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></para>
  64
  65                 <para><literallayout><filename>/etc/systemd/system/*</filename>
  66 <filename>/run/systemd/system/*</filename>
  67 <filename>/usr/lib/systemd/system/*</filename>
  68 <filename>...</filename>
  69                 </literallayout></para>
  70
  71                 <para><literallayout><filename>/etc/systemd/user/*</filename>
  72 <filename>/run/systemd/user/*</filename>
  73 <filename>/usr/lib/systemd/user/*</filename>
  74 <filename>...</filename>
  75                 </literallayout></para>
  76         </refsynopsisdiv>
  77
  78         <refsect1>
  79                 <title>Description</title>
  80
  81                 <para>A unit configuration file encodes information
  82                 about a service, a socket, a device, a mount point, an
  83                 automount point, a swap file or partition, a start-up
  84                 target, a file system path, or a timer controlled and
  85                 supervised by
  86                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>. The
  87                 syntax is inspired by <ulink
  88                 url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
  89                 Desktop Entry Specification</ulink> <filename>.desktop</filename> files, which are in turn
  90                 inspired by Microsoft Windows
  91                 <filename>.ini</filename> files.</para>
  92
  93                 <para>This man page lists the common configuration
  94                 options of all the unit types. These options need to
  95                 be configured in the [Unit] or [Install]
  96                 sections of the unit files.</para>
  97
  98                 <para>In addition to the generic [Unit] and [Install]
  99                 sections described here, each unit may have a
 100                 type-specific section, e.g. [Service] for a service
 101                 unit. See the respective man pages for more
 102                 information:
 103                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 104                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 105                 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 106                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 107                 <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 108                 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 109                 <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 110                 <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 111                 <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 112                 <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 113                 </para>
 114
 115                 <para>Unit files are loaded from a set of paths
 116                 determined during compilation, described in the next section.
 117                 </para>
 118
 119                 <para>Unit files may contain additional options on top
 120                 of those listed here. If systemd encounters an unknown
 121                 option it will write a warning log message but
 122                 continue loading the unit. If an option is prefixed
 123                 with <option>X-</option> it is ignored completely by
 124                 systemd. Applications may use this to include
 125                 additional information in the unit files.</para>
 126
 127                 <para>Boolean arguments used in unit files can be
 128                 written in various formats. For positive settings the
 129                 strings <option>1</option>, <option>yes</option>,
 130                 <option>true</option> and <option>on</option> are
 131                 equivalent. For negative settings the strings
 132                 <option>0</option>, <option>no</option>,
 133                 <option>false</option> and <option>off</option> are
 134                 equivalent.</para>
 135
 136                 <para>Time span values encoded in unit files can be
 137                 written in various formats. A stand-alone number
 138                 specifies a time in seconds. If suffixed with a time
 139                 unit, the unit is honored. A concatenation of multiple
 140                 values with units is supported, in which case the
 141                 values are added up. Example: "50" refers to 50
 142                 seconds; "2min 200ms" refers to 2 minutes plus 200
 143                 milliseconds, i.e. 120200ms. The following time units
 144                 are understood: s, min, h, d, w, ms, us. For details
 145                 see
 146                 <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 147
 148                 <para>Empty lines and lines starting with # or ; are
 149                 ignored. This may be used for commenting. Lines ending
 150                 in a backslash are concatenated with the following
 151                 line while reading and the backslash is replaced by a
 152                 space character. This may be used to wrap long lines.</para>
 153
 154                 <para>Along with a unit file
 155                 <filename>foo.service</filename> the directory
 156                 <filename>foo.service.wants/</filename> may exist. All
 157                 unit files symlinked from such a directory are
 158                 implicitly added as dependencies of type
 159                 <varname>Wanted=</varname> to the unit. This is useful
 160                 to hook units into the start-up of other units,
 161                 without having to modify their unit files. For details
 162                 about the semantics of <varname>Wanted=</varname> see
 163                 below. The preferred way to create symlinks in the
 164                 <filename>.wants/</filename> directory of a unit file
 165                 is with the <command>enable</command> command of the
 166                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 167                 tool which reads information from the [Install]
 168                 section of unit files (see below). A similar
 169                 functionality exists for <varname>Requires=</varname>
 170                 type dependencies as well, the directory suffix is
 171                 <filename>.requires/</filename> in this case.</para>
 172
 173                 <para>Along with a unit file
 174                 <filename>foo.service</filename> a directory
 175                 <filename>foo.service.d/</filename> may exist. All
 176                 files with the suffix <filename>.conf</filename> from
 177                 this directory will be parsed after the file itself is
 178                 parsed. This is useful to alter or add configuration
 179                 settings to a unit, without having to modify their
