man/systemd.unit.xml

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   7
   8 <!--
   9   This file is part of systemd.
  10
  11   Copyright 2010 Lennart Poettering
  12
  13   systemd is free software; you can redistribute it and/or modify it
  14   under the terms of the GNU Lesser General Public License as published by
  15   the Free Software Foundation; either version 2.1 of the License, or
  16   (at your option) any later version.
  17
  18   systemd is distributed in the hope that it will be useful, but
  19   WITHOUT ANY WARRANTY; without even the implied warranty of
  20   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  21   Lesser General Public License for more details.
  22
  23   You should have received a copy of the GNU Lesser General Public License
  24   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  25 -->
  26
  27 <refentry id="systemd.unit">
  28
  29         <refentryinfo>
  30                 <title>systemd.unit</title>
  31                 <productname>systemd</productname>
  32
  33                 <authorgroup>
  34                         <author>
  35                                 <contrib>Developer</contrib>
  36                                 <firstname>Lennart</firstname>
  37                                 <surname>Poettering</surname>
  38                                 <email>lennart@poettering.net</email>
  39                         </author>
  40                 </authorgroup>
  41         </refentryinfo>
  42
  43         <refmeta>
  44                 <refentrytitle>systemd.unit</refentrytitle>
  45                 <manvolnum>5</manvolnum>
  46         </refmeta>
  47
  48         <refnamediv>
  49                 <refname>systemd.unit</refname>
  50                 <refpurpose>Unit configuration</refpurpose>
  51         </refnamediv>
  52
  53         <refsynopsisdiv>
  54                 <para><filename><replaceable>service</replaceable>.service</filename>,
  55                 <filename><replaceable>socket</replaceable>.socket</filename>,
  56                 <filename><replaceable>device</replaceable>.device</filename>,
  57                 <filename><replaceable>mount</replaceable>.mount</filename>,
  58                 <filename><replaceable>automount</replaceable>.automount</filename>,
  59                 <filename><replaceable>swap</replaceable>.swap</filename>,
  60                 <filename><replaceable>target</replaceable>.target</filename>,
  61                 <filename><replaceable>path</replaceable>.path</filename>,
  62                 <filename><replaceable>timer</replaceable>.timer</filename>,
  63                 <filename><replaceable>snapshot</replaceable>.snapshot</filename>,
  64                 <filename><replaceable>slice</replaceable>.slice</filename>,
  65                 <filename><replaceable>scope</replaceable>.scope</filename></para>
  66
  67                 <para><literallayout><filename>/etc/systemd/system/*</filename>
  68 <filename>/run/systemd/system/*</filename>
  69 <filename>/usr/lib/systemd/system/*</filename>
  70 <filename>...</filename>
  71                 </literallayout></para>
  72
  73                 <para><literallayout><filename>$XDG_CONFIG_HOME/systemd/user/*</filename>
  74 <filename>$HOME/.config/systemd/user/*</filename>
  75 <filename>/etc/systemd/user/*</filename>
  76 <filename>/run/systemd/user/*</filename>
  77 <filename>$XDG_DATA_HOME/systemd/user/*</filename>
  78 <filename>$HOME/.local/share/systemd/user/*</filename>
  79 <filename>/usr/lib/systemd/user/*</filename>
  80 <filename>...</filename>
  81                 </literallayout></para>
  82         </refsynopsisdiv>
  83
  84         <refsect1>
  85                 <title>Description</title>
  86
  87                 <para>A unit configuration file encodes information
  88                 about a service, a socket, a device, a mount point, an
  89                 automount point, a swap file or partition, a start-up
  90                 target, a watched file system path, a timer controlled
  91                 and supervised by
  92                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  93                 a temporary system state snapshot, a resource
  94                 management slice or a group of externally created
  95                 processes. The syntax is inspired by <ulink
  96                 url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
  97                 Desktop Entry Specification</ulink>
  98                 <filename>.desktop</filename> files, which are in turn
  99                 inspired by Microsoft Windows
 100                 <filename>.ini</filename> files.</para>
 101
 102                 <para>This man page lists the common configuration
 103                 options of all the unit types. These options need to
 104                 be configured in the [Unit] or [Install]
 105                 sections of the unit files.</para>
 106
 107                 <para>In addition to the generic [Unit] and [Install]
 108                 sections described here, each unit may have a
 109                 type-specific section, e.g. [Service] for a service
 110                 unit. See the respective man pages for more
 111                 information:
 112                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 113                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 114                 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 115                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 116                 <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 117                 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 118                 <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 119                 <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 120                 <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 121                 <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 122                 <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 123                 <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 124                 </para>
 125
 126                 <para>Various settings are allowed to be specified
 127                 more than once, in which case the interpretation
 128                 depends on the setting. Often, multiple settings form
 129                 a list, and setting to an empty value "resets", which
 130                 means that previous assignments are ignored. When this
 131                 is allowed, it is mentioned in the description of the
 132                 setting. Note that using multiple assignments to the
 133                 same value makes the unit file incompatible with
 134                 parsers for the XDG <filename>.desktop</filename> file
 135                 format.</para>
 136
 137                 <para>Unit files are loaded from a set of paths
 138                 determined during compilation, described in the next section.
 139                 </para>
 140
 141                 <para>Unit files may contain additional options on top
 142                 of those listed here. If systemd encounters an unknown
 143                 option, it will write a warning log message but
 144                 continue loading the unit. If an option or section name
 145                 is prefixed with <option>X-</option>, it is ignored
 146                 completely by systemd. Options within an ignored
 147                 section do not need the prefix. Applications may use
 148                 this to include additional information in the unit
 149                 files.</para>
 150
 151                 <para>Boolean arguments used in unit files can be
 152                 written in various formats. For positive settings the
 153                 strings <option>1</option>, <option>yes</option>,
 154                 <option>true</option> and <option>on</option> are
 155                 equivalent. For negative settings, the strings
 156                 <option>0</option>, <option>no</option>,
 157                 <option>false</option> and <option>off</option> are
 158                 equivalent.</para>
 159
 160                 <para>Time span values encoded in unit files can be
 161                 written in various formats. A stand-alone number
 162                 specifies a time in seconds. If suffixed with a time
 163                 unit, the unit is honored. A concatenation of multiple
 164                 values with units is supported, in which case the
 165                 values are added up. Example: "50" refers to 50
 166                 seconds; "2min 200ms" refers to 2 minutes plus 200
 167                 milliseconds, i.e. 120200ms. The following time units
 168                 are understood: s, min, h, d, w, ms, us. For details
 169                 see
 170                 <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 171
 172                 <para>Empty lines and lines starting with # or ; are
 173                 ignored. This may be used for commenting. Lines ending
 174                 in a backslash are concatenated with the following
 175                 line while reading and the backslash is replaced by a
 176                 space character. This may be used to wrap long lines.</para>
 177
 178                 <para>Along with a unit file
 179                 <filename>foo.service</filename>, the directory
 180                 <filename>foo.service.wants/</filename> may exist. All
 181                 unit files symlinked from such a directory are
 182                 implicitly added as dependencies of type
 183                 <varname>Wanted=</varname> to the unit. This is useful
 184                 to hook units into the start-up of other units,
 185                 without having to modify their unit files. For details
 186                 about the semantics of <varname>Wanted=</varname>, see
 187                 below. The preferred way to create symlinks in the
 188                 <filename>.wants/</filename> directory of a unit file
 189                 is with the <command>enable</command> command of the
