man/systemd.unit.xml

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   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>$XDG_CONFIG_HOME/systemd/user/*</filename>
  74 <filename>$HOME/.config/systemd/user/*</filename>
  75 <filename>/etc/systemd/user/*</filename>
  76 <filename>/run/systemd/user/*</filename>
  77 <filename>/usr/lib/systemd/user/*</filename>
  78 <filename>...</filename>
  79                 </literallayout></para>
  80         </refsynopsisdiv>
  81
  82         <refsect1>
  83                 <title>Description</title>
  84
  85                 <para>A unit configuration file encodes information
  86                 about a service, a socket, a device, a mount point, an
  87                 automount point, a swap file or partition, a start-up
  88                 target, a watched file system path, a timer controlled
  89                 and supervised by
  90                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  91                 a temporary system state snapshot, a resource
  92                 management slice or a group of externally created
  93                 processes. The syntax is inspired by <ulink
  94                 url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
  95                 Desktop Entry Specification</ulink>
  96                 <filename>.desktop</filename> files, which are in turn
  97                 inspired by Microsoft Windows
  98                 <filename>.ini</filename> files.</para>
  99
 100                 <para>This man page lists the common configuration
 101                 options of all the unit types. These options need to
 102                 be configured in the [Unit] or [Install]
 103                 sections of the unit files.</para>
 104
 105                 <para>In addition to the generic [Unit] and [Install]
 106                 sections described here, each unit may have a
 107                 type-specific section, e.g. [Service] for a service
 108                 unit. See the respective man pages for more
 109                 information:
 110                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 111                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 112                 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 113                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 114                 <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 115                 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 116                 <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 117                 <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 118                 <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 119                 <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 120                 <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 121                 <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 122                 </para>
 123
 124                 <para>Various settings are allowed to be specified
 125                 more than once, in which case the interpretation
 126                 depends on the setting. Often, multiple settings form
 127                 a list, and setting to an empty value "resets", which
 128                 means that previous assignments are ignored. When this
 129                 is allowed, it is mentioned in the description of the
 130                 setting. Note that using multiple assignments to the
 131                 same value makes the unit file incompatible with
 132                 parsers for the XDG <filename>.desktop</filename> file
 133                 format.</para>
 134
 135                 <para>Unit files are loaded from a set of paths
 136                 determined during compilation, described in the next section.
 137                 </para>
 138
 139                 <para>Unit files may contain additional options on top
 140                 of those listed here. If systemd encounters an unknown
 141                 option, it will write a warning log message but
 142                 continue loading the unit. If an option or section name
 143                 is prefixed with <option>X-</option>, it is ignored
 144                 completely by systemd. Options within an ignored
 145                 section do not need the prefix. Applications may use
 146                 this to include additional information in the unit
 147                 files.</para>
 148
 149                 <para>Boolean arguments used in unit files can be
 150                 written in various formats. For positive settings the
 151                 strings <option>1</option>, <option>yes</option>,
 152                 <option>true</option> and <option>on</option> are
 153                 equivalent. For negative settings, the strings
 154                 <option>0</option>, <option>no</option>,
 155                 <option>false</option> and <option>off</option> are
 156                 equivalent.</para>
 157
 158                 <para>Time span values encoded in unit files can be
 159                 written in various formats. A stand-alone number
 160                 specifies a time in seconds. If suffixed with a time
 161                 unit, the unit is honored. A concatenation of multiple
 162                 values with units is supported, in which case the
 163                 values are added up. Example: "50" refers to 50
 164                 seconds; "2min 200ms" refers to 2 minutes plus 200
 165                 milliseconds, i.e. 120200ms. The following time units
 166                 are understood: s, min, h, d, w, ms, us. For details
 167                 see
 168                 <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 169
 170                 <para>Empty lines and lines starting with # or ; are
 171                 ignored. This may be used for commenting. Lines ending
 172                 in a backslash are concatenated with the following
 173                 line while reading and the backslash is replaced by a
 174                 space character. This may be used to wrap long lines.</para>
 175
 176                 <para>Along with a unit file
 177                 <filename>foo.service</filename>, the directory
 178                 <filename>foo.service.wants/</filename> may exist. All
 179                 unit files symlinked from such a directory are
 180                 implicitly added as dependencies of type
 181                 <varname>Wanted=</varname> to the unit. This is useful
 182                 to hook units into the start-up of other units,
 183                 without having to modify their unit files. For details
 184                 about the semantics of <varname>Wanted=</varname>, see
 185                 below. The preferred way to create symlinks in the
 186                 <filename>.wants/</filename> directory of a unit file
 187                 is with the <command>enable</command> command of the
 188                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 189                 tool which reads information from the [Install]
 190                 section of unit files (see below). A similar
 191                 functionality exists for <varname>Requires=</varname>
 192                 type dependencies as well, the directory suffix is
 193                 <filename>.requires/</filename> in this case.</para>
 194
 195                 <para>Along with a unit file
 196                 <filename>foo.service</filename>, a directory
 197                 <filename>foo.service.d/</filename> may exist. All
 198                 files with the suffix <literal>.conf</literal> from
 199                 this directory will be parsed after the file itself is
 200                 parsed. This is useful to alter or add configuration
 201                 settings to a unit, without having to modify their
 202                 unit files. Make sure that the file that is included
 203                 has the appropriate section headers before any
 204                 directive.</para>
 205
 206                 <para>Note that while systemd offers a flexible
 207                 dependency system between units it is recommended to
 208                 use this functionality only sparingly and instead rely
 209                 on techniques such as bus-based or socket-based
 210                 activation which make dependencies implicit, resulting
 211                 in a both simpler and more flexible system.</para>
 212
 213                 <para>Some unit names reflect paths existing in the
 214                 file system namespace. Example: a device unit
 215                 <filename>dev-sda.device</filename> refers to a device
 216                 with the device node <filename noindex='true'>/dev/sda</filename> in
 217                 the file system namespace. If this applies, a special
 218                 way to escape the path name is used, so that the
 219                 result is usable as part of a filename. Basically,
 220                 given a path, "/" is replaced by "-", and all
 221                 unprintable characters and the "-" are replaced by
 222                 C-style "\x20" escapes. The root directory "/" is
 223                 encoded as single dash, while otherwise the initial
 224                 and ending "/" is removed from all paths during
 225                 transformation. This escaping is reversible.</para>
 226
 227                 <para>Optionally, units may be instantiated from a
 228                 template file at runtime. This allows creation of
 229                 multiple units from a single configuration file. If
 230                 systemd looks for a unit configuration file, it will
 231                 first search for the literal unit name in the
 232                 file system. If that yields no success and the unit
 233                 name contains an <literal>@</literal> character, systemd will look for a
 234                 unit template that shares the same name but with the
 235                 instance string (i.e. the part between the <literal>@</literal> character
 236                 and the suffix) removed. Example: if a service
 237                 <filename>getty@tty3.service</filename> is requested
 238                 and no file by that name is found, systemd will look
 239                 for <filename>getty@.service</filename> and
 240                 instantiate a service from that configuration file if
 241                 it is found.</para>
 242
 243                 <para>To refer to the instance string from
 244                 within the configuration file you may use the special
 245                 <literal>%i</literal> specifier in many of the
 246                 configuration options. See below for details.</para>
 247
 248                 <para>If a unit file is empty (i.e. has the file size
 249                 0) or is symlinked to <filename>/dev/null</filename>,
 250                 its configuration will not be loaded and it appears
 251                 with a load state of <literal>masked</literal>, and
 252                 cannot be activated. Use this as an effective way to
 253                 fully disable a unit, making it impossible to start it
 254                 even manually.</para>
 255
 256                 <para>The unit file format is covered by the
 257                 <ulink
 258                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 259                 Stability Promise</ulink>.</para>
 260
 261         </refsect1>
 262
 263         <refsect1>
 264                 <title>Unit Load Path</title>
 265
 266                 <para>Unit files are loaded from a set of paths
 267                 determined during compilation, described in the two
 268                 tables below. Unit files found in directories listed
 269                 earlier override files with the same name in
 270                 directories lower in the list.</para>
 271
 272                 <para>When systemd is running in user mode
 273                 (<option>--user</option>) and the variable
 274                 <varname>$SYSTEMD_UNIT_PATH</varname> is set, this
 275                 contents of this variable overrides the unit load
 276                 path.