 180                 unit files. Make sure that the file that is included
 181                 has the appropriate section headers before any
 182                 directive.</para>
 183
 184                 <para>If a line starts with <option>.include</option>
 185                 followed by a filename, the specified file will be
 186                 parsed at this point. Make sure that the file that is
 187                 included has the appropriate section headers before
 188                 any directives.</para>
 189
 190                 <para>Note that while systemd offers a flexible
 191                 dependency system between units it is recommended to
 192                 use this functionality only sparingly and instead rely
 193                 on techniques such as bus-based or socket-based
 194                 activation which make dependencies implicit, resulting
 195                 in a both simpler and more flexible system.</para>
 196
 197                 <para>Some unit names reflect paths existing in the
 198                 file system namespace. Example: a device unit
 199                 <filename>dev-sda.device</filename> refers to a device
 200                 with the device node <filename noindex='true'>/dev/sda</filename> in
 201                 the file system namespace. If this applies a special
 202                 way to escape the path name is used, so that the
 203                 result is usable as part of a filename. Basically,
 204                 given a path, "/" is replaced by "-", and all
 205                 unprintable characters and the "-" are replaced by
 206                 C-style "\x20" escapes. The root directory "/" is
 207                 encoded as single dash, while otherwise the initial
 208                 and ending "/" is removed from all paths during
 209                 transformation. This escaping is reversible.</para>
 210
 211                 <para>Optionally, units may be instantiated from a
 212                 template file at runtime. This allows creation of
 213                 multiple units from a single configuration file. If
 214                 systemd looks for a unit configuration file it will
 215                 first search for the literal unit name in the
 216                 filesystem. If that yields no success and the unit
 217                 name contains an <literal>@</literal> character, systemd will look for a
 218                 unit template that shares the same name but with the
 219                 instance string (i.e. the part between the <literal>@</literal> character
 220                 and the suffix) removed. Example: if a service
 221                 <filename>getty@tty3.service</filename> is requested
 222                 and no file by that name is found, systemd will look
 223                 for <filename>getty@.service</filename> and
 224                 instantiate a service from that configuration file if
 225                 it is found.</para>
 226
 227                 <para>To refer to the instance string from
 228                 within the configuration file you may use the special
 229                 <literal>%i</literal> specifier in many of the
 230                 configuration options. See below for details.</para>
 231
 232                 <para>If a unit file is empty (i.e. has the file size
 233                 0) or is symlinked to <filename>/dev/null</filename>
 234                 its configuration will not be loaded and it appears
 235                 with a load state of <literal>masked</literal>, and
 236                 cannot be activated. Use this as an effective way to
 237                 fully disable a unit, making it impossible to start it
 238                 even manually.</para>
 239
 240                 <para>The unit file format is covered by the
 241                 <ulink
 242                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 243                 Stability Promise</ulink>.</para>
 244
 245         </refsect1>
 246
 247         <refsect1>
 248                 <title>Unit Load Path</title>
 249
 250                 <para>Unit files are loaded from a set of paths
 251                 determined during compilation, described in the two
 252                 tables below. Unit files found in directories higher
 253                 in the hierarchy override files with the same name
 254                 lower in the hierarchy, thus allowing overrides.
 255                 </para>
 256
 257                 <para>When systemd is running in user mode
 258                 (<option>--user</option>) and the variable
 259                 <varname>$SYSTEMD_UNIT_PATH</varname> is set, this
 260                 contents of this variable overrides the unit load
 261                 path.
 262                 </para>
 263
 264                 <table>
 265                   <title>
 266                     Load path when running in system mode (<option>--system</option>).
 267                   </title>
 268
 269                   <tgroup cols='2'>
 270                     <colspec colname='path' />
 271                     <colspec colname='expl' />
 272                     <thead>
 273                       <row>
 274                         <entry>Path</entry>
 275                         <entry>Description</entry>
 276                       </row>
 277                     </thead>
 278                     <tbody>
 279                       <row>
 280                         <entry><filename>/run/systemd/generator.early</filename></entry>
 281                         <entry>Generated units (early)</entry>
 282                       </row>
 283                       <row>
 284                         <entry><filename>/etc/systemd/system</filename></entry>
 285                         <entry>Local configuration</entry>
 286                       </row>
 287                       <row>
 288                         <entry><filename>/run/systemd/systemd</filename></entry>
 289                         <entry>Volatile units</entry>
 290                       </row>
 291                       <row>
 292                         <entry><filename>/run/systemd/generator</filename></entry>
 293                         <entry>Generated units (middle)</entry>
 294                       </row>
 295                       <row>
 296                         <entry><filename>/usr/local/lib/systemd/system</filename></entry>
 297                         <entry>Units for local packages</entry>
 298                       </row>
 299                       <row>
 300                         <entry><filename>/usr/lib/systemd/system</filename></entry>
 301                         <entry>Units for installed packages</entry>
 302                       </row>
 303                       <row>
 304                         <entry><filename>/run/systemd/generator.late</filename></entry>
