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 General Public License as published by
  12   the Free Software Foundation; either version 2 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   General Public License for more details.
  19
  20   You should have received a copy of the GNU 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 appropiate 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                     </tbody>
 262                   </tgroup>
 263                 </table>
 264
 265                 <para>If a unit file is empty (i.e. has the file size
 266                 0) or is symlinked to <filename>/dev/null</filename>
 267                 its configuration will not be loaded and it appears
 268                 with a load state of <literal>masked</literal>, and
 269                 cannot be activated. Use this as an effective way to
 270                 fully disable a unit, making it impossible to start it
 271                 even manually.</para>
 272
 273                 <para>The unit file format is covered by the
 274                 <ulink
 275                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 276                 Stability Promise</ulink>.</para>
 277         </refsect1>
 278
 279         <refsect1>
 280                 <title>Options</title>
 281
 282                 <para>Unit file may include a [Unit] section, which
 283                 carries generic information about the unit that is not
 284                 dependent on the type of unit:</para>
 285
 286                 <variablelist>
 287
 288                         <varlistentry>
 289                                 <term><varname>Description=</varname></term>
 290                                 <listitem><para>A free-form string
 291                                 describing the unit. This is intended
 292                                 for use in UIs to show descriptive
 293                                 information along with the unit
 294                                 name.</para></listitem>
 295                         </varlistentry>
 296
 297                         <varlistentry>
 298                                 <term><varname>Requires=</varname></term>
 299
 300                                 <listitem><para>Configures requirement
 301                                 dependencies on other units. If this
 302                                 unit gets activated, the units listed
 303                                 here will be activated as well. If one
 304                                 of the other units gets deactivated or
 305                                 its activation fails, this unit will
 306                                 be deactivated. This option may be
 307                                 specified more than once, in which
 308                                 case requirement dependencies for all
 309                                 listed names are created. Note that
 310                                 requirement dependencies do not
 311                                 influence the order in which services
 312                                 are started or stopped. This has to be
 313                                 configured independently with the
 314                                 <varname>After=</varname> or
 315                                 <varname>Before=</varname> options. If
 316                                 a unit
 317                                 <filename>foo.service</filename>
 318                                 requires a unit
 319                                 <filename>bar.service</filename> as
 320                                 configured with
 321                                 <varname>Requires=</varname> and no
 322                                 ordering is configured with
 323                                 <varname>After=</varname> or
 324                                 <varname>Before=</varname>, then both
 325                                 units will be started simultaneously
 326                                 and without any delay between them if
 327                                 <filename>foo.service</filename> is
 328                                 activated. Often it is a better choice
 329                                 to use <varname>Wants=</varname>
 330                                 instead of
 331                                 <varname>Requires=</varname> in order
 332                                 to achieve a system that is more
 333                                 robust when dealing with failing
 334                                 services.</para></listitem>
 335                         </varlistentry>
 336
 337                         <varlistentry>
 338                                 <term><varname>RequiresOverridable=</varname></term>
 339
 340                                 <listitem><para>Similar to
 341                                 <varname>Requires=</varname>.
 342                                 Dependencies listed in
 343                                 <varname>RequiresOverridable=</varname>
 344                                 which cannot be fulfilled or fail to
 345                                 start are ignored if the startup was
 346                                 explicitly requested by the user. If
 347                                 the start-up was pulled in indirectly
 348                                 by some dependency or automatic
 349                                 start-up of units that is not
 350                                 requested by the user this dependency
 351                                 must be fulfilled and otherwise the
 352                                 transaction fails. Hence, this option
 353                                 may be used to configure dependencies
 354                                 that are normally honored unless the
 355                                 user explicitly starts up the unit, in
 356                                 which case whether they failed or not
 357                                 is irrelevant.</para></listitem>
 358
 359                         </varlistentry>
 360                         <varlistentry>
 361                                 <term><varname>Requisite=</varname></term>
 362                                 <term><varname>RequisiteOverridable=</varname></term>
 363
 364                                 <listitem><para>Similar to
 365                                 <varname>Requires=</varname>
 366                                 resp. <varname>RequiresOverridable=</varname>. However,
 367                                 if a unit listed here is not started
 368                                 already it will not be started and the
 369                                 transaction fails
