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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
5 <!--
6   This file is part of systemd.
7
8   Copyright 2010 Lennart Poettering
9
10   systemd is free software; you can redistribute it and/or modify it
11   under the terms of the GNU General Public License as published by
12   the Free Software Foundation; either version 2 of the License, or
13   (at your option) any later version.
14
15   systemd is distributed in the hope that it will be useful, but
16   WITHOUT ANY WARRANTY; without even the implied warranty of
17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18   General Public License for more details.
19
20   You should have received a copy of the GNU General Public License
21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
22 -->
23
24 <refentry id="systemd.unit">
25
26         <refentryinfo>
27                 <title>systemd.unit</title>
28                 <productname>systemd</productname>
29
30                 <authorgroup>
31                         <author>
32                                 <contrib>Developer</contrib>
33                                 <firstname>Lennart</firstname>
34                                 <surname>Poettering</surname>
35                                 <email>lennart@poettering.net</email>
36                         </author>
37                 </authorgroup>
38         </refentryinfo>
39
40         <refmeta>
41                 <refentrytitle>systemd.unit</refentrytitle>
42                 <manvolnum>5</manvolnum>
43         </refmeta>
44
45         <refnamediv>
46                 <refname>systemd.unit</refname>
47                 <refpurpose>systemd unit configuration files</refpurpose>
48         </refnamediv>
49
50         <refsynopsisdiv>
51                 <para><filename>systemd.service</filename>,
52                 <filename>systemd.socket</filename>,
53                 <filename>systemd.device</filename>,
54                 <filename>systemd.mount</filename>,
55                 <filename>systemd.automount</filename>,
56                 <filename>systemd.swap</filename>,
57                 <filename>systemd.target</filename>,
58                 <filename>systemd.path</filename>,
59                 <filename>systemd.timer</filename>,
60                 <filename>systemd.snapshot</filename></para>
61         </refsynopsisdiv>
62
63         <refsect1>
64                 <title>Description</title>
65
66                 <para>A unit configuration file encodes information
67                 about a service, a socket, a device, a mount point, an
68                 automount point, a swap file or partition, a start-up
69                 target, a file system path or a timer controlled and
70                 supervised by
71                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>. The
72                 syntax is inspired by <ulink
73                 url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
74                 Desktop Entry Specification</ulink> <filename>.desktop</filename> files, which are in turn
75                 inspired by Microsoft Windows
76                 <filename>.ini</filename> files.</para>
77
78                 <para>This man pages lists the common configuration
79                 options of all the unit types. These options need to
80                 be configured in the [Unit] resp. [Install]
81                 section of the unit files.</para>
82
83                 <para>In addition to the generic [Unit] and [Install]
84                 sections described here, each unit should have a
85                 type-specific section, e.g. [Service] for a service
86                 unit. See the respective man pages for more
87                 information.</para>
88
89                 <para>Unit files may contain additional options on top
90                 of those listed here. If systemd encounters an unknown
91                 option it will write a warning log message but
92                 continue loading the unit. If an option is prefixed
93                 with <option>X-</option> it is ignored completely by
94                 systemd. Applications may use this to include
95                 additional information in the unit files.</para>
96
97                 <para>Boolean arguments used in unit files can be
98                 written in various formats. For positive settings the
99                 strings <option>1</option>, <option>yes</option>,
100                 <option>true</option> and <option>on</option> are
101                 equivalent. For negative settings the strings
102                 <option>0</option>, <option>no</option>,
103                 <option>false</option> and <option>off</option> are
104                 equivalent.</para>
105
106                 <para>Time span values encoded in unit files can be
107                 written in various formats. A stand-alone number
108                 specifies a time in seconds. If suffixed with a time
109                 unit, the unit is honored. A concatenation of
110                 multiple values with units is supported, in which case
111                 the values are added up. Example: "50" refers to 50
112                 seconds; "2min 200ms" refers to 2 minutes plus 200
113                 milliseconds, i.e. 120200ms. The following time units
114                 are understood: s, min, h, d, w, ms, us.</para>
115
116                 <para>Empty lines and lines starting with # or ; are
117                 ignored. This may be used for commenting. Lines ending
118                 in a backslash are concatenated with the following
119                 line while reading and the backslash is replaced by a
120                 space character. This may be used to wrap long lines.</para>
121
122                 <para>If a line starts with <option>.include</option>
123                 followed by a file name, the specified file will be
124                 read as if its contents were listed in place of the
125                 <option>.include</option> directive.</para>
126
127                 <para>Along with a unit file
128                 <filename>foo.service</filename> a directory
129                 <filename>foo.service.wants/</filename> may exist. All
130                 units symlinked from such a directory are implicitly
131                 added as dependencies of type
132                 <varname>Wanted=</varname> to the unit. This is useful
133                 to hook units into the start-up of other units,
134                 without having to modify their unit configuration
135                 files. For details about the semantics of
136                 <varname>Wanted=</varname> see below. The preferred
137                 way to create symlinks in the
138                 <filename>.wants/</filename> directory of a service is
139                 with the <command>enable</command> command of the
140                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
141                 tool which reads information from the [Install]
142                 section of unit files. (See below.)</para>
143
144                 <para>Note that while systemd offers a flexible
145                 dependency system between units it is recommended to
