man/systemd.unit.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="systemd.unit">
  25
  26         <refentryinfo>
  27                 <title>systemd.unit</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.unit</refentrytitle>
  42                 <manvolnum>5</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.unit</refname>
  47                 <refpurpose>Unit configuration</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename>systemd.service</filename>,
  52                 <filename>systemd.socket</filename>,
  53                 <filename>systemd.device</filename>,
  54                 <filename>systemd.mount</filename>,
  55                 <filename>systemd.automount</filename>,
  56                 <filename>systemd.swap</filename>,
  57                 <filename>systemd.target</filename>,
  58                 <filename>systemd.path</filename>,
  59                 <filename>systemd.timer</filename>,
  60                 <filename>systemd.snapshot</filename></para>
  61         </refsynopsisdiv>
  62
  63         <refsect1>
  64                 <title>Description</title>
  65
  66                 <para>A unit configuration file encodes information
  67                 about a service, a socket, a device, a mount point, an
  68                 automount point, a swap file or partition, a start-up
  69                 target, a file system path or a timer controlled and
  70                 supervised by
  71                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>. The
  72                 syntax is inspired by <ulink
  73                 url="http://standards.freedesktop.org/desktop-entry-spec/latest/">XDG
  74                 Desktop Entry Specification</ulink> <filename>.desktop</filename> files, which are in turn
  75                 inspired by Microsoft Windows
  76                 <filename>.ini</filename> files.</para>
  77
  78                 <para>This man pages lists the common configuration
  79                 options of all the unit types. These options need to
  80                 be configured in the [Unit] resp. [Install]
  81                 section of the unit files.</para>
  82
  83                 <para>In addition to the generic [Unit] and [Install]
  84                 sections described here, each unit should have a
  85                 type-specific section, e.g. [Service] for a service
  86                 unit. See the respective man pages for more
  87                 information.</para>
  88
  89                 <para>Unit files may contain additional options on top
  90                 of those listed here. If systemd encounters an unknown
  91                 option it will write a warning log message but
  92                 continue loading the unit. If an option is prefixed
  93                 with <option>X-</option> it is ignored completely by
  94                 systemd. Applications may use this to include
  95                 additional information in the unit files.</para>
  96
  97                 <para>Boolean arguments used in unit files can be
  98                 written in various formats. For positive settings the
  99                 strings <option>1</option>, <option>yes</option>,
 100                 <option>true</option> and <option>on</option> are
 101                 equivalent. For negative settings the strings
 102                 <option>0</option>, <option>no</option>,
 103                 <option>false</option> and <option>off</option> are
 104                 equivalent.</para>
 105
 106                 <para>Time span values encoded in unit files can be
 107                 written in various formats. A stand-alone number
 108                 specifies a time in seconds. If suffixed with a time
 109                 unit, the unit is honored. A concatenation of
 110                 multiple values with units is supported, in which case
 111                 the values are added up. Example: "50" refers to 50
 112                 seconds; "2min 200ms" refers to 2 minutes plus 200
 113                 milliseconds, i.e. 120200ms. The following time units
 114                 are understood: s, min, h, d, w, ms, us.</para>
 115
 116                 <para>Empty lines and lines starting with # or ; are
 117                 ignored. This may be used for commenting. Lines ending
 118                 in a backslash are concatenated with the following
 119                 line while reading and the backslash is replaced by a
 120                 space character. This may be used to wrap long lines.</para>
 121
 122                 <para>If a line starts with <option>.include</option>
 123                 followed by a file name, the specified file will be
 124                 parsed at this point. Make sure that the file that is
 125                 included has the appropriate section headers before
 126                 any directives.</para>
 127
 128                 <para>Along with a unit file
 129                 <filename>foo.service</filename> a directory
 130                 <filename>foo.service.wants/</filename> may exist. All
 131                 units symlinked from such a directory are implicitly
 132                 added as dependencies of type
 133                 <varname>Wanted=</varname> to the unit. This is useful
 134                 to hook units into the start-up of other units,
 135                 without having to modify their unit configuration
 136                 files. For details about the semantics of
 137                 <varname>Wanted=</varname> see below. The preferred
 138                 way to create symlinks in the
 139                 <filename>.wants/</filename> directory of a service is
 140                 with the <command>enable</command> command of the
 141                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 142                 tool which reads information from the [Install]
 143                 section of unit files. (See below.) A similar
 144                 functionality exists for <varname>Requires=</varname>
 145                 type dependencies as well, the directory suffix is
 146                 <filename>.requires/</filename> in this case.</para>
 147
 148                 <para>Note that while systemd offers a flexible
 149                 dependency system between units it is recommended to
 150                 use this functionality only sparsely and instead rely
 151                 on techniques such as bus-based or socket-based
 152                 activation which makes dependencies implicit, which
 153                 both results in a simpler and more flexible
 154                 system.</para>
 155
 156                 <para>Some unit names reflect paths existing in the
 157                 file system name space. Example: a device unit
