man/systemd.kill.xml

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   5
   6 <refentry id="systemd.kill" xmlns:xi="http://www.w3.org/2001/XInclude">
   7   <refentryinfo>
   8     <title>systemd.kill</title>
   9     <productname>systemd</productname>
  10   </refentryinfo>
  11
  12   <refmeta>
  13     <refentrytitle>systemd.kill</refentrytitle>
  14     <manvolnum>5</manvolnum>
  15   </refmeta>
  16
  17   <refnamediv>
  18     <refname>systemd.kill</refname>
  19     <refpurpose>Process killing procedure
  20     configuration</refpurpose>
  21   </refnamediv>
  22
  23   <refsynopsisdiv>
  24     <para><filename><replaceable>service</replaceable>.service</filename>,
  25     <filename><replaceable>socket</replaceable>.socket</filename>,
  26     <filename><replaceable>mount</replaceable>.mount</filename>,
  27     <filename><replaceable>swap</replaceable>.swap</filename>,
  28     <filename><replaceable>scope</replaceable>.scope</filename></para>
  29   </refsynopsisdiv>
  30
  31   <refsect1>
  32     <title>Description</title>
  33
  34     <para>Unit configuration files for services, sockets, mount
  35     points, swap devices and scopes share a subset of configuration
  36     options which define the killing procedure of processes belonging
  37     to the unit.</para>
  38
  39     <para>This man page lists the configuration options shared by
  40     these five unit types. See
  41     <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  42     for the common options shared by all unit configuration files, and
  43     <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  44     <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  45     <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  46     <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  47     and
  48     <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  49     for more information on the configuration file options specific to
  50     each unit type.</para>
  51
  52     <para>The kill procedure configuration options are configured in
  53     the [Service], [Socket], [Mount] or [Swap] section, depending on
  54     the unit type.</para>
  55   </refsect1>
  56
  57   <refsect1>
  58     <title>Options</title>
  59
  60     <variablelist class='unit-directives'>
  61
  62       <varlistentry>
  63         <term><varname>KillMode=</varname></term>
  64         <listitem><para>Specifies how processes of this unit shall be killed. One of
  65         <option>control-group</option>, <option>mixed</option>, <option>process</option>,
  66         <option>none</option>.</para>
  67
  68         <para>If set to <option>control-group</option>, all remaining processes in the control group of this
  69         unit will be killed on unit stop (for services: after the stop command is executed, as configured
  70         with <varname>ExecStop=</varname>). If set to <option>mixed</option>, the
  71         <constant>SIGTERM</constant> signal (see below) is sent to the main process while the subsequent
  72         <constant>SIGKILL</constant> signal (see below) is sent to all remaining processes of the unit's
  73         control group. If set to <option>process</option>, only the main process itself is killed (not
  74         recommended!). If set to <option>none</option>, no process is killed (strongly recommended
  75         against!). In this case, only the stop command will be executed on unit stop, but no process will be
  76         killed otherwise.  Processes remaining alive after stop are left in their control group and the
  77         control group continues to exist after stop unless empty.</para>
  78
  79         <para>Note that it is not recommended to set <varname>KillMode=</varname> to
  80         <constant>process</constant> or even <constant>none</constant>, as this allows processes to escape
  81         the service manager's lifecycle and resource management, and to remain running even while their
  82         service is considered stopped and is assumed to not consume any resources.</para>
  83
  84         <para>Processes will first be terminated via <constant>SIGTERM</constant> (unless the signal to send
  85         is changed via <varname>KillSignal=</varname> or <varname>RestartKillSignal=</varname>). Optionally,
  86         this is immediately followed by a <constant>SIGHUP</constant> (if enabled with
  87         <varname>SendSIGHUP=</varname>). If processes still remain after:
  88         <itemizedlist>
  89           <listitem><para>the main process of a unit has exited (applies to <varname>KillMode=</varname>:
  90               <option>mixed</option>)</para></listitem>
  91           <listitem><para>the delay configured via the <varname>TimeoutStopSec=</varname> has passed
  92               (applies to <varname>KillMode=</varname>: <option>control-group</option>, <option>mixed</option>,
  93               <option>process</option>)</para></listitem>
  94         </itemizedlist>
  95
  96         the termination request is repeated with the <constant>SIGKILL</constant> signal or the signal specified via
  97         <varname>FinalKillSignal=</varname> (unless this is disabled via the <varname>SendSIGKILL=</varname>
  98         option). See <citerefentry><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry>
  99         for more information.</para>
 100
 101         <para>Defaults to <option>control-group</option>.</para>
 102
 103         <xi:include href="version-info.xml" xpointer="v187"/></listitem>
 104       </varlistentry>
 105
