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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
<!ENTITY % entities SYSTEM "custom-entities.ent" >
%entities;
]>
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<refentry id="systemd.unit">
<refentryinfo>
<title>systemd.unit</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.unit</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.unit</refname>
<refpurpose>Unit configuration</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename><replaceable>service</replaceable>.service</filename>,
<filename><replaceable>socket</replaceable>.socket</filename>,
<filename><replaceable>device</replaceable>.device</filename>,
<filename><replaceable>mount</replaceable>.mount</filename>,
<filename><replaceable>automount</replaceable>.automount</filename>,
<filename><replaceable>swap</replaceable>.swap</filename>,
<filename><replaceable>target</replaceable>.target</filename>,
<filename><replaceable>path</replaceable>.path</filename>,
<filename><replaceable>timer</replaceable>.timer</filename>,
<filename><replaceable>snapshot</replaceable>.snapshot</filename>,
<filename><replaceable>slice</replaceable>.slice</filename>,
<filename><replaceable>scope</replaceable>.scope</filename></para>
<para><literallayout><filename>/etc/systemd/system/*</filename>
<filename>/run/systemd/system/*</filename>
<filename>/usr/lib/systemd/system/*</filename>
<filename>...</filename>
</literallayout></para>
<para><literallayout><filename>$XDG_CONFIG_HOME/systemd/user/*</filename>
<filename>$HOME/.config/systemd/user/*</filename>
<filename>/etc/systemd/user/*</filename>
<filename>/run/systemd/user/*</filename>
<filename>$XDG_DATA_HOME/systemd/user/*</filename>
<filename>$HOME/.local/share/systemd/user/*</filename>
<filename>/usr/lib/systemd/user/*</filename>
<filename>...</filename>
</literallayout></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>A unit configuration file encodes information
about a service, a socket, a device, a mount point, an
automount point, a swap file or partition, a start-up
target, a watched file system path, a timer controlled
and supervised by
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
a temporary system state snapshot, a resource
management slice or a group of externally created
processes. The syntax is inspired by <ulink
url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
Desktop Entry Specification</ulink>
<filename>.desktop</filename> files, which are in turn
inspired by Microsoft Windows
<filename>.ini</filename> files.</para>
<para>This man page lists the common configuration
options of all the unit types. These options need to
be configured in the [Unit] or [Install]
sections of the unit files.</para>
<para>In addition to the generic [Unit] and [Install]
sections described here, each unit may have a
type-specific section, e.g. [Service] for a service
unit. See the respective man pages for more
information:
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
<citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
<para>Various settings are allowed to be specified
more than once, in which case the interpretation
depends on the setting. Often, multiple settings form
a list, and setting to an empty value "resets", which
means that previous assignments are ignored. When this
is allowed, it is mentioned in the description of the
setting. Note that using multiple assignments to the
same value makes the unit file incompatible with
parsers for the XDG <filename>.desktop</filename> file
format.</para>
<para>Unit files are loaded from a set of paths
determined during compilation, described in the next section.
</para>
<para>Unit files may contain additional options on top
of those listed here. If systemd encounters an unknown
option, it will write a warning log message but
continue loading the unit. If an option or section name
is prefixed with <option>X-</option>, it is ignored
completely by systemd. Options within an ignored
section do not need the prefix. Applications may use
this to include additional information in the unit
files.</para>
<para>Boolean arguments used in unit files can be
written in various formats. For positive settings the
strings <option>1</option>, <option>yes</option>,
<option>true</option> and <option>on</option> are
equivalent. For negative settings, the strings
<option>0</option>, <option>no</option>,
<option>false</option> and <option>off</option> are
equivalent.</para>
<para>Time span values encoded in unit files can be
written in various formats. A stand-alone number
specifies a time in seconds. If suffixed with a time
unit, the unit is honored. A concatenation of multiple
values with units is supported, in which case the
values are added up. Example: "50" refers to 50
seconds; "2min 200ms" refers to 2 minutes plus 200
milliseconds, i.e. 120200ms. The following time units
are understood: s, min, h, d, w, ms, us. For details
see
<citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
<para>Empty lines and lines starting with # or ; are
ignored. This may be used for commenting. Lines ending
in a backslash are concatenated with the following
line while reading and the backslash is replaced by a
space character. This may be used to wrap long lines.</para>
<para>Along with a unit file
<filename>foo.service</filename>, the directory
<filename>foo.service.wants/</filename> may exist. All
unit files symlinked from such a directory are
implicitly added as dependencies of type
<varname>Wanted=</varname> to the unit. This is useful
to hook units into the start-up of other units,
without having to modify their unit files. For details
about the semantics of <varname>Wanted=</varname>, see
below. The preferred way to create symlinks in the
<filename>.wants/</filename> directory of a unit file
is with the <command>enable</command> command of the
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
tool which reads information from the [Install]
section of unit files (see below). A similar
functionality exists for <varname>Requires=</varname>
type dependencies as well, the directory suffix is
