man/systemd.unit.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="systemd.unit">
  25
  26         <refentryinfo>
  27                 <title>systemd.unit</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.unit</refentrytitle>
  42                 <manvolnum>5</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.unit</refname>
  47                 <refpurpose>systemd unit configuration files</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename>systemd.service</filename>,
  52                 <filename>systemd.socket</filename>,
  53                 <filename>systemd.device</filename>,
  54                 <filename>systemd.mount</filename>,
  55                 <filename>systemd.automount</filename>,
  56                 <filename>systemd.swap</filename>,
  57                 <filename>systemd.target</filename>,
  58                 <filename>systemd.path</filename>,
  59                 <filename>systemd.timer</filename>,
  60                 <filename>systemd.snapshot</filename></para>
  61         </refsynopsisdiv>
  62
  63         <refsect1>
  64                 <title>Description</title>
  65
  66                 <para>A unit configuration file encodes information
  67                 about a service, a socket, a device, a mount point, an
  68                 automount point, a swap file or partition, a start-up
  69                 target, a file system path or a timer controlled and
  70                 supervised by
  71                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>. The
  72                 syntax is inspired by <ulink
  73                 url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
  74                 Desktop Entry Specification</ulink> <filename>.desktop</filename> files, which are in turn
  75                 inspired by Microsoft Windows
  76                 <filename>.ini</filename> files.</para>
  77
  78                 <para>This man pages lists the common configuration
  79                 options of all the unit types. These options need to
  80                 be configured in the [Unit] resp. [Install]
  81                 section of the unit files.</para>
  82
  83                 <para>In addition to the generic [Unit] and [Install]
  84                 sections described here, each unit should have a
  85                 type-specific section, e.g. [Service] for a service
  86                 unit. See the respective man pages for more
  87                 information.</para>
  88
  89                 <para>Unit files may contain additional options on top
  90                 of those listed here. If systemd encounters an unknown
  91                 option it will write a warning log message but
  92                 continue loading the unit. If an option is prefixed
  93                 with <option>X-</option> it is ignored completely by
  94                 systemd. Applications may use this to include
  95                 additional information in the unit files.</para>
  96
  97                 <para>Boolean arguments used in unit files can be
  98                 written in various formats. For positive settings the
  99                 strings <option>1</option>, <option>yes</option>,
 100                 <option>true</option> and <option>on</option> are
 101                 equivalent. For negative settings the strings
 102                 <option>0</option>, <option>no</option>,
 103                 <option>false</option> and <option>off</option> are
 104                 equivalent.</para>
 105
 106                 <para>Time span values encoded in unit files can be
 107                 written in various formats. A stand-alone number
 108                 specifies a time in seconds. If suffixed with a time
 109                 unit, the unit is honored. A concatenation of
 110                 multiple values with units is supported, in which case
 111                 the values are added up. Example: "50" refers to 50
 112                 seconds; "2min 200ms" refers to 2 minutes plus 200
 113                 milliseconds, i.e. 120200ms. The following time units
 114                 are understood: s, min, h, d, w, ms, us.</para>
 115
 116                 <para>Empty lines and lines starting with # or ; are
 117                 ignored. This may be used for commenting. Lines ending
 118                 in a backslash are concatenated with the following
 119                 line while reading and the backslash is replaced by a
 120                 space character. This may be used to wrap long lines.</para>
 121
 122                 <para>If a line starts with <option>.include</option>
 123                 followed by a file name, the specified file will be
 124                 parsed at this point. Make sure that the file that is
 125                 included has the appropriate section headers before
 126                 any directives.</para>
 127
 128                 <para>Along with a unit file
 129                 <filename>foo.service</filename> a directory
 130                 <filename>foo.service.wants/</filename> may exist. All
 131                 units symlinked from such a directory are implicitly
 132                 added as dependencies of type
 133                 <varname>Wanted=</varname> to the unit. This is useful
 134                 to hook units into the start-up of other units,
 135                 without having to modify their unit configuration
 136                 files. For details about the semantics of
 137                 <varname>Wanted=</varname> see below. The preferred
 138                 way to create symlinks in the
 139                 <filename>.wants/</filename> directory of a service is
 140                 with the <command>enable</command> command of the
 141                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 142                 tool which reads information from the [Install]
 143                 section of unit files. (See below.) A similar
 144                 functionality exists for <varname>Requires=</varname>
 145                 type dependencies as well, the directory suffix is
 146                 <filename>.requires/</filename> in this case.</para>
 147
 148                 <para>Note that while systemd offers a flexible