 277                 </para>
 278
 279                 <table>
 280                   <title>
 281                     Load path when running in system mode (<option>--system</option>).
 282                   </title>
 283
 284                   <tgroup cols='2'>
 285                     <colspec colname='path' />
 286                     <colspec colname='expl' />
 287                     <thead>
 288                       <row>
 289                         <entry>Path</entry>
 290                         <entry>Description</entry>
 291                       </row>
 292                     </thead>
 293                     <tbody>
 294                       <row>
 295                         <entry><filename>/etc/systemd/system</filename></entry>
 296                         <entry>Local configuration</entry>
 297                       </row>
 298                       <row>
 299                         <entry><filename>/run/systemd/system</filename></entry>
 300                         <entry>Runtime units</entry>
 301                       </row>
 302                       <row>
 303                         <entry><filename>/usr/lib/systemd/system</filename></entry>
 304                         <entry>Units of installed packages</entry>
 305                       </row>
 306                     </tbody>
 307                   </tgroup>
 308                 </table>
 309
 310                 <table>
 311                   <title>
 312                     Load path when running in user mode (<option>--user</option>).
 313                   </title>
 314
 315                   <tgroup cols='2'>
 316                     <colspec colname='path' />
 317                     <colspec colname='expl' />
 318                     <thead>
 319                       <row>
 320                         <entry>Path</entry>
 321                         <entry>Description</entry>
 322                       </row>
 323                     </thead>
 324                     <tbody>
 325                       <row>
 326                         <entry><filename>$XDG_CONFIG_HOME/systemd/user</filename></entry>
 327                         <entry>User configuration (only used when $XDG_CONFIG_HOME is set)</entry>
 328                       </row>
 329                       <row>
 330                         <entry><filename>$HOME/.config/systemd/user</filename></entry>
 331                         <entry>User configuration (only used when $XDG_CONFIG_HOME is not set)</entry>
 332                       </row>
 333                       <row>
 334                         <entry><filename>/etc/systemd/user</filename></entry>
 335                         <entry>Local configuration</entry>
 336                       </row>
 337                       <row>
 338                         <entry><filename>/run/systemd/user</filename></entry>
 339                         <entry>Runtime units</entry>
 340                       </row>
 341                       <row>
 342                         <entry><filename>/usr/lib/systemd/user</filename></entry>
 343                         <entry>Units of installed packages</entry>
 344                       </row>
 345                     </tbody>
 346                   </tgroup>
 347                 </table>
 348
 349                 <para>Additional units might be loaded into systemd
 350                 ("linked") from directories not on the unit load
 351                 path. See the <command>link</command> command for
 352                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>. Also,
 353                 some units are dynamically created via generators
 354                 <ulink
 355                 url="http://www.freedesktop.org/wiki/Software/systemd/Generators/">Generators</ulink>.
 356                 </para>
 357         </refsect1>
 358
 359         <refsect1>
 360                 <title>[Unit] Section Options</title>
 361
 362                 <para>Unit file may include a [Unit] section, which
 363                 carries generic information about the unit that is not
 364                 dependent on the type of unit:</para>
 365
 366                 <variablelist class='unit-directives'>
 367
 368                         <varlistentry>
 369                                 <term><varname>Description=</varname></term>
 370                                 <listitem><para>A free-form string
 371                                 describing the unit. This is intended
 372                                 for use in UIs to show descriptive
 373                                 information along with the unit
 374                                 name. The description should contain a name
 375                                 that means something to the end user.
