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systemd.service.xml
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systemd.service.xml
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<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="systemd.service">
<refentryinfo>
<title>systemd.service</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.service</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.service</refname>
<refpurpose>Service unit configuration</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename><replaceable>service</replaceable>.service</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>A unit configuration file whose name ends in
<literal>.service</literal> encodes information about a process
controlled and supervised by systemd.</para>
<para>This man page lists the configuration options specific to
this unit type. See
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for the common options of all unit configuration files. The common
configuration items are configured in the generic
<literal>[Unit]</literal> and <literal>[Install]</literal>
sections. The service specific configuration options are
configured in the <literal>[Service]</literal> section.</para>
<para>Additional options are listed in
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
which define the execution environment the commands are executed
in, and in
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
which define the way the processes of the service are terminated,
and in
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
which configure resource control settings for the processes of the
service.</para>
<para>If a service is requested under a certain name but no unit
configuration file is found, systemd looks for a SysV init script
by the same name (with the <filename>.service</filename> suffix
removed) and dynamically creates a service unit from that script.
This is useful for compatibility with SysV. Note that this
compatibility is quite comprehensive but not 100%. For details
about the incompatibilities, see the <ulink
url="https://www.freedesktop.org/wiki/Software/systemd/Incompatibilities">Incompatibilities
with SysV</ulink> document.</para>
<para>The <citerefentry><refentrytitle>systemd-run</refentrytitle><manvolnum>1</manvolnum></citerefentry>
command allows creating <filename>.service</filename> and <filename>.scope</filename> units dynamically
and transiently from the command line.</para>
</refsect1>
<refsect1>
<title>Service Templates</title>
<para>It is possible for <command>systemd</command> services to take a single argument via the
<literal><replaceable>service</replaceable>@<replaceable>argument</replaceable>.service</literal>
syntax. Such services are called "instantiated" services, while the unit definition without the
<replaceable>argument</replaceable> parameter is called a "template". An example could be a
<filename>dhcpcd@.service</filename> service template which takes a network interface as a
parameter to form an instantiated service. Within the service file, this parameter or "instance
name" can be accessed with %-specifiers. See
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details.</para>
</refsect1>
<refsect1>
<title>Automatic Dependencies</title>
<refsect2>
<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.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
</refsect2>
<refsect2>
<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>
</refsect2>
</refsect1>
<refsect1>
<title>Options</title>
<para>Service files must include a <literal>[Service]</literal>
section, which carries information about the service and the
process it supervises. A number of options that may be used in
this section are shared with other unit types. These options are
documented in
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
The options specific to the <literal>[Service]</literal> section
of service units are the following:</para>
<variablelist class='unit-directives'>
<varlistentry>
<term><varname>Type=</varname></term>
<listitem>
<para>Configures the process start-up type for this service unit. One of <option>simple</option>,
<option>exec</option>, <option>forking</option>, <option>oneshot</option>, <option>dbus</option>,
<option>notify</option> or <option>idle</option>:</para>
<itemizedlist>
<listitem><para>If set to <option>simple</option> (the default if <varname>ExecStart=</varname> is
specified but neither <varname>Type=</varname> nor <varname>BusName=</varname> are), the service manager
will consider the unit started immediately after the main service process has been forked off. It is
expected that the process configured with <varname>ExecStart=</varname> is the main process of the
service. In this mode, if the process offers functionality to other processes on the system, its
communication channels should be installed before the service is started up (e.g. sockets set up by
systemd, via socket activation), as the service manager will immediately proceed starting follow-up units,
right after creating the main service process, and before executing the service's binary. Note that this
means <command>systemctl start</command> command lines for <option>simple</option> services will report
success even if the service's binary cannot be invoked successfully (for example because the selected
<varname>User=</varname> doesn't exist, or the service binary is missing).</para></listitem>
<listitem><para>The <option>exec</option> type is similar to <option>simple</option>, but the service
manager will consider the unit started immediately after the main service binary has been executed. The service
manager will delay starting of follow-up units until that point. (Or in other words:
<option>simple</option> proceeds with further jobs right after <function>fork()</function> returns, while
<option>exec</option> will not proceed before both <function>fork()</function> and
<function>execve()</function> in the service process succeeded.) Note that this means <command>systemctl
start</command> command lines for <option>exec</option> services will report failure when the service's
