2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
4 <!ENTITY % entities SYSTEM
"custom-entities.ent" >
7 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
9 <refentry id=
"systemd.unit">
12 <title>systemd.unit
</title>
13 <productname>systemd
</productname>
17 <refentrytitle>systemd.unit
</refentrytitle>
18 <manvolnum>5</manvolnum>
22 <refname>systemd.unit
</refname>
23 <refpurpose>Unit configuration
</refpurpose>
27 <para><filename><replaceable>service
</replaceable>.service
</filename>,
28 <filename><replaceable>socket
</replaceable>.socket
</filename>,
29 <filename><replaceable>device
</replaceable>.device
</filename>,
30 <filename><replaceable>mount
</replaceable>.mount
</filename>,
31 <filename><replaceable>automount
</replaceable>.automount
</filename>,
32 <filename><replaceable>swap
</replaceable>.swap
</filename>,
33 <filename><replaceable>target
</replaceable>.target
</filename>,
34 <filename><replaceable>path
</replaceable>.path
</filename>,
35 <filename><replaceable>timer
</replaceable>.timer
</filename>,
36 <filename><replaceable>slice
</replaceable>.slice
</filename>,
37 <filename><replaceable>scope
</replaceable>.scope
</filename></para>
40 <title>System Unit Search Path
</title>
42 <para><literallayout><filename>/etc/systemd/system.control/*
</filename>
43 <filename>/run/systemd/system.control/*
</filename>
44 <filename>/run/systemd/transient/*
</filename>
45 <filename>/run/systemd/generator.early/*
</filename>
46 <filename>/etc/systemd/system/*
</filename>
47 <filename>/etc/systemd/systemd.attached/*
</filename>
48 <filename>/run/systemd/system/*
</filename>
49 <filename>/run/systemd/systemd.attached/*
</filename>
50 <filename>/run/systemd/generator/*
</filename>
51 <filename index='false'
>…
</filename>
52 <filename>/usr/lib/systemd/system/*
</filename>
53 <filename>/run/systemd/generator.late/*
</filename></literallayout></para>
57 <title>User Unit Search Path
</title>
58 <para><literallayout><filename>~/.config/systemd/user.control/*
</filename>
59 <filename>$XDG_RUNTIME_DIR/systemd/user.control/*
</filename>
60 <filename>$XDG_RUNTIME_DIR/systemd/transient/*
</filename>
61 <filename>$XDG_RUNTIME_DIR/systemd/generator.early/*
</filename>
62 <filename>~/.config/systemd/user/*
</filename>
63 <filename>/etc/systemd/user/*
</filename>
64 <filename>$XDG_RUNTIME_DIR/systemd/user/*
</filename>
65 <filename>/run/systemd/user/*
</filename>
66 <filename>$XDG_RUNTIME_DIR/systemd/generator/*
</filename>
67 <filename>~/.local/share/systemd/user/*
</filename>
68 <filename index='false'
>…
</filename>
69 <filename>/usr/lib/systemd/user/*
</filename>
70 <filename>$XDG_RUNTIME_DIR/systemd/generator.late/*
</filename></literallayout></para>
76 <title>Description
</title>
78 <para>A unit file is a plain text ini-style file that encodes information about a service, a
79 socket, a device, a mount point, an automount point, a swap file or partition, a start-up
80 target, a watched file system path, a timer controlled and supervised by
81 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>, a
82 resource management slice or a group of externally created processes. See
83 <citerefentry><refentrytitle>systemd.syntax
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
84 for a general description of the syntax.
</para>
86 <para>This man page lists the common configuration options of all
87 the unit types. These options need to be configured in the [Unit]
88 or [Install] sections of the unit files.
</para>
90 <para>In addition to the generic [Unit] and [Install] sections
91 described here, each unit may have a type-specific section, e.g.
92 [Service] for a service unit. See the respective man pages for
94 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
95 <citerefentry><refentrytitle>systemd.socket
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
96 <citerefentry><refentrytitle>systemd.device
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
97 <citerefentry><refentrytitle>systemd.mount
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
98 <citerefentry><refentrytitle>systemd.automount
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
99 <citerefentry><refentrytitle>systemd.swap
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
100 <citerefentry><refentrytitle>systemd.target
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
101 <citerefentry><refentrytitle>systemd.path
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
102 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
103 <citerefentry><refentrytitle>systemd.slice
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
104 <citerefentry><refentrytitle>systemd.scope
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
107 <para>Unit files are loaded from a set of paths determined during compilation, described in the next
110 <para>Valid unit names consist of a
"name prefix" and a dot and a suffix specifying the unit type. The
111 "unit prefix" must consist of one or more valid characters (ASCII letters, digits,
<literal>:
</literal>,
112 <literal>-
</literal>,
<literal>_
</literal>,
<literal>.
</literal>, and
<literal>\
</literal>). The total
113 length of the unit name including the suffix must not exceed
256 characters. The type suffix must be one
114 of
<literal>.service
</literal>,
<literal>.socket
</literal>,
<literal>.device
</literal>,
115 <literal>.mount
</literal>,
<literal>.automount
</literal>,
<literal>.swap
</literal>,
116 <literal>.target
</literal>,
<literal>.path
</literal>,
<literal>.timer
</literal>,
117 <literal>.slice
</literal>, or
<literal>.scope
</literal>.
</para>
119 <para>Units names can be parameterized by a single argument called the
"instance name". The unit is then
120 constructed based on a
"template file" which serves as the definition of multiple services or other
121 units. A template unit must have a single
<literal>@
</literal> at the end of the name (right before the
122 type suffix). The name of the full unit is formed by inserting the instance name between
123 <literal>@
</literal> and the unit type suffix. In the unit file itself, the instance parameter may be
124 referred to using
<literal>%i
</literal> and other specifiers, see below.
</para>
126 <para>Unit files may contain additional options on top of those
127 listed here. If systemd encounters an unknown option, it will
128 write a warning log message but continue loading the unit. If an
129 option or section name is prefixed with
<option>X-
</option>, it is
130 ignored completely by systemd. Options within an ignored section
131 do not need the prefix. Applications may use this to include
132 additional information in the unit files.
</para>
134 <para>Units can be aliased (have an alternative name), by creating a symlink from the new name to the
135 existing name in one of the unit search paths. For example,
<filename>systemd-networkd.service
</filename>
136 has the alias
<filename>dbus-org.freedesktop.network1.service
</filename>, created during installation as
137 a symlink, so when
<command>systemd
</command> is asked through D-Bus to load
138 <filename>dbus-org.freedesktop.network1.service
</filename>, it'll load
139 <filename>systemd-networkd.service
</filename>. As another example,
<filename>default.target
</filename> —
140 the default system target started at boot — is commonly symlinked (aliased) to either
141 <filename>multi-user.target
</filename> or
<filename>graphical.target
</filename> to select what is started
142 by default. Alias names may be used in commands like
<command>disable
</command>,
143 <command>start
</command>,
<command>stop
</command>,
<command>status
</command>, and similar, and in all
144 unit dependency directives, including
<varname>Wants=
</varname>,
<varname>Requires=
</varname>,
145 <varname>Before=
</varname>,
<varname>After=
</varname>. Aliases cannot be used with the
146 <command>preset
</command> command.
</para>
148 <para>Aliases obey the following restrictions: a unit of a certain type (
<literal>.service
</literal>,
149 <literal>.socket
</literal>, …) can only be aliased by a name with the same type suffix. A plain unit (not
150 a template or an instance), may only be aliased by a plain name. A template instance may only be aliased
151 by another template instance, and the instance part must be identical. A template may be aliased by
152 another template (in which case the alias applies to all instances of the template). As a special case, a
153 template instance (e.g.
<literal>alias@inst.service
</literal>) may be a symlink to different template
154 (e.g.
<literal>template@inst.service
</literal>). In that case, just this specific instance is aliased,
155 while other instances of the template (e.g.
<literal>alias@foo.service
</literal>,
156 <literal>alias@bar.service
</literal>) are not aliased. Those rule preserve the requirement that the
157 instance (if any) is always uniquely defined for a given unit and all its aliases.
</para>
159 <para>Unit files may specify aliases through the
<varname>Alias=
</varname> directive in the [Install]
160 section. When the unit is enabled, symlinks will be created for those names, and removed when the unit is
161 disabled. For example,
<filename>reboot.target
</filename> specifies
162 <varname>Alias=ctrl-alt-del.target
</varname>, so when enabled, the symlink
163 <filename>/etc/systemd/systemd/ctrl-alt-del.service
</filename> pointing to the
164 <filename>reboot.target
</filename> file will be created, and when
165 <keycombo><keycap>Ctrl
</keycap><keycap>Alt
</keycap><keycap>Del
</keycap></keycombo> is invoked,
166 <command>systemd
</command> will look for the
<filename>ctrl-alt-del.service
</filename> and execute
167 <filename>reboot.service
</filename>.
<command>systemd
</command> does not look at the [Install] section at
168 all during normal operation, so any directives in that section only have an effect through the symlinks
169 created during enablement.
</para>
171 <para>Along with a unit file
<filename>foo.service
</filename>, the directory
172 <filename>foo.service.wants/
</filename> may exist. All unit files symlinked from such a directory are
173 implicitly added as dependencies of type
<varname>Wants=
</varname> to the unit. Similar functionality
174 exists for
<varname>Requires=
</varname> type dependencies as well, the directory suffix is
175 <filename>.requires/
</filename> in this case. This functionality is useful to hook units into the
176 start-up of other units, without having to modify their unit files. For details about the semantics of
177 <varname>Wants=
</varname>, see below. The preferred way to create symlinks in the
178 <filename>.wants/
</filename> or
<filename>.requires/
</filename> directory of a unit file is by embedding
179 the dependency in [Install] section of the target unit, and creating the symlink in the file system with
180 the
<command>enable
</command> or
<command>preset
</command> commands of
181 <citerefentry><refentrytitle>systemctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
</para>
183 <para>Along with a unit file
<filename>foo.service
</filename>, a
"drop-in" directory
184 <filename>foo.service.d/
</filename> may exist. All files with the suffix
<literal>.conf
</literal> from this
185 directory will be parsed after the unit file itself is parsed. This is useful to alter or add configuration
186 settings for a unit, without having to modify unit files. Drop-in files must contain appropriate section
187 headers. For instantiated units, this logic will first look for the instance
<literal>.d/
</literal> subdirectory
188 (e.g.
<literal>foo@bar.service.d/
</literal>) and read its
<literal>.conf
</literal> files, followed by the template
189 <literal>.d/
</literal> subdirectory (e.g.
<literal>foo@.service.d/
</literal>) and the
<literal>.conf
</literal>
190 files there. Moreover for units names containing dashes (
<literal>-
</literal>), the set of directories generated by
191 truncating the unit name after all dashes is searched too. Specifically, for a unit name
192 <filename>foo-bar-baz.service
</filename> not only the regular drop-in directory
193 <filename>foo-bar-baz.service.d/
</filename> is searched but also both
<filename>foo-bar-.service.d/
</filename> and
194 <filename>foo-.service.d/
</filename>. This is useful for defining common drop-ins for a set of related units, whose
195 names begin with a common prefix. This scheme is particularly useful for mount, automount and slice units, whose
196 systematic naming structure is built around dashes as component separators. Note that equally named drop-in files
197 further down the prefix hierarchy override those further up,
198 i.e.
<filename>foo-bar-.service.d/
10-override.conf
</filename> overrides
199 <filename>foo-.service.d/
10-override.conf
</filename>.
