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>/etc/systemd/user/*</filename>
  74 <filename>/run/systemd/user/*</filename>
  75 <filename>/usr/lib/systemd/user/*</filename>
  76 <filename>...</filename>
  77                 </literallayout></para>
  78         </refsynopsisdiv>
  79
  80         <refsect1>
  81                 <title>Description</title>
  82
  83                 <para>A unit configuration file encodes information
  84                 about a service, a socket, a device, a mount point, an
  85                 automount point, a swap file or partition, a start-up
  86                 target, a watched file system path, a timer controlled
  87                 and supervised by
  88                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  89                 a temporary system state snapshot, a resource
  90                 management slice or a group of externally created
  91                 processes. The syntax is inspired by <ulink
  92                 url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
  93                 Desktop Entry Specification</ulink>
  94                 <filename>.desktop</filename> files, which are in turn
  95                 inspired by Microsoft Windows
  96                 <filename>.ini</filename> files.</para>
  97
  98                 <para>This man page lists the common configuration
  99                 options of all the unit types. These options need to
 100                 be configured in the [Unit] or [Install]
 101                 sections of the unit files.</para>
 102
 103                 <para>In addition to the generic [Unit] and [Install]
 104                 sections described here, each unit may have a
 105                 type-specific section, e.g. [Service] for a service
 106                 unit. See the respective man pages for more
 107                 information:
 108                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 109                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 110                 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 111                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 112                 <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 113                 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 114                 <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 115                 <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 116                 <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 117                 <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 118                 <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 119                 <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 120                 </para>
 121
 122                 <para>Unit files are loaded from a set of paths
 123                 determined during compilation, described in the next section.
 124                 </para>
 125
 126                 <para>Unit files may contain additional options on top
 127                 of those listed here. If systemd encounters an unknown
 128                 option it will write a warning log message but
 129                 continue loading the unit. If an option is prefixed
 130                 with <option>X-</option> it is ignored completely by
 131                 systemd. Applications may use this to include
 132                 additional information in the unit files.</para>
 133
 134                 <para>Boolean arguments used in unit files can be
 135                 written in various formats. For positive settings the
 136                 strings <option>1</option>, <option>yes</option>,
 137                 <option>true</option> and <option>on</option> are
 138                 equivalent. For negative settings the strings
 139                 <option>0</option>, <option>no</option>,
 140                 <option>false</option> and <option>off</option> are
 141                 equivalent.</para>
 142
 143                 <para>Time span values encoded in unit files can be
 144                 written in various formats. A stand-alone number
 145                 specifies a time in seconds. If suffixed with a time
 146                 unit, the unit is honored. A concatenation of multiple
 147                 values with units is supported, in which case the
 148                 values are added up. Example: "50" refers to 50
 149                 seconds; "2min 200ms" refers to 2 minutes plus 200
 150                 milliseconds, i.e. 120200ms. The following time units
 151                 are understood: s, min, h, d, w, ms, us. For details
 152                 see
 153                 <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 154
 155                 <para>Empty lines and lines starting with # or ; are
 156                 ignored. This may be used for commenting. Lines ending
 157                 in a backslash are concatenated with the following
 158                 line while reading and the backslash is replaced by a
 159                 space character. This may be used to wrap long lines.</para>
 160
 161                 <para>Along with a unit file
 162                 <filename>foo.service</filename> the directory
 163                 <filename>foo.service.wants/</filename> may exist. All
 164                 unit files symlinked from such a directory are
 165                 implicitly added as dependencies of type
 166                 <varname>Wanted=</varname> to the unit. This is useful
 167                 to hook units into the start-up of other units,
 168                 without having to modify their unit files. For details
 169                 about the semantics of <varname>Wanted=</varname> see
 170                 below. The preferred way to create symlinks in the
 171                 <filename>.wants/</filename> directory of a unit file
 172                 is with the <command>enable</command> command of the
 173                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 174                 tool which reads information from the [Install]
 175                 section of unit files (see below). A similar
 176                 functionality exists for <varname>Requires=</varname>
 177                 type dependencies as well, the directory suffix is
 178                 <filename>.requires/</filename> in this case.</para>
 179
 180                 <para>Along with a unit file
 181                 <filename>foo.service</filename> a directory
 182                 <filename>foo.service.d/</filename> may exist. All
 183                 files with the suffix <literal>.conf</literal> from
 184                 this directory will be parsed after the file itself is
 185                 parsed. This is useful to alter or add configuration
 186                 settings to a unit, without having to modify their
 187                 unit files. Make sure that the file that is included
 188                 has the appropriate section headers before any
 189                 directive.</para>
 190
 191                 <para>If a line starts with <option>.include</option>
 192                 followed by a filename, the specified file will be
 193                 parsed at this point. Make sure that the file that is
 194                 included has the appropriate section headers before
 195                 any directives.</para>
 196
 197                 <para>Note that while systemd offers a flexible
 198                 dependency system between units it is recommended to
 199                 use this functionality only sparingly and instead rely
 200                 on techniques such as bus-based or socket-based
 201                 activation which make dependencies implicit, resulting
 202                 in a both simpler and more flexible system.</para>
 203
 204                 <para>Some unit names reflect paths existing in the
 205                 file system namespace. Example: a device unit
 206                 <filename>dev-sda.device</filename> refers to a device
 207                 with the device node <filename noindex='true'>/dev/sda</filename> in
 208                 the file system namespace. If this applies a special
 209                 way to escape the path name is used, so that the
 210                 result is usable as part of a filename. Basically,
 211                 given a path, "/" is replaced by "-", and all
 212                 unprintable characters and the "-" are replaced by
 213                 C-style "\x20" escapes. The root directory "/" is
 214                 encoded as single dash, while otherwise the initial
 215                 and ending "/" is removed from all paths during
 216                 transformation. This escaping is reversible.</para>
 217
 218                 <para>Optionally, units may be instantiated from a
 219                 template file at runtime. This allows creation of
 220                 multiple units from a single configuration file. If