 149                 dependency system between units it is recommended to
 150                 use this functionality only sparsely and instead rely
 151                 on techniques such as bus-based or socket-based
 152                 activation which makes dependencies implicit, which
 153                 both results in a simpler and more flexible
 154                 system.</para>
 155
 156                 <para>Some unit names reflect paths existing in the
 157                 file system name space. Example: a device unit
 158                 <filename>dev-sda.device</filename> refers to a device
 159                 with the device node <filename>/dev/sda</filename> in
 160                 the file system namespace. If this applies a special
 161                 way to escape the path name is used, so that the
 162                 result is usable as part of a file name. Basically,
 163                 given a path, "/" is replaced by "-", and all
 164                 unprintable characters and the "-" are replaced by
 165                 C-style "\x20" escapes. The root directory "/" is
 166                 encoded as single dash, while otherwise the initial
 167                 and ending "/" is removed from all paths during
 168                 transformation. This escaping is reversible.</para>
 169
 170                 <para>Optionally, units may be instantiated from a
 171                 template file at runtime. This allows creation of
 172                 multiple units from a single configuration file. If
 173                 systemd looks for a unit configuration file it will
 174                 first search for the literal unit name in the
 175                 filesystem. If that yields no success and the unit
 176                 name contains an @ character, systemd will look for a
 177                 unit template that shares the same name but with the
 178                 instance string (i.e. the part between the @ character
 179                 and the suffix) removed. Example: if a service
 180                 <filename>getty@tty3.service</filename> is requested
 181                 and no file by that name is found, systemd will look
 182                 for <filename>getty@.service</filename> and
 183                 instantiate a service from that configuration file if
 184                 it is found.</para>
 185
 186                 <para>To refer to the instance string from
 187                 within the configuration file you may use the special
 188                 <literal>%i</literal> specifier in many of the
 189                 configuration options. Other specifiers exist, the
 190                 full list is:</para>
 191
 192                 <table>
 193                   <title>Specifiers available in unit files</title>
 194                   <tgroup cols='3' align='left' colsep='1' rowsep='1'>
 195                     <colspec colname="spec" />
 196                     <colspec colname="mean" />
 197                     <colspec colname="detail" />
 198                     <thead>
 199                       <row>
 200                         <entry>Specifier</entry>
 201                         <entry>Meaning</entry>
 202                         <entry>Details</entry>
 203                       </row>
 204                     </thead>
 205                     <tbody>
 206                       <row>
 207                         <entry><literal>%n</literal></entry>
 208                         <entry>Full unit name</entry>
 209                         <entry></entry>
 210                       </row>
 211                       <row>
 212                         <entry><literal>%N</literal></entry>
 213                         <entry>Unescaped full unit name</entry>
 214                         <entry></entry>
 215                       </row>
 216                       <row>
 217                         <entry><literal>%p</literal></entry>
 218                         <entry>Prefix name</entry>
 219                         <entry>This refers to the string before the @, i.e. "getty" in the example above, where "tty3" is the instance name.</entry>
 220                       </row>
 221                       <row>
 222                         <entry><literal>%P</literal></entry>
 223                         <entry>Unescaped prefix name</entry>
 224                         <entry></entry>
 225                       </row>
 226                       <row>
 227                         <entry><literal>%i</literal></entry>
 228                         <entry>Instance name</entry>
 229                         <entry>This is the string between the @ character and the suffix.</entry>
 230                       </row>
 231                       <row>
 232                         <entry><literal>%I</literal></entry>
 233                         <entry>Unescaped instance name</entry>
 234                         <entry></entry>
 235                       </row>
 236                       <row>
 237                         <entry><literal>%f</literal></entry>
 238                         <entry>Unescaped file name</entry>
 239                         <entry>This is either the unescaped instance name (if set) with / prepended (if necessary), or the prefix name similarly prepended with /.</entry>
 240                       </row>
 241                       <row>
 242                         <entry><literal>%c</literal></entry>
 243                         <entry>Control group path of the unit</entry>
 244                         <entry></entry>
 245                       </row>
 246                       <row>
 247                         <entry><literal>%r</literal></entry>
 248                         <entry>Root control group path of systemd</entry>
 249                         <entry></entry>
 250                       </row>
 251                       <row>
 252                         <entry><literal>%R</literal></entry>
 253                         <entry>Parent directory of the root control group path of systemd</entry>
 254                         <entry></entry>
 255                       </row>
 256                       <row>
 257                         <entry><literal>%t</literal></entry>
 258                         <entry>Runtime socket dir</entry>