</para>
201 <para>In cases of unit aliases (described above), dropins for the aliased name and all aliases are
202 loaded. In the example of
<filename>default.target
</filename> aliasing
203 <filename>graphical.target
</filename>,
<filename>default.target.d/
</filename>,
204 <filename>default.target.wants/
</filename>,
<filename>default.target.requires/
</filename>,
205 <filename>graphical.target.d/
</filename>,
<filename>graphical.target.wants/
</filename>,
206 <filename>graphical.target.requires/
</filename> would all be read. For templates, dropins for the
207 template, any template aliases, the template instance, and all alias instances are read. When just a
208 specific template instance is aliased, then the dropins for the target template, the target template
209 instance, and the alias template instance are read.
</para>
211 <para>In addition to
<filename>/etc/systemd/system
</filename>, the drop-in
<literal>.d/
</literal>
212 directories for system services can be placed in
<filename>/usr/lib/systemd/system
</filename> or
213 <filename>/run/systemd/system
</filename> directories. Drop-in files in
<filename>/etc
</filename>
214 take precedence over those in
<filename>/run
</filename> which in turn take precedence over those
215 in
<filename>/usr/lib
</filename>. Drop-in files under any of these directories take precedence
216 over unit files wherever located. Multiple drop-in files with different names are applied in
217 lexicographic order, regardless of which of the directories they reside in.
</para>
219 <para>Units also support a top-level drop-in with
<filename><replaceable>type
</replaceable>.d/
</filename>,
220 where
<replaceable>type
</replaceable> may be e.g.
<literal>service
</literal> or
<literal>socket
</literal>,
221 that allows altering or adding to the settings of all corresponding unit files on the system.
222 The formatting and precedence of applying drop-in configurations follow what is defined above.
223 Configurations in
<filename><replaceable>type
</replaceable>.d/
</filename> have the lowest precedence
224 compared to settings in the name specific override directories. So the contents of
225 <filename>foo-.service.d/
10-override.conf
</filename> would override
226 <filename>service.d/
10-override.conf
</filename>.
</para>
228 <!-- Note that we do not document .include here, as we consider it mostly obsolete, and want
229 people to use .d/ drop-ins instead. -->
231 <para>Note that while systemd offers a flexible dependency system
232 between units it is recommended to use this functionality only
233 sparingly and instead rely on techniques such as bus-based or
234 socket-based activation which make dependencies implicit,
235 resulting in a both simpler and more flexible system.
</para>
237 <para>As mentioned above, a unit may be instantiated from a template file. This allows creation
238 of multiple units from a single configuration file. If systemd looks for a unit configuration
239 file, it will first search for the literal unit name in the file system. If that yields no
240 success and the unit name contains an
<literal>@
</literal> character, systemd will look for a
241 unit template that shares the same name but with the instance string (i.e. the part between the
242 <literal>@
</literal> character and the suffix) removed. Example: if a service
243 <filename>getty@tty3.service
</filename> is requested and no file by that name is found, systemd
244 will look for
<filename>getty@.service
</filename> and instantiate a service from that
245 configuration file if it is found.
</para>
247 <para>To refer to the instance string from within the
248 configuration file you may use the special
<literal>%i
</literal>
249 specifier in many of the configuration options. See below for
252 <para>If a unit file is empty (i.e. has the file size
0) or is
253 symlinked to
<filename>/dev/null
</filename>, its configuration
254 will not be loaded and it appears with a load state of
255 <literal>masked
</literal>, and cannot be activated. Use this as an
256 effective way to fully disable a unit, making it impossible to
257 start it even manually.
</para>
259 <para>The unit file format is covered by the
261 url=
"https://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
262 Stability Promise
</ulink>.
</para>
267 <title>String Escaping for Inclusion in Unit Names
</title>
269 <para>Sometimes it is useful to convert arbitrary strings into unit names. To facilitate this, a method of string
270 escaping is used, in order to map strings containing arbitrary byte values (except NUL) into valid unit names and
271 their restricted character set. A common special case are unit names that reflect paths to objects in the file
272 system hierarchy. Example: a device unit
<filename>dev-sda.device
</filename> refers to a device with the device
273 node
<filename index=
"false">/dev/sda
</filename> in the file system.
</para>
275 <para>The escaping algorithm operates as follows: given a string, any
<literal>/
</literal> character is replaced by
276 <literal>-
</literal>, and all other characters which are not ASCII alphanumerics or
<literal>_
</literal> are
277 replaced by C-style
<literal>\x2d
</literal> escapes. In addition,
<literal>.
</literal> is replaced with such a
278 C-style escape when it would appear as the first character in the escaped string.
</para>
280 <para>When the input qualifies as absolute file system path, this algorithm is extended slightly: the path to the
281 root directory
<literal>/
</literal> is encoded as single dash
<literal>-
</literal>. In addition, any leading,
282 trailing or duplicate
<literal>/
</literal> characters are removed from the string before transformation. Example:
283 <filename>/foo//bar/baz/
</filename> becomes
<literal>foo-bar-baz
</literal>.
</para>
285 <para>This escaping is fully reversible, as long as it is known whether the escaped string was a path (the
286 unescaping results are different for paths and non-path strings). The
287 <citerefentry><refentrytitle>systemd-escape
</refentrytitle><manvolnum>1</manvolnum></citerefentry> command may be
288 used to apply and reverse escaping on arbitrary strings. Use
<command>systemd-escape --path
</command> to escape
289 path strings, and
<command>systemd-escape
</command> without
<option>--path
</option> otherwise.
</para>
293 <title>Automatic dependencies
</title>
296 <title>Implicit Dependencies
</title>
298 <para>A number of unit dependencies are implicitly established, depending on unit type and
299 unit configuration. These implicit dependencies can make unit configuration file cleaner. For
300 the implicit dependencies in each unit type, please refer to section
"Implicit Dependencies"
301 in respective man pages.
</para>
303 <para>For example, service units with
<varname>Type=dbus
</varname> automatically acquire
304 dependencies of type
<varname>Requires=
</varname> and
<varname>After=
</varname> on
305 <filename>dbus.socket
</filename>. See
306 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
311 <title>Default Dependencies
</title>
313 <para>Default dependencies are similar to implicit dependencies, but can be turned on and off
314 by setting
<varname>DefaultDependencies=
</varname> to
<varname>yes
</varname> (the default) and
315 <varname>no
</varname>, while implicit dependencies are always in effect. See section
"Default
316 Dependencies" in respective man pages for the effect of enabling
317 <varname>DefaultDependencies=
</varname> in each unit types.
</para>
319 <para>For example, target units will complement all configured dependencies of type
320 <varname>Wants=
</varname> or
<varname>Requires=
</varname> with dependencies of type
321 <varname>After=
</varname> unless
<varname>DefaultDependencies=no
</varname> is set in the
323 <citerefentry><refentrytitle>systemd.target
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
324 for details. Note that this behavior can be turned off by setting
325 <varname>DefaultDependencies=no
</varname>.
</para>
330 <title>Unit File Load Path
</title>
332 <para>Unit files are loaded from a set of paths determined during
333 compilation, described in the two tables below. Unit files found
334 in directories listed earlier override files with the same name in
335 directories lower in the list.
</para>
337 <para>When the variable
<varname>$SYSTEMD_UNIT_PATH
</varname> is set,
338 the contents of this variable overrides the unit load path. If
339 <varname>$SYSTEMD_UNIT_PATH
</varname> ends with an empty component
340 (
<literal>:
</literal>), the usual unit load path will be appended
341 to the contents of the variable.
</para>
345 Load path when running in system mode (
<option>--system
</option>).
349 <colspec colname='path'
/>
350 <colspec colname='expl'
/>
354 <entry>Description
</entry>
359 <entry><filename>/etc/systemd/system.control
</filename></entry>
360 <entry morerows=
"1">Persistent and transient configuration created using the dbus API
</entry>
363 <entry><filename>/run/systemd/system.control
</filename></entry>
366 <entry><filename>/run/systemd/transient
</filename></entry>
367 <entry>Dynamic configuration for transient units
</entry>
370 <entry><filename>/run/systemd/generator.early
</filename></entry>
371 <entry>Generated units with high priority (see
<replaceable>early-dir
</replaceable> in
<citerefentry
372 ><refentrytitle>systemd.generator
</refentrytitle><manvolnum>7</manvolnum></citerefentry>)
</entry>
375 <entry><filename>/etc/systemd/system
</filename></entry>
376 <entry>System units created by the administrator
</entry>
379 <entry><filename>/run/systemd/system
</filename></entry>
380 <entry>Runtime units
</entry>
383 <entry><filename>/run/systemd/generator
</filename></entry>
384 <entry>Generated units with medium priority (see
<replaceable>normal-dir
</replaceable> in
<citerefentry
385 ><refentrytitle>systemd.generator
</refentrytitle><manvolnum>7</manvolnum></citerefentry>)
</entry>
388 <entry><filename>/usr/local/lib/systemd/system
</filename></entry>
389 <entry>System units installed by the administrator
</entry>
392 <entry><filename>/usr/lib/systemd/system
</filename></entry>
393 <entry>System units installed by the distribution package manager
</entry>
396 <entry><filename>/run/systemd/generator.late
</filename></entry>
397 <entry>Generated units with low priority (see
<replaceable>late-dir
</replaceable> in
<citerefentry
398 ><refentrytitle>systemd.generator
</refentrytitle><manvolnum>7</manvolnum></citerefentry>)
</entry>
406 Load path when running in user mode (
<option>--user
</option>).
410 <colspec colname='path'
/>
411 <colspec colname='expl'
/>
415 <entry>Description
</entry>
420 <entry><filename>$XDG_CONFIG_HOME/systemd/user.control
</filename> or
<filename
421 >~/.config/systemd/user.control
</filename></entry>
422 <entry morerows=
"1">Persistent and transient configuration created using the dbus API (
<varname>$XDG_CONFIG_HOME
</varname> is used if set,
<filename>~/.config
</filename> otherwise)
</entry>
425 <entry><filename>$XDG_RUNTIME_DIR/systemd/user.control
</filename></entry>
428 <entry><filename>/run/systemd/transient
</filename></entry>
429 <entry>Dynamic configuration for transient units
</entry>
432 <entry><filename>/run/systemd/generator.early
</filename></entry>
433 <entry>Generated units with high priority (see
<replaceable>early-dir
</replaceable> in
<citerefentry
434 ><refentrytitle>systemd.generator
</refentrytitle><manvolnum>7</manvolnum></citerefentry>)
</entry>
437 <entry><filename>$XDG_CONFIG_HOME/systemd/user
</filename> or
<filename>$HOME/.config/systemd/user
</filename></entry>
438 <entry>User configuration (
<varname>$XDG_CONFIG_HOME
</varname> is used if set,
<filename>~/.config
</filename> otherwise)
</entry>
441 <entry><filename>/etc/systemd/user
</filename></entry>
442 <entry>User units created by the administrator
</entry>
445 <entry><filename>$XDG_RUNTIME_DIR/systemd/user
</filename></entry>
446 <entry>Runtime units (only used when $XDG_RUNTIME_DIR is set)
</entry>
449 <entry><filename>/run/systemd/user
</filename></entry>
450 <entry>Runtime units
</entry>
453 <entry><filename>$XDG_RUNTIME_DIR/systemd/generator
</filename></entry>
454 <entry>Generated units with medium priority (see
<replaceable>normal-dir
</replaceable> in
<citerefentry
455 ><refentrytitle>systemd.generator
</refentrytitle><manvolnum>7</manvolnum></citerefentry>)
</entry>
458 <entry><filename>$XDG_DATA_HOME/systemd/user
</filename> or
<filename>$HOME/.local/share/systemd/user
</filename></entry>
459 <entry>Units of packages that have been installed in the home directory (
<varname>$XDG_DATA_HOME
</varname> is used if set,
<filename>~/.local/share
</filename> otherwise)
</entry>
462 <entry><filename>$dir/systemd/user
</filename> for each
<varname index=
"false">$dir
</varname> in
<varname>$XDG_DATA_DIRS
</varname></entry>
463 <entry>Additional locations for installed user units, one for each entry in
<varname>$XDG_DATA_DIRS
</varname></entry>
466 <entry><filename>/usr/local/lib/systemd/user
</filename></entry>
467 <entry>User units installed by the administrator
</entry>
470 <entry><filename>/usr/lib/systemd/user
</filename></entry>
471 <entry>User units installed by the distribution package manager
</entry>
474 <entry><filename>$XDG_RUNTIME_DIR/systemd/generator.late
</filename></entry>
475 <entry>Generated units with low priority (see
<replaceable>late-dir
</replaceable> in
<citerefentry
476 ><refentrytitle>systemd.generator
</refentrytitle><manvolnum>7</manvolnum></citerefentry>)
</entry>
482 <para>The set of load paths for the user manager instance may be augmented or
483 changed using various environment variables. And environment variables may in
484 turn be set using environment generators, see
485 <citerefentry><refentrytitle>systemd.environment-generator
</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
486 In particular,
<varname>$XDG_DATA_HOME
</varname> and
487 <varname>$XDG_DATA_DIRS
</varname> may be easily set using
488 <citerefentry><refentrytitle>systemd-environment-d-generator
</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
489 Thus, directories listed here are just the defaults. To see the actual list that
490 would be used based on compilation options and current environment use
491 <programlisting>systemd-analyze --user unit-paths
</programlisting>
494 <para>Moreover, additional units might be loaded into systemd from
495 directories not on the unit load path by creating a symlink pointing to a
496 unit file in the directories. You can use
<command>systemctl link
</command>
497 for this operation. See
498 <citerefentry><refentrytitle>systemctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>
499 for its usage and precaution.
