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udevadm-settle: add missing brace
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1 <?xml version='1.0'?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
4 <!ENTITY % entities SYSTEM "custom-entities.ent" >
5 %entities;
6 ]>
7
8 <!--
9   This file is part of systemd.
10
11   Copyright 2010 Lennart Poettering
12
13   systemd is free software; you can redistribute it and/or modify it
14   under the terms of the GNU Lesser General Public License as published by
15   the Free Software Foundation; either version 2.1 of the License, or
16   (at your option) any later version.
17
18   systemd is distributed in the hope that it will be useful, but
19   WITHOUT ANY WARRANTY; without even the implied warranty of
20   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
21   Lesser General Public License for more details.
22
23   You should have received a copy of the GNU Lesser General Public License
24   along with systemd; If not, see <http://www.gnu.org/licenses/>.
25 -->
26
27 <refentry id="systemd.unit">
28
29         <refentryinfo>
30                 <title>systemd.unit</title>
31                 <productname>systemd</productname>
32
33                 <authorgroup>
34                         <author>
35                                 <contrib>Developer</contrib>
36                                 <firstname>Lennart</firstname>
37                                 <surname>Poettering</surname>
38                                 <email>lennart@poettering.net</email>
39                         </author>
40                 </authorgroup>
41         </refentryinfo>
42
43         <refmeta>
44                 <refentrytitle>systemd.unit</refentrytitle>
45                 <manvolnum>5</manvolnum>
46         </refmeta>
47
48         <refnamediv>
49                 <refname>systemd.unit</refname>
50                 <refpurpose>Unit configuration</refpurpose>
51         </refnamediv>
52
53         <refsynopsisdiv>
54                 <para><filename><replaceable>service</replaceable>.service</filename>,
55                 <filename><replaceable>socket</replaceable>.socket</filename>,
56                 <filename><replaceable>device</replaceable>.device</filename>,
57                 <filename><replaceable>mount</replaceable>.mount</filename>,
58                 <filename><replaceable>automount</replaceable>.automount</filename>,
59                 <filename><replaceable>swap</replaceable>.swap</filename>,
60                 <filename><replaceable>target</replaceable>.target</filename>,
61                 <filename><replaceable>path</replaceable>.path</filename>,
62                 <filename><replaceable>timer</replaceable>.timer</filename>,
63                 <filename><replaceable>snapshot</replaceable>.snapshot</filename>,
64                 <filename><replaceable>slice</replaceable>.slice</filename>,
65                 <filename><replaceable>scope</replaceable>.scope</filename></para>
66
67                 <para><literallayout><filename>/etc/systemd/system/*</filename>
68 <filename>/run/systemd/system/*</filename>
69 <filename>/usr/lib/systemd/system/*</filename>
70 <filename>...</filename>
71                 </literallayout></para>
72
73                 <para><literallayout><filename>$HOME/.config/systemd/user/*</filename>
74 <filename>/etc/systemd/user/*</filename>
75 <filename>/run/systemd/user/*</filename>
76 <filename>/usr/lib/systemd/user/*</filename>
77 <filename>...</filename>
78                 </literallayout></para>
79         </refsynopsisdiv>
80
81         <refsect1>
82                 <title>Description</title>
83
84                 <para>A unit configuration file encodes information
85                 about a service, a socket, a device, a mount point, an
86                 automount point, a swap file or partition, a start-up
87                 target, a watched file system path, a timer controlled
88                 and supervised by
89                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
90                 a temporary system state snapshot, a resource
91                 management slice or a group of externally created
92                 processes. The syntax is inspired by <ulink
93                 url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
94                 Desktop Entry Specification</ulink>
95                 <filename>.desktop</filename> files, which are in turn
96                 inspired by Microsoft Windows
97                 <filename>.ini</filename> files.</para>
98
99                 <para>This man page lists the common configuration
100                 options of all the unit types. These options need to
101                 be configured in the [Unit] or [Install]
102                 sections of the unit files.</para>
103
104                 <para>In addition to the generic [Unit] and [Install]
105                 sections described here, each unit may have a
106                 type-specific section, e.g. [Service] for a service
107                 unit. See the respective man pages for more
108                 information:
109                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
110                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
111                 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
112                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
113                 <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
114                 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
115                 <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
116                 <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
117                 <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
118                 <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
119                 <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
120                 <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
121                 </para>
122
123                 <para>Unit files are loaded from a set of paths
124                 determined during compilation, described in the next section.