 190                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 191                 tool which reads information from the [Install]
 192                 section of unit files (see below). A similar
 193                 functionality exists for <varname>Requires=</varname>
 194                 type dependencies as well, the directory suffix is
 195                 <filename>.requires/</filename> in this case.</para>
 196
 197                 <para>Along with a unit file
 198                 <filename>foo.service</filename>, a directory
 199                 <filename>foo.service.d/</filename> may exist. All
 200                 files with the suffix <literal>.conf</literal> from
 201                 this directory will be parsed after the file itself is
 202                 parsed. This is useful to alter or add configuration
 203                 settings to a unit, without having to modify their
 204                 unit files. Make sure that the file that is included
 205                 has the appropriate section headers before any
 206                 directive. Note that for instanced units this logic
 207                 will first look for the instance
 208                 <literal>.d/</literal> subdirectory and read its
 209                 <literal>.conf</literal> files, followed by the
 210                 template <literal>.d/</literal> subdirectory and reads
 211                 its <literal>.conf</literal> files.</para>
 212
 213                 <para>Note that while systemd offers a flexible
 214                 dependency system between units it is recommended to
 215                 use this functionality only sparingly and instead rely
 216                 on techniques such as bus-based or socket-based
 217                 activation which make dependencies implicit, resulting
 218                 in a both simpler and more flexible system.</para>
 219
 220                 <para>Some unit names reflect paths existing in the
 221                 file system namespace. Example: a device unit
 222                 <filename>dev-sda.device</filename> refers to a device
 223                 with the device node <filename noindex='true'>/dev/sda</filename> in
 224                 the file system namespace. If this applies, a special
 225                 way to escape the path name is used, so that the
 226                 result is usable as part of a filename. Basically,
 227                 given a path, "/" is replaced by "-", and all
 228                 unprintable characters and the "-" are replaced by
 229                 C-style "\x20" escapes. The root directory "/" is
 230                 encoded as single dash, while otherwise the initial
 231                 and ending "/" is removed from all paths during
 232                 transformation. This escaping is reversible.</para>
 233
 234                 <para>Optionally, units may be instantiated from a
 235                 template file at runtime. This allows creation of
 236                 multiple units from a single configuration file. If
 237                 systemd looks for a unit configuration file, it will
 238                 first search for the literal unit name in the
 239                 file system. If that yields no success and the unit
 240                 name contains an <literal>@</literal> character, systemd will look for a
 241                 unit template that shares the same name but with the
 242                 instance string (i.e. the part between the <literal>@</literal> character
 243                 and the suffix) removed. Example: if a service
 244                 <filename>getty@tty3.service</filename> is requested
 245                 and no file by that name is found, systemd will look
 246                 for <filename>getty@.service</filename> and
 247                 instantiate a service from that configuration file if
 248                 it is found.</para>
 249
 250                 <para>To refer to the instance string from
 251                 within the configuration file you may use the special
 252                 <literal>%i</literal> specifier in many of the
 253                 configuration options. See below for details.</para>
 254
 255                 <para>If a unit file is empty (i.e. has the file size
 256                 0) or is symlinked to <filename>/dev/null</filename>,
 257                 its configuration will not be loaded and it appears
 258                 with a load state of <literal>masked</literal>, and
 259                 cannot be activated. Use this as an effective way to
 260                 fully disable a unit, making it impossible to start it
 261                 even manually.</para>
 262
 263                 <para>The unit file format is covered by the
 264                 <ulink
 265                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 266                 Stability Promise</ulink>.</para>
 267
 268         </refsect1>
 269
 270         <refsect1>
 271                 <title>Unit Load Path</title>
 272
 273                 <para>Unit files are loaded from a set of paths
 274                 determined during compilation, described in the two
 275                 tables below. Unit files found in directories listed
 276                 earlier override files with the same name in
 277                 directories lower in the list.</para>
 278
 279                 <para>When systemd is running in user mode
 280                 (<option>--user</option>) and the variable
 281                 <varname>$SYSTEMD_UNIT_PATH</varname> is set, this
 282                 contents of this variable overrides the unit load
 283                 path. If <varname>$SYSTEMD_UNIT_PATH</varname> ends
 284                 with an empty component (<literal>:</literal>), the
 285                 usual unit load path will be appended to the contents
 286                 of the variable.</para>
 287
 288                 <table>
 289                   <title>
 290                     Load path when running in system mode (<option>--system</option>).
 291                   </title>
 292
 293                   <tgroup cols='2'>
 294                     <colspec colname='path' />
 295                     <colspec colname='expl' />
 296                     <thead>
 297                       <row>
 298                         <entry>Path</entry>
 299                         <entry>Description</entry>
 300                       </row>
 301                     </thead>
 302                     <tbody>
 303                       <row>
 304                         <entry><filename>/etc/systemd/system</filename></entry>
 305                         <entry>Local configuration</entry>
 306                       </row>
 307                       <row>
 308                         <entry><filename>/run/systemd/system</filename></entry>
 309                         <entry>Runtime units</entry>
 310                       </row>
 311                       <row>
 312                         <entry><filename>/usr/lib/systemd/system</filename></entry>
 313                         <entry>Units of installed packages</entry>
 314                       </row>
 315                     </tbody>
 316                   </tgroup>
 317                 </table>
 318
 319                 <table>
 320                   <title>
 321                     Load path when running in user mode (<option>--user</option>).
 322                   </title>
 323
 324                   <tgroup cols='2'>
 325                     <colspec colname='path' />
 326                     <colspec colname='expl' />
 327                     <thead>
 328                       <row>
 329                         <entry>Path</entry>
 330                         <entry>Description</entry>
 331                       </row>
 332                     </thead>
 333                     <tbody>
 334                       <row>
 335                         <entry><filename>$XDG_CONFIG_HOME/systemd/user</filename></entry>
 336                         <entry>User configuration (only used when $XDG_CONFIG_HOME is set)</entry>
 337                       </row>
 338                       <row>
 339                         <entry><filename>$HOME/.config/systemd/user</filename></entry>
 340                         <entry>User configuration (only used when $XDG_CONFIG_HOME is not set)</entry>
 341                       </row>
 342                       <row>
 343                         <entry><filename>/etc/systemd/user</filename></entry>
 344                         <entry>Local configuration</entry>
 345                       </row>
 346                       <row>
 347                         <entry><filename>/run/systemd/user</filename></entry>
 348                         <entry>Runtime units</entry>
 349                       </row>
 350                       <row>
 351                         <entry><filename>$XDG_DATA_HOME/systemd/user</filename></entry>
 352                         <entry>Units of packages that have been installed in the home directory (only used when $XDG_DATA_HOME is set)</entry>
 353                       </row>
 354                       <row>
 355                         <entry><filename>$HOME/.local/share/systemd/user</filename></entry>
 356                         <entry>Units of packages that have been installed in the home directory (only used when $XDG_DATA_HOME is not set)</entry>
 357                       </row>
 358                       <row>
 359                         <entry><filename>/usr/lib/systemd/user</filename></entry>
 360                         <entry>Units of packages that have been installed system-wide</entry>
 361                       </row>
 362                     </tbody>
 363                   </tgroup>
 364                 </table>
 365
 366                 <para>Additional units might be loaded into systemd
 367                 ("linked") from directories not on the unit load
 368                 path. See the <command>link</command> command for
 369                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>. Also,
 370                 some units are dynamically created via generators
 371                 <ulink
 372                 url="http://www.freedesktop.org/wiki/Software/systemd/Generators/">Generators</ulink>.
