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                 read as if its contents were listed in place of the
 125                 <option>.include</option> directive.</para>
 126
 127                 <para>Along with a unit file
 128                 <filename>foo.service</filename> a directory
 129                 <filename>foo.service.wants/</filename> may exist. All
 130                 units symlinked from such a directory are implicitly
 131                 added as dependencies of type
 132                 <varname>Wanted=</varname> to the unit. This is useful
 133                 to hook units into the start-up of other units,
 134                 without having to modify their unit configuration
 135                 files. For details about the semantics of
 136                 <varname>Wanted=</varname> see below. The preferred
 137                 way to create symlinks in the
 138                 <filename>.wants/</filename> directory of a service is
 139                 with the <command>enable</command> command of the
 140                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 141                 tool which reads information from the [Install]
 142                 section of unit files. (See below.) A similar
 143                 functionality exists for <varname>Requires=</varname>
 144                 type dependencies as well, the directory suffix is
 145                 <filename>.requires/</filename> in this case.</para>
 146
 147                 <para>Note that while systemd offers a flexible
 148                 dependency system between units it is recommended to
 149                 use this functionality only sparsely and instead rely
 150                 on techniques such as bus-based or socket-based
 151                 activation which makes dependencies implicit, which
 152                 both results in a simpler and more flexible
 153                 system.</para>
 154
 155                 <para>Some unit names reflect paths existing in the
 156                 file system name space. Example: a device unit
 157                 <filename>dev-sda.device</filename> refers to a device
 158                 with the device node <filename>/dev/sda</filename> in
 159                 the file system namespace. If this applies a special
 160                 way to escape the path name is used, so that the
 161                 result is usable as part of a file name. Basically,
 162                 given a path, "/" is replaced by "-", and all
 163                 unprintable characters and the "-" are replaced by
 164                 C-style "\x20" escapes. The root directory "/" is
 165                 encoded as single dash, while otherwise the initial
 166                 and ending "/" is removed from all paths during
 167                 transformation. This escaping is reversible.</para>
 168
 169                 <para>Optionally, units may be instantiated from a
 170                 template file at runtime. This allows creation of
 171                 multiple units from a single configuration file. If
 172                 systemd looks for a unit configuration file it will
 173                 first search for the literal unit name in the
 174                 filesystem. If that yields no success and the unit
 175                 name contains an @ character, systemd will look for a
 176                 unit template that shares the same name but with the
 177                 instance string (i.e. the part between the @ character
 178                 and the suffix) removed. Example: if a service
 179                 <filename>getty@tty3.service</filename> is requested
 180                 and no file by that name is found, systemd will look
 181                 for <filename>getty@.service</filename> and
 182                 instantiate a service from that configuration file if
 183                 it is found.</para>
 184
 185                 <para>To refer to the instance string from
 186                 within the configuration file you may use the special
 187                 <literal>%i</literal> specifier in many of the
 188                 configuration options. Other specifiers exist, the
 189                 full list is:</para>
 190
 191                 <table>
 192                   <title>Specifiers available in unit files</title>
 193                   <tgroup cols='3' align='left' colsep='1' rowsep='1'>
 194                     <colspec colname="spec" />
 195                     <colspec colname="mean" />
 196                     <colspec colname="detail" />
 197                     <thead>
 198                       <row>
 199                         <entry>Specifier</entry>
 200                         <entry>Meaning</entry>
 201                         <entry>Details</entry>
 202                       </row>
 203                     </thead>
 204                     <tbody>
 205                       <row>
 206                         <entry><literal>%n</literal></entry>
 207                         <entry>Full unit name</entry>
 208                         <entry></entry>
 209                       </row>
 210                       <row>
 211                         <entry><literal>%N</literal></entry>
 212                         <entry>Unescaped full unit name</entry>
 213                         <entry></entry>
 214                       </row>
 215                       <row>
 216                         <entry><literal>%p</literal></entry>
 217                         <entry>Prefix name</entry>
 218                         <entry>This refers to the string before the @, i.e. "getty" in the example above, where "tty3" is the instance name.</entry>
 219                       </row>
 220                       <row>
 221                         <entry><literal>%P</literal></entry>
 222                         <entry>Unescaped prefix name</entry>
 223                         <entry></entry>
 224                       </row>
 225                       <row>
 226                         <entry><literal>%i</literal></entry>
 227                         <entry>Instance name</entry>
 228                         <entry>This is the string between the @ character and the suffix.</entry>
 229                       </row>