125                 </para>
126
127                 <para>Unit files may contain additional options on top
128                 of those listed here. If systemd encounters an unknown
129                 option, it will write a warning log message but
130                 continue loading the unit. If an option is prefixed
131                 with <option>X-</option>, it is ignored completely by
132                 systemd. Applications may use this to include
133                 additional information in the unit files.</para>
134
135                 <para>Boolean arguments used in unit files can be
136                 written in various formats. For positive settings the
137                 strings <option>1</option>, <option>yes</option>,
138                 <option>true</option> and <option>on</option> are
139                 equivalent. For negative settings, the strings
140                 <option>0</option>, <option>no</option>,
141                 <option>false</option> and <option>off</option> are
142                 equivalent.</para>
143
144                 <para>Time span values encoded in unit files can be
145                 written in various formats. A stand-alone number
146                 specifies a time in seconds. If suffixed with a time
147                 unit, the unit is honored. A concatenation of multiple
148                 values with units is supported, in which case the
149                 values are added up. Example: "50" refers to 50
150                 seconds; "2min 200ms" refers to 2 minutes plus 200
151                 milliseconds, i.e. 120200ms. The following time units
152                 are understood: s, min, h, d, w, ms, us. For details
153                 see
154                 <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
155
156                 <para>Empty lines and lines starting with # or ; are
157                 ignored. This may be used for commenting. Lines ending
158                 in a backslash are concatenated with the following
159                 line while reading and the backslash is replaced by a
160                 space character. This may be used to wrap long lines.</para>
161
162                 <para>Along with a unit file
163                 <filename>foo.service</filename>, the directory
164                 <filename>foo.service.wants/</filename> may exist. All
165                 unit files symlinked from such a directory are
166                 implicitly added as dependencies of type
167                 <varname>Wanted=</varname> to the unit. This is useful
168                 to hook units into the start-up of other units,
169                 without having to modify their unit files. For details
170                 about the semantics of <varname>Wanted=</varname>, see
171                 below. The preferred way to create symlinks in the
172                 <filename>.wants/</filename> directory of a unit file
173                 is with the <command>enable</command> command of the
174                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
175                 tool which reads information from the [Install]
176                 section of unit files (see below). A similar
177                 functionality exists for <varname>Requires=</varname>
178                 type dependencies as well, the directory suffix is
179                 <filename>.requires/</filename> in this case.</para>
180
181                 <para>Along with a unit file
182                 <filename>foo.service</filename>, a directory
183                 <filename>foo.service.d/</filename> may exist. All
184                 files with the suffix <literal>.conf</literal> from
185                 this directory will be parsed after the file itself is
186                 parsed. This is useful to alter or add configuration
187                 settings to a unit, without having to modify their
188                 unit files. Make sure that the file that is included
189                 has the appropriate section headers before any
190                 directive.</para>
191
192                 <para>If a line starts with <option>.include</option>
193                 followed by a filename, the specified file will be
194                 parsed at this point. Make sure that the file that is
195                 included has the appropriate section headers before
196                 any directives.</para>
197
198                 <para>Note that while systemd offers a flexible
199                 dependency system between units it is recommended to
200                 use this functionality only sparingly and instead rely
201                 on techniques such as bus-based or socket-based
202                 activation which make dependencies implicit, resulting
203                 in a both simpler and more flexible system.</para>
204
205                 <para>Some unit names reflect paths existing in the
206                 file system namespace. Example: a device unit
207                 <filename>dev-sda.device</filename> refers to a device
208                 with the device node <filename noindex='true'>/dev/sda</filename> in
209                 the file system namespace. If this applies, a special
210                 way to escape the path name is used, so that the
211                 result is usable as part of a filename. Basically,
212                 given a path, "/" is replaced by "-", and all
213                 unprintable characters and the "-" are replaced by
214                 C-style "\x20" escapes. The root directory "/" is
215                 encoded as single dash, while otherwise the initial
216                 and ending "/" is removed from all paths during
217                 transformation. This escaping is reversible.</para>
218
219                 <para>Optionally, units may be instantiated from a
220                 template file at runtime. This allows creation of
221                 multiple units from a single configuration file. If
222                 systemd looks for a unit configuration file, it will
223                 first search for the literal unit name in the
224                 filesystem. If that yields no success and the unit
225                 name contains an <literal>@</literal> character, systemd will look for a
226                 unit template that shares the same name but with the
227                 instance string (i.e. the part between the <literal>@</literal> character
228                 and the suffix) removed. Example: if a service
229                 <filename>getty@tty3.service</filename> is requested
230                 and no file by that name is found, systemd will look
231                 for <filename>getty@.service</filename> and
232                 instantiate a service from that configuration file if
233                 it is found.</para>
234
235                 <para>To refer to the instance string from
236                 within the configuration file you may use the special
237                 <literal>%i</literal> specifier in many of the
238                 configuration options. See below for details.</para>
239
240                 <para>If a unit file is empty (i.e. has the file size
241                 0) or is symlinked to <filename>/dev/null</filename>,
242                 its configuration will not be loaded and it appears
243                 with a load state of <literal>masked</literal>, and
244                 cannot be activated. Use this as an effective way to
245                 fully disable a unit, making it impossible to start it
246                 even manually.</para>
247
248                 <para>The unit file format is covered by the
249                 <ulink
250                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
251                 Stability Promise</ulink>.</para>
252
253         </refsect1>
254
255         <refsect1>
256                 <title>Unit Load Path</title>
257
258                 <para>Unit files are loaded from a set of paths
259                 determined during compilation, described in the two
260                 tables below. Unit files found in directories listed
261                 earlier override files with the same name in
262                 directories lower in the list.</para>
263
264                 <para>When systemd is running in user mode
265                 (<option>--user</option>) and the variable
266                 <varname>$SYSTEMD_UNIT_PATH</varname> is set, this
267                 contents of this variable overrides the unit load
268                 path.
269                 </para>
270
271                 <table>
272                   <title>
273                     Load path when running in system mode (<option>--system</option>).
274                   </title>
275
276                   <tgroup cols='2'>
277                     <colspec colname='path' />
278                     <colspec colname='expl' />
279                     <thead>
280                       <row>
281                         <entry>Path</entry>
282                         <entry>Description</entry>
283                       </row>
284                     </thead>
285                     <tbody>
286                       <row>
287                         <entry><filename>/etc/systemd/system</filename></entry>
288                         <entry>Local configuration</entry>
289                       </row>
290                       <row>
291                         <entry><filename>/run/systemd/system</filename></entry>
292                         <entry>Runtime units</entry>
293                       </row>
294                       <row>
295                         <entry><filename>/usr/lib/systemd/system</filename></entry>
296                         <entry>Units of installed packages</entry>
297                       </row>
298                     </tbody>
299                   </tgroup>
300                 </table>
301
302                 <table>
303                   <title>
304                     Load path when running in user mode (<option>--user</option>).
305                   </title>
306
307                   <tgroup cols='2'>
308                     <colspec colname='path' />
309                     <colspec colname='expl' />
310                     <thead>
311                       <row>
312                         <entry>Path</entry>
313                         <entry>Description</entry>
314                       </row>
315                     </thead>
316                     <tbody>
317                       <row>
318                         <entry><filename>$HOME/.config/systemd/user</filename></entry>
319                         <entry>User configuration</entry>
320                       </row>
321                       <row>
322                         <entry><filename>/etc/systemd/user</filename></entry>
323                         <entry>Local configuration</entry>
324                       </row>
325                       <row>
326                         <entry><filename>/run/systemd/user</filename></entry>
327                         <entry>Runtime units</entry>
328                       </row>
329                       <row>
330                         <entry><filename>/usr/lib/systemd/user</filename></entry>
331                         <entry>Units of installed packages</entry>
332                       </row>
333                     </tbody>
334                   </tgroup>
335                 </table>
336
337                 <para>Additional units might be loaded into systemd
338                 ("linked") from directories not on the unit load
339                 path. See the <command>link</command> command for
340                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>. Also,
341                 some units are dynamically created via generators
342                 <ulink
343                 url="http://www.freedesktop.org/wiki/Software/systemd/Generators/">Generators</ulink>.
