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