 305                         <entry>Generated units (late)</entry>
 306                       </row>
 307                     </tbody>
 308                   </tgroup>
 309                 </table>
 310
 311                 <table>
 312                   <title>
 313                     Load path when running in session mode (<option>--user</option>).
 314                   </title>
 315
 316                   <tgroup cols='2'>
 317                     <colspec colname='path' />
 318                     <colspec colname='expl' />
 319                     <thead>
 320                       <row>
 321                         <entry>Path</entry>
 322                         <entry>Description</entry>
 323                       </row>
 324                     </thead>
 325                     <tbody>
 326                       <row>
 327                         <entry><filename>/tmp/systemd-generator.early.<replaceable>XXXXXX</replaceable></filename></entry>
 328                         <entry>Generated units (early)</entry>
 329                       </row>
 330                       <row>
 331                         <entry><filename>/etc/systemd/user</filename></entry>
 332                         <entry>Local configuration</entry>
 333                       </row>
 334                       <row>
 335                         <entry><filename>/run/systemd/user</filename></entry>
 336                         <entry>Volatile units</entry>
 337                       </row>
 338                       <row>
 339                         <entry><filename>/tmp/systemd-generator.<replaceable>XXXXXX</replaceable></filename></entry>
 340                         <entry>Generated units (middle)</entry>
 341                       </row>
 342                       <row>
 343                         <entry><filename>/usr/local/lib/systemd/user</filename></entry>
 344                         <entry>Units for local packages</entry>
 345                       </row>
 346                       <row>
 347                         <entry><filename>/usr/lib/systemd/user</filename></entry>
 348                         <entry>Units for installed packages</entry>
 349                       </row>
 350                       <row>
 351                         <entry><filename>/tmp/systemd-generator.late.<replaceable>XXXXXX</replaceable></filename></entry>
 352                         <entry>Generated units (late)</entry>
 353                       </row>
 354                     </tbody>
 355                   </tgroup>
 356                 </table>
 357
 358                 <para>Additional units might be loaded into systemd
 359                 ("linked") from directories not on the unit load
 360                 path. See the <command>link</command> command for
 361                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 362                 </para>
 363         </refsect1>
 364
 365         <refsect1>
 366                 <title>Options</title>
 367
 368                 <para>Unit file may include a [Unit] section, which
 369                 carries generic information about the unit that is not
 370                 dependent on the type of unit:</para>
 371
 372                 <variablelist class='unit-directives'>
 373
 374                         <varlistentry>
 375                                 <term><varname>Description=</varname></term>
 376                                 <listitem><para>A free-form string
 377                                 describing the unit. This is intended
 378                                 for use in UIs to show descriptive
 379                                 information along with the unit
 380                                 name.</para></listitem>
 381                         </varlistentry>
 382
 383                         <varlistentry>
 384                                 <term><varname>Documentation=</varname></term>
 385                                 <listitem><para>A space-separated list
 386                                 of URIs referencing documentation for
 387                                 this unit or its
 388                                 configuration. Accepted are only URIs
 389                                 of the types
 390                                 <literal>http://</literal>,
 391                                 <literal>https://</literal>,
 392                                 <literal>file:</literal>,
 393                                 <literal>info:</literal>,
 394                                 <literal>man:</literal>. For more
 395                                 information about the syntax of these
 396                                 URIs, see
 397                                 <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
 398                                 URIs should be listed in order of
 399                                 relevance, starting with the most
 400                                 relevant. It is a good idea to first
 401                                 reference documentation that explains
 402                                 what the unit's purpose is, followed
 403                                 by how it is configured, followed by
 404                                 any other related documentation. This
 405                                 option may be specified more than once
 406                                 in which case the specified list of
 407                                 URIs is merged. If the empty string is
 408                                 assigned to this option, the list is
 409                                 reset and all prior assignments will
 410                                 have no effect.</para></listitem>
 411                         </varlistentry>
 412
 413                         <varlistentry>
 414                                 <term><varname>Requires=</varname></term>
 415
 416                                 <listitem><para>Configures requirement
 417                                 dependencies on other units. If this
 418                                 unit gets activated, the units listed
 419                                 here will be activated as well. If one
 420                                 of the other units gets deactivated or
 421                                 its activation fails, this unit will
 422                                 be deactivated. This option may be
 423                                 specified more than once, in which
 424                                 case requirement dependencies for all
 425                                 listed names are created. Note that
 426                                 requirement dependencies do not
 427                                 influence the order in which services
 428                                 are started or stopped. This has to be
 429                                 configured independently with the
 430                                 <varname>After=</varname> or
 431                                 <varname>Before=</varname> options. If
 432                                 a unit
 433                                 <filename>foo.service</filename>
 434                                 requires a unit
 435                                 <filename>bar.service</filename> as
 436                                 configured with
 437                                 <varname>Requires=</varname> and no
 438                                 ordering is configured with
 439                                 <varname>After=</varname> or
 440                                 <varname>Before=</varname>, then both
 441                                 units will be started simultaneously
 442                                 and without any delay between them if
 443                                 <filename>foo.service</filename> is
 444                                 activated. Often it is a better choice
 445                                 to use <varname>Wants=</varname>
 446                                 instead of
 447                                 <varname>Requires=</varname> in order
 448                                 to achieve a system that is more
 449                                 robust when dealing with failing
 450                                 services.</para>
 451
 452                                 <para>Note that dependencies of this
 453                                 type may also be configured outside of
 454                                 the unit configuration file by
 455                                 adding a symlink to a
 456                                 <filename>.requires/</filename> directory
 457                                 accompanying the unit file. For
 458                                 details see above.</para></listitem>
 459                         </varlistentry>
 460
 461                         <varlistentry>
 462                                 <term><varname>RequiresOverridable=</varname></term>
 463
 464                                 <listitem><para>Similar to
 465                                 <varname>Requires=</varname>.
 466                                 Dependencies listed in
 467                                 <varname>RequiresOverridable=</varname>
 468                                 which cannot be fulfilled or fail to
 469                                 start are ignored if the startup was
 470                                 explicitly requested by the user. If
 471                                 the start-up was pulled in indirectly
 472                                 by some dependency or automatic
 473                                 start-up of units that is not
 474                                 requested by the user this dependency
 475                                 must be fulfilled and otherwise the
 476                                 transaction fails. Hence, this option
 477                                 may be used to configure dependencies
 478                                 that are normally honored unless the
 479                                 user explicitly starts up the unit, in
 480                                 which case whether they failed or not
 481                                 is irrelevant.</para></listitem>
 482
 483                         </varlistentry>
 484                         <varlistentry>
 485                                 <term><varname>Requisite=</varname></term>
 486                                 <term><varname>RequisiteOverridable=</varname></term>
 487
 488                                 <listitem><para>Similar to
 489                                 <varname>Requires=</varname>
 490                                 and <varname>RequiresOverridable=</varname>, respectively. However,
 491                                 if a unit listed here is not started
 492                                 already it will not be started and the
 493                                 transaction fails
 494                                 immediately.</para></listitem>
 495                         </varlistentry>
 496
 497                         <varlistentry>
 498                                 <term><varname>Wants=</varname></term>
 499
 500                                 <listitem><para>A weaker version of
 501                                 <varname>Requires=</varname>. A unit
 502                                 listed in this option will be started
 503                                 if the configuring unit is. However,
 504                                 if the listed unit fails to start up
 505                                 or cannot be added to the transaction
 506                                 this has no impact on the validity of
 507                                 the transaction as a whole. This is
 508                                 the recommended way to hook start-up
 509                                 of one unit to the start-up of another
 510                                 unit.</para>
 511
 512                                 <para>Note that dependencies of this
 513                                 type may also be configured outside of
 514                                 the unit configuration file by
 515                                 adding a symlink to a
 516                                 <filename>.wants/</filename> directory
 517                                 accompanying the unit file. For
 518                                 details see above.</para></listitem>
 519                         </varlistentry>
 520
 521                         <varlistentry>
 522                                 <term><varname>BindsTo=</varname></term>
 523
 524                                 <listitem><para>Configures requirement
 525                                 dependencies, very similar in style to
 526                                 <varname>Requires=</varname>, however
 527                                 in addition to this behavior it also
 528                                 declares that this unit is stopped
 529                                 when any of the units listed suddenly
 530                                 disappears. Units can suddenly,
 531                                 unexpectedly disappear if a service
 532                                 terminates on its own choice, a device
 533                                 is unplugged or a mount point
 534                                 unmounted without involvement of
 535                                 systemd.</para></listitem>
 536                         </varlistentry>
 537
 538                         <varlistentry>
 539                                 <term><varname>PartOf=</varname></term>
 540
 541                                 <listitem><para>Configures dependencies
 542                                 similar to <varname>Requires=</varname>,
 543                                 but limited to stopping and restarting
 544                                 of units. When systemd stops or restarts
 545                                 the units listed here, the action is
 546                                 propagated to this unit.