 221                 systemd looks for a unit configuration file it will
 222                 first search for the literal unit name in the
 223                 filesystem. If that yields no success and the unit
 224                 name contains an <literal>@</literal> character, systemd will look for a
 225                 unit template that shares the same name but with the
 226                 instance string (i.e. the part between the <literal>@</literal> character
 227                 and the suffix) removed. Example: if a service
 228                 <filename>getty@tty3.service</filename> is requested
 229                 and no file by that name is found, systemd will look
 230                 for <filename>getty@.service</filename> and
 231                 instantiate a service from that configuration file if
 232                 it is found.</para>
 233
 234                 <para>To refer to the instance string from
 235                 within the configuration file you may use the special
 236                 <literal>%i</literal> specifier in many of the
 237                 configuration options. See below for details.</para>
 238
 239                 <para>If a unit file is empty (i.e. has the file size
 240                 0) or is symlinked to <filename>/dev/null</filename>
 241                 its configuration will not be loaded and it appears
 242                 with a load state of <literal>masked</literal>, and
 243                 cannot be activated. Use this as an effective way to
 244                 fully disable a unit, making it impossible to start it
 245                 even manually.</para>
 246
 247                 <para>The unit file format is covered by the
 248                 <ulink
 249                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 250                 Stability Promise</ulink>.</para>
 251
 252         </refsect1>
 253
 254         <refsect1>
 255                 <title>Unit Load Path</title>
 256
 257                 <para>Unit files are loaded from a set of paths
 258                 determined during compilation, described in the two
 259                 tables below. Unit files found in directories higher
 260                 in the hierarchy override files with the same name
 261                 lower in the hierarchy, thus allowing overrides.
 262                 </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>/run/systemd/generator.early</filename></entry>
 288                         <entry>Generated units (early)</entry>
 289                       </row>
 290                       <row>
 291                         <entry><filename>/etc/systemd/system</filename></entry>
 292                         <entry>Local configuration</entry>
 293                       </row>
 294                       <row>
 295                         <entry><filename>/run/systemd/system</filename></entry>
 296                         <entry>Volatile units</entry>
 297                       </row>
 298                       <row>
 299                         <entry><filename>/run/systemd/generator</filename></entry>
 300                         <entry>Generated units (middle)</entry>
 301                       </row>
 302                       <row>
 303                         <entry><filename>/usr/local/lib/systemd/system</filename></entry>
 304                         <entry>Units for local packages</entry>
 305                       </row>
 306                       <row>
 307                         <entry><filename>/usr/lib/systemd/system</filename></entry>
 308                         <entry>Units for installed packages</entry>
 309                       </row>
 310                       <row>
 311                         <entry><filename>/run/systemd/generator.late</filename></entry>
 312                         <entry>Generated units (late)</entry>
 313                       </row>
 314                     </tbody>
 315                   </tgroup>
 316                 </table>
 317
 318                 <table>
 319                   <title>
 320                     Load path when running in session mode (<option>--user</option>).
 321                   </title>
 322
 323                   <tgroup cols='2'>
 324                     <colspec colname='path' />
 325                     <colspec colname='expl' />
 326                     <thead>
 327                       <row>
 328                         <entry>Path</entry>
 329                         <entry>Description</entry>
 330                       </row>
 331                     </thead>
 332                     <tbody>
 333                       <row>
 334                         <entry><filename>/tmp/systemd-generator.early.<replaceable>XXXXXX</replaceable></filename></entry>
 335                         <entry>Generated units (early)</entry>
 336                       </row>
 337                       <row>
 338                         <entry><filename>/etc/systemd/user</filename></entry>
 339                         <entry>Local configuration</entry>
 340                       </row>
 341                       <row>
 342                         <entry><filename>/run/systemd/user</filename></entry>
 343                         <entry>Volatile units</entry>
 344                       </row>
 345                       <row>
 346                         <entry><filename>/tmp/systemd-generator.<replaceable>XXXXXX</replaceable></filename></entry>
 347                         <entry>Generated units (middle)</entry>
 348                       </row>
 349                       <row>
 350                         <entry><filename>/usr/local/lib/systemd/user</filename></entry>
 351                         <entry>Units for local packages</entry>
 352                       </row>
 353                       <row>
 354                         <entry><filename>/usr/lib/systemd/user</filename></entry>
 355                         <entry>Units for installed packages</entry>
 356                       </row>
 357                       <row>
 358                         <entry><filename>/tmp/systemd-generator.late.<replaceable>XXXXXX</replaceable></filename></entry>
 359                         <entry>Generated units (late)</entry>
 360                       </row>
 361                     </tbody>
 362                   </tgroup>
 363                 </table>
 364
 365                 <para>Additional units might be loaded into systemd
 366                 ("linked") from directories not on the unit load
 367                 path. See the <command>link</command> command for
 368                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 369                 </para>
 370         </refsect1>
 371
 372         <refsect1>
 373                 <title>Options</title>
 374
 375                 <para>Unit file may include a [Unit] section, which
 376                 carries generic information about the unit that is not
 377                 dependent on the type of unit:</para>
 378
 379                 <variablelist class='unit-directives'>
 380
 381                         <varlistentry>
 382                                 <term><varname>Description=</varname></term>
 383                                 <listitem><para>A free-form string
 384                                 describing the unit. This is intended
 385                                 for use in UIs to show descriptive
 386                                 information along with the unit
 387                                 name.</para></listitem>
 388                         </varlistentry>
 389
 390                         <varlistentry>
 391                                 <term><varname>Documentation=</varname></term>
 392                                 <listitem><para>A space-separated list
 393                                 of URIs referencing documentation for
 394                                 this unit or its
 395                                 configuration. Accepted are only URIs
 396                                 of the types
 397                                 <literal>http://</literal>,
 398                                 <literal>https://</literal>,
 399                                 <literal>file:</literal>,
 400                                 <literal>info:</literal>,
 401                                 <literal>man:</literal>. For more
 402                                 information about the syntax of these
 403                                 URIs, see
 404                                 <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
 405                                 URIs should be listed in order of
 406                                 relevance, starting with the most
 407                                 relevant. It is a good idea to first
 408                                 reference documentation that explains
 409                                 what the unit's purpose is, followed
 410                                 by how it is configured, followed by
