"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
+ SPDX-License-Identifier: LGPL-2.1+
+
This file is part of systemd.
Copyright 2010 Lennart Poettering
<title>Description</title>
<para>A unit configuration file whose name ends in
- <filename>.service</filename> encodes information about a process
+ <literal>.service</literal> encodes information about a process
controlled and supervised by systemd.</para>
<para>This man page lists the configuration options specific to
</refsect1>
<refsect1>
- <title>Automatic Dependencies</title>
-
- <para>Services with <varname>Type=dbus</varname> set automatically
- acquire dependencies of type <varname>Requires=</varname> and
- <varname>After=</varname> on
- <filename>dbus.socket</filename>.</para>
-
- <para>Socket activated services are automatically ordered after
- their activating <filename>.socket</filename> units via an
- automatic <varname>After=</varname> dependency.
- Services also pull in all <filename>.socket</filename> units
- listed in <varname>Sockets=</varname> via automatic
- <varname>Wants=</varname> and <varname>After=</varname> dependencies.</para>
-
- <para>Unless <varname>DefaultDependencies=</varname> in the <literal>[Unit]</literal> is set to
- <option>false</option>, service units will implicitly have dependencies of type <varname>Requires=</varname> and
- <varname>After=</varname> on <filename>sysinit.target</filename>, a dependency of type <varname>After=</varname> on
- <filename>basic.target</filename> as well as dependencies of type <varname>Conflicts=</varname> and
- <varname>Before=</varname> on <filename>shutdown.target</filename>. These ensure that normal service units pull in
- basic system initialization, and are terminated cleanly prior to system shutdown. Only services involved with early
- boot or late system shutdown should disable this option.</para>
-
- <para>Instanced service units (i.e. service units with an <literal>@</literal> in their name) are assigned by
- default a per-template slice unit (see
- <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>), named after the
- template unit, containing all instances of the specific template. This slice is normally stopped at shutdown,
- together with all template instances. If that is not desired, set <varname>DefaultDependencies=no</varname> in the
- template unit, and either define your own per-template slice unit file that also sets
- <varname>DefaultDependencies=no</varname>, or set <varname>Slice=system.slice</varname> (or another suitable slice)
- in the template unit. Also see
- <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+ <title>Implicit Dependencies</title>
+
+ <para>The following dependencies are implicitly added:</para>
+
+ <itemizedlist>
+ <listitem><para>Services with <varname>Type=dbus</varname> set automatically
+ acquire dependencies of type <varname>Requires=</varname> and
+ <varname>After=</varname> on
+ <filename>dbus.socket</filename>.</para></listitem>
+
+ <listitem><para>Socket activated services are automatically ordered after
+ their activating <filename>.socket</filename> units via an
+ automatic <varname>After=</varname> dependency.
+ Services also pull in all <filename>.socket</filename> units
+ listed in <varname>Sockets=</varname> via automatic
+ <varname>Wants=</varname> and <varname>After=</varname> dependencies.</para></listitem>
+ </itemizedlist>
<para>Additional implicit dependencies may be added as result of
execution and resource control parameters as documented in
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
</refsect1>
+ <refsect1>
+ <title>Default Dependencies</title>
+
+ <para>The following dependencies are added unless <varname>DefaultDependencies=no</varname> is set:</para>
+
+ <itemizedlist>
+ <listitem><para>Service units will have dependencies of type <varname>Requires=</varname> and
+ <varname>After=</varname> on <filename>sysinit.target</filename>, a dependency of type <varname>After=</varname> on
+ <filename>basic.target</filename> as well as dependencies of type <varname>Conflicts=</varname> and
+ <varname>Before=</varname> on <filename>shutdown.target</filename>. These ensure that normal service units pull in
+ basic system initialization, and are terminated cleanly prior to system shutdown. Only services involved with early
+ boot or late system shutdown should disable this option.</para></listitem>
+
+ <listitem><para>Instanced service units (i.e. service units with an <literal>@</literal> in their name) are assigned by
+ default a per-template slice unit (see
+ <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>), named after the
+ template unit, containing all instances of the specific template. This slice is normally stopped at shutdown,
+ together with all template instances. If that is not desired, set <varname>DefaultDependencies=no</varname> in the
+ template unit, and either define your own per-template slice unit file that also sets
+ <varname>DefaultDependencies=no</varname>, or set <varname>Slice=system.slice</varname> (or another suitable slice)
+ in the template unit. Also see
+ <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ </para></listitem>
+ </itemizedlist>
+ </refsect1>
+
<refsect1>
<title>Options</title>
<varname>PrivateNetwork=</varname><option>yes</option>.</para>
<para>Behavior of <option>idle</option> is very similar to <option>simple</option>; however, actual execution
- of the service binary is delayed until all active jobs are dispatched. This may be used to avoid interleaving
+ of the service program is delayed until all active jobs are dispatched. This may be used to avoid interleaving
of output of shell services with the status output on the console. Note that this type is useful only to
improve console output, it is not useful as a general unit ordering tool, and the effect of this service type
- is subject to a 5s time-out, after which the service binary is invoked anyway.</para>
+ is subject to a 5s time-out, after which the service program is invoked anyway.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>PIDFile=</varname></term>
- <listitem><para>Takes an absolute file name pointing to the
- PID file of this daemon. Use of this option is recommended for
- services where <varname>Type=</varname> is set to
- <option>forking</option>. systemd will read the PID of the
- main process of the daemon after start-up of the service.