 547                                 Note that this is a one way dependency -
 548                                 changes to this unit do not affect the
 549                                 listed units.
 550                                 </para></listitem>
 551                         </varlistentry>
 552
 553                         <varlistentry>
 554                                 <term><varname>Conflicts=</varname></term>
 555
 556                                 <listitem><para>Configures negative
 557                                 requirement dependencies. If a unit
 558                                 has a
 559                                 <varname>Conflicts=</varname> setting
 560                                 on another unit, starting the former
 561                                 will stop the latter and vice
 562                                 versa. Note that this setting is
 563                                 independent of and orthogonal to the
 564                                 <varname>After=</varname> and
 565                                 <varname>Before=</varname> ordering
 566                                 dependencies.</para>
 567
 568                                 <para>If a unit A that conflicts with
 569                                 a unit B is scheduled to be started at
 570                                 the same time as B, the transaction
 571                                 will either fail (in case both are
 572                                 required part of the transaction) or
 573                                 be modified to be fixed (in case one
 574                                 or both jobs are not a required part
 575                                 of the transaction). In the latter
 576                                 case the job that is not the required
 577                                 will be removed, or in case both are
 578                                 not required the unit that conflicts
 579                                 will be started and the unit that is
 580                                 conflicted is
 581                                 stopped.</para></listitem>
 582                         </varlistentry>
 583
 584                         <varlistentry>
 585                                 <term><varname>Before=</varname></term>
 586                                 <term><varname>After=</varname></term>
 587
 588                                 <listitem><para>Configures ordering
 589                                 dependencies between units. If a unit
 590                                 <filename>foo.service</filename>
 591                                 contains a setting
 592                                 <option>Before=bar.service</option>
 593                                 and both units are being started,
 594                                 <filename>bar.service</filename>'s
 595                                 start-up is delayed until
 596                                 <filename>foo.service</filename> is
 597                                 started up. Note that this setting is
 598                                 independent of and orthogonal to the
 599                                 requirement dependencies as configured
 600                                 by <varname>Requires=</varname>. It is
 601                                 a common pattern to include a unit
 602                                 name in both the
 603                                 <varname>After=</varname> and
 604                                 <varname>Requires=</varname> option in
 605                                 which case the unit listed will be
 606                                 started before the unit that is
 607                                 configured with these options. This
 608                                 option may be specified more than
 609                                 once, in which case ordering
 610                                 dependencies for all listed names are
 611                                 created. <varname>After=</varname> is
 612                                 the inverse of
 613                                 <varname>Before=</varname>, i.e. while
 614                                 <varname>After=</varname> ensures that
 615                                 the configured unit is started after
 616                                 the listed unit finished starting up,
 617                                 <varname>Before=</varname> ensures the
 618                                 opposite, i.e.  that the configured
 619                                 unit is fully started up before the
 620                                 listed unit is started. Note that when
 621                                 two units with an ordering dependency
 622                                 between them are shut down, the
 623                                 inverse of the start-up order is
 624                                 applied. i.e. if a unit is configured
 625                                 with <varname>After=</varname> on
 626                                 another unit, the former is stopped
 627                                 before the latter if both are shut
 628                                 down. If one unit with an ordering
 629                                 dependency on another unit is shut
 630                                 down while the latter is started up,
 631                                 the shut down is ordered before the
 632                                 start-up regardless whether the
 633                                 ordering dependency is actually of
 634                                 type <varname>After=</varname> or
 635                                 <varname>Before=</varname>. If two
 636                                 units have no ordering dependencies
 637                                 between them they are shut down
 638                                 or started up simultaneously, and
 639                                 no ordering takes
 640                                 place. </para></listitem>
 641                         </varlistentry>
 642
 643                         <varlistentry>
 644                                 <term><varname>OnFailure=</varname></term>
 645
 646                                 <listitem><para>Lists one or more
 647                                 units that are activated when this
 648                                 unit enters the
 649                                 <literal>failed</literal>
 650                                 state.</para></listitem>
 651                         </varlistentry>
 652
 653                         <varlistentry>
 654                                 <term><varname>PropagatesReloadTo=</varname></term>
 655                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 656
 657                                 <listitem><para>Lists one or more
 658                                 units where reload requests on the
 659                                 unit will be propagated to/on the
 660                                 other unit will be propagated
 661                                 from. Issuing a reload request on a
 662                                 unit will automatically also enqueue a
 663                                 reload request on all units that the
 664                                 reload request shall be propagated to
 665                                 via these two
 666                                 settings.</para></listitem>
 667                         </varlistentry>
 668
 669                         <varlistentry>
 670                                 <term><varname>RequiresMountsFor=</varname></term>
 671
 672                                 <listitem><para>Takes a space-separated
 673                                 list of absolute paths. Automatically
 674                                 adds dependencies of type
 675                                 <varname>Requires=</varname> and
 676                                 <varname>After=</varname> for all
 677                                 mount units required to access the
 678                                 specified path.</para></listitem>
 679                         </varlistentry>
 680
 681                         <varlistentry>
 682                                 <term><varname>OnFailureIsolate=</varname></term>
 683
 684                                 <listitem><para>Takes a boolean
 685                                 argument. If <option>true</option> the
 686                                 unit listed in
 687                                 <varname>OnFailure=</varname> will be
 688                                 enqueued in isolation mode, i.e. all
 689                                 units that are not its dependency will
 690                                 be stopped. If this is set only a
 691                                 single unit may be listed in
 692                                 <varname>OnFailure=</varname>. Defaults
 693                                 to
 694                                 <option>false</option>.</para></listitem>
 695                         </varlistentry>
 696
 697                         <varlistentry>