 259                         <entry>This is either /run (for the system manager) or $XDG_RUNTIME_DIR (for user managers).</entry>
 260                       </row>
 261                       <row>
 262                         <entry><literal>%u</literal></entry>
 263                         <entry>User name</entry>
 264                         <entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
 265                       </row>
 266                       <row>
 267                         <entry><literal>%h</literal></entry>
 268                         <entry>User home directory</entry>
 269                         <entry>This is the home directory of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
 270                       </row>
 271                     </tbody>
 272                   </tgroup>
 273                 </table>
 274
 275                 <para>If a unit file is empty (i.e. has the file size
 276                 0) or is symlinked to <filename>/dev/null</filename>
 277                 its configuration will not be loaded and it appears
 278                 with a load state of <literal>masked</literal>, and
 279                 cannot be activated. Use this as an effective way to
 280                 fully disable a unit, making it impossible to start it
 281                 even manually.</para>
 282
 283                 <para>The unit file format is covered by the
 284                 <ulink
 285                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 286                 Stability Promise</ulink>.</para>
 287         </refsect1>
 288
 289         <refsect1>
 290                 <title>Options</title>
 291
 292                 <para>Unit file may include a [Unit] section, which
 293                 carries generic information about the unit that is not
 294                 dependent on the type of unit:</para>
 295
 296                 <variablelist>
 297
 298                         <varlistentry>
 299                                 <term><varname>Description=</varname></term>
 300                                 <listitem><para>A free-form string
 301                                 describing the unit. This is intended
 302                                 for use in UIs to show descriptive
 303                                 information along with the unit
 304                                 name.</para></listitem>
 305                         </varlistentry>
 306
 307                         <varlistentry>
 308                                 <term><varname>Documentation=</varname></term>
 309                                 <listitem><para>A space separated list
 310                                 of URIs referencing documentation for
 311                                 this unit or its
 312                                 configuration. Accepted are only URIs
 313                                 of the types
 314                                 <literal>http://</literal>,
 315                                 <literal>https://</literal>,
 316                                 <literal>file:</literal>,
 317                                 <literal>info:</literal>,
 318                                 <literal>man:</literal>. For more
 319                                 information about the syntax of these
 320                                 URIs see
 321                                 <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
 322                         </varlistentry>
 323
 324                         <varlistentry>
 325                                 <term><varname>Requires=</varname></term>
 326
 327                                 <listitem><para>Configures requirement
 328                                 dependencies on other units. If this
 329                                 unit gets activated, the units listed
 330                                 here will be activated as well. If one
 331                                 of the other units gets deactivated or
 332                                 its activation fails, this unit will
 333                                 be deactivated. This option may be
 334                                 specified more than once, in which
 335                                 case requirement dependencies for all
 336                                 listed names are created. Note that
 337                                 requirement dependencies do not
 338                                 influence the order in which services
 339                                 are started or stopped. This has to be
 340                                 configured independently with the
 341                                 <varname>After=</varname> or
 342                                 <varname>Before=</varname> options. If
 343                                 a unit
 344                                 <filename>foo.service</filename>
 345                                 requires a unit
 346                                 <filename>bar.service</filename> as
 347                                 configured with
 348                                 <varname>Requires=</varname> and no
 349                                 ordering is configured with
 350                                 <varname>After=</varname> or
 351                                 <varname>Before=</varname>, then both
 352                                 units will be started simultaneously
 353                                 and without any delay between them if
 354                                 <filename>foo.service</filename> is
 355                                 activated. Often it is a better choice
 356                                 to use <varname>Wants=</varname>
 357                                 instead of
 358                                 <varname>Requires=</varname> in order
 359                                 to achieve a system that is more
 360                                 robust when dealing with failing
 361                                 services.</para></listitem>
 362                         </varlistentry>
 363
 364                         <varlistentry>
 365                                 <term><varname>RequiresOverridable=</varname></term>
 366
 367                                 <listitem><para>Similar to
 368                                 <varname>Requires=</varname>.
