man/systemd.unit.xml

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   7
   8 <!--
   9   This file is part of systemd.
  10
  11   Copyright 2010 Lennart Poettering
  12
  13   systemd is free software; you can redistribute it and/or modify it
  14   under the terms of the GNU Lesser General Public License as published by
  15   the Free Software Foundation; either version 2.1 of the License, or
  16   (at your option) any later version.
  17
  18   systemd is distributed in the hope that it will be useful, but
  19   WITHOUT ANY WARRANTY; without even the implied warranty of
  20   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  21   Lesser General Public License for more details.
  22
  23   You should have received a copy of the GNU Lesser General Public License
  24   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  25 -->
  26
  27 <refentry id="systemd.unit">
  28
  29         <refentryinfo>
  30                 <title>systemd.unit</title>
  31                 <productname>systemd</productname>
  32
  33                 <authorgroup>
  34                         <author>
  35                                 <contrib>Developer</contrib>
  36                                 <firstname>Lennart</firstname>
  37                                 <surname>Poettering</surname>
  38                                 <email>lennart@poettering.net</email>
  39                         </author>
  40                 </authorgroup>
  41         </refentryinfo>
  42
  43         <refmeta>
  44                 <refentrytitle>systemd.unit</refentrytitle>
  45                 <manvolnum>5</manvolnum>
  46         </refmeta>
  47
  48         <refnamediv>
  49                 <refname>systemd.unit</refname>
  50                 <refpurpose>Unit configuration</refpurpose>
  51         </refnamediv>
  52
  53         <refsynopsisdiv>
  54                 <para><filename><replaceable>service</replaceable>.service</filename>,
  55                 <filename><replaceable>socket</replaceable>.socket</filename>,
  56                 <filename><replaceable>device</replaceable>.device</filename>,
  57                 <filename><replaceable>mount</replaceable>.mount</filename>,
  58                 <filename><replaceable>automount</replaceable>.automount</filename>,
  59                 <filename><replaceable>swap</replaceable>.swap</filename>,
  60                 <filename><replaceable>target</replaceable>.target</filename>,
  61                 <filename><replaceable>path</replaceable>.path</filename>,
  62                 <filename><replaceable>timer</replaceable>.timer</filename>,
  63                 <filename><replaceable>snapshot</replaceable>.snapshot</filename>,
  64                 <filename><replaceable>slice</replaceable>.slice</filename>,
  65                 <filename><replaceable>scope</replaceable>.scope</filename></para>
  66
  67                 <para><literallayout><filename>/etc/systemd/system/*</filename>
  68 <filename>/run/systemd/system/*</filename>
  69 <filename>/usr/lib/systemd/system/*</filename>
  70 <filename>...</filename>
  71                 </literallayout></para>
  72
  73                 <para><literallayout><filename>$HOME/.config/systemd/user/*</filename>
  74 <filename>/etc/systemd/user/*</filename>
  75 <filename>/run/systemd/user/*</filename>
  76 <filename>/usr/lib/systemd/user/*</filename>
  77 <filename>...</filename>
  78                 </literallayout></para>
  79         </refsynopsisdiv>
  80
  81         <refsect1>
  82                 <title>Description</title>
  83
  84                 <para>A unit configuration file encodes information
  85                 about a service, a socket, a device, a mount point, an
  86                 automount point, a swap file or partition, a start-up
  87                 target, a watched file system path, a timer controlled
  88                 and supervised by
  89                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  90                 a temporary system state snapshot, a resource
  91                 management slice or a group of externally created
  92                 processes. The syntax is inspired by <ulink
  93                 url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
  94                 Desktop Entry Specification</ulink>
  95                 <filename>.desktop</filename> files, which are in turn
  96                 inspired by Microsoft Windows
  97                 <filename>.ini</filename> files.</para>
  98
  99                 <para>This man page lists the common configuration
 100                 options of all the unit types. These options need to
 101                 be configured in the [Unit] or [Install]
 102                 sections of the unit files.</para>
 103
 104                 <para>In addition to the generic [Unit] and [Install]
 105                 sections described here, each unit may have a
 106                 type-specific section, e.g. [Service] for a service
 107                 unit. See the respective man pages for more
 108                 information:
 109                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 110                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 111                 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 112                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 113                 <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 114                 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 115                 <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 116                 <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 117                 <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 118                 <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 119                 <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 120                 <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 121                 </para>
 122
 123                 <para>Unit files are loaded from a set of paths
 124                 determined during compilation, described in the next section.