binary cannot be invoked successfully (for example because the selected <varname>User=</varname> doesn't
exist, or the service binary is missing).</para></listitem>
<listitem><para>If set to <option>forking</option>, it is expected that the process configured with
<varname>ExecStart=</varname> will call <function>fork()</function> as part of its start-up. The parent
process is expected to exit when start-up is complete and all communication channels are set up. The child
continues to run as the main service process, and the service manager will consider the unit started when
the parent process exits. This is the behavior of traditional UNIX services. If this setting is used, it is
recommended to also use the <varname>PIDFile=</varname> option, so that systemd can reliably identify the
main process of the service. systemd will proceed with starting follow-up units as soon as the parent
process exits.</para></listitem>
<listitem><para>Behavior of <option>oneshot</option> is similar to <option>simple</option>;
however, the service manager will consider the unit up after the main process exits. It will then
start follow-up units. <varname>RemainAfterExit=</varname> is particularly useful for this type
of service. <varname>Type=</varname><option>oneshot</option> is the implied default if neither
<varname>Type=</varname> nor <varname>ExecStart=</varname> are specified. Note that if this
option is used without <varname>RemainAfterExit=</varname> the service will never enter
<literal>active</literal> unit state, but directly transition from <literal>activating</literal>
to <literal>deactivating</literal> or <literal>dead</literal> since no process is configured that
shall run continuously. In particular this means that after a service of this type ran (and which
has <varname>RemainAfterExit=</varname> not set) it will not show up as started afterwards, but
as dead.</para></listitem>
<listitem><para>Behavior of <option>dbus</option> is similar to <option>simple</option>; however, it is
expected that the service acquires a name on the D-Bus bus, as configured by
<varname>BusName=</varname>. systemd will proceed with starting follow-up units after the D-Bus bus name
has been acquired. Service units with this option configured implicitly gain dependencies on the
<filename>dbus.socket</filename> unit. This type is the default if <varname>BusName=</varname> is
specified.</para></listitem>
<listitem><para>Behavior of <option>notify</option> is similar to <option>exec</option>; however, it is
expected that the service sends a notification message via
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> or an
equivalent call when it has finished starting up. systemd will proceed with starting follow-up units after
this notification message has been sent. If this option is used, <varname>NotifyAccess=</varname> (see
below) should be set to open access to the notification socket provided by systemd. If
<varname>NotifyAccess=</varname> is missing or set to <option>none</option>, it will be forcibly set to
<option>main</option></para></listitem>.
<listitem><para>Behavior of <option>idle</option> is very similar to <option>simple</option>; however,
actual execution 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 timeout, after which the service program is invoked
anyway.</para></listitem>
</itemizedlist>
<para>It is generally recommended to use <varname>Type=</varname><option>simple</option> for long-running
services whenever possible, as it is the simplest and fastest option. However, as this service type won't
propagate service start-up failures and doesn't allow ordering of other units against completion of
initialization of the service (which for example is useful if clients need to connect to the service through
some form of IPC, and the IPC channel is only established by the service itself — in contrast to doing this
ahead of time through socket or bus activation or similar), it might not be sufficient for many cases. If so,
<option>notify</option> or <option>dbus</option> (the latter only in case the service provides a D-Bus
interface) are the preferred options as they allow service program code to precisely schedule when to
consider the service started up successfully and when to proceed with follow-up units. The
<option>notify</option> service type requires explicit support in the service codebase (as
<function>sd_notify()</function> or an equivalent API needs to be invoked by the service at the appropriate
time) — if it's not supported, then <option>forking</option> is an alternative: it supports the traditional
UNIX service start-up protocol. Finally, <option>exec</option> might be an option for cases where it is
enough to ensure the service binary is invoked, and where the service binary itself executes no or little
initialization on its own (and its initialization is unlikely to fail). Note that using any type other than
<option>simple</option> possibly delays the boot process, as the service manager needs to wait for service
initialization to complete. It is hence recommended not to needlessly use any types other than
<option>simple</option>. (Also note it is generally not recommended to use <option>idle</option> or
<option>oneshot</option> for long-running services.)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>RemainAfterExit=</varname></term>
<listitem><para>Takes a boolean value that specifies whether
the service shall be considered active even when all its
processes exited. Defaults to <option>no</option>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>GuessMainPID=</varname></term>
<listitem><para>Takes a boolean value that specifies whether
systemd should try to guess the main PID of a service if it
cannot be determined reliably. This option is ignored unless
<option>Type=forking</option> is set and
<option>PIDFile=</option> is unset because for the other types
or with an explicitly configured PID file, the main PID is
always known. The guessing algorithm might come to incorrect
conclusions if a daemon consists of more than one process. If
the main PID cannot be determined, failure detection and
automatic restarting of a service will not work reliably.