<filename>.requires/</filename> in this case.</para>
<para>Along with a unit file
<filename>foo.service</filename>, a directory
<filename>foo.service.d/</filename> may exist. All
files with the suffix <literal>.conf</literal> from
this directory will be parsed after the file itself is
parsed. This is useful to alter or add configuration
settings to a unit, without having to modify their
unit files. Make sure that the file that is included
has the appropriate section headers before any
directive. Note that for instanced units this logic
will first look for the instance
<literal>.d/</literal> subdirectory and read its
<literal>.conf</literal> files, followed by the
template <literal>.d/</literal> subdirectory and reads
its <literal>.conf</literal> files.</para>
<para>Note that while systemd offers a flexible
dependency system between units it is recommended to
use this functionality only sparingly and instead rely
on techniques such as bus-based or socket-based
activation which make dependencies implicit, resulting
in a both simpler and more flexible system.</para>
<para>Some unit names reflect paths existing in the
file system namespace. Example: a device unit
<filename>dev-sda.device</filename> refers to a device
with the device node <filename noindex='true'>/dev/sda</filename> in
the file system namespace. If this applies, a special
way to escape the path name is used, so that the
result is usable as part of a filename. Basically,
given a path, "/" is replaced by "-", and all
unprintable characters and the "-" are replaced by
C-style "\x20" escapes. The root directory "/" is
encoded as single dash, while otherwise the initial
and ending "/" is removed from all paths during
transformation. This escaping is reversible.</para>
<para>Optionally, units may be instantiated from a
template file at runtime. This allows creation of
multiple units from a single configuration file. If
systemd looks for a unit configuration file, it will
first search for the literal unit name in the
file system. If that yields no success and the unit
name contains an <literal>@</literal> character, systemd will look for a
unit template that shares the same name but with the
instance string (i.e. the part between the <literal>@</literal> character
and the suffix) removed. Example: if a service
<filename>getty@tty3.service</filename> is requested
and no file by that name is found, systemd will look
for <filename>getty@.service</filename> and
instantiate a service from that configuration file if
it is found.</para>
<para>To refer to the instance string from
within the configuration file you may use the special
<literal>%i</literal> specifier in many of the
configuration options. See below for details.</para>
<para>If a unit file is empty (i.e. has the file size
0) or is symlinked to <filename>/dev/null</filename>,
its configuration will not be loaded and it appears
with a load state of <literal>masked</literal>, and
cannot be activated. Use this as an effective way to
fully disable a unit, making it impossible to start it
even manually.</para>
<para>The unit file format is covered by the
<ulink
url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
Stability Promise</ulink>.</para>
</refsect1>
<refsect1>
<title>Unit Load Path</title>
<para>Unit files are loaded from a set of paths
determined during compilation, described in the two
tables below. Unit files found in directories listed
earlier override files with the same name in
directories lower in the list.</para>
<para>When systemd is running in user mode
(<option>--user</option>) and the variable
<varname>$SYSTEMD_UNIT_PATH</varname> is set, this
contents of this variable overrides the unit load
path. If <varname>$SYSTEMD_UNIT_PATH</varname> ends
with an empty component (<literal>:</literal>), the
usual unit load path will be appended to the contents
of the variable.</para>
<table>
<title>
Load path when running in system mode (<option>--system</option>).
</title>
<tgroup cols='2'>
<colspec colname='path' />
<colspec colname='expl' />
<thead>
<row>
<entry>Path</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><filename>/etc/systemd/system</filename></entry>
<entry>Local configuration</entry>
</row>
<row>
<entry><filename>/run/systemd/system</filename></entry>
<entry>Runtime units</entry>
</row>
<row>
<entry><filename>/usr/lib/systemd/system</filename></entry>
<entry>Units of installed packages</entry>
</row>
</tbody>
</tgroup>
</table>
<table>
<title>
Load path when running in user mode (<option>--user</option>).
</title>
<tgroup cols='2'>
<colspec colname='path' />
<colspec colname='expl' />
<thead>
<row>
<entry>Path</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><filename>$XDG_CONFIG_HOME/systemd/user</filename></entry>
<entry>User configuration (only used when $XDG_CONFIG_HOME is set)</entry>
</row>
<row>
<entry><filename>$HOME/.config/systemd/user</filename></entry>
<entry>User configuration (only used when $XDG_CONFIG_HOME is not set)</entry>
</row>
<row>
<entry><filename>/etc/systemd/user</filename></entry>
<entry>Local configuration</entry>
</row>
<row>
<entry><filename>/run/systemd/user</filename></entry>
<entry>Runtime units</entry>
</row>
<row>
<entry><filename>$XDG_DATA_HOME/systemd/user</filename></entry>
<entry>Units of packages that have been installed in the home directory (only used when $XDG_DATA_HOME is set)</entry>
</row>
<row>
<entry><filename>$HOME/.local/share/systemd/user</filename></entry>
<entry>Units of packages that have been installed in the home directory (only used when $XDG_DATA_HOME is not set)</entry>
</row>
<row>
<entry><filename>/usr/lib/systemd/user</filename></entry>
<entry>Units of packages that have been installed system-wide</entry>
</row>
</tbody>
</tgroup>
</table>
<para>Additional units might be loaded into systemd
("linked") from directories not on the unit load
path. See the <command>link</command> command for
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>. Also,
some units are dynamically created via generators
<ulink
url="http://www.freedesktop.org/wiki/Software/systemd/Generators/">Generators</ulink>.