 125                 </para>
 126
 127                 <para>Unit files may contain additional options on top
 128                 of those listed here. If systemd encounters an unknown
 129                 option it will write a warning log message but
 130                 continue loading the unit. If an option is prefixed
 131                 with <option>X-</option> it is ignored completely by
 132                 systemd. Applications may use this to include
 133                 additional information in the unit files.</para>
 134
 135                 <para>Boolean arguments used in unit files can be
 136                 written in various formats. For positive settings the
 137                 strings <option>1</option>, <option>yes</option>,
 138                 <option>true</option> and <option>on</option> are
 139                 equivalent. For negative settings the strings
 140                 <option>0</option>, <option>no</option>,
 141                 <option>false</option> and <option>off</option> are
 142                 equivalent.</para>
 143
 144                 <para>Time span values encoded in unit files can be
 145                 written in various formats. A stand-alone number
 146                 specifies a time in seconds. If suffixed with a time
 147                 unit, the unit is honored. A concatenation of multiple
 148                 values with units is supported, in which case the
 149                 values are added up. Example: "50" refers to 50
 150                 seconds; "2min 200ms" refers to 2 minutes plus 200
 151                 milliseconds, i.e. 120200ms. The following time units
 152                 are understood: s, min, h, d, w, ms, us. For details
 153                 see
 154                 <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 155
 156                 <para>Empty lines and lines starting with # or ; are
 157                 ignored. This may be used for commenting. Lines ending
 158                 in a backslash are concatenated with the following
 159                 line while reading and the backslash is replaced by a
 160                 space character. This may be used to wrap long lines.</para>
 161
 162                 <para>Along with a unit file
 163                 <filename>foo.service</filename> the directory
 164                 <filename>foo.service.wants/</filename> may exist. All
 165                 unit files symlinked from such a directory are
 166                 implicitly added as dependencies of type
 167                 <varname>Wanted=</varname> to the unit. This is useful
 168                 to hook units into the start-up of other units,
 169                 without having to modify their unit files. For details
 170                 about the semantics of <varname>Wanted=</varname> see
 171                 below. The preferred way to create symlinks in the
 172                 <filename>.wants/</filename> directory of a unit file
 173                 is with the <command>enable</command> command of the
 174                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 175                 tool which reads information from the [Install]
 176                 section of unit files (see below). A similar
 177                 functionality exists for <varname>Requires=</varname>
 178                 type dependencies as well, the directory suffix is
 179                 <filename>.requires/</filename> in this case.</para>
 180
 181                 <para>Along with a unit file
 182                 <filename>foo.service</filename> a directory
 183                 <filename>foo.service.d/</filename> may exist. All
 184                 files with the suffix <literal>.conf</literal> from
 185                 this directory will be parsed after the file itself is
 186                 parsed. This is useful to alter or add configuration
 187                 settings to a unit, without having to modify their
 188                 unit files. Make sure that the file that is included
 189                 has the appropriate section headers before any
 190                 directive.</para>
 191
 192                 <para>If a line starts with <option>.include</option>
 193                 followed by a filename, the specified file will be
 194                 parsed at this point. Make sure that the file that is
 195                 included has the appropriate section headers before
 196                 any directives.</para>
 197
 198                 <para>Note that while systemd offers a flexible
 199                 dependency system between units it is recommended to
 200                 use this functionality only sparingly and instead rely
 201                 on techniques such as bus-based or socket-based
 202                 activation which make dependencies implicit, resulting
 203                 in a both simpler and more flexible system.</para>
 204
 205                 <para>Some unit names reflect paths existing in the
 206                 file system namespace. Example: a device unit
 207                 <filename>dev-sda.device</filename> refers to a device
 208                 with the device node <filename noindex='true'>/dev/sda</filename> in
 209                 the file system namespace. If this applies a special
 210                 way to escape the path name is used, so that the
 211                 result is usable as part of a filename. Basically,
 212                 given a path, "/" is replaced by "-", and all
 213                 unprintable characters and the "-" are replaced by
 214                 C-style "\x20" escapes. The root directory "/" is
 215                 encoded as single dash, while otherwise the initial
 216                 and ending "/" is removed from all paths during
 217                 transformation. This escaping is reversible.</para>
 218
 219                 <para>Optionally, units may be instantiated from a
 220                 template file at runtime. This allows creation of
 221                 multiple units from a single configuration file. If
 222                 systemd looks for a unit configuration file it will
 223                 first search for the literal unit name in the
 224                 filesystem. If that yields no success and the unit
 225                 name contains an <literal>@</literal> character, systemd will look for a
 226                 unit template that shares the same name but with the
 227                 instance string (i.e. the part between the <literal>@</literal> character
 228                 and the suffix) removed. Example: if a service
 229                 <filename>getty@tty3.service</filename> is requested
 230                 and no file by that name is found, systemd will look
 231                 for <filename>getty@.service</filename> and
 232                 instantiate a service from that configuration file if
 233                 it is found.</para>
 234
 235                 <para>To refer to the instance string from
 236                 within the configuration file you may use the special
 237                 <literal>%i</literal> specifier in many of the
 238                 configuration options. See below for details.</para>
 239
 240                 <para>If a unit file is empty (i.e. has the file size
 241                 0) or is symlinked to <filename>/dev/null</filename>
 242                 its configuration will not be loaded and it appears
 243                 with a load state of <literal>masked</literal>, and
 244                 cannot be activated. Use this as an effective way to
 245                 fully disable a unit, making it impossible to start it
 246                 even manually.</para>
 247
 248                 <para>The unit file format is covered by the
 249                 <ulink
 250                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 251                 Stability Promise</ulink>.</para>
 252
 253         </refsect1>
 254
 255         <refsect1>
 256                 <title>Unit Load Path</title>
 257
 258                 <para>Unit files are loaded from a set of paths
 259                 determined during compilation, described in the two
 260                 tables below. Unit files found in directories listed
 261                 earlier override files with the same name in
 262                 directories lower in the list.</para>
 263
 264                 <para>When systemd is running in user mode
 265                 (<option>--user</option>) and the variable
 266                 <varname>$SYSTEMD_UNIT_PATH</varname> is set, this
 267                 contents of this variable overrides the unit load
 268                 path.
 269                 </para>
 270
 271                 <table>
 272                   <title>
 273                     Load path when running in system mode (<option>--system</option>).
 274                   </title>
 275
 276                   <tgroup cols='2'>
 277                     <colspec colname='path' />
 278                     <colspec colname='expl' />
 279                     <thead>
 280                       <row>
 281                         <entry>Path</entry>
 282                         <entry>Description</entry>
 283                       </row>
 284                     </thead>
 285                     <tbody>
 286                       <row>
 287                         <entry><filename>/etc/systemd/system</filename></entry>
 288                         <entry>Local configuration</entry>
 289                       </row>
 290                       <row>
 291                         <entry><filename>/run/systemd/system</filename></entry>
 292                         <entry>Runtime units</entry>
 293                       </row>
 294                       <row>
 295                         <entry><filename>/usr/lib/systemd/system</filename></entry>
 296                         <entry>Units of installed packages</entry>
 297                       </row>
 298                     </tbody>
 299                   </tgroup>
 300                 </table>
 301
 302                 <table>
 303                   <title>
 304                     Load path when running in user mode (<option>--user</option>).
 305                   </title>
 306
 307                   <tgroup cols='2'>
 308                     <colspec colname='path' />
 309                     <colspec colname='expl' />
 310                     <thead>
 311                       <row>
 312                         <entry>Path</entry>
 313                         <entry>Description</entry>
 314                       </row>
 315                     </thead>
 316                     <tbody>
 317                       <row>
 318                         <entry><filename>$HOME/.config/systemd/user</filename></entry>
 319                         <entry>User configuration</entry>
 320                       </row>
 321                       <row>
 322                         <entry><filename>/etc/systemd/user</filename></entry>
 323                         <entry>Local configuration</entry>
 324                       </row>
 325                       <row>
 326                         <entry><filename>/run/systemd/user</filename></entry>
 327                         <entry>Runtime units</entry>
 328                       </row>
 329                       <row>
 330                         <entry><filename>/usr/lib/systemd/user</filename></entry>
 331                         <entry>Units of installed packages</entry>
 332                       </row>
 333                     </tbody>
 334                   </tgroup>
 335                 </table>
 336
 337                 <para>Additional units might be loaded into systemd
 338                 ("linked") from directories not on the unit load
 339                 path. See the <command>link</command> command for
 340                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>. Also,
 341                 some units are dynamically created via generators
 342                 <ulink
 343                 url="http://www.freedesktop.org/wiki/Software/systemd/Generators/">Generators</ulink>.
