man/systemd.unit.xml

   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> and
 186                 <literal>%I</literal>, for the full unit name, the
 187                 unescaped unit name, the prefix name, the unescaped
 188                 prefix name and the unescaped instance name,
 189                 respectively. The prefix name here refers to the
 190                 string before the @, i.e. "getty" in the example
 191                 above, where "tty3" is the instance name.</para>
 192
 193                 <para>The unit file format is covered by the
 194                 <ulink
 195                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 196                 Stability Promise</ulink>.</para>
 197         </refsect1>
 198
 199         <refsect1>
 200                 <title>Options</title>
 201
 202                 <para>Unit file may include a [Unit] section, which
 203                 carries generic information about the unit that is not
 204                 dependent on the type of unit:</para>
 205
 206                 <variablelist>
 207                         <varlistentry>
 208                                 <term><varname>Names=</varname></term>
 209
 210                                 <listitem><para>Additional names for
 211                                 this unit. The names listed here must
 212                                 have the same suffix (i.e. type) as
 213                                 the unit file name. This option may be
 214                                 specified more than once, in which
 215                                 case all listed names are used. Note
 216                                 that this option is different from the
 217                                 <varname>Alias=</varname> option from
 218                                 the [Install] section mentioned
 219                                 below. See below for details.</para>
 220                                 </listitem>
 221                         </varlistentry>
 222
 223                         <varlistentry>
 224                                 <term><varname>Description=</varname></term>
 225                                 <listitem><para>A free-form string
 226                                 describing the unit. This is intended
 227                                 for use in UIs to show descriptive
 228                                 information along with the unit
 229                                 name.</para></listitem>
 230                         </varlistentry>
 231
 232                         <varlistentry>
 233                                 <term><varname>Requires=</varname></term>
 234
 235                                 <listitem><para>Configures requirement
 236                                 dependencies on other units. If this
 237                                 unit gets activated, the units listed
 238                                 here will be activated as well. If one
 239                                 of the other units gets deactivated or
 240                                 its activation fails, this unit will
 241                                 be deactivated. This option may be
 242                                 specified more than once, in which
 243                                 case requirement dependencies for all
 244                                 listed names are created. Note that
 245                                 requirement dependencies do not
 246                                 influence the order in which services
 247                                 are started or stopped. This has to be
 248                                 configured independently with the
 249                                 <varname>After=</varname> or
 250                                 <varname>Before=</varname> options. If
 251                                 a unit
 252                                 <filename>foo.service</filename>
 253                                 requires a unit
 254                                 <filename>bar.service</filename> as
 255                                 configured with
 256                                 <varname>Requires=</varname> and no
 257                                 ordering is configured with
 258                                 <varname>After=</varname> or
 259                                 <varname>Before=</varname>, then both
 260                                 units will be started simultaneously
 261                                 and without any delay between them if
 262                                 <filename>foo.service</filename> is
 263                                 activated. Often it is a better choice
 264                                 to use <varname>Wants=</varname>
 265                                 instead of
 266                                 <varname>Requires=</varname> in order
 267                                 to achieve a system that is more
 268                                 robust when dealing with failing
 269                                 services.</para></listitem>
 270                         </varlistentry>
 271
 272
 273                         <varlistentry>
 274                                 <term><varname>RequiresOverridable=</varname></term>
 275
 276                                 <listitem><para>Similar to
 277                                 <varname>Requires=</varname>.