</para>
</refsect1>
<refsect1>
<title>[Unit] Section Options</title>
<para>Unit file may include a [Unit] section, which
carries generic information about the unit that is not
dependent on the type of unit:</para>
<variablelist class='unit-directives'>
<varlistentry>
<term><varname>Description=</varname></term>
<listitem><para>A free-form string
describing the unit. This is intended
for use in UIs to show descriptive
information along with the unit
name. The description should contain a name
that means something to the end user.
<literal>Apache2 Web Server</literal> is a good
example. Bad examples are
<literal>high-performance light-weight HTTP
server</literal> (too generic) or
<literal>Apache2</literal> (too specific and
meaningless for people who do not know
Apache).</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Documentation=</varname></term>
<listitem><para>A space-separated list
of URIs referencing documentation for
this unit or its
configuration. Accepted are only URIs
of the types
<literal>http://</literal>,
<literal>https://</literal>,
<literal>file:</literal>,
<literal>info:</literal>,
<literal>man:</literal>. For more
information about the syntax of these
URIs, see
<citerefentry project='man-pages'><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
URIs should be listed in order of
relevance, starting with the most
relevant. It is a good idea to first
reference documentation that explains
what the unit's purpose is, followed
by how it is configured, followed by
any other related documentation. This
option may be specified more than once,
in which case the specified list of
URIs is merged. If the empty string is
assigned to this option, the list is
reset and all prior assignments will
have no effect.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Requires=</varname></term>
<listitem><para>Configures requirement
dependencies on other units. If this
unit gets activated, the units listed
here will be activated as well. If one
of the other units gets deactivated or
its activation fails, this unit will
be deactivated. This option may be
specified more than once or multiple
space-separated units may be specified
in one option in which case
requirement dependencies for all
listed names will be created. Note
that requirement dependencies do not
influence the order in which services
are started or stopped. This has to be
configured independently with the
<varname>After=</varname> or
<varname>Before=</varname> options. If
a unit
<filename>foo.service</filename>
requires a unit
<filename>bar.service</filename> as
configured with
<varname>Requires=</varname> and no
ordering is configured with
<varname>After=</varname> or
<varname>Before=</varname>, then both
units will be started simultaneously
and without any delay between them if
<filename>foo.service</filename> is
activated. Often it is a better choice
to use <varname>Wants=</varname>
instead of
<varname>Requires=</varname> in order
to achieve a system that is more
robust when dealing with failing
services.</para>
<para>Note that dependencies of this
type may also be configured outside of
the unit configuration file by
adding a symlink to a
<filename>.requires/</filename> directory
accompanying the unit file. For
details see above.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>RequiresOverridable=</varname></term>
<listitem><para>Similar to
<varname>Requires=</varname>.
Dependencies listed in
<varname>RequiresOverridable=</varname>
which cannot be fulfilled or fail to
start are ignored if the startup was
explicitly requested by the user. If
the start-up was pulled in indirectly
by some dependency or automatic
start-up of units that is not
requested by the user, this dependency
must be fulfilled and otherwise the
transaction fails. Hence, this option
may be used to configure dependencies
that are normally honored unless the
user explicitly starts up the unit, in
which case whether they failed or not
is irrelevant.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Requisite=</varname></term>
<term><varname>RequisiteOverridable=</varname></term>
<listitem><para>Similar to
<varname>Requires=</varname> and
<varname>RequiresOverridable=</varname>,
respectively. However, if the units
listed here are not started already,
they will not be started and the
transaction will fail immediately.
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Wants=</varname></term>
<listitem><para>A weaker version of
<varname>Requires=</varname>. Units
listed in this option will be started
if the configuring unit is. However,
if the listed units fail to start
or cannot be added to the transaction,
this has no impact on the validity of
the transaction as a whole. This is
the recommended way to hook start-up
of one unit to the start-up of another
unit.</para>
<para>Note that dependencies of this
type may also be configured outside of
the unit configuration file by adding
symlinks to a
<filename>.wants/</filename> directory
accompanying the unit file. For
details, see above.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>BindsTo=</varname></term>
<listitem><para>Configures requirement
dependencies, very similar in style to
<varname>Requires=</varname>, however
in addition to this behavior, it also
declares that this unit is stopped
when any of the units listed suddenly
disappears. Units can suddenly,
unexpectedly disappear if a service
terminates on its own choice, a device
is unplugged or a mount point
unmounted without involvement of
systemd.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>PartOf=</varname></term>
<listitem><para>Configures dependencies
similar to <varname>Requires=</varname>,
but limited to stopping and restarting
of units. When systemd stops or restarts
the units listed here, the action is
propagated to this unit.
Note that this is a one-way dependency —
changes to this unit do not affect the
listed units.