 344                 </para>
 345         </refsect1>
 346
 347         <refsect1>
 348                 <title>Options</title>
 349
 350                 <para>Unit file may include a [Unit] section, which
 351                 carries generic information about the unit that is not
 352                 dependent on the type of unit:</para>
 353
 354                 <variablelist class='unit-directives'>
 355
 356                         <varlistentry>
 357                                 <term><varname>Description=</varname></term>
 358                                 <listitem><para>A free-form string
 359                                 describing the unit. This is intended
 360                                 for use in UIs to show descriptive
 361                                 information along with the unit
 362                                 name.</para></listitem>
 363                         </varlistentry>
 364
 365                         <varlistentry>
 366                                 <term><varname>Documentation=</varname></term>
 367                                 <listitem><para>A space-separated list
 368                                 of URIs referencing documentation for
 369                                 this unit or its
 370                                 configuration. Accepted are only URIs
 371                                 of the types
 372                                 <literal>http://</literal>,
 373                                 <literal>https://</literal>,
 374                                 <literal>file:</literal>,
 375                                 <literal>info:</literal>,
 376                                 <literal>man:</literal>. For more
 377                                 information about the syntax of these
 378                                 URIs, see
 379                                 <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
 380                                 URIs should be listed in order of
 381                                 relevance, starting with the most
 382                                 relevant. It is a good idea to first
 383                                 reference documentation that explains
 384                                 what the unit's purpose is, followed
 385                                 by how it is configured, followed by
 386                                 any other related documentation. This
 387                                 option may be specified more than once
 388                                 in which case the specified list of
 389                                 URIs is merged. If the empty string is
 390                                 assigned to this option, the list is
 391                                 reset and all prior assignments will
 392                                 have no effect.</para></listitem>
 393                         </varlistentry>
 394
 395                         <varlistentry>
 396                                 <term><varname>Requires=</varname></term>
 397
 398                                 <listitem><para>Configures requirement
 399                                 dependencies on other units. If this
 400                                 unit gets activated, the units listed
 401                                 here will be activated as well. If one
 402                                 of the other units gets deactivated or
 403                                 its activation fails, this unit will
 404                                 be deactivated. This option may be
 405                                 specified more than once, in which
 406                                 case requirement dependencies for all
 407                                 listed names are created. Note that
 408                                 requirement dependencies do not
 409                                 influence the order in which services
 410                                 are started or stopped. This has to be
 411                                 configured independently with the
 412                                 <varname>After=</varname> or
 413                                 <varname>Before=</varname> options. If
 414                                 a unit
 415                                 <filename>foo.service</filename>
 416                                 requires a unit
 417                                 <filename>bar.service</filename> as
 418                                 configured with
 419                                 <varname>Requires=</varname> and no
 420                                 ordering is configured with
 421                                 <varname>After=</varname> or
 422                                 <varname>Before=</varname>, then both
 423                                 units will be started simultaneously
 424                                 and without any delay between them if
 425                                 <filename>foo.service</filename> is
 426                                 activated. Often it is a better choice
 427                                 to use <varname>Wants=</varname>
 428                                 instead of
 429                                 <varname>Requires=</varname> in order
 430                                 to achieve a system that is more
 431                                 robust when dealing with failing
 432                                 services.</para>
 433
 434                                 <para>Note that dependencies of this
 435                                 type may also be configured outside of
 436                                 the unit configuration file by
 437                                 adding a symlink to a
 438                                 <filename>.requires/</filename> directory
 439                                 accompanying the unit file. For
 440                                 details see above.</para></listitem>
 441                         </varlistentry>
 442
 443                         <varlistentry>
 444                                 <term><varname>RequiresOverridable=</varname></term>
 445
 446                                 <listitem><para>Similar to
 447                                 <varname>Requires=</varname>.