 411                                 any other related documentation. This
 412                                 option may be specified more than once
 413                                 in which case the specified list of
 414                                 URIs is merged. If the empty string is
 415                                 assigned to this option, the list is
 416                                 reset and all prior assignments will
 417                                 have no effect.</para></listitem>
 418                         </varlistentry>
 419
 420                         <varlistentry>
 421                                 <term><varname>Requires=</varname></term>
 422
 423                                 <listitem><para>Configures requirement
 424                                 dependencies on other units. If this
 425                                 unit gets activated, the units listed
 426                                 here will be activated as well. If one
 427                                 of the other units gets deactivated or
 428                                 its activation fails, this unit will
 429                                 be deactivated. This option may be
 430                                 specified more than once, in which
 431                                 case requirement dependencies for all
 432                                 listed names are created. Note that
 433                                 requirement dependencies do not
 434                                 influence the order in which services
 435                                 are started or stopped. This has to be
 436                                 configured independently with the
 437                                 <varname>After=</varname> or
 438                                 <varname>Before=</varname> options. If
 439                                 a unit
 440                                 <filename>foo.service</filename>
 441                                 requires a unit
 442                                 <filename>bar.service</filename> as
 443                                 configured with
 444                                 <varname>Requires=</varname> and no
 445                                 ordering is configured with
 446                                 <varname>After=</varname> or
 447                                 <varname>Before=</varname>, then both
 448                                 units will be started simultaneously
 449                                 and without any delay between them if
 450                                 <filename>foo.service</filename> is
 451                                 activated. Often it is a better choice
 452                                 to use <varname>Wants=</varname>
 453                                 instead of
 454                                 <varname>Requires=</varname> in order
 455                                 to achieve a system that is more
 456                                 robust when dealing with failing
 457                                 services.</para>
 458
 459                                 <para>Note that dependencies of this
 460                                 type may also be configured outside of
 461                                 the unit configuration file by
 462                                 adding a symlink to a
 463                                 <filename>.requires/</filename> directory
 464                                 accompanying the unit file. For
 465                                 details see above.</para></listitem>
 466                         </varlistentry>
 467
 468                         <varlistentry>
 469                                 <term><varname>RequiresOverridable=</varname></term>
 470
 471                                 <listitem><para>Similar to
 472                                 <varname>Requires=</varname>.
 473                                 Dependencies listed in
 474                                 <varname>RequiresOverridable=</varname>
 475                                 which cannot be fulfilled or fail to
 476                                 start are ignored if the startup was
 477                                 explicitly requested by the user. If
 478                                 the start-up was pulled in indirectly
 479                                 by some dependency or automatic
 480                                 start-up of units that is not
 481                                 requested by the user this dependency
 482                                 must be fulfilled and otherwise the
 483                                 transaction fails. Hence, this option
 484                                 may be used to configure dependencies
 485                                 that are normally honored unless the
 486                                 user explicitly starts up the unit, in
 487                                 which case whether they failed or not
 488                                 is irrelevant.</para></listitem>
 489
 490                         </varlistentry>
 491                         <varlistentry>
 492                                 <term><varname>Requisite=</varname></term>
 493                                 <term><varname>RequisiteOverridable=</varname></term>
 494
 495                                 <listitem><para>Similar to
 496                                 <varname>Requires=</varname>
 497                                 and <varname>RequiresOverridable=</varname>, respectively. However,
 498                                 if a unit listed here is not started
 499                                 already it will not be started and the
 500                                 transaction fails
 501                                 immediately.</para></listitem>
 502                         </varlistentry>
 503
 504                         <varlistentry>
 505                                 <term><varname>Wants=</varname></term>
 506
 507                                 <listitem><para>A weaker version of
 508                                 <varname>Requires=</varname>. A unit
 509                                 listed in this option will be started
 510                                 if the configuring unit is. However,
 511                                 if the listed unit fails to start up
 512                                 or cannot be added to the transaction
 513                                 this has no impact on the validity of
 514                                 the transaction as a whole. This is
 515                                 the recommended way to hook start-up
 516                                 of one unit to the start-up of another
 517                                 unit.</para>
 518
 519                                 <para>Note that dependencies of this
 520                                 type may also be configured outside of
 521                                 the unit configuration file by
 522                                 adding a symlink to a
 523                                 <filename>.wants/</filename> directory
 524                                 accompanying the unit file. For
 525                                 details see above.</para></listitem>
 526                         </varlistentry>
 527
 528                         <varlistentry>
 529                                 <term><varname>BindsTo=</varname></term>
 530
 531                                 <listitem><para>Configures requirement
 532                                 dependencies, very similar in style to
 533                                 <varname>Requires=</varname>, however
 534                                 in addition to this behavior it also
 535                                 declares that this unit is stopped
 536                                 when any of the units listed suddenly
 537                                 disappears. Units can suddenly,
 538                                 unexpectedly disappear if a service
 539                                 terminates on its own choice, a device
 540                                 is unplugged or a mount point
 541                                 unmounted without involvement of
 542                                 systemd.</para></listitem>
 543                         </varlistentry>
 544
 545                         <varlistentry>
 546                                 <term><varname>PartOf=</varname></term>
 547
 548                                 <listitem><para>Configures dependencies
 549                                 similar to <varname>Requires=</varname>,
 550                                 but limited to stopping and restarting
 551                                 of units. When systemd stops or restarts
 552                                 the units listed here, the action is
 553                                 propagated to this unit.