Defaults to <option>yes</option>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>PIDFile=</varname></term>
<listitem><para>Takes a 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 path specified typically points
to a file below <filename>/run/</filename>. If a relative path is specified it is hence prefixed with
<filename>/run/</filename>. 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>
<term><varname>BusName=</varname></term>
<listitem><para>Takes a D-Bus bus name that this service is
reachable as. This option is mandatory for services where
<varname>Type=</varname> is set to
<option>dbus</option>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ExecStart=</varname></term>
<listitem><para>Commands with their arguments that are
executed when this service is started. The value is split into
zero or more command lines according to the rules described
below (see section "Command Lines" below).
</para>
<para>Unless <varname>Type=</varname> is <option>oneshot</option>, exactly one command must be given. When
<varname>Type=oneshot</varname> is used, zero or more commands may be specified. Commands may be specified by
providing multiple command lines in the same directive, or alternatively, this directive may be specified more
than once with the same effect. If the empty string is assigned to this option, the list of commands to start
is reset, prior assignments of this option will have no effect. If no <varname>ExecStart=</varname> is
specified, then the service must have <varname>RemainAfterExit=yes</varname> and at least one
<varname>ExecStop=</varname> line set. (Services lacking both <varname>ExecStart=</varname> and
<varname>ExecStop=</varname> are not valid.)</para>
<para>For each of the specified commands, the first argument must be either an absolute path to an executable
or a simple file name without any slashes. 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 recorded, but has no further effect and is considered equivalent to success.</entry>
</row>
<row>
<entry><literal>:</literal></entry>
<entry>If the executable path is prefixed with <literal>:</literal>, environment variable substitution (as described by the "Command Lines" section below) is not applied.</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 that 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>, <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
file. If one of the commands fails (and is not prefixed with
<literal>-</literal>), other lines are not executed, and the
unit is considered failed.</para>
<para>Unless <varname>Type=forking</varname> is set, the
process started via this command line will be considered the
main process of the daemon.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ExecStartPre=</varname></term>
<term><varname>ExecStartPost=</varname></term>
<listitem><para>Additional commands that are executed before
or after the command in <varname>ExecStart=</varname>,
respectively. Syntax is the same as for
<varname>ExecStart=</varname>, except that multiple command
lines are allowed and the commands are executed one after the
other, serially.</para>
<para>If any of those commands (not prefixed with
<literal>-</literal>) fail, the rest are not executed and the
unit is considered failed.</para>
<para><varname>ExecStart=</varname> commands are only run after
all <varname>ExecStartPre=</varname> commands that were not prefixed
with a <literal>-</literal> exit successfully.</para>
<para><varname>ExecStartPost=</varname> commands are only run after the commands specified in
<varname>ExecStart=</varname> have been invoked successfully, as determined by <varname>Type=</varname>
(i.e. the process has been started for <varname>Type=simple</varname> or <varname>Type=idle</varname>, the last
<varname>ExecStart=</varname> process exited successfully for <varname>Type=oneshot</varname>, the initial
process exited successfully for <varname>Type=forking</varname>, <literal>READY=1</literal> is sent for
<varname>Type=notify</varname>, or the <varname>BusName=</varname> has been taken for
<varname>Type=dbus</varname>).</para>
<para>Note that <varname>ExecStartPre=</varname> may not be
used to start long-running processes. All processes forked
off by processes invoked via <varname>ExecStartPre=</varname> will
be killed before the next service process is run.</para>
<para>Note that if any of the commands specified in <varname>ExecStartPre=</varname>,
<varname>ExecStart=</varname>, or <varname>ExecStartPost=</varname> fail (and are not prefixed with
<literal>-</literal>, see above) or time out before the service is fully up, execution continues with commands
specified in <varname>ExecStopPost=</varname>, the commands in <varname>ExecStop=</varname> are skipped.</para>
<para>Note that the execution of <varname>ExecStartPost=</varname> is taken into account for the purpose of
<varname>Before=</varname>/<varname>After=</varname> ordering constraints.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ExecCondition=</varname></term>
<listitem><para>Optional commands that are executed before the command(s) in <varname>ExecStartPre=</varname>.