344                 </para>
345         </refsect1>
346
347         <refsect1>
348                 <title>Options</title>
349
350                 <para>Unit file may include a [Unit] section, which
351                 carries generic information about the unit that is not
352                 dependent on the type of unit:</para>
353
354                 <variablelist class='unit-directives'>
355
356                         <varlistentry>
357                                 <term><varname>Description=</varname></term>
358                                 <listitem><para>A free-form string
359                                 describing the unit. This is intended
360                                 for use in UIs to show descriptive
361                                 information along with the unit
362                                 name. The description should contain a name
363                                 that means something to the end user.
364                                 <literal>Apache2 Web Server</literal> is a good
365                                 example. Bad examples are
366                                 <literal>high-performance light-weight HTTP
367                                 server</literal> (too generic) or
368                                 <literal>Apache2</literal> (too specific and
369                                 meaningless for people who do not know
370                                 Apache).</para></listitem>
371                         </varlistentry>
372
373                         <varlistentry>
374                                 <term><varname>Documentation=</varname></term>
375                                 <listitem><para>A space-separated list
376                                 of URIs referencing documentation for
377                                 this unit or its
378                                 configuration. Accepted are only URIs
379                                 of the types
380                                 <literal>http://</literal>,
381                                 <literal>https://</literal>,
382                                 <literal>file:</literal>,
383                                 <literal>info:</literal>,
384                                 <literal>man:</literal>. For more
385                                 information about the syntax of these
386                                 URIs, see
387                                 <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
388                                 URIs should be listed in order of
389                                 relevance, starting with the most
390                                 relevant. It is a good idea to first
391                                 reference documentation that explains
392                                 what the unit's purpose is, followed
393                                 by how it is configured, followed by
394                                 any other related documentation. This
395                                 option may be specified more than once
396                                 in which case the specified list of
397                                 URIs is merged. If the empty string is
398                                 assigned to this option, the list is
399                                 reset and all prior assignments will
400                                 have no effect.</para></listitem>
401                         </varlistentry>
402
403                         <varlistentry>
404                                 <term><varname>Requires=</varname></term>
405
406                                 <listitem><para>Configures requirement
407                                 dependencies on other units. If this
408                                 unit gets activated, the units listed
409                                 here will be activated as well. If one
410                                 of the other units gets deactivated or
411                                 its activation fails, this unit will
412                                 be deactivated. This option may be
413                                 specified more than once, in which
414                                 case requirement dependencies for all
415                                 listed names are created. Note that
416                                 requirement dependencies do not
417                                 influence the order in which services
418                                 are started or stopped. This has to be
419                                 configured independently with the
420                                 <varname>After=</varname> or
421                                 <varname>Before=</varname> options. If
422                                 a unit
423                                 <filename>foo.service</filename>
424                                 requires a unit
425                                 <filename>bar.service</filename> as
426                                 configured with
427                                 <varname>Requires=</varname> and no
428                                 ordering is configured with
429                                 <varname>After=</varname> or
430                                 <varname>Before=</varname>, then both
431                                 units will be started simultaneously
432                                 and without any delay between them if
433                                 <filename>foo.service</filename> is
434                                 activated. Often it is a better choice
435                                 to use <varname>Wants=</varname>
436                                 instead of
437                                 <varname>Requires=</varname> in order
438                                 to achieve a system that is more
439                                 robust when dealing with failing
440                                 services.</para>
441
442                                 <para>Note that dependencies of this
443                                 type may also be configured outside of
444                                 the unit configuration file by
445                                 adding a symlink to a
446                                 <filename>.requires/</filename> directory
447                                 accompanying the unit file. For
448                                 details see above.</para></listitem>
449                         </varlistentry>
450
451                         <varlistentry>
452                                 <term><varname>RequiresOverridable=</varname></term>
453
454                                 <listitem><para>Similar to
455                                 <varname>Requires=</varname>.
456                                 Dependencies listed in
457                                 <varname>RequiresOverridable=</varname>
458                                 which cannot be fulfilled or fail to
459                                 start are ignored if the startup was
460                                 explicitly requested by the user. If
461                                 the start-up was pulled in indirectly
462                                 by some dependency or automatic
463                                 start-up of units that is not
464                                 requested by the user, this dependency
465                                 must be fulfilled and otherwise the
466                                 transaction fails. Hence, this option
467                                 may be used to configure dependencies
468                                 that are normally honored unless the
469                                 user explicitly starts up the unit, in
470                                 which case whether they failed or not
471                                 is irrelevant.</para></listitem>
472
473                         </varlistentry>
474                         <varlistentry>
475                                 <term><varname>Requisite=</varname></term>
476                                 <term><varname>RequisiteOverridable=</varname></term>
477
478                                 <listitem><para>Similar to
479                                 <varname>Requires=</varname>
480                                 and <varname>RequiresOverridable=</varname>, respectively. However,
481                                 if a unit listed here is not started
482                                 already it will not be started and the
483                                 transaction fails
484                                 immediately.</para></listitem>
485                         </varlistentry>
486
487                         <varlistentry>
488                                 <term><varname>Wants=</varname></term>
489
490                                 <listitem><para>A weaker version of
491                                 <varname>Requires=</varname>. A unit
492                                 listed in this option will be started
493                                 if the configuring unit is. However,
494                                 if the listed unit fails to start up
495                                 or cannot be added to the transaction
496                                 this has no impact on the validity of
497                                 the transaction as a whole. This is
498                                 the recommended way to hook start-up
499                                 of one unit to the start-up of another
500                                 unit.</para>
501
502                                 <para>Note that dependencies of this
503                                 type may also be configured outside of
504                                 the unit configuration file by
505                                 adding a symlink to a
506                                 <filename>.wants/</filename> directory
507                                 accompanying the unit file. For
508                                 details see above.</para></listitem>
509                         </varlistentry>
510
511                         <varlistentry>
512                                 <term><varname>BindsTo=</varname></term>
513
514                                 <listitem><para>Configures requirement
515                                 dependencies, very similar in style to
516                                 <varname>Requires=</varname>, however
517                                 in addition to this behavior it also
518                                 declares that this unit is stopped
519                                 when any of the units listed suddenly
520                                 disappears. Units can suddenly,
521                                 unexpectedly disappear if a service
522                                 terminates on its own choice, a device
523                                 is unplugged or a mount point
524                                 unmounted without involvement of
525                                 systemd.</para></listitem>
526                         </varlistentry>
527
528                         <varlistentry>
529                                 <term><varname>PartOf=</varname></term>
530
531                                 <listitem><para>Configures dependencies
532                                 similar to <varname>Requires=</varname>,
533                                 but limited to stopping and restarting
534                                 of units. When systemd stops or restarts
535                                 the units listed here, the action is
536                                 propagated to this unit.