 278                                 Dependencies listed in
 279                                 <varname>RequiresOverridable=</varname>
 280                                 which cannot be fulfilled or fail to
 281                                 start are ignored if the startup was
 282                                 explicitly requested by the user. If
 283                                 the start-up was pulled in indirectly
 284                                 by some dependency or automatic
 285                                 start-up of units that is not
 286                                 requested by the user this dependency
 287                                 must be fulfilled and otherwise the
 288                                 transaction fails. Hence, this option
 289                                 may be used to configure dependencies
 290                                 that are normally honored unless the
 291                                 user explicitly starts up the unit, in
 292                                 which case whether they failed or not
 293                                 is irrelevant.</para></listitem>
 294
 295                         </varlistentry>
 296                         <varlistentry>
 297                                 <term><varname>Requisite=</varname></term>
 298                                 <term><varname>RequisiteOverridable=</varname></term>
 299
 300                                 <listitem><para>Similar to
 301                                 <varname>Requires=</varname>
 302                                 resp. <varname>RequiresOverridable=</varname>. However,
 303                                 if a unit listed here is not started
 304                                 already it will not be started and the
 305                                 transaction fails
 306                                 immediately.</para></listitem>
 307                         </varlistentry>
 308
 309                         <varlistentry>
 310                                 <term><varname>Wants=</varname></term>
 311
 312                                 <listitem><para>A weaker version of
 313                                 <varname>Requires=</varname>. A unit
 314                                 listed in this option will be started
 315                                 if the configuring unit is. However,
 316                                 if the listed unit fails to start up
 317                                 or cannot be added to the transaction
 318                                 this has no impact on the validity of
 319                                 the transaction as a whole. This is
 320                                 the recommended way to hook start-up
 321                                 of one unit to the start-up of another
 322                                 unit. Note that dependencies of this
 323                                 type may also be configured outside of
 324                                 the unit configuration file by
 325                                 adding a symlink to a
 326                                 <filename>.wants/</filename> directory
 327                                 accompanying the unit file. For
 328                                 details see above.</para></listitem>
 329                         </varlistentry>
 330
 331                         <varlistentry>
 332                                 <term><varname>Conflicts=</varname></term>
 333
 334                                 <listitem><para>Configures negative
 335                                 requirement dependencies. If a unit
 336                                 has a
 337                                 <varname>Conflicts=</varname> setting
 338                                 on another unit, starting the former
 339                                 will stop the latter and vice
 340                                 versa. Note that this setting is
 341                                 independent of and orthogonal to the
 342                                 <varname>After=</varname> and
 343                                 <varname>Before=</varname> ordering
 344                                 dependencies.</para>
 345
 346                                 <para>If a unit A that conflicts with
 347                                 a unit B is scheduled to be started at
 348                                 the same time as B, the transaction
 349                                 will either fail (in case both are
 350                                 required part of the transaction) or
 351                                 be modified to be fixed (in case one
 352                                 or both jobs are not a required part
 353                                 of the transaction). In the latter
 354                                 case the job that is not the required
 355                                 will be removed, or in case both are
 356                                 not required the unit that conflicts
 357                                 will be started and the unit that is
 358                                 conflicted is
 359                                 stopped.</para></listitem>
 360                         </varlistentry>
 361
 362                         <varlistentry>
 363                                 <term><varname>Before=</varname></term>
 364                                 <term><varname>After=</varname></term>
 365
 366                                 <listitem><para>Configures ordering
 367                                 dependencies between units. If a unit
 368                                 <filename>foo.service</filename>
 369                                 contains a setting
 370                                 <option>Before=bar.service</option>
 371                                 and both units are being started,
 372                                 <filename>bar.service</filename>'s
 373                                 start-up is delayed until
 374                                 <filename>foo.service</filename> is
 375                                 started up. Note that this setting is
 376                                 independent of and orthogonal to the
 377                                 requirement dependencies as configured
 378                                 by <varname>Requires=</varname>. It is
 379                                 a common pattern to include a unit
 380                                 name in both the
 381                                 <varname>After=</varname> and
 382                                 <varname>Requires=</varname> option in
 383                                 which case the unit listed will be
 384                                 started before the unit that is
 385                                 configured with these options. This
 386                                 option may be specified more than
 387                                 once, in which case ordering
 388                                 dependencies for all listed names are
 389                                 created. <varname>After=</varname> is
 390                                 the inverse of
 391                                 <varname>Before=</varname>, i.e. while
 392                                 <varname>After=</varname> ensures that
 393                                 the configured unit is started after
 394                                 the listed unit finished starting up,
 395                                 <varname>Before=</varname> ensures the
 396                                 opposite, i.e.  that the configured
 397                                 unit is fully started up before the
 398                                 listed unit is started. Note that when
 399                                 two units with an ordering dependency
 400                                 between them are shut down, the
 401                                 inverse of the start-up order is
 402                                 applied. i.e. if a unit is configured
 403                                 with <varname>After=</varname> on
 404                                 another unit, the former is stopped
 405                                 before the latter if both are shut
 406                                 down. If one unit with an ordering
 407                                 dependency on another unit is shut