 376                                 <literal>Apache2 Web Server</literal> is a good
 377                                 example. Bad examples are
 378                                 <literal>high-performance light-weight HTTP
 379                                 server</literal> (too generic) or
 380                                 <literal>Apache2</literal> (too specific and
 381                                 meaningless for people who do not know
 382                                 Apache).</para></listitem>
 383                         </varlistentry>
 384
 385                         <varlistentry>
 386                                 <term><varname>Documentation=</varname></term>
 387                                 <listitem><para>A space-separated list
 388                                 of URIs referencing documentation for
 389                                 this unit or its
 390                                 configuration. Accepted are only URIs
 391                                 of the types
 392                                 <literal>http://</literal>,
 393                                 <literal>https://</literal>,
 394                                 <literal>file:</literal>,
 395                                 <literal>info:</literal>,
 396                                 <literal>man:</literal>. For more
 397                                 information about the syntax of these
 398                                 URIs, see
 399                                 <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
 400                                 URIs should be listed in order of
 401                                 relevance, starting with the most
 402                                 relevant. It is a good idea to first
 403                                 reference documentation that explains
 404                                 what the unit's purpose is, followed
 405                                 by how it is configured, followed by
 406                                 any other related documentation. This
 407                                 option may be specified more than once,
 408                                 in which case the specified list of
 409                                 URIs is merged. If the empty string is
 410                                 assigned to this option, the list is
 411                                 reset and all prior assignments will
 412                                 have no effect.</para></listitem>
 413                         </varlistentry>
 414
 415                         <varlistentry>
 416                                 <term><varname>Requires=</varname></term>
 417
 418                                 <listitem><para>Configures requirement
 419                                 dependencies on other units. If this
 420                                 unit gets activated, the units listed
 421                                 here will be activated as well. If one
 422                                 of the other units gets deactivated or
 423                                 its activation fails, this unit will
 424                                 be deactivated. This option may be
 425                                 specified more than once or multiple
 426                                 space-separated units may be specified
 427                                 in one option in which case
 428                                 requirement dependencies for all
 429                                 listed names will be created. Note
 430                                 that requirement dependencies do not
 431                                 influence the order in which services
 432                                 are started or stopped. This has to be
 433                                 configured independently with the
 434                                 <varname>After=</varname> or
 435                                 <varname>Before=</varname> options. If
 436                                 a unit
 437                                 <filename>foo.service</filename>
 438                                 requires a unit
 439                                 <filename>bar.service</filename> as
 440                                 configured with
 441                                 <varname>Requires=</varname> and no
 442                                 ordering is configured with
 443                                 <varname>After=</varname> or
 444                                 <varname>Before=</varname>, then both
 445                                 units will be started simultaneously
 446                                 and without any delay between them if
 447                                 <filename>foo.service</filename> is
 448                                 activated. Often it is a better choice
 449                                 to use <varname>Wants=</varname>
 450                                 instead of
 451                                 <varname>Requires=</varname> in order
 452                                 to achieve a system that is more
 453                                 robust when dealing with failing
 454                                 services.</para>
 455
 456                                 <para>Note that dependencies of this
 457                                 type may also be configured outside of
 458                                 the unit configuration file by
 459                                 adding a symlink to a
 460                                 <filename>.requires/</filename> directory
 461                                 accompanying the unit file. For
 462                                 details see above.</para></listitem>
 463                         </varlistentry>
 464
 465                         <varlistentry>
 466                                 <term><varname>RequiresOverridable=</varname></term>
 467
 468                                 <listitem><para>Similar to
 469                                 <varname>Requires=</varname>.
 470                                 Dependencies listed in
 471                                 <varname>RequiresOverridable=</varname>
 472                                 which cannot be fulfilled or fail to
 473                                 start are ignored if the startup was
 474                                 explicitly requested by the user. If
 475                                 the start-up was pulled in indirectly
 476                                 by some dependency or automatic
 477                                 start-up of units that is not
 478                                 requested by the user, this dependency
 479                                 must be fulfilled and otherwise the
 480                                 transaction fails. Hence, this option
 481                                 may be used to configure dependencies
 482                                 that are normally honored unless the
 483                                 user explicitly starts up the unit, in
 484                                 which case whether they failed or not
 485                                 is irrelevant.</para></listitem>
 486
 487                         </varlistentry>
 488                         <varlistentry>
 489                                 <term><varname>Requisite=</varname></term>
 490                                 <term><varname>RequisiteOverridable=</varname></term>
 491
 492                                 <listitem><para>Similar to
 493                                 <varname>Requires=</varname> and
 494                                 <varname>RequiresOverridable=</varname>,
 495                                 respectively. However, if the units
 496                                 listed here are not started already,
 497                                 they will not be started and the
 498                                 transaction will fail immediately.
 499                                 </para></listitem>
 500                         </varlistentry>
 501
 502                         <varlistentry>
 503                                 <term><varname>Wants=</varname></term>
 504
 505                                 <listitem><para>A weaker version of
 506                                 <varname>Requires=</varname>. Units
 507                                 listed in this option will be started
 508                                 if the configuring unit is. However,
 509                                 if the listed units fail to start
 510                                 or cannot be added to the transaction,
 511                                 this has no impact on the validity of
 512                                 the transaction as a whole. This is
 513                                 the recommended way to hook start-up
 514                                 of one unit to the start-up of another
 515                                 unit.</para>
 516
 517                                 <para>Note that dependencies of this
 518                                 type may also be configured outside of
 519                                 the unit configuration file by adding
 520                                 symlinks to a
 521                                 <filename>.wants/</filename> directory
 522                                 accompanying the unit file. For
 523                                 details, see above.</para></listitem>
 524                         </varlistentry>
 525
 526                         <varlistentry>
 527                                 <term><varname>BindsTo=</varname></term>
 528
 529                                 <listitem><para>Configures requirement
 530                                 dependencies, very similar in style to
 531                                 <varname>Requires=</varname>, however
 532                                 in addition to this behavior, it also
 533                                 declares that this unit is stopped
 534                                 when any of the units listed suddenly
 535                                 disappears. Units can suddenly,
 536                                 unexpectedly disappear if a service
 537                                 terminates on its own choice, a device
 538                                 is unplugged or a mount point
 539                                 unmounted without involvement of
 540                                 systemd.</para></listitem>
 541                         </varlistentry>
 542
 543                         <varlistentry>
 544                                 <term><varname>PartOf=</varname></term>
 545
 546                                 <listitem><para>Configures dependencies
 547                                 similar to <varname>Requires=</varname>,
 548                                 but limited to stopping and restarting
 549                                 of units. When systemd stops or restarts
 550                                 the units listed here, the action is
 551                                 propagated to this unit.
 552                                 Note that this is a one-way dependency —
 553                                 changes to this unit do not affect the
 554                                 listed units.