 373                 </para>
 374         </refsect1>
 375
 376         <refsect1>
 377                 <title>[Unit] Section Options</title>
 378
 379                 <para>Unit file may include a [Unit] section, which
 380                 carries generic information about the unit that is not
 381                 dependent on the type of unit:</para>
 382
 383                 <variablelist class='unit-directives'>
 384
 385                         <varlistentry>
 386                                 <term><varname>Description=</varname></term>
 387                                 <listitem><para>A free-form string
 388                                 describing the unit. This is intended
 389                                 for use in UIs to show descriptive
 390                                 information along with the unit
 391                                 name. The description should contain a name
 392                                 that means something to the end user.
 393                                 <literal>Apache2 Web Server</literal> is a good
 394                                 example. Bad examples are
 395                                 <literal>high-performance light-weight HTTP
 396                                 server</literal> (too generic) or
 397                                 <literal>Apache2</literal> (too specific and
 398                                 meaningless for people who do not know
 399                                 Apache).</para></listitem>
 400                         </varlistentry>
 401
 402                         <varlistentry>
 403                                 <term><varname>Documentation=</varname></term>
 404                                 <listitem><para>A space-separated list
 405                                 of URIs referencing documentation for
 406                                 this unit or its
 407                                 configuration. Accepted are only URIs
 408                                 of the types
 409                                 <literal>http://</literal>,
 410                                 <literal>https://</literal>,
 411                                 <literal>file:</literal>,
 412                                 <literal>info:</literal>,
 413                                 <literal>man:</literal>. For more
 414                                 information about the syntax of these
 415                                 URIs, see
 416                                 <citerefentry project='man-pages'><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
 417                                 URIs should be listed in order of
 418                                 relevance, starting with the most
 419                                 relevant. It is a good idea to first
 420                                 reference documentation that explains
 421                                 what the unit's purpose is, followed
 422                                 by how it is configured, followed by
 423                                 any other related documentation. This
 424                                 option may be specified more than once,
 425                                 in which case the specified list of
 426                                 URIs is merged. If the empty string is
 427                                 assigned to this option, the list is
 428                                 reset and all prior assignments will
 429                                 have no effect.</para></listitem>
 430                         </varlistentry>
 431
 432                         <varlistentry>
 433                                 <term><varname>Requires=</varname></term>
 434
 435                                 <listitem><para>Configures requirement
 436                                 dependencies on other units. If this
 437                                 unit gets activated, the units listed
 438                                 here will be activated as well. If one
 439                                 of the other units gets deactivated or
 440                                 its activation fails, this unit will
 441                                 be deactivated. This option may be
 442                                 specified more than once or multiple
 443                                 space-separated units may be specified
 444                                 in one option in which case
 445                                 requirement dependencies for all
 446                                 listed names will be created. Note
 447                                 that requirement dependencies do not
 448                                 influence the order in which services
 449                                 are started or stopped. This has to be
 450                                 configured independently with the
 451                                 <varname>After=</varname> or
 452                                 <varname>Before=</varname> options. If
 453                                 a unit
 454                                 <filename>foo.service</filename>
 455                                 requires a unit
 456                                 <filename>bar.service</filename> as
 457                                 configured with
 458                                 <varname>Requires=</varname> and no
 459                                 ordering is configured with
 460                                 <varname>After=</varname> or
 461                                 <varname>Before=</varname>, then both
 462                                 units will be started simultaneously
 463                                 and without any delay between them if
 464                                 <filename>foo.service</filename> is
 465                                 activated. Often it is a better choice
 466                                 to use <varname>Wants=</varname>
 467                                 instead of
 468                                 <varname>Requires=</varname> in order
 469                                 to achieve a system that is more
 470                                 robust when dealing with failing
 471                                 services.</para>
 472
 473                                 <para>Note that dependencies of this
 474                                 type may also be configured outside of
 475                                 the unit configuration file by
 476                                 adding a symlink to a
 477                                 <filename>.requires/</filename> directory
 478                                 accompanying the unit file. For
 479                                 details see above.</para></listitem>
 480                         </varlistentry>
 481
 482                         <varlistentry>
 483                                 <term><varname>RequiresOverridable=</varname></term>
 484
 485                                 <listitem><para>Similar to
 486                                 <varname>Requires=</varname>.
 487                                 Dependencies listed in
 488                                 <varname>RequiresOverridable=</varname>
 489                                 which cannot be fulfilled or fail to
 490                                 start are ignored if the startup was
 491                                 explicitly requested by the user. If
 492                                 the start-up was pulled in indirectly
 493                                 by some dependency or automatic
 494                                 start-up of units that is not
 495                                 requested by the user, this dependency
 496                                 must be fulfilled and otherwise the
 497                                 transaction fails. Hence, this option
 498                                 may be used to configure dependencies
 499                                 that are normally honored unless the
 500                                 user explicitly starts up the unit, in
 501                                 which case whether they failed or not
 502                                 is irrelevant.</para></listitem>
 503
 504                         </varlistentry>
 505                         <varlistentry>
 506                                 <term><varname>Requisite=</varname></term>
 507                                 <term><varname>RequisiteOverridable=</varname></term>
 508
 509                                 <listitem><para>Similar to
 510                                 <varname>Requires=</varname> and
 511                                 <varname>RequiresOverridable=</varname>,
 512                                 respectively. However, if the units
 513                                 listed here are not started already,
 514                                 they will not be started and the
 515                                 transaction will fail immediately.
 516                                 </para></listitem>
 517                         </varlistentry>
 518
 519                         <varlistentry>
 520                                 <term><varname>Wants=</varname></term>
 521
 522                                 <listitem><para>A weaker version of
 523                                 <varname>Requires=</varname>. Units
 524                                 listed in this option will be started
 525                                 if the configuring unit is. However,
 526                                 if the listed units fail to start
 527                                 or cannot be added to the transaction,
 528                                 this has no impact on the validity of
 529                                 the transaction as a whole. This is
 530                                 the recommended way to hook start-up
 531                                 of one unit to the start-up of another
 532                                 unit.</para>
 533
 534                                 <para>Note that dependencies of this
 535                                 type may also be configured outside of
 536                                 the unit configuration file by adding
 537                                 symlinks to a
 538                                 <filename>.wants/</filename> directory
 539                                 accompanying the unit file. For
 540                                 details, see above.</para></listitem>
 541                         </varlistentry>
 542
 543                         <varlistentry>
 544                                 <term><varname>BindsTo=</varname></term>
 545
 546                                 <listitem><para>Configures requirement
 547                                 dependencies, very similar in style to
 548                                 <varname>Requires=</varname>, however
 549                                 in addition to this behavior, it also
 550                                 declares that this unit is stopped
 551                                 when any of the units listed suddenly
 552                                 disappears. Units can suddenly,
 553                                 unexpectedly disappear if a service
 554                                 terminates on its own choice, a device
 555                                 is unplugged or a mount point
 556                                 unmounted without involvement of
 557                                 systemd.</para></listitem>
 558                         </varlistentry>
 559
 560                         <varlistentry>
 561                                 <term><varname>PartOf=</varname></term>
 562
 563                                 <listitem><para>Configures dependencies
 564                                 similar to <varname>Requires=</varname>,
 565                                 but limited to stopping and restarting
 566                                 of units. When systemd stops or restarts
 567                                 the units listed here, the action is
 568                                 propagated to this unit.
 569                                 Note that this is a one-way dependency —
 570                                 changes to this unit do not affect the
 571                                 listed units.