146                 use this functionality only sparsely and instead rely
147                 on techniques such as bus-based or socket-based
148                 activation which makes dependencies implicit, which
149                 both results in a simpler and more flexible
150                 system.</para>
151
152                 <para>Some unit names reflect paths existing in the
153                 file system name space. Example: a device unit
154                 <filename>dev-sda.device</filename> refers to a device
155                 with the device node <filename>/dev/sda</filename> in
156                 the file system namespace. If this applies a special
157                 way to escape the path name is used, so that the
158                 result is usable as part of a file name. Basically,
159                 given a path, "/" is replaced by "-", and all
160                 unprintable characters and the "-" are replaced by
161                 C-style "\x20" escapes. The root directory "/" is
162                 encoded as single dash, while otherwise the initial
163                 and ending "/" is removed from all paths during
164                 transformation. This escaping is reversible.</para>
165
166                 <para>Optionally, units may be instantiated from a
167                 template file at runtime. This allows creation of
168                 multiple units from a single configuration file. If
169                 systemd looks for a unit configuration file it will
170                 first search for the literal unit name in the
171                 filesystem. If that yields no success and the unit
172                 name contains an @ character, systemd will look for a
173                 unit template that shares the same name but with the
174                 instance string (i.e. the part between the @ character
175                 and the suffix) removed. Example: if a service
176                 <filename>getty@tty3.service</filename> is requested
177                 and no file by that name is found, systemd will look
178                 for <filename>getty@.service</filename> and
179                 instantiate a service from that configuration file if
180                 it is found. To refer to the instance string from
181                 within the configuration file you may use the special
182                 <literal>%i</literal> specifier in many of the
183                 configuration options. Other specifiers that may be
184                 used are <literal>%n</literal>, <literal>%N</literal>,
185                 <literal>%p</literal>, <literal>%P</literal>,
186                 <literal>%I</literal> and <literal>%f</literal>, for
187                 the full unit name, the unescaped unit name, the
188                 prefix name, the unescaped prefix name, the unescaped
189                 instance name and the unescaped filename,
190                 respectively. The unescaped filename is either the
191                 unescaped instance name (if set) with / prepended (if
192                 necessary), or the prefix name similarly prepended
193                 with /. The prefix name here refers to the string
194                 before the @, i.e. "getty" in the example above, where
195                 "tty3" is the instance name.</para>
196
197                 <para>If a unit file is empty (i.e. has the file size
198                 0) or is symlinked to <filename>/dev/null</filename>
199                 its configuration will not be loaded and it appears
200                 with a load state of <literal>masked</literal>, and
201                 cannot be activated. Use this as an effective way to
202                 fully disable a unit, making it impossible to start it
203                 even manually.</para>
204
205                 <para>The unit file format is covered by the
206                 <ulink
207                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
208                 Stability Promise</ulink>.</para>
209         </refsect1>
210
211         <refsect1>
212                 <title>Options</title>
213
214                 <para>Unit file may include a [Unit] section, which
215                 carries generic information about the unit that is not
216                 dependent on the type of unit:</para>
217
218                 <variablelist>
219                         <varlistentry>
220                                 <term><varname>Names=</varname></term>
221
222                                 <listitem><para>Additional names for
223                                 this unit. The names listed here must
224                                 have the same suffix (i.e. type) as
225                                 the unit file name. This option may be
226                                 specified more than once, in which
227                                 case all listed names are used. Note
228                                 that this option is different from the
229                                 <varname>Alias=</varname> option from
230                                 the [Install] section mentioned
231                                 below. See below for details.</para>
232                                 </listitem>
233                         </varlistentry>
234
235                         <varlistentry>
236                                 <term><varname>Description=</varname></term>
237                                 <listitem><para>A free-form string
238                                 describing the unit. This is intended
239                                 for use in UIs to show descriptive
240                                 information along with the unit
241                                 name.</para></listitem>
242                         </varlistentry>
243
244                         <varlistentry>
245                                 <term><varname>Requires=</varname></term>
246
247                                 <listitem><para>Configures requirement
248                                 dependencies on other units. If this
249                                 unit gets activated, the units listed
250                                 here will be activated as well. If one
251                                 of the other units gets deactivated or
252                                 its activation fails, this unit will
253                                 be deactivated. This option may be
254                                 specified more than once, in which
255                                 case requirement dependencies for all
256                                 listed names are created. Note that
257                                 requirement dependencies do not
258                                 influence the order in which services
259                                 are started or stopped. This has to be
260                                 configured independently with the
261                                 <varname>After=</varname> or
262                                 <varname>Before=</varname> options. If
263                                 a unit
264                                 <filename>foo.service</filename>