 158                 <filename>dev-sda.device</filename> refers to a device
 159                 with the device node <filename>/dev/sda</filename> in
 160                 the file system namespace. If this applies a special
 161                 way to escape the path name is used, so that the
 162                 result is usable as part of a file name. Basically,
 163                 given a path, "/" is replaced by "-", and all
 164                 unprintable characters and the "-" are replaced by
 165                 C-style "\x20" escapes. The root directory "/" is
 166                 encoded as single dash, while otherwise the initial
 167                 and ending "/" is removed from all paths during
 168                 transformation. This escaping is reversible.</para>
 169
 170                 <para>Optionally, units may be instantiated from a
 171                 template file at runtime. This allows creation of
 172                 multiple units from a single configuration file. If
 173                 systemd looks for a unit configuration file it will
 174                 first search for the literal unit name in the
 175                 filesystem. If that yields no success and the unit
 176                 name contains an @ character, systemd will look for a
 177                 unit template that shares the same name but with the
 178                 instance string (i.e. the part between the @ character
 179                 and the suffix) removed. Example: if a service
 180                 <filename>getty@tty3.service</filename> is requested
 181                 and no file by that name is found, systemd will look
 182                 for <filename>getty@.service</filename> and
 183                 instantiate a service from that configuration file if
 184                 it is found.</para>
 185
 186                 <para>To refer to the instance string from
 187                 within the configuration file you may use the special
 188                 <literal>%i</literal> specifier in many of the
 189                 configuration options. Other specifiers exist, the
 190                 full list is:</para>
 191
 192                 <table>
 193                   <title>Specifiers available in unit files</title>
 194                   <tgroup cols='3' align='left' colsep='1' rowsep='1'>
 195                     <colspec colname="spec" />
 196                     <colspec colname="mean" />
 197                     <colspec colname="detail" />
 198                     <thead>
 199                       <row>
 200                         <entry>Specifier</entry>
 201                         <entry>Meaning</entry>
 202                         <entry>Details</entry>
 203                       </row>
 204                     </thead>
 205                     <tbody>
 206                       <row>
 207                         <entry><literal>%n</literal></entry>
 208                         <entry>Full unit name</entry>
 209                         <entry></entry>
 210                       </row>
 211                       <row>
 212                         <entry><literal>%N</literal></entry>
 213                         <entry>Unescaped full unit name</entry>
 214                         <entry></entry>
 215                       </row>
 216                       <row>
 217                         <entry><literal>%p</literal></entry>
 218                         <entry>Prefix name</entry>
 219                         <entry>This refers to the string before the @, i.e. "getty" in the example above, where "tty3" is the instance name.</entry>
 220                       </row>
 221                       <row>
 222                         <entry><literal>%P</literal></entry>
 223                         <entry>Unescaped prefix name</entry>
 224                         <entry></entry>
 225                       </row>
 226                       <row>
 227                         <entry><literal>%i</literal></entry>
 228                         <entry>Instance name</entry>
 229                         <entry>This is the string between the @ character and the suffix.</entry>
 230                       </row>
 231                       <row>
 232                         <entry><literal>%I</literal></entry>
 233                         <entry>Unescaped instance name</entry>
 234                         <entry></entry>
 235                       </row>
 236                       <row>
 237                         <entry><literal>%f</literal></entry>
 238                         <entry>Unescaped file name</entry>
 239                         <entry>This is either the unescaped instance name (if set) with / prepended (if necessary), or the prefix name similarly prepended with /.</entry>
 240                       </row>
 241                       <row>
 242                         <entry><literal>%c</literal></entry>
 243                         <entry>Control group path of the unit</entry>
 244                         <entry></entry>
 245                       </row>
 246                       <row>
 247                         <entry><literal>%r</literal></entry>
 248                         <entry>Root control group path of systemd</entry>
 249                         <entry></entry>
 250                       </row>
 251                       <row>
 252                         <entry><literal>%R</literal></entry>
 253                         <entry>Parent directory of the root control group path of systemd</entry>
 254                         <entry></entry>
 255                       </row>
 256                       <row>
 257                         <entry><literal>%t</literal></entry>
 258                         <entry>Runtime socket dir</entry>
 259                         <entry>This is either /run (for the system manager) or $XDG_RUNTIME_DIR (for user managers).</entry>
 260                       </row>
 261                       <row>
 262                         <entry><literal>%u</literal></entry>
 263                         <entry>User name</entry>
 264                         <entry>This is the name of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
 265                       </row>
 266                       <row>
 267                         <entry><literal>%h</literal></entry>
 268                         <entry>User home directory</entry>
 269                         <entry>This is the home directory of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
 270                       </row>
 271                       <row>
 272                         <entry><literal>%s</literal></entry>
 273                         <entry>User shell</entry>
 274                         <entry>This is the shell of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
 275                       </row>
 276                     </tbody>
