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>$XDG_RUNTIME_DIR/systemd/user/*</filename>
  77 <filename>/run/systemd/user/*</filename>
  78 <filename>$XDG_DATA_HOME/systemd/user/*</filename>
  79 <filename>$HOME/.local/share/systemd/user/*</filename>
  80 <filename>/usr/lib/systemd/user/*</filename>
  81 <filename>...</filename>
  82                 </literallayout></para>
  83         </refsynopsisdiv>
  84
  85         <refsect1>
  86                 <title>Description</title>
  87
  88                 <para>A unit configuration file encodes information
  89                 about a service, a socket, a device, a mount point, an
  90                 automount point, a swap file or partition, a start-up
  91                 target, a watched file system path, a timer controlled
  92                 and supervised by
  93                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  94                 a temporary system state snapshot, a resource
  95                 management slice or a group of externally created
  96                 processes. The syntax is inspired by <ulink
  97                 url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
  98                 Desktop Entry Specification</ulink>
  99                 <filename>.desktop</filename> files, which are in turn
 100                 inspired by Microsoft Windows
 101                 <filename>.ini</filename> files.</para>
 102
 103                 <para>This man page lists the common configuration
 104                 options of all the unit types. These options need to
 105                 be configured in the [Unit] or [Install]
 106                 sections of the unit files.</para>
 107
 108                 <para>In addition to the generic [Unit] and [Install]
 109                 sections described here, each unit may have a
 110                 type-specific section, e.g. [Service] for a service
 111                 unit. See the respective man pages for more
 112                 information:
 113                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 114                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 115                 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 116                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 117                 <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 118                 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 119                 <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 120                 <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 121                 <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 122                 <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 123                 <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 124                 <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 125                 </para>
 126
 127                 <para>Various settings are allowed to be specified
 128                 more than once, in which case the interpretation
 129                 depends on the setting. Often, multiple settings form
 130                 a list, and setting to an empty value "resets", which
 131                 means that previous assignments are ignored. When this
 132                 is allowed, it is mentioned in the description of the
 133                 setting. Note that using multiple assignments to the
 134                 same value makes the unit file incompatible with
 135                 parsers for the XDG <filename>.desktop</filename> file
 136                 format.</para>
 137
 138                 <para>Unit files are loaded from a set of paths
 139                 determined during compilation, described in the next section.
 140                 </para>
 141
 142                 <para>Unit files may contain additional options on top
 143                 of those listed here. If systemd encounters an unknown
 144                 option, it will write a warning log message but
 145                 continue loading the unit. If an option or section name
 146                 is prefixed with <option>X-</option>, it is ignored
 147                 completely by systemd. Options within an ignored
 148                 section do not need the prefix. Applications may use
 149                 this to include additional information in the unit
 150                 files.</para>
 151
 152                 <para>Boolean arguments used in unit files can be
 153                 written in various formats. For positive settings the
 154                 strings <option>1</option>, <option>yes</option>,
 155                 <option>true</option> and <option>on</option> are
 156                 equivalent. For negative settings, the strings
 157                 <option>0</option>, <option>no</option>,
 158                 <option>false</option> and <option>off</option> are
 159                 equivalent.</para>
 160
 161                 <para>Time span values encoded in unit files can be
 162                 written in various formats. A stand-alone number
 163                 specifies a time in seconds. If suffixed with a time
 164                 unit, the unit is honored. A concatenation of multiple
 165                 values with units is supported, in which case the
 166                 values are added up. Example: "50" refers to 50
 167                 seconds; "2min 200ms" refers to 2 minutes plus 200
 168                 milliseconds, i.e. 120200ms. The following time units
 169                 are understood: s, min, h, d, w, ms, us. For details
 170                 see
 171                 <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 172
 173                 <para>Empty lines and lines starting with # or ; are
 174                 ignored. This may be used for commenting. Lines ending
 175                 in a backslash are concatenated with the following
 176                 line while reading and the backslash is replaced by a
 177                 space character. This may be used to wrap long lines.</para>
 178
 179                 <para>Along with a unit file
 180                 <filename>foo.service</filename>, the directory
 181                 <filename>foo.service.wants/</filename> may exist. All
 182                 unit files symlinked from such a directory are
 183                 implicitly added as dependencies of type
 184                 <varname>Wanted=</varname> to the unit. This is useful
 185                 to hook units into the start-up of other units,
 186                 without having to modify their unit files. For details
 187                 about the semantics of <varname>Wanted=</varname>, see
 188                 below. The preferred way to create symlinks in the
 189                 <filename>.wants/</filename> directory of a unit file
 190                 is with the <command>enable</command> command of the
 191                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 192                 tool which reads information from the [Install]
 193                 section of unit files (see below). A similar
 194                 functionality exists for <varname>Requires=</varname>
 195                 type dependencies as well, the directory suffix is
 196                 <filename>.requires/</filename> in this case.</para>
 197
 198                 <para>Along with a unit file
 199                 <filename>foo.service</filename>, a directory
 200                 <filename>foo.service.d/</filename> may exist. All
 201                 files with the suffix <literal>.conf</literal> from
 202                 this directory will be parsed after the file itself is
 203                 parsed. This is useful to alter or add configuration
 204                 settings to a unit, without having to modify their
 205                 unit files. Make sure that the file that is included
 206                 has the appropriate section headers before any
 207                 directive. Note that for instanced units this logic
 208                 will first look for the instance
 209                 <literal>.d/</literal> subdirectory and read its
 210                 <literal>.conf</literal> files, followed by the
 211                 template <literal>.d/</literal> subdirectory and reads
 212                 its <literal>.conf</literal> files.</para>
 213
 214                 <para>Note that while systemd offers a flexible
 215                 dependency system between units it is recommended to
 216                 use this functionality only sparingly and instead rely
 217                 on techniques such as bus-based or socket-based
 218                 activation which make dependencies implicit, resulting
 219                 in a both simpler and more flexible system.</para>
 220
 221                 <para>Some unit names reflect paths existing in the
 222                 file system namespace. Example: a device unit
 223                 <filename>dev-sda.device</filename> refers to a device
 224                 with the device node <filename noindex='true'>/dev/sda</filename> in
 225                 the file system namespace. If this applies, a special
 226                 way to escape the path name is used, so that the
 227                 result is usable as part of a filename. Basically,
 228                 given a path, "/" is replaced by "-", and all
 229                 unprintable characters and the "-" are replaced by
 230                 C-style "\x2d" escapes. The root directory "/" is
 231                 encoded as single dash, while otherwise the initial
 232                 and ending "/" is removed from all paths during
 233                 transformation. This escaping is reversible.</para>
 234
 235                 <para>Optionally, units may be instantiated from a
 236                 template file at runtime. This allows creation of
 237                 multiple units from a single configuration file. If
 238                 systemd looks for a unit configuration file, it will
 239                 first search for the literal unit name in the
 240                 file system. If that yields no success and the unit
 241                 name contains an <literal>@</literal> character, systemd will look for a
 242                 unit template that shares the same name but with the
 243                 instance string (i.e. the part between the <literal>@</literal> character
 244                 and the suffix) removed. Example: if a service
 245                 <filename>getty@tty3.service</filename> is requested
 246                 and no file by that name is found, systemd will look
 247                 for <filename>getty@.service</filename> and
 248                 instantiate a service from that configuration file if
 249                 it is found.</para>
 250
 251                 <para>To refer to the instance string from
 252                 within the configuration file you may use the special
 253                 <literal>%i</literal> specifier in many of the
 254                 configuration options. See below for details.</para>
 255
 256                 <para>If a unit file is empty (i.e. has the file size
 257                 0) or is symlinked to <filename>/dev/null</filename>,
 258                 its configuration will not be loaded and it appears
 259                 with a load state of <literal>masked</literal>, and
 260                 cannot be activated. Use this as an effective way to
 261                 fully disable a unit, making it impossible to start it
 262                 even manually.</para>
 263
 264                 <para>The unit file format is covered by the
 265                 <ulink
 266                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 267                 Stability Promise</ulink>.</para>