265                                 requires a unit
266                                 <filename>bar.service</filename> as
267                                 configured with
268                                 <varname>Requires=</varname> and no
269                                 ordering is configured with
270                                 <varname>After=</varname> or
271                                 <varname>Before=</varname>, then both
272                                 units will be started simultaneously
273                                 and without any delay between them if
274                                 <filename>foo.service</filename> is
275                                 activated. Often it is a better choice
276                                 to use <varname>Wants=</varname>
277                                 instead of
278                                 <varname>Requires=</varname> in order
279                                 to achieve a system that is more
280                                 robust when dealing with failing
281                                 services.</para></listitem>
282                         </varlistentry>
283
284                         <varlistentry>
285                                 <term><varname>RequiresOverridable=</varname></term>
286
287                                 <listitem><para>Similar to
288                                 <varname>Requires=</varname>.
289                                 Dependencies listed in
290                                 <varname>RequiresOverridable=</varname>
291                                 which cannot be fulfilled or fail to
292                                 start are ignored if the startup was
293                                 explicitly requested by the user. If
294                                 the start-up was pulled in indirectly
295                                 by some dependency or automatic
296                                 start-up of units that is not
297                                 requested by the user this dependency
298                                 must be fulfilled and otherwise the
299                                 transaction fails. Hence, this option
300                                 may be used to configure dependencies
301                                 that are normally honored unless the
302                                 user explicitly starts up the unit, in
303                                 which case whether they failed or not
304                                 is irrelevant.</para></listitem>
305
306                         </varlistentry>
307                         <varlistentry>
308                                 <term><varname>Requisite=</varname></term>
309                                 <term><varname>RequisiteOverridable=</varname></term>
310
311                                 <listitem><para>Similar to
312                                 <varname>Requires=</varname>
313                                 resp. <varname>RequiresOverridable=</varname>. However,
314                                 if a unit listed here is not started
315                                 already it will not be started and the
316                                 transaction fails
317                                 immediately.</para></listitem>
318                         </varlistentry>
319
320                         <varlistentry>
321                                 <term><varname>Wants=</varname></term>
322
323                                 <listitem><para>A weaker version of
324                                 <varname>Requires=</varname>. A unit
325                                 listed in this option will be started
326                                 if the configuring unit is. However,
327                                 if the listed unit fails to start up
328                                 or cannot be added to the transaction
329                                 this has no impact on the validity of
330                                 the transaction as a whole. This is
331                                 the recommended way to hook start-up
332                                 of one unit to the start-up of another
333                                 unit. Note that dependencies of this
334                                 type may also be configured outside of
335                                 the unit configuration file by
336                                 adding a symlink to a
337                                 <filename>.wants/</filename> directory
338                                 accompanying the unit file. For
339                                 details see above.</para></listitem>
340                         </varlistentry>
341
342                         <varlistentry>
343                                 <term><varname>BindTo=</varname></term>
344
345                                 <listitem><para>Configures requirement
346                                 dependencies, very similar in style to
347                                 <varname>Requires=</varname>, however
348                                 in addition to this behaviour it also
349                                 declares that this unit is stopped
350                                 when any of the units listed suddenly
351                                 disappears. Units can suddenly,
352                                 unexpectedly disappear if a service
353                                 terminates on its own choice, a device
354                                 is unplugged or a mount point
355                                 unmounted with involvement of
356                                 systemd.</para></listitem>
357                         </varlistentry>
358
359                         <varlistentry>
360                                 <term><varname>Conflicts=</varname></term>
361
362                                 <listitem><para>Configures negative
363                                 requirement dependencies. If a unit
364                                 has a
365                                 <varname>Conflicts=</varname> setting
366                                 on another unit, starting the former
367                                 will stop the latter and vice
368                                 versa. Note that this setting is
369                                 independent of and orthogonal to the
370                                 <varname>After=</varname> and
371                                 <varname>Before=</varname> ordering
372                                 dependencies.</para>
373
374                                 <para>If a unit A that conflicts with
375                                 a unit B is scheduled to be started at
376                                 the same time as B, the transaction
377                                 will either fail (in case both are
378                                 required part of the transaction) or
379                                 be modified to be fixed (in case one
380                                 or both jobs are not a required part
381                                 of the transaction). In the latter
382                                 case the job that is not the required