504 <title>Unit Garbage Collection
</title>
506 <para>The system and service manager loads a unit's configuration automatically when a unit is referenced for the
507 first time. It will automatically unload the unit configuration and state again when the unit is not needed anymore
508 (
"garbage collection"). A unit may be referenced through a number of different mechanisms:
</para>
511 <listitem><para>Another loaded unit references it with a dependency such as
<varname>After=
</varname>,
512 <varname>Wants=
</varname>, …
</para></listitem>
514 <listitem><para>The unit is currently starting, running, reloading or stopping.
</para></listitem>
516 <listitem><para>The unit is currently in the
<constant>failed
</constant> state. (But see below.)
</para></listitem>
518 <listitem><para>A job for the unit is pending.
</para></listitem>
520 <listitem><para>The unit is pinned by an active IPC client program.
</para></listitem>
522 <listitem><para>The unit is a special
"perpetual" unit that is always active and loaded. Examples for perpetual
523 units are the root mount unit
<filename>-.mount
</filename> or the scope unit
<filename>init.scope
</filename> that
524 the service manager itself lives in.
</para></listitem>
526 <listitem><para>The unit has running processes associated with it.
</para></listitem>
529 <para>The garbage collection logic may be altered with the
<varname>CollectMode=
</varname> option, which allows
530 configuration whether automatic unloading of units that are in
<constant>failed
</constant> state is permissible,
533 <para>Note that when a unit's configuration and state is unloaded, all execution results, such as exit codes, exit
534 signals, resource consumption and other statistics are lost, except for what is stored in the log subsystem.
</para>
536 <para>Use
<command>systemctl daemon-reload
</command> or an equivalent command to reload unit configuration while
537 the unit is already loaded. In this case all configuration settings are flushed out and replaced with the new
538 configuration (which however might not be in effect immediately), however all runtime state is
539 saved/restored.
</para>
543 <title>[Unit] Section Options
</title>
545 <para>The unit file may include a [Unit] section, which carries
546 generic information about the unit that is not dependent on the
549 <variablelist class='unit-directives'
>
551 <term><varname>Description=
</varname></term>
552 <listitem><para>A human readable name for the unit. This is used by
553 <command>systemd
</command> (and other UIs) as the label for the unit, so this string should
554 identify the unit rather than describe it, despite the name.
<literal>Apache2 Web
555 Server
</literal> is a good example. Bad examples are
<literal>high-performance light-weight
556 HTTP server
</literal> (too generic) or
<literal>Apache2
</literal> (too specific and
557 meaningless for people who do not know Apache).
<command>systemd
</command> will use this
558 string as a noun in status messages (
<literal>Starting
559 <replaceable>description
</replaceable>...
</literal>,
<literal>Started
560 <replaceable>description
</replaceable>.
</literal>,
<literal>Reached target
561 <replaceable>description
</replaceable>.
</literal>,
<literal>Failed to start
562 <replaceable>description
</replaceable>.
</literal>), so it should be capitalized, and should
563 not be a full sentence or a phrase with a continuous verb. Bad examples include
564 <literal>exiting the container
</literal> or
<literal>updating the database once per
565 day.
</literal>.
</para>
570 <term><varname>Documentation=
</varname></term>
571 <listitem><para>A space-separated list of URIs referencing
572 documentation for this unit or its configuration. Accepted are
573 only URIs of the types
<literal>http://
</literal>,
574 <literal>https://
</literal>,
<literal>file:
</literal>,
575 <literal>info:
</literal>,
<literal>man:
</literal>. For more
576 information about the syntax of these URIs, see
<citerefentry
577 project='man-pages'
><refentrytitle>uri
</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
578 The URIs should be listed in order of relevance, starting with
579 the most relevant. It is a good idea to first reference
580 documentation that explains what the unit's purpose is,
581 followed by how it is configured, followed by any other
582 related documentation. This option may be specified more than
583 once, in which case the specified list of URIs is merged. If
584 the empty string is assigned to this option, the list is reset
585 and all prior assignments will have no
586 effect.
</para></listitem>
590 <term><varname>Wants=
</varname></term>
592 <listitem><para>Configures requirement dependencies on other units. This option may be specified more
593 than once or multiple space-separated units may be specified in one option in which case dependencies
594 for all listed names will be created. Dependencies of this type may also be configured outside of the
595 unit configuration file by adding a symlink to a
<filename>.wants/
</filename> directory accompanying
596 the unit file. For details, see above.
</para>
598 <para>Units listed in this option will be started if the configuring unit is. However, if the listed
599 units fail to start or cannot be added to the transaction, this has no impact on the validity of the
600 transaction as a whole, and this unit will still be started. This is the recommended way to hook
601 start-up of one unit to the start-up of another unit.
</para>
603 <para>Note that requirement dependencies do not influence the order in which services are started or
604 stopped. This has to be configured independently with the
<varname>After=
</varname> or
605 <varname>Before=
</varname> options. If unit
<filename>foo.service
</filename> pulls in unit
606 <filename>bar.service
</filename> as configured with
<varname>Wants=
</varname> and no ordering is
607 configured with
<varname>After=
</varname> or
<varname>Before=
</varname>, then both units will be
608 started simultaneously and without any delay between them if
<filename>foo.service
</filename> is
609 activated.
</para></listitem>
613 <term><varname>Requires=
</varname></term>
615 <listitem><para>Similar to
<varname>Wants=
</varname>, but declares a stronger
616 dependency. Dependencies of this type may also be configured by adding a symlink to a
617 <filename>.requires/
</filename> directory accompanying the unit file.
</para>
619 <para>If this unit gets activated, the units listed will be activated as well. If one of
620 the other units fails to activate, and an ordering dependency
<varname>After=
</varname> on the
621 failing unit is set, this unit will not be started. Besides, with or without specifying
622 <varname>After=
</varname>, this unit will be stopped if one of the other units is explicitly
625 <para>Often, it is a better choice to use
<varname>Wants=
</varname> instead of
626 <varname>Requires=
</varname> in order to achieve a system that is more robust when dealing with
627 failing services.
</para>
629 <para>Note that this dependency type does not imply that the other unit always has to be in active state when
630 this unit is running. Specifically: failing condition checks (such as
<varname>ConditionPathExists=
</varname>,
631 <varname>ConditionPathIsSymbolicLink=
</varname>, … — see below) do not cause the start job of a unit with a
632 <varname>Requires=
</varname> dependency on it to fail. Also, some unit types may deactivate on their own (for
633 example, a service process may decide to exit cleanly, or a device may be unplugged by the user), which is not
634 propagated to units having a
<varname>Requires=
</varname> dependency. Use the
<varname>BindsTo=
</varname>
635 dependency type together with
<varname>After=
</varname> to ensure that a unit may never be in active state
636 without a specific other unit also in active state (see below).
</para></listitem>
640 <term><varname>Requisite=
</varname></term>
642 <listitem><para>Similar to
<varname>Requires=
</varname>. However, if the units listed here
643 are not started already, they will not be started and the starting of this unit will fail
644 immediately.
<varname>Requisite=
</varname> does not imply an ordering dependency, even if
645 both units are started in the same transaction. Hence this setting should usually be
646 combined with
<varname>After=
</varname>, to ensure this unit is not started before the other
649 <para>When
<varname>Requisite=b.service
</varname> is used on
650 <filename>a.service
</filename>, this dependency will show as
651 <varname>RequisiteOf=a.service
</varname> in property listing of
652 <filename>b.service
</filename>.
<varname>RequisiteOf=
</varname>
653 dependency cannot be specified directly.
</para>
658 <term><varname>BindsTo=
</varname></term>
660 <listitem><para>Configures requirement dependencies, very similar in style to
661 <varname>Requires=
</varname>. However, this dependency type is stronger: in addition to the effect of
662 <varname>Requires=
</varname> it declares that if the unit bound to is stopped, this unit will be stopped
663 too. This means a unit bound to another unit that suddenly enters inactive state will be stopped too.
664 Units can suddenly, unexpectedly enter inactive state for different reasons: the main process of a service unit
665 might terminate on its own choice, the backing device of a device unit might be unplugged or the mount point of
666 a mount unit might be unmounted without involvement of the system and service manager.
</para>
668 <para>When used in conjunction with
<varname>After=
</varname> on the same unit the behaviour of
669 <varname>BindsTo=
</varname> is even stronger. In this case, the unit bound to strictly has to be in active
670 state for this unit to also be in active state. This not only means a unit bound to another unit that suddenly
671 enters inactive state, but also one that is bound to another unit that gets skipped due to a failed condition
672 check (such as
<varname>ConditionPathExists=
</varname>,
<varname>ConditionPathIsSymbolicLink=
</varname>, … —
673 see below) will be stopped, should it be running. Hence, in many cases it is best to combine
674 <varname>BindsTo=
</varname> with
<varname>After=
</varname>.
</para>
676 <para>When
<varname>BindsTo=b.service
</varname> is used on
677 <filename>a.service
</filename>, this dependency will show as
678 <varname>BoundBy=a.service
</varname> in property listing of
679 <filename>b.service
</filename>.
<varname>BoundBy=
</varname>
680 dependency cannot be specified directly.
</para>
685 <term><varname>PartOf=
</varname></term>
687 <listitem><para>Configures dependencies similar to
688 <varname>Requires=
</varname>, but limited to stopping and
689 restarting of units. When systemd stops or restarts the units
690 listed here, the action is propagated to this unit. Note that
691 this is a one-way dependency — changes to this unit do not
692 affect the listed units.
</para>
694 <para>When
<varname>PartOf=b.service
</varname> is used on
695 <filename>a.service
</filename>, this dependency will show as
696 <varname>ConsistsOf=a.service
</varname> in property listing of
697 <filename>b.service
</filename>.
<varname>ConsistsOf=
</varname>
698 dependency cannot be specified directly.
</para>
703 <term><varname>Conflicts=
</varname></term>
705 <listitem><para>A space-separated list of unit names. Configures negative requirement
706 dependencies. If a unit has a
<varname>Conflicts=
</varname> setting on another unit, starting the
707 former will stop the latter and vice versa.