 230                       <row>
 231                         <entry><literal>%I</literal></entry>
 232                         <entry>Unescaped instance name</entry>
 233                         <entry></entry>
 234                       </row>
 235                       <row>
 236                         <entry><literal>%f</literal></entry>
 237                         <entry>Unescaped file name</entry>
 238                         <entry>This is either the unescaped instance name (if set) with / prepended (if necessary), or the prefix name similarly prepended with /.</entry>
 239                       </row>
 240                       <row>
 241                         <entry><literal>%c</literal></entry>
 242                         <entry>Control group path of the unit</entry>
 243                         <entry></entry>
 244                       </row>
 245                       <row>
 246                         <entry><literal>%r</literal></entry>
 247                         <entry>Root control group path of systemd</entry>
 248                         <entry></entry>
 249                       </row>
 250                       <row>
 251                         <entry><literal>%R</literal></entry>
 252                         <entry>Parent directory of the root control group path of systemd</entry>
 253                         <entry></entry>
 254                       </row>
 255                       <row>
 256                         <entry><literal>%t</literal></entry>
 257                         <entry>Runtime socket dir</entry>
 258                         <entry>This is either /run (for the system manager) or $XDG_RUNTIME_DIR (for user managers).</entry>
 259                       </row>
 260                     </tbody>
 261                   </tgroup>
 262                 </table>
 263
 264                 <para>If a unit file is empty (i.e. has the file size
 265                 0) or is symlinked to <filename>/dev/null</filename>
 266                 its configuration will not be loaded and it appears
 267                 with a load state of <literal>masked</literal>, and
 268                 cannot be activated. Use this as an effective way to
 269                 fully disable a unit, making it impossible to start it
 270                 even manually.</para>
 271
 272                 <para>The unit file format is covered by the
 273                 <ulink
 274                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 275                 Stability Promise</ulink>.</para>
 276         </refsect1>
 277
 278         <refsect1>
 279                 <title>Options</title>
 280
 281                 <para>Unit file may include a [Unit] section, which
 282                 carries generic information about the unit that is not
 283                 dependent on the type of unit:</para>
 284
 285                 <variablelist>
 286
 287                         <varlistentry>
 288                                 <term><varname>Description=</varname></term>
 289                                 <listitem><para>A free-form string
 290                                 describing the unit. This is intended
 291                                 for use in UIs to show descriptive
 292                                 information along with the unit
 293                                 name.</para></listitem>
 294                         </varlistentry>
 295
 296                         <varlistentry>
 297                                 <term><varname>Requires=</varname></term>
 298
 299                                 <listitem><para>Configures requirement
 300                                 dependencies on other units. If this
 301                                 unit gets activated, the units listed
 302                                 here will be activated as well. If one
 303                                 of the other units gets deactivated or
 304                                 its activation fails, this unit will
 305                                 be deactivated. This option may be
 306                                 specified more than once, in which
 307                                 case requirement dependencies for all
 308                                 listed names are created. Note that
 309                                 requirement dependencies do not
 310                                 influence the order in which services
 311                                 are started or stopped. This has to be
 312                                 configured independently with the
 313                                 <varname>After=</varname> or
 314                                 <varname>Before=</varname> options. If
 315                                 a unit
 316                                 <filename>foo.service</filename>
 317                                 requires a unit
 318                                 <filename>bar.service</filename> as
 319                                 configured with
 320                                 <varname>Requires=</varname> and no
 321                                 ordering is configured with
 322                                 <varname>After=</varname> or
 323                                 <varname>Before=</varname>, then both
 324                                 units will be started simultaneously
 325                                 and without any delay between them if
 326                                 <filename>foo.service</filename> is
 327                                 activated. Often it is a better choice
 328                                 to use <varname>Wants=</varname>
 329                                 instead of
 330                                 <varname>Requires=</varname> in order
 331                                 to achieve a system that is more
 332                                 robust when dealing with failing
 333                                 services.</para></listitem>
 334                         </varlistentry>
 335
 336                         <varlistentry>
 337                                 <term><varname>RequiresOverridable=</varname></term>
 338
 339                                 <listitem><para>Similar to
 340                                 <varname>Requires=</varname>.