Syntax is the same as for <varname>ExecStart=</varname>, except that multiple command lines are allowed and the
commands are executed one after the other, serially.</para>
<para>The behavior is like an <varname>ExecStartPre=</varname> and condition check hybrid: when an
<varname>ExecCondition=</varname> command exits with exit code 1 through 254 (inclusive), the remaining
commands are skipped and the unit is <emphasis>not</emphasis> marked as failed. However, if an
<varname>ExecCondition=</varname> command exits with 255 or abnormally (e.g. timeout, killed by a
signal, etc.), the unit will be considered failed (and remaining commands will be skipped). Exit code of 0 or
those matching <varname>SuccessExitStatus=</varname> will continue execution to the next command(s).</para>
<para>The same recommendations about not running long-running processes in <varname>ExecStartPre=</varname>
also applies to <varname>ExecCondition=</varname>. <varname>ExecCondition=</varname> will also run the commands
in <varname>ExecStopPost=</varname>, as part of stopping the service, in the case of any non-zero or abnormal
exits, like the ones described above.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ExecReload=</varname></term>
<listitem><para>Commands to execute to trigger a configuration
reload in the service. This argument takes multiple command
lines, following the same scheme as described for
<varname>ExecStart=</varname> above. Use of this setting is
optional. Specifier and environment variable substitution is
supported here following the same scheme as for
<varname>ExecStart=</varname>.</para>
<para>One additional, special environment variable is set: if
known, <varname>$MAINPID</varname> is set to the main process
of the daemon, and may be used for command lines like the
following:</para>
<programlisting>/bin/kill -HUP $MAINPID</programlisting>
<para>Note however that reloading a daemon by sending a signal
(as with the example line above) is usually not a good choice,
because this is an asynchronous operation and hence not
suitable to order reloads of multiple services against each
other. It is strongly recommended to set
<varname>ExecReload=</varname> to a command that not only
triggers a configuration reload of the daemon, but also
synchronously waits for it to complete.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>ExecStop=</varname></term>
<listitem><para>Commands to execute to stop the service started via
<varname>ExecStart=</varname>. This argument takes multiple command lines, following the same scheme
as described for <varname>ExecStart=</varname> above. Use of this setting is optional. After the
commands configured in this option are run, it is implied that the service is stopped, and any
processes remaining for it are terminated according to the <varname>KillMode=</varname> setting (see
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
If this option is not specified, the process is terminated by sending the signal specified in
<varname>KillSignal=</varname> or <varname>RestartKillSignal=</varname> when service stop is
requested. Specifier and environment variable substitution is supported (including
<varname>$MAINPID</varname>, see above).</para>
<para>Note that it is usually not sufficient to specify a command for this setting that only asks the
service to terminate (for example, by sending some form of termination signal to it), but does not
wait for it to do so. Since the remaining processes of the services are killed according to
<varname>KillMode=</varname> and <varname>KillSignal=</varname> or
<varname>RestartKillSignal=</varname> as described above immediately after the command exited, this
may not result in a clean stop. The specified command should hence be a synchronous operation, not an
asynchronous one.</para>
<para>Note that the commands specified in <varname>ExecStop=</varname> are only executed when the service
started successfully first. They are not invoked if the service was never started at all, or in case its
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. Also note that the stop operation is always
performed if the service started successfully, even if the processes in the service terminated on their
own or were killed. The stop commands must be prepared to deal with that case. <varname>$MAINPID</varname>
will be unset if systemd knows that the main process exited by the time the stop commands are called.</para>
<para>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. For post-mortem clean-up steps use <varname>ExecStopPost=</varname> instead.