 370                                 immediately.</para></listitem>
 371                         </varlistentry>
 372
 373                         <varlistentry>
 374                                 <term><varname>Wants=</varname></term>
 375
 376                                 <listitem><para>A weaker version of
 377                                 <varname>Requires=</varname>. A unit
 378                                 listed in this option will be started
 379                                 if the configuring unit is. However,
 380                                 if the listed unit fails to start up
 381                                 or cannot be added to the transaction
 382                                 this has no impact on the validity of
 383                                 the transaction as a whole. This is
 384                                 the recommended way to hook start-up
 385                                 of one unit to the start-up of another
 386                                 unit. Note that dependencies of this
 387                                 type may also be configured outside of
 388                                 the unit configuration file by
 389                                 adding a symlink to a
 390                                 <filename>.wants/</filename> directory
 391                                 accompanying the unit file. For
 392                                 details see above.</para></listitem>
 393                         </varlistentry>
 394
 395                         <varlistentry>
 396                                 <term><varname>BindTo=</varname></term>
 397
 398                                 <listitem><para>Configures requirement
 399                                 dependencies, very similar in style to
 400                                 <varname>Requires=</varname>, however
 401                                 in addition to this behaviour it also
 402                                 declares that this unit is stopped
 403                                 when any of the units listed suddenly
 404                                 disappears. Units can suddenly,
 405                                 unexpectedly disappear if a service
 406                                 terminates on its own choice, a device
 407                                 is unplugged or a mount point
 408                                 unmounted without involvement of
 409                                 systemd.</para></listitem>
 410                         </varlistentry>
 411
 412                         <varlistentry>
 413                                 <term><varname>Conflicts=</varname></term>
 414
 415                                 <listitem><para>Configures negative
 416                                 requirement dependencies. If a unit
 417                                 has a
 418                                 <varname>Conflicts=</varname> setting
 419                                 on another unit, starting the former
 420                                 will stop the latter and vice
 421                                 versa. Note that this setting is
 422                                 independent of and orthogonal to the
 423                                 <varname>After=</varname> and
 424                                 <varname>Before=</varname> ordering
 425                                 dependencies.</para>
 426
 427                                 <para>If a unit A that conflicts with
 428                                 a unit B is scheduled to be started at
 429                                 the same time as B, the transaction
 430                                 will either fail (in case both are
 431                                 required part of the transaction) or
 432                                 be modified to be fixed (in case one
 433                                 or both jobs are not a required part
 434                                 of the transaction). In the latter
 435                                 case the job that is not the required
 436                                 will be removed, or in case both are
 437                                 not required the unit that conflicts
 438                                 will be started and the unit that is
 439                                 conflicted is
 440                                 stopped.</para></listitem>
 441                         </varlistentry>
 442
 443                         <varlistentry>
 444                                 <term><varname>Before=</varname></term>
 445                                 <term><varname>After=</varname></term>
 446
 447                                 <listitem><para>Configures ordering
 448                                 dependencies between units. If a unit
 449                                 <filename>foo.service</filename>
 450                                 contains a setting
 451                                 <option>Before=bar.service</option>
 452                                 and both units are being started,
 453                                 <filename>bar.service</filename>'s
 454                                 start-up is delayed until
 455                                 <filename>foo.service</filename> is
 456                                 started up. Note that this setting is
 457                                 independent of and orthogonal to the
 458                                 requirement dependencies as configured
 459                                 by <varname>Requires=</varname>. It is
 460                                 a common pattern to include a unit
 461                                 name in both the
 462                                 <varname>After=</varname> and
 463                                 <varname>Requires=</varname> option in
 464                                 which case the unit listed will be
 465                                 started before the unit that is
 466                                 configured with these options. This
 467                                 option may be specified more than
 468                                 once, in which case ordering
 469                                 dependencies for all listed names are
 470                                 created. <varname>After=</varname> is
 471                                 the inverse of
 472                                 <varname>Before=</varname>, i.e. while
 473                                 <varname>After=</varname> ensures that
 474                                 the configured unit is started after
 475                                 the listed unit finished starting up,
 476                                 <varname>Before=</varname> ensures the