 341                                 Dependencies listed in
 342                                 <varname>RequiresOverridable=</varname>
 343                                 which cannot be fulfilled or fail to
 344                                 start are ignored if the startup was
 345                                 explicitly requested by the user. If
 346                                 the start-up was pulled in indirectly
 347                                 by some dependency or automatic
 348                                 start-up of units that is not
 349                                 requested by the user this dependency
 350                                 must be fulfilled and otherwise the
 351                                 transaction fails. Hence, this option
 352                                 may be used to configure dependencies
 353                                 that are normally honored unless the
 354                                 user explicitly starts up the unit, in
 355                                 which case whether they failed or not
 356                                 is irrelevant.</para></listitem>
 357
 358                         </varlistentry>
 359                         <varlistentry>
 360                                 <term><varname>Requisite=</varname></term>
 361                                 <term><varname>RequisiteOverridable=</varname></term>
 362
 363                                 <listitem><para>Similar to
 364                                 <varname>Requires=</varname>
 365                                 resp. <varname>RequiresOverridable=</varname>. However,
 366                                 if a unit listed here is not started
 367                                 already it will not be started and the
 368                                 transaction fails
 369                                 immediately.</para></listitem>
 370                         </varlistentry>
 371
 372                         <varlistentry>
 373                                 <term><varname>Wants=</varname></term>
 374
 375                                 <listitem><para>A weaker version of
 376                                 <varname>Requires=</varname>. A unit
 377                                 listed in this option will be started
 378                                 if the configuring unit is. However,
 379                                 if the listed unit fails to start up
 380                                 or cannot be added to the transaction
 381                                 this has no impact on the validity of
 382                                 the transaction as a whole. This is
 383                                 the recommended way to hook start-up
 384                                 of one unit to the start-up of another
 385                                 unit. Note that dependencies of this
 386                                 type may also be configured outside of
 387                                 the unit configuration file by
 388                                 adding a symlink to a
 389                                 <filename>.wants/</filename> directory
 390                                 accompanying the unit file. For
 391                                 details see above.</para></listitem>
 392                         </varlistentry>
 393
 394                         <varlistentry>
 395                                 <term><varname>BindTo=</varname></term>
 396
 397                                 <listitem><para>Configures requirement
 398                                 dependencies, very similar in style to
 399                                 <varname>Requires=</varname>, however
 400                                 in addition to this behaviour it also
 401                                 declares that this unit is stopped
 402                                 when any of the units listed suddenly
 403                                 disappears. Units can suddenly,
 404                                 unexpectedly disappear if a service
 405                                 terminates on its own choice, a device
 406                                 is unplugged or a mount point
 407                                 unmounted without involvement of
 408                                 systemd.</para></listitem>
 409                         </varlistentry>
 410
 411                         <varlistentry>
 412                                 <term><varname>Conflicts=</varname></term>
 413
 414                                 <listitem><para>Configures negative
 415                                 requirement dependencies. If a unit
 416                                 has a
 417                                 <varname>Conflicts=</varname> setting
 418                                 on another unit, starting the former
 419                                 will stop the latter and vice
 420                                 versa. Note that this setting is
 421                                 independent of and orthogonal to the
 422                                 <varname>After=</varname> and
 423                                 <varname>Before=</varname> ordering
 424                                 dependencies.</para>
 425
 426                                 <para>If a unit A that conflicts with
 427                                 a unit B is scheduled to be started at
 428                                 the same time as B, the transaction
 429                                 will either fail (in case both are
 430                                 required part of the transaction) or
 431                                 be modified to be fixed (in case one
 432                                 or both jobs are not a required part
 433                                 of the transaction). In the latter
 434                                 case the job that is not the required
 435                                 will be removed, or in case both are
 436                                 not required the unit that conflicts
 437                                 will be started and the unit that is
 438                                 conflicted is
 439                                 stopped.</para></listitem>
 440                         </varlistentry>
 441
 442                         <varlistentry>
 443                                 <term><varname>Before=</varname></term>
 444                                 <term><varname>After=</varname></term>
 445
 446                                 <listitem><para>Configures ordering
 447                                 dependencies between units. If a unit
 448                                 <filename>foo.service</filename>
 449                                 contains a setting
 450                                 <option>Before=bar.service</option>
 451                                 and both units are being started,
 452                                 <filename>bar.service</filename>'s
 453                                 start-up is delayed until
 454                                 <filename>foo.service</filename> is
 455                                 started up. Note that this setting is
 456                                 independent of and orthogonal to the
 457                                 requirement dependencies as configured
 458                                 by <varname>Requires=</varname>. It is
 459                                 a common pattern to include a unit
 460                                 name in both the
 461                                 <varname>After=</varname> and
 462                                 <varname>Requires=</varname> option in