 408                                 down while the latter is started up,
 409                                 the shut down is ordered before the
 410                                 start-up regardless whether the
 411                                 ordering dependency is actually of
 412                                 type <varname>After=</varname> or
 413                                 <varname>Before=</varname>. If two
 414                                 units have no ordering dependencies
 415                                 between them they are shut down
 416                                 resp. started up simultaneously, and
 417                                 no ordering takes
 418                                 place. </para></listitem>
 419                         </varlistentry>
 420
 421                         <varlistentry>
 422                                 <term><varname>OnFailure=</varname></term>
 423
 424                                 <listitem><para>Lists one or more
 425                                 units that are activated when this
 426                                 unit enters the
 427                                 '<literal>failed</literal>'
 428                                 state.</para></listitem>
 429                         </varlistentry>
 430
 431                         <varlistentry>
 432                                 <term><varname>RecursiveStop=</varname></term>
 433
 434                                 <listitem><para>Takes a boolean
 435                                 argument. If <option>true</option> and
 436                                 the unit stops without being requested
 437                                 by the user, all units
 438                                 depending on it will be stopped as
 439                                 well. (e.g. if a service exits or
 440                                 crashes on its own behalf, units using
 441                                 it will be stopped) Note that normally
 442                                 if a unit stops without a user request,
 443                                 units depending on it will not be
 444                                 terminated. Only if the user requested
 445                                 shutdown of a unit, all units depending
 446                                 on that unit will be shut down as well
 447                                 and at the same time. Defaults to
 448                                 <option>false</option>.</para></listitem>
 449                         </varlistentry>
 450
 451                         <varlistentry>
 452                                 <term><varname>StopWhenUnneeded=</varname></term>
 453
 454                                 <listitem><para>Takes a boolean
 455                                 argument. If <option>true</option>
 456                                 this unit will be stopped when it is
 457                                 no longer used. Note that in order to
 458                                 minimize the work to be executed,
 459                                 systemd will not stop units by default
 460                                 unless they are conflicting with other
 461                                 units, or the user explicitly
 462                                 requested their shut down. If this
 463                                 option is set, a unit will be
 464                                 automatically cleaned up if no other
 465                                 active unit requires it. Defaults to
 466                                 <option>false</option>.</para></listitem>
 467                         </varlistentry>
 468
 469                         <varlistentry>
 470                                 <term><varname>RefuseManualStart=</varname></term>
 471                                 <term><varname>RefuseManualStop=</varname></term>
 472
 473                                 <listitem><para>Takes a boolean
 474                                 argument. If <option>true</option>
 475                                 this unit can only be activated
 476                                 (resp. deactivated) indirectly. In
 477                                 this case explicit start-up
 478                                 (resp. termination) requested by the
 479                                 user is denied, however if it is
 480                                 started (resp. stopped) as a
 481                                 dependency of another unit, start-up
 482                                 (resp. termination) will succeed. This
 483                                 is mostly a safety feature to ensure
 484                                 that the user does not accidentally
 485                                 activate units that are not intended
 486                                 to be activated explicitly, and not
 487                                 accidentally deactivate units that are
 488                                 not intended to be deactivated.
 489                                 These options default to
 490                                 <option>false</option>.</para></listitem>
 491                         </varlistentry>
 492
 493                         <varlistentry>
 494                                 <term><varname>AllowIsolate=</varname></term>
 495
 496                                 <listitem><para>Takes a boolean
 497                                 argument. If <option>true</option>
 498                                 this unit may be used with the
 499                                 <command>systemctl isolate</command>
 500                                 command. Otherwise this will be
 501                                 refused. It probably is a good idea to
 502                                 leave this disabled except for target
 503                                 units that shall be used similar to
 504                                 runlevels in SysV init systems, just
 505                                 as a precaution to avoid unusable
 506                                 system states. This option defaults to
 507                                 <option>false</option>.</para></listitem>
 508                         </varlistentry>
 509
 510                         <varlistentry>
 511                                 <term><varname>DefaultDependencies=</varname></term>
 512
 513                                 <listitem><para>Takes a boolean
 514                                 argument. If <option>true</option>
 515                                 (the default), a few default
 516                                 dependencies will implicitly be
 517                                 created for the unit. The actual
 518                                 dependencies created depend on the
 519                                 unit type. For example, for service
 520                                 units, these dependencies ensure that
 521                                 the service is started only after
 522                                 basic system initialization is
 523                                 completed and is properly terminated on
 524                                 system shutdown. See the respective
 525                                 man pages for details. Generally, only
 526                                 services involved with early boot or
 527                                 late shutdown should set this option
 528                                 to <option>false</option>. It is
 529                                 highly recommended to leave this
 530                                 option enabled for the majority of
 531                                 common units. If set to
 532                                 <option>false</option> this option
 533                                 does not disable all implicit
 534                                 dependencies, just non-essential
 535                                 ones.</para></listitem>
 536                         </varlistentry>
 537
 538                         <varlistentry>
 539                                 <term><varname>IgnoreDependencyFailure=</varname></term>
 540
 541                                 <listitem><para>Takes a boolean
 542                                 argument. If <option>true</option> and
 543                                 a requirement dependency of this unit