 448                                 Dependencies listed in
 449                                 <varname>RequiresOverridable=</varname>
 450                                 which cannot be fulfilled or fail to
 451                                 start are ignored if the startup was
 452                                 explicitly requested by the user. If
 453                                 the start-up was pulled in indirectly
 454                                 by some dependency or automatic
 455                                 start-up of units that is not
 456                                 requested by the user this dependency
 457                                 must be fulfilled and otherwise the
 458                                 transaction fails. Hence, this option
 459                                 may be used to configure dependencies
 460                                 that are normally honored unless the
 461                                 user explicitly starts up the unit, in
 462                                 which case whether they failed or not
 463                                 is irrelevant.</para></listitem>
 464
 465                         </varlistentry>
 466                         <varlistentry>
 467                                 <term><varname>Requisite=</varname></term>
 468                                 <term><varname>RequisiteOverridable=</varname></term>
 469
 470                                 <listitem><para>Similar to
 471                                 <varname>Requires=</varname>
 472                                 and <varname>RequiresOverridable=</varname>, respectively. However,
 473                                 if a unit listed here is not started
 474                                 already it will not be started and the
 475                                 transaction fails
 476                                 immediately.</para></listitem>
 477                         </varlistentry>
 478
 479                         <varlistentry>
 480                                 <term><varname>Wants=</varname></term>
 481
 482                                 <listitem><para>A weaker version of
 483                                 <varname>Requires=</varname>. A unit
 484                                 listed in this option will be started
 485                                 if the configuring unit is. However,
 486                                 if the listed unit fails to start up
 487                                 or cannot be added to the transaction
 488                                 this has no impact on the validity of
 489                                 the transaction as a whole. This is
 490                                 the recommended way to hook start-up
 491                                 of one unit to the start-up of another
 492                                 unit.</para>
 493
 494                                 <para>Note that dependencies of this
 495                                 type may also be configured outside of
 496                                 the unit configuration file by
 497                                 adding a symlink to a
 498                                 <filename>.wants/</filename> directory
 499                                 accompanying the unit file. For
 500                                 details see above.</para></listitem>
 501                         </varlistentry>
 502
 503                         <varlistentry>
 504                                 <term><varname>BindsTo=</varname></term>
 505
 506                                 <listitem><para>Configures requirement
 507                                 dependencies, very similar in style to
 508                                 <varname>Requires=</varname>, however
 509                                 in addition to this behavior it also
 510                                 declares that this unit is stopped
 511                                 when any of the units listed suddenly
 512                                 disappears. Units can suddenly,
 513                                 unexpectedly disappear if a service
 514                                 terminates on its own choice, a device
 515                                 is unplugged or a mount point
 516                                 unmounted without involvement of
 517                                 systemd.</para></listitem>
 518                         </varlistentry>
 519
 520                         <varlistentry>
 521                                 <term><varname>PartOf=</varname></term>
 522
 523                                 <listitem><para>Configures dependencies
 524                                 similar to <varname>Requires=</varname>,
 525                                 but limited to stopping and restarting
 526                                 of units. When systemd stops or restarts
 527                                 the units listed here, the action is
 528                                 propagated to this unit.
 529                                 Note that this is a one way dependency -
 530                                 changes to this unit do not affect the
 531                                 listed units.
 532                                 </para></listitem>
 533                         </varlistentry>
 534
 535                         <varlistentry>
 536                                 <term><varname>Conflicts=</varname></term>
 537
 538                                 <listitem><para>Configures negative
 539                                 requirement dependencies. If a unit
 540                                 has a
 541                                 <varname>Conflicts=</varname> setting
 542                                 on another unit, starting the former
 543                                 will stop the latter and vice
 544                                 versa. Note that this setting is
 545                                 independent of and orthogonal to the
 546                                 <varname>After=</varname> and
 547                                 <varname>Before=</varname> ordering
 548                                 dependencies.</para>
 549
 550                                 <para>If a unit A that conflicts with
 551                                 a unit B is scheduled to be started at
 552                                 the same time as B, the transaction
 553                                 will either fail (in case both are
 554                                 required part of the transaction) or
 555                                 be modified to be fixed (in case one
 556                                 or both jobs are not a required part
 557                                 of the transaction). In the latter
 558                                 case the job that is not the required
 559                                 will be removed, or in case both are
 560                                 not required the unit that conflicts
 561                                 will be started and the unit that is
 562                                 conflicted is
 563                                 stopped.</para></listitem>
 564                         </varlistentry>
 565
 566                         <varlistentry>
 567                                 <term><varname>Before=</varname></term>
 568                                 <term><varname>After=</varname></term>
 569
 570                                 <listitem><para>Configures ordering
 571                                 dependencies between units. If a unit
 572                                 <filename>foo.service</filename>
 573                                 contains a setting
 574                                 <option>Before=bar.service</option>
 575                                 and both units are being started,
 576                                 <filename>bar.service</filename>'s
 577                                 start-up is delayed until
 578                                 <filename>foo.service</filename> is
 579                                 started up. Note that this setting is
 580                                 independent of and orthogonal to the
 581                                 requirement dependencies as configured
 582                                 by <varname>Requires=</varname>. It is
 583                                 a common pattern to include a unit
 584                                 name in both the
 585                                 <varname>After=</varname> and
 586                                 <varname>Requires=</varname> option in
 587                                 which case the unit listed will be
 588                                 started before the unit that is
 589                                 configured with these options. This
 590                                 option may be specified more than
 591                                 once, in which case ordering
 592                                 dependencies for all listed names are
 593                                 created. <varname>After=</varname> is
 594                                 the inverse of
 595                                 <varname>Before=</varname>, i.e. while
 596                                 <varname>After=</varname> ensures that
 597                                 the configured unit is started after
 598                                 the listed unit finished starting up,
 599                                 <varname>Before=</varname> ensures the
 600                                 opposite, i.e.  that the configured
 601                                 unit is fully started up before the
 602                                 listed unit is started. Note that when
 603                                 two units with an ordering dependency
 604                                 between them are shut down, the
 605                                 inverse of the start-up order is
 606                                 applied. i.e. if a unit is configured
 607                                 with <varname>After=</varname> on
 608                                 another unit, the former is stopped
 609                                 before the latter if both are shut
 610                                 down. If one unit with an ordering
 611                                 dependency on another unit is shut
 612                                 down while the latter is started up,
 613                                 the shut down is ordered before the
 614                                 start-up regardless whether the
 615                                 ordering dependency is actually of
 616                                 type <varname>After=</varname> or
 617                                 <varname>Before=</varname>. If two
 618                                 units have no ordering dependencies
 619                                 between them they are shut down