 555                                 </para></listitem>
 556                         </varlistentry>
 557
 558                         <varlistentry>
 559                                 <term><varname>Conflicts=</varname></term>
 560
 561                                 <listitem><para>A space-separated list
 562                                 of unit names. Configures negative
 563                                 requirement dependencies. If a unit
 564                                 has a <varname>Conflicts=</varname>
 565                                 setting on another unit, starting the
 566                                 former will stop the latter and vice
 567                                 versa. Note that this setting is
 568                                 independent of and orthogonal to the
 569                                 <varname>After=</varname> and
 570                                 <varname>Before=</varname> ordering
 571                                 dependencies.</para>
 572
 573                                 <para>If a unit A that conflicts with
 574                                 a unit B is scheduled to be started at
 575                                 the same time as B, the transaction
 576                                 will either fail (in case both are
 577                                 required part of the transaction) or
 578                                 be modified to be fixed (in case one
 579                                 or both jobs are not a required part
 580                                 of the transaction). In the latter
 581                                 case, the job that is not the required
 582                                 will be removed, or in case both are
 583                                 not required, the unit that conflicts
 584                                 will be started and the unit that is
 585                                 conflicted is
 586                                 stopped.</para></listitem>
 587                         </varlistentry>
 588
 589                         <varlistentry>
 590                                 <term><varname>Before=</varname></term>
 591                                 <term><varname>After=</varname></term>
 592
 593                                 <listitem><para>A space-separated list
 594                                 of unit names. Configures ordering
 595                                 dependencies between units. If a unit
 596                                 <filename>foo.service</filename>
 597                                 contains a setting
 598                                 <option>Before=bar.service</option>
 599                                 and both units are being started,
 600                                 <filename>bar.service</filename>'s
 601                                 start-up is delayed until
 602                                 <filename>foo.service</filename> is
 603                                 started up. Note that this setting is
 604                                 independent of and orthogonal to the
 605                                 requirement dependencies as configured
 606                                 by <varname>Requires=</varname>. It is
 607                                 a common pattern to include a unit
 608                                 name in both the
 609                                 <varname>After=</varname> and
 610                                 <varname>Requires=</varname> option, in
 611                                 which case the unit listed will be
 612                                 started before the unit that is
 613                                 configured with these options. This
 614                                 option may be specified more than
 615                                 once, in which case ordering
 616                                 dependencies for all listed names are
 617                                 created. <varname>After=</varname> is
 618                                 the inverse of
 619                                 <varname>Before=</varname>, i.e. while
 620                                 <varname>After=</varname> ensures that
 621                                 the configured unit is started after
 622                                 the listed unit finished starting up,
 623                                 <varname>Before=</varname> ensures the
 624                                 opposite, i.e.  that the configured
 625                                 unit is fully started up before the
 626                                 listed unit is started. Note that when
 627                                 two units with an ordering dependency
 628                                 between them are shut down, the
 629                                 inverse of the start-up order is
 630                                 applied. i.e. if a unit is configured
 631                                 with <varname>After=</varname> on
 632                                 another unit, the former is stopped
 633                                 before the latter if both are shut
 634                                 down. If one unit with an ordering
 635                                 dependency on another unit is shut
 636                                 down while the latter is started up,
 637                                 the shut down is ordered before the
 638                                 start-up regardless of whether the
 639                                 ordering dependency is actually of
 640                                 type <varname>After=</varname> or
 641                                 <varname>Before=</varname>. If two
 642                                 units have no ordering dependencies
 643                                 between them, they are shut down or
 644                                 started up simultaneously, and no
 645                                 ordering takes
 646                                 place. </para></listitem>
 647                         </varlistentry>
 648
 649                         <varlistentry>
 650                                 <term><varname>OnFailure=</varname></term>
 651
 652                                 <listitem><para>A space-separated list
 653                                 of one or more units that are
 654                                 activated when this unit enters the
 655                                 <literal>failed</literal>
 656                                 state.</para></listitem>
 657                         </varlistentry>
 658
 659                         <varlistentry>
 660                                 <term><varname>PropagatesReloadTo=</varname></term>
 661                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 662
 663                                 <listitem><para>A space-separated list
 664                                 of one or more units where reload
 665                                 requests on this unit will be
 666                                 propagated to, or reload requests on
 667                                 the other unit will be propagated to
 668                                 this unit, respectively. Issuing a
 669                                 reload request on a unit will
 670                                 automatically also enqueue a reload
 671                                 request on all units that the reload
 672                                 request shall be propagated to via
 673                                 these two settings.</para></listitem>
 674                         </varlistentry>
 675
 676                         <varlistentry>
 677                                 <term><varname>JoinsNamespaceOf=</varname></term>
 678
 679                                 <listitem><para>For units that start
 680                                 processes (such as service units),
 681                                 lists one or more other units whose
 682                                 network and/or temporary file
 683                                 namespace to join. This only applies
 684                                 to unit types which support the
 685                                 <varname>PrivateNetwork=</varname> and
 686                                 <varname>PrivateTmp=</varname>
 687                                 directives (see
 688                                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 689                                 for details). If a unit that has this
 690                                 setting set is started, its processes
 691                                 will see the same
 692                                 <filename>/tmp</filename>,
 693                                 <filename>/tmp/var</filename> and
 694                                 network namespace as one listed unit
 695                                 that is started. If multiple listed
 696                                 units are already started, it is not
 697                                 defined which namespace is
 698                                 joined. Note that this setting only
 699                                 has an effect if
 700                                 <varname>PrivateNetwork=</varname>
 701                                 and/or <varname>PrivateTmp=</varname>
 702                                 is enabled for both the unit that
 703                                 joins the namespace and the unit whose
 704                                 namespace is joined.</para></listitem>
 705                         </varlistentry>
 706
 707                         <varlistentry>
 708                                 <term><varname>RequiresMountsFor=</varname></term>
 709
 710                                 <listitem><para>Takes a
 711                                 space-separated list of absolute
 712                                 paths. Automatically adds dependencies
 713                                 of type <varname>Requires=</varname>
 714                                 and <varname>After=</varname> for all
 715                                 mount units required to access the
 716                                 specified path.</para>
 717
 718                                 <para>Mount points marked with
 719                                 <option>noauto</option> are not
 720                                 mounted automatically and will be
 721                                 ignored for the purposes of this
 722                                 option. If such a mount should be a
 723                                 requirement for this unit,
 724                                 direct dependencies on the mount
 725                                 units may be added
 726                                 (<varname>Requires=</varname> and
 727                                 <varname>After=</varname> or
 728                                 some other combination).