537                                 Note that this is a one way dependency -
538                                 changes to this unit do not affect the
539                                 listed units.
540                                 </para></listitem>
541                         </varlistentry>
542
543                         <varlistentry>
544                                 <term><varname>Conflicts=</varname></term>
545
546                                 <listitem><para>Configures negative
547                                 requirement dependencies. If a unit
548                                 has a
549                                 <varname>Conflicts=</varname> setting
550                                 on another unit, starting the former
551                                 will stop the latter and vice
552                                 versa. Note that this setting is
553                                 independent of and orthogonal to the
554                                 <varname>After=</varname> and
555                                 <varname>Before=</varname> ordering
556                                 dependencies.</para>
557
558                                 <para>If a unit A that conflicts with
559                                 a unit B is scheduled to be started at
560                                 the same time as B, the transaction
561                                 will either fail (in case both are
562                                 required part of the transaction) or
563                                 be modified to be fixed (in case one
564                                 or both jobs are not a required part
565                                 of the transaction). In the latter
566                                 case the job that is not the required
567                                 will be removed, or in case both are
568                                 not required the unit that conflicts
569                                 will be started and the unit that is
570                                 conflicted is
571                                 stopped.</para></listitem>
572                         </varlistentry>
573
574                         <varlistentry>
575                                 <term><varname>Before=</varname></term>
576                                 <term><varname>After=</varname></term>
577
578                                 <listitem><para>Configures ordering
579                                 dependencies between units. If a unit
580                                 <filename>foo.service</filename>
581                                 contains a setting
582                                 <option>Before=bar.service</option>
583                                 and both units are being started,
584                                 <filename>bar.service</filename>'s
585                                 start-up is delayed until
586                                 <filename>foo.service</filename> is
587                                 started up. Note that this setting is
588                                 independent of and orthogonal to the
589                                 requirement dependencies as configured
590                                 by <varname>Requires=</varname>. It is
591                                 a common pattern to include a unit
592                                 name in both the
593                                 <varname>After=</varname> and
594                                 <varname>Requires=</varname> option in
595                                 which case the unit listed will be
596                                 started before the unit that is
597                                 configured with these options. This
598                                 option may be specified more than
599                                 once, in which case ordering
600                                 dependencies for all listed names are
601                                 created. <varname>After=</varname> is
602                                 the inverse of
603                                 <varname>Before=</varname>, i.e. while
604                                 <varname>After=</varname> ensures that
605                                 the configured unit is started after
606                                 the listed unit finished starting up,
607                                 <varname>Before=</varname> ensures the
608                                 opposite, i.e.  that the configured
609                                 unit is fully started up before the
610                                 listed unit is started. Note that when
611                                 two units with an ordering dependency
612                                 between them are shut down, the
613                                 inverse of the start-up order is
614                                 applied. i.e. if a unit is configured
615                                 with <varname>After=</varname> on
616                                 another unit, the former is stopped
617                                 before the latter if both are shut
618                                 down. If one unit with an ordering
619                                 dependency on another unit is shut
620                                 down while the latter is started up,
621                                 the shut down is ordered before the
622                                 start-up regardless whether the
623                                 ordering dependency is actually of
624                                 type <varname>After=</varname> or
625                                 <varname>Before=</varname>. If two
626                                 units have no ordering dependencies
627                                 between them, they are shut down
628                                 or started up simultaneously, and
629                                 no ordering takes
630                                 place. </para></listitem>
631                         </varlistentry>
632
633                         <varlistentry>
634                                 <term><varname>OnFailure=</varname></term>
635
636                                 <listitem><para>Lists one or more
637                                 units that are activated when this
638                                 unit enters the
639                                 <literal>failed</literal>
640                                 state.</para></listitem>
641                         </varlistentry>
642
643                         <varlistentry>
644                                 <term><varname>PropagatesReloadTo=</varname></term>
645                                 <term><varname>ReloadPropagatedFrom=</varname></term>
646
647                                 <listitem><para>Lists one or more
648                                 units where reload requests on the
649                                 unit will be propagated to/on the
650                                 other unit will be propagated
651                                 from. Issuing a reload request on a
652                                 unit will automatically also enqueue a
653                                 reload request on all units that the
654                                 reload request shall be propagated to
655                                 via these two
656                                 settings.</para></listitem>
657                         </varlistentry>
658
659                         <varlistentry>
660                                 <term><varname>RequiresMountsFor=</varname></term>
661
662                                 <listitem><para>Takes a space-separated
663                                 list of absolute paths. Automatically
664                                 adds dependencies of type
665                                 <varname>Requires=</varname> and
666                                 <varname>After=</varname> for all
667                                 mount units required to access the
668                                 specified path.</para></listitem>
669                         </varlistentry>
670
671                         <varlistentry>
672                                 <term><varname>OnFailureIsolate=</varname></term>
673
674                                 <listitem><para>Takes a boolean
675                                 argument. If <option>true</option>, the
676                                 unit listed in
677                                 <varname>OnFailure=</varname> will be
678                                 enqueued in isolation mode, i.e. all
679                                 units that are not its dependency will
680                                 be stopped. If this is set, only a
681                                 single unit may be listed in
682                                 <varname>OnFailure=</varname>. Defaults
683                                 to
684                                 <option>false</option>.</para></listitem>
685                         </varlistentry>
686
687                         <varlistentry>