383                                 will be removed, or in case both are
384                                 not required the unit that conflicts
385                                 will be started and the unit that is
386                                 conflicted is
387                                 stopped.</para></listitem>
388                         </varlistentry>
389
390                         <varlistentry>
391                                 <term><varname>Before=</varname></term>
392                                 <term><varname>After=</varname></term>
393
394                                 <listitem><para>Configures ordering
395                                 dependencies between units. If a unit
396                                 <filename>foo.service</filename>
397                                 contains a setting
398                                 <option>Before=bar.service</option>
399                                 and both units are being started,
400                                 <filename>bar.service</filename>'s
401                                 start-up is delayed until
402                                 <filename>foo.service</filename> is
403                                 started up. Note that this setting is
404                                 independent of and orthogonal to the
405                                 requirement dependencies as configured
406                                 by <varname>Requires=</varname>. It is
407                                 a common pattern to include a unit
408                                 name in both the
409                                 <varname>After=</varname> and
410                                 <varname>Requires=</varname> option in
411                                 which case the unit listed will be
412                                 started before the unit that is
413                                 configured with these options. This
414                                 option may be specified more than
415                                 once, in which case ordering
416                                 dependencies for all listed names are
417                                 created. <varname>After=</varname> is
418                                 the inverse of
419                                 <varname>Before=</varname>, i.e. while
420                                 <varname>After=</varname> ensures that
421                                 the configured unit is started after
422                                 the listed unit finished starting up,
423                                 <varname>Before=</varname> ensures the
424                                 opposite, i.e.  that the configured
425                                 unit is fully started up before the
426                                 listed unit is started. Note that when
427                                 two units with an ordering dependency
428                                 between them are shut down, the
429                                 inverse of the start-up order is
430                                 applied. i.e. if a unit is configured
431                                 with <varname>After=</varname> on
432                                 another unit, the former is stopped
433                                 before the latter if both are shut
434                                 down. If one unit with an ordering
435                                 dependency on another unit is shut
436                                 down while the latter is started up,
437                                 the shut down is ordered before the
438                                 start-up regardless whether the
439                                 ordering dependency is actually of
440                                 type <varname>After=</varname> or
441                                 <varname>Before=</varname>. If two
442                                 units have no ordering dependencies
443                                 between them they are shut down
444                                 resp. started up simultaneously, and
445                                 no ordering takes
446                                 place. </para></listitem>
447                         </varlistentry>
448
449                         <varlistentry>
450                                 <term><varname>OnFailure=</varname></term>
451
452                                 <listitem><para>Lists one or more
453                                 units that are activated when this
454                                 unit enters the
455                                 '<literal>failed</literal>'
456                                 state.</para></listitem>
457                         </varlistentry>
458
459                         <varlistentry>
460                                 <term><varname>StopWhenUnneeded=</varname></term>
461
462                                 <listitem><para>Takes a boolean
463                                 argument. If <option>true</option>
464                                 this unit will be stopped when it is
465                                 no longer used. Note that in order to
466                                 minimize the work to be executed,
467                                 systemd will not stop units by default
468                                 unless they are conflicting with other
469                                 units, or the user explicitly
470                                 requested their shut down. If this
471                                 option is set, a unit will be
472                                 automatically cleaned up if no other
473                                 active unit requires it. Defaults to
474                                 <option>false</option>.</para></listitem>
475                         </varlistentry>
476
477                         <varlistentry>
478                                 <term><varname>RefuseManualStart=</varname></term>
479                                 <term><varname>RefuseManualStop=</varname></term>
480
481                                 <listitem><para>Takes a boolean
482                                 argument. If <option>true</option>
483                                 this unit can only be activated
484                                 (resp. deactivated) indirectly. In
485                                 this case explicit start-up
486                                 (resp. termination) requested by the
487                                 user is denied, however if it is
488                                 started (resp. stopped) as a
489                                 dependency of another unit, start-up
490                                 (resp. termination) will succeed. This
491                                 is mostly a safety feature to ensure
492                                 that the user does not accidentally
493                                 activate units that are not intended
494                                 to be activated explicitly, and not
495                                 accidentally deactivate units that are
496                                 not intended to be deactivated.