 729                                 </para></listitem>
 730                         </varlistentry>
 731
 732                         <varlistentry>
 733                                 <term><varname>OnFailureJobMode=</varname></term>
 734
 735                                 <listitem><para>Takes a value of
 736                                 <literal>fail</literal>,
 737                                 <literal>replace</literal>,
 738                                 <literal>replace-irreversibly</literal>,
 739                                 <literal>isolate</literal>,
 740                                 <literal>flush</literal>,
 741                                 <literal>ignore-dependencies</literal>
 742                                 or
 743                                 <literal>ignore-requirements</literal>. Defaults
 744                                 to
 745                                 <literal>replace</literal>. Specifies
 746                                 how the units listed in
 747                                 <varname>OnFailure=</varname> will be
 748                                 enqueued. See
 749                                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
 750                                 <option>--job-mode=</option> option
 751                                 for details on the possible values. If
 752                                 this is set to
 753                                 <literal>isolate</literal>, only a
 754                                 single unit may be listed in
 755                                 <varname>OnFailure=</varname>..</para></listitem>
 756                         </varlistentry>
 757
 758                         <varlistentry>
 759                                 <term><varname>IgnoreOnIsolate=</varname></term>
 760
 761                                 <listitem><para>Takes a boolean
 762                                 argument. If <option>true</option>,
 763                                 this unit will not be stopped when
 764                                 isolating another unit. Defaults to
 765                                 <option>false</option>.</para></listitem>
 766                         </varlistentry>
 767
 768                         <varlistentry>
 769                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 770
 771                                 <listitem><para>Takes a boolean
 772                                 argument. If <option>true</option>,
 773                                 this unit will not be included in
 774                                 snapshots. Defaults to
 775                                 <option>true</option> for device and
 776                                 snapshot units, <option>false</option>
 777                                 for the others.</para></listitem>
 778                         </varlistentry>
 779
 780                         <varlistentry>
 781                                 <term><varname>StopWhenUnneeded=</varname></term>
 782
 783                                 <listitem><para>Takes a boolean
 784                                 argument. If <option>true</option>,
 785                                 this unit will be stopped when it is
 786                                 no longer used. Note that in order to
 787                                 minimize the work to be executed,
 788                                 systemd will not stop units by default
 789                                 unless they are conflicting with other
 790                                 units, or the user explicitly
 791                                 requested their shut down. If this
 792                                 option is set, a unit will be
 793                                 automatically cleaned up if no other
 794                                 active unit requires it. Defaults to
 795                                 <option>false</option>.</para></listitem>
 796                         </varlistentry>
 797
 798                         <varlistentry>
 799                                 <term><varname>RefuseManualStart=</varname></term>
 800                                 <term><varname>RefuseManualStop=</varname></term>
 801
 802                                 <listitem><para>Takes a boolean
 803                                 argument. If <option>true</option>,
 804                                 this unit can only be activated
 805                                 or deactivated indirectly. In
 806                                 this case, explicit start-up
 807                                 or termination requested by the
 808                                 user is denied, however if it is
 809                                 started or stopped as a
 810                                 dependency of another unit, start-up
 811                                 or termination will succeed. This
 812                                 is mostly a safety feature to ensure
 813                                 that the user does not accidentally
 814                                 activate units that are not intended
 815                                 to be activated explicitly, and not
 816                                 accidentally deactivate units that are
 817                                 not intended to be deactivated.
 818                                 These options default to
 819                                 <option>false</option>.</para></listitem>
 820                         </varlistentry>
 821
 822                         <varlistentry>
 823                                 <term><varname>AllowIsolate=</varname></term>
 824
 825                                 <listitem><para>Takes a boolean
 826                                 argument. If <option>true</option>,
 827                                 this unit may be used with the
 828                                 <command>systemctl isolate</command>
 829                                 command. Otherwise, this will be
 830                                 refused. It probably is a good idea to
 831                                 leave this disabled except for target
 832                                 units that shall be used similar to
 833                                 runlevels in SysV init systems, just
 834                                 as a precaution to avoid unusable
 835                                 system states. This option defaults to
 836                                 <option>false</option>.</para></listitem>
 837                         </varlistentry>
 838
 839                         <varlistentry>
 840                                 <term><varname>DefaultDependencies=</varname></term>
 841
 842                                 <listitem><para>Takes a boolean
 843                                 argument. If <option>true</option>,
 844                                 (the default), a few default
 845                                 dependencies will implicitly be
 846                                 created for the unit. The actual
 847                                 dependencies created depend on the
 848                                 unit type. For example, for service
 849                                 units, these dependencies ensure that
 850                                 the service is started only after
 851                                 basic system initialization is
 852                                 completed and is properly terminated on
 853                                 system shutdown. See the respective
 854                                 man pages for details. Generally, only
 855                                 services involved with early boot or
 856                                 late shutdown should set this option
 857                                 to <option>false</option>. It is
 858                                 highly recommended to leave this
 859                                 option enabled for the majority of
 860                                 common units. If set to
 861                                 <option>false</option>, this option
 862                                 does not disable all implicit
 863                                 dependencies, just non-essential
 864                                 ones.</para></listitem>
 865                         </varlistentry>
 866
 867                         <varlistentry>
 868                                 <term><varname>JobTimeoutSec=</varname></term>
 869
 870                                 <listitem><para>When clients are
 871                                 waiting for a job of this unit to
 872                                 complete, time out after the specified
 873                                 time. If this time limit is reached,
 874                                 the job will be cancelled, the unit
 875                                 however will not change state or even
 876                                 enter the <literal>failed</literal>
 877                                 mode. This value defaults to 0 (job
 878                                 timeouts disabled), except for device
 879                                 units. NB: this timeout is independent
 880                                 from any unit-specific timeout (for
 881                                 example, the timeout set with
 882                                 <varname>Timeout=</varname> in service
 883                                 units) as the job timeout has no
 884                                 effect on the unit itself, only on the
 885                                 job that might be pending for it. Or
 886                                 in other words: unit-specific timeouts
 887                                 are useful to abort unit state
 888                                 changes, and revert them. The job
 889                                 timeout set with this option however
 890                                 is useful to abort only the job
 891                                 waiting for the unit state to
 892                                 change.</para></listitem>
 893                         </varlistentry>
 894
 895                         <varlistentry>
 896                                 <term><varname>ConditionArchitecture=</varname></term>
 897                                 <term><varname>ConditionVirtualization=</varname></term>
 898                                 <term><varname>ConditionHost=</varname></term>
 899                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 900                                 <term><varname>ConditionSecurity=</varname></term>
 901                                 <term><varname>ConditionCapability=</varname></term>
 902                                 <term><varname>ConditionACPower=</varname></term>
 903                                 <term><varname>ConditionPathExists=</varname></term>
 904                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 905                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 906                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 907                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 908                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 909                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 910                                 <term><varname>ConditionFileNotEmpty=</varname></term>
