>Similar, when used with
          <command>set-cgroup-attr</command>,
          <command>unset-cgroup-attr</command>,
          <command>set-cgroup</command> and
          <command>unset-cgroup</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 operation remotely. Specify a hostname, or
          username and hostname separated by @, to connect to. This
          will use SSH to talk to the remote systemd
          instance.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-P</option></term>
        <term><option>--privileged</option></term>

        <listitem>
          <para>Acquire privileges via PolicyKit before executing the
          operation.</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>

    <variablelist>
      <varlistentry>
        <term><command>list-units</command></term>

        <listitem>
          <para>List known units (subject to limitations specified
          with <option>-t</option>).</para>

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

      <varlistentry>
        <term><command>list-sockets</command></term>

        <listitem>
          <para>List socket units ordered by the listening address. 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 programatic consumption.
          </para>

          <para>See also the options <option>--show-types</option>,
          <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. Do 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. Do 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, 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 failed.
          Returns an exit code 0 if at least one is 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 [<replaceable>NAME</replaceable>...|<replaceable>PID</replaceable>...]</command></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.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><command>show [<replaceable>NAME</replaceable>...|<replaceable>JOB</replaceable>...]</command></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>get-cgroup-attr <replaceable>NAME</replaceable> <replaceable>ATTRIBUTE</replaceable>...</command></term>

        <listitem>
          <para>Retrieve the specified control group attributes of the
          specified unit. Takes a unit name and one or more attribute
          names such as <literal>cpu.shares</literal>. This will
          output the current values of the specified attributes,
          separated by new-lines. For attributes that take list of
          items the output will be new-line separated, too. This
          operation will always try to retrieve the data in question
          from the kernel first, and if that is not available use the
          configured values instead. Instead of low-level control
          group attribute names high-level pretty names may be used,
          as used for unit execution environment configuration, see
          <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
          for details. For example, passing
          <literal>memory.limit_in_bytes</literal> and
          <literal>MemoryLimit</literal> is equivalent.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><command>set-cgroup-attr <replaceable>NAME</replaceable> <replaceable>ATTRIBUTE</replaceable> <replaceable>VALUE</replaceable>...</command></term>

        <listitem>
          <para>Set the specified control group attribute of the
          specified unit to the specified value. Takes a unit
          name and an attribute name such as
          <literal>cpu.shares</literal>, plus one or more values
          (multiple values may only be used for attributes that take
          multiple values). This operation will immediately update the
          kernel attribute for this unit and persistently store this
          setting for later reboots (unless <option>--runtime</option>
          is passed, in which case the setting is not saved
          persistently and only valid until the next reboot.) Instead
          of low-level control group attribute names high-level pretty
          names may be used, as used for unit execution environment
          configuration, see
          <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
          for details. For example, passing
          <literal>memory.limit_in_bytes</literal> and
          <literal>MemoryLimit</literal> is equivalent. This operation
          will implicitly create a control group for the unit in the
          controller the attribute belongs to, if needed. For
          attributes that take multiple values, this operation will
          append the specified values to the previously set values
          list (use <command>unset-cgroup-attr</command> to reset the
          list explicitly). For attributes that take a single value
          only the list will be reset implicitly.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><command>unset-cgroup-attr <replaceable>NAME</replaceable> <replaceable>ATTRIBUTE</replaceable>...</command></term>

        <listitem><para>Unset the specified control group attributes
        of the specified unit. Takes a unit name and one or more
        attribut names such as <literal>cpu.shares</literal>. This
        operation might or might not have an immediate effect on the
        current kernel attribute value. This will remove any
        persistently stored configuration values for this attribute
        (as set with <command>set-cgroup-attr</command> before),
        unless <option>--runtime</option> is passed, in which case the
        configuration is reset only until the next reboot. Again,
        high-level control group attributes may be used instead of the
        low-level kernel ones. For attributes which take multiple
        values, all currently set values are reset.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><command>set-cgroup <replaceable>NAME</replaceable> <replaceable>CGROUP</replaceable>...</command></term>
        <term><command>unset-cgroup <replaceable>NAME</replaceable> <replaceable>CGROUP</replaceable>...</command></term>

        <listitem><para>Add or remove a unit to/from a specific
        control group hierarchy and/or control group path. Takes a
        unit name, plus a control group specification in the syntax
        <replaceable>CONTROLLER</replaceable>:<replaceable>PATH</replaceable>
        or <replaceable>CONTROLLER</replaceable>. In the latter syntax
        (where the path is omitted) the default unit control group
        path is implied. Examples: <literal>cpu</literal> or
        <literal>cpu:/foo/bar</literal>. If a unit is removed from a
        control group hierarchy all its processes will be moved to the
        root group of the hierarchy and all control group attributes
        will be reset. These operations are immediately reflected in
        the kernel hierarchy, and stored persistently to disk (unless
        <option>--runtime</option> is passed).</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 passed the manual pages for the unit
          the process of the PID belongs to is
          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 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-unit-files</command></term>

        <listitem>
          <para>List installed unit files.</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 not have the effect that any of the units enabled
          are also started at the same time. 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 same as instances are created in 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 his 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> or <option>--global</option> is
          specified this enables the unit for the system, for the
          calling user only or for all future logins of all
          users. 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>--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. To suppress
          this output use <option>--quiet</option>.</para>
        </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 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.</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
          isn't installed directly in the unit search path.</para>
        </listitem>
      </varlistentry>

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

        <listitem>
          <para>Load one or more units specified on the command
          line. This will simply load their configuration from disk,
          but not start them. To start them you need to use the
          <command>start</command> command which will implicitly load
          a unit that has not been loaded yet. Note that systemd
          garbage collects loaded units that are not active or
          referenced by an active unit. This means that units loaded
          this way will usually not stay loaded for long. Also note
          that this command cannot be used to reload unit
          configuration. Use the <command>daemon-reload</command>
          command for that. All in all, this command is of little use
          except for debugging.</para>

          <para>This command should not be confused with the
          <command>daemon-reload</command> or
          <command>reload</command>.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><command>list-jobs</command></term>

        <listitem>
          <para>List jobs that are in progress.</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>
      <varlistentry>
        <term><command>dump</command></term>

        <listitem>
          <para>Dump server status. This will output a (usually very
          long) human readable manager status dump. Its format is
          subject to change without notice and should not be parsed by
          applications.</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>
      <varlistentry>
        <term><command>snapshot [<replaceable>NAME</replaceable>]</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>
      <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 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 reexecuted all sockets systemd listens
          on on behalf of user configuration will stay accessible.
          </para>
        </listitem>
      </varlistentry>
      <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>
      <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</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>
        </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> [<replaceable>INIT</replaceable>]</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. Takes two
          arguments: the directory to make 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>

  </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.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>