 268
 269         </refsect1>
 270
 271         <refsect1>
 272                 <title>Unit Load Path</title>
 273
 274                 <para>Unit files are loaded from a set of paths
 275                 determined during compilation, described in the two
 276                 tables below. Unit files found in directories listed
 277                 earlier override files with the same name in
 278                 directories lower in the list.</para>
 279
 280                 <para>When systemd is running in user mode
 281                 (<option>--user</option>) and the variable
 282                 <varname>$SYSTEMD_UNIT_PATH</varname> is set, this
 283                 contents of this variable overrides the unit load
 284                 path. If <varname>$SYSTEMD_UNIT_PATH</varname> ends
 285                 with an empty component (<literal>:</literal>), the
 286                 usual unit load path will be appended to the contents
 287                 of the variable.</para>
 288
 289                 <table>
 290                   <title>
 291                     Load path when running in system mode (<option>--system</option>).
 292                   </title>
 293
 294                   <tgroup cols='2'>
 295                     <colspec colname='path' />
 296                     <colspec colname='expl' />
 297                     <thead>
 298                       <row>
 299                         <entry>Path</entry>
 300                         <entry>Description</entry>
 301                       </row>
 302                     </thead>
 303                     <tbody>
 304                       <row>
 305                         <entry><filename>/etc/systemd/system</filename></entry>
 306                         <entry>Local configuration</entry>
 307                       </row>
 308                       <row>
 309                         <entry><filename>/run/systemd/system</filename></entry>
 310                         <entry>Runtime units</entry>
 311                       </row>
 312                       <row>
 313                         <entry><filename>/usr/lib/systemd/system</filename></entry>
 314                         <entry>Units of installed packages</entry>
 315                       </row>
 316                     </tbody>
 317                   </tgroup>
 318                 </table>
 319
 320                 <table>
 321                   <title>
 322                     Load path when running in user mode (<option>--user</option>).
 323                   </title>
 324
 325                   <tgroup cols='2'>
 326                     <colspec colname='path' />
 327                     <colspec colname='expl' />
 328                     <thead>
 329                       <row>
 330                         <entry>Path</entry>
 331                         <entry>Description</entry>
 332                       </row>
 333                     </thead>
 334                     <tbody>
 335                       <row>
 336                         <entry><filename>$XDG_CONFIG_HOME/systemd/user</filename></entry>
 337                         <entry>User configuration (only used when $XDG_CONFIG_HOME is set)</entry>
 338                       </row>
 339                       <row>
 340                         <entry><filename>$HOME/.config/systemd/user</filename></entry>
 341                         <entry>User configuration (only used when $XDG_CONFIG_HOME is not set)</entry>
 342                       </row>
 343                       <row>
 344                         <entry><filename>/etc/systemd/user</filename></entry>
 345                         <entry>Local configuration</entry>
 346                       </row>
 347                       <row>
 348                         <entry><filename>$XDG_RUNTIME_DIR/systemd/user</filename></entry>
 349                         <entry>Runtime units (only used when $XDG_RUNTIME_DIR is set)</entry>
 350                       </row>
 351                       <row>
 352                         <entry><filename>/run/systemd/user</filename></entry>
 353                         <entry>Runtime units</entry>
 354                       </row>
 355                       <row>
 356                         <entry><filename>$XDG_DATA_HOME/systemd/user</filename></entry>
 357                         <entry>Units of packages that have been installed in the home directory (only used when $XDG_DATA_HOME is set)</entry>
 358                       </row>
 359                       <row>
 360                         <entry><filename>$HOME/.local/share/systemd/user</filename></entry>
 361                         <entry>Units of packages that have been installed in the home directory (only used when $XDG_DATA_HOME is not set)</entry>
 362                       </row>
 363                       <row>
 364                         <entry><filename>/usr/lib/systemd/user</filename></entry>
 365                         <entry>Units of packages that have been installed system-wide</entry>
 366                       </row>
 367                     </tbody>
 368                   </tgroup>
 369                 </table>
 370
 371                 <para>Additional units might be loaded into systemd
 372                 ("linked") from directories not on the unit load
 373                 path. See the <command>link</command> command for
 374                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>. Also,
 375                 some units are dynamically created via generators
 376                 <ulink
 377                 url="http://www.freedesktop.org/wiki/Software/systemd/Generators/">Generators</ulink>.
 378                 </para>
 379         </refsect1>
 380
 381         <refsect1>
 382                 <title>[Unit] Section Options</title>
 383
 384                 <para>Unit file may include a [Unit] section, which
 385                 carries generic information about the unit that is not
 386                 dependent on the type of unit:</para>
 387
 388                 <variablelist class='unit-directives'>
 389
 390                         <varlistentry>
 391                                 <term><varname>Description=</varname></term>
 392                                 <listitem><para>A free-form string
 393                                 describing the unit. This is intended
 394                                 for use in UIs to show descriptive
 395                                 information along with the unit
 396                                 name. The description should contain a name
 397                                 that means something to the end user.