 544                                 fails to start up this unit will be
 545                                 started nonetheless, ignoring that
 546                                 failure. If <option>false</option>
 547                                 (the default) and a dependency unit
 548                                 fails the unit will immediately fail
 549                                 too and the job is removed.</para></listitem>
 550                         </varlistentry>
 551
 552                         <varlistentry>
 553                                 <term><varname>JobTimeoutSec=</varname></term>
 554
 555                                 <listitem><para>When clients are
 556                                 waiting for a job of this unit to
 557                                 complete, time out after the specified
 558                                 time. If this time limit is reached
 559                                 the job will be cancelled, the unit
 560                                 however will not change state or even
 561                                 enter the '<literal>failed</literal>'
 562                                 mode. This value defaults to 0 (job
 563                                 timeouts disabled), except for device
 564                                 units. NB: this timeout is independent
 565                                 from any unit-specific timeout (for
 566                                 example, the timeout set with
 567                                 <varname>Timeout=</varname> in service
 568                                 units) as the job timeout has no
 569                                 effect on the unit itself, only on the
 570                                 job that might be pending for it. Or
 571                                 in other words: unit-specific timeouts
 572                                 are useful to abort unit state
 573                                 changes, and revert them. The job
 574                                 timeout set with this option however
 575                                 is useful to abort only the job
 576                                 waiting for the unit state to
 577                                 change.</para></listitem>
 578                         </varlistentry>
 579
 580                 </variablelist>
 581
 582                 <para>Unit file may include a [Install] section, which
 583                 carries installation information for the unit. This
 584                 section is not interpreted by
 585                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 586                 during runtime. It is used exclusively by the
 587                 <command>enable</command> and
 588                 <command>disable</command> commands of the
 589                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 590                 tool during installation of a unit:</para>
 591
 592                 <variablelist>
 593                         <varlistentry>
 594                                 <term><varname>Alias=</varname></term>
 595
 596                                 <listitem><para>Additional names this
 597                                 unit shall be installed under. The
 598                                 names listed here must have the same
 599                                 suffix (i.e. type) as the unit file
 600                                 name. This option may be specified
 601                                 more than once, in which case all
 602                                 listed names are used. At installation
 603                                 time,
 604                                 <command>systemctl enable</command>
 605                                 will create symlinks from these names
 606                                 to the unit file name. Note that this
 607                                 is different from the
 608                                 <varname>Names=</varname> option from
 609                                 the [Unit] section mentioned above:
 610                                 The names from
 611                                 <varname>Names=</varname> apply
 612                                 unconditionally if the unit is
 613                                 loaded. The names from
 614                                 <varname>Alias=</varname> apply only
 615                                 if the unit has actually been
 616                                 installed with the
 617                                 <command>systemctl enable</command>
 618                                 command.  Also, if systemd searches for a
 619                                 unit, it will discover symlinked alias
 620                                 names as configured with
 621                                 <varname>Alias=</varname>, but not
 622                                 names configured with
 623                                 <varname>Names=</varname> only. It is
 624                                 a common pattern to list a name in
 625                                 both options. In this case, a unit
 626                                 will be active under all names if
 627                                 installed, but also if not installed
 628                                 but requested explicitly under its
 629                                 main name.</para></listitem>
 630                         </varlistentry>
 631
 632                         <varlistentry>
 633                                 <term><varname>WantedBy=</varname></term>
 634
 635                                 <listitem><para>Installs a symlink in
 636                                 the <filename>.wants/</filename>
 637                                 subdirectory for a unit. This has the
 638                                 effect that when the listed unit name
 639                                 is activated the unit listing it is
 640                                 activated
 641                                 too. <command>WantedBy=foo.service</command>
 642                                 in a service
 643                                 <filename>bar.service</filename> is
 644                                 mostly equivalent to
 645                                 <command>Alias=foo.service.wants/bar.service</command>
 646                                 in the same file.</para></listitem>
 647                         </varlistentry>
 648
 649                         <varlistentry>
 650                                 <term><varname>Also=</varname></term>
 651
 652                                 <listitem><para>Additional units to
 653                                 install when this unit is
 654                                 installed. If the user requests
 655                                 installation of a unit with this
 656                                 option configured,
 657                                 <command>systemctl enable</command>
 658                                 will automatically install units
 659                                 listed in this option as
 660                                 well.</para></listitem>
 661                         </varlistentry>
 662                 </variablelist>
 663
 664         </refsect1>
 665
 666         <refsect1>
 667                 <title>See Also</title>
 668                 <para>
 669                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 670                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 671                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 672                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 673                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 674                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 675                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 676                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 677                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 678                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 679                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 680                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 681                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 682                 </para>
 683         </refsect1>
 684
 685 </refentry>