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Conflicts=</varname></term>
<listitem><para>A space-separated list
of unit names. Configures negative
requirement dependencies. If a unit
has a <varname>Conflicts=</varname>
setting on another unit, starting the
former will stop the latter and vice
versa. Note that this setting is
independent of and orthogonal to the
<varname>After=</varname> and
<varname>Before=</varname> ordering
dependencies.</para>
<para>If a unit A that conflicts with
a unit B is scheduled to be started at
the same time as B, the transaction
will either fail (in case both are
required part of the transaction) or
be modified to be fixed (in case one
or both jobs are not a required part
of the transaction). In the latter
case, the job that is not the required
will be removed, or in case both are
not required, the unit that conflicts
will be started and the unit that is
conflicted is
stopped.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Before=</varname></term>
<term><varname>After=</varname></term>
<listitem><para>A space-separated list
of unit names. Configures ordering
dependencies between units. If a unit
<filename>foo.service</filename>
contains a setting
<option>Before=bar.service</option>
and both units are being started,
<filename>bar.service</filename>'s
start-up is delayed until
<filename>foo.service</filename> is
started up. Note that this setting is
independent of and orthogonal to the
requirement dependencies as configured
by <varname>Requires=</varname>. It is
a common pattern to include a unit
name in both the
<varname>After=</varname> and
<varname>Requires=</varname> option, in
which case the unit listed will be
started before the unit that is
configured with these options. This
option may be specified more than
once, in which case ordering
dependencies for all listed names are
created. <varname>After=</varname> is
the inverse of
<varname>Before=</varname>, i.e. while
<varname>After=</varname> ensures that
the configured unit is started after
the listed unit finished starting up,
<varname>Before=</varname> ensures the
opposite, i.e. that the configured
unit is fully started up before the
listed unit is started. Note that when
two units with an ordering dependency
between them are shut down, the
inverse of the start-up order is
applied. i.e. if a unit is configured
with <varname>After=</varname> on
another unit, the former is stopped
before the latter if both are shut
down. If one unit with an ordering
dependency on another unit is shut
down while the latter is started up,
the shut down is ordered before the
start-up regardless of whether the
ordering dependency is actually of
type <varname>After=</varname> or
<varname>Before=</varname>. If two
units have no ordering dependencies
between them, they are shut down or
started up simultaneously, and no
ordering takes
place. </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>OnFailure=</varname></term>
<listitem><para>A space-separated list
of one or more units that are
activated when this unit enters the
<literal>failed</literal>
state.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>PropagatesReloadTo=</varname></term>
<term><varname>ReloadPropagatedFrom=</varname></term>
<listitem><para>A space-separated list
of one or more units where reload
requests on this unit will be
propagated to, or reload requests on
the other unit will be propagated to
this unit, respectively. Issuing a
reload request on a unit will
automatically also enqueue a reload
request on all units that the reload
request shall be propagated to via
these two settings.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>JoinsNamespaceOf=</varname></term>
<listitem><para>For units that start
processes (such as service units),
lists one or more other units whose
network and/or temporary file
namespace to join. This only applies
to unit types which support the
<varname>PrivateNetwork=</varname> and
<varname>PrivateTmp=</varname>
directives (see
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details). If a unit that has this
setting set is started, its processes
will see the same
<filename>/tmp</filename>,
<filename>/tmp/var</filename> and
network namespace as one listed unit
that is started. If multiple listed
units are already started, it is not
defined which namespace is
joined. Note that this setting only
has an effect if
<varname>PrivateNetwork=</varname>
and/or <varname>PrivateTmp=</varname>
is enabled for both the unit that
joins the namespace and the unit whose
namespace is joined.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>RequiresMountsFor=</varname></term>
<listitem><para>Takes a
space-separated list of absolute
paths. Automatically adds dependencies
of type <varname>Requires=</varname>
and <varname>After=</varname> for all
mount units required to access the
specified path.</para>
<para>Mount points marked with
<option>noauto</option> are not
mounted automatically and will be
ignored for the purposes of this
option. If such a mount should be a
requirement for this unit,
direct dependencies on the mount
units may be added
(<varname>Requires=</varname> and
<varname>After=</varname> or
some other combination).
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>OnFailureJobMode=</varname></term>
<listitem><para>Takes a value of
<literal>fail</literal>,
<literal>replace</literal>,
<literal>replace-irreversibly</literal>,
<literal>isolate</literal>,
<literal>flush</literal>,
<literal>ignore-dependencies</literal>
or
<literal>ignore-requirements</literal>. Defaults
to
<literal>replace</literal>. Specifies
how the units listed in
<varname>OnFailure=</varname> will be
enqueued. See
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
<option>--job-mode=</option> option
for details on the possible values. If
this is set to
<literal>isolate</literal>, only a
single unit may be listed in
<varname>OnFailure=</varname>..</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>IgnoreOnIsolate=</varname></term>
<listitem><para>Takes a boolean
argument. If <option>true</option>,
this unit will not be stopped when
isolating another unit. Defaults to
<option>false</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>IgnoreOnSnapshot=</varname></term>
<listitem><para>Takes a boolean
argument. If <option>true</option>,
this unit will not be included in
snapshots. Defaults to
<option>true</option> for device and
snapshot units, <option>false</option>
for the others.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>StopWhenUnneeded=</varname></term>
<listitem><para>Takes a boolean
argument. If <option>true</option>,
this unit will be stopped when it is
no longer used. Note that in order to
minimize the work to be executed,
systemd will not stop units by default
unless they are conflicting with other
units, or the user explicitly
requested their shut down. If this
option is set, a unit will be
automatically cleaned up if no other
active unit requires it. Defaults to
<option>false</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>RefuseManualStart=</varname></term>
<term><varname>RefuseManualStop=</varname></term>
<listitem><para>Takes a boolean
argument. If <option>true</option>,
this unit can only be activated
or deactivated indirectly. In
this case, explicit start-up
or termination requested by the
user is denied, however if it is
started or stopped as a
dependency of another unit, start-up
or termination will succeed. This
is mostly a safety feature to ensure
that the user does not accidentally
activate units that are not intended
to be activated explicitly, and not
accidentally deactivate units that are
not intended to be deactivated.