 398                                 <literal>Apache2 Web Server</literal> is a good
 399                                 example. Bad examples are
 400                                 <literal>high-performance light-weight HTTP
 401                                 server</literal> (too generic) or
 402                                 <literal>Apache2</literal> (too specific and
 403                                 meaningless for people who do not know
 404                                 Apache).</para></listitem>
 405                         </varlistentry>
 406
 407                         <varlistentry>
 408                                 <term><varname>Documentation=</varname></term>
 409                                 <listitem><para>A space-separated list
 410                                 of URIs referencing documentation for
 411                                 this unit or its
 412                                 configuration. Accepted are only URIs
 413                                 of the types
 414                                 <literal>http://</literal>,
 415                                 <literal>https://</literal>,
 416                                 <literal>file:</literal>,
 417                                 <literal>info:</literal>,
 418                                 <literal>man:</literal>. For more
 419                                 information about the syntax of these
 420                                 URIs, see
 421                                 <citerefentry project='man-pages'><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
 422                                 URIs should be listed in order of
 423                                 relevance, starting with the most
 424                                 relevant. It is a good idea to first
 425                                 reference documentation that explains
 426                                 what the unit's purpose is, followed
 427                                 by how it is configured, followed by
 428                                 any other related documentation. This
 429                                 option may be specified more than once,
 430                                 in which case the specified list of
 431                                 URIs is merged. If the empty string is
 432                                 assigned to this option, the list is
 433                                 reset and all prior assignments will
 434                                 have no effect.</para></listitem>
 435                         </varlistentry>
 436
 437                         <varlistentry>
 438                                 <term><varname>Requires=</varname></term>
 439
 440                                 <listitem><para>Configures requirement
 441                                 dependencies on other units. If this
 442                                 unit gets activated, the units listed
 443                                 here will be activated as well. If one
 444                                 of the other units gets deactivated or
 445                                 its activation fails, this unit will
 446                                 be deactivated. This option may be
 447                                 specified more than once or multiple
 448                                 space-separated units may be specified
 449                                 in one option in which case
 450                                 requirement dependencies for all
 451                                 listed names will be created. Note
 452                                 that requirement dependencies do not
 453                                 influence the order in which services
 454                                 are started or stopped. This has to be
 455                                 configured independently with the
 456                                 <varname>After=</varname> or
 457                                 <varname>Before=</varname> options. If
 458                                 a unit
 459                                 <filename>foo.service</filename>
 460                                 requires a unit
 461                                 <filename>bar.service</filename> as
 462                                 configured with
 463                                 <varname>Requires=</varname> and no
 464                                 ordering is configured with
 465                                 <varname>After=</varname> or
 466                                 <varname>Before=</varname>, then both
 467                                 units will be started simultaneously
 468                                 and without any delay between them if
 469                                 <filename>foo.service</filename> is
 470                                 activated. Often it is a better choice
 471                                 to use <varname>Wants=</varname>
 472                                 instead of
 473                                 <varname>Requires=</varname> in order
 474                                 to achieve a system that is more
 475                                 robust when dealing with failing
 476                                 services.</para>
 477
 478                                 <para>Note that dependencies of this
 479                                 type may also be configured outside of
 480                                 the unit configuration file by
 481                                 adding a symlink to a
 482                                 <filename>.requires/</filename> directory
 483                                 accompanying the unit file. For
 484                                 details see above.</para></listitem>
 485                         </varlistentry>
 486
 487                         <varlistentry>
 488                                 <term><varname>RequiresOverridable=</varname></term>
 489
 490                                 <listitem><para>Similar to
 491                                 <varname>Requires=</varname>.
 492                                 Dependencies listed in
 493                                 <varname>RequiresOverridable=</varname>
 494                                 which cannot be fulfilled or fail to
 495                                 start are ignored if the startup was
 496                                 explicitly requested by the user. If
 497                                 the start-up was pulled in indirectly
 498                                 by some dependency or automatic
 499                                 start-up of units that is not
 500                                 requested by the user, this dependency
 501                                 must be fulfilled and otherwise the
 502                                 transaction fails. Hence, this option
 503                                 may be used to configure dependencies
 504                                 that are normally honored unless the
 505                                 user explicitly starts up the unit, in
 506                                 which case whether they failed or not
 507                                 is irrelevant.</para></listitem>
 508
 509                         </varlistentry>
 510                         <varlistentry>
 511                                 <term><varname>Requisite=</varname></term>
 512                                 <term><varname>RequisiteOverridable=</varname></term>
 513
 514                                 <listitem><para>Similar to
 515                                 <varname>Requires=</varname> and
 516                                 <varname>RequiresOverridable=</varname>,
 517                                 respectively. However, if the units
 518                                 listed here are not started already,
 519                                 they will not be started and the
 520                                 transaction will fail immediately.
 521                                 </para></listitem>
 522                         </varlistentry>
 523
 524                         <varlistentry>
 525                                 <term><varname>Wants=</varname></term>
 526
 527                                 <listitem><para>A weaker version of
 528                                 <varname>Requires=</varname>. Units
 529                                 listed in this option will be started
 530                                 if the configuring unit is. However,
 531                                 if the listed units fail to start
 532                                 or cannot be added to the transaction,
 533                                 this has no impact on the validity of
 534                                 the transaction as a whole. This is
 535                                 the recommended way to hook start-up
 536                                 of one unit to the start-up of another
 537                                 unit.</para>
 538
 539                                 <para>Note that dependencies of this
 540                                 type may also be configured outside of
 541                                 the unit configuration file by adding
 542                                 symlinks to a
 543                                 <filename>.wants/</filename> directory
 544                                 accompanying the unit file. For
 545                                 details, see above.</para></listitem>
 546                         </varlistentry>
 547
 548                         <varlistentry>
 549                                 <term><varname>BindsTo=</varname></term>
 550
 551                                 <listitem><para>Configures requirement
 552                                 dependencies, very similar in style to
 553                                 <varname>Requires=</varname>, however
 554                                 in addition to this behavior, it also
 555                                 declares that this unit is stopped
 556                                 when any of the units listed suddenly
 557                                 disappears. Units can suddenly,
 558                                 unexpectedly disappear if a service
 559                                 terminates on its own choice, a device
 560                                 is unplugged or a mount point
 561                                 unmounted without involvement of
 562                                 systemd.</para></listitem>
 563                         </varlistentry>
 564
 565                         <varlistentry>
 566                                 <term><varname>PartOf=</varname></term>
 567
 568                                 <listitem><para>Configures dependencies
 569                                 similar to <varname>Requires=</varname>,
 570                                 but limited to stopping and restarting
 571                                 of units. When systemd stops or restarts
 572                                 the units listed here, the action is
 573                                 propagated to this unit.
 574                                 Note that this is a one-way dependency —
 575                                 changes to this unit do not affect the
 576                                 listed units.