 477                                 opposite, i.e.  that the configured
 478                                 unit is fully started up before the
 479                                 listed unit is started. Note that when
 480                                 two units with an ordering dependency
 481                                 between them are shut down, the
 482                                 inverse of the start-up order is
 483                                 applied. i.e. if a unit is configured
 484                                 with <varname>After=</varname> on
 485                                 another unit, the former is stopped
 486                                 before the latter if both are shut
 487                                 down. If one unit with an ordering
 488                                 dependency on another unit is shut
 489                                 down while the latter is started up,
 490                                 the shut down is ordered before the
 491                                 start-up regardless whether the
 492                                 ordering dependency is actually of
 493                                 type <varname>After=</varname> or
 494                                 <varname>Before=</varname>. If two
 495                                 units have no ordering dependencies
 496                                 between them they are shut down
 497                                 resp. started up simultaneously, and
 498                                 no ordering takes
 499                                 place. </para></listitem>
 500                         </varlistentry>
 501
 502                         <varlistentry>
 503                                 <term><varname>OnFailure=</varname></term>
 504
 505                                 <listitem><para>Lists one or more
 506                                 units that are activated when this
 507                                 unit enters the
 508                                 '<literal>failed</literal>'
 509                                 state.</para></listitem>
 510                         </varlistentry>
 511
 512                         <varlistentry>
 513                                 <term><varname>OnFailureIsolate=</varname></term>
 514
 515                                 <listitem><para>Takes a boolean
 516                                 argument. If <option>true</option> the
 517                                 unit listed in
 518                                 <varname>OnFailure=</varname> will be
 519                                 enqueued in isolation mode, i.e. all
 520                                 units that are not its dependency will
 521                                 be stopped. If this is set only a
 522                                 single unit may be listed in
 523                                 <varname>OnFailure=</varname>. Defaults
 524                                 to
 525                                 <option>false</option>.</para></listitem>
 526                         </varlistentry>
 527
 528                         <varlistentry>
 529                                 <term><varname>IgnoreOnIsolate=</varname></term>
 530
 531                                 <listitem><para>Takes a boolean
 532                                 argument. If <option>true</option>
 533                                 this unit will not be stopped when
 534                                 isolating another unit. Defaults to
 535                                 <option>false</option>.</para></listitem>
 536                         </varlistentry>
 537
 538                         <varlistentry>
 539                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 540
 541                                 <listitem><para>Takes a boolean
 542                                 argument. If <option>true</option>
 543                                 this unit will not be included in
 544                                 snapshots. Defaults to
 545                                 <option>true</option> for device and
 546                                 snapshot units, <option>false</option>
 547                                 for the others.</para></listitem>
 548                         </varlistentry>
 549
 550                         <varlistentry>
 551                                 <term><varname>StopWhenUnneeded=</varname></term>
 552
 553                                 <listitem><para>Takes a boolean
 554                                 argument. If <option>true</option>
 555                                 this unit will be stopped when it is
 556                                 no longer used. Note that in order to
 557                                 minimize the work to be executed,
 558                                 systemd will not stop units by default
 559                                 unless they are conflicting with other
 560                                 units, or the user explicitly
 561                                 requested their shut down. If this
 562                                 option is set, a unit will be
 563                                 automatically cleaned up if no other
 564                                 active unit requires it. Defaults to
 565                                 <option>false</option>.</para></listitem>
 566                         </varlistentry>
 567
 568                         <varlistentry>
 569                                 <term><varname>RefuseManualStart=</varname></term>
 570                                 <term><varname>RefuseManualStop=</varname></term>
 571
 572                                 <listitem><para>Takes a boolean
 573                                 argument. If <option>true</option>
 574                                 this unit can only be activated
 575                                 (resp. deactivated) indirectly. In
 576                                 this case explicit start-up
 577                                 (resp. termination) requested by the
 578                                 user is denied, however if it is
 579                                 started (resp. stopped) as a
 580                                 dependency of another unit, start-up
 581                                 (resp. termination) will succeed. This
 582                                 is mostly a safety feature to ensure
 583                                 that the user does not accidentally
 584                                 activate units that are not intended
 585                                 to be activated explicitly, and not
 586                                 accidentally deactivate units that are
 587                                 not intended to be deactivated.