These options default to
<option>false</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>AllowIsolate=</varname></term>
<listitem><para>Takes a boolean
argument. If <option>true</option>,
this unit may be used with the
<command>systemctl isolate</command>
command. Otherwise, this will be
refused. It probably is a good idea to
leave this disabled except for target
units that shall be used similar to
runlevels in SysV init systems, just
as a precaution to avoid unusable
system states. This option defaults to
<option>false</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>DefaultDependencies=</varname></term>
<listitem><para>Takes a boolean
argument. If <option>true</option>,
(the default), a few default
dependencies will implicitly be
created for the unit. The actual
dependencies created depend on the
unit type. For example, for service
units, these dependencies ensure that
the service is started only after
basic system initialization is
completed and is properly terminated on
system shutdown. See the respective
man pages for details. Generally, only
services involved with early boot or
late shutdown should set this option
to <option>false</option>. It is
highly recommended to leave this
option enabled for the majority of
common units. If set to
<option>false</option>, this option
does not disable all implicit
dependencies, just non-essential
ones.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>JobTimeoutSec=</varname></term>
<listitem><para>When clients are
waiting for a job of this unit to
complete, time out after the specified
time. If this time limit is reached,
the job will be cancelled, the unit
however will not change state or even
enter the <literal>failed</literal>
mode. This value defaults to 0 (job
timeouts disabled), except for device
units. NB: this timeout is independent
from any unit-specific timeout (for
example, the timeout set with
<varname>Timeout=</varname> in service
units) as the job timeout has no
effect on the unit itself, only on the
job that might be pending for it. Or
in other words: unit-specific timeouts
are useful to abort unit state
changes, and revert them. The job
timeout set with this option however
is useful to abort only the job
waiting for the unit state to
change.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>ConditionArchitecture=</varname></term>
<term><varname>ConditionVirtualization=</varname></term>
<term><varname>ConditionHost=</varname></term>
<term><varname>ConditionKernelCommandLine=</varname></term>
<term><varname>ConditionSecurity=</varname></term>
<term><varname>ConditionCapability=</varname></term>
<term><varname>ConditionACPower=</varname></term>
<term><varname>ConditionNeedsUpdate=</varname></term>
<term><varname>ConditionFirstBoot=</varname></term>
<term><varname>ConditionPathExists=</varname></term>
<term><varname>ConditionPathExistsGlob=</varname></term>
<term><varname>ConditionPathIsDirectory=</varname></term>
<term><varname>ConditionPathIsSymbolicLink=</varname></term>
<term><varname>ConditionPathIsMountPoint=</varname></term>
<term><varname>ConditionPathIsReadWrite=</varname></term>
<term><varname>ConditionDirectoryNotEmpty=</varname></term>
<term><varname>ConditionFileNotEmpty=</varname></term>
<term><varname>ConditionFileIsExecutable=</varname></term>
<term><varname>ConditionNull=</varname></term>
<listitem><para>Before starting a unit
verify that the specified condition is
true. If it is not true, the starting
of the unit will be skipped, however
all ordering dependencies of it are
still respected. A failing condition
will not result in the unit being
moved into a failure state. The
condition is checked at the time the
queued start job is to be
executed.</para>
<para><varname>ConditionArchitecture=</varname>
may be used to check whether the
system is running on a specific
architecture. Takes one of
<varname>x86</varname>,
<varname>x86-64</varname>,
<varname>ppc</varname>,
<varname>ppc-le</varname>,
<varname>ppc64</varname>,
<varname>ppc64-le</varname>,
<varname>ia64</varname>,
<varname>parisc</varname>,
<varname>parisc64</varname>,
<varname>s390</varname>,
<varname>s390x</varname>,
<varname>sparc</varname>,
<varname>sparc64</varname>,
<varname>mips</varname>,
<varname>mips-le</varname>,
<varname>mips64</varname>,
<varname>mips64-le</varname>,
<varname>alpha</varname>,
<varname>arm</varname>,
<varname>arm-be</varname>,
<varname>arm64</varname>,
<varname>arm64-be</varname>,
<varname>sh</varname>,
<varname>sh64</varname>,
<varname>m86k</varname>,
<varname>tilegx</varname>,
<varname>cris</varname> to test
against a specific architecture. The
architecture is determined from the
information returned by
<citerefentry><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
and is thus subject to
<citerefentry><refentrytitle>personality</refentrytitle><manvolnum>2</manvolnum></citerefentry>. Note
that a <varname>Personality=</varname>
setting in the same unit file has no
effect on this condition. A special
architecture name
<varname>native</varname> is mapped to
the architecture the system manager
itself is compiled for. The test may
be negated by prepending an
exclamation mark.</para>
<para><varname>ConditionVirtualization=</varname>
may be used to check whether the
system is executed in a virtualized
environment and optionally test
whether it is a specific
implementation. Takes either boolean
value to check if being executed in
any virtualized environment, or one of
<varname>vm</varname> and
<varname>container</varname> to test
against a generic type of
virtualization solution, or one of