 463                                 which case the unit listed will be
 464                                 started before the unit that is
 465                                 configured with these options. This
 466                                 option may be specified more than
 467                                 once, in which case ordering
 468                                 dependencies for all listed names are
 469                                 created. <varname>After=</varname> is
 470                                 the inverse of
 471                                 <varname>Before=</varname>, i.e. while
 472                                 <varname>After=</varname> ensures that
 473                                 the configured unit is started after
 474                                 the listed unit finished starting up,
 475                                 <varname>Before=</varname> ensures the
 476                                 opposite, i.e.  that the configured
 477                                 unit is fully started up before the
 478                                 listed unit is started. Note that when
 479                                 two units with an ordering dependency
 480                                 between them are shut down, the
 481                                 inverse of the start-up order is
 482                                 applied. i.e. if a unit is configured
 483                                 with <varname>After=</varname> on
 484                                 another unit, the former is stopped
 485                                 before the latter if both are shut
 486                                 down. If one unit with an ordering
 487                                 dependency on another unit is shut
 488                                 down while the latter is started up,
 489                                 the shut down is ordered before the
 490                                 start-up regardless whether the
 491                                 ordering dependency is actually of
 492                                 type <varname>After=</varname> or
 493                                 <varname>Before=</varname>. If two
 494                                 units have no ordering dependencies
 495                                 between them they are shut down
 496                                 resp. started up simultaneously, and
 497                                 no ordering takes
 498                                 place. </para></listitem>
 499                         </varlistentry>
 500
 501                         <varlistentry>
 502                                 <term><varname>OnFailure=</varname></term>
 503
 504                                 <listitem><para>Lists one or more
 505                                 units that are activated when this
 506                                 unit enters the
 507                                 '<literal>failed</literal>'
 508                                 state.</para></listitem>
 509                         </varlistentry>
 510
 511                         <varlistentry>
 512                                 <term><varname>OnFailureIsolate=</varname></term>
 513
 514                                 <listitem><para>Takes a boolean
 515                                 argument. If <option>true</option> the
 516                                 unit listed in
 517                                 <varname>OnFailure=</varname> will be
 518                                 enqueued in isolation mode, i.e. all
 519                                 units that are not its dependency will
 520                                 be stopped. If this is set only a
 521                                 single unit may be listed in
 522                                 <varname>OnFailure=</varname>. Defaults
 523                                 to
 524                                 <option>false</option>.</para></listitem>
 525                         </varlistentry>
 526
 527                         <varlistentry>
 528                                 <term><varname>IgnoreOnIsolate=</varname></term>
 529
 530                                 <listitem><para>Takes a boolean
 531                                 argument. If <option>true</option>
 532                                 this unit will not be stopped when
 533                                 isolating another unit. Defaults to
 534                                 <option>false</option>.</para></listitem>
 535                         </varlistentry>
 536
 537                         <varlistentry>
 538                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 539
 540                                 <listitem><para>Takes a boolean
 541                                 argument. If <option>true</option>
 542                                 this unit will not be included in
 543                                 snapshots. Defaults to
 544                                 <option>true</option> for device and
 545                                 snapshot units, <option>false</option>
 546                                 for the others.</para></listitem>
 547                         </varlistentry>
 548
 549                         <varlistentry>
 550                                 <term><varname>StopWhenUnneeded=</varname></term>
 551
 552                                 <listitem><para>Takes a boolean
 553                                 argument. If <option>true</option>
 554                                 this unit will be stopped when it is
 555                                 no longer used. Note that in order to
 556                                 minimize the work to be executed,
 557                                 systemd will not stop units by default
 558                                 unless they are conflicting with other
 559                                 units, or the user explicitly
 560                                 requested their shut down. If this
 561                                 option is set, a unit will be
 562                                 automatically cleaned up if no other
 563                                 active unit requires it. Defaults to
 564                                 <option>false</option>.</para></listitem>
 565                         </varlistentry>
 566
 567                         <varlistentry>
 568                                 <term><varname>RefuseManualStart=</varname></term>
 569                                 <term><varname>RefuseManualStop=</varname></term>
 570
 571                                 <listitem><para>Takes a boolean
 572                                 argument. If <option>true</option>
 573                                 this unit can only be activated
 574                                 (resp. deactivated) indirectly. In
 575                                 this case explicit start-up
 576                                 (resp. termination) requested by the
 577                                 user is denied, however if it is
 578                                 started (resp. stopped) as a
 579                                 dependency of another unit, start-up
 580                                 (resp. termination) will succeed. This
 581                                 is mostly a safety feature to ensure
 582                                 that the user does not accidentally
 583                                 activate units that are not intended
 584                                 to be activated explicitly, and not
 585                                 accidentally deactivate units that are
 586                                 not intended to be deactivated.