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>ExecStopPost=</varname></term>
<listitem><para>Additional commands that are executed after the service is stopped. This includes cases where
the commands configured in <varname>ExecStop=</varname> were used, where the service does not have any
<varname>ExecStop=</varname> defined, or where the service exited unexpectedly. This argument takes multiple
command lines, following the same scheme as described for <varname>ExecStart=</varname>. Use of these settings
is optional. Specifier and environment variable substitution is supported. Note that – unlike
<varname>ExecStop=</varname> – commands specified with this setting are invoked when a service failed to start
up correctly and is shut down again.</para>
<para>It is recommended to use this setting for clean-up operations that shall be executed even when the
service failed to start up correctly. Commands configured with this setting need to be able to operate even if
the service failed starting up half-way and left incompletely initialized data around. As the service's
processes have been terminated already when the commands specified with this setting are executed they should
not attempt to communicate with them.</para>
<para>Note that all commands that are configured with this setting are invoked with the result code of the
service, as well as the main process' exit code and status, set in the <varname>$SERVICE_RESULT</varname>,
<varname>$EXIT_CODE</varname> and <varname>$EXIT_STATUS</varname> environment variables, see
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
details.</para>
<para>Note that the execution of <varname>ExecStopPost=</varname> is taken into account for the purpose of
<varname>Before=</varname>/<varname>After=</varname> ordering constraints.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>RestartSec=</varname></term>
<listitem><para>Configures the time to sleep before restarting
a service (as configured with <varname>Restart=</varname>).
Takes a unit-less value in seconds, or a time span value such
as "5min 20s". Defaults to 100ms.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>TimeoutStartSec=</varname></term>
<listitem><para>Configures the time to wait for start-up. If a
daemon service does not signal start-up completion within the
configured time, the service will be considered failed and
will be shut down again. Takes a unit-less value in seconds,
or a time span value such as "5min 20s". Pass
<literal>infinity</literal> to disable the timeout logic. Defaults to
<varname>DefaultTimeoutStartSec=</varname> from the manager
configuration file, except when
<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 extended 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>
<varlistentry>
<term><varname>TimeoutStopSec=</varname></term>
<listitem><para>This option serves two purposes. First, it configures the time to wait for each
<varname>ExecStop=</varname> command. If any of them times out, subsequent <varname>ExecStop=</varname> commands
are skipped and the service will be terminated by <constant>SIGTERM</constant>. If no <varname>ExecStop=</varname>
commands are specified, the service gets the <constant>SIGTERM</constant> immediately. Second, it configures the time
to wait for the service itself to stop. If it doesn't terminate in the specified time, it will be forcibly terminated
by <constant>SIGKILL</constant> (see <varname>KillMode=</varname> in
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
Takes a unit-less value in seconds, or a time span value such
as "5min 20s". Pass <literal>infinity</literal> to disable the
timeout logic. Defaults to
<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 extended 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>
<varlistentry>
<term><varname>TimeoutAbortSec=</varname></term>
<listitem><para>This option configures the time to wait for the service to terminate when it was aborted due to a
watchdog timeout (see <varname>WatchdogSec=</varname>). If the service has a short <varname>TimeoutStopSec=</varname>
this option can be used to give the system more time to write a core dump of the service. Upon expiration the service
will be forcibly terminated by <constant>SIGKILL</constant> (see <varname>KillMode=</varname> in
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>). The core file will
be truncated in this case. Use <varname>TimeoutAbortSec=</varname> to set a sensible timeout for the core dumping per
service that is large enough to write all expected data while also being short enough to handle the service failure
in due time.
</para>
<para>Takes a unit-less value in seconds, or a time span value such as "5min 20s". Pass an empty value to skip
the dedicated watchdog abort timeout handling and fall back <varname>TimeoutStopSec=</varname>. Pass
<literal>infinity</literal> to disable the timeout logic. Defaults to <varname>DefaultTimeoutAbortSec=</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> handles <constant>SIGABRT</constant> itself (instead of relying
on the kernel to write a core dump) it can send <literal>EXTEND_TIMEOUT_USEC=…</literal> to
extended the abort time beyond <varname>TimeoutAbortSec=</varname>. The first receipt of this message
must occur before <varname>TimeoutAbortSec=</varname> is exceeded, and once the abort time has extended beyond
<varname>TimeoutAbortSec=</varname>, the service manager will allow the service to continue to abort, 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>
<varlistentry>
<term><varname>TimeoutSec=</varname></term>
<listitem><para>A shorthand for configuring both
<varname>TimeoutStartSec=</varname> and
<varname>TimeoutStopSec=</varname> to the specified value.