 369                                 Dependencies listed in
 370                                 <varname>RequiresOverridable=</varname>
 371                                 which cannot be fulfilled or fail to
 372                                 start are ignored if the startup was
 373                                 explicitly requested by the user. If
 374                                 the start-up was pulled in indirectly
 375                                 by some dependency or automatic
 376                                 start-up of units that is not
 377                                 requested by the user this dependency
 378                                 must be fulfilled and otherwise the
 379                                 transaction fails. Hence, this option
 380                                 may be used to configure dependencies
 381                                 that are normally honored unless the
 382                                 user explicitly starts up the unit, in
 383                                 which case whether they failed or not
 384                                 is irrelevant.</para></listitem>
 385
 386                         </varlistentry>
 387                         <varlistentry>
 388                                 <term><varname>Requisite=</varname></term>
 389                                 <term><varname>RequisiteOverridable=</varname></term>
 390
 391                                 <listitem><para>Similar to
 392                                 <varname>Requires=</varname>
 393                                 resp. <varname>RequiresOverridable=</varname>. However,
 394                                 if a unit listed here is not started
 395                                 already it will not be started and the
 396                                 transaction fails
 397                                 immediately.</para></listitem>
 398                         </varlistentry>
 399
 400                         <varlistentry>
 401                                 <term><varname>Wants=</varname></term>
 402
 403                                 <listitem><para>A weaker version of
 404                                 <varname>Requires=</varname>. A unit
 405                                 listed in this option will be started
 406                                 if the configuring unit is. However,
 407                                 if the listed unit fails to start up
 408                                 or cannot be added to the transaction
 409                                 this has no impact on the validity of
 410                                 the transaction as a whole. This is
 411                                 the recommended way to hook start-up
 412                                 of one unit to the start-up of another
 413                                 unit. Note that dependencies of this
 414                                 type may also be configured outside of
 415                                 the unit configuration file by
 416                                 adding a symlink to a
 417                                 <filename>.wants/</filename> directory
 418                                 accompanying the unit file. For
 419                                 details see above.</para></listitem>
 420                         </varlistentry>
 421
 422                         <varlistentry>
 423                                 <term><varname>BindsTo=</varname></term>
 424
 425                                 <listitem><para>Configures requirement
 426                                 dependencies, very similar in style to
 427                                 <varname>Requires=</varname>, however
 428                                 in addition to this behaviour it also
 429                                 declares that this unit is stopped
 430                                 when any of the units listed suddenly
 431                                 disappears. Units can suddenly,
 432                                 unexpectedly disappear if a service
 433                                 terminates on its own choice, a device
 434                                 is unplugged or a mount point
 435                                 unmounted without involvement of
 436                                 systemd.</para></listitem>
 437                         </varlistentry>
 438
 439                         <varlistentry>
 440                                 <term><varname>Conflicts=</varname></term>
 441
 442                                 <listitem><para>Configures negative
 443                                 requirement dependencies. If a unit
 444                                 has a
 445                                 <varname>Conflicts=</varname> setting
 446                                 on another unit, starting the former
 447                                 will stop the latter and vice
 448                                 versa. Note that this setting is
 449                                 independent of and orthogonal to the
 450                                 <varname>After=</varname> and
 451                                 <varname>Before=</varname> ordering
 452                                 dependencies.</para>
 453
 454                                 <para>If a unit A that conflicts with
 455                                 a unit B is scheduled to be started at
 456                                 the same time as B, the transaction
 457                                 will either fail (in case both are
 458                                 required part of the transaction) or
 459                                 be modified to be fixed (in case one
 460                                 or both jobs are not a required part
 461                                 of the transaction). In the latter
 462                                 case the job that is not the required
 463                                 will be removed, or in case both are
 464                                 not required the unit that conflicts
 465                                 will be started and the unit that is
 466                                 conflicted is
 467                                 stopped.</para></listitem>
 468                         </varlistentry>
 469
 470                         <varlistentry>
 471                                 <term><varname>Before=</varname></term>
 472                                 <term><varname>After=</varname></term>
 473
 474                                 <listitem><para>Configures ordering
 475                                 dependencies between units. If a unit
 476                                 <filename>foo.service</filename>
 477                                 contains a setting
 478                                 <option>Before=bar.service</option>
 479                                 and both units are being started,
 480                                 <filename>bar.service</filename>'s
 481                                 start-up is delayed until
 482                                 <filename>foo.service</filename> is
 483                                 started up. Note that this setting is
 484                                 independent of and orthogonal to the
 485                                 requirement dependencies as configured
 486                                 by <varname>Requires=</varname>. It is
 487                                 a common pattern to include a unit
 488                                 name in both the
 489                                 <varname>After=</varname> and
 490                                 <varname>Requires=</varname> option in
 491                                 which case the unit listed will be
 492                                 started before the unit that is
 493                                 configured with these options. This
 494                                 option may be specified more than
 495                                 once, in which case ordering
 496                                 dependencies for all listed names are
 497                                 created. <varname>After=</varname> is
 498                                 the inverse of
 499                                 <varname>Before=</varname>, i.e. while
 500                                 <varname>After=</varname> ensures that
 501                                 the configured unit is started after
 502                                 the listed unit finished starting up,