<varname>qemu</varname>,
<varname>kvm</varname>,
<varname>zvm</varname>,
<varname>vmware</varname>,
<varname>microsoft</varname>,
<varname>oracle</varname>,
<varname>xen</varname>,
<varname>bochs</varname>,
<varname>uml</varname>,
<varname>openvz</varname>,
<varname>lxc</varname>,
<varname>lxc-libvirt</varname>,
<varname>systemd-nspawn</varname> to
test against a specific
implementation. If multiple
virtualization technologies are nested,
only the innermost is considered. The
test may be negated by prepending an
exclamation mark.</para>
<para><varname>ConditionHost=</varname>
may be used to match against the
hostname or machine ID of the
host. This either takes a hostname
string (optionally with shell style
globs) which is tested against the
locally set hostname as returned by
<citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
or a machine ID formatted as string
(see
<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
The test may be negated by prepending
an exclamation mark.</para>
<para><varname>ConditionKernelCommandLine=</varname>
may be used to check whether a
specific kernel command line option is
set (or if prefixed with the
exclamation mark unset). The argument
must either be a single word, or an
assignment (i.e. two words, separated
<literal>=</literal>). In the former
case the kernel command line is
searched for the word appearing as is,
or as left hand side of an
assignment. In the latter case, the
exact assignment is looked for with
right and left hand side
matching.</para>
<para><varname>ConditionSecurity=</varname>
may be used to check whether the given
security module is enabled on the
system. Currently the recognized values
values are <varname>selinux</varname>,
<varname>apparmor</varname>,
<varname>ima</varname> and
<varname>smack</varname>.
The test may be negated by prepending
an exclamation
mark.</para>
<para><varname>ConditionCapability=</varname>
may be used to check whether the given
capability exists in the capability
bounding set of the service manager
(i.e. this does not check whether
capability is actually available in
the permitted or effective sets, see
<citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
for details). Pass a capability name
such as <literal>CAP_MKNOD</literal>,
possibly prefixed with an exclamation
mark to negate the check.</para>
<para><varname>ConditionACPower=</varname>
may be used to check whether the
system has AC power, or is exclusively
battery powered at the time of
activation of the unit. This takes a
boolean argument. If set to
<varname>true</varname>, the condition
will hold only if at least one AC
connector of the system is connected
to a power source, or if no AC
connectors are known. Conversely, if
set to <varname>false</varname>, the
condition will hold only if there is
at least one AC connector known and
all AC connectors are disconnected
from a power source.</para>
<para><varname>ConditionNeedsUpdate=</varname>
takes one of <filename>/var</filename>
or <filename>/etc</filename> as
argument, possibly prefixed with a
<literal>!</literal> (for inverting
the condition). This condition may be
used to conditionalize units on
whether the specified directory
requires an update because
<filename>/usr</filename>'s
modification time is newer than the
stamp file
<filename>.updated</filename> in the
specified directory. This is useful to
implement offline updates of the
vendor operating system resources in
<filename>/usr</filename> that require
updating of <filename>/etc</filename>
or <filename>/var</filename> on the
next following boot. Units making use
of this condition should order
themselves before
<citerefentry><refentrytitle>systemd-update-done.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
to make sure they run before the stamp
files's modification time gets reset
indicating a completed update.</para>
<para><varname>ConditionFirstBoot=</varname>
takes a boolean argument. This
condition may be used to
conditionalize units on whether the
system is booting up with an
unpopulated <filename>/etc</filename>
directory. This may be used to
populate <filename>/etc</filename> on
the first boot after factory reset, or
when a new system instances boots up
for the first time.</para>
<para>With
<varname>ConditionPathExists=</varname>
a file existence condition is
checked before a unit is started. If
the specified absolute path name does
not exist, the condition will
fail. If the absolute path name passed
to
<varname>ConditionPathExists=</varname>
is prefixed with an exclamation mark
(<literal>!</literal>), the test is negated, and the unit
is only started if the path does not
exist.</para>
<para><varname>ConditionPathExistsGlob=</varname>
is similar to
<varname>ConditionPathExists=</varname>,
but checks for the existence of at
least one file or directory matching
the specified globbing pattern.</para>
<para><varname>ConditionPathIsDirectory=</varname>
is similar to
<varname>ConditionPathExists=</varname>
but verifies whether a certain path
exists and is a
directory.</para>
<para><varname>ConditionPathIsSymbolicLink=</varname>
is similar to
<varname>ConditionPathExists=</varname>
but verifies whether a certain path
exists and is a symbolic
link.</para>
<para><varname>ConditionPathIsMountPoint=</varname>
is similar to
<varname>ConditionPathExists=</varname>
but verifies whether a certain path
exists and is a mount
point.</para>
<para><varname>ConditionPathIsReadWrite=</varname>
is similar to
<varname>ConditionPathExists=</varname>
but verifies whether the underlying
file system is readable and writable
(i.e. not mounted