</para>
709 <para>Note that this setting does not imply an ordering dependency, similarly to the
710 <varname>Wants=
</varname> and
<varname>Requires=
</varname> dependencies described above. This means
711 that to ensure that the conflicting unit is stopped before the other unit is started, an
712 <varname>After=
</varname> or
<varname>Before=
</varname> dependency must be declared. It doesn't
713 matter which of the two ordering dependencies is used, because stop jobs are always ordered before
714 start jobs, see the discussion in
<varname>Before=
</varname>/
<varname>After=
</varname> below.
</para>
716 <para>If unit A that conflicts with unit B is scheduled to
717 be started at the same time as B, the transaction will either
718 fail (in case both are required parts of the transaction) or be
719 modified to be fixed (in case one or both jobs are not a
720 required part of the transaction). In the latter case, the job
721 that is not required will be removed, or in case both are
722 not required, the unit that conflicts will be started and the
723 unit that is conflicted is stopped.
</para></listitem>
727 <term><varname>Before=
</varname></term>
728 <term><varname>After=
</varname></term>
730 <listitem><para>These two settings expect a space-separated list of unit names. They may be specified
731 more than once, in which case dependencies for all listed names are created.
</para>
733 <para>Those two setttings configure ordering dependencies between units. If unit
734 <filename>foo.service
</filename> contains the setting
<option>Before=bar.service
</option> and both
735 units are being started,
<filename>bar.service
</filename>'s start-up is delayed until
736 <filename>foo.service
</filename> has finished starting up.
<varname>After=
</varname> is the inverse
737 of
<varname>Before=
</varname>, i.e. while
<varname>Before=
</varname> ensures that the configured unit
738 is started before the listed unit begins starting up,
<varname>After=
</varname> ensures the opposite,
739 that the listed unit is fully started up before the configured unit is started.
</para>
741 <para>When two units with an ordering dependency between them are shut down, the inverse of the
742 start-up order is applied. i.e. if a unit is configured with
<varname>After=
</varname> on another
743 unit, the former is stopped before the latter if both are shut down. Given two units with any
744 ordering dependency between them, if one unit is shut down and the other is started up, the shutdown
745 is ordered before the start-up. It doesn't matter if the ordering dependency is
746 <varname>After=
</varname> or
<varname>Before=
</varname>, in this case. It also doesn't matter which
747 of the two is shut down, as long as one is shut down and the other is started up; the shutdown is
748 ordered before the start-up in all cases. If two units have no ordering dependencies between them,
749 they are shut down or started up simultaneously, and no ordering takes place. It depends on the unit
750 type when precisely a unit has finished starting up. Most importantly, for service units start-up is
751 considered completed for the purpose of
<varname>Before=
</varname>/
<varname>After=
</varname> when all
752 its configured start-up commands have been invoked and they either failed or reported start-up
755 <para>Note that those settings are independent of and orthogonal to the requirement dependencies as
756 configured by
<varname>Requires=
</varname>,
<varname>Wants=
</varname>,
<varname>Requisite=
</varname>,
757 or
<varname>BindsTo=
</varname>. It is a common pattern to include a unit name in both the
758 <varname>After=
</varname> and
<varname>Wants=
</varname> options, in which case the unit listed will
759 be started before the unit that is configured with these options.
</para>
761 <para>Note that
<varname>Before=
</varname> dependencies on device units have no effect and are not
762 supported. Devices generally become available as a result of an external hotplug event, and systemd
763 creates the corresponding device unit without delay.
</para></listitem>
767 <term><varname>OnFailure=
</varname></term>
769 <listitem><para>A space-separated list of one or more units
770 that are activated when this unit enters the
771 <literal>failed
</literal> state. A service unit using
772 <varname>Restart=
</varname> enters the failed state only after
773 the start limits are reached.
</para></listitem>
777 <term><varname>PropagatesReloadTo=
</varname></term>
778 <term><varname>ReloadPropagatedFrom=
</varname></term>
780 <listitem><para>A space-separated list of one or more units
781 where reload requests on this unit will be propagated to, or
782 reload requests on the other unit will be propagated to this
783 unit, respectively. Issuing a reload request on a unit will
784 automatically also enqueue a reload request on all units that
785 the reload request shall be propagated to via these two
786 settings.
</para></listitem>
790 <term><varname>JoinsNamespaceOf=
</varname></term>
792 <listitem><para>For units that start processes (such as service units), lists one or more other units
793 whose network and/or temporary file namespace to join. This only applies to unit types which support
794 the
<varname>PrivateNetwork=
</varname>,
<varname>NetworkNamespacePath=
</varname> and
795 <varname>PrivateTmp=
</varname> directives (see
796 <citerefentry><refentrytitle>systemd.exec
</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
797 details). If a unit that has this setting set is started, its processes will see the same
798 <filename>/tmp
</filename>,
<filename>/var/tmp
</filename> and network namespace as one listed unit
799 that is started. If multiple listed units are already started, it is not defined which namespace is
800 joined. Note that this setting only has an effect if
801 <varname>PrivateNetwork=
</varname>/
<varname>NetworkNamespacePath=
</varname> and/or
802 <varname>PrivateTmp=
</varname> is enabled for both the unit that joins the namespace and the unit
803 whose namespace is joined.
</para></listitem>
807 <term><varname>RequiresMountsFor=
</varname></term>
809 <listitem><para>Takes a space-separated list of absolute
810 paths. Automatically adds dependencies of type
811 <varname>Requires=
</varname> and
<varname>After=
</varname> for
812 all mount units required to access the specified path.
</para>
814 <para>Mount points marked with
<option>noauto
</option> are not
815 mounted automatically through
<filename>local-fs.target
</filename>,
816 but are still honored for the purposes of this option, i.e. they
817 will be pulled in by this unit.
</para></listitem>
821 <term><varname>OnFailureJobMode=
</varname></term>
823 <listitem><para>Takes a value of
824 <literal>fail
</literal>,
825 <literal>replace
</literal>,
826 <literal>replace-irreversibly
</literal>,
827 <literal>isolate
</literal>,
828 <literal>flush
</literal>,
829 <literal>ignore-dependencies
</literal> or
830 <literal>ignore-requirements
</literal>. Defaults to
831 <literal>replace
</literal>. Specifies how the units listed in
832 <varname>OnFailure=
</varname> will be enqueued. See
833 <citerefentry><refentrytitle>systemctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
834 <option>--job-mode=
</option> option for details on the
835 possible values. If this is set to
<literal>isolate
</literal>,
836 only a single unit may be listed in
837 <varname>OnFailure=
</varname>..
</para></listitem>
841 <term><varname>IgnoreOnIsolate=
</varname></term>
843 <listitem><para>Takes a boolean argument. If
<option>true
</option>, this unit
844 will not be stopped when isolating another unit. Defaults to
845 <option>false
</option> for service, target, socket, busname, timer, and path
846 units, and
<option>true
</option> for slice, scope, device, swap, mount, and
847 automount units.
</para></listitem>
851 <term><varname>StopWhenUnneeded=
</varname></term>
853 <listitem><para>Takes a boolean argument. If
854 <option>true
</option>, this unit will be stopped when it is no
855 longer used. Note that, in order to minimize the work to be
856 executed, systemd will not stop units by default unless they
857 are conflicting with other units, or the user explicitly
858 requested their shut down. If this option is set, a unit will
859 be automatically cleaned up if no other active unit requires
860 it. Defaults to
<option>false
</option>.
</para></listitem>
864 <term><varname>RefuseManualStart=
</varname></term>
865 <term><varname>RefuseManualStop=
</varname></term>
867 <listitem><para>Takes a boolean argument. If
868 <option>true
</option>, this unit can only be activated or
869 deactivated indirectly. In this case, explicit start-up or
870 termination requested by the user is denied, however if it is
871 started or stopped as a dependency of another unit, start-up
872 or termination will succeed. This is mostly a safety feature
873 to ensure that the user does not accidentally activate units
874 that are not intended to be activated explicitly, and not
875 accidentally deactivate units that are not intended to be
876 deactivated. These options default to
877 <option>false
</option>.
</para></listitem>
881 <term><varname>AllowIsolate=
</varname></term>
883 <listitem><para>Takes a boolean argument. If
884 <option>true
</option>, this unit may be used with the
885 <command>systemctl isolate
</command> command. Otherwise, this
886 will be refused. It probably is a good idea to leave this
887 disabled except for target units that shall be used similar to
888 runlevels in SysV init systems, just as a precaution to avoid
889 unusable system states. This option defaults to
890 <option>false
</option>.
</para></listitem>
894 <term><varname>DefaultDependencies=
</varname></term>
896 <listitem><para>Takes a boolean argument. If
897 <option>yes
</option>, (the default), a few default
898 dependencies will implicitly be created for the unit. The
899 actual dependencies created depend on the unit type. For
900 example, for service units, these dependencies ensure that the
901 service is started only after basic system initialization is
902 completed and is properly terminated on system shutdown. See
903 the respective man pages for details. Generally, only services
904 involved with early boot or late shutdown should set this
905 option to
<option>no
</option>. It is highly recommended to
906 leave this option enabled for the majority of common units. If
907 set to
<option>no
</option>, this option does not disable
908 all implicit dependencies, just non-essential
909 ones.
</para></listitem>
913 <term><varname>CollectMode=
</varname></term>
915 <listitem><para>Tweaks the
"garbage collection" algorithm for this unit. Takes one of
<option>inactive
</option>
916 or
<option>inactive-or-failed
</option>. If set to
<option>inactive
</option> the unit will be unloaded if it is
917 in the
<constant>inactive
</constant> state and is not referenced by clients, jobs or other units — however it
918 is not unloaded if it is in the
<constant>failed
</constant> state. In
<option>failed
</option> mode, failed
919 units are not unloaded until the user invoked
<command>systemctl reset-failed
</command> on them to reset the
920 <constant>failed
</constant> state, or an equivalent command. This behaviour is altered if this option is set to
921 <option>inactive-or-failed
</option>: in this case the unit is unloaded even if the unit is in a
922 <constant>failed
</constant> state, and thus an explicitly resetting of the
<constant>failed
</constant> state is
923 not necessary. Note that if this mode is used unit results (such as exit codes, exit signals, consumed
924 resources, …) are flushed out immediately after the unit completed, except for what is stored in the logging
925 subsystem. Defaults to
<option>inactive
</option>.
</para>
930 <term><varname>FailureAction=
</varname></term>
931 <term><varname>SuccessAction=
</varname></term>
933 <listitem><para>Configure the action to take when the unit stops and enters a failed state or inactive state.
934 Takes one of
<option>none
</option>,
<option>reboot
</option>,
<option>reboot-force
</option>,
935 <option>reboot-immediate
</option>,
<option>poweroff
</option>,
<option>poweroff-force
</option>,
936 <option>poweroff-immediate
</option>,
<option>exit
</option>, and
<option>exit-force
</option>. In system mode,
937 all options are allowed. In user mode, only
<option>none
</option>,
<option>exit
</option>, and
938 <option>exit-force
</option> are allowed. Both options default to
<option>none
</option>.
</para>
940 <para>If
<option>none
</option> is set, no action will be triggered.
<option>reboot
</option> causes a reboot
941 following the normal shutdown procedure (i.e. equivalent to
<command>systemctl reboot
</command>).
942 <option>reboot-force
</option> causes a forced reboot which will terminate all processes forcibly but should
943 cause no dirty file systems on reboot (i.e. equivalent to
<command>systemctl reboot -f
</command>) and
944 <option>reboot-immediate
</option> causes immediate execution of the
945 <citerefentry><refentrytitle>reboot
</refentrytitle><manvolnum>2</manvolnum></citerefentry> system call, which
946 might result in data loss (i.e. equivalent to
<command>systemctl reboot -ff
</command>). Similarly,
947 <option>poweroff
</option>,
<option>poweroff-force
</option>,
<option>poweroff-immediate
</option> have the effect
948 of powering down the system with similar semantics.