 554                                 Note that this is a one way dependency -
 555                                 changes to this unit do not affect the
 556                                 listed units.
 557                                 </para></listitem>
 558                         </varlistentry>
 559
 560                         <varlistentry>
 561                                 <term><varname>Conflicts=</varname></term>
 562
 563                                 <listitem><para>Configures negative
 564                                 requirement dependencies. If a unit
 565                                 has a
 566                                 <varname>Conflicts=</varname> setting
 567                                 on another unit, starting the former
 568                                 will stop the latter and vice
 569                                 versa. Note that this setting is
 570                                 independent of and orthogonal to the
 571                                 <varname>After=</varname> and
 572                                 <varname>Before=</varname> ordering
 573                                 dependencies.</para>
 574
 575                                 <para>If a unit A that conflicts with
 576                                 a unit B is scheduled to be started at
 577                                 the same time as B, the transaction
 578                                 will either fail (in case both are
 579                                 required part of the transaction) or
 580                                 be modified to be fixed (in case one
 581                                 or both jobs are not a required part
 582                                 of the transaction). In the latter
 583                                 case the job that is not the required
 584                                 will be removed, or in case both are
 585                                 not required the unit that conflicts
 586                                 will be started and the unit that is
 587                                 conflicted is
 588                                 stopped.</para></listitem>
 589                         </varlistentry>
 590
 591                         <varlistentry>
 592                                 <term><varname>Before=</varname></term>
 593                                 <term><varname>After=</varname></term>
 594
 595                                 <listitem><para>Configures ordering
 596                                 dependencies between units. If a unit
 597                                 <filename>foo.service</filename>
 598                                 contains a setting
 599                                 <option>Before=bar.service</option>
 600                                 and both units are being started,
 601                                 <filename>bar.service</filename>'s
 602                                 start-up is delayed until
 603                                 <filename>foo.service</filename> is
 604                                 started up. Note that this setting is
 605                                 independent of and orthogonal to the
 606                                 requirement dependencies as configured
 607                                 by <varname>Requires=</varname>. It is
 608                                 a common pattern to include a unit
 609                                 name in both the
 610                                 <varname>After=</varname> and
 611                                 <varname>Requires=</varname> option in
 612                                 which case the unit listed will be
 613                                 started before the unit that is
 614                                 configured with these options. This
 615                                 option may be specified more than
 616                                 once, in which case ordering
 617                                 dependencies for all listed names are
 618                                 created. <varname>After=</varname> is
 619                                 the inverse of
 620                                 <varname>Before=</varname>, i.e. while
 621                                 <varname>After=</varname> ensures that
 622                                 the configured unit is started after
 623                                 the listed unit finished starting up,
 624                                 <varname>Before=</varname> ensures the
 625                                 opposite, i.e.  that the configured
 626                                 unit is fully started up before the
 627                                 listed unit is started. Note that when
 628                                 two units with an ordering dependency
 629                                 between them are shut down, the
 630                                 inverse of the start-up order is
 631                                 applied. i.e. if a unit is configured
 632                                 with <varname>After=</varname> on
 633                                 another unit, the former is stopped
 634                                 before the latter if both are shut
 635                                 down. If one unit with an ordering
 636                                 dependency on another unit is shut
 637                                 down while the latter is started up,
 638                                 the shut down is ordered before the
 639                                 start-up regardless whether the
 640                                 ordering dependency is actually of
 641                                 type <varname>After=</varname> or
 642                                 <varname>Before=</varname>. If two
 643                                 units have no ordering dependencies
 644                                 between them they are shut down
 645                                 or started up simultaneously, and
 646                                 no ordering takes
 647                                 place. </para></listitem>
 648                         </varlistentry>
 649
 650                         <varlistentry>
 651                                 <term><varname>OnFailure=</varname></term>
 652
 653                                 <listitem><para>Lists one or more
 654                                 units that are activated when this
 655                                 unit enters the
 656                                 <literal>failed</literal>
 657                                 state.</para></listitem>
 658                         </varlistentry>
 659
 660                         <varlistentry>
 661                                 <term><varname>PropagatesReloadTo=</varname></term>
 662                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 663
 664                                 <listitem><para>Lists one or more
 665                                 units where reload requests on the
 666                                 unit will be propagated to/on the
 667                                 other unit will be propagated
 668                                 from. Issuing a reload request on a
 669                                 unit will automatically also enqueue a
 670                                 reload request on all units that the
 671                                 reload request shall be propagated to
 672                                 via these two
 673                                 settings.</para></listitem>
 674                         </varlistentry>
 675
 676                         <varlistentry>
 677                                 <term><varname>RequiresMountsFor=</varname></term>
 678
 679                                 <listitem><para>Takes a space-separated
 680                                 list of absolute paths. Automatically
 681                                 adds dependencies of type
 682                                 <varname>Requires=</varname> and
 683                                 <varname>After=</varname> for all
 684                                 mount units required to access the
 685                                 specified path.</para></listitem>
 686                         </varlistentry>
 687
 688                         <varlistentry>
 689                                 <term><varname>OnFailureIsolate=</varname></term>
 690
 691                                 <listitem><para>Takes a boolean
 692                                 argument. If <option>true</option> the
 693                                 unit listed in
 694                                 <varname>OnFailure=</varname> will be
 695                                 enqueued in isolation mode, i.e. all
 696                                 units that are not its dependency will
 697                                 be stopped. If this is set only a
 698                                 single unit may be listed in
 699                                 <varname>OnFailure=</varname>. Defaults
 700                                 to
 701                                 <option>false</option>.</para></listitem>
 702                         </varlistentry>
 703
 704                         <varlistentry>