 698                                 <term><varname>IgnoreOnIsolate=</varname></term>
 699
 700                                 <listitem><para>Takes a boolean
 701                                 argument. If <option>true</option>
 702                                 this unit will not be stopped when
 703                                 isolating another unit. Defaults to
 704                                 <option>false</option>.</para></listitem>
 705                         </varlistentry>
 706
 707                         <varlistentry>
 708                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 709
 710                                 <listitem><para>Takes a boolean
 711                                 argument. If <option>true</option>
 712                                 this unit will not be included in
 713                                 snapshots. Defaults to
 714                                 <option>true</option> for device and
 715                                 snapshot units, <option>false</option>
 716                                 for the others.</para></listitem>
 717                         </varlistentry>
 718
 719                         <varlistentry>
 720                                 <term><varname>StopWhenUnneeded=</varname></term>
 721
 722                                 <listitem><para>Takes a boolean
 723                                 argument. If <option>true</option>
 724                                 this unit will be stopped when it is
 725                                 no longer used. Note that in order to
 726                                 minimize the work to be executed,
 727                                 systemd will not stop units by default
 728                                 unless they are conflicting with other
 729                                 units, or the user explicitly
 730                                 requested their shut down. If this
 731                                 option is set, a unit will be
 732                                 automatically cleaned up if no other
 733                                 active unit requires it. Defaults to
 734                                 <option>false</option>.</para></listitem>
 735                         </varlistentry>
 736
 737                         <varlistentry>
 738                                 <term><varname>RefuseManualStart=</varname></term>
 739                                 <term><varname>RefuseManualStop=</varname></term>
 740
 741                                 <listitem><para>Takes a boolean
 742                                 argument. If <option>true</option>
 743                                 this unit can only be activated
 744                                 or deactivated indirectly. In
 745                                 this case explicit start-up
 746                                 or termination requested by the
 747                                 user is denied, however if it is
 748                                 started or stopped as a
 749                                 dependency of another unit, start-up
 750                                 or termination will succeed. This
 751                                 is mostly a safety feature to ensure
 752                                 that the user does not accidentally
 753                                 activate units that are not intended
 754                                 to be activated explicitly, and not
 755                                 accidentally deactivate units that are
 756                                 not intended to be deactivated.
 757                                 These options default to
 758                                 <option>false</option>.</para></listitem>
 759                         </varlistentry>
 760
 761                         <varlistentry>
 762                                 <term><varname>AllowIsolate=</varname></term>
 763
 764                                 <listitem><para>Takes a boolean
 765                                 argument. If <option>true</option>
 766                                 this unit may be used with the
 767                                 <command>systemctl isolate</command>
 768                                 command. Otherwise this will be
 769                                 refused. It probably is a good idea to
 770                                 leave this disabled except for target
 771                                 units that shall be used similar to
 772                                 runlevels in SysV init systems, just
 773                                 as a precaution to avoid unusable
 774                                 system states. This option defaults to
 775                                 <option>false</option>.</para></listitem>
 776                         </varlistentry>
 777
 778                         <varlistentry>
 779                                 <term><varname>DefaultDependencies=</varname></term>
 780
 781                                 <listitem><para>Takes a boolean
 782                                 argument. If <option>true</option>
 783                                 (the default), a few default
 784                                 dependencies will implicitly be
 785                                 created for the unit. The actual
 786                                 dependencies created depend on the
 787                                 unit type. For example, for service
 788                                 units, these dependencies ensure that
 789                                 the service is started only after
 790                                 basic system initialization is
 791                                 completed and is properly terminated on
 792                                 system shutdown. See the respective
 793                                 man pages for details. Generally, only
 794                                 services involved with early boot or
 795                                 late shutdown should set this option
 796                                 to <option>false</option>. It is
 797                                 highly recommended to leave this
 798                                 option enabled for the majority of
 799                                 common units. If set to
 800                                 <option>false</option> this option
 801                                 does not disable all implicit
 802                                 dependencies, just non-essential
 803                                 ones.</para></listitem>
 804                         </varlistentry>
 805
 806                         <varlistentry>
 807                                 <term><varname>JobTimeoutSec=</varname></term>
 808
 809                                 <listitem><para>When clients are
 810                                 waiting for a job of this unit to
 811                                 complete, time out after the specified
 812                                 time. If this time limit is reached
 813                                 the job will be cancelled, the unit
 814                                 however will not change state or even
 815                                 enter the <literal>failed</literal>
 816                                 mode. This value defaults to 0 (job
 817                                 timeouts disabled), except for device
 818                                 units. NB: this timeout is independent
 819                                 from any unit-specific timeout (for
 820                                 example, the timeout set with
 821                                 <varname>Timeout=</varname> in service
 822                                 units) as the job timeout has no
 823                                 effect on the unit itself, only on the
 824                                 job that might be pending for it. Or
 825                                 in other words: unit-specific timeouts
 826                                 are useful to abort unit state
 827                                 changes, and revert them. The job
 828                                 timeout set with this option however
 829                                 is useful to abort only the job
 830                                 waiting for the unit state to
 831                                 change.</para></listitem>
 832                         </varlistentry>
 833
 834                         <varlistentry>
 835                                 <term><varname>ConditionPathExists=</varname></term>
 836                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 837                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 838                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 839                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 840                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 841                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 842                                 <term><varname>ConditionFileNotEmpty=</varname></term>
 843                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 844                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 845                                 <term><varname>ConditionVirtualization=</varname></term>