 587                                 These options default to
 588                                 <option>false</option>.</para></listitem>
 589                         </varlistentry>
 590
 591                         <varlistentry>
 592                                 <term><varname>AllowIsolate=</varname></term>
 593
 594                                 <listitem><para>Takes a boolean
 595                                 argument. If <option>true</option>
 596                                 this unit may be used with the
 597                                 <command>systemctl isolate</command>
 598                                 command. Otherwise this will be
 599                                 refused. It probably is a good idea to
 600                                 leave this disabled except for target
 601                                 units that shall be used similar to
 602                                 runlevels in SysV init systems, just
 603                                 as a precaution to avoid unusable
 604                                 system states. This option defaults to
 605                                 <option>false</option>.</para></listitem>
 606                         </varlistentry>
 607
 608                         <varlistentry>
 609                                 <term><varname>DefaultDependencies=</varname></term>
 610
 611                                 <listitem><para>Takes a boolean
 612                                 argument. If <option>true</option>
 613                                 (the default), a few default
 614                                 dependencies will implicitly be
 615                                 created for the unit. The actual
 616                                 dependencies created depend on the
 617                                 unit type. For example, for service
 618                                 units, these dependencies ensure that
 619                                 the service is started only after
 620                                 basic system initialization is
 621                                 completed and is properly terminated on
 622                                 system shutdown. See the respective
 623                                 man pages for details. Generally, only
 624                                 services involved with early boot or
 625                                 late shutdown should set this option
 626                                 to <option>false</option>. It is
 627                                 highly recommended to leave this
 628                                 option enabled for the majority of
 629                                 common units. If set to
 630                                 <option>false</option> this option
 631                                 does not disable all implicit
 632                                 dependencies, just non-essential
 633                                 ones.</para></listitem>
 634                         </varlistentry>
 635
 636                         <varlistentry>
 637                                 <term><varname>JobTimeoutSec=</varname></term>
 638
 639                                 <listitem><para>When clients are
 640                                 waiting for a job of this unit to
 641                                 complete, time out after the specified
 642                                 time. If this time limit is reached
 643                                 the job will be cancelled, the unit
 644                                 however will not change state or even
 645                                 enter the '<literal>failed</literal>'
 646                                 mode. This value defaults to 0 (job
 647                                 timeouts disabled), except for device
 648                                 units. NB: this timeout is independent
 649                                 from any unit-specific timeout (for
 650                                 example, the timeout set with
 651                                 <varname>Timeout=</varname> in service
 652                                 units) as the job timeout has no
 653                                 effect on the unit itself, only on the
 654                                 job that might be pending for it. Or
 655                                 in other words: unit-specific timeouts
 656                                 are useful to abort unit state
 657                                 changes, and revert them. The job
 658                                 timeout set with this option however
 659                                 is useful to abort only the job
 660                                 waiting for the unit state to
 661                                 change.</para></listitem>
 662                         </varlistentry>
 663
 664                         <varlistentry>
 665                                 <term><varname>ConditionPathExists=</varname></term>
 666                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 667                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 668                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 669                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 670                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 671                                 <term><varname>ConditionVirtualization=</varname></term>
 672                                 <term><varname>ConditionSecurity=</varname></term>