 705                                 <term><varname>IgnoreOnIsolate=</varname></term>
 706
 707                                 <listitem><para>Takes a boolean
 708                                 argument. If <option>true</option>
 709                                 this unit will not be stopped when
 710                                 isolating another unit. Defaults to
 711                                 <option>false</option>.</para></listitem>
 712                         </varlistentry>
 713
 714                         <varlistentry>
 715                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 716
 717                                 <listitem><para>Takes a boolean
 718                                 argument. If <option>true</option>
 719                                 this unit will not be included in
 720                                 snapshots. Defaults to
 721                                 <option>true</option> for device and
 722                                 snapshot units, <option>false</option>
 723                                 for the others.</para></listitem>
 724                         </varlistentry>
 725
 726                         <varlistentry>
 727                                 <term><varname>StopWhenUnneeded=</varname></term>
 728
 729                                 <listitem><para>Takes a boolean
 730                                 argument. If <option>true</option>
 731                                 this unit will be stopped when it is
 732                                 no longer used. Note that in order to
 733                                 minimize the work to be executed,
 734                                 systemd will not stop units by default
 735                                 unless they are conflicting with other
 736                                 units, or the user explicitly
 737                                 requested their shut down. If this
 738                                 option is set, a unit will be
 739                                 automatically cleaned up if no other
 740                                 active unit requires it. Defaults to
 741                                 <option>false</option>.</para></listitem>
 742                         </varlistentry>
 743
 744                         <varlistentry>
 745                                 <term><varname>RefuseManualStart=</varname></term>
 746                                 <term><varname>RefuseManualStop=</varname></term>
 747
 748                                 <listitem><para>Takes a boolean
 749                                 argument. If <option>true</option>
 750                                 this unit can only be activated
 751                                 or deactivated indirectly. In
 752                                 this case explicit start-up
 753                                 or termination requested by the
 754                                 user is denied, however if it is
 755                                 started or stopped as a
 756                                 dependency of another unit, start-up
 757                                 or termination will succeed. This
 758                                 is mostly a safety feature to ensure
 759                                 that the user does not accidentally
 760                                 activate units that are not intended
 761                                 to be activated explicitly, and not
 762                                 accidentally deactivate units that are
 763                                 not intended to be deactivated.
 764                                 These options default to
 765                                 <option>false</option>.</para></listitem>
 766                         </varlistentry>
 767
 768                         <varlistentry>
 769                                 <term><varname>AllowIsolate=</varname></term>
 770
 771                                 <listitem><para>Takes a boolean
 772                                 argument. If <option>true</option>
 773                                 this unit may be used with the
 774                                 <command>systemctl isolate</command>
 775                                 command. Otherwise this will be
 776                                 refused. It probably is a good idea to
 777                                 leave this disabled except for target
 778                                 units that shall be used similar to
 779                                 runlevels in SysV init systems, just
 780                                 as a precaution to avoid unusable
 781                                 system states. This option defaults to
 782                                 <option>false</option>.</para></listitem>
 783                         </varlistentry>
 784
 785                         <varlistentry>
 786                                 <term><varname>DefaultDependencies=</varname></term>
 787
 788                                 <listitem><para>Takes a boolean
 789                                 argument. If <option>true</option>
 790                                 (the default), a few default
 791                                 dependencies will implicitly be
 792                                 created for the unit. The actual
 793                                 dependencies created depend on the
 794                                 unit type. For example, for service
 795                                 units, these dependencies ensure that
 796                                 the service is started only after
 797                                 basic system initialization is
 798                                 completed and is properly terminated on
 799                                 system shutdown. See the respective
 800                                 man pages for details. Generally, only
 801                                 services involved with early boot or
 802                                 late shutdown should set this option
 803                                 to <option>false</option>. It is
 804                                 highly recommended to leave this
 805                                 option enabled for the majority of
 806                                 common units. If set to
 807                                 <option>false</option>, this option
 808                                 does not disable all implicit
 809                                 dependencies, just non-essential
 810                                 ones.</para></listitem>
 811                         </varlistentry>
 812
 813                         <varlistentry>
 814                                 <term><varname>JobTimeoutSec=</varname></term>
 815
 816                                 <listitem><para>When clients are
 817                                 waiting for a job of this unit to
 818                                 complete, time out after the specified
 819                                 time. If this time limit is reached
 820                                 the job will be cancelled, the unit
 821                                 however will not change state or even
 822                                 enter the <literal>failed</literal>
 823                                 mode. This value defaults to 0 (job
 824                                 timeouts disabled), except for device
 825                                 units. NB: this timeout is independent
 826                                 from any unit-specific timeout (for
 827                                 example, the timeout set with
 828                                 <varname>Timeout=</varname> in service
 829                                 units) as the job timeout has no
 830                                 effect on the unit itself, only on the
 831                                 job that might be pending for it. Or
 832                                 in other words: unit-specific timeouts
 833                                 are useful to abort unit state
 834                                 changes, and revert them. The job
 835                                 timeout set with this option however
 836                                 is useful to abort only the job
 837                                 waiting for the unit state to
 838                                 change.</para></listitem>
 839                         </varlistentry>
 840
 841                         <varlistentry>
 842                                 <term><varname>ConditionPathExists=</varname></term>
 843                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 844                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 845                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 846                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 847                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 848                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 849                                 <term><varname>ConditionFileNotEmpty=</varname></term>
 850                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 851                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 852                                 <term><varname>ConditionVirtualization=</varname></term>