 620                                 or started up simultaneously, and
 621                                 no ordering takes
 622                                 place. </para></listitem>
 623                         </varlistentry>
 624
 625                         <varlistentry>
 626                                 <term><varname>OnFailure=</varname></term>
 627
 628                                 <listitem><para>Lists one or more
 629                                 units that are activated when this
 630                                 unit enters the
 631                                 <literal>failed</literal>
 632                                 state.</para></listitem>
 633                         </varlistentry>
 634
 635                         <varlistentry>
 636                                 <term><varname>PropagatesReloadTo=</varname></term>
 637                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 638
 639                                 <listitem><para>Lists one or more
 640                                 units where reload requests on the
 641                                 unit will be propagated to/on the
 642                                 other unit will be propagated
 643                                 from. Issuing a reload request on a
 644                                 unit will automatically also enqueue a
 645                                 reload request on all units that the
 646                                 reload request shall be propagated to
 647                                 via these two
 648                                 settings.</para></listitem>
 649                         </varlistentry>
 650
 651                         <varlistentry>
 652                                 <term><varname>RequiresMountsFor=</varname></term>
 653
 654                                 <listitem><para>Takes a space-separated
 655                                 list of absolute paths. Automatically
 656                                 adds dependencies of type
 657                                 <varname>Requires=</varname> and
 658                                 <varname>After=</varname> for all
 659                                 mount units required to access the
 660                                 specified path.</para></listitem>
 661                         </varlistentry>
 662
 663                         <varlistentry>
 664                                 <term><varname>OnFailureIsolate=</varname></term>
 665
 666                                 <listitem><para>Takes a boolean
 667                                 argument. If <option>true</option> the
 668                                 unit listed in
 669                                 <varname>OnFailure=</varname> will be
 670                                 enqueued in isolation mode, i.e. all
 671                                 units that are not its dependency will
 672                                 be stopped. If this is set only a
 673                                 single unit may be listed in
 674                                 <varname>OnFailure=</varname>. Defaults
 675                                 to
 676                                 <option>false</option>.</para></listitem>
 677                         </varlistentry>
 678
 679                         <varlistentry>
 680                                 <term><varname>IgnoreOnIsolate=</varname></term>
 681
 682                                 <listitem><para>Takes a boolean
 683                                 argument. If <option>true</option>
 684                                 this unit will not be stopped when
 685                                 isolating another unit. Defaults to
 686                                 <option>false</option>.</para></listitem>
 687                         </varlistentry>
 688
 689                         <varlistentry>
 690                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 691
 692                                 <listitem><para>Takes a boolean
 693                                 argument. If <option>true</option>
 694                                 this unit will not be included in
 695                                 snapshots. Defaults to
 696                                 <option>true</option> for device and
 697                                 snapshot units, <option>false</option>
 698                                 for the others.</para></listitem>
 699                         </varlistentry>
 700
 701                         <varlistentry>
 702                                 <term><varname>StopWhenUnneeded=</varname></term>
 703
 704                                 <listitem><para>Takes a boolean
 705                                 argument. If <option>true</option>
 706                                 this unit will be stopped when it is
 707                                 no longer used. Note that in order to
 708                                 minimize the work to be executed,
 709                                 systemd will not stop units by default
 710                                 unless they are conflicting with other
 711                                 units, or the user explicitly
 712                                 requested their shut down. If this
 713                                 option is set, a unit will be
 714                                 automatically cleaned up if no other
 715                                 active unit requires it. Defaults to
 716                                 <option>false</option>.</para></listitem>
 717                         </varlistentry>
 718
 719                         <varlistentry>
 720                                 <term><varname>RefuseManualStart=</varname></term>
 721                                 <term><varname>RefuseManualStop=</varname></term>
 722
 723                                 <listitem><para>Takes a boolean
 724                                 argument. If <option>true</option>
 725                                 this unit can only be activated
 726                                 or deactivated indirectly. In
 727                                 this case explicit start-up
 728                                 or termination requested by the
 729                                 user is denied, however if it is
 730                                 started or stopped as a
 731                                 dependency of another unit, start-up
 732                                 or termination will succeed. This
 733                                 is mostly a safety feature to ensure
 734                                 that the user does not accidentally
 735                                 activate units that are not intended
 736                                 to be activated explicitly, and not
 737                                 accidentally deactivate units that are
 738                                 not intended to be deactivated.
 739                                 These options default to
 740                                 <option>false</option>.</para></listitem>
 741                         </varlistentry>
 742
 743                         <varlistentry>
 744                                 <term><varname>AllowIsolate=</varname></term>
 745
 746                                 <listitem><para>Takes a boolean
 747                                 argument. If <option>true</option>
 748                                 this unit may be used with the
 749                                 <command>systemctl isolate</command>
 750                                 command. Otherwise this will be
 751                                 refused. It probably is a good idea to
 752                                 leave this disabled except for target
 753                                 units that shall be used similar to
 754                                 runlevels in SysV init systems, just
 755                                 as a precaution to avoid unusable
 756                                 system states. This option defaults to
 757                                 <option>false</option>.</para></listitem>
 758                         </varlistentry>
 759
 760                         <varlistentry>
 761                                 <term><varname>DefaultDependencies=</varname></term>
 762
 763                                 <listitem><para>Takes a boolean
 764                                 argument. If <option>true</option>
 765                                 (the default), a few default
 766                                 dependencies will implicitly be
 767                                 created for the unit. The actual
 768                                 dependencies created depend on the
 769                                 unit type. For example, for service
 770                                 units, these dependencies ensure that
 771                                 the service is started only after
 772                                 basic system initialization is
 773                                 completed and is properly terminated on
 774                                 system shutdown. See the respective
 775                                 man pages for details. Generally, only
 776                                 services involved with early boot or
 777                                 late shutdown should set this option
 778                                 to <option>false</option>. It is
 779                                 highly recommended to leave this
 780                                 option enabled for the majority of
 781                                 common units. If set to
 782                                 <option>false</option>, this option
 783                                 does not disable all implicit
 784                                 dependencies, just non-essential
 785                                 ones.</para></listitem>
 786                         </varlistentry>
 787
 788                         <varlistentry>
 789                                 <term><varname>JobTimeoutSec=</varname></term>
 790
 791                                 <listitem><para>When clients are
 792                                 waiting for a job of this unit to
 793                                 complete, time out after the specified
 794                                 time. If this time limit is reached
 795                                 the job will be cancelled, the unit
 796                                 however will not change state or even
 797                                 enter the <literal>failed</literal>
 798                                 mode. This value defaults to 0 (job
 799                                 timeouts disabled), except for device
 800                                 units. NB: this timeout is independent
 801                                 from any unit-specific timeout (for
 802                                 example, the timeout set with