 577                                 </para></listitem>
 578                         </varlistentry>
 579
 580                         <varlistentry>
 581                                 <term><varname>Conflicts=</varname></term>
 582
 583                                 <listitem><para>A space-separated list
 584                                 of unit names. Configures negative
 585                                 requirement dependencies. If a unit
 586                                 has a <varname>Conflicts=</varname>
 587                                 setting on another unit, starting the
 588                                 former will stop the latter and vice
 589                                 versa. Note that this setting is
 590                                 independent of and orthogonal to the
 591                                 <varname>After=</varname> and
 592                                 <varname>Before=</varname> ordering
 593                                 dependencies.</para>
 594
 595                                 <para>If a unit A that conflicts with
 596                                 a unit B is scheduled to be started at
 597                                 the same time as B, the transaction
 598                                 will either fail (in case both are
 599                                 required part of the transaction) or
 600                                 be modified to be fixed (in case one
 601                                 or both jobs are not a required part
 602                                 of the transaction). In the latter
 603                                 case, the job that is not the required
 604                                 will be removed, or in case both are
 605                                 not required, the unit that conflicts
 606                                 will be started and the unit that is
 607                                 conflicted is
 608                                 stopped.</para></listitem>
 609                         </varlistentry>
 610
 611                         <varlistentry>
 612                                 <term><varname>Before=</varname></term>
 613                                 <term><varname>After=</varname></term>
 614
 615                                 <listitem><para>A space-separated list
 616                                 of unit names. Configures ordering
 617                                 dependencies between units. If a unit
 618                                 <filename>foo.service</filename>
 619                                 contains a setting
 620                                 <option>Before=bar.service</option>
 621                                 and both units are being started,
 622                                 <filename>bar.service</filename>'s
 623                                 start-up is delayed until
 624                                 <filename>foo.service</filename> is
 625                                 started up. Note that this setting is
 626                                 independent of and orthogonal to the
 627                                 requirement dependencies as configured
 628                                 by <varname>Requires=</varname>. It is
 629                                 a common pattern to include a unit
 630                                 name in both the
 631                                 <varname>After=</varname> and
 632                                 <varname>Requires=</varname> option, in
 633                                 which case the unit listed will be
 634                                 started before the unit that is
 635                                 configured with these options. This
 636                                 option may be specified more than
 637                                 once, in which case ordering
 638                                 dependencies for all listed names are
 639                                 created. <varname>After=</varname> is
 640                                 the inverse of
 641                                 <varname>Before=</varname>, i.e. while
 642                                 <varname>After=</varname> ensures that
 643                                 the configured unit is started after
 644                                 the listed unit finished starting up,
 645                                 <varname>Before=</varname> ensures the
 646                                 opposite, i.e.  that the configured
 647                                 unit is fully started up before the
 648                                 listed unit is started. Note that when
 649                                 two units with an ordering dependency
 650                                 between them are shut down, the
 651                                 inverse of the start-up order is
 652                                 applied. i.e. if a unit is configured
 653                                 with <varname>After=</varname> on
 654                                 another unit, the former is stopped
 655                                 before the latter if both are shut
 656                                 down. If one unit with an ordering
 657                                 dependency on another unit is shut
 658                                 down while the latter is started up,
 659                                 the shut down is ordered before the
 660                                 start-up regardless of whether the
 661                                 ordering dependency is actually of
 662                                 type <varname>After=</varname> or
 663                                 <varname>Before=</varname>. If two
 664                                 units have no ordering dependencies
 665                                 between them, they are shut down or
 666                                 started up simultaneously, and no
 667                                 ordering takes
 668                                 place. </para></listitem>
 669                         </varlistentry>
 670
 671                         <varlistentry>
 672                                 <term><varname>OnFailure=</varname></term>
 673
 674                                 <listitem><para>A space-separated list
 675                                 of one or more units that are
 676                                 activated when this unit enters the
 677                                 <literal>failed</literal>
 678                                 state.</para></listitem>
 679                         </varlistentry>
 680
 681                         <varlistentry>
 682                                 <term><varname>PropagatesReloadTo=</varname></term>
 683                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 684
 685                                 <listitem><para>A space-separated list
 686                                 of one or more units where reload
 687                                 requests on this unit will be
 688                                 propagated to, or reload requests on
 689                                 the other unit will be propagated to
 690                                 this unit, respectively. Issuing a
 691                                 reload request on a unit will
 692                                 automatically also enqueue a reload
 693                                 request on all units that the reload
 694                                 request shall be propagated to via
 695                                 these two settings.</para></listitem>
 696                         </varlistentry>
 697
 698                         <varlistentry>
 699                                 <term><varname>JoinsNamespaceOf=</varname></term>
 700
 701                                 <listitem><para>For units that start
 702                                 processes (such as service units),
 703                                 lists one or more other units whose
 704                                 network and/or temporary file
 705                                 namespace to join. This only applies
 706                                 to unit types which support the
 707                                 <varname>PrivateNetwork=</varname> and
 708                                 <varname>PrivateTmp=</varname>
 709                                 directives (see
 710                                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 711                                 for details). If a unit that has this
 712                                 setting set is started, its processes
 713                                 will see the same
 714                                 <filename>/tmp</filename>,
 715                                 <filename>/tmp/var</filename> and
 716                                 network namespace as one listed unit
 717                                 that is started. If multiple listed
 718                                 units are already started, it is not
 719                                 defined which namespace is
 720                                 joined. Note that this setting only
 721                                 has an effect if
 722                                 <varname>PrivateNetwork=</varname>
 723                                 and/or <varname>PrivateTmp=</varname>
 724                                 is enabled for both the unit that
 725                                 joins the namespace and the unit whose
 726                                 namespace is joined.</para></listitem>
 727                         </varlistentry>
 728
 729                         <varlistentry>
 730                                 <term><varname>RequiresMountsFor=</varname></term>
 731
 732                                 <listitem><para>Takes a
 733                                 space-separated list of absolute
 734                                 paths. Automatically adds dependencies
 735                                 of type <varname>Requires=</varname>
 736                                 and <varname>After=</varname> for all
 737                                 mount units required to access the
 738                                 specified path.</para>
 739
 740                                 <para>Mount points marked with
 741                                 <option>noauto</option> are not
 742                                 mounted automatically and will be
 743                                 ignored for the purposes of this
 744                                 option. If such a mount should be a
 745                                 requirement for this unit,
 746                                 direct dependencies on the mount
 747                                 units may be added
 748                                 (<varname>Requires=</varname> and
 749                                 <varname>After=</varname> or
 750                                 some other combination).