688                                 <term><varname>IgnoreOnIsolate=</varname></term>
689
690                                 <listitem><para>Takes a boolean
691                                 argument. If <option>true</option>,
692                                 this unit will not be stopped when
693                                 isolating another unit. Defaults to
694                                 <option>false</option>.</para></listitem>
695                         </varlistentry>
696
697                         <varlistentry>
698                                 <term><varname>IgnoreOnSnapshot=</varname></term>
699
700                                 <listitem><para>Takes a boolean
701                                 argument. If <option>true</option>,
702                                 this unit will not be included in
703                                 snapshots. Defaults to
704                                 <option>true</option> for device and
705                                 snapshot units, <option>false</option>
706                                 for the others.</para></listitem>
707                         </varlistentry>
708
709                         <varlistentry>
710                                 <term><varname>StopWhenUnneeded=</varname></term>
711
712                                 <listitem><para>Takes a boolean
713                                 argument. If <option>true</option>,
714                                 this unit will be stopped when it is
715                                 no longer used. Note that in order to
716                                 minimize the work to be executed,
717                                 systemd will not stop units by default
718                                 unless they are conflicting with other
719                                 units, or the user explicitly
720                                 requested their shut down. If this
721                                 option is set, a unit will be
722                                 automatically cleaned up if no other
723                                 active unit requires it. Defaults to
724                                 <option>false</option>.</para></listitem>
725                         </varlistentry>
726
727                         <varlistentry>
728                                 <term><varname>RefuseManualStart=</varname></term>
729                                 <term><varname>RefuseManualStop=</varname></term>
730
731                                 <listitem><para>Takes a boolean
732                                 argument. If <option>true</option>,
733                                 this unit can only be activated
734                                 or deactivated indirectly. In
735                                 this case, explicit start-up
736                                 or termination requested by the
737                                 user is denied, however if it is
738                                 started or stopped as a
739                                 dependency of another unit, start-up
740                                 or termination will succeed. This
741                                 is mostly a safety feature to ensure
742                                 that the user does not accidentally
743                                 activate units that are not intended
744                                 to be activated explicitly, and not
745                                 accidentally deactivate units that are
746                                 not intended to be deactivated.
747                                 These options default to
748                                 <option>false</option>.</para></listitem>
749                         </varlistentry>
750
751                         <varlistentry>
752                                 <term><varname>AllowIsolate=</varname></term>
753
754                                 <listitem><para>Takes a boolean
755                                 argument. If <option>true</option>,
756                                 this unit may be used with the
757                                 <command>systemctl isolate</command>
758                                 command. Otherwise, this will be
759                                 refused. It probably is a good idea to
760                                 leave this disabled except for target
761                                 units that shall be used similar to
762                                 runlevels in SysV init systems, just
763                                 as a precaution to avoid unusable
764                                 system states. This option defaults to
765                                 <option>false</option>.</para></listitem>
766                         </varlistentry>
767
768                         <varlistentry>
769                                 <term><varname>DefaultDependencies=</varname></term>
770
771                                 <listitem><para>Takes a boolean
772                                 argument. If <option>true</option>,
773                                 (the default), a few default
774                                 dependencies will implicitly be
775                                 created for the unit. The actual
776                                 dependencies created depend on the
777                                 unit type. For example, for service
778                                 units, these dependencies ensure that
779                                 the service is started only after
780                                 basic system initialization is
781                                 completed and is properly terminated on
782                                 system shutdown. See the respective
783                                 man pages for details. Generally, only
784                                 services involved with early boot or
785                                 late shutdown should set this option
786                                 to <option>false</option>. It is
787                                 highly recommended to leave this
788                                 option enabled for the majority of
789                                 common units. If set to
790                                 <option>false</option>, this option
791                                 does not disable all implicit
792                                 dependencies, just non-essential
793                                 ones.</para></listitem>
794                         </varlistentry>
795
796                         <varlistentry>
797                                 <term><varname>JobTimeoutSec=</varname></term>
798
799                                 <listitem><para>When clients are
800                                 waiting for a job of this unit to
801                                 complete, time out after the specified
802                                 time. If this time limit is reached,
803                                 the job will be cancelled, the unit
804                                 however will not change state or even
805                                 enter the <literal>failed</literal>
806                                 mode. This value defaults to 0 (job
807                                 timeouts disabled), except for device
808                                 units. NB: this timeout is independent
809                                 from any unit-specific timeout (for
810                                 example, the timeout set with
811                                 <varname>Timeout=</varname> in service
812                                 units) as the job timeout has no
813                                 effect on the unit itself, only on the
814                                 job that might be pending for it. Or
815                                 in other words: unit-specific timeouts
816                                 are useful to abort unit state
817                                 changes, and revert them. The job
818                                 timeout set with this option however
819                                 is useful to abort only the job
820                                 waiting for the unit state to
821                                 change.</para></listitem>
822                         </varlistentry>
823
824                         <varlistentry>
825                                 <term><varname>ConditionPathExists=</varname></term>
826                                 <term><varname>ConditionPathExistsGlob=</varname></term>
827                                 <term><varname>ConditionPathIsDirectory=</varname></term>
828                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
829                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
830                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
831                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
832                                 <term><varname>ConditionFileNotEmpty=</varname></term>
833                                 <term><varname>ConditionFileIsExecutable=</varname></term>
834                                 <term><varname>ConditionKernelCommandLine=</varname></term>