 846                                 <term><varname>ConditionSecurity=</varname></term>
 847                                 <term><varname>ConditionCapability=</varname></term>
 848                                 <term><varname>ConditionHost=</varname></term>
 849                                 <term><varname>ConditionACPower=</varname></term>
 850                                 <term><varname>ConditionNull=</varname></term>
 851
 852                                 <listitem><para>Before starting a unit
 853                                 verify that the specified condition is
 854                                 true. If it is not true the starting
 855                                 of the unit will be skipped, however
 856                                 all ordering dependencies of it are
 857                                 still respected. A failing condition
 858                                 will not result in the unit being
 859                                 moved into a failure state. The
 860                                 condition is checked at the time the
 861                                 queued start job is to be
 862                                 executed.</para>
 863
 864                                 <para>With
 865                                 <varname>ConditionPathExists=</varname>
 866                                 a file existence condition is
 867                                 checked before a unit is started. If
 868                                 the specified absolute path name does
 869                                 not exist the condition will
 870                                 fail. If the absolute path name passed
 871                                 to
 872                                 <varname>ConditionPathExists=</varname>
 873                                 is prefixed with an exclamation mark
 874                                 (<literal>!</literal>), the test is negated, and the unit
 875                                 is only started if the path does not
 876                                 exist.</para>
 877
 878                                 <para><varname>ConditionPathExistsGlob=</varname>
 879                                 is similar to
 880                                 <varname>ConditionPathExists=</varname>,
 881                                 but checks for the existence of at
 882                                 least one file or directory matching
 883                                 the specified globbing pattern.</para>
 884
 885                                 <para><varname>ConditionPathIsDirectory=</varname>
 886                                 is similar to
 887                                 <varname>ConditionPathExists=</varname>
 888                                 but verifies whether a certain path
 889                                 exists and is a
 890                                 directory.</para>
 891
 892                                 <para><varname>ConditionPathIsSymbolicLink=</varname>
 893                                 is similar to
 894                                 <varname>ConditionPathExists=</varname>
 895                                 but verifies whether a certain path
 896                                 exists and is a symbolic
 897                                 link.</para>
 898
 899                                 <para><varname>ConditionPathIsMountPoint=</varname>
 900                                 is similar to
 901                                 <varname>ConditionPathExists=</varname>
 902                                 but verifies whether a certain path
 903                                 exists and is a mount
 904                                 point.</para>
 905
 906                                 <para><varname>ConditionPathIsReadWrite=</varname>
 907                                 is similar to
 908                                 <varname>ConditionPathExists=</varname>
 909                                 but verifies whether the underlying
 910                                 file system is readable and writable
 911                                 (i.e. not mounted
 912                                 read-only).</para>
 913
 914                                 <para><varname>ConditionDirectoryNotEmpty=</varname>
 915                                 is similar to
 916                                 <varname>ConditionPathExists=</varname>
 917                                 but verifies whether a certain path
 918                                 exists and is a non-empty
 919                                 directory.</para>
 920
 921                                 <para><varname>ConditionFileNotEmpty=</varname>
 922                                 is similar to
 923                                 <varname>ConditionPathExists=</varname>
 924                                 but verifies whether a certain path
 925                                 exists and refers to a regular file
 926                                 with a non-zero size.</para>
 927
 928                                 <para><varname>ConditionFileIsExecutable=</varname>
 929                                 is similar to
 930                                 <varname>ConditionPathExists=</varname>
 931                                 but verifies whether a certain path
 932                                 exists, is a regular file and marked
 933                                 executable.</para>
 934
 935                                 <para>Similar,
 936                                 <varname>ConditionKernelCommandLine=</varname>
 937                                 may be used to check whether a
 938                                 specific kernel command line option is
 939                                 set (or if prefixed with the
 940                                 exclamation mark unset). The argument
 941                                 must either be a single word, or an
 942                                 assignment (i.e. two words, separated
 943                                 <literal>=</literal>). In the former
 944                                 case the kernel command line is
 945                                 searched for the word appearing as is,
 946                                 or as left hand side of an
 947                                 assignment. In the latter case the
 948                                 exact assignment is looked for with
 949                                 right and left hand side
 950                                 matching.</para>
 951
 952                                 <para><varname>ConditionVirtualization=</varname>
 953                                 may be used to check whether the
 954                                 system is executed in a virtualized
 955                                 environment and optionally test
 956                                 whether it is a specific
 957                                 implementation. Takes either boolean
 958                                 value to check if being executed in
 959                                 any virtualized environment, or one of
 960                                 <varname>vm</varname> and
 961                                 <varname>container</varname> to test
 962                                 against a generic type of
 963                                 virtualization solution, or one of
 964                                 <varname>qemu</varname>,
 965                                 <varname>kvm</varname>,
 966                                 <varname>vmware</varname>,
 967                                 <varname>microsoft</varname>,
 968                                 <varname>oracle</varname>,
 969                                 <varname>xen</varname>,
 970                                 <varname>bochs</varname>,
 971                                 <varname>chroot</varname>,
 972                                 <varname>openvz</varname>,
 973                                 <varname>lxc</varname>,
 974                                 <varname>lxc-libvirt</varname>,
 975                                 <varname>systemd-nspawn</varname> to
 976                                 test against a specific
 977                                 implementation. If multiple
 978                                 virtualization technologies are nested
 979                                 only the innermost is considered. The
 980                                 test may be negated by prepending an
 981                                 exclamation mark.</para>
 982
 983                                 <para><varname>ConditionSecurity=</varname>
 984                                 may be used to check whether the given
 985                                 security module is enabled on the
 986                                 system. Currently the recognized values
 987                                 values are <varname>selinux</varname>,
 988                                 <varname>apparmor</varname>,
 989                                 <varname>ima</varname> and
 990                                 <varname>smack</varname>.