 503                                 <varname>Before=</varname> ensures the
 504                                 opposite, i.e.  that the configured
 505                                 unit is fully started up before the
 506                                 listed unit is started. Note that when
 507                                 two units with an ordering dependency
 508                                 between them are shut down, the
 509                                 inverse of the start-up order is
 510                                 applied. i.e. if a unit is configured
 511                                 with <varname>After=</varname> on
 512                                 another unit, the former is stopped
 513                                 before the latter if both are shut
 514                                 down. If one unit with an ordering
 515                                 dependency on another unit is shut
 516                                 down while the latter is started up,
 517                                 the shut down is ordered before the
 518                                 start-up regardless whether the
 519                                 ordering dependency is actually of
 520                                 type <varname>After=</varname> or
 521                                 <varname>Before=</varname>. If two
 522                                 units have no ordering dependencies
 523                                 between them they are shut down
 524                                 resp. started up simultaneously, and
 525                                 no ordering takes
 526                                 place. </para></listitem>
 527                         </varlistentry>
 528
 529                         <varlistentry>
 530                                 <term><varname>OnFailure=</varname></term>
 531
 532                                 <listitem><para>Lists one or more
 533                                 units that are activated when this
 534                                 unit enters the
 535                                 '<literal>failed</literal>'
 536                                 state.</para></listitem>
 537                         </varlistentry>
 538
 539                         <varlistentry>
 540                                 <term><varname>PropagatesReloadTo=</varname></term>
 541                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 542
 543                                 <listitem><para>Lists one or more
 544                                 units where reload requests on the
 545                                 unit will be propagated to/on the
 546                                 other unit will be propagated
 547                                 from. Issuing a reload request on a
 548                                 unit will automatically also enqueue a
 549                                 reload request on all units that the
 550                                 reload request shall be propagated to
 551                                 via these two
 552                                 settings.</para></listitem>
 553                         </varlistentry>
 554
 555                         <varlistentry>
 556                                 <term><varname>RequiresMountsFor=</varname></term>
 557
 558                                 <listitem><para>Takes a space
 559                                 separated list of paths. Automatically
 560                                 adds dependencies of type
 561                                 <varname>Requires=</varname> and
 562                                 <varname>After=</varname> for all
 563                                 mount units required to access the
 564                                 specified path.</para></listitem>
 565                         </varlistentry>
 566
 567                         <varlistentry>
 568                                 <term><varname>OnFailureIsolate=</varname></term>
 569
 570                                 <listitem><para>Takes a boolean
 571                                 argument. If <option>true</option> the
 572                                 unit listed in
 573                                 <varname>OnFailure=</varname> will be
 574                                 enqueued in isolation mode, i.e. all
 575                                 units that are not its dependency will
 576                                 be stopped. If this is set only a
 577                                 single unit may be listed in
 578                                 <varname>OnFailure=</varname>. Defaults
 579                                 to
 580                                 <option>false</option>.</para></listitem>
 581                         </varlistentry>
 582
 583                         <varlistentry>
 584                                 <term><varname>IgnoreOnIsolate=</varname></term>
 585
 586                                 <listitem><para>Takes a boolean
 587                                 argument. If <option>true</option>
 588                                 this unit will not be stopped when
 589                                 isolating another unit. Defaults to
 590                                 <option>false</option>.</para></listitem>
 591                         </varlistentry>
 592
 593                         <varlistentry>
 594                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 595
 596                                 <listitem><para>Takes a boolean
 597                                 argument. If <option>true</option>
 598                                 this unit will not be included in
 599                                 snapshots. Defaults to
 600                                 <option>true</option> for device and
 601                                 snapshot units, <option>false</option>
 602                                 for the others.</para></listitem>
 603                         </varlistentry>
 604
 605                         <varlistentry>
 606                                 <term><varname>StopWhenUnneeded=</varname></term>
 607
 608                                 <listitem><para>Takes a boolean
 609                                 argument. If <option>true</option>
 610                                 this unit will be stopped when it is
 611                                 no longer used. Note that in order to
 612                                 minimize the work to be executed,
 613                                 systemd will not stop units by default
 614                                 unless they are conflicting with other
 615                                 units, or the user explicitly
 616                                 requested their shut down. If this
 617                                 option is set, a unit will be
 618                                 automatically cleaned up if no other
 619                                 active unit requires it. Defaults to
 620                                 <option>false</option>.</para></listitem>
 621                         </varlistentry>
 622
 623                         <varlistentry>
 624                                 <term><varname>RefuseManualStart=</varname></term>
 625                                 <term><varname>RefuseManualStop=</varname></term>
 626
 627                                 <listitem><para>Takes a boolean
 628                                 argument. If <option>true</option>
 629                                 this unit can only be activated
 630                                 (resp. deactivated) indirectly. In
 631                                 this case explicit start-up
 632                                 (resp. termination) requested by the
 633                                 user is denied, however if it is
 634                                 started (resp. stopped) as a
 635                                 dependency of another unit, start-up
 636                                 (resp. termination) will succeed. This
 637                                 is mostly a safety feature to ensure
 638                                 that the user does not accidentally
 639                                 activate units that are not intended
 640                                 to be activated explicitly, and not
 641                                 accidentally deactivate units that are
 642                                 not intended to be deactivated.