 853                                 <term><varname>ConditionSecurity=</varname></term>
 854                                 <term><varname>ConditionCapability=</varname></term>
 855                                 <term><varname>ConditionHost=</varname></term>
 856                                 <term><varname>ConditionACPower=</varname></term>
 857                                 <term><varname>ConditionNull=</varname></term>
 858
 859                                 <listitem><para>Before starting a unit
 860                                 verify that the specified condition is
 861                                 true. If it is not true the starting
 862                                 of the unit will be skipped, however
 863                                 all ordering dependencies of it are
 864                                 still respected. A failing condition
 865                                 will not result in the unit being
 866                                 moved into a failure state. The
 867                                 condition is checked at the time the
 868                                 queued start job is to be
 869                                 executed.</para>
 870
 871                                 <para>With
 872                                 <varname>ConditionPathExists=</varname>
 873                                 a file existence condition is
 874                                 checked before a unit is started. If
 875                                 the specified absolute path name does
 876                                 not exist the condition will
 877                                 fail. If the absolute path name passed
 878                                 to
 879                                 <varname>ConditionPathExists=</varname>
 880                                 is prefixed with an exclamation mark
 881                                 (<literal>!</literal>), the test is negated, and the unit
 882                                 is only started if the path does not
 883                                 exist.</para>
 884
 885                                 <para><varname>ConditionPathExistsGlob=</varname>
 886                                 is similar to
 887                                 <varname>ConditionPathExists=</varname>,
 888                                 but checks for the existence of at
 889                                 least one file or directory matching
 890                                 the specified globbing pattern.</para>
 891
 892                                 <para><varname>ConditionPathIsDirectory=</varname>
 893                                 is similar to
 894                                 <varname>ConditionPathExists=</varname>
 895                                 but verifies whether a certain path
 896                                 exists and is a
 897                                 directory.</para>
 898
 899                                 <para><varname>ConditionPathIsSymbolicLink=</varname>
 900                                 is similar to
 901                                 <varname>ConditionPathExists=</varname>
 902                                 but verifies whether a certain path
 903                                 exists and is a symbolic
 904                                 link.</para>
 905
 906                                 <para><varname>ConditionPathIsMountPoint=</varname>
 907                                 is similar to
 908                                 <varname>ConditionPathExists=</varname>
 909                                 but verifies whether a certain path
 910                                 exists and is a mount
 911                                 point.</para>
 912
 913                                 <para><varname>ConditionPathIsReadWrite=</varname>
 914                                 is similar to
 915                                 <varname>ConditionPathExists=</varname>
 916                                 but verifies whether the underlying
 917                                 file system is readable and writable
 918                                 (i.e. not mounted
 919                                 read-only).</para>
 920
 921                                 <para><varname>ConditionDirectoryNotEmpty=</varname>
 922                                 is similar to
 923                                 <varname>ConditionPathExists=</varname>
 924                                 but verifies whether a certain path
 925                                 exists and is a non-empty
 926                                 directory.</para>
 927
 928                                 <para><varname>ConditionFileNotEmpty=</varname>
 929                                 is similar to
 930                                 <varname>ConditionPathExists=</varname>
 931                                 but verifies whether a certain path
 932                                 exists and refers to a regular file
 933                                 with a non-zero size.</para>
 934
 935                                 <para><varname>ConditionFileIsExecutable=</varname>
 936                                 is similar to
 937                                 <varname>ConditionPathExists=</varname>
 938                                 but verifies whether a certain path
 939                                 exists, is a regular file and marked
 940                                 executable.</para>
 941
 942                                 <para>Similar,
 943                                 <varname>ConditionKernelCommandLine=</varname>
 944                                 may be used to check whether a
 945                                 specific kernel command line option is
 946                                 set (or if prefixed with the
 947                                 exclamation mark unset). The argument
 948                                 must either be a single word, or an
 949                                 assignment (i.e. two words, separated
 950                                 <literal>=</literal>). In the former
 951                                 case the kernel command line is
 952                                 searched for the word appearing as is,
 953                                 or as left hand side of an
 954                                 assignment. In the latter case the
 955                                 exact assignment is looked for with
 956                                 right and left hand side
 957                                 matching.</para>
 958
 959                                 <para><varname>ConditionVirtualization=</varname>
 960                                 may be used to check whether the
 961                                 system is executed in a virtualized
 962                                 environment and optionally test
 963                                 whether it is a specific
 964                                 implementation. Takes either boolean
 965                                 value to check if being executed in
 966                                 any virtualized environment, or one of
 967                                 <varname>vm</varname> and
 968                                 <varname>container</varname> to test
 969                                 against a generic type of
 970                                 virtualization solution, or one of
 971                                 <varname>qemu</varname>,
 972                                 <varname>kvm</varname>,
 973                                 <varname>vmware</varname>,
 974                                 <varname>microsoft</varname>,
 975                                 <varname>oracle</varname>,
 976                                 <varname>xen</varname>,
 977                                 <varname>bochs</varname>,
 978                                 <varname>chroot</varname>,
 979                                 <varname>uml</varname>,
 980                                 <varname>openvz</varname>,
 981                                 <varname>lxc</varname>,
 982                                 <varname>lxc-libvirt</varname>,
 983                                 <varname>systemd-nspawn</varname> to
 984                                 test against a specific
 985                                 implementation. If multiple
 986                                 virtualization technologies are nested
 987                                 only the innermost is considered. The
 988                                 test may be negated by prepending an
 989                                 exclamation mark.</para>
 990
 991                                 <para><varname>ConditionSecurity=</varname>
 992                                 may be used to check whether the given
 993                                 security module is enabled on the
 994                                 system. Currently the recognized values
 995                                 values are <varname>selinux</varname>,
 996                                 <varname>apparmor</varname>,
 997                                 <varname>ima</varname> and
 998                                 <varname>smack</varname>.