 572                                 </para></listitem>
 573                         </varlistentry>
 574
 575                         <varlistentry>
 576                                 <term><varname>Conflicts=</varname></term>
 577
 578                                 <listitem><para>A space-separated list
 579                                 of unit names. Configures negative
 580                                 requirement dependencies. If a unit
 581                                 has a <varname>Conflicts=</varname>
 582                                 setting on another unit, starting the
 583                                 former will stop the latter and vice
 584                                 versa. Note that this setting is
 585                                 independent of and orthogonal to the
 586                                 <varname>After=</varname> and
 587                                 <varname>Before=</varname> ordering
 588                                 dependencies.</para>
 589
 590                                 <para>If a unit A that conflicts with
 591                                 a unit B is scheduled to be started at
 592                                 the same time as B, the transaction
 593                                 will either fail (in case both are
 594                                 required part of the transaction) or
 595                                 be modified to be fixed (in case one
 596                                 or both jobs are not a required part
 597                                 of the transaction). In the latter
 598                                 case, the job that is not the required
 599                                 will be removed, or in case both are
 600                                 not required, the unit that conflicts
 601                                 will be started and the unit that is
 602                                 conflicted is
 603                                 stopped.</para></listitem>
 604                         </varlistentry>
 605
 606                         <varlistentry>
 607                                 <term><varname>Before=</varname></term>
 608                                 <term><varname>After=</varname></term>
 609
 610                                 <listitem><para>A space-separated list
 611                                 of unit names. Configures ordering
 612                                 dependencies between units. If a unit
 613                                 <filename>foo.service</filename>
 614                                 contains a setting
 615                                 <option>Before=bar.service</option>
 616                                 and both units are being started,
 617                                 <filename>bar.service</filename>'s
 618                                 start-up is delayed until
 619                                 <filename>foo.service</filename> is
 620                                 started up. Note that this setting is
 621                                 independent of and orthogonal to the
 622                                 requirement dependencies as configured
 623                                 by <varname>Requires=</varname>. It is
 624                                 a common pattern to include a unit
 625                                 name in both the
 626                                 <varname>After=</varname> and
 627                                 <varname>Requires=</varname> option, in
 628                                 which case the unit listed will be
 629                                 started before the unit that is
 630                                 configured with these options. This
 631                                 option may be specified more than
 632                                 once, in which case ordering
 633                                 dependencies for all listed names are
 634                                 created. <varname>After=</varname> is
 635                                 the inverse of
 636                                 <varname>Before=</varname>, i.e. while
 637                                 <varname>After=</varname> ensures that
 638                                 the configured unit is started after
 639                                 the listed unit finished starting up,
 640                                 <varname>Before=</varname> ensures the
 641                                 opposite, i.e.  that the configured
 642                                 unit is fully started up before the
 643                                 listed unit is started. Note that when
 644                                 two units with an ordering dependency
 645                                 between them are shut down, the
 646                                 inverse of the start-up order is
 647                                 applied. i.e. if a unit is configured
 648                                 with <varname>After=</varname> on
 649                                 another unit, the former is stopped
 650                                 before the latter if both are shut
 651                                 down. If one unit with an ordering
 652                                 dependency on another unit is shut
 653                                 down while the latter is started up,
 654                                 the shut down is ordered before the
 655                                 start-up regardless of whether the
 656                                 ordering dependency is actually of
 657                                 type <varname>After=</varname> or
 658                                 <varname>Before=</varname>. If two
 659                                 units have no ordering dependencies
 660                                 between them, they are shut down or
 661                                 started up simultaneously, and no
 662                                 ordering takes
 663                                 place. </para></listitem>
 664                         </varlistentry>
 665
 666                         <varlistentry>
 667                                 <term><varname>OnFailure=</varname></term>
 668
 669                                 <listitem><para>A space-separated list
 670                                 of one or more units that are
 671                                 activated when this unit enters the
 672                                 <literal>failed</literal>
 673                                 state.</para></listitem>
 674                         </varlistentry>
 675
 676                         <varlistentry>
 677                                 <term><varname>PropagatesReloadTo=</varname></term>
 678                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 679
 680                                 <listitem><para>A space-separated list
 681                                 of one or more units where reload
 682                                 requests on this unit will be
 683                                 propagated to, or reload requests on
 684                                 the other unit will be propagated to
 685                                 this unit, respectively. Issuing a
 686                                 reload request on a unit will
 687                                 automatically also enqueue a reload
 688                                 request on all units that the reload
 689                                 request shall be propagated to via
 690                                 these two settings.</para></listitem>
 691                         </varlistentry>
 692
 693                         <varlistentry>
 694                                 <term><varname>JoinsNamespaceOf=</varname></term>
 695
 696                                 <listitem><para>For units that start
 697                                 processes (such as service units),
 698                                 lists one or more other units whose
 699                                 network and/or temporary file
 700                                 namespace to join. This only applies
 701                                 to unit types which support the
 702                                 <varname>PrivateNetwork=</varname> and
 703                                 <varname>PrivateTmp=</varname>
 704                                 directives (see
 705                                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 706                                 for details). If a unit that has this
 707                                 setting set is started, its processes
 708                                 will see the same
 709                                 <filename>/tmp</filename>,
 710                                 <filename>/tmp/var</filename> and
 711                                 network namespace as one listed unit
 712                                 that is started. If multiple listed
 713                                 units are already started, it is not
 714                                 defined which namespace is
 715                                 joined. Note that this setting only
 716                                 has an effect if
 717                                 <varname>PrivateNetwork=</varname>
 718                                 and/or <varname>PrivateTmp=</varname>
 719                                 is enabled for both the unit that
 720                                 joins the namespace and the unit whose
 721                                 namespace is joined.</para></listitem>
 722                         </varlistentry>
 723
 724                         <varlistentry>
 725                                 <term><varname>RequiresMountsFor=</varname></term>
 726
 727                                 <listitem><para>Takes a
 728                                 space-separated list of absolute
 729                                 paths. Automatically adds dependencies
 730                                 of type <varname>Requires=</varname>
 731                                 and <varname>After=</varname> for all
 732                                 mount units required to access the
 733                                 specified path.</para>
 734
 735                                 <para>Mount points marked with
 736                                 <option>noauto</option> are not
 737                                 mounted automatically and will be
 738                                 ignored for the purposes of this
 739                                 option. If such a mount should be a
 740                                 requirement for this unit,
 741                                 direct dependencies on the mount
 742                                 units may be added
 743                                 (<varname>Requires=</varname> and
 744                                 <varname>After=</varname> or
 745                                 some other combination).