 643                                 These options default to
 644                                 <option>false</option>.</para></listitem>
 645                         </varlistentry>
 646
 647                         <varlistentry>
 648                                 <term><varname>AllowIsolate=</varname></term>
 649
 650                                 <listitem><para>Takes a boolean
 651                                 argument. If <option>true</option>
 652                                 this unit may be used with the
 653                                 <command>systemctl isolate</command>
 654                                 command. Otherwise this will be
 655                                 refused. It probably is a good idea to
 656                                 leave this disabled except for target
 657                                 units that shall be used similar to
 658                                 runlevels in SysV init systems, just
 659                                 as a precaution to avoid unusable
 660                                 system states. This option defaults to
 661                                 <option>false</option>.</para></listitem>
 662                         </varlistentry>
 663
 664                         <varlistentry>
 665                                 <term><varname>DefaultDependencies=</varname></term>
 666
 667                                 <listitem><para>Takes a boolean
 668                                 argument. If <option>true</option>
 669                                 (the default), a few default
 670                                 dependencies will implicitly be
 671                                 created for the unit. The actual
 672                                 dependencies created depend on the
 673                                 unit type. For example, for service
 674                                 units, these dependencies ensure that
 675                                 the service is started only after
 676                                 basic system initialization is
 677                                 completed and is properly terminated on
 678                                 system shutdown. See the respective
 679                                 man pages for details. Generally, only
 680                                 services involved with early boot or
 681                                 late shutdown should set this option
 682                                 to <option>false</option>. It is
 683                                 highly recommended to leave this
 684                                 option enabled for the majority of
 685                                 common units. If set to
 686                                 <option>false</option> this option
 687                                 does not disable all implicit
 688                                 dependencies, just non-essential
 689                                 ones.</para></listitem>
 690                         </varlistentry>
 691
 692                         <varlistentry>
 693                                 <term><varname>JobTimeoutSec=</varname></term>
 694
 695                                 <listitem><para>When clients are
 696                                 waiting for a job of this unit to
 697                                 complete, time out after the specified
 698                                 time. If this time limit is reached
 699                                 the job will be cancelled, the unit
 700                                 however will not change state or even
 701                                 enter the '<literal>failed</literal>'
 702                                 mode. This value defaults to 0 (job
 703                                 timeouts disabled), except for device
 704                                 units. NB: this timeout is independent
 705                                 from any unit-specific timeout (for
 706                                 example, the timeout set with
 707                                 <varname>Timeout=</varname> in service
 708                                 units) as the job timeout has no
 709                                 effect on the unit itself, only on the
 710                                 job that might be pending for it. Or
 711                                 in other words: unit-specific timeouts
 712                                 are useful to abort unit state
 713                                 changes, and revert them. The job
 714                                 timeout set with this option however
 715                                 is useful to abort only the job
 716                                 waiting for the unit state to
 717                                 change.</para></listitem>
 718                         </varlistentry>
 719
 720                         <varlistentry>
 721                                 <term><varname>ConditionPathExists=</varname></term>
 722                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 723                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 724                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 725                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 726                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 727                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 728                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 729                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 730                                 <term><varname>ConditionVirtualization=</varname></term>
 731                                 <term><varname>ConditionSecurity=</varname></term>
 732                                 <term><varname>ConditionCapability=</varname></term>
 733                                 <term><varname>ConditionNull=</varname></term>
 734
 735                                 <listitem><para>Before starting a unit
 736                                 verify that the specified condition is
 737                                 true. With
 738                                 <varname>ConditionPathExists=</varname>
 739                                 a file existence condition can be
 740                                 checked before a unit is started. If
 741                                 the specified absolute path name does
 742                                 not exist, startup of a unit will not
 743                                 actually happen, however the unit is
 744                                 still useful for ordering purposes in
 745                                 this case. The condition is checked at
 746                                 the time the queued start job is to be
 747                                 executed. If the absolute path name
 748                                 passed to
 749                                 <varname>ConditionPathExists=</varname>
 750                                 is prefixed with an exclamation mark
 751                                 (!), the test is negated, and the unit
 752                                 is only started if the path does not
 753                                 exist.
