man/systemd.kill.xml

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   5
   6 <refentry id="systemd.kill">
   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></listitem>
 102       </varlistentry>
 103
 104       <varlistentry>
 105         <term><varname>KillSignal=</varname></term>
 106         <listitem><para>Specifies which signal to use when stopping a service. This controls the signal that
 107         is sent as first step of shutting down a unit (see above), and is usually followed by
 108         <constant>SIGKILL</constant> (see above and below). For a list of valid signals, see
 109         <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
 110         Defaults to <constant>SIGTERM</constant>.</para>
 111
 112         <para>Note that, right after sending the signal specified in this setting, systemd will always send
 113         <constant>SIGCONT</constant>, to ensure that even suspended tasks can be terminated cleanly.</para>
 114         </listitem>
 115       </varlistentry>
 116
 117       <varlistentry>
 118         <term><varname>RestartKillSignal=</varname></term>
 119         <listitem><para>Specifies which signal to use when restarting a service. The same as
 120         <varname>KillSignal=</varname> described above, with the exception that this setting is used in a
 121         restart job. Not set by default, and the value of <varname>KillSignal=</varname> is used.</para>
 122         </listitem>
 123       </varlistentry>
 124
 125       <varlistentry>
 126         <term><varname>SendSIGHUP=</varname></term>
 127         <listitem><para>Specifies whether to send
 128         <constant>SIGHUP</constant> to remaining processes immediately
 129         after sending the signal configured with
 130         <varname>KillSignal=</varname>. This is useful to indicate to
 131         shells and shell-like programs that their connection has been
 132         severed. Takes a boolean value. Defaults to "no".
 133         </para></listitem>
 134       </varlistentry>
 135
 136       <varlistentry>
 137         <term><varname>SendSIGKILL=</varname></term>
 138         <listitem><para>Specifies whether to send
 139         <constant>SIGKILL</constant> (or the signal specified by
 140         <varname>FinalKillSignal=</varname>) to remaining processes
 141         after a timeout, if the normal shutdown procedure left
 142         processes of the service around. When disabled, a
 143         <varname>KillMode=</varname> of <constant>control-group</constant>
 144         or <constant>mixed</constant> service will not restart if
 145         processes from prior services exist within the control group.
 146         Takes a boolean value. Defaults to "yes".
 147         </para></listitem>
 148       </varlistentry>
 149
 150       <varlistentry>
 151         <term><varname>FinalKillSignal=</varname></term>
 152         <listitem><para>Specifies which signal to send to remaining
 153         processes after a timeout if <varname>SendSIGKILL=</varname>
 154         is enabled. The signal configured here should be one that is
 155         not typically caught and processed by services (<constant>SIGTERM</constant>
 156         is not suitable). Developers can find it useful to use this to
 157         generate a coredump to troubleshoot why a service did not
 158         terminate upon receiving the initial <constant>SIGTERM</constant>
 159         signal. This can be achieved by configuring <varname>LimitCORE=</varname>
 160         and setting <varname>FinalKillSignal=</varname> to either
 161         <constant>SIGQUIT</constant> or <constant>SIGABRT</constant>.
 162         Defaults to <constant>SIGKILL</constant>.
 163         </para></listitem>
 164       </varlistentry>
 165
 166       <varlistentry>
 167         <term><varname>WatchdogSignal=</varname></term>
 168         <listitem><para>Specifies which signal to use to terminate the
 169         service when the watchdog timeout expires (enabled through
 170         <varname>WatchdogSec=</varname>). Defaults to <constant>SIGABRT</constant>.
 171         </para></listitem>
 172       </varlistentry>
 173
 174     </variablelist>
 175   </refsect1>
 176
 177   <refsect1>
 178       <title>See Also</title>
 179       <para>
 180         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 181         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 182         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 183         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 184         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 185         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 186         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 187         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 188         <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 189         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 190         <citerefentry><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 191         <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 192       </para>
 193   </refsect1>
 194
 195 </refentry>