 746                                 </para></listitem>
 747                         </varlistentry>
 748
 749                         <varlistentry>
 750                                 <term><varname>OnFailureJobMode=</varname></term>
 751
 752                                 <listitem><para>Takes a value of
 753                                 <literal>fail</literal>,
 754                                 <literal>replace</literal>,
 755                                 <literal>replace-irreversibly</literal>,
 756                                 <literal>isolate</literal>,
 757                                 <literal>flush</literal>,
 758                                 <literal>ignore-dependencies</literal>
 759                                 or
 760                                 <literal>ignore-requirements</literal>. Defaults
 761                                 to
 762                                 <literal>replace</literal>. Specifies
 763                                 how the units listed in
 764                                 <varname>OnFailure=</varname> will be
 765                                 enqueued. See
 766                                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
 767                                 <option>--job-mode=</option> option
 768                                 for details on the possible values. If
 769                                 this is set to
 770                                 <literal>isolate</literal>, only a
 771                                 single unit may be listed in
 772                                 <varname>OnFailure=</varname>..</para></listitem>
 773                         </varlistentry>
 774
 775                         <varlistentry>
 776                                 <term><varname>IgnoreOnIsolate=</varname></term>
 777
 778                                 <listitem><para>Takes a boolean
 779                                 argument. If <option>true</option>,
 780                                 this unit will not be stopped when
 781                                 isolating another unit. Defaults to
 782                                 <option>false</option>.</para></listitem>
 783                         </varlistentry>
 784
 785                         <varlistentry>
 786                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 787
 788                                 <listitem><para>Takes a boolean
 789                                 argument. If <option>true</option>,
 790                                 this unit will not be included in
 791                                 snapshots. Defaults to
 792                                 <option>true</option> for device and
 793                                 snapshot units, <option>false</option>
 794                                 for the others.</para></listitem>
 795                         </varlistentry>
 796
 797                         <varlistentry>
 798                                 <term><varname>StopWhenUnneeded=</varname></term>
 799
 800                                 <listitem><para>Takes a boolean
 801                                 argument. If <option>true</option>,
 802                                 this unit will be stopped when it is
 803                                 no longer used. Note that in order to
 804                                 minimize the work to be executed,
 805                                 systemd will not stop units by default
 806                                 unless they are conflicting with other
 807                                 units, or the user explicitly
 808                                 requested their shut down. If this
 809                                 option is set, a unit will be
 810                                 automatically cleaned up if no other
 811                                 active unit requires it. Defaults to
 812                                 <option>false</option>.</para></listitem>
 813                         </varlistentry>
 814
 815                         <varlistentry>
 816                                 <term><varname>RefuseManualStart=</varname></term>
 817                                 <term><varname>RefuseManualStop=</varname></term>
 818
 819                                 <listitem><para>Takes a boolean
 820                                 argument. If <option>true</option>,
 821                                 this unit can only be activated
 822                                 or deactivated indirectly. In
 823                                 this case, explicit start-up
 824                                 or termination requested by the
 825                                 user is denied, however if it is
 826                                 started or stopped as a
 827                                 dependency of another unit, start-up
 828                                 or termination will succeed. This
 829                                 is mostly a safety feature to ensure
 830                                 that the user does not accidentally
 831                                 activate units that are not intended
 832                                 to be activated explicitly, and not
 833                                 accidentally deactivate units that are
 834                                 not intended to be deactivated.
 835                                 These options default to
 836                                 <option>false</option>.</para></listitem>
 837                         </varlistentry>
 838
 839                         <varlistentry>
 840                                 <term><varname>AllowIsolate=</varname></term>
 841
 842                                 <listitem><para>Takes a boolean
 843                                 argument. If <option>true</option>,
 844                                 this unit may be used with the
 845                                 <command>systemctl isolate</command>
 846                                 command. Otherwise, this will be
 847                                 refused. It probably is a good idea to
 848                                 leave this disabled except for target
 849                                 units that shall be used similar to
 850                                 runlevels in SysV init systems, just
 851                                 as a precaution to avoid unusable
 852                                 system states. This option defaults to
 853                                 <option>false</option>.</para></listitem>
 854                         </varlistentry>
 855
 856                         <varlistentry>
 857                                 <term><varname>DefaultDependencies=</varname></term>
 858
 859                                 <listitem><para>Takes a boolean
 860                                 argument. If <option>true</option>,
 861                                 (the default), a few default
 862                                 dependencies will implicitly be
 863                                 created for the unit. The actual
 864                                 dependencies created depend on the
 865                                 unit type. For example, for service
 866                                 units, these dependencies ensure that
 867                                 the service is started only after
 868                                 basic system initialization is
 869                                 completed and is properly terminated on
 870                                 system shutdown. See the respective
 871                                 man pages for details. Generally, only
 872                                 services involved with early boot or
 873                                 late shutdown should set this option
 874                                 to <option>false</option>. It is
 875                                 highly recommended to leave this
 876                                 option enabled for the majority of
 877                                 common units. If set to
 878                                 <option>false</option>, this option
 879                                 does not disable all implicit
 880                                 dependencies, just non-essential
 881                                 ones.</para></listitem>
 882                         </varlistentry>
 883
 884                         <varlistentry>
 885                                 <term><varname>JobTimeoutSec=</varname></term>
 886
 887                                 <listitem><para>When clients are
 888                                 waiting for a job of this unit to
 889                                 complete, time out after the specified
 890                                 time. If this time limit is reached,
 891                                 the job will be cancelled, the unit
 892                                 however will not change state or even
 893                                 enter the <literal>failed</literal>
 894                                 mode. This value defaults to 0 (job
 895                                 timeouts disabled), except for device
 896                                 units. NB: this timeout is independent
 897                                 from any unit-specific timeout (for
 898                                 example, the timeout set with
 899                                 <varname>Timeout=</varname> in service
 900                                 units) as the job timeout has no
 901                                 effect on the unit itself, only on the
 902                                 job that might be pending for it. Or
 903                                 in other words: unit-specific timeouts
 904                                 are useful to abort unit state
 905                                 changes, and revert them. The job
 906                                 timeout set with this option however
 907                                 is useful to abort only the job
 908                                 waiting for the unit state to
 909                                 change.</para></listitem>
 910                         </varlistentry>
 911
 912                         <varlistentry>
 913                                 <term><varname>ConditionArchitecture=</varname></term>
 914                                 <term><varname>ConditionVirtualization=</varname></term>
 915                                 <term><varname>ConditionHost=</varname></term>
 916                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 917                                 <term><varname>ConditionSecurity=</varname></term>
 918                                 <term><varname>ConditionCapability=</varname></term>
 919                                 <term><varname>ConditionACPower=</varname></term>
 920                                 <term><varname>ConditionNeedsUpdate=</varname></term>
 921                                 <term><varname>ConditionFirstBoot=</varname></term>
 922                                 <term><varname>ConditionPathExists=</varname></term>
 923                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 924                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 925                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 926                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 927                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 928                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 929                                 <term><varname>ConditionFileNotEmpty=</varname></term>
 930                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 931                                 <term><varname>ConditionNull=</varname></term>
 932
 933                                 <listitem><para>Before starting a unit
 934                                 verify that the specified condition is
 935                                 true. If it is not true, the starting
 936                                 of the unit will be skipped, however
 937                                 all ordering dependencies of it are
 938                                 still respected. A failing condition
 939                                 will not result in the unit being
 940                                 moved into a failure state. The
 941                                 condition is checked at the time the