- systemd will not write to the file configured here, although
- it will remove the file after the service has shut down if it
- still exists.
- </para>
- </listitem>
+ <listitem><para>Takes an absolute path referring to the PID file of the service. Usage of this option is
+ recommended for services where <varname>Type=</varname> is set to <option>forking</option>. The service manager
+ will read the PID of the main process of the service from this file after start-up of the service. The service
+ manager will not write to the file configured here, although it will remove the file after the service has shut
+ down if it still exists. The PID file does not need to be owned by a privileged user, but if it is owned by an
+ unprivileged user additional safety restrictions are enforced: the file may not be a symlink to a file owned by
+ a different user (neither directly nor indirectly), and the PID file must refer to a process already belonging
+ to the service.</para></listitem>
</varlistentry>
<varlistentry>
<varname>ExecStop=</varname> are not valid.)</para>
<para>For each of the specified commands, the first argument must be an absolute path to an
- executable. Optionally, if this file name is prefixed with <literal>@</literal>, the second token will be
- passed as <literal>argv[0]</literal> to the executed process, followed by the further arguments specified. If
- the absolute filename is prefixed with <literal>-</literal>, an exit code of the command normally considered a
- failure (i.e. non-zero exit status or abnormal exit due to signal) is ignored and considered success. If the
- absolute path is prefixed with <literal>+</literal> then it is executed with full
- privileges. <literal>@</literal>, <literal>-</literal>, and <literal>+</literal> may be used together and they
- can appear in any order.</para>
+ executable. Optionally, this filename may be prefixed with a number of special characters:</para>
+
+ <table>
+ <title>Special executable prefixes</title>
+
+ <tgroup cols='2'>
+ <colspec colname='prefix'/>
+ <colspec colname='meaning'/>
+
+ <thead>
+ <row>
+ <entry>Prefix</entry>
+ <entry>Effect</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry><literal>@</literal></entry>
+ <entry>If the executable path is prefixed with <literal>@</literal>, the second specified token will be passed as <literal>argv[0]</literal> to the executed process (instead of the actual filename), followed by the further arguments specified.</entry>
+ </row>
+
+ <row>
+ <entry><literal>-</literal></entry>
+ <entry>If the executable path is prefixed with <literal>-</literal>, an exit code of the command normally considered a failure (i.e. non-zero exit status or abnormal exit due to signal) is ignored and considered success.</entry>
+ </row>
+
+ <row>
+ <entry><literal>+</literal></entry>
+ <entry>If the executable path is prefixed with <literal>+</literal> then the process is executed with full privileges. In this mode privilege restrictions configured with <varname>User=</varname>, <varname>Group=</varname>, <varname>CapabilityBoundingSet=</varname> or the various file system namespacing options (such as <varname>PrivateDevices=</varname>, <varname>PrivateTmp=</varname>) are not applied to the invoked command line (but still affect any other <varname>ExecStart=</varname>, <varname>ExecStop=</varname>, … lines).</entry>
+ </row>
+
+ <row>
+ <entry><literal>!</literal></entry>
+
+ <entry>Similar to the <literal>+</literal> character discussed above this permits invoking command lines with elevated privileges. However, unlike <literal>+</literal> the <literal>!</literal> character exclusively alters the effect of <varname>User=</varname>, <varname>Group=</varname> and <varname>SupplementaryGroups=</varname>, i.e. only the stanzas the affect user and group credentials. Note that this setting may be combined with <varname>DynamicUser=</varname>, in which case a dynamic user/group pair is allocated before the command is invoked, but credential changing is left to the executed process itself.</entry>
+ </row>
+
+ <row>
+ <entry><literal>!!</literal></entry>
+