497                                 These options default to
498                                 <option>false</option>.</para></listitem>
499                         </varlistentry>
500
501                         <varlistentry>
502                                 <term><varname>AllowIsolate=</varname></term>
503
504                                 <listitem><para>Takes a boolean
505                                 argument. If <option>true</option>
506                                 this unit may be used with the
507                                 <command>systemctl isolate</command>
508                                 command. Otherwise this will be
509                                 refused. It probably is a good idea to
510                                 leave this disabled except for target
511                                 units that shall be used similar to
512                                 runlevels in SysV init systems, just
513                                 as a precaution to avoid unusable
514                                 system states. This option defaults to
515                                 <option>false</option>.</para></listitem>
516                         </varlistentry>
517
518                         <varlistentry>
519                                 <term><varname>DefaultDependencies=</varname></term>
520
521                                 <listitem><para>Takes a boolean
522                                 argument. If <option>true</option>
523                                 (the default), a few default
524                                 dependencies will implicitly be
525                                 created for the unit. The actual
526                                 dependencies created depend on the
527                                 unit type. For example, for service
528                                 units, these dependencies ensure that
529                                 the service is started only after
530                                 basic system initialization is
531                                 completed and is properly terminated on
532                                 system shutdown. See the respective
533                                 man pages for details. Generally, only
534                                 services involved with early boot or
535                                 late shutdown should set this option
536                                 to <option>false</option>. It is
537                                 highly recommended to leave this
538                                 option enabled for the majority of
539                                 common units. If set to
540                                 <option>false</option> this option
541                                 does not disable all implicit
542                                 dependencies, just non-essential
543                                 ones.</para></listitem>
544                         </varlistentry>
545
546                         <varlistentry>
547                                 <term><varname>JobTimeoutSec=</varname></term>
548
549                                 <listitem><para>When clients are
550                                 waiting for a job of this unit to
551                                 complete, time out after the specified
552                                 time. If this time limit is reached
553                                 the job will be cancelled, the unit
554                                 however will not change state or even
555                                 enter the '<literal>failed</literal>'
556                                 mode. This value defaults to 0 (job
557                                 timeouts disabled), except for device
558                                 units. NB: this timeout is independent
559                                 from any unit-specific timeout (for
560                                 example, the timeout set with
561                                 <varname>Timeout=</varname> in service
562                                 units) as the job timeout has no
563                                 effect on the unit itself, only on the
564                                 job that might be pending for it. Or
565                                 in other words: unit-specific timeouts
566                                 are useful to abort unit state
567                                 changes, and revert them. The job
568                                 timeout set with this option however
569                                 is useful to abort only the job
570                                 waiting for the unit state to
571                                 change.</para></listitem>
572                         </varlistentry>
573
574                         <varlistentry>
575                                 <term><varname>ConditionPathExists=</varname></term>
576                                 <term><varname>ConditionKernelCommandLine=</varname></term>
577
578                                 <listitem><para>Before starting a unit
579                                 verify that the specified condition is
580                                 true. With
581                                 <varname>ConditionPathExists=</varname>
582                                 a file existance condition can be
583                                 checked before a unit is started. If
584                                 the specified absolute path name does
585                                 not exist startup of a unit will not
586                                 actually happen, however the unit is
587                                 still useful for ordering purposes in
588                                 this case. The condition is checked at
589                                 the time the queued start job is to be
590                                 executed. If the absolute path name
591                                 passed to
592                                 <varname>ConditionPathExists=</varname>
593                                 is prefixed with an exclamation mark
594                                 (!), the test is negated, and the unit
595                                 only started if the path does not
596                                 exist. Similarly
597                                 <varname>ConditionKernelCommandLine=</varname>
598                                 may be used to check whether a
599                                 specific kernel command line option is
600                                 set (or if prefixed with the
601                                 exclamation mark unset). The argument
602                                 must either be a single word, or an
603                                 assignment (i.e. two words, seperated