 754                                 <varname>ConditionPathExistsGlob=</varname>
 755                                 works in a similar way, but checks for
 756                                 the existence of at least one file or
 757                                 directory matching the specified
 758                                 globbing
 759                                 pattern. <varname>ConditionPathIsDirectory=</varname>
 760                                 is similar to
 761                                 <varname>ConditionPathExists=</varname>
 762                                 but verifies whether a certain path
 763                                 exists and is a
 764                                 directory. <varname>ConditionPathIsSymbolicLink=</varname>
 765                                 is similar to
 766                                 <varname>ConditionPathExists=</varname>
 767                                 but verifies whether a certain path
 768                                 exists and is a symbolic
 769                                 link. <varname>ConditionPathIsMountPoint=</varname>
 770                                 is similar to
 771                                 <varname>ConditionPathExists=</varname>
 772                                 but verifies whether a certain path
 773                                 exists and is a mount
 774                                 point. <varname>ConditionPathIsReadWrite=</varname>
 775                                 is similar to
 776                                 <varname>ConditionPathExists=</varname>
 777                                 but verifies whether the underlying
 778                                 file system is read and writable
 779                                 (i.e. not mounted
 780                                 read-only). <varname>ConditionFileIsExecutable=</varname>
 781                                 is similar to
 782                                 <varname>ConditionPathExists=</varname>
 783                                 but verifies whether a certain path
 784                                 exists, is a regular file and marked
 785                                 executable.
 786                                 <varname>ConditionDirectoryNotEmpty=</varname>
 787                                 is similar to
 788                                 <varname>ConditionPathExists=</varname>
 789                                 but verifies whether a certain path
 790                                 exists and is a non-empty
 791                                 directory. Similarly
 792                                 <varname>ConditionKernelCommandLine=</varname>
 793                                 may be used to check whether a
 794                                 specific kernel command line option is
 795                                 set (or if prefixed with the
 796                                 exclamation mark unset). The argument
 797                                 must either be a single word, or an
 798                                 assignment (i.e. two words, separated
 799                                 by the equality sign). In the former
 800                                 case the kernel command line is
 801                                 searched for the word appearing as is,
 802                                 or as left hand side of an
 803                                 assignment. In the latter case the
 804                                 exact assignment is looked for with
 805                                 right and left hand side
 806                                 matching. <varname>ConditionVirtualization=</varname>
 807                                 may be used to check whether the
 808                                 system is executed in a virtualized
 809                                 environment and optionally test
 810                                 whether it is a specific
 811                                 implementation. Takes either boolean
 812                                 value to check if being executed in
 813                                 any virtualized environment, or one of
 814                                 <varname>vm</varname> and
 815                                 <varname>container</varname> to test
 816                                 against a specific type of
 817                                 virtualization solution, or one of
 818                                 <varname>qemu</varname>,
 819                                 <varname>kvm</varname>,
 820                                 <varname>vmware</varname>,
 821                                 <varname>microsoft</varname>,
 822                                 <varname>oracle</varname>,
 823                                 <varname>xen</varname>,
 824                                 <varname>bochs</varname>,
 825                                 <varname>chroot</varname>,
 826                                 <varname>openvz</varname>,
 827                                 <varname>lxc</varname>,
 828                                 <varname>lxc-libvirt</varname>,
 829                                 <varname>systemd-nspawn</varname> to
 830                                 test against a specific
 831                                 implementation. If multiple
 832                                 virtualization technologies are nested
 833                                 only the innermost is considered. The
 834                                 test may be negated by prepending an
 835                                 exclamation mark.
 836                                 <varname>ConditionSecurity=</varname>
 837                                 may be used to check whether the given
 838                                 security module is enabled on the
 839                                 system.  Currently the only recognized
 840                                 value is <varname>selinux</varname>.