read-only).</para>
<para><varname>ConditionDirectoryNotEmpty=</varname>
is similar to
<varname>ConditionPathExists=</varname>
but verifies whether a certain path
exists and is a non-empty
directory.</para>
<para><varname>ConditionFileNotEmpty=</varname>
is similar to
<varname>ConditionPathExists=</varname>
but verifies whether a certain path
exists and refers to a regular file
with a non-zero size.</para>
<para><varname>ConditionFileIsExecutable=</varname>
is similar to
<varname>ConditionPathExists=</varname>
but verifies whether a certain path
exists, is a regular file and marked
executable.</para>
<para>Finally,
<varname>ConditionNull=</varname> may
be used to add a constant condition
check value to the unit. It takes a
boolean argument. If set to
<varname>false</varname>, the condition
will always fail, otherwise
succeed.</para>
<para>If multiple conditions are
specified, the unit will be executed if
all of them apply (i.e. a logical AND
is applied). Condition checks can be
prefixed with a pipe symbol (|) in
which case a condition becomes a
triggering condition. If at least one
triggering condition is defined for a
unit, then the unit will be executed if
at least one of the triggering
conditions apply and all of the
non-triggering conditions. If you
prefix an argument with the pipe
symbol and an exclamation mark, the
pipe symbol must be passed first, the
exclamation second. Except for
<varname>ConditionPathIsSymbolicLink=</varname>,
all path checks follow symlinks. If
any of these options is assigned the
empty string, the list of conditions is
reset completely, all previous
condition settings (of any kind) will
have no effect.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>SourcePath=</varname></term>
<listitem><para>A path to a
configuration file this unit has been
generated from. This is primarily
useful for implementation of generator
tools that convert configuration from
an external configuration file format
into native unit files. This
functionality should not be used in
normal units.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>[Install] Section Options</title>
<para>Unit file may include an
<literal>[Install]</literal> section, which carries
installation information for the unit. This section is
not interpreted by
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
during runtime. It is used exclusively by the
<command>enable</command> and
<command>disable</command> commands of the
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
tool during installation of a unit:</para>
<variablelist class='unit-directives'>
<varlistentry>
<term><varname>Alias=</varname></term>
<listitem><para>A space-separated list
of additional names this unit shall be
installed under. The names listed here
must have the same suffix (i.e. type)
as the unit file name. This option may
be specified more than once, in which
case all listed names are used. At
installation time, <command>systemctl
enable</command> will create symlinks
from these names to the unit
filename.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>WantedBy=</varname></term>
<term><varname>RequiredBy=</varname></term>
<listitem><para>This option may be
used more than once, or a
space-separated list of unit names may
be given. A symbolic link is created
in the <filename>.wants/</filename> or
<filename>.requires/</filename>
directory of each of the listed units
when this unit is installed by
<command>systemctl enable</command>.
This has the effect that a dependency
of type <varname>Wants=</varname> or
<varname>Requires=</varname> is added
from the listed unit to the current
unit. The primary result is that the
current unit will be started when the
listed unit is started. See the
description of
<varname>Wants=</varname> and
<varname>Requires=</varname> in the
[Unit] section for details.</para>
<para><command>WantedBy=foo.service</command>
in a service
<filename>bar.service</filename> is
mostly equivalent to
<command>Alias=foo.service.wants/bar.service</command>
in the same file. In case of template
units, <command>systemctl enable</command>
must be called with an instance name, and
this instance will be added to the
<filename>.wants/</filename> or
<filename>.requires/</filename> list
of the listed unit.
E.g. <command>WantedBy=getty.target</command>
in a service
<filename>getty@.service</filename>
will result in <command>systemctl
enable getty@tty2.service</command>
creating a
<filename>getty.target.wants/getty@tty2.service</filename>
link to <filename>getty@.service</filename>.
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Also=</varname></term>
<listitem><para>Additional units to
install/deinstall when this unit is
installed/deinstalled. If the user
requests installation/deinstallation
of a unit with this option configured,
<command>systemctl enable</command>
and <command>systemctl
disable</command> will automatically
install/uninstall units listed in this option as
well.</para>
<para>This option may be used more
than once, or a space-separated list
of unit names may be
given.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>DefaultInstance=</varname></term>
<listitem><para>In template unit files,
this specifies for which instance the
unit shall be enabled if the template
is enabled without any explicitly set
instance. This option has no effect in
non-template unit files. The specified
string must be usable as instance
identifier.</para></listitem>
</varlistentry>
</variablelist>
<para>The following specifiers are interpreted in the
Install section: %n, %N, %p, %i, %U, %u, %m, %H, %b, %v.