 751                                 </para></listitem>
 752                         </varlistentry>
 753
 754                         <varlistentry>
 755                                 <term><varname>OnFailureJobMode=</varname></term>
 756
 757                                 <listitem><para>Takes a value of
 758                                 <literal>fail</literal>,
 759                                 <literal>replace</literal>,
 760                                 <literal>replace-irreversibly</literal>,
 761                                 <literal>isolate</literal>,
 762                                 <literal>flush</literal>,
 763                                 <literal>ignore-dependencies</literal>
 764                                 or
 765                                 <literal>ignore-requirements</literal>. Defaults
 766                                 to
 767                                 <literal>replace</literal>. Specifies
 768                                 how the units listed in
 769                                 <varname>OnFailure=</varname> will be
 770                                 enqueued. See
 771                                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
 772                                 <option>--job-mode=</option> option
 773                                 for details on the possible values. If
 774                                 this is set to
 775                                 <literal>isolate</literal>, only a
 776                                 single unit may be listed in
 777                                 <varname>OnFailure=</varname>..</para></listitem>
 778                         </varlistentry>
 779
 780                         <varlistentry>
 781                                 <term><varname>IgnoreOnIsolate=</varname></term>
 782
 783                                 <listitem><para>Takes a boolean
 784                                 argument. If <option>true</option>,
 785                                 this unit will not be stopped when
 786                                 isolating another unit. Defaults to
 787                                 <option>false</option>.</para></listitem>
 788                         </varlistentry>
 789
 790                         <varlistentry>
 791                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 792
 793                                 <listitem><para>Takes a boolean
 794                                 argument. If <option>true</option>,
 795                                 this unit will not be included in
 796                                 snapshots. Defaults to
 797                                 <option>true</option> for device and
 798                                 snapshot units, <option>false</option>
 799                                 for the others.</para></listitem>
 800                         </varlistentry>
 801
 802                         <varlistentry>
 803                                 <term><varname>StopWhenUnneeded=</varname></term>
 804
 805                                 <listitem><para>Takes a boolean
 806                                 argument. If <option>true</option>,
 807                                 this unit will be stopped when it is
 808                                 no longer used. Note that in order to
 809                                 minimize the work to be executed,
 810                                 systemd will not stop units by default
 811                                 unless they are conflicting with other
 812                                 units, or the user explicitly
 813                                 requested their shut down. If this
 814                                 option is set, a unit will be
 815                                 automatically cleaned up if no other
 816                                 active unit requires it. Defaults to
 817                                 <option>false</option>.</para></listitem>
 818                         </varlistentry>
 819
 820                         <varlistentry>
 821                                 <term><varname>RefuseManualStart=</varname></term>
 822                                 <term><varname>RefuseManualStop=</varname></term>
 823
 824                                 <listitem><para>Takes a boolean
 825                                 argument. If <option>true</option>,
 826                                 this unit can only be activated
 827                                 or deactivated indirectly. In
 828                                 this case, explicit start-up
 829                                 or termination requested by the
 830                                 user is denied, however if it is
 831                                 started or stopped as a
 832                                 dependency of another unit, start-up
 833                                 or termination will succeed. This
 834                                 is mostly a safety feature to ensure
 835                                 that the user does not accidentally
 836                                 activate units that are not intended
 837                                 to be activated explicitly, and not
 838                                 accidentally deactivate units that are
 839                                 not intended to be deactivated.
 840                                 These options default to
 841                                 <option>false</option>.</para></listitem>
 842                         </varlistentry>
 843
 844                         <varlistentry>
 845                                 <term><varname>AllowIsolate=</varname></term>
 846
 847                                 <listitem><para>Takes a boolean
 848                                 argument. If <option>true</option>,
 849                                 this unit may be used with the
 850                                 <command>systemctl isolate</command>
 851                                 command. Otherwise, this will be
 852                                 refused. It probably is a good idea to
 853                                 leave this disabled except for target
 854                                 units that shall be used similar to
 855                                 runlevels in SysV init systems, just
 856                                 as a precaution to avoid unusable
 857                                 system states. This option defaults to
 858                                 <option>false</option>.</para></listitem>
 859                         </varlistentry>
 860
 861                         <varlistentry>
 862                                 <term><varname>DefaultDependencies=</varname></term>
 863
 864                                 <listitem><para>Takes a boolean
 865                                 argument. If <option>true</option>,
 866                                 (the default), a few default
 867                                 dependencies will implicitly be
 868                                 created for the unit. The actual
 869                                 dependencies created depend on the
 870                                 unit type. For example, for service
 871                                 units, these dependencies ensure that
 872                                 the service is started only after
 873                                 basic system initialization is
 874                                 completed and is properly terminated on
 875                                 system shutdown. See the respective
 876                                 man pages for details. Generally, only
 877                                 services involved with early boot or
 878                                 late shutdown should set this option
 879                                 to <option>false</option>. It is
 880                                 highly recommended to leave this
 881                                 option enabled for the majority of
 882                                 common units. If set to
 883                                 <option>false</option>, this option
 884                                 does not disable all implicit
 885                                 dependencies, just non-essential
 886                                 ones.</para></listitem>
 887                         </varlistentry>
 888
 889                         <varlistentry>
 890                                 <term><varname>JobTimeoutSec=</varname></term>
 891
 892                                 <listitem><para>When clients are
 893                                 waiting for a job of this unit to
 894                                 complete, time out after the specified
 895                                 time. If this time limit is reached,
 896                                 the job will be cancelled, the unit
 897                                 however will not change state or even
 898                                 enter the <literal>failed</literal>
 899                                 mode. This value defaults to 0 (job
 900                                 timeouts disabled), except for device
 901                                 units. NB: this timeout is independent
 902                                 from any unit-specific timeout (for
 903                                 example, the timeout set with
 904                                 <varname>Timeout=</varname> in service
 905                                 units) as the job timeout has no
 906                                 effect on the unit itself, only on the
 907                                 job that might be pending for it. Or
 908                                 in other words: unit-specific timeouts
 909                                 are useful to abort unit state
 910                                 changes, and revert them. The job
 911                                 timeout set with this option however
 912                                 is useful to abort only the job
 913                                 waiting for the unit state to
 914                                 change.</para></listitem>
 915                         </varlistentry>
 916
 917                         <varlistentry>
 918                                 <term><varname>ConditionArchitecture=</varname></term>
 919                                 <term><varname>ConditionVirtualization=</varname></term>
 920                                 <term><varname>ConditionHost=</varname></term>
 921                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 922                                 <term><varname>ConditionSecurity=</varname></term>
 923                                 <term><varname>ConditionCapability=</varname></term>
 924                                 <term><varname>ConditionACPower=</varname></term>
 925                                 <term><varname>ConditionNeedsUpdate=</varname></term>
 926                                 <term><varname>ConditionFirstBoot=</varname></term>
 927                                 <term><varname>ConditionPathExists=</varname></term>
 928                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 929                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 930                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 931                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 932                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 933                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 934                                 <term><varname>ConditionFileNotEmpty=</varname></term>
 935                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 936                                 <term><varname>ConditionNull=</varname></term>
 937
 938                                 <listitem><para>Before starting a unit
 939                                 verify that the specified condition is
 940                                 true. If it is not true, the starting
 941                                 of the unit will be skipped, however
 942                                 all ordering dependencies of it are
 943                                 still respected. A failing condition
 944                                 will not result in the unit being
 945                                 moved into a failure state. The
 946                                 condition is checked at the time the