 588                                 These options default to
 589                                 <option>false</option>.</para></listitem>
 590                         </varlistentry>
 591
 592                         <varlistentry>
 593                                 <term><varname>AllowIsolate=</varname></term>
 594
 595                                 <listitem><para>Takes a boolean
 596                                 argument. If <option>true</option>
 597                                 this unit may be used with the
 598                                 <command>systemctl isolate</command>
 599                                 command. Otherwise this will be
 600                                 refused. It probably is a good idea to
 601                                 leave this disabled except for target
 602                                 units that shall be used similar to
 603                                 runlevels in SysV init systems, just
 604                                 as a precaution to avoid unusable
 605                                 system states. This option defaults to
 606                                 <option>false</option>.</para></listitem>
 607                         </varlistentry>
 608
 609                         <varlistentry>
 610                                 <term><varname>DefaultDependencies=</varname></term>
 611
 612                                 <listitem><para>Takes a boolean
 613                                 argument. If <option>true</option>
 614                                 (the default), a few default
 615                                 dependencies will implicitly be
 616                                 created for the unit. The actual
 617                                 dependencies created depend on the
 618                                 unit type. For example, for service
 619                                 units, these dependencies ensure that
 620                                 the service is started only after
 621                                 basic system initialization is
 622                                 completed and is properly terminated on
 623                                 system shutdown. See the respective
 624                                 man pages for details. Generally, only
 625                                 services involved with early boot or
 626                                 late shutdown should set this option
 627                                 to <option>false</option>. It is
 628                                 highly recommended to leave this
 629                                 option enabled for the majority of
 630                                 common units. If set to
 631                                 <option>false</option> this option
 632                                 does not disable all implicit
 633                                 dependencies, just non-essential
 634                                 ones.</para></listitem>
 635                         </varlistentry>
 636
 637                         <varlistentry>
 638                                 <term><varname>JobTimeoutSec=</varname></term>
 639
 640                                 <listitem><para>When clients are
 641                                 waiting for a job of this unit to
 642                                 complete, time out after the specified
 643                                 time. If this time limit is reached
 644                                 the job will be cancelled, the unit
 645                                 however will not change state or even
 646                                 enter the '<literal>failed</literal>'
 647                                 mode. This value defaults to 0 (job
 648                                 timeouts disabled), except for device
 649                                 units. NB: this timeout is independent
 650                                 from any unit-specific timeout (for
 651                                 example, the timeout set with
 652                                 <varname>Timeout=</varname> in service
 653                                 units) as the job timeout has no
 654                                 effect on the unit itself, only on the
 655                                 job that might be pending for it. Or
 656                                 in other words: unit-specific timeouts
 657                                 are useful to abort unit state
 658                                 changes, and revert them. The job
 659                                 timeout set with this option however
 660                                 is useful to abort only the job
 661                                 waiting for the unit state to
 662                                 change.</para></listitem>
 663                         </varlistentry>
 664
 665                         <varlistentry>
 666                                 <term><varname>ConditionPathExists=</varname></term>
 667                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 668                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 669                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 670                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 671                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 672                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 673                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 674                                 <term><varname>ConditionVirtualization=</varname></term>
 675                                 <term><varname>ConditionSecurity=</varname></term>
 676                                 <term><varname>ConditionCapability=</varname></term>
 677                                 <term><varname>ConditionNull=</varname></term>
 678
 679                                 <listitem><para>Before starting a unit
 680                                 verify that the specified condition is
 681                                 true. With
 682                                 <varname>ConditionPathExists=</varname>
 683                                 a file existence condition can be
 684                                 checked before a unit is started. If
 685                                 the specified absolute path name does
 686                                 not exist, startup of a unit will not
 687                                 actually happen, however the unit is
 688                                 still useful for ordering purposes in
 689                                 this case. The condition is checked at
 690                                 the time the queued start job is to be
 691                                 executed. If the absolute path name
 692                                 passed to
 693                                 <varname>ConditionPathExists=</varname>
 694                                 is prefixed with an exclamation mark
 695                                 (!), the test is negated, and the unit
 696                                 is only started if the path does not
 697                                 exist.
 698                                 <varname>ConditionPathExistsGlob=</varname>
 699                                 works in a similar way, but checks for
 700                                 the existence of at least one file or
 701                                 directory matching the specified
 702                                 globbing
 703                                 pattern. <varname>ConditionPathIsDirectory=</varname>
 704                                 is similar to
 705                                 <varname>ConditionPathExists=</varname>
 706                                 but verifies whether a certain path
 707                                 exists and is a
 708                                 directory. <varname>ConditionPathIsSymbolicLink=</varname>
 709                                 is similar to
 710                                 <varname>ConditionPathExists=</varname>
 711                                 but verifies whether a certain path
 712                                 exists and is a symbolic
 713                                 link. <varname>ConditionPathIsMountPoint=</varname>
 714                                 is similar to
 715                                 <varname>ConditionPathExists=</varname>
 716                                 but verifies whether a certain path
 717                                 exists and is a mount
 718                                 point. <varname>ConditionFileIsExecutable=</varname>
 719                                 is similar to
 720                                 <varname>ConditionPathExists=</varname>
 721                                 but verifies whether a certain path
 722                                 exists, is a regular file and marked
 723                                 executable.