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>RuntimeMaxSec=</varname></term>
<listitem><para>Configures a maximum time for the service to run. If this is used and the service has been
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>
<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 extended 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 achieved by <literal>STOPPING=1</literal> (or termination). (see
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>).
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>WatchdogSec=</varname></term>
<listitem><para>Configures the watchdog timeout for a service.
The watchdog is activated when the start-up is completed. The
service must call
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
regularly with <literal>WATCHDOG=1</literal> (i.e. the
"keep-alive ping"). If the time between two such calls is
larger than the configured time, then the service is placed in
a failed state and it will be terminated with
<constant>SIGABRT</constant> (or the signal specified by
<varname>WatchdogSignal=</varname>). By setting
<varname>Restart=</varname> to <option>on-failure</option>,
<option>on-watchdog</option>, <option>on-abnormal</option> or
<option>always</option>, the service will be automatically
restarted. The time configured here will be passed to the
executed service process in the
<varname>WATCHDOG_USEC=</varname> environment variable. This
allows daemons to automatically enable the keep-alive pinging
logic if watchdog support is enabled for the service. If this
option is used, <varname>NotifyAccess=</varname> (see below)
should be set to open access to the notification socket
provided by systemd. If <varname>NotifyAccess=</varname> is
not set, it will be implicitly set to <option>main</option>.
Defaults to 0, which disables this feature. The service can
check whether the service manager expects watchdog keep-alive
notifications. See
<citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for details.
<citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
may be used to enable automatic watchdog notification support.
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Restart=</varname></term>
<listitem><para>Configures whether the service shall be
restarted when the service process exits, is killed, or a
timeout is reached. The service process may be the main
service process, but it may also be one of the processes
specified with <varname>ExecStartPre=</varname>,
<varname>ExecStartPost=</varname>,
<varname>ExecStop=</varname>,
<varname>ExecStopPost=</varname>, or
<varname>ExecReload=</varname>. When the death of the process
is a result of systemd operation (e.g. service stop or
restart), the service will not be restarted. Timeouts include
missing the watchdog "keep-alive ping" deadline and a service
start, reload, and stop operation timeouts.</para>
<para>Takes one of
<option>no</option>,
<option>on-success</option>,
<option>on-failure</option>,
<option>on-abnormal</option>,
<option>on-watchdog</option>,
<option>on-abort</option>, or
<option>always</option>.
If set to <option>no</option> (the default), the service will
not be restarted. If set to <option>on-success</option>, it
will be restarted only when the service process exits cleanly.
In this context, a clean exit means an exit code of 0, or one
of the signals
<constant>SIGHUP</constant>,
<constant>SIGINT</constant>,
<constant>SIGTERM</constant> or
<constant>SIGPIPE</constant>, and
additionally, exit statuses and signals specified in
<varname>SuccessExitStatus=</varname>. If set to
<option>on-failure</option>, the service will be restarted
when the process exits with a non-zero exit code, is
terminated by a signal (including on core dump, but excluding
the aforementioned four signals), when an operation (such as
service reload) times out, and when the configured watchdog
timeout is triggered. If set to <option>on-abnormal</option>,
the service will be restarted when the process is terminated
by a signal (including on core dump, excluding the
aforementioned four signals), when an operation times out, or
when the watchdog timeout is triggered. If set to
<option>on-abort</option>, the service will be restarted only
if the service process exits due to an uncaught signal not
specified as a clean exit status. If set to
<option>on-watchdog</option>, the service will be restarted
only if the watchdog timeout for the service expires. If set
to <option>always</option>, the service will be restarted
regardless of whether it exited cleanly or not, got terminated
abnormally by a signal, or hit a timeout.</para>
<table>
<title>Exit causes and the effect of the <varname>Restart=</varname> settings on them</title>
<tgroup cols='2'>
<colspec colname='path' />
<colspec colname='expl' />
<thead>
<row>
<entry>Restart settings/Exit causes</entry>
<entry><option>no</option></entry>
<entry><option>always</option></entry>
<entry><option>on-success</option></entry>
<entry><option>on-failure</option></entry>
<entry><option>on-abnormal</option></entry>
<entry><option>on-abort</option></entry>
<entry><option>on-watchdog</option></entry>
</row>
</thead>
<tbody>
<row>
<entry>Clean exit code or signal</entry>
<entry/>
<entry>X</entry>
<entry>X</entry>
<entry/>
<entry/>
<entry/>
<entry/>
</row>
<row>
<entry>Unclean exit code</entry>
<entry/>
<entry>X</entry>
<entry/>
<entry>X</entry>