 947                                 queued start job is to be
 948                                 executed.</para>
 949
 950                                 <para><varname>ConditionArchitecture=</varname>
 951                                 may be used to check whether the
 952                                 system is running on a specific
 953                                 architecture. Takes one of
 954                                 <varname>x86</varname>,
 955                                 <varname>x86-64</varname>,
 956                                 <varname>ppc</varname>,
 957                                 <varname>ppc-le</varname>,
 958                                 <varname>ppc64</varname>,
 959                                 <varname>ppc64-le</varname>,
 960                                 <varname>ia64</varname>,
 961                                 <varname>parisc</varname>,
 962                                 <varname>parisc64</varname>,
 963                                 <varname>s390</varname>,
 964                                 <varname>s390x</varname>,
 965                                 <varname>sparc</varname>,
 966                                 <varname>sparc64</varname>,
 967                                 <varname>mips</varname>,
 968                                 <varname>mips-le</varname>,
 969                                 <varname>mips64</varname>,
 970                                 <varname>mips64-le</varname>,
 971                                 <varname>alpha</varname>,
 972                                 <varname>arm</varname>,
 973                                 <varname>arm-be</varname>,
 974                                 <varname>arm64</varname>,
 975                                 <varname>arm64-be</varname>,
 976                                 <varname>sh</varname>,
 977                                 <varname>sh64</varname>,
 978                                 <varname>m86k</varname>,
 979                                 <varname>tilegx</varname>,
 980                                 <varname>cris</varname> to test
 981                                 against a specific architecture. The
 982                                 architecture is determined from the
 983                                 information returned by
 984                                 <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 985                                 and is thus subject to
 986                                 <citerefentry><refentrytitle>personality</refentrytitle><manvolnum>2</manvolnum></citerefentry>. Note
 987                                 that a <varname>Personality=</varname>
 988                                 setting in the same unit file has no
 989                                 effect on this condition. A special
 990                                 architecture name
 991                                 <varname>native</varname> is mapped to
 992                                 the architecture the system manager
 993                                 itself is compiled for. The test may
 994                                 be negated by prepending an
 995                                 exclamation mark.</para>
 996
 997                                 <para><varname>ConditionVirtualization=</varname>
 998                                 may be used to check whether the
 999                                 system is executed in a virtualized
1000                                 environment and optionally test
1001                                 whether it is a specific
1002                                 implementation. Takes either boolean
1003                                 value to check if being executed in
1004                                 any virtualized environment, or one of
1005                                 <varname>vm</varname> and
1006                                 <varname>container</varname> to test
1007                                 against a generic type of
1008                                 virtualization solution, or one of
1009                                 <varname>qemu</varname>,
1010                                 <varname>kvm</varname>,
1011                                 <varname>zvm</varname>,
1012                                 <varname>vmware</varname>,
1013                                 <varname>microsoft</varname>,
1014                                 <varname>oracle</varname>,
1015                                 <varname>xen</varname>,
1016                                 <varname>bochs</varname>,
1017                                 <varname>uml</varname>,
1018                                 <varname>openvz</varname>,
1019                                 <varname>lxc</varname>,
1020                                 <varname>lxc-libvirt</varname>,
1021                                 <varname>systemd-nspawn</varname> to
1022                                 test against a specific
1023                                 implementation. If multiple
1024                                 virtualization technologies are nested,
1025                                 only the innermost is considered. The
1026                                 test may be negated by prepending an
1027                                 exclamation mark.</para>
1028
1029                                 <para><varname>ConditionHost=</varname>
1030                                 may be used to match against the
1031                                 hostname or machine ID of the
1032                                 host. This either takes a hostname
1033                                 string (optionally with shell style
1034                                 globs) which is tested against the
1035                                 locally set hostname as returned by
1036                                 <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
1037                                 or a machine ID formatted as string
1038                                 (see
1039                                 <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
1040                                 The test may be negated by prepending
1041                                 an exclamation mark.</para>
1042
1043                                 <para><varname>ConditionKernelCommandLine=</varname>
1044                                 may be used to check whether a
1045                                 specific kernel command line option is
1046                                 set (or if prefixed with the
1047                                 exclamation mark unset). The argument
1048                                 must either be a single word, or an
1049                                 assignment (i.e. two words, separated
1050                                 <literal>=</literal>). In the former
1051                                 case the kernel command line is
1052                                 searched for the word appearing as is,
1053                                 or as left hand side of an
1054                                 assignment. In the latter case, the
1055                                 exact assignment is looked for with
1056                                 right and left hand side
1057                                 matching.</para>
1058
1059                                 <para><varname>ConditionSecurity=</varname>
1060                                 may be used to check whether the given
1061                                 security module is enabled on the
1062                                 system. Currently the recognized values
1063                                 values are <varname>selinux</varname>,
1064                                 <varname>apparmor</varname>,
1065                                 <varname>ima</varname> and
1066                                 <varname>smack</varname>.
1067                                 The test may be negated by prepending
1068                                 an exclamation
1069                                 mark.</para>
1070
1071                                 <para><varname>ConditionCapability=</varname>
1072                                 may be used to check whether the given
1073                                 capability exists in the capability
1074                                 bounding set of the service manager
1075                                 (i.e. this does not check whether
1076                                 capability is actually available in
1077                                 the permitted or effective sets, see
1078                                 <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1079                                 for details). Pass a capability name
1080                                 such as <literal>CAP_MKNOD</literal>,
1081                                 possibly prefixed with an exclamation
1082                                 mark to negate the check.</para>
1083
1084                                 <para><varname>ConditionACPower=</varname>
1085                                 may be used to check whether the
1086                                 system has AC power, or is exclusively
1087                                 battery powered at the time of
1088                                 activation of the unit. This takes a
1089                                 boolean argument. If set to
1090                                 <varname>true</varname>, the condition
1091                                 will hold only if at least one AC
1092                                 connector of the system is connected
1093                                 to a power source, or if no AC
1094                                 connectors are known. Conversely, if
1095                                 set to <varname>false</varname>, the
1096                                 condition will hold only if there is
1097                                 at least one AC connector known and
1098                                 all AC connectors are disconnected
1099                                 from a power source.</para>
1100
1101                                 <para><varname>ConditionNeedsUpdate=</varname>
1102                                 takes one of <filename>/var</filename>
1103                                 or <filename>/etc</filename> as
1104                                 argument, possibly prefixed with a
1105                                 <literal>!</literal> (for inverting
1106                                 the condition). This condition may be
1107                                 used to conditionalize units on
1108                                 whether the specified directory
1109                                 requires an update because
1110                                 <filename>/usr</filename>'s
1111                                 modification time is newer than the
1112                                 stamp file
1113                                 <filename>.updated</filename> in the
1114                                 specified directory. This is useful to
1115                                 implement offline updates of the
1116                                 vendor operating system resources in
1117                                 <filename>/usr</filename> that require
1118                                 updating of <filename>/etc</filename>
1119                                 or <filename>/var</filename> on the
1120                                 next following boot. Units making use
1121                                 of this condition should order
1122                                 themselves before
1123                                 <citerefentry><refentrytitle>systemd-update-done.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1124                                 to make sure they run before the stamp
1125                                 files's modification time gets reset
1126                                 indicating a completed update.</para>
1127
1128                                 <para><varname>ConditionFirstBoot=</varname>
1129                                 takes a boolean argument. This
1130                                 condition may be used to
1131                                 conditionalize units on whether the
1132                                 system is booting up with an
1133                                 unpopulated <filename>/etc</filename>
1134                                 directory. This may be used to