 999                                 The test may be negated by prepending
1000                                 an exclamation
1001                                 mark.</para>
1002
1003                                 <para><varname>ConditionCapability=</varname>
1004                                 may be used to check whether the given
1005                                 capability exists in the capability
1006                                 bounding set of the service manager
1007                                 (i.e. this does not check whether
1008                                 capability is actually available in
1009                                 the permitted or effective sets, see
1010                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1011                                 for details). Pass a capability name
1012                                 such as <literal>CAP_MKNOD</literal>,
1013                                 possibly prefixed with an exclamation
1014                                 mark to negate the check.</para>
1015
1016                                 <para><varname>ConditionHost=</varname>
1017                                 may be used to match against the
1018                                 hostname or machine ID of the
1019                                 host. This either takes a hostname
1020                                 string (optionally with shell style
1021                                 globs) which is tested against the
1022                                 locally set hostname as returned by
1023                                 <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
1024                                 or a machine ID formatted as string
1025                                 (see
1026                                 <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
1027                                 The test may be negated by prepending
1028                                 an exclamation mark.</para>
1029
1030                                 <para><varname>ConditionACPower=</varname>
1031                                 may be used to check whether the
1032                                 system has AC power, or is exclusively
1033                                 battery powered at the time of
1034                                 activation of the unit. This takes a
1035                                 boolean argument. If set to
1036                                 <varname>true</varname> the condition
1037                                 will hold only if at least one AC
1038                                 connector of the system is connected
1039                                 to a power source, or if no AC
1040                                 connectors are known. Conversely, if
1041                                 set to <varname>false</varname> the
1042                                 condition will hold only if there is
1043                                 at least one AC connector known and
1044                                 all AC connectors are disconnected
1045                                 from a power source.</para>
1046
1047                                 <para>Finally,
1048                                 <varname>ConditionNull=</varname> may
1049                                 be used to add a constant condition
1050                                 check value to the unit. It takes a
1051                                 boolean argument. If set to
1052                                 <varname>false</varname> the condition
1053                                 will always fail, otherwise
1054                                 succeed.</para>
1055
1056                                 <para>If multiple conditions are
1057                                 specified the unit will be executed if
1058                                 all of them apply (i.e. a logical AND
1059                                 is applied). Condition checks can be
1060                                 prefixed with a pipe symbol (|) in
1061                                 which case a condition becomes a
1062                                 triggering condition. If at least one
1063                                 triggering condition is defined for a
1064                                 unit then the unit will be executed if
1065                                 at least one of the triggering
1066                                 conditions apply and all of the
1067                                 non-triggering conditions. If you
1068                                 prefix an argument with the pipe
1069                                 symbol and an exclamation mark the
1070                                 pipe symbol must be passed first, the
1071                                 exclamation second. Except for
1072                                 <varname>ConditionPathIsSymbolicLink=</varname>,
1073                                 all path checks follow symlinks. If
1074                                 any of these options is assigned the
1075                                 empty string the list of conditions is
1076                                 reset completely, all previous
1077                                 condition settings (of any kind) will
1078                                 have no effect.</para></listitem>
1079                         </varlistentry>
1080
1081                         <varlistentry>
1082                                 <term><varname>SourcePath=</varname></term>
1083                                 <listitem><para>A path to a
1084                                 configuration file this unit has been
1085                                 generated from. This is primarily
1086                                 useful for implementation of generator
1087                                 tools that convert configuration from
1088                                 an external configuration file format
1089                                 into native unit files. Thus
1090                                 functionality should not be used in
1091                                 normal units.</para></listitem>
1092                         </varlistentry>
1093                 </variablelist>
1094
1095                 <para>Unit file may include a [Install] section, which
1096                 carries installation information for the unit. This
1097                 section is not interpreted by
1098                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1099                 during runtime. It is used exclusively by the
1100                 <command>enable</command> and
1101                 <command>disable</command> commands of the
1102                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1103                 tool during installation of a unit:</para>
1104
1105                 <variablelist class='unit-directives'>
1106                         <varlistentry>
1107                                 <term><varname>Alias=</varname></term>
1108
1109                                 <listitem><para>Additional names this
1110                                 unit shall be installed under. The
1111                                 names listed here must have the same
1112                                 suffix (i.e. type) as the unit file
1113                                 name. This option may be specified
1114                                 more than once, in which case all
1115                                 listed names are used. At installation
1116                                 time,
1117                                 <command>systemctl enable</command>
1118                                 will create symlinks from these names
1119                                 to the unit filename.</para></listitem>
1120                         </varlistentry>
1121
1122                         <varlistentry>
1123                                 <term><varname>WantedBy=</varname></term>
1124                                 <term><varname>RequiredBy=</varname></term>
1125
1126                                 <listitem><para>A symbolic link is
1127                                 created in the
1128                                 <filename>.wants/</filename> or
1129                                 <filename>.requires/</filename> directory
1130                                 of the listed unit when this unit is
1131                                 activated by <command>systemctl
1132                                 enable</command>.  This has the effect
1133                                 that a dependency of type
1134                                 <varname>Wants=</varname> or
1135                                 <varname>Requires=</varname> is added
1136                                 from the listed unit to the current
1137                                 unit. The primary result is that the
1138                                 current unit will be started when the
1139                                 listed unit is started. See the
1140                                 description of
1141                                 <varname>Wants=</varname> and
1142                                 <varname>Requires=</varname> in the
1143                                 [Unit] section for details.</para>
1144
1145                                 <para><command>WantedBy=foo.service</command>
1146                                 in a service
1147                                 <filename>bar.service</filename> is
1148                                 mostly equivalent to
1149                                 <command>Alias=foo.service.wants/bar.service</command>
1150                                 in the same file. In case of template
1151                                 units, <command>systemctl enable</command>
1152                                 must be called with an instance name, and
1153                                 this instance will be added to the
1154                                 <filename>.wants/</filename> or
1155                                 <filename>.requires/</filename> list
1156                                 of the listed unit.
1157                                 E.g. <command>WantedBy=getty.target</command>
1158                                 in a service
1159                                 <filename>getty@.service</filename>
1160                                 will result in <command>systemctl
1161                                 enable getty@tty2.service</command>
1162                                 creating a
1163                                 <filename>getty.target.wants/getty@tty2.service</filename>
1164                                 link to <filename>getty@.service</filename>.