 911                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 912                                 <term><varname>ConditionNull=</varname></term>
 913
 914                                 <listitem><para>Before starting a unit
 915                                 verify that the specified condition is
 916                                 true. If it is not true, the starting
 917                                 of the unit will be skipped, however
 918                                 all ordering dependencies of it are
 919                                 still respected. A failing condition
 920                                 will not result in the unit being
 921                                 moved into a failure state. The
 922                                 condition is checked at the time the
 923                                 queued start job is to be
 924                                 executed.</para>
 925
 926                                 <para><varname>ConditionArchitecture=</varname>
 927                                 may be used to check whether the
 928                                 system is running on a specific
 929                                 architecture. Takes one of
 930                                 <varname>x86</varname>,
 931                                 <varname>x86-64</varname>,
 932                                 <varname>ppc</varname>,
 933                                 <varname>ppc64</varname>,
 934                                 <varname>ia64</varname>,
 935                                 <varname>parisc</varname>,
 936                                 <varname>parisc64</varname>,
 937                                 <varname>s390</varname>,
 938                                 <varname>s390x</varname>,
 939                                 <varname>sparc</varname>,
 940                                 <varname>sparc64</varname>,
 941                                 <varname>mips</varname>,
 942                                 <varname>mips64</varname>,
 943                                 <varname>alpha</varname>,
 944                                 <varname>arm</varname>,
 945                                 <varname>arm-be</varname>,
 946                                 <varname>arm64</varname>,
 947                                 <varname>arm64-be</varname>,
 948                                 <varname>sh</varname>,
 949                                 <varname>sh64</varname>,
 950                                 <varname>m86k</varname> to test
 951                                 against a specific architecture. The
 952                                 architecture is determined from the
 953                                 information returned by
 954                                 <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 955                                 and is thus subject to
 956                                 <citerefentry><refentrytitle>personality</refentrytitle><manvolnum>2</manvolnum></citerefentry>. Note
 957                                 that a <varname>Personality=</varname>
 958                                 setting in the same unit file has no
 959                                 effect on this condition. A special
 960                                 architecture name
 961                                 <varname>native</varname> is mapped to
 962                                 the architecture the system manager
 963                                 itself is compiled for. The test may
 964                                 be negated by prepending an
 965                                 exclamation mark.</para>
 966
 967                                 <para><varname>ConditionVirtualization=</varname>
 968                                 may be used to check whether the
 969                                 system is executed in a virtualized
 970                                 environment and optionally test
 971                                 whether it is a specific
 972                                 implementation. Takes either boolean
 973                                 value to check if being executed in
 974                                 any virtualized environment, or one of
 975                                 <varname>vm</varname> and
 976                                 <varname>container</varname> to test
 977                                 against a generic type of
 978                                 virtualization solution, or one of
 979                                 <varname>qemu</varname>,
 980                                 <varname>kvm</varname>,
 981                                 <varname>vmware</varname>,
 982                                 <varname>microsoft</varname>,
 983                                 <varname>oracle</varname>,
 984                                 <varname>xen</varname>,
 985                                 <varname>bochs</varname>,
 986                                 <varname>chroot</varname>,
 987                                 <varname>uml</varname>,
 988                                 <varname>openvz</varname>,
 989                                 <varname>lxc</varname>,
 990                                 <varname>lxc-libvirt</varname>,
 991                                 <varname>systemd-nspawn</varname> to
 992                                 test against a specific
 993                                 implementation. If multiple
 994                                 virtualization technologies are nested,
 995                                 only the innermost is considered. The
 996                                 test may be negated by prepending an
 997                                 exclamation mark.</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>ConditionKernelCommandLine=</varname>
1014                                 may be used to check whether a
1015                                 specific kernel command line option is
1016                                 set (or if prefixed with the
1017                                 exclamation mark unset). The argument
1018                                 must either be a single word, or an
1019                                 assignment (i.e. two words, separated
1020                                 <literal>=</literal>). In the former
1021                                 case the kernel command line is
1022                                 searched for the word appearing as is,
1023                                 or as left hand side of an
1024                                 assignment. In the latter case, the
1025                                 exact assignment is looked for with
1026                                 right and left hand side
1027                                 matching.</para>
1028
1029                                 <para><varname>ConditionSecurity=</varname>
1030                                 may be used to check whether the given
1031                                 security module is enabled on the
1032                                 system. Currently the recognized values
1033                                 values are <varname>selinux</varname>,
1034                                 <varname>apparmor</varname>,
1035                                 <varname>ima</varname> and
1036                                 <varname>smack</varname>.
1037                                 The test may be negated by prepending
1038                                 an exclamation
1039                                 mark.</para>
1040
1041                                 <para><varname>ConditionCapability=</varname>
1042                                 may be used to check whether the given
1043                                 capability exists in the capability
1044                                 bounding set of the service manager
1045                                 (i.e. this does not check whether
1046                                 capability is actually available in
1047                                 the permitted or effective sets, see
1048                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1049                                 for details). Pass a capability name
1050                                 such as <literal>CAP_MKNOD</literal>,
1051                                 possibly prefixed with an exclamation
1052                                 mark to negate the check.</para>
1053
1054                                 <para><varname>ConditionACPower=</varname>
1055                                 may be used to check whether the
1056                                 system has AC power, or is exclusively
1057                                 battery powered at the time of
1058                                 activation of the unit. This takes a
1059                                 boolean argument. If set to
1060                                 <varname>true</varname>, the condition
1061                                 will hold only if at least one AC
1062                                 connector of the system is connected
1063                                 to a power source, or if no AC
1064                                 connectors are known. Conversely, if
1065                                 set to <varname>false</varname>, the
1066                                 condition will hold only if there is
1067                                 at least one AC connector known and
1068                                 all AC connectors are disconnected
1069                                 from a power source.</para>
1070
1071                                 <para>With
1072                                 <varname>ConditionPathExists=</varname>
1073                                 a file existence condition is
1074                                 checked before a unit is started. If
1075                                 the specified absolute path name does
1076                                 not exist, the condition will
1077                                 fail. If the absolute path name passed
1078                                 to
1079                                 <varname>ConditionPathExists=</varname>
1080                                 is prefixed with an exclamation mark
1081                                 (<literal>!</literal>), the test is negated, and the unit
1082                                 is only started if the path does not
1083                                 exist.</para>
1084
1085                                 <para><varname>ConditionPathExistsGlob=</varname>
1086                                 is similar to
1087                                 <varname>ConditionPathExists=</varname>,
1088                                 but checks for the existence of at
1089                                 least one file or directory matching
1090                                 the specified globbing pattern.</para>
1091
1092                                 <para><varname>ConditionPathIsDirectory=</varname>
1093                                 is similar to
1094                                 <varname>ConditionPathExists=</varname>
1095                                 but verifies whether a certain path
1096                                 exists and is a
1097                                 directory.</para>
1098
1099                                 <para><varname>ConditionPathIsSymbolicLink=</varname>
1100                                 is similar to
1101                                 <varname>ConditionPathExists=</varname>
1102                                 but verifies whether a certain path