<entry/>
<entry/>
<entry/>
</row>
<row>
<entry>Unclean signal</entry>
<entry/>
<entry>X</entry>
<entry/>
<entry>X</entry>
<entry>X</entry>
<entry>X</entry>
<entry/>
</row>
<row>
<entry>Timeout</entry>
<entry/>
<entry>X</entry>
<entry/>
<entry>X</entry>
<entry>X</entry>
<entry/>
<entry/>
</row>
<row>
<entry>Watchdog</entry>
<entry/>
<entry>X</entry>
<entry/>
<entry>X</entry>
<entry>X</entry>
<entry/>
<entry>X</entry>
</row>
</tbody>
</tgroup>
</table>
<para>As exceptions to the setting above, the service will not
be restarted if the exit code or signal is specified in
<varname>RestartPreventExitStatus=</varname> (see below) or
the service is stopped with <command>systemctl stop</command>
or an equivalent operation. Also, the services will always be
restarted if the exit code or signal is specified in
<varname>RestartForceExitStatus=</varname> (see below).</para>
<para>Note that service restart is subject to unit start rate
limiting configured with <varname>StartLimitIntervalSec=</varname>
and <varname>StartLimitBurst=</varname>, see
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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
increase reliability by attempting automatic recovery from
errors. For services that shall be able to terminate on their
own choice (and avoid immediate restarting),
<option>on-abnormal</option> is an alternative choice.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>SuccessExitStatus=</varname></term>
<listitem><para>Takes a list of exit status definitions that, when returned by the main service
process, will be considered successful termination, in addition to the normal successful exit code 0
and the signals <constant>SIGHUP</constant>, <constant>SIGINT</constant>,
<constant>SIGTERM</constant>, and <constant>SIGPIPE</constant>. Exit status definitions can be
numeric exit codes, termination code names, or termination signal names, separated by spaces. See the
Process Exit Codes section in
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
a list of termination codes names (for this setting only the part without the
<literal>EXIT_</literal> or <literal>EX_</literal> prefix should be used). See
<citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
a list of signal names.</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
prior assignments of this option will have no
effect.</para>
<example>
<title>A service with with the <varname>SuccessExitStatus=</varname> setting</title>
<programlisting>SuccessExitStatus=TEMPFAIL 250 SIGUSR1</programlisting>
<para>Exit codes 75 (<constant>TEMPFAIL</constant>), 250, and the termination signal
<constant>SIGKILL</constant> are considered clean service terminations.</para>
</example>
<para>Note: <command>systemd-analyze exit-codes</command> may be used to list exit
codes and translate between numerical code values and names.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>RestartPreventExitStatus=</varname></term>
<listitem><para>Takes a list of exit status definitions that, when returned by the main service
process, will prevent automatic service restarts, regardless of the restart setting configured with
<varname>Restart=</varname>. Exit status definitions can either be numeric exit codes or termination
signal names, and are separated by spaces. Defaults to the empty list, so that, by default, no exit
status is excluded from the configured restart logic. For example:
<programlisting>RestartPreventExitStatus=1 6 SIGABRT</programlisting>
ensures that exit codes 1 and 6 and the termination signal <constant>SIGABRT</constant> will not
result in automatic service restarting. This option may appear more than once, in which case the list
of restart-preventing statuses is merged. If the empty string is assigned to this option, the list is
reset and all prior assignments of this option will have no effect.</para>
<para>Note that this setting has no effect on processes configured via
<varname>ExecStartPre=</varname>, <varname>ExecStartPost=</varname>, <varname>ExecStop=</varname>,
<varname>ExecStopPost=</varname> or <varname>ExecReload=</varname>, but only on the main service
process, i.e. either the one invoked by <varname>ExecStart=</varname> or (depending on
<varname>Type=</varname>, <varname>PIDFile=</varname>, …) the otherwise configured main
process.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>RestartForceExitStatus=</varname></term>
<listitem><para>Takes a list of exit status definitions that,
when returned by the main service process, will force automatic
service restarts, regardless of the restart setting configured
with <varname>Restart=</varname>. The argument format is
similar to
<varname>RestartPreventExitStatus=</varname>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>RootDirectoryStartOnly=</varname></term>
<listitem><para>Takes a boolean argument. If true, the root
directory, as configured with the
<varname>RootDirectory=</varname> option (see
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for more information), is only applied to the process started
with <varname>ExecStart=</varname>, and not to the various
other <varname>ExecStartPre=</varname>,
<varname>ExecStartPost=</varname>,
<varname>ExecReload=</varname>, <varname>ExecStop=</varname>,
and <varname>ExecStopPost=</varname> commands. If false, the
setting is applied to all configured commands the same way.