 991                                 The test may be negated by prepending
 992                                 an exclamation
 993                                 mark.</para>
 994
 995                                 <para><varname>ConditionCapability=</varname>
 996                                 may be used to check whether the given
 997                                 capability exists in the capability
 998                                 bounding set of the service manager
 999                                 (i.e. this does not check whether
1000                                 capability is actually available in
1001                                 the permitted or effective sets, see
1002                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1003                                 for details). Pass a capability name
1004                                 such as <literal>CAP_MKNOD</literal>,
1005                                 possibly prefixed with an exclamation
1006                                 mark to negate the check.</para>
1007
1008                                 <para><varname>ConditionHost=</varname>
1009                                 may be used to match against the
1010                                 hostname or machine ID of the
1011                                 host. This either takes a hostname
1012                                 string (optionally with shell style
1013                                 globs) which is tested against the
1014                                 locally set hostname as returned by
1015                                 <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
1016                                 or a machine ID formatted as string
1017                                 (see
1018                                 <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
1019                                 The test may be negated by prepending
1020                                 an exclamation mark.</para>
1021
1022                                 <para><varname>ConditionACPower=</varname>
1023                                 may be used to check whether the
1024                                 system has AC power, or is exclusively
1025                                 battery powered at the time of
1026                                 activation of the unit. This takes a
1027                                 boolean argument. If set to
1028                                 <varname>true</varname> the condition
1029                                 will hold only if at least one AC
1030                                 connector of the system is connected
1031                                 to a power source, or if no AC
1032                                 connectors are known. Conversely, if
1033                                 set to <varname>false</varname> the
1034                                 condition will hold only if there is
1035                                 at least one AC connector known and
1036                                 all AC connectors are disconnected
1037                                 from a power source.</para>
1038
1039                                 <para>Finally,
1040                                 <varname>ConditionNull=</varname> may
1041                                 be used to add a constant condition
1042                                 check value to the unit. It takes a
1043                                 boolean argument. If set to
1044                                 <varname>false</varname> the condition
1045                                 will always fail, otherwise
1046                                 succeed.</para>
1047
1048                                 <para>If multiple conditions are
1049                                 specified the unit will be executed if
1050                                 all of them apply (i.e. a logical AND
1051                                 is applied). Condition checks can be
1052                                 prefixed with a pipe symbol (|) in
1053                                 which case a condition becomes a
1054                                 triggering condition. If at least one
1055                                 triggering condition is defined for a
1056                                 unit then the unit will be executed if
1057                                 at least one of the triggering
1058                                 conditions apply and all of the
1059                                 non-triggering conditions. If you
1060                                 prefix an argument with the pipe
1061                                 symbol and an exclamation mark the
1062                                 pipe symbol must be passed first, the
1063                                 exclamation second. Except for
1064                                 <varname>ConditionPathIsSymbolicLink=</varname>,
1065                                 all path checks follow symlinks. If
1066                                 any of these options is assigned the
1067                                 empty string the list of conditions is
1068                                 reset completely, all previous
1069                                 condition settings (of any kind) will
1070                                 have no effect.</para></listitem>
1071                         </varlistentry>
1072
1073                         <varlistentry>
1074                                 <term><varname>SourcePath=</varname></term>
1075                                 <listitem><para>A path to a
1076                                 configuration file this unit has been
1077                                 generated from. This is primarily
1078                                 useful for implementation of generator
1079                                 tools that convert configuration from
1080                                 an external configuration file format
1081                                 into native unit files. Thus
1082                                 functionality should not be used in
1083                                 normal units.</para></listitem>
1084                         </varlistentry>
1085                 </variablelist>
1086
1087                 <para>Unit file may include a [Install] section, which
1088                 carries installation information for the unit. This
1089                 section is not interpreted by
1090                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1091                 during runtime. It is used exclusively by the
1092                 <command>enable</command> and
1093                 <command>disable</command> commands of the
1094                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1095                 tool during installation of a unit:</para>
1096
1097                 <variablelist class='unit-directives'>
1098                         <varlistentry>
1099                                 <term><varname>Alias=</varname></term>
1100
1101                                 <listitem><para>Additional names this
1102                                 unit shall be installed under. The
1103                                 names listed here must have the same
1104                                 suffix (i.e. type) as the unit file
1105                                 name. This option may be specified
1106                                 more than once, in which case all
1107                                 listed names are used. At installation
1108                                 time,
1109                                 <command>systemctl enable</command>
1110                                 will create symlinks from these names
1111                                 to the unit filename.</para></listitem>
1112                         </varlistentry>
1113
1114                         <varlistentry>
1115                                 <term><varname>WantedBy=</varname></term>
1116                                 <term><varname>RequiredBy=</varname></term>
1117
1118                                 <listitem><para>Installs a symlink in
1119                                 the <filename>.wants/</filename>
1120                                 or <filename>.requires/</filename>
1121                                 subdirectory for a unit, respectively. This has the
1122                                 effect that when the listed unit name
1123                                 is activated the unit listing it is
1124                                 activated
1125                                 too. <command>WantedBy=foo.service</command>
1126                                 in a service
1127                                 <filename>bar.service</filename> is
1128                                 mostly equivalent to
1129                                 <command>Alias=foo.service.wants/bar.service</command>
1130                                 in the same file.</para></listitem>
1131                         </varlistentry>
1132
1133                         <varlistentry>
1134                                 <term><varname>Also=</varname></term>
1135
1136                                 <listitem><para>Additional units to
1137                                 install/deinstall when this unit is
1138                                 installed/deinstalled. If the user
1139                                 requests installation/deinstallation
1140                                 of a unit with this option configured,
1141                                 <command>systemctl enable</command>
1142                                 and <command>systemctl
1143                                 disable</command> will automatically
1144                                 install/uninstall units listed in this option as