1103                                 exists and is a symbolic
1104                                 link.</para>
1105
1106                                 <para><varname>ConditionPathIsMountPoint=</varname>
1107                                 is similar to
1108                                 <varname>ConditionPathExists=</varname>
1109                                 but verifies whether a certain path
1110                                 exists and is a mount
1111                                 point.</para>
1112
1113                                 <para><varname>ConditionPathIsReadWrite=</varname>
1114                                 is similar to
1115                                 <varname>ConditionPathExists=</varname>
1116                                 but verifies whether the underlying
1117                                 file system is readable and writable
1118                                 (i.e. not mounted
1119                                 read-only).</para>
1120
1121                                 <para><varname>ConditionDirectoryNotEmpty=</varname>
1122                                 is similar to
1123                                 <varname>ConditionPathExists=</varname>
1124                                 but verifies whether a certain path
1125                                 exists and is a non-empty
1126                                 directory.</para>
1127
1128                                 <para><varname>ConditionFileNotEmpty=</varname>
1129                                 is similar to
1130                                 <varname>ConditionPathExists=</varname>
1131                                 but verifies whether a certain path
1132                                 exists and refers to a regular file
1133                                 with a non-zero size.</para>
1134
1135                                 <para><varname>ConditionFileIsExecutable=</varname>
1136                                 is similar to
1137                                 <varname>ConditionPathExists=</varname>
1138                                 but verifies whether a certain path
1139                                 exists, is a regular file and marked
1140                                 executable.</para>
1141
1142                                 <para>Finally,
1143                                 <varname>ConditionNull=</varname> may
1144                                 be used to add a constant condition
1145                                 check value to the unit. It takes a
1146                                 boolean argument. If set to
1147                                 <varname>false</varname>, the condition
1148                                 will always fail, otherwise
1149                                 succeed.</para>
1150
1151                                 <para>If multiple conditions are
1152                                 specified, the unit will be executed if
1153                                 all of them apply (i.e. a logical AND
1154                                 is applied). Condition checks can be
1155                                 prefixed with a pipe symbol (|) in
1156                                 which case a condition becomes a
1157                                 triggering condition. If at least one
1158                                 triggering condition is defined for a
1159                                 unit, then the unit will be executed if
1160                                 at least one of the triggering
1161                                 conditions apply and all of the
1162                                 non-triggering conditions. If you
1163                                 prefix an argument with the pipe
1164                                 symbol and an exclamation mark, the
1165                                 pipe symbol must be passed first, the
1166                                 exclamation second. Except for
1167                                 <varname>ConditionPathIsSymbolicLink=</varname>,
1168                                 all path checks follow symlinks. If
1169                                 any of these options is assigned the
1170                                 empty string, the list of conditions is
1171                                 reset completely, all previous
1172                                 condition settings (of any kind) will
1173                                 have no effect.</para></listitem>
1174                         </varlistentry>
1175
1176                         <varlistentry>
1177                                 <term><varname>SourcePath=</varname></term>
1178                                 <listitem><para>A path to a
1179                                 configuration file this unit has been
1180                                 generated from. This is primarily
1181                                 useful for implementation of generator
1182                                 tools that convert configuration from
1183                                 an external configuration file format
1184                                 into native unit files. This
1185                                 functionality should not be used in
1186                                 normal units.</para></listitem>
1187                         </varlistentry>
1188                 </variablelist>
1189
1190         </refsect1>
1191
1192         <refsect1>
1193                 <title>[Install] Section Options</title>
1194
1195                 <para>Unit file may include a [Install] section, which
1196                 carries installation information for the unit. This
1197                 section is not interpreted by
1198                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1199                 during runtime. It is used exclusively by the
1200                 <command>enable</command> and
1201                 <command>disable</command> commands of the
1202                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1203                 tool during installation of a unit:</para>
1204
1205                 <variablelist class='unit-directives'>
1206                         <varlistentry>
1207                                 <term><varname>Alias=</varname></term>
1208
1209                                 <listitem><para>A space-seperated list
1210                                 of additional names this unit shall be
1211                                 installed under. The names listed here
1212                                 must have the same suffix (i.e. type)
1213                                 as the unit file name. This option may
1214                                 be specified more than once, in which
1215                                 case all listed names are used. At
1216                                 installation time, <command>systemctl
1217                                 enable</command> will create symlinks
1218                                 from these names to the unit
1219                                 filename.</para></listitem>
1220                         </varlistentry>
1221
1222                         <varlistentry>
1223                                 <term><varname>WantedBy=</varname></term>
1224                                 <term><varname>RequiredBy=</varname></term>
1225
1226                                 <listitem><para>This option may be
1227                                 used more than once, or a
1228                                 space-separated list of unit names may
1229                                 be given. A symbolic link is created
1230                                 in the <filename>.wants/</filename> or
1231                                 <filename>.requires/</filename>
1232                                 directory of each of the listed units
1233                                 when this unit is installed by
1234                                 <command>systemctl enable</command>.
1235                                 This has the effect that a dependency
1236                                 of type <varname>Wants=</varname> or
1237                                 <varname>Requires=</varname> is added
1238                                 from the listed unit to the current
1239                                 unit. The primary result is that the
1240                                 current unit will be started when the
1241                                 listed unit is started. See the
1242                                 description of
1243                                 <varname>Wants=</varname> and
1244                                 <varname>Requires=</varname> in the
1245                                 [Unit] section for details.</para>
1246
1247                                 <para><command>WantedBy=foo.service</command>
1248                                 in a service
1249                                 <filename>bar.service</filename> is
1250                                 mostly equivalent to
1251                                 <command>Alias=foo.service.wants/bar.service</command>
1252                                 in the same file. In case of template
1253                                 units, <command>systemctl enable</command>
1254                                 must be called with an instance name, and
1255                                 this instance will be added to the
1256                                 <filename>.wants/</filename> or
1257                                 <filename>.requires/</filename> list
1258                                 of the listed unit.
1259                                 E.g. <command>WantedBy=getty.target</command>
1260                                 in a service
1261                                 <filename>getty@.service</filename>
1262                                 will result in <command>systemctl
1263                                 enable getty@tty2.service</command>
1264                                 creating a
1265                                 <filename>getty.target.wants/getty@tty2.service</filename>
1266                                 link to <filename>getty@.service</filename>.
1267                                 </para></listitem>
1268                         </varlistentry>
1269
1270                         <varlistentry>
1271                                 <term><varname>Also=</varname></term>
1272
1273                                 <listitem><para>Additional units to
1274                                 install/deinstall when this unit is
1275                                 installed/deinstalled. If the user
1276                                 requests installation/deinstallation
1277                                 of a unit with this option configured,
1278                                 <command>systemctl enable</command>
1279                                 and <command>systemctl
1280                                 disable</command> will automatically
1281                                 install/uninstall units listed in this option as
1282                                 well.</para>
1283
1284                                 <para>This option may be used more
1285                                 than once, or a space-separated list
1286                                 of unit names may be
1287                                 given.</para></listitem>
1288                         </varlistentry>
1289
1290                         <varlistentry>
1291                                 <term><varname>DefaultInstance=</varname></term>