835                                 <term><varname>ConditionVirtualization=</varname></term>
836                                 <term><varname>ConditionSecurity=</varname></term>
837                                 <term><varname>ConditionCapability=</varname></term>
838                                 <term><varname>ConditionHost=</varname></term>
839                                 <term><varname>ConditionACPower=</varname></term>
840                                 <term><varname>ConditionNull=</varname></term>
841
842                                 <listitem><para>Before starting a unit
843                                 verify that the specified condition is
844                                 true. If it is not true, the starting
845                                 of the unit will be skipped, however
846                                 all ordering dependencies of it are
847                                 still respected. A failing condition
848                                 will not result in the unit being
849                                 moved into a failure state. The
850                                 condition is checked at the time the
851                                 queued start job is to be
852                                 executed.</para>
853
854                                 <para>With
855                                 <varname>ConditionPathExists=</varname>
856                                 a file existence condition is
857                                 checked before a unit is started. If
858                                 the specified absolute path name does
859                                 not exist, the condition will
860                                 fail. If the absolute path name passed
861                                 to
862                                 <varname>ConditionPathExists=</varname>
863                                 is prefixed with an exclamation mark
864                                 (<literal>!</literal>), the test is negated, and the unit
865                                 is only started if the path does not
866                                 exist.</para>
867
868                                 <para><varname>ConditionPathExistsGlob=</varname>
869                                 is similar to
870                                 <varname>ConditionPathExists=</varname>,
871                                 but checks for the existence of at
872                                 least one file or directory matching
873                                 the specified globbing pattern.</para>
874
875                                 <para><varname>ConditionPathIsDirectory=</varname>
876                                 is similar to
877                                 <varname>ConditionPathExists=</varname>
878                                 but verifies whether a certain path
879                                 exists and is a
880                                 directory.</para>
881
882                                 <para><varname>ConditionPathIsSymbolicLink=</varname>
883                                 is similar to
884                                 <varname>ConditionPathExists=</varname>
885                                 but verifies whether a certain path
886                                 exists and is a symbolic
887                                 link.</para>
888
889                                 <para><varname>ConditionPathIsMountPoint=</varname>
890                                 is similar to
891                                 <varname>ConditionPathExists=</varname>
892                                 but verifies whether a certain path
893                                 exists and is a mount
894                                 point.</para>
895
896                                 <para><varname>ConditionPathIsReadWrite=</varname>
897                                 is similar to
898                                 <varname>ConditionPathExists=</varname>
899                                 but verifies whether the underlying
900                                 file system is readable and writable
901                                 (i.e. not mounted
902                                 read-only).</para>
903
904                                 <para><varname>ConditionDirectoryNotEmpty=</varname>
905                                 is similar to
906                                 <varname>ConditionPathExists=</varname>
907                                 but verifies whether a certain path
908                                 exists and is a non-empty
909                                 directory.</para>
910
911                                 <para><varname>ConditionFileNotEmpty=</varname>
912                                 is similar to
913                                 <varname>ConditionPathExists=</varname>
914                                 but verifies whether a certain path
915                                 exists and refers to a regular file
916                                 with a non-zero size.</para>
917
918                                 <para><varname>ConditionFileIsExecutable=</varname>
919                                 is similar to
920                                 <varname>ConditionPathExists=</varname>
921                                 but verifies whether a certain path
922                                 exists, is a regular file and marked
923                                 executable.</para>
924
925                                 <para>Similar,
926                                 <varname>ConditionKernelCommandLine=</varname>
927                                 may be used to check whether a
928                                 specific kernel command line option is
929                                 set (or if prefixed with the
930                                 exclamation mark unset). The argument
931                                 must either be a single word, or an
932                                 assignment (i.e. two words, separated
933                                 <literal>=</literal>). In the former
934                                 case the kernel command line is
935                                 searched for the word appearing as is,
936                                 or as left hand side of an
937                                 assignment. In the latter case the
938                                 exact assignment is looked for with
939                                 right and left hand side
940                                 matching.</para>
941
942                                 <para><varname>ConditionVirtualization=</varname>
943                                 may be used to check whether the
944                                 system is executed in a virtualized
945                                 environment and optionally test
946                                 whether it is a specific
947                                 implementation. Takes either boolean
948                                 value to check if being executed in
949                                 any virtualized environment, or one of
950                                 <varname>vm</varname> and
951                                 <varname>container</varname> to test
952                                 against a generic type of
953                                 virtualization solution, or one of
954                                 <varname>qemu</varname>,
955                                 <varname>kvm</varname>,
956                                 <varname>vmware</varname>,
957                                 <varname>microsoft</varname>,
958                                 <varname>oracle</varname>,
959                                 <varname>xen</varname>,
960                                 <varname>bochs</varname>,
961                                 <varname>chroot</varname>,
962                                 <varname>uml</varname>,
963                                 <varname>openvz</varname>,
964                                 <varname>lxc</varname>,
965                                 <varname>lxc-libvirt</varname>,
966                                 <varname>systemd-nspawn</varname> to
967                                 test against a specific
968                                 implementation. If multiple
969                                 virtualization technologies are nested,
970                                 only the innermost is considered. The
971                                 test may be negated by prepending an
972                                 exclamation mark.</para>
973
974                                 <para><varname>ConditionSecurity=</varname>
975                                 may be used to check whether the given
976                                 security module is enabled on the
977                                 system. Currently the recognized values
978                                 values are <varname>selinux</varname>,
979                                 <varname>apparmor</varname>,
980                                 <varname>ima</varname> and
981                                 <varname>smack</varname>.