<option>exit
</option> causes the manager to exit following
949 the normal shutdown procedure, and
<option>exit-force
</option> causes it terminate without shutting down
950 services. When
<option>exit
</option> or
<option>exit-force
</option> is used by default the exit status of the
951 main process of the unit (if this applies) is returned from the service manager. However, this may be overridden
952 with
<varname>FailureActionExitStatus=
</varname>/
<varname>SuccessActionExitStatus=
</varname>, see
953 below.
</para></listitem>
957 <term><varname>FailureActionExitStatus=
</varname></term>
958 <term><varname>SuccessActionExitStatus=
</varname></term>
960 <listitem><para>Controls the exit status to propagate back to an invoking container manager (in case of a
961 system service) or service manager (in case of a user manager) when the
962 <varname>FailureAction=
</varname>/
<varname>SuccessAction=
</varname> are set to
<option>exit
</option> or
963 <option>exit-force
</option> and the action is triggered. By default the exit status of the main process of the
964 triggering unit (if this applies) is propagated. Takes a value in the range
0…
255 or the empty string to
965 request default behaviour.
</para></listitem>
969 <term><varname>JobTimeoutSec=
</varname></term>
970 <term><varname>JobRunningTimeoutSec=
</varname></term>
972 <listitem><para>When a job for this unit is queued, a timeout
<varname>JobTimeoutSec=
</varname> may be
973 configured. Similarly,
<varname>JobRunningTimeoutSec=
</varname> starts counting when the queued job is actually
974 started. If either time limit is reached, the job will be cancelled, the unit however will not change state or
975 even enter the
<literal>failed
</literal> mode. This value defaults to
<literal>infinity
</literal> (job timeouts
976 disabled), except for device units (
<varname>JobRunningTimeoutSec=
</varname> defaults to
977 <varname>DefaultTimeoutStartSec=
</varname>). NB: this timeout is independent from any unit-specific timeout
978 (for example, the timeout set with
<varname>TimeoutStartSec=
</varname> in service units) as the job timeout has
979 no effect on the unit itself, only on the job that might be pending for it. Or in other words: unit-specific
980 timeouts are useful to abort unit state changes, and revert them. The job timeout set with this option however
981 is useful to abort only the job waiting for the unit state to change.
</para>
986 <term><varname>JobTimeoutAction=
</varname></term>
987 <term><varname>JobTimeoutRebootArgument=
</varname></term>
989 <listitem><para><varname>JobTimeoutAction=
</varname> optionally configures an additional action to take when
990 the timeout is hit, see description of
<varname>JobTimeoutSec=
</varname> and
991 <varname>JobRunningTimeoutSec=
</varname> above. It takes the same values as
992 <varname>StartLimitAction=
</varname>. Defaults to
<option>none
</option>.
993 <varname>JobTimeoutRebootArgument=
</varname> configures an optional reboot string to pass to the
994 <citerefentry><refentrytitle>reboot
</refentrytitle><manvolnum>2</manvolnum></citerefentry> system call.
999 <term><varname>StartLimitIntervalSec=
<replaceable>interval
</replaceable></varname></term>
1000 <term><varname>StartLimitBurst=
<replaceable>burst
</replaceable></varname></term>
1002 <listitem><para>Configure unit start rate limiting. Units which are started more than
1003 <replaceable>burst
</replaceable> times within an
<replaceable>interval
</replaceable> time interval are not
1004 permitted to start any more. Use
<varname>StartLimitIntervalSec=
</varname> to configure the checking interval
1005 (defaults to
<varname>DefaultStartLimitIntervalSec=
</varname> in manager configuration file, set it to
0 to
1006 disable any kind of rate limiting). Use
<varname>StartLimitBurst=
</varname> to configure how many starts per
1007 interval are allowed (defaults to
<varname>DefaultStartLimitBurst=
</varname> in manager configuration
1008 file). These configuration options are particularly useful in conjunction with the service setting
1009 <varname>Restart=
</varname> (see
1010 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>); however,
1011 they apply to all kinds of starts (including manual), not just those triggered by the
1012 <varname>Restart=
</varname> logic. Note that units which are configured for
<varname>Restart=
</varname> and
1013 which reach the start limit are not attempted to be restarted anymore; however, they may still be restarted
1014 manually at a later point, after the
<replaceable>interval
</replaceable> has passed. From this point on, the
1015 restart logic is activated again. Note that
<command>systemctl reset-failed
</command> will cause the restart
1016 rate counter for a service to be flushed, which is useful if the administrator wants to manually start a unit
1017 and the start limit interferes with that. Note that this rate-limiting is enforced after any unit condition
1018 checks are executed, and hence unit activations with failing conditions do not count towards this rate
1019 limit. This setting does not apply to slice, target, device, and scope units, since they are unit types whose
1020 activation may either never fail, or may succeed only a single time.
</para>
1022 <para>When a unit is unloaded due to the garbage collection logic (see above) its rate limit counters are
1023 flushed out too. This means that configuring start rate limiting for a unit that is not referenced continuously
1024 has no effect.
</para></listitem>
1028 <term><varname>StartLimitAction=
</varname></term>
1030 <listitem><para>Configure an additional action to take if the rate limit configured with
1031 <varname>StartLimitIntervalSec=
</varname> and
<varname>StartLimitBurst=
</varname> is hit. Takes the same
1032 values as the setting
<varname>FailureAction=
</varname>/
<varname>SuccessAction=
</varname> settings and executes
1033 the same actions. If
<option>none
</option> is set, hitting the rate limit will trigger no action besides that
1034 the start will not be permitted. Defaults to
<option>none
</option>.
</para></listitem>
1038 <term><varname>RebootArgument=
</varname></term>
1039 <listitem><para>Configure the optional argument for the
1040 <citerefentry><refentrytitle>reboot
</refentrytitle><manvolnum>2</manvolnum></citerefentry> system call if
1041 <varname>StartLimitAction=
</varname> or
<varname>FailureAction=
</varname> is a reboot action. This
1042 works just like the optional argument to
<command>systemctl reboot
</command> command.
</para></listitem>
1046 <term><varname>SourcePath=
</varname></term>
1047 <listitem><para>A path to a configuration file this unit has
1048 been generated from. This is primarily useful for
1049 implementation of generator tools that convert configuration
1050 from an external configuration file format into native unit
1051 files. This functionality should not be used in normal
1052 units.
</para></listitem>
1057 <title>Conditions and Asserts
</title>
1059 <para>Unit files may also include a number of
<varname index=
"false">Condition…=
</varname> and
1060 <varname index=
"false">Assert…=
</varname> settings. Before the unit is started, systemd will verify
1061 that the specified conditions are true. If not, the starting of the unit will be (mostly silently)
1062 skipped. Failing conditions will not result in the unit being moved into the
<literal>failed
</literal>
1063 state. The conditions are checked at the time the queued start job is to be executed. The ordering
1064 dependencies are still respected, so other units are still pulled in and ordered as if this unit was
1065 successfully activated. Use condition expressions in order to skip units that do not apply to the local
1066 system, for example because the kernel or runtime environment doesn't require their functionality.
1069 <para>If multiple conditions are specified, the unit will be executed if all of them apply (i.e. a
1070 logical AND is applied). Condition checks can use a pipe symbol (
<literal>|
</literal>) after the equals
1071 sign (
<literal>Condition…=|…
</literal>), which causes the condition becomes a triggering condition. If
1072 at least one triggering condition is defined for a unit, then the unit will be executed if at least one
1073 of the triggering conditions apply and all of the non-triggering conditions. If you prefix an argument
1074 with the pipe symbol and an exclamation mark, the pipe symbol must be passed first, the exclamation
1075 second. If any of these options is assigned the empty string, the list of conditions is reset
1076 completely, all previous condition settings (of any kind) will have no effect.
</para>
1078 <para>The
<varname>AssertArchitecture=
</varname>,
<varname>AssertVirtualization=
</varname>, … options
1079 provide a similar mechanism that causes the job to fail (instead of being skipped). The failed check is
1080 logged. Units with failed conditions are considered to be in a clean state and will be garbage
1081 collected if they are not referenced. This means that when queried, the condition failure may or may
1082 not show up in the state of the unit.
</para>
1084 <para>Note that neither assertion nor condition expressions result in unit state changes. Also note
1085 that both are checked at the time the job is to be executed, i.e. long after depending jobs and it
1086 itself were queued. Thus, neither condition nor assertion expressions are suitable for conditionalizing
1087 unit dependencies.
</para>
1089 <para>The
<command>condition
</command> verb of
1090 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry> can
1091 be used to test condition and assert expressions.
</para>
1093 <para>Except for
<varname>ConditionPathIsSymbolicLink=
</varname>, all path checks follow symlinks.
</para>
1095 <variablelist class='unit-directives'
>
1096 <!-- We do not document ConditionNull= here, as it is not particularly useful and probably just
1100 <term><varname>ConditionArchitecture=
</varname></term>
1102 <listitem><para>Check whether the system is running on a specific architecture. Takes one of
1103 <literal>x86
</literal>,
1104 <literal>x86-
64</literal>,
1105 <literal>ppc
</literal>,
1106 <literal>ppc-le
</literal>,
1107 <literal>ppc64
</literal>,
1108 <literal>ppc64-le
</literal>,
1109 <literal>ia64
</literal>,
1110 <literal>parisc
</literal>,
1111 <literal>parisc64
</literal>,
1112 <literal>s390
</literal>,
1113 <literal>s390x
</literal>,
1114 <literal>sparc
</literal>,
1115 <literal>sparc64
</literal>,
1116 <literal>mips
</literal>,
1117 <literal>mips-le
</literal>,
1118 <literal>mips64
</literal>,
1119 <literal>mips64-le
</literal>,
1120 <literal>alpha
</literal>,
1121 <literal>arm
</literal>,
1122 <literal>arm-be
</literal>,
1123 <literal>arm64
</literal>,
1124 <literal>arm64-be
</literal>,
1125 <literal>sh
</literal>,
1126 <literal>sh64
</literal>,
1127 <literal>m68k
</literal>,
1128 <literal>tilegx
</literal>,
1129 <literal>cris
</literal>,
1130 <literal>arc
</literal>,
1131 <literal>arc-be
</literal>, or
1132 <literal>native
</literal>.
</para>
1134 <para>The architecture is determined from the information returned by
1135 <citerefentry project='man-pages'
><refentrytitle>uname
</refentrytitle><manvolnum>2</manvolnum></citerefentry>
1136 and is thus subject to
1137 <citerefentry><refentrytitle>personality
</refentrytitle><manvolnum>2</manvolnum></citerefentry>.
1138 Note that a
<varname>Personality=
</varname> setting in the same unit file has no effect on this
1139 condition. A special architecture name
<literal>native
</literal> is mapped to the architecture the
1140 system manager itself is compiled for. The test may be negated by prepending an exclamation
1146 <term><varname>ConditionVirtualization=
</varname></term>
1148 <listitem><para>Check whether the system is executed in a virtualized environment and optionally
1149 test whether it is a specific implementation. Takes either boolean value to check if being executed
1150 in any virtualized environment, or one of
1151 <literal>vm
</literal> and
1152 <literal>container
</literal> to test against a generic type of virtualization solution, or one of
1153 <literal>qemu
</literal>,
1154 <literal>kvm
</literal>,
1155 <literal>zvm
</literal>,
1156 <literal>vmware
</literal>,
1157 <literal>microsoft
</literal>,
1158 <literal>oracle
</literal>,
1159 <literal>xen
</literal>,
1160 <literal>bochs
</literal>,
1161 <literal>uml
</literal>,
1162 <literal>bhyve
</literal>,
1163 <literal>qnx
</literal>,
1164 <literal>openvz
</literal>,
1165 <literal>lxc
</literal>,
1166 <literal>lxc-libvirt
</literal>,
1167 <literal>systemd-nspawn
</literal>,
1168 <literal>docker
</literal>,
1169 <literal>podman
</literal>,
1170 <literal>rkt
</literal>,
1171 <literal>wsl
</literal>,
1172 <literal>acrn
</literal> to test
1173 against a specific implementation, or
1174 <literal>private-users
</literal> to check whether we are running in a user namespace. See
1175 <citerefentry><refentrytitle>systemd-detect-virt
</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1176 for a full list of known virtualization technologies and their identifiers. If multiple
1177 virtualization technologies are nested, only the innermost is considered. The test may be negated
1178 by prepending an exclamation mark.