 942                                 queued start job is to be
 943                                 executed.</para>
 944
 945                                 <para><varname>ConditionArchitecture=</varname>
 946                                 may be used to check whether the
 947                                 system is running on a specific
 948                                 architecture. Takes one of
 949                                 <varname>x86</varname>,
 950                                 <varname>x86-64</varname>,
 951                                 <varname>ppc</varname>,
 952                                 <varname>ppc-le</varname>,
 953                                 <varname>ppc64</varname>,
 954                                 <varname>ppc64-le</varname>,
 955                                 <varname>ia64</varname>,
 956                                 <varname>parisc</varname>,
 957                                 <varname>parisc64</varname>,
 958                                 <varname>s390</varname>,
 959                                 <varname>s390x</varname>,
 960                                 <varname>sparc</varname>,
 961                                 <varname>sparc64</varname>,
 962                                 <varname>mips</varname>,
 963                                 <varname>mips-le</varname>,
 964                                 <varname>mips64</varname>,
 965                                 <varname>mips64-le</varname>,
 966                                 <varname>alpha</varname>,
 967                                 <varname>arm</varname>,
 968                                 <varname>arm-be</varname>,
 969                                 <varname>arm64</varname>,
 970                                 <varname>arm64-be</varname>,
 971                                 <varname>sh</varname>,
 972                                 <varname>sh64</varname>,
 973                                 <varname>m86k</varname>,
 974                                 <varname>tilegx</varname>,
 975                                 <varname>cris</varname> to test
 976                                 against a specific architecture. The
 977                                 architecture is determined from the
 978                                 information returned by
 979                                 <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 980                                 and is thus subject to
 981                                 <citerefentry><refentrytitle>personality</refentrytitle><manvolnum>2</manvolnum></citerefentry>. Note
 982                                 that a <varname>Personality=</varname>
 983                                 setting in the same unit file has no
 984                                 effect on this condition. A special
 985                                 architecture name
 986                                 <varname>native</varname> is mapped to
 987                                 the architecture the system manager
 988                                 itself is compiled for. The test may
 989                                 be negated by prepending an
 990                                 exclamation mark.</para>
 991
 992                                 <para><varname>ConditionVirtualization=</varname>
 993                                 may be used to check whether the
 994                                 system is executed in a virtualized
 995                                 environment and optionally test
 996                                 whether it is a specific
 997                                 implementation. Takes either boolean
 998                                 value to check if being executed in
 999                                 any virtualized environment, or one of
1000                                 <varname>vm</varname> and
1001                                 <varname>container</varname> to test
1002                                 against a generic type of
1003                                 virtualization solution, or one of
1004                                 <varname>qemu</varname>,
1005                                 <varname>kvm</varname>,
1006                                 <varname>zvm</varname>,
1007                                 <varname>vmware</varname>,
1008                                 <varname>microsoft</varname>,
1009                                 <varname>oracle</varname>,
1010                                 <varname>xen</varname>,
1011                                 <varname>bochs</varname>,
1012                                 <varname>uml</varname>,
1013                                 <varname>openvz</varname>,
1014                                 <varname>lxc</varname>,
1015                                 <varname>lxc-libvirt</varname>,
1016                                 <varname>systemd-nspawn</varname> to
1017                                 test against a specific
1018                                 implementation. If multiple
1019                                 virtualization technologies are nested,
1020                                 only the innermost is considered. The
1021                                 test may be negated by prepending an
1022                                 exclamation mark.</para>
1023
1024                                 <para><varname>ConditionHost=</varname>
1025                                 may be used to match against the
1026                                 hostname or machine ID of the
1027                                 host. This either takes a hostname
1028                                 string (optionally with shell style
1029                                 globs) which is tested against the
1030                                 locally set hostname as returned by
1031                                 <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
1032                                 or a machine ID formatted as string
1033                                 (see
1034                                 <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
1035                                 The test may be negated by prepending
1036                                 an exclamation mark.</para>
1037
1038                                 <para><varname>ConditionKernelCommandLine=</varname>
1039                                 may be used to check whether a
1040                                 specific kernel command line option is
1041                                 set (or if prefixed with the
1042                                 exclamation mark unset). The argument
1043                                 must either be a single word, or an
1044                                 assignment (i.e. two words, separated
1045                                 <literal>=</literal>). In the former
1046                                 case the kernel command line is
1047                                 searched for the word appearing as is,
1048                                 or as left hand side of an
1049                                 assignment. In the latter case, the
1050                                 exact assignment is looked for with
1051                                 right and left hand side
1052                                 matching.</para>
1053
1054                                 <para><varname>ConditionSecurity=</varname>
1055                                 may be used to check whether the given
1056                                 security module is enabled on the
1057                                 system. Currently the recognized values
1058                                 values are <varname>selinux</varname>,
1059                                 <varname>apparmor</varname>,
1060                                 <varname>ima</varname> and
1061                                 <varname>smack</varname>.
1062                                 The test may be negated by prepending
1063                                 an exclamation
1064                                 mark.</para>
1065
1066                                 <para><varname>ConditionCapability=</varname>
1067                                 may be used to check whether the given
1068                                 capability exists in the capability
1069                                 bounding set of the service manager
1070                                 (i.e. this does not check whether
1071                                 capability is actually available in
1072                                 the permitted or effective sets, see
1073                                 <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1074                                 for details). Pass a capability name
1075                                 such as <literal>CAP_MKNOD</literal>,
1076                                 possibly prefixed with an exclamation
1077                                 mark to negate the check.</para>
1078
1079                                 <para><varname>ConditionACPower=</varname>
1080                                 may be used to check whether the
1081                                 system has AC power, or is exclusively
1082                                 battery powered at the time of
1083                                 activation of the unit. This takes a
1084                                 boolean argument. If set to
1085                                 <varname>true</varname>, the condition
1086                                 will hold only if at least one AC
1087                                 connector of the system is connected
1088                                 to a power source, or if no AC
1089                                 connectors are known. Conversely, if
1090                                 set to <varname>false</varname>, the
1091                                 condition will hold only if there is
1092                                 at least one AC connector known and
1093                                 all AC connectors are disconnected
1094                                 from a power source.</para>
1095
1096                                 <para><varname>ConditionNeedsUpdate=</varname>
1097                                 takes one of <filename>/var</filename>
1098                                 or <filename>/etc</filename> as
1099                                 argument, possibly prefixed with a
1100                                 <literal>!</literal> (for inverting
1101                                 the condition). This condition may be
1102                                 used to conditionalize units on
1103                                 whether the specified directory
1104                                 requires an update because
1105                                 <filename>/usr</filename>'s
1106                                 modification time is newer than the
1107                                 stamp file
1108                                 <filename>.updated</filename> in the
1109                                 specified directory. This is useful to
1110                                 implement offline updates of the
1111                                 vendor operating system resources in
1112                                 <filename>/usr</filename> that require
1113                                 updating of <filename>/etc</filename>
1114                                 or <filename>/var</filename> on the
1115                                 next following boot. Units making use
1116                                 of this condition should order
1117                                 themselves before
1118                                 <citerefentry><refentrytitle>systemd-update-done.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1119                                 to make sure they run before the stamp
1120                                 files's modification time gets reset
1121                                 indicating a completed update.</para>
1122
1123                                 <para><varname>ConditionFirstBoot=</varname>
1124                                 takes a boolean argument. This
1125                                 condition may be used to
1126                                 conditionalize units on whether the
1127                                 system is booting up with an
1128                                 unpopulated <filename>/etc</filename>
1129                                 directory. This may be used to