 724                                 <varname>ConditionDirectoryNotEmpty=</varname>
 725                                 is similar to
 726                                 <varname>ConditionPathExists=</varname>
 727                                 but verifies whether a certain path
 728                                 exists and is a non-empty
 729                                 directory. Similarly
 730                                 <varname>ConditionKernelCommandLine=</varname>
 731                                 may be used to check whether a
 732                                 specific kernel command line option is
 733                                 set (or if prefixed with the
 734                                 exclamation mark unset). The argument
 735                                 must either be a single word, or an
 736                                 assignment (i.e. two words, separated
 737                                 by the equality sign). In the former
 738                                 case the kernel command line is
 739                                 searched for the word appearing as is,
 740                                 or as left hand side of an
 741                                 assignment. In the latter case the
 742                                 exact assignment is looked for with
 743                                 right and left hand side
 744                                 matching. <varname>ConditionVirtualization=</varname>
 745                                 may be used to check whether the
 746                                 system is executed in a virtualized
 747                                 environment and optionally test
 748                                 whether it is a specific
 749                                 implementation. Takes either boolean
 750                                 value to check if being executed in
 751                                 any virtualized environment, or one of
 752                                 <varname>vm</varname> and
 753                                 <varname>container</varname> to test
 754                                 against a specific type of
 755                                 virtualization solution, or one of
 756                                 <varname>qemu</varname>,
 757                                 <varname>kvm</varname>,
 758                                 <varname>vmware</varname>,
 759                                 <varname>microsoft</varname>,
 760                                 <varname>oracle</varname>,
 761                                 <varname>xen</varname>,
 762                                 <varname>bochs</varname>,
 763                                 <varname>chroot</varname>,
 764                                 <varname>openvz</varname>,
 765                                 <varname>lxc</varname>,
 766                                 <varname>systemd-nspawn</varname>,
 767                                 <varname>pidns</varname> to test
 768                                 against a specific implementation. If
 769                                 multiple virtualization technologies
 770                                 are nested only the innermost is
 771                                 considered. The test may be negated by
 772                                 prepending an exclamation mark.
 773                                 <varname>ConditionSecurity=</varname>
 774                                 may be used to check whether the given
 775                                 security module is enabled on the
 776                                 system.  Currently the only recognized
 777                                 value is <varname>selinux</varname>.
 778                                 The test may be negated by prepending
 779                                 an exclamation
 780                                 mark. <varname>ConditionCapability=</varname>
 781                                 may be used to check whether the given
 782                                 capability exists in the capability
 783                                 bounding set of the service manager
 784                                 (i.e. this does not check whether
 785                                 capability is actually available in
 786                                 the permitted or effective sets, see
 787                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 788                                 for details). Pass a capability name
 789                                 such as <literal>CAP_MKNOD</literal>,
 790                                 possibly prefixed with an exclamation
 791                                 mark to negate the check. Finally,
 792                                 <varname>ConditionNull=</varname> may
 793                                 be used to add a constant condition
 794                                 check value to the unit. It takes a
 795                                 boolean argument. If set to
 796                                 <varname>false</varname> the condition
 797                                 will always fail, otherwise
 798                                 succeed. If multiple conditions are
 799                                 specified the unit will be executed if
 800                                 all of them apply (i.e. a logical AND
 801                                 is applied). Condition checks can be
 802                                 prefixed with a pipe symbol (|) in
 803                                 which case a condition becomes a
 804                                 triggering condition. If at least one
 805                                 triggering condition is defined for a
 806                                 unit then the unit will be executed if
 807                                 at least one of the triggering
 808                                 conditions apply and all of the
 809                                 non-triggering conditions. If you
 810                                 prefix an argument with the pipe
 811                                 symbol and an exclamation mark the
 812                                 pipe symbol must be passed first, the
 813                                 exclamation second. Except for
 814                                 <varname>ConditionPathIsSymbolicLink=</varname>,
 815                                 all path checks follow
 816                                 symlinks.</para></listitem>
 817                         </varlistentry>
 818
 819                         <varlistentry>
 820                                 <term><varname>Names=</varname></term>
 821
 822                                 <listitem><para>Additional names for
 823                                 this unit. The names listed here must
 824                                 have the same suffix (i.e. type) as
 825                                 the unit file name. This option may be
 826                                 specified more than once, in which
 827                                 case all listed names are used. Note
 828                                 that this option is different from the
 829                                 <varname>Alias=</varname> option from