For their meaning see the next section.
</para>
</refsect1>
<refsect1>
<title>Specifiers</title>
<para>Many settings resolve specifiers which may be
used to write generic unit files referring to runtime
or unit parameters that are replaced when the unit
files are loaded. The following specifiers are
understood:</para>
<table>
<title>Specifiers available in unit files</title>
<tgroup cols='3' align='left' colsep='1' rowsep='1'>
<colspec colname="spec" />
<colspec colname="mean" />
<colspec colname="detail" />
<thead>
<row>
<entry>Specifier</entry>
<entry>Meaning</entry>
<entry>Details</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>%n</literal></entry>
<entry>Full unit name</entry>
<entry></entry>
</row>
<row>
<entry><literal>%N</literal></entry>
<entry>Unescaped full unit name</entry>
<entry>Same as <literal>%n</literal>, but with escaping undone</entry>
</row>
<row>
<entry><literal>%p</literal></entry>
<entry>Prefix name</entry>
<entry>For instantiated units, this refers to the string before the <literal>@</literal> character of the unit name. For non-instantiated units, this refers to the name of the unit with the type suffix removed.</entry>
</row>
<row>
<entry><literal>%P</literal></entry>
<entry>Unescaped prefix name</entry>
<entry>Same as <literal>%p</literal>, but with escaping undone</entry>
</row>
<row>
<entry><literal>%i</literal></entry>
<entry>Instance name</entry>
<entry>For instantiated units: this is the string between the <literal>@</literal> character and the suffix of the unit name.</entry>
</row>
<row>
<entry><literal>%I</literal></entry>
<entry>Unescaped instance name</entry>
<entry>Same as <literal>%i</literal>, but with escaping undone</entry>
</row>
<row>
<entry><literal>%f</literal></entry>
<entry>Unescaped filename</entry>
<entry>This is either the unescaped instance name (if applicable) with <filename>/</filename> prepended (if applicable), or the prefix name prepended with <filename>/</filename>.</entry>
</row>
<row>
<entry><literal>%c</literal></entry>
<entry>Control group path of the unit</entry>
<entry>This path does not include the <filename>/sys/fs/cgroup/systemd/</filename> prefix.</entry>
</row>
<row>
<entry><literal>%r</literal></entry>
<entry>Control group path of the slice the unit is placed in</entry>
<entry>This usually maps to the parent cgroup path of <literal>%c</literal>.</entry>
</row>
<row>
<entry><literal>%R</literal></entry>
<entry>Root control group path below which slices and units are placed</entry>
<entry>For system instances, this resolves to <filename>/</filename>, except in containers, where this maps to the container's root control group path.</entry>
</row>
<row>
<entry><literal>%t</literal></entry>
<entry>Runtime directory</entry>
<entry>This is either <filename>/run</filename> (for the system manager) or the path <literal>$XDG_RUNTIME_DIR</literal> resolves to (for user managers).</entry>
</row>
<row>
<entry><literal>%u</literal></entry>
<entry>User name</entry>
<entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
</row>
<row>
<entry><literal>%U</literal></entry>
<entry>User UID</entry>
<entry>This is the numeric UID of the configured user of the unit, or (if none is set) the user running the systemd user instance. Note that this specifier is not available for units run by the systemd system instance (as opposed to those run by a systemd user instance), unless the user has been configured as a numeric UID in the first place or the configured user is the root user.</entry>
</row>
<row>
<entry><literal>%h</literal></entry>
<entry>User home directory</entry>
<entry>This is the home directory of the configured user of the unit, or (if none is set) the user running the systemd user instance. Similar to <literal>%U</literal>, this specifier is not available for units run by the systemd system instance, unless the configured user is the root user.</entry>
</row>
<row>
<entry><literal>%s</literal></entry>
<entry>User shell</entry>
<entry>This is the shell of the configured user of the unit, or (if none is set) the user running the systemd user instance. Similar to <literal>%U</literal>, this specifier is not available for units run by the systemd system instance, unless the configured user is the root user.</entry>
</row>
<row>
<entry><literal>%m</literal></entry>
<entry>Machine ID</entry>
<entry>The machine ID of the running system, formatted as string. See <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information.</entry>
</row>
<row>
<entry><literal>%b</literal></entry>
<entry>Boot ID</entry>
<entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
</row>
<row>
<entry><literal>%H</literal></entry>
<entry>Host name</entry>
<entry>The hostname of the running system at the point in time the unit configuation is loaded.</entry>
</row>
<row>
<entry><literal>%v</literal></entry>
<entry>Kernel release</entry>
<entry>Identical to <command>uname -r</command> output</entry>
</row>
<row>
<entry><literal>%%</literal></entry>
<entry>Single percent sign</entry>
<entry>Use <literal>%%</literal> in place of <literal>%</literal> to specify a single percent sign.</entry>
</row>
</tbody>
</tgroup>
</table>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-verify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>uname</refentrytitle><manvolnum>1</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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