1130                                 populate <filename>/etc</filename> on
1131                                 the first boot after factory reset, or
1132                                 when a new system instances boots up
1133                                 for the first time.</para>
1134
1135                                 <para>With
1136                                 <varname>ConditionPathExists=</varname>
1137                                 a file existence condition is
1138                                 checked before a unit is started. If
1139                                 the specified absolute path name does
1140                                 not exist, the condition will
1141                                 fail. If the absolute path name passed
1142                                 to
1143                                 <varname>ConditionPathExists=</varname>
1144                                 is prefixed with an exclamation mark
1145                                 (<literal>!</literal>), the test is negated, and the unit
1146                                 is only started if the path does not
1147                                 exist.</para>
1148
1149                                 <para><varname>ConditionPathExistsGlob=</varname>
1150                                 is similar to
1151                                 <varname>ConditionPathExists=</varname>,
1152                                 but checks for the existence of at
1153                                 least one file or directory matching
1154                                 the specified globbing pattern.</para>
1155
1156                                 <para><varname>ConditionPathIsDirectory=</varname>
1157                                 is similar to
1158                                 <varname>ConditionPathExists=</varname>
1159                                 but verifies whether a certain path
1160                                 exists and is a
1161                                 directory.</para>
1162
1163                                 <para><varname>ConditionPathIsSymbolicLink=</varname>
1164                                 is similar to
1165                                 <varname>ConditionPathExists=</varname>
1166                                 but verifies whether a certain path
1167                                 exists and is a symbolic
1168                                 link.</para>
1169
1170                                 <para><varname>ConditionPathIsMountPoint=</varname>
1171                                 is similar to
1172                                 <varname>ConditionPathExists=</varname>
1173                                 but verifies whether a certain path
1174                                 exists and is a mount
1175                                 point.</para>
1176
1177                                 <para><varname>ConditionPathIsReadWrite=</varname>
1178                                 is similar to
1179                                 <varname>ConditionPathExists=</varname>
1180                                 but verifies whether the underlying
1181                                 file system is readable and writable
1182                                 (i.e. not mounted
1183                                 read-only).</para>
1184
1185                                 <para><varname>ConditionDirectoryNotEmpty=</varname>
1186                                 is similar to
1187                                 <varname>ConditionPathExists=</varname>
1188                                 but verifies whether a certain path
1189                                 exists and is a non-empty
1190                                 directory.</para>
1191
1192                                 <para><varname>ConditionFileNotEmpty=</varname>
1193                                 is similar to
1194                                 <varname>ConditionPathExists=</varname>
1195                                 but verifies whether a certain path
1196                                 exists and refers to a regular file
1197                                 with a non-zero size.</para>
1198
1199                                 <para><varname>ConditionFileIsExecutable=</varname>
1200                                 is similar to
1201                                 <varname>ConditionPathExists=</varname>
1202                                 but verifies whether a certain path
1203                                 exists, is a regular file and marked
1204                                 executable.</para>
1205
1206                                 <para>Finally,
1207                                 <varname>ConditionNull=</varname> may
1208                                 be used to add a constant condition
1209                                 check value to the unit. It takes a
1210                                 boolean argument. If set to
1211                                 <varname>false</varname>, the condition
1212                                 will always fail, otherwise
1213                                 succeed.</para>
1214
1215                                 <para>If multiple conditions are
1216                                 specified, the unit will be executed if
1217                                 all of them apply (i.e. a logical AND
1218                                 is applied). Condition checks can be
1219                                 prefixed with a pipe symbol (|) in
1220                                 which case a condition becomes a
1221                                 triggering condition. If at least one
1222                                 triggering condition is defined for a
1223                                 unit, then the unit will be executed if
1224                                 at least one of the triggering
1225                                 conditions apply and all of the
1226                                 non-triggering conditions. If you
1227                                 prefix an argument with the pipe
1228                                 symbol and an exclamation mark, the
1229                                 pipe symbol must be passed first, the
1230                                 exclamation second. Except for
1231                                 <varname>ConditionPathIsSymbolicLink=</varname>,
1232                                 all path checks follow symlinks. If
1233                                 any of these options is assigned the
1234                                 empty string, the list of conditions is
1235                                 reset completely, all previous
1236                                 condition settings (of any kind) will
1237                                 have no effect.</para></listitem>
1238                         </varlistentry>
1239
1240                         <varlistentry>
1241                                 <term><varname>SourcePath=</varname></term>
1242                                 <listitem><para>A path to a
1243                                 configuration file this unit has been
1244                                 generated from. This is primarily
1245                                 useful for implementation of generator
1246                                 tools that convert configuration from
1247                                 an external configuration file format
1248                                 into native unit files. This
1249                                 functionality should not be used in
1250                                 normal units.</para></listitem>
1251                         </varlistentry>
1252                 </variablelist>
1253
1254         </refsect1>
1255
1256         <refsect1>
1257                 <title>[Install] Section Options</title>
1258
1259                 <para>Unit file may include a [Install] section, which
1260                 carries installation information for the unit. This
1261                 section is not interpreted by
1262                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1263                 during runtime. It is used exclusively by the
1264                 <command>enable</command> and
1265                 <command>disable</command> commands of the
1266                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1267                 tool during installation of a unit:</para>
1268
1269                 <variablelist class='unit-directives'>
1270                         <varlistentry>
1271                                 <term><varname>Alias=</varname></term>
1272
1273                                 <listitem><para>A space-seperated list
1274                                 of additional names this unit shall be
1275                                 installed under. The names listed here
1276                                 must have the same suffix (i.e. type)
1277                                 as the unit file name. This option may
1278                                 be specified more than once, in which
1279                                 case all listed names are used. At
1280                                 installation time, <command>systemctl
1281                                 enable</command> will create symlinks
1282                                 from these names to the unit
1283                                 filename.</para></listitem>
1284                         </varlistentry>
1285
1286                         <varlistentry>
1287                                 <term><varname>WantedBy=</varname></term>
1288                                 <term><varname>RequiredBy=</varname></term>
1289
1290                                 <listitem><para>This option may be
1291                                 used more than once, or a
1292                                 space-separated list of unit names may
1293                                 be given. A symbolic link is created
1294                                 in the <filename>.wants/</filename> or
1295                                 <filename>.requires/</filename>
1296                                 directory of each of the listed units
1297                                 when this unit is installed by
1298                                 <command>systemctl enable</command>.
1299                                 This has the effect that a dependency
1300                                 of type <varname>Wants=</varname> or
1301                                 <varname>Requires=</varname> is added
1302                                 from the listed unit to the current
1303                                 unit. The primary result is that the
1304                                 current unit will be started when the
1305                                 listed unit is started. See the
1306                                 description of
1307                                 <varname>Wants=</varname> and
1308                                 <varname>Requires=</varname> in the
1309                                 [Unit] section for details.</para>
1310
1311                                 <para><command>WantedBy=foo.service</command>
1312                                 in a service
1313                                 <filename>bar.service</filename> is
1314                                 mostly equivalent to
1315                                 <command>Alias=foo.service.wants/bar.service</command>
1316                                 in the same file. In case of template
1317                                 units, <command>systemctl enable</command>
1318                                 must be called with an instance name, and
1319                                 this instance will be added to the
1320                                 <filename>.wants/</filename> or
1321                                 <filename>.requires/</filename> list
1322                                 of the listed unit.
1323                                 E.g. <command>WantedBy=getty.target</command>
1324                                 in a service
1325                                 <filename>getty@.service</filename>
1326                                 will result in <command>systemctl
1327                                 enable getty@tty2.service</command>
1328                                 creating a
1329                                 <filename>getty.target.wants/getty@tty2.service</filename>
1330                                 link to <filename>getty@.service</filename>.