 830                                 the [Install] section mentioned
 831                                 below. See below for details. Note
 832                                 that in almost all cases this option
 833                                 is not what you want. A symlink alias
 834                                 in the file system is generally
 835                                 preferable since it can be used as
 836                                 lookup key. If a unit with a symlinked
 837                                 alias name is not loaded and needs to
 838                                 be it is easily found via the
 839                                 symlink. However, if a unit with an
 840                                 alias name configured with this
 841                                 setting is not loaded it will not be
 842                                 discovered. This settings' only use is
 843                                 in conjunction with service
 844                                 instances.</para>
 845                                 </listitem>
 846                         </varlistentry>
 847                 </variablelist>
 848
 849                 <para>Unit file may include a [Install] section, which
 850                 carries installation information for the unit. This
 851                 section is not interpreted by
 852                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 853                 during runtime. It is used exclusively by the
 854                 <command>enable</command> and
 855                 <command>disable</command> commands of the
 856                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 857                 tool during installation of a unit:</para>
 858
 859                 <variablelist>
 860                         <varlistentry>
 861                                 <term><varname>Alias=</varname></term>
 862
 863                                 <listitem><para>Additional names this
 864                                 unit shall be installed under. The
 865                                 names listed here must have the same
 866                                 suffix (i.e. type) as the unit file
 867                                 name. This option may be specified
 868                                 more than once, in which case all
 869                                 listed names are used. At installation
 870                                 time,
 871                                 <command>systemctl enable</command>
 872                                 will create symlinks from these names
 873                                 to the unit file name. Note that this
 874                                 is different from the
 875                                 <varname>Names=</varname> option from
 876                                 the [Unit] section mentioned above:
 877                                 The names from
 878                                 <varname>Names=</varname> apply
 879                                 unconditionally if the unit is
 880                                 loaded. The names from
 881                                 <varname>Alias=</varname> apply only
 882                                 if the unit has actually been
 883                                 installed with the
 884                                 <command>systemctl enable</command>
 885                                 command.  Also, if systemd searches for a
 886                                 unit, it will discover symlinked alias
 887                                 names as configured with
 888                                 <varname>Alias=</varname>, but not
 889                                 names configured with
 890                                 <varname>Names=</varname> only. It is
 891                                 a common pattern to list a name in
 892                                 both options. In this case, a unit
 893                                 will be active under all names if
 894                                 installed, but also if not installed
 895                                 but requested explicitly under its
 896                                 main name.</para></listitem>
 897                         </varlistentry>
 898
 899                         <varlistentry>
 900                                 <term><varname>WantedBy=</varname></term>
 901
 902                                 <listitem><para>Installs a symlink in
 903                                 the <filename>.wants/</filename>
 904                                 subdirectory for a unit. This has the
 905                                 effect that when the listed unit name
 906                                 is activated the unit listing it is
 907                                 activated
 908                                 too. <command>WantedBy=foo.service</command>
 909                                 in a service
 910                                 <filename>bar.service</filename> is
 911                                 mostly equivalent to
 912                                 <command>Alias=foo.service.wants/bar.service</command>
 913                                 in the same file.</para></listitem>
 914                         </varlistentry>
 915
 916                         <varlistentry>
 917                                 <term><varname>Also=</varname></term>
 918
 919                                 <listitem><para>Additional units to
 920                                 install when this unit is
 921                                 installed. If the user requests
 922                                 installation of a unit with this
 923                                 option configured,
 924                                 <command>systemctl enable</command>
 925                                 will automatically install units
 926                                 listed in this option as
 927                                 well.</para></listitem>
 928                         </varlistentry>
 929                 </variablelist>
 930
 931         </refsect1>
 932
 933         <refsect1>
 934                 <title>See Also</title>
 935                 <para>
 936                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 937                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 938                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 939                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 940                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 941                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 942                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 943                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 944                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 945                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 946                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 947                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 948                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 949                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 950                 </para>
 951         </refsect1>
 952
 953 </refentry>