1165                                 </para></listitem>
1166                         </varlistentry>
1167
1168                         <varlistentry>
1169                                 <term><varname>Also=</varname></term>
1170
1171                                 <listitem><para>Additional units to
1172                                 install/deinstall when this unit is
1173                                 installed/deinstalled. If the user
1174                                 requests installation/deinstallation
1175                                 of a unit with this option configured,
1176                                 <command>systemctl enable</command>
1177                                 and <command>systemctl
1178                                 disable</command> will automatically
1179                                 install/uninstall units listed in this option as
1180                                 well.</para></listitem>
1181                         </varlistentry>
1182                 </variablelist>
1183
1184                 <para>The following specifiers are interpreted in the
1185                 Install section: %n, %N, %p, %i, %U, %u, %m, %H, %b, %v.
1186                 For their meaning see the next section.
1187                 </para>
1188         </refsect1>
1189
1190         <refsect1>
1191                 <title>Specifiers</title>
1192
1193                 <para>Many settings resolve specifiers which may be
1194                 used to write generic unit files referring to runtime
1195                 or unit parameters that are replaced when the unit
1196                 files are loaded. The following specifiers are
1197                 understood:</para>
1198
1199                 <table>
1200                   <title>Specifiers available in unit files</title>
1201                   <tgroup cols='3' align='left' colsep='1' rowsep='1'>
1202                     <colspec colname="spec" />
1203                     <colspec colname="mean" />
1204                     <colspec colname="detail" />
1205                     <thead>
1206                       <row>
1207                         <entry>Specifier</entry>
1208                         <entry>Meaning</entry>
1209                         <entry>Details</entry>
1210                       </row>
1211                     </thead>
1212                     <tbody>
1213                       <row>
1214                         <entry><literal>%n</literal></entry>
1215                         <entry>Full unit name</entry>
1216                         <entry></entry>
1217                       </row>
1218                       <row>
1219                         <entry><literal>%N</literal></entry>
1220                         <entry>Unescaped full unit name</entry>
1221                         <entry></entry>
1222                       </row>
1223                       <row>
1224                         <entry><literal>%p</literal></entry>
1225                         <entry>Prefix name</entry>
1226                         <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>
1227                       </row>
1228                       <row>
1229                         <entry><literal>%P</literal></entry>
1230                         <entry>Unescaped prefix name</entry>
1231                         <entry></entry>
1232                       </row>
1233                       <row>
1234                         <entry><literal>%i</literal></entry>
1235                         <entry>Instance name</entry>
1236                         <entry>For instantiated units: this is the string between the <literal>@</literal> character and the suffix.</entry>
1237                       </row>
1238                       <row>
1239                         <entry><literal>%I</literal></entry>
1240                         <entry>Unescaped instance name</entry>
1241                         <entry></entry>
1242                       </row>
1243                       <row>
1244                         <entry><literal>%f</literal></entry>
1245                         <entry>Unescaped filename</entry>
1246                         <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>
1247                       </row>
1248                       <row>
1249                         <entry><literal>%c</literal></entry>
1250                         <entry>Control group path of the unit</entry>
1251                         <entry></entry>
1252                       </row>
1253                       <row>
1254                         <entry><literal>%r</literal></entry>
1255                         <entry>Root control group path where units are placed.</entry>
1256                         <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>
1257                       </row>
1258                       <row>
1259                         <entry><literal>%R</literal></entry>
1260                         <entry>Parent directory of the control group path where units are placed.</entry>
1261                         <entry>For system instances this usually resolves to <filename>/</filename>, except in containers, where this resolves to the container's root directory. This specifier is particularly useful in the <varname>ControlGroup=</varname> setting (see <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</entry>
1262                       </row>
1263                       <row>
1264                         <entry><literal>%t</literal></entry>
1265                         <entry>Runtime socket dir</entry>
1266                         <entry>This is either <filename>/run</filename> (for the system manager) or <literal>$XDG_RUNTIME_DIR</literal> (for user managers).</entry>
1267                       </row>
1268                       <row>
1269                         <entry><literal>%u</literal></entry>
1270                         <entry>User name</entry>
1271                         <entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1272                       </row>
1273                       <row>
1274                         <entry><literal>%U</literal></entry>
1275                         <entry>User UID</entry>
1276                         <entry>This is the UID of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1277                       </row>
1278                       <row>
1279                         <entry><literal>%h</literal></entry>
1280                         <entry>User home directory</entry>
1281                         <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>
1282                       </row>
1283                       <row>
1284                         <entry><literal>%s</literal></entry>
1285                         <entry>User shell</entry>
1286                         <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>
1287                       </row>
1288                       <row>
1289                         <entry><literal>%m</literal></entry>
1290                         <entry>Machine ID</entry>
1291                         <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>
1292                       </row>
1293                       <row>
1294                         <entry><literal>%b</literal></entry>
1295                         <entry>Boot ID</entry>
1296                         <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
1297                       </row>
1298                       <row>
1299                         <entry><literal>%H</literal></entry>
1300                         <entry>Host name</entry>
1301                         <entry>The hostname of the running system.</entry>
1302                       </row>
1303                       <row>
1304                         <entry><literal>%v</literal></entry>
1305                         <entry>Kernel release</entry>
1306                         <entry>Identical to <command>uname -r</command> output.</entry>
1307                       </row>
1308                       <row>
1309                         <entry><literal>%%</literal></entry>
1310                         <entry>Escaped %</entry>
1311                         <entry>Single percent sign.</entry>
1312                       </row>
1313                     </tbody>
1314                   </tgroup>
1315                 </table>
1316         </refsect1>
1317
1318         <refsect1>
1319                 <title>See Also</title>
1320                 <para>
1321                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1322                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1323                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1324                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1325                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1326                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1327                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1328                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1329                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1330                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1331                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1332                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1333                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1334                         <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1335                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1336                         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1337                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1338                         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1339                         <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1340                 </para>
1341         </refsect1>
1342
1343 </refentry>