1145                                 well.</para></listitem>
1146                         </varlistentry>
1147                 </variablelist>
1148
1149                 <para>The following specifiers are interpreted in the
1150                 Install section: %n, %N, %p, %i, %U, %u, %m, %H, %b.
1151                 For their meaning see the next section.
1152                 </para>
1153         </refsect1>
1154
1155         <refsect1>
1156                 <title>Specifiers</title>
1157
1158                 <para>Many settings resolve specifiers which may be
1159                 used to write generic unit files referring to runtime
1160                 or unit parameters that are replaced when the unit
1161                 files are loaded. The following specifiers are
1162                 understood:</para>
1163
1164                 <table>
1165                   <title>Specifiers available in unit files</title>
1166                   <tgroup cols='3' align='left' colsep='1' rowsep='1'>
1167                     <colspec colname="spec" />
1168                     <colspec colname="mean" />
1169                     <colspec colname="detail" />
1170                     <thead>
1171                       <row>
1172                         <entry>Specifier</entry>
1173                         <entry>Meaning</entry>
1174                         <entry>Details</entry>
1175                       </row>
1176                     </thead>
1177                     <tbody>
1178                       <row>
1179                         <entry><literal>%n</literal></entry>
1180                         <entry>Full unit name</entry>
1181                         <entry></entry>
1182                       </row>
1183                       <row>
1184                         <entry><literal>%N</literal></entry>
1185                         <entry>Unescaped full unit name</entry>
1186                         <entry></entry>
1187                       </row>
1188                       <row>
1189                         <entry><literal>%p</literal></entry>
1190                         <entry>Prefix name</entry>
1191                         <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>
1192                       </row>
1193                       <row>
1194                         <entry><literal>%P</literal></entry>
1195                         <entry>Unescaped prefix name</entry>
1196                         <entry></entry>
1197                       </row>
1198                       <row>
1199                         <entry><literal>%i</literal></entry>
1200                         <entry>Instance name</entry>
1201                         <entry>For instantiated units: this is the string between the <literal>@</literal> character and the suffix.</entry>
1202                       </row>
1203                       <row>
1204                         <entry><literal>%I</literal></entry>
1205                         <entry>Unescaped instance name</entry>
1206                         <entry></entry>
1207                       </row>
1208                       <row>
1209                         <entry><literal>%f</literal></entry>
1210                         <entry>Unescaped filename</entry>
1211                         <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>
1212                       </row>
1213                       <row>
1214                         <entry><literal>%c</literal></entry>
1215                         <entry>Control group path of the unit</entry>
1216                         <entry></entry>
1217                       </row>
1218                       <row>
1219                         <entry><literal>%r</literal></entry>
1220                         <entry>Root control group path where units are placed.</entry>
1221                         <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>
1222                       </row>
1223                       <row>
1224                         <entry><literal>%R</literal></entry>
1225                         <entry>Parent directory of the control group path where units are placed.</entry>
1226                         <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>
1227                       </row>
1228                       <row>
1229                         <entry><literal>%t</literal></entry>
1230                         <entry>Runtime socket dir</entry>
1231                         <entry>This is either <filename>/run</filename> (for the system manager) or <literal>$XDG_RUNTIME_DIR</literal> (for user managers).</entry>
1232                       </row>
1233                       <row>
1234                         <entry><literal>%u</literal></entry>
1235                         <entry>User name</entry>
1236                         <entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1237                       </row>
1238                       <row>
1239                         <entry><literal>%U</literal></entry>
1240                         <entry>User UID</entry>
1241                         <entry>This is the UID of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1242                       </row>
1243                       <row>
1244                         <entry><literal>%h</literal></entry>
1245                         <entry>User home directory</entry>
1246                         <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>
1247                       </row>
1248                       <row>
1249                         <entry><literal>%s</literal></entry>
1250                         <entry>User shell</entry>
1251                         <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>
1252                       </row>
1253                       <row>
1254                         <entry><literal>%m</literal></entry>
1255                         <entry>Machine ID</entry>
1256                         <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>
1257                       </row>
1258                       <row>
1259                         <entry><literal>%b</literal></entry>
1260                         <entry>Boot ID</entry>
1261                         <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
1262                       </row>
1263                       <row>
1264                         <entry><literal>%H</literal></entry>
1265                         <entry>Host name</entry>
1266                         <entry>The hostname of the running system.</entry>
1267                       </row>
1268                       <row>
1269                         <entry><literal>%%</literal></entry>
1270                         <entry>Escaped %</entry>
1271                         <entry>Single percent sign.</entry>
1272                       </row>
1273                     </tbody>
1274                   </tgroup>
1275                 </table>
1276         </refsect1>
1277
1278         <refsect1>
1279                 <title>See Also</title>
1280                 <para>
1281                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1282                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1283                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1284                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1285                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1286                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1287                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1288                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1289                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1290                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1291                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1292                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1293                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1294                         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1295                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1296                         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1297                 </para>
1298         </refsect1>
1299
1300 </refentry>