man/systemd.kill.xml

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<refentry id="systemd.kill">
  <refentryinfo>
    <title>systemd.kill</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd.kill</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd.kill</refname>
    <refpurpose>Process killing procedure
    configuration</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename><replaceable>service</replaceable>.service</filename>,
    <filename><replaceable>socket</replaceable>.socket</filename>,
    <filename><replaceable>mount</replaceable>.mount</filename>,
    <filename><replaceable>swap</replaceable>.swap</filename>,
    <filename><replaceable>scope</replaceable>.scope</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>Unit configuration files for services, sockets, mount
    points, swap devices and scopes share a subset of configuration
    options which define the killing procedure of processes belonging
    to the unit.</para>

    <para>This man page lists the configuration options shared by
    these five unit types. See
    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for the common options shared by all unit configuration files, and
    <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    and
    <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for more information on the configuration file options specific to
    each unit type.</para>

    <para>The kill procedure configuration options are configured in
    the [Service], [Socket], [Mount] or [Swap] section, depending on
    the unit type.</para>
  </refsect1>

  <refsect1>
    <title>Options</title>

    <variablelist class='unit-directives'>

      <varlistentry>
        <term><varname>KillMode=</varname></term>
        <listitem><para>Specifies how processes of this unit shall be
        killed. One of
        <option>control-group</option>,
        <option>process</option>,
        <option>mixed</option>,
        <option>none</option>.</para>

        <para>If set to <option>control-group</option>, all remaining
        processes in the control group of this unit will be killed on
        unit stop (for services: after the stop command is executed,
        as configured with <varname>ExecStop=</varname>). If set to
        <option>process</option>, only the main process itself is
        killed. If set to <option>mixed</option>, the
        <constant>SIGTERM</constant> signal (see below) is sent to the
        main process while the subsequent <constant>SIGKILL</constant>
        signal (see below) is sent to all remaining processes of the
        unit's control group. If set to <option>none</option>, no
        process is killed. In this case, only the stop command will be
        executed on unit stop, but no process will be killed otherwise.
        Processes remaining alive after stop are left in their control
        group and the control group continues to exist after stop
        unless it is empty.</para>

        <para>Processes will first be terminated via <constant>SIGTERM</constant> (unless the signal to send
        is changed via <varname>KillSignal=</varname>). Optionally, this is immediately followed by a
        <constant>SIGHUP</constant> (if enabled with <varname>SendSIGHUP=</varname>). If processes still
        remain after the main process of a unit has exited or the delay configured via the
        <varname>TimeoutStopSec=</varname> has passed, the termination request is repeated with the
        <constant>SIGKILL</constant> signal or the signal specified via <varname>FinalKillSignal=</varname>
        (unless this is disabled via the <varname>SendSIGKILL=</varname> option). See
        <citerefentry><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry> for more
        information.</para>

        <para>Defaults to <option>control-group</option>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>KillSignal=</varname></term>
        <listitem><para>Specifies which signal to use when killing a
        service. This controls the signal that is sent as first step
        of shutting down a unit (see above), and is usually followed
        by <constant>SIGKILL</constant> (see above and below). For a
        list of valid signals, see
        <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
        Defaults to <constant>SIGTERM</constant>. </para>

        <para>Note that, right after sending the signal specified in
        this setting, systemd will always send
        <constant>SIGCONT</constant>, to ensure that even suspended
        tasks can be terminated cleanly.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SendSIGHUP=</varname></term>
        <listitem><para>Specifies whether to send
        <constant>SIGHUP</constant> to remaining processes immediately
        after sending the signal configured with
        <varname>KillSignal=</varname>. This is useful to indicate to
        shells and shell-like programs that their connection has been
        severed. Takes a boolean value. Defaults to "no".
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SendSIGKILL=</varname></term>
        <listitem><para>Specifies whether to send
        <constant>SIGKILL</constant> (or the signal specified by
        <varname>FinalKillSignal=</varname>) to remaining processes
        after a timeout, if the normal shutdown procedure left
        processes of the service around. When disabled, a
        <varname>KillMode=</varname> of <constant>control-group</constant>
        or <constant>mixed</constant> service will not restart if
        processes from prior services exist within the control group.
        Takes a boolean value. Defaults to "yes".
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>FinalKillSignal=</varname></term>
        <listitem><para>Specifies which signal to send to remaining
        processes after a timeout if <varname>SendSIGKILL=</varname>
        is enabled. The signal configured here should be one that is
        not typically caught and processed by services (<constant>SIGTERM</constant>
        is not suitable). Developers can find it useful to use this to
        generate a coredump to troubleshoot why a service did not
        terminate upon receiving the initial <constant>SIGTERM</constant>
        signal. This can be achieved by configuring <varname>LimitCORE=</varname>
        and setting <varname>FinalKillSignal=</varname> to either
        <constant>SIGQUIT</constant> or <constant>SIGABRT</constant>
        Defaults to <constant>SIGKILL</constant>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>WatchdogSignal=</varname></term>
        <listitem><para>Specifies which signal to use to terminate the
        service when the watchdog timeout expires (enabled through
        <varname>WatchdogSec=</varname>). Defaults to <constant>SIGABRT</constant>.
        </para></listitem>
      </varlistentry>

    </variablelist>
  </refsect1>

  <refsect1>
      <title>See Also</title>
      <para>
        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
        <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>
      </para>
  </refsect1>

</refentry>