1292
1293                                 <listitem><para>In template unit files,
1294                                 this specifies for which instance the
1295                                 unit shall be enabled if the template
1296                                 is enabled without any explicitly set
1297                                 instance. This option has no effect in
1298                                 non-template unit files. The specified
1299                                 string must be usable as instance
1300                                 identifier.</para></listitem>
1301                         </varlistentry>
1302                 </variablelist>
1303
1304                 <para>The following specifiers are interpreted in the
1305                 Install section: %n, %N, %p, %i, %U, %u, %m, %H, %b, %v.
1306                 For their meaning see the next section.
1307                 </para>
1308         </refsect1>
1309
1310         <refsect1>
1311                 <title>Specifiers</title>
1312
1313                 <para>Many settings resolve specifiers which may be
1314                 used to write generic unit files referring to runtime
1315                 or unit parameters that are replaced when the unit
1316                 files are loaded. The following specifiers are
1317                 understood:</para>
1318
1319                 <table>
1320                   <title>Specifiers available in unit files</title>
1321                   <tgroup cols='3' align='left' colsep='1' rowsep='1'>
1322                     <colspec colname="spec" />
1323                     <colspec colname="mean" />
1324                     <colspec colname="detail" />
1325                     <thead>
1326                       <row>
1327                         <entry>Specifier</entry>
1328                         <entry>Meaning</entry>
1329                         <entry>Details</entry>
1330                       </row>
1331                     </thead>
1332                     <tbody>
1333                       <row>
1334                         <entry><literal>%n</literal></entry>
1335                         <entry>Full unit name</entry>
1336                         <entry></entry>
1337                       </row>
1338                       <row>
1339                         <entry><literal>%N</literal></entry>
1340                         <entry>Unescaped full unit name</entry>
1341                         <entry>Same as <literal>%n</literal>, but with escaping undone</entry>
1342                       </row>
1343                       <row>
1344                         <entry><literal>%p</literal></entry>
1345                         <entry>Prefix name</entry>
1346                         <entry>For instantiated units, this refers to the string before the <literal>@</literal> character of the unit name. For non-instantiated units, this refers to the name of the unit with the type suffix removed.</entry>
1347                       </row>
1348                       <row>
1349                         <entry><literal>%P</literal></entry>
1350                         <entry>Unescaped prefix name</entry>
1351                         <entry>Same as <literal>%p</literal>, but with escaping undone</entry>
1352                       </row>
1353                       <row>
1354                         <entry><literal>%i</literal></entry>
1355                         <entry>Instance name</entry>
1356                         <entry>For instantiated units: this is the string between the <literal>@</literal> character and the suffix of the unit name.</entry>
1357                       </row>
1358                       <row>
1359                         <entry><literal>%I</literal></entry>
1360                         <entry>Unescaped instance name</entry>
1361                         <entry>Same as <literal>%i</literal>, but with escaping undone</entry>
1362                       </row>
1363                       <row>
1364                         <entry><literal>%f</literal></entry>
1365                         <entry>Unescaped filename</entry>
1366                         <entry>This is either the unescaped instance name (if applicable) with <filename>/</filename> prepended (if applicable), or the prefix name prepended with <filename>/</filename>.</entry>
1367                       </row>
1368                       <row>
1369                         <entry><literal>%c</literal></entry>
1370                         <entry>Control group path of the unit</entry>
1371                         <entry>This path does not include the <filename>/sys/fs/cgroup/systemd/</filename> prefix.</entry>
1372                       </row>
1373                       <row>
1374                         <entry><literal>%r</literal></entry>
1375                         <entry>Control group path of the slice the unit is placed in</entry>
1376                         <entry>This usually maps to the parent cgroup path of <literal>%c</literal>.</entry>
1377                       </row>
1378                       <row>
1379                         <entry><literal>%R</literal></entry>
1380                         <entry>Root control group path below which slices and units are placed</entry>
1381                         <entry>For system instances, this resolves to <filename>/</filename>, except in containers, where this maps to the container's root control group path.</entry>
1382                       </row>
1383                       <row>
1384                         <entry><literal>%t</literal></entry>
1385                         <entry>Runtime directory</entry>
1386                         <entry>This is either <filename>/run</filename> (for the system manager) or the path <literal>$XDG_RUNTIME_DIR</literal> resolves to (for user managers).</entry>
1387                       </row>
1388                       <row>
1389                         <entry><literal>%u</literal></entry>
1390                         <entry>User name</entry>
1391                         <entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1392                       </row>
1393                       <row>
1394                         <entry><literal>%U</literal></entry>
1395                         <entry>User UID</entry>
1396                         <entry>This is the numeric UID of the configured user of the unit, or (if none is set) the user running the systemd user instance. Note that this specifier is not available for units run by the systemd system instance (as opposed to those run by a systemd user instance), unless the user has been configured as a numeric UID in the first place or the configured user is the root user.</entry>
1397                       </row>
1398                       <row>
1399                         <entry><literal>%h</literal></entry>
1400                         <entry>User home directory</entry>
1401                         <entry>This is the home directory of the configured user of the unit, or (if none is set) the user running the systemd user instance. Similar to <literal>%U</literal>, this specifier is not available for units run by the systemd system instance, unless the configured user is the root user.</entry>
1402                       </row>
1403                       <row>
1404                         <entry><literal>%s</literal></entry>
1405                         <entry>User shell</entry>
1406                         <entry>This is the shell of the configured user of the unit, or (if none is set) the user running the systemd user instance. Similar to <literal>%U</literal>, this specifier is not available for units run by the systemd system instance, unless the configured user is the root user.</entry>
1407                       </row>
1408                       <row>
1409                         <entry><literal>%m</literal></entry>
1410                         <entry>Machine ID</entry>
1411                         <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>
1412                       </row>
1413                       <row>
1414                         <entry><literal>%b</literal></entry>
1415                         <entry>Boot ID</entry>
1416                         <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
1417                       </row>
1418                       <row>
1419                         <entry><literal>%H</literal></entry>
1420                         <entry>Host name</entry>
1421                         <entry>The hostname of the running system at the point in time the unit configuation is loaded.</entry>
1422                       </row>
1423                       <row>
1424                         <entry><literal>%v</literal></entry>
1425                         <entry>Kernel release</entry>
1426                         <entry>Identical to <command>uname -r</command> output</entry>
1427                       </row>
1428                       <row>
1429                         <entry><literal>%%</literal></entry>
1430                         <entry>Single percent sign</entry>
1431                         <entry>Use <literal>%%</literal> in place of <literal>%</literal> to specify a single percent sign.</entry>
1432                       </row>
1433                     </tbody>
1434                   </tgroup>
1435                 </table>
1436         </refsect1>
1437
1438         <refsect1>
1439                 <title>See Also</title>
1440                 <para>
1441                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1442                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1443                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1444                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1445                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1446                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1447                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1448                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1449                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1450                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1451                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1452                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1453                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1454                         <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1455                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1456                         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1457                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1458                         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1459                         <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1460                 </para>
1461         </refsect1>
1462
1463 </refentry>