 106       <varlistentry>
 107         <term><varname>KillSignal=</varname></term>
 108         <listitem><para>Specifies which signal to use when stopping a service. This controls the signal that
 109         is sent as first step of shutting down a unit (see above), and is usually followed by
 110         <constant>SIGKILL</constant> (see above and below). For a list of valid signals, see
 111         <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
 112         Defaults to <constant>SIGTERM</constant>.</para>
 113
 114         <para>Note that, right after sending the signal specified in this setting, systemd will always send
 115         <constant>SIGCONT</constant>, to ensure that even suspended tasks can be terminated cleanly.</para>
 116
 117         <xi:include href="version-info.xml" xpointer="v187"/>
 118         </listitem>
 119       </varlistentry>
 120
 121       <varlistentry>
 122         <term><varname>RestartKillSignal=</varname></term>
 123         <listitem><para>Specifies which signal to use when restarting a service. The same as
 124         <varname>KillSignal=</varname> described above, with the exception that this setting is used in a
 125         restart job. Not set by default, and the value of <varname>KillSignal=</varname> is used.</para>
 126
 127         <xi:include href="version-info.xml" xpointer="v244"/>
 128         </listitem>
 129       </varlistentry>
 130
 131       <varlistentry>
 132         <term><varname>SendSIGHUP=</varname></term>
 133         <listitem><para>Specifies whether to send
 134         <constant>SIGHUP</constant> to remaining processes immediately
 135         after sending the signal configured with
 136         <varname>KillSignal=</varname>. This is useful to indicate to
 137         shells and shell-like programs that their connection has been
 138         severed. Takes a boolean value. Defaults to <literal>no</literal>.
 139         </para>
 140
 141         <xi:include href="version-info.xml" xpointer="v207"/></listitem>
 142       </varlistentry>
 143
 144       <varlistentry>
 145         <term><varname>SendSIGKILL=</varname></term>
 146         <listitem><para>Specifies whether to send
 147         <constant>SIGKILL</constant> (or the signal specified by
 148         <varname>FinalKillSignal=</varname>) to remaining processes
 149         after a timeout, if the normal shutdown procedure left
 150         processes of the service around. When disabled, a
 151         <varname>KillMode=</varname> of <constant>control-group</constant>
 152         or <constant>mixed</constant> service will not restart if
 153         processes from prior services exist within the control group.
 154         Takes a boolean value. Defaults to <literal>yes</literal>.
 155         </para>
 156
 157         <xi:include href="version-info.xml" xpointer="v187"/></listitem>
 158       </varlistentry>
 159
 160       <varlistentry>
 161         <term><varname>FinalKillSignal=</varname></term>
 162         <listitem><para>Specifies which signal to send to remaining
 163         processes after a timeout if <varname>SendSIGKILL=</varname>
 164         is enabled. The signal configured here should be one that is
 165         not typically caught and processed by services (<constant>SIGTERM</constant>
 166         is not suitable). Developers can find it useful to use this to
 167         generate a coredump to troubleshoot why a service did not
 168         terminate upon receiving the initial <constant>SIGTERM</constant>
 169         signal. This can be achieved by configuring <varname>LimitCORE=</varname>
 170         and setting <varname>FinalKillSignal=</varname> to either
 171         <constant>SIGQUIT</constant> or <constant>SIGABRT</constant>.
 172         Defaults to <constant>SIGKILL</constant>.
 173         </para>
 174
 175         <xi:include href="version-info.xml" xpointer="v240"/></listitem>
 176       </varlistentry>
 177
 178       <varlistentry>
 179         <term><varname>WatchdogSignal=</varname></term>
 180         <listitem><para>Specifies which signal to use to terminate the
 181         service when the watchdog timeout expires (enabled through
 182         <varname>WatchdogSec=</varname>). Defaults to <constant>SIGABRT</constant>.
 183         </para>
 184
 185         <xi:include href="version-info.xml" xpointer="v240"/></listitem>
 186       </varlistentry>
 187
 188     </variablelist>
 189   </refsect1>
 190
 191   <refsect1>
 192       <title>See Also</title>
 193       <para><simplelist type="inline">
 194         <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 195         <member><citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 196         <member><citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 197         <member><citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 198         <member><citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 199         <member><citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 200         <member><citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 201         <member><citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 202         <member><citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 203         <member><citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 204         <member><citerefentry><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry></member>
 205         <member><citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 206       </simplelist></para>
 207   </refsect1>
 208
 209 </refentry>