1135                                 populate <filename>/etc</filename> on
1136                                 the first boot after factory reset, or
1137                                 when a new system instances boots up
1138                                 for the first time.</para>
1139
1140                                 <para>With
1141                                 <varname>ConditionPathExists=</varname>
1142                                 a file existence condition is
1143                                 checked before a unit is started. If
1144                                 the specified absolute path name does
1145                                 not exist, the condition will
1146                                 fail. If the absolute path name passed
1147                                 to
1148                                 <varname>ConditionPathExists=</varname>
1149                                 is prefixed with an exclamation mark
1150                                 (<literal>!</literal>), the test is negated, and the unit
1151                                 is only started if the path does not
1152                                 exist.</para>
1153
1154                                 <para><varname>ConditionPathExistsGlob=</varname>
1155                                 is similar to
1156                                 <varname>ConditionPathExists=</varname>,
1157                                 but checks for the existence of at
1158                                 least one file or directory matching
1159                                 the specified globbing pattern.</para>
1160
1161                                 <para><varname>ConditionPathIsDirectory=</varname>
1162                                 is similar to
1163                                 <varname>ConditionPathExists=</varname>
1164                                 but verifies whether a certain path
1165                                 exists and is a
1166                                 directory.</para>
1167
1168                                 <para><varname>ConditionPathIsSymbolicLink=</varname>
1169                                 is similar to
1170                                 <varname>ConditionPathExists=</varname>
1171                                 but verifies whether a certain path
1172                                 exists and is a symbolic
1173                                 link.</para>
1174
1175                                 <para><varname>ConditionPathIsMountPoint=</varname>
1176                                 is similar to
1177                                 <varname>ConditionPathExists=</varname>
1178                                 but verifies whether a certain path
1179                                 exists and is a mount
1180                                 point.</para>
1181
1182                                 <para><varname>ConditionPathIsReadWrite=</varname>
1183                                 is similar to
1184                                 <varname>ConditionPathExists=</varname>
1185                                 but verifies whether the underlying
1186                                 file system is readable and writable
1187                                 (i.e. not mounted
1188                                 read-only).</para>
1189
1190                                 <para><varname>ConditionDirectoryNotEmpty=</varname>
1191                                 is similar to
1192                                 <varname>ConditionPathExists=</varname>
1193                                 but verifies whether a certain path
1194                                 exists and is a non-empty
1195                                 directory.</para>
1196
1197                                 <para><varname>ConditionFileNotEmpty=</varname>
1198                                 is similar to
1199                                 <varname>ConditionPathExists=</varname>
1200                                 but verifies whether a certain path
1201                                 exists and refers to a regular file
1202                                 with a non-zero size.</para>
1203
1204                                 <para><varname>ConditionFileIsExecutable=</varname>
1205                                 is similar to
1206                                 <varname>ConditionPathExists=</varname>
1207                                 but verifies whether a certain path
1208                                 exists, is a regular file and marked
1209                                 executable.</para>
1210
1211                                 <para>Finally,
1212                                 <varname>ConditionNull=</varname> may
1213                                 be used to add a constant condition
1214                                 check value to the unit. It takes a
1215                                 boolean argument. If set to
1216                                 <varname>false</varname>, the condition
1217                                 will always fail, otherwise
1218                                 succeed.</para>
1219
1220                                 <para>If multiple conditions are
1221                                 specified, the unit will be executed if
1222                                 all of them apply (i.e. a logical AND
1223                                 is applied). Condition checks can be
1224                                 prefixed with a pipe symbol (|) in
1225                                 which case a condition becomes a
1226                                 triggering condition. If at least one
1227                                 triggering condition is defined for a
1228                                 unit, then the unit will be executed if
1229                                 at least one of the triggering
1230                                 conditions apply and all of the
1231                                 non-triggering conditions. If you
1232                                 prefix an argument with the pipe
1233                                 symbol and an exclamation mark, the
1234                                 pipe symbol must be passed first, the
1235                                 exclamation second. Except for
1236                                 <varname>ConditionPathIsSymbolicLink=</varname>,
1237                                 all path checks follow symlinks. If
1238                                 any of these options is assigned the
1239                                 empty string, the list of conditions is
1240                                 reset completely, all previous
1241                                 condition settings (of any kind) will
1242                                 have no effect.</para></listitem>
1243                         </varlistentry>
1244
1245                         <varlistentry>
1246                                 <term><varname>SourcePath=</varname></term>
1247                                 <listitem><para>A path to a
1248                                 configuration file this unit has been
1249                                 generated from. This is primarily
1250                                 useful for implementation of generator
1251                                 tools that convert configuration from
1252                                 an external configuration file format
1253                                 into native unit files. This
1254                                 functionality should not be used in
1255                                 normal units.</para></listitem>
1256                         </varlistentry>
1257                 </variablelist>
1258
1259         </refsect1>
1260
1261         <refsect1>
1262                 <title>[Install] Section Options</title>
1263
1264                 <para>Unit file may include an
1265                 <literal>[Install]</literal> section, which carries
1266                 installation information for the unit. This section is
1267                 not interpreted by
1268                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1269                 during runtime. It is used exclusively by the
1270                 <command>enable</command> and
1271                 <command>disable</command> commands of the
1272                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1273                 tool during installation of a unit:</para>
1274
1275                 <variablelist class='unit-directives'>
1276                         <varlistentry>
1277                                 <term><varname>Alias=</varname></term>
1278
1279                                 <listitem><para>A space-separated list
1280                                 of additional names this unit shall be
1281                                 installed under. The names listed here
1282                                 must have the same suffix (i.e. type)
1283                                 as the unit file name. This option may
1284                                 be specified more than once, in which
1285                                 case all listed names are used. At
1286                                 installation time, <command>systemctl
1287                                 enable</command> will create symlinks
1288                                 from these names to the unit
1289                                 filename.</para></listitem>
1290                         </varlistentry>
1291
1292                         <varlistentry>
1293                                 <term><varname>WantedBy=</varname></term>
1294                                 <term><varname>RequiredBy=</varname></term>
1295
1296                                 <listitem><para>This option may be
1297                                 used more than once, or a
1298                                 space-separated list of unit names may
1299                                 be given. A symbolic link is created
1300                                 in the <filename>.wants/</filename> or
1301                                 <filename>.requires/</filename>
1302                                 directory of each of the listed units
1303                                 when this unit is installed by
1304                                 <command>systemctl enable</command>.
1305                                 This has the effect that a dependency
1306                                 of type <varname>Wants=</varname> or
1307                                 <varname>Requires=</varname> is added
1308                                 from the listed unit to the current
1309                                 unit. The primary result is that the
1310                                 current unit will be started when the
1311                                 listed unit is started. See the
1312                                 description of
1313                                 <varname>Wants=</varname> and
1314                                 <varname>Requires=</varname> in the
1315                                 [Unit] section for details.</para>
1316
1317                                 <para><command>WantedBy=foo.service</command>
1318                                 in a service
1319                                 <filename>bar.service</filename> is
1320                                 mostly equivalent to
1321                                 <command>Alias=foo.service.wants/bar.service</command>
1322                                 in the same file. In case of template
1323                                 units, <command>systemctl enable</command>
1324                                 must be called with an instance name, and
1325                                 this instance will be added to the
1326                                 <filename>.wants/</filename> or
1327                                 <filename>.requires/</filename> list
1328                                 of the listed unit.
1329                                 E.g. <command>WantedBy=getty.target</command>
1330                                 in a service
1331                                 <filename>getty@.service</filename>
1332                                 will result in <command>systemctl
1333                                 enable getty@tty2.service</command>
1334                                 creating a
1335                                 <filename>getty.target.wants/getty@tty2.service</filename>
1336                                 link to <filename>getty@.service</filename>.