Defaults to false.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>NonBlocking=</varname></term>
<listitem><para>Set the <constant>O_NONBLOCK</constant> flag for all file descriptors passed via socket-based
activation. If true, all file descriptors >= 3 (i.e. all except stdin, stdout, stderr), excluding those passed
in via the file descriptor storage logic (see <varname>FileDescriptorStoreMax=</varname> for details), will
have the <constant>O_NONBLOCK</constant> flag set and hence are in non-blocking mode. This option is only
useful in conjunction with a socket unit, as described in
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry> and has no
effect on file descriptors which were previously saved in the file-descriptor store for example. Defaults to
false.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>NotifyAccess=</varname></term>
<listitem><para>Controls access to the service status notification socket, as accessible via the
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> call. Takes one
of <option>none</option> (the default), <option>main</option>, <option>exec</option> or
<option>all</option>. If <option>none</option>, no daemon status updates are accepted from the service
processes, all status update messages are ignored. If <option>main</option>, only service updates sent from the
main process of the service are accepted. If <option>exec</option>, only service updates sent from any of the
main or control processes originating from one of the <varname>Exec*=</varname> commands are accepted. If
<option>all</option>, all services updates from all members of the service's control group are accepted. This
option should be set to open access to the notification socket when using <varname>Type=notify</varname> or
<varname>WatchdogSec=</varname> (see above). If those options are used but <varname>NotifyAccess=</varname> is
not configured, it will be implicitly set to <option>main</option>.</para>
<para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if
either the sending process is still around at the time PID 1 processes the message, or if the sending process
is explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally
forked off the process, i.e. on all processes that match <option>main</option> or
<option>exec</option>. Conversely, if an auxiliary process of the unit sends an
<function>sd_notify()</function> message and immediately exits, the service manager might not be able to
properly attribute the message to the unit, and thus will ignore it, even if
<varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
<para>Hence, to eliminate all race conditions involving lookup of the client's unit and attribution of notifications
to units correctly, <function>sd_notify_barrier()</function> may be used. This call acts as a synchronization point
and ensures all notifications sent before this call have been picked up by the service manager when it returns
successfully. Use of <function>sd_notify_barrier()</function> is needed for clients which are not invoked by the
service manager, otherwise this synchronization mechanism is unnecessary for attribution of notifications to the
unit.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Sockets=</varname></term>
<listitem><para>Specifies the name of the socket units this
service shall inherit socket file descriptors from when the
service is started. Normally, it should not be necessary to use
this setting, as all socket file descriptors whose unit shares
the same name as the service (subject to the different unit
name suffix of course) are passed to the spawned
process.</para>
<para>Note that the same socket file descriptors may be passed
to multiple processes simultaneously. Also note that a
different service may be activated on incoming socket traffic
than the one which is ultimately configured to inherit the
socket file descriptors. Or, in other words: the
<varname>Service=</varname> setting of
<filename>.socket</filename> units does not have to match the
inverse of the <varname>Sockets=</varname> setting of the
<filename>.service</filename> it refers to.</para>
<para>This option may appear more than once, in which case the list of socket units is merged. Note
that once set, clearing the list of sockets again (for example, by assigning the empty string to this
option) is not supported.</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
<citerefentry><refentrytitle>sd_pid_notify_with_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>'s