</para>
1183 <term><varname>ConditionHost=
</varname></term>
1185 <listitem><para><varname>ConditionHost=
</varname> may be used to match against the hostname or
1186 machine ID of the host. This either takes a hostname string (optionally with shell style globs)
1187 which is tested against the locally set hostname as returned by
1188 <citerefentry><refentrytitle>gethostname
</refentrytitle><manvolnum>2</manvolnum></citerefentry>, or
1189 a machine ID formatted as string (see
1190 <citerefentry><refentrytitle>machine-id
</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
1191 The test may be negated by prepending an exclamation mark.
</para>
1196 <term><varname>ConditionKernelCommandLine=
</varname></term>
1198 <listitem><para><varname>ConditionKernelCommandLine=
</varname> may be used to check whether a
1199 specific kernel command line option is set (or if prefixed with the exclamation mark — unset). The
1200 argument must either be a single word, or an assignment (i.e. two words, separated by
1201 <literal>=
</literal>). In the former case the kernel command line is searched for the word
1202 appearing as is, or as left hand side of an assignment. In the latter case, the exact assignment is
1203 looked for with right and left hand side matching.
</para>
1208 <term><varname>ConditionKernelVersion=
</varname></term>
1210 <listitem><para><varname>ConditionKernelVersion=
</varname> may be used to check whether the kernel
1211 version (as reported by
<command>uname -r
</command>) matches a certain expression (or if prefixed
1212 with the exclamation mark does not match it). The argument must be a list of (potentially quoted)
1213 expressions. For each of the expressions, if it starts with one of
<literal><</literal>,
1214 <literal><=
</literal>,
<literal>=
</literal>,
<literal>!=
</literal>,
<literal>>=
</literal>,
1215 <literal>></literal> a relative version comparison is done, otherwise the specified string is
1216 matched with shell-style globs.
</para>
1218 <para>Note that using the kernel version string is an unreliable way to determine which features
1219 are supported by a kernel, because of the widespread practice of backporting drivers, features, and
1220 fixes from newer upstream kernels into older versions provided by distributions. Hence, this check
1221 is inherently unportable and should not be used for units which may be used on different
1222 distributions.
</para>
1227 <term><varname>ConditionSecurity=
</varname></term>
1229 <listitem><para><varname>ConditionSecurity=
</varname> may be used to check whether the given
1230 security technology is enabled on the system. Currently, the recognized values are
1231 <literal>selinux
</literal>,
<literal>apparmor
</literal>,
<literal>tomoyo
</literal>,
1232 <literal>ima
</literal>,
<literal>smack
</literal>,
<literal>audit
</literal> and
1233 <literal>uefi-secureboot
</literal>. The test may be negated by prepending an exclamation
1239 <term><varname>ConditionCapability=
</varname></term>
1241 <listitem><para>Check whether the given capability exists in the capability bounding set of the
1242 service manager (i.e. this does not check whether capability is actually available in the permitted
1243 or effective sets, see
1244 <citerefentry project='man-pages'
><refentrytitle>capabilities
</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1245 for details). Pass a capability name such as
<literal>CAP_MKNOD
</literal>, possibly prefixed with
1246 an exclamation mark to negate the check.
</para>
1251 <term><varname>ConditionACPower=
</varname></term>
1253 <listitem><para>Check whether the system has AC power, or is exclusively battery powered at the
1254 time of activation of the unit. This takes a boolean argument. If set to
<literal>true
</literal>,
1255 the condition will hold only if at least one AC connector of the system is connected to a power
1256 source, or if no AC connectors are known. Conversely, if set to
<literal>false
</literal>, the
1257 condition will hold only if there is at least one AC connector known and all AC connectors are
1258 disconnected from a power source.
</para>
1263 <term><varname>ConditionNeedsUpdate=
</varname></term>
1265 <listitem><para>Takes one of
<filename>/var
</filename> or
<filename>/etc
</filename> as argument,
1266 possibly prefixed with a
<literal>!
</literal> (to inverting the condition). This condition may be
1267 used to conditionalize units on whether the specified directory requires an update because
1268 <filename>/usr
</filename>'s modification time is newer than the stamp file
1269 <filename>.updated
</filename> in the specified directory. This is useful to implement offline
1270 updates of the vendor operating system resources in
<filename>/usr
</filename> that require updating
1271 of
<filename>/etc
</filename> or
<filename>/var
</filename> on the next following boot. Units making
1272 use of this condition should order themselves before
1273 <citerefentry><refentrytitle>systemd-update-done.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1274 to make sure they run before the stamp file's modification time gets reset indicating a completed
1280 <term><varname>ConditionFirstBoot=
</varname></term>
1282 <listitem><para>Takes a boolean argument. This condition may be used to conditionalize units on
1283 whether the system is booting up with an unpopulated
<filename>/etc
</filename> directory
1284 (specifically: an
<filename>/etc
</filename> with no
<filename>/etc/machine-id
</filename>). This may
1285 be used to populate
<filename>/etc
</filename> on the first boot after factory reset, or when a new
1286 system instance boots up for the first time.
</para>
1291 <term><varname>ConditionPathExists=
</varname></term>
1293 <listitem><para>Check for the exists of a file. If the specified absolute path name does not exist,
1294 the condition will fail. If the absolute path name passed to
1295 <varname>ConditionPathExists=
</varname> is prefixed with an exclamation mark
1296 (
<literal>!
</literal>), the test is negated, and the unit is only started if the path does not
1302 <term><varname>ConditionPathExistsGlob=
</varname></term>
1304 <listitem><para><varname>ConditionPathExistsGlob=
</varname> is similar to
1305 <varname>ConditionPathExists=
</varname>, but checks for the existence of at least one file or
1306 directory matching the specified globbing pattern.
</para>
1311 <term><varname>ConditionPathIsDirectory=
</varname></term>
1313 <listitem><para><varname>ConditionPathIsDirectory=
</varname> is similar to
1314 <varname>ConditionPathExists=
</varname> but verifies that a certain path exists and is a
1320 <term><varname>ConditionPathIsSymbolicLink=
</varname></term>
1322 <listitem><para><varname>ConditionPathIsSymbolicLink=
</varname> is similar to
1323 <varname>ConditionPathExists=
</varname> but verifies that a certain path exists and is a symbolic
1329 <term><varname>ConditionPathIsMountPoint=
</varname></term>
1331 <listitem><para><varname>ConditionPathIsMountPoint=
</varname> is similar to
1332 <varname>ConditionPathExists=
</varname> but verifies that a certain path exists and is a mount
1338 <term><varname>ConditionPathIsReadWrite=
</varname></term>
1340 <listitem><para><varname>ConditionPathIsReadWrite=
</varname> is similar to
1341 <varname>ConditionPathExists=
</varname> but verifies that the underlying file system is readable
1342 and writable (i.e. not mounted read-only).
</para>
1347 <term><varname>ConditionDirectoryNotEmpty=
</varname></term>
1349 <listitem><para><varname>ConditionDirectoryNotEmpty=
</varname> is similar to
1350 <varname>ConditionPathExists=
</varname> but verifies that a certain path exists and is a non-empty
1356 <term><varname>ConditionFileNotEmpty=
</varname></term>
1358 <listitem><para><varname>ConditionFileNotEmpty=
</varname> is similar to
1359 <varname>ConditionPathExists=
</varname> but verifies that a certain path exists and refers to a
1360 regular file with a non-zero size.
</para>
1365 <term><varname>ConditionFileIsExecutable=
</varname></term>
1367 <listitem><para><varname>ConditionFileIsExecutable=
</varname> is similar to
1368 <varname>ConditionPathExists=
</varname> but verifies that a certain path exists, is a regular file,
1369 and marked executable.
</para>
1374 <term><varname>ConditionUser=
</varname></term>
1376 <listitem><para><varname>ConditionUser=
</varname> takes a numeric
<literal>UID
</literal>, a UNIX
1377 user name, or the special value
<literal>@system
</literal>. This condition may be used to check
1378 whether the service manager is running as the given user. The special value
1379 <literal>@system
</literal> can be used to check if the user id is within the system user
1380 range. This option is not useful for system services, as the system manager exclusively runs as the
1381 root user, and thus the test result is constant.
</para>
1386 <term><varname>ConditionGroup=
</varname></term>
1388 <listitem><para><varname>ConditionGroup=
</varname> is similar to
<varname>ConditionUser=
</varname>
1389 but verifies that the service manager's real or effective group, or any of its auxiliary groups,
1390 match the specified group or GID. This setting does not support the special value
1391 <literal>@system
</literal>.
</para>
1396 <term><varname>ConditionControlGroupController=
</varname></term>
1398 <listitem><para>Verify that the given cgroup controller (eg.
<literal>cpu
</literal>) is available
1399 for use on the system. For example, a particular controller may not be available if it was disabled
1400 on the kernel command line with
<varname>cgroup_disable=controller
</varname>. Multiple controllers
1401 may be passed with a space separating them; in this case the condition will only pass if all listed
1402 controllers are available for use. Controllers unknown to systemd are ignored. Valid controllers
1403 are
<literal>cpu
</literal>,
<literal>cpuacct
</literal>,
<literal>io
</literal>,
1404 <literal>blkio
</literal>,
<literal>memory
</literal>,
<literal>devices
</literal>, and
1405 <literal>pids
</literal>.
</para>
1410 <term><varname>ConditionMemory=
</varname></term>
1412 <listitem><para>Verify that the specified amount of system memory is available to the current
1413 system. Takes a memory size in bytes as argument, optionally prefixed with a comparison operator
1414 <literal><</literal>,
<literal><=
</literal>,
<literal>=
</literal>,
<literal>!=
</literal>,
1415 <literal>>=
</literal>,
<literal>></literal>. On bare-metal systems compares the amount of
1416 physical memory in the system with the specified size, adhering to the specified comparison
1417 operator. In containers compares the amount of memory assigned to the container instead.
</para>
1422 <term><varname>ConditionCPUs=
</varname></term>
1424 <listitem><para>Verify that the specified number of CPUs is available to the current system. Takes
1425 a number of CPUs as argument, optionally prefixed with a comparison operator
1426 <literal><</literal>,
<literal><=
</literal>,
<literal>=
</literal>,
<literal>!=
</literal>,
1427 <literal>>=
</literal>,
<literal>></literal>. Compares the number of CPUs in the CPU affinity
1428 mask configured of the service manager itself with the specified number, adhering to the specified
1429 comparison operator. On physical systems the number of CPUs in the affinity mask of the service
1430 manager usually matches the number of physical CPUs, but in special and virtual environments might
1431 differ. In particular, in containers the affinity mask usually matches the number of CPUs assigned
1432 to the container and not the physically available ones.