 803                                 <varname>Timeout=</varname> in service
 804                                 units) as the job timeout has no
 805                                 effect on the unit itself, only on the
 806                                 job that might be pending for it. Or
 807                                 in other words: unit-specific timeouts
 808                                 are useful to abort unit state
 809                                 changes, and revert them. The job
 810                                 timeout set with this option however
 811                                 is useful to abort only the job
 812                                 waiting for the unit state to
 813                                 change.</para></listitem>
 814                         </varlistentry>
 815
 816                         <varlistentry>
 817                                 <term><varname>ConditionPathExists=</varname></term>
 818                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 819                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 820                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 821                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 822                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 823                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 824                                 <term><varname>ConditionFileNotEmpty=</varname></term>
 825                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 826                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 827                                 <term><varname>ConditionVirtualization=</varname></term>
 828                                 <term><varname>ConditionSecurity=</varname></term>
 829                                 <term><varname>ConditionCapability=</varname></term>
 830                                 <term><varname>ConditionHost=</varname></term>
 831                                 <term><varname>ConditionACPower=</varname></term>
 832                                 <term><varname>ConditionNull=</varname></term>
 833
 834                                 <listitem><para>Before starting a unit
 835                                 verify that the specified condition is
 836                                 true. If it is not true the starting
 837                                 of the unit will be skipped, however
 838                                 all ordering dependencies of it are
 839                                 still respected. A failing condition
 840                                 will not result in the unit being
 841                                 moved into a failure state. The
 842                                 condition is checked at the time the
 843                                 queued start job is to be
 844                                 executed.</para>
 845
 846                                 <para>With
 847                                 <varname>ConditionPathExists=</varname>
 848                                 a file existence condition is
 849                                 checked before a unit is started. If
 850                                 the specified absolute path name does
 851                                 not exist the condition will
 852                                 fail. If the absolute path name passed
 853                                 to
 854                                 <varname>ConditionPathExists=</varname>
 855                                 is prefixed with an exclamation mark
 856                                 (<literal>!</literal>), the test is negated, and the unit
 857                                 is only started if the path does not
 858                                 exist.</para>
 859
 860                                 <para><varname>ConditionPathExistsGlob=</varname>
 861                                 is similar to
 862                                 <varname>ConditionPathExists=</varname>,
 863                                 but checks for the existence of at
 864                                 least one file or directory matching
 865                                 the specified globbing pattern.</para>
 866
 867                                 <para><varname>ConditionPathIsDirectory=</varname>
 868                                 is similar to
 869                                 <varname>ConditionPathExists=</varname>
 870                                 but verifies whether a certain path
 871                                 exists and is a
 872                                 directory.</para>
 873
 874                                 <para><varname>ConditionPathIsSymbolicLink=</varname>
 875                                 is similar to
 876                                 <varname>ConditionPathExists=</varname>
 877                                 but verifies whether a certain path
 878                                 exists and is a symbolic
 879                                 link.</para>
 880
 881                                 <para><varname>ConditionPathIsMountPoint=</varname>
 882                                 is similar to
 883                                 <varname>ConditionPathExists=</varname>
 884                                 but verifies whether a certain path
 885                                 exists and is a mount
 886                                 point.</para>
 887
 888                                 <para><varname>ConditionPathIsReadWrite=</varname>
 889                                 is similar to
 890                                 <varname>ConditionPathExists=</varname>
 891                                 but verifies whether the underlying
 892                                 file system is readable and writable
 893                                 (i.e. not mounted
 894                                 read-only).</para>
 895
 896                                 <para><varname>ConditionDirectoryNotEmpty=</varname>
 897                                 is similar to
 898                                 <varname>ConditionPathExists=</varname>
 899                                 but verifies whether a certain path
 900                                 exists and is a non-empty
 901                                 directory.</para>
 902
 903                                 <para><varname>ConditionFileNotEmpty=</varname>
 904                                 is similar to
 905                                 <varname>ConditionPathExists=</varname>
 906                                 but verifies whether a certain path
 907                                 exists and refers to a regular file
 908                                 with a non-zero size.</para>
 909
 910                                 <para><varname>ConditionFileIsExecutable=</varname>
 911                                 is similar to
 912                                 <varname>ConditionPathExists=</varname>
 913                                 but verifies whether a certain path
 914                                 exists, is a regular file and marked
 915                                 executable.</para>
 916
 917                                 <para>Similar,
 918                                 <varname>ConditionKernelCommandLine=</varname>
 919                                 may be used to check whether a
 920                                 specific kernel command line option is
 921                                 set (or if prefixed with the
 922                                 exclamation mark unset). The argument
 923                                 must either be a single word, or an
 924                                 assignment (i.e. two words, separated
 925                                 <literal>=</literal>). In the former
 926                                 case the kernel command line is
 927                                 searched for the word appearing as is,
 928                                 or as left hand side of an
 929                                 assignment. In the latter case the
 930                                 exact assignment is looked for with
 931                                 right and left hand side
 932                                 matching.</para>
 933
 934                                 <para><varname>ConditionVirtualization=</varname>
 935                                 may be used to check whether the
 936                                 system is executed in a virtualized
 937                                 environment and optionally test
 938                                 whether it is a specific
 939                                 implementation. Takes either boolean
 940                                 value to check if being executed in
 941                                 any virtualized environment, or one of
 942                                 <varname>vm</varname> and
 943                                 <varname>container</varname> to test
 944                                 against a generic type of
 945                                 virtualization solution, or one of
 946                                 <varname>qemu</varname>,
 947                                 <varname>kvm</varname>,
 948                                 <varname>vmware</varname>,
 949                                 <varname>microsoft</varname>,
 950                                 <varname>oracle</varname>,
 951                                 <varname>xen</varname>,
 952                                 <varname>bochs</varname>,
 953                                 <varname>chroot</varname>,
 954                                 <varname>uml</varname>,
 955                                 <varname>openvz</varname>,
 956                                 <varname>lxc</varname>,
 957                                 <varname>lxc-libvirt</varname>,
 958                                 <varname>systemd-nspawn</varname> to
 959                                 test against a specific
 960                                 implementation. If multiple
 961                                 virtualization technologies are nested
 962                                 only the innermost is considered. The
 963                                 test may be negated by prepending an
 964                                 exclamation mark.</para>
 965
 966                                 <para><varname>ConditionSecurity=</varname>
 967                                 may be used to check whether the given
 968                                 security module is enabled on the
 969                                 system. Currently the recognized values
 970                                 values are <varname>selinux</varname>,
 971                                 <varname>apparmor</varname>,
 972                                 <varname>ima</varname> and
 973                                 <varname>smack</varname>.