 673                                 <term><varname>ConditionNull=</varname></term>
 674
 675                                 <listitem><para>Before starting a unit
 676                                 verify that the specified condition is
 677                                 true. With
 678                                 <varname>ConditionPathExists=</varname>
 679                                 a file existence condition can be
 680                                 checked before a unit is started. If
 681                                 the specified absolute path name does
 682                                 not exist startup of a unit will not
 683                                 actually happen, however the unit is
 684                                 still useful for ordering purposes in
 685                                 this case. The condition is checked at
 686                                 the time the queued start job is to be
 687                                 executed. If the absolute path name
 688                                 passed to
 689                                 <varname>ConditionPathExists=</varname>
 690                                 is prefixed with an exclamation mark
 691                                 (!), the test is negated, and the unit
 692                                 only started if the path does not
 693                                 exist. <varname>ConditionPathExistsGlob=</varname>
 694                                 work in a similar way, but checks for
 695                                 the existance of at least one file or
 696                                 directory matching the specified
 697                                 globbing
 698                                 pattern. <varname>ConditionPathIsDirectory=</varname>
 699                                 is similar to
 700                                 <varname>ConditionPathExists=</varname>
 701                                 but verifies whether a certain path
 702                                 exists and is a
 703                                 directory. <varname>ConditionFileIsExecutable=</varname>
 704                                 is similar to
 705                                 <varname>ConditionPathExists=</varname>
 706                                 but verifies whether a certain path
 707                                 exists, is a regular file and marked
 708                                 executable.
 709                                 <varname>ConditionDirectoryNotEmpty=</varname>
 710                                 is similar to
 711                                 <varname>ConditionPathExists=</varname>
 712                                 but verifies whether a certain path
 713                                 exists and is a non-empty
 714                                 directory. Similarly
 715                                 <varname>ConditionKernelCommandLine=</varname>
 716                                 may be used to check whether a
 717                                 specific kernel command line option is
 718                                 set (or if prefixed with the
 719                                 exclamation mark unset). The argument
 720                                 must either be a single word, or an
 721                                 assignment (i.e. two words, separated
 722                                 by the equality sign). In the former
 723                                 case the kernel command line is
 724                                 searched for the word appearing as is,
 725                                 or as left hand side of an
 726                                 assignment. In the latter case the
 727                                 exact assignment is looked for with
 728                                 right and left hand side
 729                                 matching. <varname>ConditionVirtualization=</varname>
 730                                 may be used to check whether the
 731                                 system is executed in a virtualized
 732                                 environment and optionally test
 733                                 whether it is a specific
 734                                 implementation. Takes either boolean
 735                                 value to check if being executed in
 736                                 any virtual environment or one of the
 737                                 <varname>qemu</varname>,
 738                                 <varname>kvm</varname>,
 739                                 <varname>vmware</varname>,
 740                                 <varname>microsoft</varname>,
 741                                 <varname>oracle</varname>,
 742                                 <varname>xen</varname>,
 743                                 <varname>pidns</varname>,
 744                                 <varname>openvz</varname> to test
 745                                 against a specific implementation. The
 746                                 test may be negated by prepending an
 747                                 exclamation mark.
 748                                 <varname>ConditionSecurity=</varname>
 749                                 may be used to check whether the given
 750                                 security module is enabled on the
 751                                 system.  Currently the only recognized
 752                                 value is <varname>selinux</varname>.