982                                 The test may be negated by prepending
983                                 an exclamation
984                                 mark.</para>
985
986                                 <para><varname>ConditionCapability=</varname>
987                                 may be used to check whether the given
988                                 capability exists in the capability
989                                 bounding set of the service manager
990                                 (i.e. this does not check whether
991                                 capability is actually available in
992                                 the permitted or effective sets, see
993                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
994                                 for details). Pass a capability name
995                                 such as <literal>CAP_MKNOD</literal>,
996                                 possibly prefixed with an exclamation
997                                 mark to negate the check.</para>
998
999                                 <para><varname>ConditionHost=</varname>
1000                                 may be used to match against the
1001                                 hostname or machine ID of the
1002                                 host. This either takes a hostname
1003                                 string (optionally with shell style
1004                                 globs) which is tested against the
1005                                 locally set hostname as returned by
1006                                 <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
1007                                 or a machine ID formatted as string
1008                                 (see
1009                                 <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
1010                                 The test may be negated by prepending
1011                                 an exclamation mark.</para>
1012
1013                                 <para><varname>ConditionACPower=</varname>
1014                                 may be used to check whether the
1015                                 system has AC power, or is exclusively
1016                                 battery powered at the time of
1017                                 activation of the unit. This takes a
1018                                 boolean argument. If set to
1019                                 <varname>true</varname>, the condition
1020                                 will hold only if at least one AC
1021                                 connector of the system is connected
1022                                 to a power source, or if no AC
1023                                 connectors are known. Conversely, if
1024                                 set to <varname>false</varname>, the
1025                                 condition will hold only if there is
1026                                 at least one AC connector known and
1027                                 all AC connectors are disconnected
1028                                 from a power source.</para>
1029
1030                                 <para>Finally,
1031                                 <varname>ConditionNull=</varname> may
1032                                 be used to add a constant condition
1033                                 check value to the unit. It takes a
1034                                 boolean argument. If set to
1035                                 <varname>false</varname>, the condition
1036                                 will always fail, otherwise
1037                                 succeed.</para>
1038
1039                                 <para>If multiple conditions are
1040                                 specified, the unit will be executed if
1041                                 all of them apply (i.e. a logical AND
1042                                 is applied). Condition checks can be
1043                                 prefixed with a pipe symbol (|) in
1044                                 which case a condition becomes a
1045                                 triggering condition. If at least one
1046                                 triggering condition is defined for a
1047                                 unit, then the unit will be executed if
1048                                 at least one of the triggering
1049                                 conditions apply and all of the
1050                                 non-triggering conditions. If you
1051                                 prefix an argument with the pipe
1052                                 symbol and an exclamation mark, the
1053                                 pipe symbol must be passed first, the
1054                                 exclamation second. Except for
1055                                 <varname>ConditionPathIsSymbolicLink=</varname>,
1056                                 all path checks follow symlinks. If
1057                                 any of these options is assigned the
1058                                 empty string, the list of conditions is
1059                                 reset completely, all previous
1060                                 condition settings (of any kind) will
1061                                 have no effect.</para></listitem>
1062                         </varlistentry>
1063
1064                         <varlistentry>
1065                                 <term><varname>SourcePath=</varname></term>
1066                                 <listitem><para>A path to a
1067                                 configuration file this unit has been
1068                                 generated from. This is primarily
1069                                 useful for implementation of generator
1070                                 tools that convert configuration from
1071                                 an external configuration file format
1072                                 into native unit files. Thus
1073                                 functionality should not be used in
1074                                 normal units.</para></listitem>
1075                         </varlistentry>
1076                 </variablelist>
1077
1078                 <para>Unit file may include a [Install] section, which
1079                 carries installation information for the unit. This
1080                 section is not interpreted by
1081                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1082                 during runtime. It is used exclusively by the
1083                 <command>enable</command> and
1084                 <command>disable</command> commands of the
1085                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1086                 tool during installation of a unit:</para>
1087
1088                 <variablelist class='unit-directives'>
1089                         <varlistentry>
1090                                 <term><varname>Alias=</varname></term>
1091
1092                                 <listitem><para>Additional names this
1093                                 unit shall be installed under. The
1094                                 names listed here must have the same
1095                                 suffix (i.e. type) as the unit file
1096                                 name. This option may be specified
1097                                 more than once, in which case all
1098                                 listed names are used. At installation
1099                                 time,
1100                                 <command>systemctl enable</command>
1101                                 will create symlinks from these names
1102                                 to the unit filename.</para></listitem>
1103                         </varlistentry>
1104
1105                         <varlistentry>
1106                                 <term><varname>WantedBy=</varname></term>
1107                                 <term><varname>RequiredBy=</varname></term>
1108
1109                                 <listitem><para>A symbolic link is
1110                                 created in the
1111                                 <filename>.wants/</filename> or
1112                                 <filename>.requires/</filename> directory
1113                                 of the listed unit when this unit is
1114                                 activated by <command>systemctl
1115                                 enable</command>.  This has the effect
1116                                 that a dependency of type
1117                                 <varname>Wants=</varname> or
1118                                 <varname>Requires=</varname> is added
1119                                 from the listed unit to the current
1120                                 unit. The primary result is that the
1121                                 current unit will be started when the
1122                                 listed unit is started. See the
1123                                 description of
1124                                 <varname>Wants=</varname> and
1125                                 <varname>Requires=</varname> in the
1126                                 [Unit] section for details.</para>
1127
1128                                 <para><command>WantedBy=foo.service</command>
1129                                 in a service
1130                                 <filename>bar.service</filename> is
1131                                 mostly equivalent to
1132                                 <command>Alias=foo.service.wants/bar.service</command>
1133                                 in the same file. In case of template
1134                                 units, <command>systemctl enable</command>
1135                                 must be called with an instance name, and
1136                                 this instance will be added to the
1137                                 <filename>.wants/</filename> or
1138                                 <filename>.requires/</filename> list
1139                                 of the listed unit.
1140                                 E.g. <command>WantedBy=getty.target</command>
1141                                 in a service
1142                                 <filename>getty@.service</filename>
1143                                 will result in <command>systemctl
1144                                 enable getty@tty2.service</command>
1145                                 creating a
1146                                 <filename>getty.target.wants/getty@tty2.service</filename>
1147                                 link to <filename>getty@.service</filename>.