 974                                 The test may be negated by prepending
 975                                 an exclamation
 976                                 mark.</para>
 977
 978                                 <para><varname>ConditionCapability=</varname>
 979                                 may be used to check whether the given
 980                                 capability exists in the capability
 981                                 bounding set of the service manager
 982                                 (i.e. this does not check whether
 983                                 capability is actually available in
 984                                 the permitted or effective sets, see
 985                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 986                                 for details). Pass a capability name
 987                                 such as <literal>CAP_MKNOD</literal>,
 988                                 possibly prefixed with an exclamation
 989                                 mark to negate the check.</para>
 990
 991                                 <para><varname>ConditionHost=</varname>
 992                                 may be used to match against the
 993                                 hostname or machine ID of the
 994                                 host. This either takes a hostname
 995                                 string (optionally with shell style
 996                                 globs) which is tested against the
 997                                 locally set hostname as returned by
 998                                 <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 999                                 or a machine ID formatted as string
1000                                 (see
1001                                 <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
1002                                 The test may be negated by prepending
1003                                 an exclamation mark.</para>
1004
1005                                 <para><varname>ConditionACPower=</varname>
1006                                 may be used to check whether the
1007                                 system has AC power, or is exclusively
1008                                 battery powered at the time of
1009                                 activation of the unit. This takes a
1010                                 boolean argument. If set to
1011                                 <varname>true</varname> the condition
1012                                 will hold only if at least one AC
1013                                 connector of the system is connected
1014                                 to a power source, or if no AC
1015                                 connectors are known. Conversely, if
1016                                 set to <varname>false</varname> the
1017                                 condition will hold only if there is
1018                                 at least one AC connector known and
1019                                 all AC connectors are disconnected
1020                                 from a power source.</para>
1021
1022                                 <para>Finally,
1023                                 <varname>ConditionNull=</varname> may
1024                                 be used to add a constant condition
1025                                 check value to the unit. It takes a
1026                                 boolean argument. If set to
1027                                 <varname>false</varname> the condition
1028                                 will always fail, otherwise
1029                                 succeed.</para>
1030
1031                                 <para>If multiple conditions are
1032                                 specified the unit will be executed if
1033                                 all of them apply (i.e. a logical AND
1034                                 is applied). Condition checks can be
1035                                 prefixed with a pipe symbol (|) in
1036                                 which case a condition becomes a
1037                                 triggering condition. If at least one
1038                                 triggering condition is defined for a
1039                                 unit then the unit will be executed if
1040                                 at least one of the triggering
1041                                 conditions apply and all of the
1042                                 non-triggering conditions. If you
1043                                 prefix an argument with the pipe
1044                                 symbol and an exclamation mark the
1045                                 pipe symbol must be passed first, the
1046                                 exclamation second. Except for
1047                                 <varname>ConditionPathIsSymbolicLink=</varname>,
1048                                 all path checks follow symlinks. If
1049                                 any of these options is assigned the
1050                                 empty string the list of conditions is
1051                                 reset completely, all previous
1052                                 condition settings (of any kind) will
1053                                 have no effect.</para></listitem>
1054                         </varlistentry>
1055
1056                         <varlistentry>
1057                                 <term><varname>SourcePath=</varname></term>
1058                                 <listitem><para>A path to a
1059                                 configuration file this unit has been
1060                                 generated from. This is primarily
1061                                 useful for implementation of generator
1062                                 tools that convert configuration from
1063                                 an external configuration file format
1064                                 into native unit files. Thus
1065                                 functionality should not be used in
1066                                 normal units.</para></listitem>
1067                         </varlistentry>
1068                 </variablelist>
1069
1070                 <para>Unit file may include a [Install] section, which
1071                 carries installation information for the unit. This
1072                 section is not interpreted by
1073                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1074                 during runtime. It is used exclusively by the
1075                 <command>enable</command> and
1076                 <command>disable</command> commands of the
1077                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1078                 tool during installation of a unit:</para>
1079
1080                 <variablelist class='unit-directives'>
1081                         <varlistentry>
1082                                 <term><varname>Alias=</varname></term>
1083
1084                                 <listitem><para>Additional names this
1085                                 unit shall be installed under. The
1086                                 names listed here must have the same
1087                                 suffix (i.e. type) as the unit file
1088                                 name. This option may be specified
1089                                 more than once, in which case all
1090                                 listed names are used. At installation
1091                                 time,
1092                                 <command>systemctl enable</command>
1093                                 will create symlinks from these names
1094                                 to the unit filename.</para></listitem>
1095                         </varlistentry>
1096
1097                         <varlistentry>
1098                                 <term><varname>WantedBy=</varname></term>
1099                                 <term><varname>RequiredBy=</varname></term>
1100
1101                                 <listitem><para>A symbolic link is
1102                                 created in the
1103                                 <filename>.wants/</filename> or
1104                                 <filename>.requires/</filename> directory
1105                                 of the listed unit when this unit is
1106                                 activated by <command>systemctl
1107                                 enable</command>.  This has the effect
1108                                 that a dependency of type
1109                                 <varname>Wants=</varname> or
1110                                 <varname>Requires=</varname> is added
1111                                 from the listed unit to the current
1112                                 unit. The primary result is that the
1113                                 current unit will be started when the
1114                                 listed unit is started. See the
1115                                 description of
1116                                 <varname>Wants=</varname> and
1117                                 <varname>Requires=</varname> in the
1118                                 [Unit] section for details.</para>
1119
1120                                 <para><command>WantedBy=foo.service</command>
1121                                 in a service
1122                                 <filename>bar.service</filename> is
1123                                 mostly equivalent to
1124                                 <command>Alias=foo.service.wants/bar.service</command>
1125                                 in the same file. In case of template
1126                                 units, <command>systemctl enable</command>
1127                                 must be called with an instance name, and
1128                                 this instance will be added to the
1129                                 <filename>.wants/</filename> or
1130                                 <filename>.requires/</filename> list
1131                                 of the listed unit.