1331                                 </para></listitem>
1332                         </varlistentry>
1333
1334                         <varlistentry>
1335                                 <term><varname>Also=</varname></term>
1336
1337                                 <listitem><para>Additional units to
1338                                 install/deinstall when this unit is
1339                                 installed/deinstalled. If the user
1340                                 requests installation/deinstallation
1341                                 of a unit with this option configured,
1342                                 <command>systemctl enable</command>
1343                                 and <command>systemctl
1344                                 disable</command> will automatically
1345                                 install/uninstall units listed in this option as
1346                                 well.</para>
1347
1348                                 <para>This option may be used more
1349                                 than once, or a space-separated list
1350                                 of unit names may be
1351                                 given.</para></listitem>
1352                         </varlistentry>
1353
1354                         <varlistentry>
1355                                 <term><varname>DefaultInstance=</varname></term>
1356
1357                                 <listitem><para>In template unit files,
1358                                 this specifies for which instance the
1359                                 unit shall be enabled if the template
1360                                 is enabled without any explicitly set
1361                                 instance. This option has no effect in
1362                                 non-template unit files. The specified
1363                                 string must be usable as instance
1364                                 identifier.</para></listitem>
1365                         </varlistentry>
1366                 </variablelist>
1367
1368                 <para>The following specifiers are interpreted in the
1369                 Install section: %n, %N, %p, %i, %U, %u, %m, %H, %b, %v.
1370                 For their meaning see the next section.
1371                 </para>
1372         </refsect1>
1373
1374         <refsect1>
1375                 <title>Specifiers</title>
1376
1377                 <para>Many settings resolve specifiers which may be
1378                 used to write generic unit files referring to runtime
1379                 or unit parameters that are replaced when the unit
1380                 files are loaded. The following specifiers are
1381                 understood:</para>
1382
1383                 <table>
1384                   <title>Specifiers available in unit files</title>
1385                   <tgroup cols='3' align='left' colsep='1' rowsep='1'>
1386                     <colspec colname="spec" />
1387                     <colspec colname="mean" />
1388                     <colspec colname="detail" />
1389                     <thead>
1390                       <row>
1391                         <entry>Specifier</entry>
1392                         <entry>Meaning</entry>
1393                         <entry>Details</entry>
1394                       </row>
1395                     </thead>
1396                     <tbody>
1397                       <row>
1398                         <entry><literal>%n</literal></entry>
1399                         <entry>Full unit name</entry>
1400                         <entry></entry>
1401                       </row>
1402                       <row>
1403                         <entry><literal>%N</literal></entry>
1404                         <entry>Unescaped full unit name</entry>
1405                         <entry>Same as <literal>%n</literal>, but with escaping undone</entry>
1406                       </row>
1407                       <row>
1408                         <entry><literal>%p</literal></entry>
1409                         <entry>Prefix name</entry>
1410                         <entry>For instantiated units, this refers to the string before the <literal>@</literal> character of the unit name. For non-instantiated units, this refers to the name of the unit with the type suffix removed.</entry>
1411                       </row>
1412                       <row>
1413                         <entry><literal>%P</literal></entry>
1414                         <entry>Unescaped prefix name</entry>
1415                         <entry>Same as <literal>%p</literal>, but with escaping undone</entry>
1416                       </row>
1417                       <row>
1418                         <entry><literal>%i</literal></entry>
1419                         <entry>Instance name</entry>
1420                         <entry>For instantiated units: this is the string between the <literal>@</literal> character and the suffix of the unit name.</entry>
1421                       </row>
1422                       <row>
1423                         <entry><literal>%I</literal></entry>
1424                         <entry>Unescaped instance name</entry>
1425                         <entry>Same as <literal>%i</literal>, but with escaping undone</entry>
1426                       </row>
1427                       <row>
1428                         <entry><literal>%f</literal></entry>
1429                         <entry>Unescaped filename</entry>
1430                         <entry>This is either the unescaped instance name (if applicable) with <filename>/</filename> prepended (if applicable), or the prefix name prepended with <filename>/</filename>.</entry>
1431                       </row>
1432                       <row>
1433                         <entry><literal>%c</literal></entry>
1434                         <entry>Control group path of the unit</entry>
1435                         <entry>This path does not include the <filename>/sys/fs/cgroup/systemd/</filename> prefix.</entry>
1436                       </row>
1437                       <row>
1438                         <entry><literal>%r</literal></entry>
1439                         <entry>Control group path of the slice the unit is placed in</entry>
1440                         <entry>This usually maps to the parent cgroup path of <literal>%c</literal>.</entry>
1441                       </row>
1442                       <row>
1443                         <entry><literal>%R</literal></entry>
1444                         <entry>Root control group path below which slices and units are placed</entry>
1445                         <entry>For system instances, this resolves to <filename>/</filename>, except in containers, where this maps to the container's root control group path.</entry>
1446                       </row>
1447                       <row>
1448                         <entry><literal>%t</literal></entry>
1449                         <entry>Runtime directory</entry>
1450                         <entry>This is either <filename>/run</filename> (for the system manager) or the path <literal>$XDG_RUNTIME_DIR</literal> resolves to (for user managers).</entry>
1451                       </row>
1452                       <row>
1453                         <entry><literal>%u</literal></entry>
1454                         <entry>User name</entry>
1455                         <entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1456                       </row>
1457                       <row>
1458                         <entry><literal>%U</literal></entry>
1459                         <entry>User UID</entry>
1460                         <entry>This is the numeric UID of the configured user of the unit, or (if none is set) the user running the systemd user instance. Note that this specifier is not available for units run by the systemd system instance (as opposed to those run by a systemd user instance), unless the user has been configured as a numeric UID in the first place or the configured user is the root user.</entry>
1461                       </row>
1462                       <row>
1463                         <entry><literal>%h</literal></entry>
1464                         <entry>User home directory</entry>
1465                         <entry>This is the home directory of the configured user of the unit, or (if none is set) the user running the systemd user instance. Similar to <literal>%U</literal>, this specifier is not available for units run by the systemd system instance, unless the configured user is the root user.</entry>
1466                       </row>
1467                       <row>
1468                         <entry><literal>%s</literal></entry>
1469                         <entry>User shell</entry>
1470                         <entry>This is the shell of the configured user of the unit, or (if none is set) the user running the systemd user instance. Similar to <literal>%U</literal>, this specifier is not available for units run by the systemd system instance, unless the configured user is the root user.</entry>
1471                       </row>
1472                       <row>
1473                         <entry><literal>%m</literal></entry>
1474                         <entry>Machine ID</entry>
1475                         <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>
1476                       </row>
1477                       <row>
1478                         <entry><literal>%b</literal></entry>
1479                         <entry>Boot ID</entry>
1480                         <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
1481                       </row>
1482                       <row>
1483                         <entry><literal>%H</literal></entry>
1484                         <entry>Host name</entry>
1485                         <entry>The hostname of the running system at the point in time the unit configuation is loaded.</entry>
1486                       </row>
1487                       <row>
1488                         <entry><literal>%v</literal></entry>
1489                         <entry>Kernel release</entry>
1490                         <entry>Identical to <command>uname -r</command> output</entry>
1491                       </row>
1492                       <row>
1493                         <entry><literal>%%</literal></entry>
1494                         <entry>Single percent sign</entry>
1495                         <entry>Use <literal>%%</literal> in place of <literal>%</literal> to specify a single percent sign.</entry>
1496                       </row>
1497                     </tbody>
1498                   </tgroup>
1499                 </table>
1500         </refsect1>
1501
1502         <refsect1>
1503                 <title>See Also</title>
1504                 <para>
1505                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1506                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1507                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1508                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1509                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1510                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1511                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1512                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1513                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1514                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1515                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1516                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1517                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1518                         <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1519                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1520                         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1521                         <citerefentry><refentrytitle>systemd-verify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1522                         <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1523                         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1524                         <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1525                 </para>
1526         </refsect1>
1527
1528 </refentry>