+ <entry>This prefix is very similar to <literal>!</literal>, however it only has an effect on systems lacking support for ambient process capabilities, i.e. without support for <varname>AmbientCapabilities=</varname>. It's intended to be used for unit files that take benefit of ambient capabilities to run processes with minimal privileges wherever possible while remaining compatible with systems that lack ambient capabilities support. Note that when <literal>!!</literal> is used, and a system lacking ambient capability support is detected any configured <varname>SystemCallFilter=</varname> and <varname>CapabilityBoundingSet=</varname> stanzas are implicitly modified, in order to permit spawned processes to drop credentials and capabilities themselves, even if this is configured to not be allowed. Moreover, if this prefix is used and a system lacking ambient capability support is detected <varname>AmbientCapabilities=</varname> will be skipped and not be applied. On systems supporting ambient capabilities, <literal>!!</literal> has no effect and is redundant.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <para><literal>@</literal>, <literal>-</literal>, and one of
+ <literal>+</literal>/<literal>!</literal>/<literal>!!</literal> may be used together and they can appear in any
+ order. However, only one of <literal>+</literal>, <literal>!</literal>, <literal>!!</literal> may be used at a
+ time. Note that these prefixes are also supported for the other command line settings,
+ i.e. <varname>ExecStartPre=</varname>, <varname>ExecStartPost=</varname>, <varname>ExecReload=</varname>,
+ <varname>ExecStop=</varname> and <varname>ExecStopPost=</varname>.</para>
<para>If more than one command is specified, the commands are
invoked sequentially in the order they appear in the unit
start-up failed, for example because any of the commands specified in <varname>ExecStart=</varname>,
<varname>ExecStartPre=</varname> or <varname>ExecStartPost=</varname> failed (and weren't prefixed with
<literal>-</literal>, see above) or timed out. Use <varname>ExecStopPost=</varname> to invoke commands when a
- service failed to start up correctly and is shut down again.</para>
+ service failed to start up correctly and is shut down again. Also note that, service restart requests are
+ implemented as stop operations followed by start operations. This means that <varname>ExecStop=</varname> and
+ <varname>ExecStopPost=</varname> are executed during a service restart operation.</para>
<para>It is recommended to use this setting for commands that communicate with the service requesting clean
termination. When the commands specified with this option are executed it should be assumed that the service is
<varname>Type=oneshot</varname> is used, in which case the
timeout is disabled by default (see
<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
+ </para>
+
+ <para>If a service of <varname>Type=notify</varname> sends <literal>EXTEND_TIMEOUT_USEC=…</literal>, this may cause
+ the start time to be extended beyond <varname>TimeoutStartSec=</varname>. The first receipt of this message
+ must occur before <varname>TimeoutStartSec=</varname> is exceeded, and once the start time has exended beyond
+ <varname>TimeoutStartSec=</varname>, the service manager will allow the service to continue to start, provided
+ the service repeats <literal>EXTEND_TIMEOUT_USEC=…</literal> within the interval specified until the service
+ startup status is finished by <literal>READY=1</literal>. (see
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>).
</para></listitem>
</varlistentry>
<varname>DefaultTimeoutStopSec=</varname> from the manager
configuration file (see
<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
+ </para>
+
+ <para>If a service of <varname>Type=notify</varname> sends <literal>EXTEND_TIMEOUT_USEC=…</literal>, this may cause
+ the stop time to be extended beyond <varname>TimeoutStopSec=</varname>. The first receipt of this message
+ must occur before <varname>TimeoutStopSec=</varname> is exceeded, and once the stop time has exended beyond
+ <varname>TimeoutStopSec=</varname>, the service manager will allow the service to continue to stop, provided
+ the service repeats <literal>EXTEND_TIMEOUT_USEC=…</literal> within the interval specified, or terminates itself
+ (see <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>).