 841                                 The test may be negated by prepending
 842                                 an exclamation
 843                                 mark. <varname>ConditionCapability=</varname>
 844                                 may be used to check whether the given
 845                                 capability exists in the capability
 846                                 bounding set of the service manager
 847                                 (i.e. this does not check whether
 848                                 capability is actually available in
 849                                 the permitted or effective sets, see
 850                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 851                                 for details). Pass a capability name
 852                                 such as <literal>CAP_MKNOD</literal>,
 853                                 possibly prefixed with an exclamation
 854                                 mark to negate the check. Finally,
 855                                 <varname>ConditionNull=</varname> may
 856                                 be used to add a constant condition
 857                                 check value to the unit. It takes a
 858                                 boolean argument. If set to
 859                                 <varname>false</varname> the condition
 860                                 will always fail, otherwise
 861                                 succeed. If multiple conditions are
 862                                 specified the unit will be executed if
 863                                 all of them apply (i.e. a logical AND
 864                                 is applied). Condition checks can be
 865                                 prefixed with a pipe symbol (|) in
 866                                 which case a condition becomes a
 867                                 triggering condition. If at least one
 868                                 triggering condition is defined for a
 869                                 unit then the unit will be executed if
 870                                 at least one of the triggering
 871                                 conditions apply and all of the
 872                                 non-triggering conditions. If you
 873                                 prefix an argument with the pipe
 874                                 symbol and an exclamation mark the
 875                                 pipe symbol must be passed first, the
 876                                 exclamation second. Except for
 877                                 <varname>ConditionPathIsSymbolicLink=</varname>,
 878                                 all path checks follow
 879                                 symlinks.</para></listitem>
 880                         </varlistentry>
 881
 882                         <varlistentry>
 883                                 <term><varname>SourcePath=</varname></term>
 884                                 <listitem><para>A path to a
 885                                 configuration file this unit has been
 886                                 generated from. This is primarily
 887                                 useful for implementation of generator
 888                                 tools that convert configuration from
 889                                 an external configuration file format
 890                                 into native unit files. Thus
 891                                 functionality should not be used in
 892                                 normal units.</para></listitem>
 893                         </varlistentry>
 894                 </variablelist>
 895
 896                 <para>Unit file may include a [Install] section, which
 897                 carries installation information for the unit. This
 898                 section is not interpreted by
 899                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 900                 during runtime. It is used exclusively by the
 901                 <command>enable</command> and
 902                 <command>disable</command> commands of the
 903                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 904                 tool during installation of a unit:</para>
 905
 906                 <variablelist>
 907                         <varlistentry>
 908                                 <term><varname>Alias=</varname></term>
 909
 910                                 <listitem><para>Additional names this
 911                                 unit shall be installed under. The
 912                                 names listed here must have the same
 913                                 suffix (i.e. type) as the unit file
 914                                 name. This option may be specified
 915                                 more than once, in which case all
 916                                 listed names are used. At installation
 917                                 time,
 918                                 <command>systemctl enable</command>
 919                                 will create symlinks from these names
 920                                 to the unit file name.</para></listitem>
 921                         </varlistentry>
 922
 923                         <varlistentry>
 924                                 <term><varname>WantedBy=</varname></term>
 925                                 <term><varname>RequiredBy=</varname></term>
 926
 927                                 <listitem><para>Installs a symlink in
 928                                 the <filename>.wants/</filename>
 929                                 resp. <filename>.requires/</filename>
 930                                 subdirectory for a unit. This has the
 931                                 effect that when the listed unit name
 932                                 is activated the unit listing it is
 933                                 activated
 934                                 too. <command>WantedBy=foo.service</command>
 935                                 in a service
 936                                 <filename>bar.service</filename> is
 937                                 mostly equivalent to
 938                                 <command>Alias=foo.service.wants/bar.service</command>
 939                                 in the same file.</para></listitem>
 940                         </varlistentry>
 941
 942                         <varlistentry>
 943                                 <term><varname>Also=</varname></term>
 944
 945                                 <listitem><para>Additional units to
 946                                 install when this unit is
 947                                 installed. If the user requests
 948                                 installation of a unit with this
 949                                 option configured,
 950                                 <command>systemctl enable</command>
 951                                 will automatically install units
 952                                 listed in this option as
 953                                 well.</para></listitem>
 954                         </varlistentry>
 955                 </variablelist>
 956
 957         </refsect1>
 958
 959         <refsect1>
 960                 <title>See Also</title>
 961                 <para>
 962                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 963                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 964                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 965                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 966                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 967                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 968                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 969                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 970                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 971                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 972                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 973                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 974                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 975                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 976                 </para>
 977         </refsect1>
 978
 979 </refentry>