</para></listitem>
1436 <term><varname>AssertArchitecture=
</varname></term>
1437 <term><varname>AssertVirtualization=
</varname></term>
1438 <term><varname>AssertHost=
</varname></term>
1439 <term><varname>AssertKernelCommandLine=
</varname></term>
1440 <term><varname>AssertKernelVersion=
</varname></term>
1441 <term><varname>AssertSecurity=
</varname></term>
1442 <term><varname>AssertCapability=
</varname></term>
1443 <term><varname>AssertACPower=
</varname></term>
1444 <term><varname>AssertNeedsUpdate=
</varname></term>
1445 <term><varname>AssertFirstBoot=
</varname></term>
1446 <term><varname>AssertPathExists=
</varname></term>
1447 <term><varname>AssertPathExistsGlob=
</varname></term>
1448 <term><varname>AssertPathIsDirectory=
</varname></term>
1449 <term><varname>AssertPathIsSymbolicLink=
</varname></term>
1450 <term><varname>AssertPathIsMountPoint=
</varname></term>
1451 <term><varname>AssertPathIsReadWrite=
</varname></term>
1452 <term><varname>AssertDirectoryNotEmpty=
</varname></term>
1453 <term><varname>AssertFileNotEmpty=
</varname></term>
1454 <term><varname>AssertFileIsExecutable=
</varname></term>
1455 <term><varname>AssertUser=
</varname></term>
1456 <term><varname>AssertGroup=
</varname></term>
1457 <term><varname>AssertControlGroupController=
</varname></term>
1459 <listitem><para>Similar to the
<varname>ConditionArchitecture=
</varname>,
1460 <varname>ConditionVirtualization=
</varname>, …, condition settings described above, these settings
1461 add assertion checks to the start-up of the unit. However, unlike the conditions settings, any
1462 assertion setting that is not met results in failure of the start job (which means this is logged
1463 loudly). Note that hitting a configured assertion does not cause the unit to enter the
1464 <literal>failed
</literal> state (or in fact result in any state change of the unit), it affects
1465 only the job queued for it. Use assertion expressions for units that cannot operate when specific
1466 requirements are not met, and when this is something the administrator or user should look
1475 <title>Mapping of unit properties to their inverses
</title>
1477 <para>Unit settings that create a relationship with a second unit usually show up
1478 in properties of both units, for example in
<command>systemctl show
</command>
1479 output. In some cases the name of the property is the same as the name of the
1480 configuration setting, but not always. This table lists the properties
1481 that are shown on two units which are connected through some dependency, and shows
1482 which property on
"source" unit corresponds to which property on the
"target" unit.
1487 "Forward" and
"reverse" unit properties
1491 <colspec colname='forward'
/>
1492 <colspec colname='reverse'
/>
1493 <colspec colname='fuse'
/>
1494 <colspec colname='ruse'
/>
1497 <entry>"Forward" property
</entry>
1498 <entry>"Reverse" property
</entry>
1499 <entry namest='fuse' nameend='ruse' valign='middle'
>Where used
</entry>
1504 <entry><varname>Before=
</varname></entry>
1505 <entry><varname>After=
</varname></entry>
1506 <entry morerows='
1' namest='fuse' nameend='ruse' valign='middle'
>[Unit] section
</entry>
1509 <entry><varname>After=
</varname></entry>
1510 <entry><varname>Before=
</varname></entry>
1513 <entry><varname>Requires=
</varname></entry>
1514 <entry><varname>RequiredBy=
</varname></entry>
1515 <entry>[Unit] section
</entry>
1516 <entry>[Install] section
</entry>
1519 <entry><varname>Wants=
</varname></entry>
1520 <entry><varname>WantedBy=
</varname></entry>
1521 <entry>[Unit] section
</entry>
1522 <entry>[Install] section
</entry>
1525 <entry><varname>PartOf=
</varname></entry>
1526 <entry><varname>ConsistsOf=
</varname></entry>
1527 <entry>[Unit] section
</entry>
1528 <entry>an automatic property
</entry>
1531 <entry><varname>BindsTo=
</varname></entry>
1532 <entry><varname>BoundBy=
</varname></entry>
1533 <entry>[Unit] section
</entry>
1534 <entry>an automatic property
</entry>
1537 <entry><varname>Requisite=
</varname></entry>
1538 <entry><varname>RequisiteOf=
</varname></entry>
1539 <entry>[Unit] section
</entry>
1540 <entry>an automatic property
</entry>
1543 <entry><varname>Triggers=
</varname></entry>
1544 <entry><varname>TriggeredBy=
</varname></entry>
1545 <entry namest='fuse' nameend='ruse' valign='middle'
>Automatic properties, see notes below
</entry>
1548 <entry><varname>Conflicts=
</varname></entry>
1549 <entry><varname>ConflictedBy=
</varname></entry>
1550 <entry>[Unit] section
</entry>
1551 <entry>an automatic property
</entry>
1554 <entry><varname>PropagatesReloadTo=
</varname></entry>
1555 <entry><varname>ReloadPropagatedFrom=
</varname></entry>
1556 <entry morerows='
1' namest='fuse' nameend='ruse' valign='middle'
>[Unit] section
</entry>
1559 <entry><varname>ReloadPropagatedFrom=
</varname></entry>
1560 <entry><varname>PropagatesReloadTo=
</varname></entry>
1563 <entry><varname>Following=
</varname></entry>
1565 <entry>An automatic property
</entry>
1571 <para>Note:
<varname>WantedBy=
</varname> and
<varname>RequiredBy=
</varname> are
1572 used in the [Install] section to create symlinks in
<filename>.wants/
</filename>
1573 and
<filename>.requires/
</filename> directories. They cannot be used directly as a
1574 unit configuration setting.
</para>
1576 <para>Note:
<varname>ConsistsOf=
</varname>,
<varname>BoundBy=
</varname>,
1577 <varname>RequisiteOf=
</varname>,
<varname>ConflictedBy=
</varname> are created
1578 implicitly along with their reverses and cannot be specified directly.
</para>
1580 <para>Note:
<varname>Triggers=
</varname> is created implicitly between a socket,
1581 path unit, or an automount unit, and the unit they activate. By default a unit
1582 with the same name is triggered, but this can be overridden using
1583 <varname>Sockets=
</varname>,
<varname>Service=
</varname>, and
<varname>Unit=
</varname>
1585 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1586 <citerefentry><refentrytitle>systemd.socket
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1587 <citerefentry><refentrytitle>systemd.path
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1589 <citerefentry><refentrytitle>systemd.automount
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1590 for details.
<varname>TriggeredBy=
</varname> is created implicitly on the
1591 triggered unit.
</para>
1593 <para>Note:
<varname>Following=
</varname> is used to group device aliases and points to the
1594 "primary" device unit that systemd is using to track device state, usually corresponding to a
1595 sysfs path. It does not show up in the
"target" unit.
</para>
1599 <title>[Install] Section Options
</title>
1601 <para>Unit files may include an
<literal>[Install]
</literal> section, which carries installation information for
1602 the unit. This section is not interpreted by
1603 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry> during runtime; it is
1604 used by the
<command>enable
</command> and
<command>disable
</command> commands of the
1605 <citerefentry><refentrytitle>systemctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry> tool during
1606 installation of a unit.
</para>
1608 <variablelist class='unit-directives'
>
1610 <term><varname>Alias=
</varname></term>
1612 <listitem><para>A space-separated list of additional names this unit shall be installed under. The names listed
1613 here must have the same suffix (i.e. type) as the unit filename. This option may be specified more than once,
1614 in which case all listed names are used. At installation time,
<command>systemctl enable
</command> will create
1615 symlinks from these names to the unit filename. Note that not all unit types support such alias names, and this
1616 setting is not supported for them. Specifically, mount, slice, swap, and automount units do not support
1617 aliasing.
</para></listitem>
1621 <term><varname>WantedBy=
</varname></term>
1622 <term><varname>RequiredBy=
</varname></term>
1624 <listitem><para>This option may be used more than once, or a
1625 space-separated list of unit names may be given. A symbolic
1626 link is created in the
<filename>.wants/
</filename> or
1627 <filename>.requires/
</filename> directory of each of the
1628 listed units when this unit is installed by
<command>systemctl
1629 enable
</command>. This has the effect that a dependency of
1630 type
<varname>Wants=
</varname> or
<varname>Requires=
</varname>
1631 is added from the listed unit to the current unit. The primary
1632 result is that the current unit will be started when the
1633 listed unit is started. See the description of
1634 <varname>Wants=
</varname> and
<varname>Requires=
</varname> in
1635 the [Unit] section for details.
</para>
1637 <para><command>WantedBy=foo.service
</command> in a service
1638 <filename>bar.service
</filename> is mostly equivalent to
1639 <command>Alias=foo.service.wants/bar.service
</command> in the
1640 same file. In case of template units,
<command>systemctl
1641 enable
</command> must be called with an instance name, and
1642 this instance will be added to the
1643 <filename>.wants/
</filename> or
1644 <filename>.requires/
</filename> list of the listed unit. E.g.
1645 <command>WantedBy=getty.target
</command> in a service
1646 <filename>getty@.service
</filename> will result in
1647 <command>systemctl enable getty@tty2.service
</command>
1649 <filename>getty.target.wants/getty@tty2.service
</filename>
1650 link to
<filename>getty@.service
</filename>.
1655 <term><varname>Also=
</varname></term>
1657 <listitem><para>Additional units to install/deinstall when
1658 this unit is installed/deinstalled. If the user requests
1659 installation/deinstallation of a unit with this option
1660 configured,
<command>systemctl enable
</command> and
1661 <command>systemctl disable
</command> will automatically
1662 install/uninstall units listed in this option as well.
</para>
1664 <para>This option may be used more than once, or a
1665 space-separated list of unit names may be
1666 given.
</para></listitem>
1670 <term><varname>DefaultInstance=
</varname></term>
1672 <listitem><para>In template unit files, this specifies for
1673 which instance the unit shall be enabled if the template is
1674 enabled without any explicitly set instance. This option has
1675 no effect in non-template unit files. The specified string
1676 must be usable as instance identifier.
</para></listitem>
1680 <para>The following specifiers are interpreted in the Install
1681 section: %n, %N, %p, %i, %j, %g, %G, %U, %u, %m, %H, %b, %v. For their
1682 meaning see the next section.
1687 <title>Specifiers
</title>
1689 <para>Many settings resolve specifiers which may be used to write
1690 generic unit files referring to runtime or unit parameters that
1691 are replaced when the unit files are loaded. Specifiers must be known
1692 and resolvable for the setting to be valid. The following
1693 specifiers are understood:
</para>
1696 <title>Specifiers available in unit files
</title>
1697 <tgroup cols='
3' align='left' colsep='
1' rowsep='
1'
>
1698 <colspec colname=
"spec" />
1699 <colspec colname=
"mean" />
1700 <colspec colname=
"detail" />
1703 <entry>Specifier
</entry>
1704 <entry>Meaning
</entry>
1705 <entry>Details
</entry>
1710 <entry><literal>%b
</literal></entry>
1711 <entry>Boot ID
</entry>
1712 <entry>The boot ID of the running system, formatted as string. See
<citerefentry><refentrytitle>random
</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.
</entry>
1715 <entry><literal>%C
</literal></entry>
1716 <entry>Cache directory root
</entry>
1717 <entry>This is either
<filename>/var/cache
</filename> (for the system manager) or the path
<literal>$XDG_CACHE_HOME
</literal> resolves to (for user managers).
</entry>
1720 <entry><literal>%E
</literal></entry>
1721 <entry>Configuration directory root
</entry>
1722 <entry>This is either
<filename>/etc
</filename> (for the system manager) or the path
<literal>$XDG_CONFIG_HOME
</literal> resolves to (for user managers).
</entry>
1725 <entry><literal>%f
</literal></entry>
1726 <entry>Unescaped filename
</entry>
1727 <entry>This is either the unescaped instance name (if applicable) with
<filename>/
</filename> prepended (if applicable), or the unescaped prefix name prepended with
<filename>/
</filename>. This implements unescaping according to the rules for escaping absolute file system paths discussed above.
</entry>
1730 <entry><literal>%h
</literal></entry>
1731 <entry>User home directory
</entry>
1732 <entry>This is the home directory of the
<emphasis>user running the service manager instance
</emphasis>. In case of the system manager this resolves to
<literal>/root
</literal>.
1734 Note that this setting is
<emphasis>not
</emphasis> influenced by the
<varname>User=
</varname> setting configurable in the [Service] section of the service unit.