604                                 by the equality sign). In the former
605                                 case the kernel command line is search
606                                 for the word appearing as is, or as
607                                 left hand side of an assignment. In
608                                 the latter case the exact assignment
609                                 is looked for with right and left hand
610                                 side matching. If multiple conditions
611                                 are specified the unit will be
612                                 executed iff at least one of them
613                                 applies (i.e. a logical OR is
614                                 applied).</para></listitem>
615                         </varlistentry>
616                 </variablelist>
617
618                 <para>Unit file may include a [Install] section, which
619                 carries installation information for the unit. This
620                 section is not interpreted by
621                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
622                 during runtime. It is used exclusively by the
623                 <command>enable</command> and
624                 <command>disable</command> commands of the
625                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
626                 tool during installation of a unit:</para>
627
628                 <variablelist>
629                         <varlistentry>
630                                 <term><varname>Alias=</varname></term>
631
632                                 <listitem><para>Additional names this
633                                 unit shall be installed under. The
634                                 names listed here must have the same
635                                 suffix (i.e. type) as the unit file
636                                 name. This option may be specified
637                                 more than once, in which case all
638                                 listed names are used. At installation
639                                 time,
640                                 <command>systemctl enable</command>
641                                 will create symlinks from these names
642                                 to the unit file name. Note that this
643                                 is different from the
644                                 <varname>Names=</varname> option from
645                                 the [Unit] section mentioned above:
646                                 The names from
647                                 <varname>Names=</varname> apply
648                                 unconditionally if the unit is
649                                 loaded. The names from
650                                 <varname>Alias=</varname> apply only
651                                 if the unit has actually been
652                                 installed with the
653                                 <command>systemctl enable</command>
654                                 command.  Also, if systemd searches for a
655                                 unit, it will discover symlinked alias
656                                 names as configured with
657                                 <varname>Alias=</varname>, but not
658                                 names configured with
659                                 <varname>Names=</varname> only. It is
660                                 a common pattern to list a name in
661                                 both options. In this case, a unit
662                                 will be active under all names if
663                                 installed, but also if not installed
664                                 but requested explicitly under its
665                                 main name.</para></listitem>
666                         </varlistentry>
667
668                         <varlistentry>
669                                 <term><varname>WantedBy=</varname></term>
670
671                                 <listitem><para>Installs a symlink in
672                                 the <filename>.wants/</filename>
673                                 subdirectory for a unit. This has the
674                                 effect that when the listed unit name
675                                 is activated the unit listing it is
676                                 activated
677                                 too. <command>WantedBy=foo.service</command>
678                                 in a service
679                                 <filename>bar.service</filename> is
680                                 mostly equivalent to
681                                 <command>Alias=foo.service.wants/bar.service</command>
682                                 in the same file.</para></listitem>
683                         </varlistentry>
684
685                         <varlistentry>
686                                 <term><varname>Also=</varname></term>
687
688                                 <listitem><para>Additional units to
689                                 install when this unit is
690                                 installed. If the user requests
691                                 installation of a unit with this
692                                 option configured,
693                                 <command>systemctl enable</command>
694                                 will automatically install units
695                                 listed in this option as
696                                 well.</para></listitem>
697                         </varlistentry>
698                 </variablelist>
699
700         </refsect1>
701
702         <refsect1>
703                 <title>See Also</title>
704                 <para>
705                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
706                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
707                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
708                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
709                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
710                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
711                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
712                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
713                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
714                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
715                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
716                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
717                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>
718                 </para>
719         </refsect1>
720
721 </refentry>