</para></listitem>
</varlistentry>
active for longer than the specified time it is terminated and put into a failure state. Note that this setting
does not have any effect on <varname>Type=oneshot</varname> services, as they terminate immediately after
activation completed. Pass <literal>infinity</literal> (the default) to configure no runtime
- limit.</para></listitem>
+ limit.</para>
+
+ <para>If a service of <varname>Type=notify</varname> sends <literal>EXTEND_TIMEOUT_USEC=…</literal>, this may cause
+ the runtime to be extended beyond <varname>RuntimeMaxSec=</varname>. The first receipt of this message
+ must occur before <varname>RuntimeMaxSec=</varname> is exceeded, and once the runtime has exended beyond
+ <varname>RuntimeMaxSec=</varname>, the service manager will allow the service to continue to run, provided
+ the service repeats <literal>EXTEND_TIMEOUT_USEC=…</literal> within the interval specified until the service
+ shutdown is acheived by <literal>STOPPING=1</literal> (or termination). (see
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>).
+ </para></listitem>
</varlistentry>
<varlistentry>
limiting configured with <varname>StartLimitIntervalSec=</varname>
and <varname>StartLimitBurst=</varname>, see
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- for details.</para>
+ for details. A restarted service enters the failed state only
+ after the start limits are reached.</para>
<para>Setting this to <option>on-failure</option> is the
recommended choice for long-running services, in order to
considered clean service terminations.
</para>
- <para>Note that if a process has a signal handler installed
- and exits by calling
- <citerefentry><refentrytitle>_exit</refentrytitle><manvolnum>2</manvolnum></citerefentry>
- in response to a signal, the information about the signal is
- lost. Programs should instead perform cleanup and kill
- themselves with the same signal instead. See
- <ulink url="http://www.cons.org/cracauer/sigint.html">Proper
- handling of SIGINT/SIGQUIT — How to be a proper
- program</ulink>.</para>
-
<para>This option may appear more than once, in which case the
list of successful exit statuses is merged. If the empty
string is assigned to this option, the list is reset, all
effect.</para></listitem>
</varlistentry>
- <varlistentry>
- <term><varname>FailureAction=</varname></term>
- <listitem><para>Configure the action to take when the service enters a failed state. Takes the same values as
- the unit setting <varname>StartLimitAction=</varname> and executes the same actions (see
- <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>). Defaults to
- <option>none</option>. </para></listitem>
- </varlistentry>
-
<varlistentry>
<term><varname>FileDescriptorStoreMax=</varname></term>
<listitem><para>Configure how many file descriptors may be stored in the service manager for the service using
<para>Each command line is split on whitespace, with the first item being the command to
execute, and the subsequent items being the arguments. Double quotes ("…") and single quotes
- ('…') may be used, in which case everything until the next matching quote becomes part of the
- same argument. Quotes themselves are removed. C-style escapes are also supported. The table
- below contains the list of known escape patterns. Only escape patterns which match the syntax in
- the table are allowed; other patterns may be added in the future and unknown patterns will
- result in a warning. In particular, any backslashes should be doubled. Finally, a trailing
- backslash (<literal>\</literal>) may be used to merge lines.</para>
+ ('…') may be used to wrap a whole item (the opening quote may appear only at the beginning or
+ after whitespace that is not quoted, and the closing quote must be followed by whitespace or the
+ end of line), in which case everything until the next matching quote becomes part of the same
+ argument. Quotes themselves are removed. C-style escapes are also supported. The table below
+ contains the list of known escape patterns. Only escape patterns which match the syntax in the
+ table are allowed; other patterns may be added in the future and unknown patterns will result in
+ a warning. In particular, any backslashes should be doubled. Finally, a trailing backslash
+ (<literal>\</literal>) may be used to merge lines.</para>
<para>This syntax is inspired by shell syntax, but only the meta-characters and expansions
described in the following paragraphs are understood, and the expansion of variables is
<para>The command line accepts <literal>%</literal> specifiers as
described in
- <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
- Note that the first argument of the command line (i.e. the program
- to execute) may not include specifiers.</para>
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
<para>Basic environment variable substitution is supported. Use
<literal>${FOO}</literal> as part of a word, or as a word of its
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