</entry>
1737 <entry><literal>%H
</literal></entry>
1738 <entry>Host name
</entry>
1739 <entry>The hostname of the running system at the point in time the unit configuration is loaded.
</entry>
1742 <entry><literal>%i
</literal></entry>
1743 <entry>Instance name
</entry>
1744 <entry>For instantiated units this is the string between the first
<literal>@
</literal> character and the type suffix. Empty for non-instantiated units.
</entry>
1747 <entry><literal>%I
</literal></entry>
1748 <entry>Unescaped instance name
</entry>
1749 <entry>Same as
<literal>%i
</literal>, but with escaping undone.
</entry>
1752 <entry><literal>%j
</literal></entry>
1753 <entry>Final component of the prefix
</entry>
1754 <entry>This is the string between the last
<literal>-
</literal> and the end of the prefix name. If there is no
<literal>-
</literal>, this is the same as
<literal>%p
</literal>.
</entry>
1757 <entry><literal>%J
</literal></entry>
1758 <entry>Unescaped final component of the prefix
</entry>
1759 <entry>Same as
<literal>%j
</literal>, but with escaping undone.
</entry>
1762 <entry><literal>%L
</literal></entry>
1763 <entry>Log directory root
</entry>
1764 <entry>This is either
<filename>/var/log
</filename> (for the system manager) or the path
<literal>$XDG_CONFIG_HOME
</literal> resolves to with
<filename index=
"false">/log
</filename> appended (for user managers).
</entry>
1767 <entry><literal>%m
</literal></entry>
1768 <entry>Machine ID
</entry>
1769 <entry>The machine ID of the running system, formatted as string. See
<citerefentry><refentrytitle>machine-id
</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information.
</entry>
1772 <entry><literal>%n
</literal></entry>
1773 <entry>Full unit name
</entry>
1777 <entry><literal>%N
</literal></entry>
1778 <entry>Full unit name
</entry>
1779 <entry>Same as
<literal>%n
</literal>, but with the type suffix removed.
</entry>
1782 <entry><literal>%p
</literal></entry>
1783 <entry>Prefix name
</entry>
1784 <entry>For instantiated units, this refers to the string before the first
<literal>@
</literal> character of the unit name. For non-instantiated units, same as
<literal>%N
</literal>.
</entry>
1787 <entry><literal>%P
</literal></entry>
1788 <entry>Unescaped prefix name
</entry>
1789 <entry>Same as
<literal>%p
</literal>, but with escaping undone.
</entry>
1792 <entry><literal>%s
</literal></entry>
1793 <entry>User shell
</entry>
1794 <entry>This is the shell of the user running the service manager instance. In case of the system manager this resolves to
<literal>/bin/sh
</literal>.
</entry>
1797 <entry><literal>%S
</literal></entry>
1798 <entry>State directory root
</entry>
1799 <entry>This is either
<filename>/var/lib
</filename> (for the system manager) or the path
<literal>$XDG_CONFIG_HOME
</literal> resolves to (for user managers).
</entry>
1802 <entry><literal>%t
</literal></entry>
1803 <entry>Runtime directory root
</entry>
1804 <entry>This is either
<filename>/run
</filename> (for the system manager) or the path
<literal>$XDG_RUNTIME_DIR
</literal> resolves to (for user managers).
</entry>
1807 <entry><literal>%T
</literal></entry>
1808 <entry>Directory for temporary files
</entry>
1809 <entry>This is either
<filename>/tmp
</filename> or the path
<literal>$TMPDIR
</literal>,
<literal>$TEMP
</literal> or
<literal>$TMP
</literal> are set to.
</entry>
1812 <entry><literal>%g
</literal></entry>
1813 <entry>User group
</entry>
1814 <entry>This is the name of the group running the service manager instance. In case of the system manager this resolves to
<literal>root
</literal>.
</entry>
1817 <entry><literal>%G
</literal></entry>
1818 <entry>User GID
</entry>
1819 <entry>This is the numeric GID of the user running the service manager instance. In case of the system manager this resolves to
<literal>0</literal>.
</entry>
1822 <entry><literal>%u
</literal></entry>
1823 <entry>User name
</entry>
1824 <entry>This is the name of the
<emphasis>user running the service manager instance
</emphasis>. In case of the system manager this resolves to
<literal>root
</literal>.
1826 Note that this setting is
<emphasis>not
</emphasis> influenced by the
<varname>User=
</varname> setting configurable in the [Service] section of the service unit.
</entry>
1829 <entry><literal>%U
</literal></entry>
1830 <entry>User UID
</entry>
1831 <entry>This is the numeric UID of the
<emphasis>user running the service manager instance
</emphasis>. In case of the system manager this resolves to
<literal>0</literal>.
1833 Note that this setting is
<emphasis>not
</emphasis> influenced by the
<varname>User=
</varname> setting configurable in the [Service] section of the service unit.
</entry>
1836 <entry><literal>%v
</literal></entry>
1837 <entry>Kernel release
</entry>
1838 <entry>Identical to
<command>uname -r
</command> output
</entry>
1841 <entry><literal>%V
</literal></entry>
1842 <entry>Directory for larger and persistent temporary files
</entry>
1843 <entry>This is either
<filename>/var/tmp
</filename> or the path
<literal>$TMPDIR
</literal>,
<literal>$TEMP
</literal> or
<literal>$TMP
</literal> are set to.
</entry>
1846 <entry><literal>%%
</literal></entry>
1847 <entry>Single percent sign
</entry>
1848 <entry>Use
<literal>%%
</literal> in place of
<literal>%
</literal> to specify a single percent sign.
</entry>
1856 <title>Examples
</title>
1859 <title>Allowing units to be enabled
</title>
1861 <para>The following snippet (highlighted) allows a unit (e.g.
1862 <filename>foo.service
</filename>) to be enabled via
1863 <command>systemctl enable
</command>:
</para>
1865 <programlisting>[Unit]
1869 ExecStart=/usr/sbin/foo-daemon
1871 <emphasis>[Install]
</emphasis>
1872 <emphasis>WantedBy=multi-user.target
</emphasis></programlisting>
1874 <para>After running
<command>systemctl enable
</command>, a
1876 <filename>/etc/systemd/system/multi-user.target.wants/foo.service
</filename>
1877 linking to the actual unit will be created. It tells systemd to
1878 pull in the unit when starting
1879 <filename>multi-user.target
</filename>. The inverse
1880 <command>systemctl disable
</command> will remove that symlink
1885 <title>Overriding vendor settings
</title>
1887 <para>There are two methods of overriding vendor settings in
1888 unit files: copying the unit file from
1889 <filename>/usr/lib/systemd/system
</filename> to
1890 <filename>/etc/systemd/system
</filename> and modifying the
1891 chosen settings. Alternatively, one can create a directory named
1892 <filename><replaceable>unit
</replaceable>.d/
</filename> within
1893 <filename>/etc/systemd/system
</filename> and place a drop-in
1894 file
<filename><replaceable>name
</replaceable>.conf
</filename>
1895 there that only changes the specific settings one is interested
1896 in. Note that multiple such drop-in files are read if
1897 present, processed in lexicographic order of their filename.
</para>
1899 <para>The advantage of the first method is that one easily
1900 overrides the complete unit, the vendor unit is not parsed at
1901 all anymore. It has the disadvantage that improvements to the
1902 unit file by the vendor are not automatically incorporated on
1905 <para>The advantage of the second method is that one only
1906 overrides the settings one specifically wants, where updates to
1907 the unit by the vendor automatically apply. This has the
1908 disadvantage that some future updates by the vendor might be
1909 incompatible with the local changes.
</para>
1911 <para>This also applies for user instances of systemd, but with
1912 different locations for the unit files. See the section on unit
1913 load paths for further details.
</para>
1915 <para>Suppose there is a vendor-supplied unit
1916 <filename>/usr/lib/systemd/system/httpd.service
</filename> with
1917 the following contents:
</para>
1919 <programlisting>[Unit]
1920 Description=Some HTTP server
1921 After=remote-fs.target sqldb.service
1922 Requires=sqldb.service
1923 AssertPathExists=/srv/webserver
1927 ExecStart=/usr/sbin/some-fancy-httpd-server
1931 WantedBy=multi-user.target
</programlisting>
1933 <para>Now one wants to change some settings as an administrator:
1934 firstly, in the local setup,
<filename>/srv/webserver
</filename>
1935 might not exist, because the HTTP server is configured to use
1936 <filename>/srv/www
</filename> instead. Secondly, the local
1937 configuration makes the HTTP server also depend on a memory
1938 cache service,
<filename>memcached.service
</filename>, that
1939 should be pulled in (
<varname>Requires=
</varname>) and also be
1940 ordered appropriately (
<varname>After=
</varname>). Thirdly, in
1941 order to harden the service a bit more, the administrator would
1942 like to set the
<varname>PrivateTmp=
</varname> setting (see
1943 <citerefentry><refentrytitle>systemd.exec
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1944 for details). And lastly, the administrator would like to reset
1945 the niceness of the service to its default value of
0.
</para>
1947 <para>The first possibility is to copy the unit file to
1948 <filename>/etc/systemd/system/httpd.service
</filename> and
1949 change the chosen settings:
</para>
1951 <programlisting>[Unit]
1952 Description=Some HTTP server
1953 After=remote-fs.target sqldb.service
<emphasis>memcached.service
</emphasis>
1954 Requires=sqldb.service
<emphasis>memcached.service
</emphasis>
1955 AssertPathExists=
<emphasis>/srv/www
</emphasis>
1959 ExecStart=/usr/sbin/some-fancy-httpd-server
1960 <emphasis>Nice=
0</emphasis>
1961 <emphasis>PrivateTmp=yes
</emphasis>
1964 WantedBy=multi-user.target
</programlisting>
1966 <para>Alternatively, the administrator could create a drop-in
1968 <filename>/etc/systemd/system/httpd.service.d/local.conf
</filename>
1969 with the following contents:
</para>
1971 <programlisting>[Unit]
1972 After=memcached.service
1973 Requires=memcached.service
1974 # Reset all assertions and then re-add the condition we want
1976 AssertPathExists=/srv/www
1980 PrivateTmp=yes
</programlisting>
1982 <para>Note that for drop-in files, if one wants to remove
1983 entries from a setting that is parsed as a list (and is not a
1984 dependency), such as
<varname>AssertPathExists=
</varname> (or
1985 e.g.
<varname>ExecStart=
</varname> in service units), one needs
1986 to first clear the list before re-adding all entries except the
1987 one that is to be removed. Dependencies (
<varname>After=
</varname>, etc.)
1988 cannot be reset to an empty list, so dependencies can only be
1989 added in drop-ins. If you want to remove dependencies, you have
1990 to override the entire unit.
</para>
1996 <title>See Also
</title>
1998 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1999 <citerefentry><refentrytitle>systemctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
2000 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2001 <citerefentry><refentrytitle>systemd.special
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
2002 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2003 <citerefentry><refentrytitle>systemd.socket
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2004 <citerefentry><refentrytitle>systemd.device
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2005 <citerefentry><refentrytitle>systemd.mount
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2006 <citerefentry><refentrytitle>systemd.automount
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2007 <citerefentry><refentrytitle>systemd.swap
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2008 <citerefentry><refentrytitle>systemd.target
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2009 <citerefentry><refentrytitle>systemd.path
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2010 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2011 <citerefentry><refentrytitle>systemd.scope
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2012 <citerefentry><refentrytitle>systemd.slice
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
2013 <citerefentry><refentrytitle>systemd.time
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
2014 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
2015 <citerefentry project='man-pages'
><refentrytitle>capabilities
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
2016 <citerefentry><refentrytitle>systemd.directives
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
2017 <citerefentry project='man-pages'
><refentrytitle>uname
</refentrytitle><manvolnum>1</manvolnum></citerefentry>