1337                                 </para></listitem>
1338                         </varlistentry>
1339
1340                         <varlistentry>
1341                                 <term><varname>Also=</varname></term>
1342
1343                                 <listitem><para>Additional units to
1344                                 install/deinstall when this unit is
1345                                 installed/deinstalled. If the user
1346                                 requests installation/deinstallation
1347                                 of a unit with this option configured,
1348                                 <command>systemctl enable</command>
1349                                 and <command>systemctl
1350                                 disable</command> will automatically
1351                                 install/uninstall units listed in this option as
1352                                 well.</para>
1353
1354                                 <para>This option may be used more
1355                                 than once, or a space-separated list
1356                                 of unit names may be
1357                                 given.</para></listitem>
1358                         </varlistentry>
1359
1360                         <varlistentry>
1361                                 <term><varname>DefaultInstance=</varname></term>
1362
1363                                 <listitem><para>In template unit files,
1364                                 this specifies for which instance the
1365                                 unit shall be enabled if the template
1366                                 is enabled without any explicitly set
1367                                 instance. This option has no effect in
1368                                 non-template unit files. The specified
1369                                 string must be usable as instance
1370                                 identifier.</para></listitem>
1371                         </varlistentry>
1372                 </variablelist>
1373
1374                 <para>The following specifiers are interpreted in the
1375                 Install section: %n, %N, %p, %i, %U, %u, %m, %H, %b, %v.
1376                 For their meaning see the next section.
1377                 </para>
1378         </refsect1>
1379
1380         <refsect1>
1381                 <title>Specifiers</title>
1382
1383                 <para>Many settings resolve specifiers which may be
1384                 used to write generic unit files referring to runtime
1385                 or unit parameters that are replaced when the unit
1386                 files are loaded. The following specifiers are
1387                 understood:</para>
1388
1389                 <table>
1390                   <title>Specifiers available in unit files</title>
1391                   <tgroup cols='3' align='left' colsep='1' rowsep='1'>
1392                     <colspec colname="spec" />
1393                     <colspec colname="mean" />
1394                     <colspec colname="detail" />
1395                     <thead>
1396                       <row>
1397                         <entry>Specifier</entry>
1398                         <entry>Meaning</entry>
1399                         <entry>Details</entry>
1400                       </row>
1401                     </thead>
1402                     <tbody>
1403                       <row>
1404                         <entry><literal>%n</literal></entry>
1405                         <entry>Full unit name</entry>
1406                         <entry></entry>
1407                       </row>
1408                       <row>
1409                         <entry><literal>%N</literal></entry>
1410                         <entry>Unescaped full unit name</entry>
1411                         <entry>Same as <literal>%n</literal>, but with escaping undone</entry>
1412                       </row>
1413                       <row>
1414                         <entry><literal>%p</literal></entry>
1415                         <entry>Prefix name</entry>
1416                         <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>
1417                       </row>
1418                       <row>
1419                         <entry><literal>%P</literal></entry>
1420                         <entry>Unescaped prefix name</entry>
1421                         <entry>Same as <literal>%p</literal>, but with escaping undone</entry>
1422                       </row>
1423                       <row>
1424                         <entry><literal>%i</literal></entry>
1425                         <entry>Instance name</entry>
1426                         <entry>For instantiated units: this is the string between the <literal>@</literal> character and the suffix of the unit name.</entry>
1427                       </row>
1428                       <row>
1429                         <entry><literal>%I</literal></entry>
1430                         <entry>Unescaped instance name</entry>
1431                         <entry>Same as <literal>%i</literal>, but with escaping undone</entry>
1432                       </row>
1433                       <row>
1434                         <entry><literal>%f</literal></entry>
1435                         <entry>Unescaped filename</entry>
1436                         <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>
1437                       </row>
1438                       <row>
1439                         <entry><literal>%c</literal></entry>
1440                         <entry>Control group path of the unit</entry>
1441                         <entry>This path does not include the <filename>/sys/fs/cgroup/systemd/</filename> prefix.</entry>
1442                       </row>
1443                       <row>
1444                         <entry><literal>%r</literal></entry>
1445                         <entry>Control group path of the slice the unit is placed in</entry>
1446                         <entry>This usually maps to the parent cgroup path of <literal>%c</literal>.</entry>
1447                       </row>
1448                       <row>
1449                         <entry><literal>%R</literal></entry>
1450                         <entry>Root control group path below which slices and units are placed</entry>
1451                         <entry>For system instances, this resolves to <filename>/</filename>, except in containers, where this maps to the container's root control group path.</entry>
1452                       </row>
1453                       <row>
1454                         <entry><literal>%t</literal></entry>
1455                         <entry>Runtime directory</entry>
1456                         <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>
1457                       </row>
1458                       <row>
1459                         <entry><literal>%u</literal></entry>
1460                         <entry>User name</entry>
1461                         <entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
1462                       </row>
1463                       <row>
1464                         <entry><literal>%U</literal></entry>
1465                         <entry>User UID</entry>
1466                         <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>
1467                       </row>
1468                       <row>
1469                         <entry><literal>%h</literal></entry>
1470                         <entry>User home directory</entry>
1471                         <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>
1472                       </row>
1473                       <row>
1474                         <entry><literal>%s</literal></entry>
1475                         <entry>User shell</entry>
1476                         <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>
1477                       </row>
1478                       <row>
1479                         <entry><literal>%m</literal></entry>
1480                         <entry>Machine ID</entry>
1481                         <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>
1482                       </row>
1483                       <row>
1484                         <entry><literal>%b</literal></entry>
1485                         <entry>Boot ID</entry>
1486                         <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
1487                       </row>
1488                       <row>
1489                         <entry><literal>%H</literal></entry>
1490                         <entry>Host name</entry>
1491                         <entry>The hostname of the running system at the point in time the unit configuation is loaded.</entry>
1492                       </row>
1493                       <row>
1494                         <entry><literal>%v</literal></entry>
1495                         <entry>Kernel release</entry>
1496                         <entry>Identical to <command>uname -r</command> output</entry>
1497                       </row>
1498                       <row>
1499                         <entry><literal>%%</literal></entry>
1500                         <entry>Single percent sign</entry>
1501                         <entry>Use <literal>%%</literal> in place of <literal>%</literal> to specify a single percent sign.</entry>
1502                       </row>
1503                     </tbody>
1504                   </tgroup>
1505                 </table>
1506         </refsect1>
1507
1508         <refsect1>
1509                 <title>See Also</title>
1510                 <para>
1511                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1512                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1513                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1514                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1515                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1516                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1517                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1518                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1519                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1520                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1521                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1522                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1523                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1524                         <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1525                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1526                         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1527                         <citerefentry><refentrytitle>systemd-verify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1528                         <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1529                         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1530                         <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1531                 </para>
1532         </refsect1>
1533
1534 </refentry>