1148                                 </para></listitem>
1149                         </varlistentry>
1150
1151                         <varlistentry>
1152                                 <term><varname>Also=</varname></term>
1153
1154                                 <listitem><para>Additional units to
1155                                 install/deinstall when this unit is
1156                                 installed/deinstalled. If the user
1157                                 requests installation/deinstallation
1158                                 of a unit with this option configured,
1159                                 <command>systemctl enable</command>
1160                                 and <command>systemctl
1161                                 disable</command> will automatically
1162                                 install/uninstall units listed in this option as
1163                                 well.</para></listitem>
1164                         </varlistentry>
1165                 </variablelist>
1166
1167                 <para>The following specifiers are interpreted in the
1168                 Install section: %n, %N, %p, %i, %U, %u, %m, %H, %b, %v.
1169                 For their meaning see the next section.
1170                 </para>
1171         </refsect1>
1172
1173         <refsect1>
1174                 <title>Specifiers</title>
1175
1176                 <para>Many settings resolve specifiers which may be
1177                 used to write generic unit files referring to runtime
1178                 or unit parameters that are replaced when the unit
1179                 files are loaded. The following specifiers are
1180                 understood:</para>
1181
1182                 <table>
1183                   <title>Specifiers available in unit files</title>
1184                   <tgroup cols='3' align='left' colsep='1' rowsep='1'>
1185                     <colspec colname="spec" />
1186                     <colspec colname="mean" />
1187                     <colspec colname="detail" />
1188                     <thead>
1189                       <row>
1190                         <entry>Specifier</entry>
1191                         <entry>Meaning</entry>
1192                         <entry>Details</entry>
1193                       </row>
1194                     </thead>
1195                     <tbody>
1196                       <row>
1197                         <entry><literal>%n</literal></entry>
1198                         <entry>Full unit name</entry>
1199                         <entry></entry>
1200                       </row>
1201                       <row>
1202                         <entry><literal>%N</literal></entry>
1203                         <entry>Unescaped full unit name</entry>
1204                         <entry></entry>
1205                       </row>
1206                       <row>
1207                         <entry><literal>%p</literal></entry>
1208                         <entry>Prefix name</entry>
1209                         <entry>For instantiated units this refers to the string before the @. For non-instantiated units this refers to to the name of the unit with the type suffix removed.</entry>
1210                       </row>
1211                       <row>
1212                         <entry><literal>%P</literal></entry>
1213                         <entry>Unescaped prefix name</entry>
1214                         <entry></entry>
1215                       </row>
1216                       <row>
1217                         <entry><literal>%i</literal></entry>
1218                         <entry>Instance name</entry>
1219                         <entry>For instantiated units: this is the string between the <literal>@</literal> character and the suffix.</entry>
1220                       </row>
1221                       <row>
1222                         <entry><literal>%I</literal></entry>
1223                         <entry>Unescaped instance name</entry>
1224                         <entry></entry>
1225                       </row>
1226                       <row>
1227                         <entry><literal>%f</literal></entry>
1228                         <entry>Unescaped filename</entry>
1229                         <entry>This is either the unescaped instance name (if applicable) with <filename>/</filename> prepended (if applicable), or the prefix name similarly prepended with <filename>/</filename>.</entry>
1230                       </row>
1231                       <row>
1232                         <entry><literal>%c</literal></entry>
1233                         <entry>Control group path of the unit</entry>
1234                         <entry></entry>
1235                       </row>
1236                       <row>
1237                         <entry><literal>%r</literal></entry>
1238                         <entry>Root control group path where units are placed.</entry>
1239                         <entry>For system instances, this usually resolves to <filename>/system</filename>, except in containers, where the path might be prefixed with the container's root control group.</entry>
1240                       </row>
1241                       <row>
1242                         <entry><literal>%R</literal></entry>
1243                         <entry>Parent directory of the control group path where units are placed.</entry>
1244                         <entry>For system instances, this usually
1245                         resolves to <filename>/</filename>, except in
1246                         containers, where this resolves to the
1247                         container's root directory.</entry>
1248                       </row>
1249                       <row>
1250                         <entry><literal>%t</literal></entry>
1251                         <entry>Runtime socket dir</entry>
1252                         <entry>This is either <filename>/run</filename> (for the system manager) or <literal>$XDG_RUNTIME_DIR</literal> (for user managers).</entry>
1253                       </row>
1254                       <row>
1255                         <entry><literal>%u</literal></entry>
1256                         <entry>User name</entry>
1257                         <entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1258                       </row>
1259                       <row>
1260                         <entry><literal>%U</literal></entry>
1261                         <entry>User UID</entry>
1262                         <entry>This is the UID of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1263                       </row>
1264                       <row>
1265                         <entry><literal>%h</literal></entry>
1266                         <entry>User home directory</entry>
1267                         <entry>This is the home directory of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1268                       </row>
1269                       <row>
1270                         <entry><literal>%s</literal></entry>
1271                         <entry>User shell</entry>
1272                         <entry>This is the shell of the configured user of the unit, or (if none is set) the user running the systemd instance.  If the user is <literal>root</literal> (UID equal to 0), the shell configured in account database is ignored and <filename>/bin/sh</filename> is always used.</entry>
1273                       </row>
1274                       <row>
1275                         <entry><literal>%m</literal></entry>
1276                         <entry>Machine ID</entry>
1277                         <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>
1278                       </row>
1279                       <row>
1280                         <entry><literal>%b</literal></entry>
1281                         <entry>Boot ID</entry>
1282                         <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
1283                       </row>
1284                       <row>
1285                         <entry><literal>%H</literal></entry>
1286                         <entry>Host name</entry>
1287                         <entry>The hostname of the running system.</entry>
1288                       </row>
1289                       <row>
1290                         <entry><literal>%v</literal></entry>
1291                         <entry>Kernel release</entry>
1292                         <entry>Identical to <command>uname -r</command> output.</entry>
1293                       </row>
1294                       <row>
1295                         <entry><literal>%%</literal></entry>
1296                         <entry>Escaped %</entry>
1297                         <entry>Single percent sign.</entry>
1298                       </row>
1299                     </tbody>
1300                   </tgroup>
1301                 </table>
1302         </refsect1>
1303
1304         <refsect1>
1305                 <title>See Also</title>
1306                 <para>
1307                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1308                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1309                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1310                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1311                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1312                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1313                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1314                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1315                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1316                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1317                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1318                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1319                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1320                         <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1321                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1322                         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1323                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1324                         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1325                         <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1326                 </para>
1327         </refsect1>
1328
1329 </refentry>