1132                                 E.g. <command>WantedBy=getty.target</command>
1133                                 in a service
1134                                 <filename>getty@.service</filename>
1135                                 will result in <command>systemctl
1136                                 enable getty@tty2.service</command>
1137                                 creating a
1138                                 <filename>getty.target.wants/getty@tty2.service</filename>
1139                                 link to <filename>getty@.service</filename>.
1140                                 </para></listitem>
1141                         </varlistentry>
1142
1143                         <varlistentry>
1144                                 <term><varname>Also=</varname></term>
1145
1146                                 <listitem><para>Additional units to
1147                                 install/deinstall when this unit is
1148                                 installed/deinstalled. If the user
1149                                 requests installation/deinstallation
1150                                 of a unit with this option configured,
1151                                 <command>systemctl enable</command>
1152                                 and <command>systemctl
1153                                 disable</command> will automatically
1154                                 install/uninstall units listed in this option as
1155                                 well.</para></listitem>
1156                         </varlistentry>
1157                 </variablelist>
1158
1159                 <para>The following specifiers are interpreted in the
1160                 Install section: %n, %N, %p, %i, %U, %u, %m, %H, %b, %v.
1161                 For their meaning see the next section.
1162                 </para>
1163         </refsect1>
1164
1165         <refsect1>
1166                 <title>Specifiers</title>
1167
1168                 <para>Many settings resolve specifiers which may be
1169                 used to write generic unit files referring to runtime
1170                 or unit parameters that are replaced when the unit
1171                 files are loaded. The following specifiers are
1172                 understood:</para>
1173
1174                 <table>
1175                   <title>Specifiers available in unit files</title>
1176                   <tgroup cols='3' align='left' colsep='1' rowsep='1'>
1177                     <colspec colname="spec" />
1178                     <colspec colname="mean" />
1179                     <colspec colname="detail" />
1180                     <thead>
1181                       <row>
1182                         <entry>Specifier</entry>
1183                         <entry>Meaning</entry>
1184                         <entry>Details</entry>
1185                       </row>
1186                     </thead>
1187                     <tbody>
1188                       <row>
1189                         <entry><literal>%n</literal></entry>
1190                         <entry>Full unit name</entry>
1191                         <entry></entry>
1192                       </row>
1193                       <row>
1194                         <entry><literal>%N</literal></entry>
1195                         <entry>Unescaped full unit name</entry>
1196                         <entry></entry>
1197                       </row>
1198                       <row>
1199                         <entry><literal>%p</literal></entry>
1200                         <entry>Prefix name</entry>
1201                         <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>
1202                       </row>
1203                       <row>
1204                         <entry><literal>%P</literal></entry>
1205                         <entry>Unescaped prefix name</entry>
1206                         <entry></entry>
1207                       </row>
1208                       <row>
1209                         <entry><literal>%i</literal></entry>
1210                         <entry>Instance name</entry>
1211                         <entry>For instantiated units: this is the string between the <literal>@</literal> character and the suffix.</entry>
1212                       </row>
1213                       <row>
1214                         <entry><literal>%I</literal></entry>
1215                         <entry>Unescaped instance name</entry>
1216                         <entry></entry>
1217                       </row>
1218                       <row>
1219                         <entry><literal>%f</literal></entry>
1220                         <entry>Unescaped filename</entry>
1221                         <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>
1222                       </row>
1223                       <row>
1224                         <entry><literal>%c</literal></entry>
1225                         <entry>Control group path of the unit</entry>
1226                         <entry></entry>
1227                       </row>
1228                       <row>
1229                         <entry><literal>%r</literal></entry>
1230                         <entry>Root control group path where units are placed.</entry>
1231                         <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>
1232                       </row>
1233                       <row>
1234                         <entry><literal>%R</literal></entry>
1235                         <entry>Parent directory of the control group path where units are placed.</entry>
1236                         <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>
1237                       </row>
1238                       <row>
1239                         <entry><literal>%t</literal></entry>
1240                         <entry>Runtime socket dir</entry>
1241                         <entry>This is either <filename>/run</filename> (for the system manager) or <literal>$XDG_RUNTIME_DIR</literal> (for user managers).</entry>
1242                       </row>
1243                       <row>
1244                         <entry><literal>%u</literal></entry>
1245                         <entry>User name</entry>
1246                         <entry>This is the name 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>%U</literal></entry>
1250                         <entry>User UID</entry>
1251                         <entry>This is the UID of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1252                       </row>
1253                       <row>
1254                         <entry><literal>%h</literal></entry>
1255                         <entry>User home directory</entry>
1256                         <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>
1257                       </row>
1258                       <row>
1259                         <entry><literal>%s</literal></entry>
1260                         <entry>User shell</entry>
1261                         <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>
1262                       </row>
1263                       <row>
1264                         <entry><literal>%m</literal></entry>
1265                         <entry>Machine ID</entry>
1266                         <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>
1267                       </row>
1268                       <row>
1269                         <entry><literal>%b</literal></entry>
1270                         <entry>Boot ID</entry>
1271                         <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
1272                       </row>
1273                       <row>
1274                         <entry><literal>%H</literal></entry>
1275                         <entry>Host name</entry>
1276                         <entry>The hostname of the running system.</entry>
1277                       </row>
1278                       <row>
1279                         <entry><literal>%v</literal></entry>
1280                         <entry>Kernel release</entry>
1281                         <entry>Identical to <command>uname -r</command> output.</entry>
1282                       </row>
1283                       <row>
1284                         <entry><literal>%%</literal></entry>
1285                         <entry>Escaped %</entry>
1286                         <entry>Single percent sign.</entry>
1287                       </row>
1288                     </tbody>
1289                   </tgroup>
1290                 </table>
1291         </refsect1>
1292
1293         <refsect1>
1294                 <title>See Also</title>
1295                 <para>
1296                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1297                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1298                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1299                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1300                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1301                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1302                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1303                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1304                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1305                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1306                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1307                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1308                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1309                         <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1310                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1311                         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1312                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1313                         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1314                         <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1315                 </para>
1316         </refsect1>
1317
1318 </refentry>