 753                                 The test may be negated by prepending
 754                                 an exclamation mark. Finally,
 755                                 <varname>ConditionNull=</varname> may
 756                                 be used to add a constant condition
 757                                 check value to the unit. It takes a
 758                                 boolean argument. If set to
 759                                 <varname>false</varname> the condition
 760                                 will always fail, otherwise
 761                                 succeed. If multiple conditions are
 762                                 specified the unit will be executed if
 763                                 all of them apply (i.e. a logical AND
 764                                 is applied). Condition checks can be
 765                                 prefixed with a pipe symbol (|) in
 766                                 which case a condition becomes a
 767                                 triggering condition. If at least one
 768                                 triggering condition is defined for a
 769                                 unit then the unit will be executed if
 770                                 at least one of the triggering
 771                                 conditions apply and all of the
 772                                 non-triggering conditions. If you
 773                                 prefix an argument with the pipe
 774                                 symbol and an exclamation mark the
 775                                 pipe symbol must be passed first, the
 776                                 exclamation second.</para></listitem>
 777                         </varlistentry>
 778
 779                         <varlistentry>
 780                                 <term><varname>Names=</varname></term>
 781
 782                                 <listitem><para>Additional names for
 783                                 this unit. The names listed here must
 784                                 have the same suffix (i.e. type) as
 785                                 the unit file name. This option may be
 786                                 specified more than once, in which
 787                                 case all listed names are used. Note
 788                                 that this option is different from the
 789                                 <varname>Alias=</varname> option from
 790                                 the [Install] section mentioned
 791                                 below. See below for details. Note
 792                                 that in almost all cases this option
 793                                 is not what you want. A symlink alias
 794                                 in the file system is generally
 795                                 preferable since it can be used as
 796                                 lookup key. If a unit with a symlinked
 797                                 alias name is not loaded and needs to
 798                                 be it is easily found via the
 799                                 symlink. However, if a unit with an
 800                                 alias name configured with this
 801                                 setting is not loaded it will not be
 802                                 discovered. This settings' only use is
 803                                 in conjunction with service
 804                                 instances.</para>
 805                                 </listitem>
 806                         </varlistentry>
 807                 </variablelist>
 808
 809                 <para>Unit file may include a [Install] section, which
 810                 carries installation information for the unit. This
 811                 section is not interpreted by
 812                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 813                 during runtime. It is used exclusively by the
 814                 <command>enable</command> and
 815                 <command>disable</command> commands of the
 816                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 817                 tool during installation of a unit:</para>
 818
 819                 <variablelist>
 820                         <varlistentry>
 821                                 <term><varname>Alias=</varname></term>
 822
 823                                 <listitem><para>Additional names this
 824                                 unit shall be installed under. The
 825                                 names listed here must have the same
 826                                 suffix (i.e. type) as the unit file
 827                                 name. This option may be specified
 828                                 more than once, in which case all
 829                                 listed names are used. At installation
 830                                 time,
 831                                 <command>systemctl enable</command>
 832                                 will create symlinks from these names
 833                                 to the unit file name. Note that this
 834                                 is different from the
 835                                 <varname>Names=</varname> option from
 836                                 the [Unit] section mentioned above:
 837                                 The names from
 838                                 <varname>Names=</varname> apply
 839                                 unconditionally if the unit is
 840                                 loaded. The names from
 841                                 <varname>Alias=</varname> apply only
 842                                 if the unit has actually been
 843                                 installed with the
 844                                 <command>systemctl enable</command>
 845                                 command.  Also, if systemd searches for a
 846                                 unit, it will discover symlinked alias
 847                                 names as configured with
 848                                 <varname>Alias=</varname>, but not
 849                                 names configured with
 850                                 <varname>Names=</varname> only. It is
 851                                 a common pattern to list a name in
 852                                 both options. In this case, a unit
 853                                 will be active under all names if
 854                                 installed, but also if not installed
 855                                 but requested explicitly under its
 856                                 main name.</para></listitem>
 857                         </varlistentry>
 858
 859                         <varlistentry>
 860                                 <term><varname>WantedBy=</varname></term>
 861
 862                                 <listitem><para>Installs a symlink in
 863                                 the <filename>.wants/</filename>
 864                                 subdirectory for a unit. This has the
 865                                 effect that when the listed unit name
 866                                 is activated the unit listing it is
 867                                 activated
 868                                 too. <command>WantedBy=foo.service</command>
 869                                 in a service
 870                                 <filename>bar.service</filename> is
 871                                 mostly equivalent to
 872                                 <command>Alias=foo.service.wants/bar.service</command>
 873                                 in the same file.</para></listitem>
 874                         </varlistentry>
 875
 876                         <varlistentry>
 877                                 <term><varname>Also=</varname></term>
 878
 879                                 <listitem><para>Additional units to
 880                                 install when this unit is
 881                                 installed. If the user requests
 882                                 installation of a unit with this
 883                                 option configured,
 884                                 <command>systemctl enable</command>
 885                                 will automatically install units
 886                                 listed in this option as
 887                                 well.</para></listitem>
 888                         </varlistentry>
 889                 </variablelist>
 890
 891         </refsect1>
 892
 893         <refsect1>
 894                 <title>See Also</title>
 895                 <para>
 896                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 897                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 898                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 899                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 900                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 901                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 902                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 903                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 904                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 905                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 906                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 907                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 908                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 909                 </para>
 910         </refsect1>
 911
 912 </refentry>