 277                   </tgroup>
 278                 </table>
 279
 280                 <para>If a unit file is empty (i.e. has the file size
 281                 0) or is symlinked to <filename>/dev/null</filename>
 282                 its configuration will not be loaded and it appears
 283                 with a load state of <literal>masked</literal>, and
 284                 cannot be activated. Use this as an effective way to
 285                 fully disable a unit, making it impossible to start it
 286                 even manually.</para>
 287
 288                 <para>The unit file format is covered by the
 289                 <ulink
 290                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 291                 Stability Promise</ulink>.</para>
 292         </refsect1>
 293
 294         <refsect1>
 295                 <title>Options</title>
 296
 297                 <para>Unit file may include a [Unit] section, which
 298                 carries generic information about the unit that is not
 299                 dependent on the type of unit:</para>
 300
 301                 <variablelist>
 302
 303                         <varlistentry>
 304                                 <term><varname>Description=</varname></term>
 305                                 <listitem><para>A free-form string
 306                                 describing the unit. This is intended
 307                                 for use in UIs to show descriptive
 308                                 information along with the unit
 309                                 name.</para></listitem>
 310                         </varlistentry>
 311
 312                         <varlistentry>
 313                                 <term><varname>Documentation=</varname></term>
 314                                 <listitem><para>A space separated list
 315                                 of URIs referencing documentation for
 316                                 this unit or its
 317                                 configuration. Accepted are only URIs
 318                                 of the types
 319                                 <literal>http://</literal>,
 320                                 <literal>https://</literal>,
 321                                 <literal>file:</literal>,
 322                                 <literal>info:</literal>,
 323                                 <literal>man:</literal>. For more
 324                                 information about the syntax of these
 325                                 URIs see
 326                                 <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
 327                         </varlistentry>
 328
 329                         <varlistentry>
 330                                 <term><varname>Requires=</varname></term>
 331
 332                                 <listitem><para>Configures requirement
 333                                 dependencies on other units. If this
 334                                 unit gets activated, the units listed
 335                                 here will be activated as well. If one
 336                                 of the other units gets deactivated or
 337                                 its activation fails, this unit will
 338                                 be deactivated. This option may be
 339                                 specified more than once, in which
 340                                 case requirement dependencies for all
 341                                 listed names are created. Note that
 342                                 requirement dependencies do not
 343                                 influence the order in which services
 344                                 are started or stopped. This has to be
 345                                 configured independently with the
 346                                 <varname>After=</varname> or
 347                                 <varname>Before=</varname> options. If
 348                                 a unit
 349                                 <filename>foo.service</filename>
 350                                 requires a unit
 351                                 <filename>bar.service</filename> as
 352                                 configured with
 353                                 <varname>Requires=</varname> and no
 354                                 ordering is configured with
 355                                 <varname>After=</varname> or
 356                                 <varname>Before=</varname>, then both
 357                                 units will be started simultaneously
 358                                 and without any delay between them if
 359                                 <filename>foo.service</filename> is
 360                                 activated. Often it is a better choice
 361                                 to use <varname>Wants=</varname>
 362                                 instead of
 363                                 <varname>Requires=</varname> in order
 364                                 to achieve a system that is more
 365                                 robust when dealing with failing
 366                                 services.</para>
 367
 368                                 <para>Note that dependencies of this
 369                                 type may also be configured outside of
 370                                 the unit configuration file by
 371                                 adding a symlink to a
 372                                 <filename>.requires/</filename> directory
 373                                 accompanying the unit file. For
 374                                 details see above.</para></listitem>
 375                         </varlistentry>
 376
 377                         <varlistentry>
 378                                 <term><varname>RequiresOverridable=</varname></term>
 379
 380                                 <listitem><para>Similar to
 381                                 <varname>Requires=</varname>.
 382                                 Dependencies listed in
 383                                 <varname>RequiresOverridable=</varname>
 384                                 which cannot be fulfilled or fail to
 385                                 start are ignored if the startup was
 386                                 explicitly requested by the user. If
 387                                 the start-up was pulled in indirectly
 388                                 by some dependency or automatic
 389                                 start-up of units that is not
 390                                 requested by the user this dependency
 391                                 must be fulfilled and otherwise the
 392                                 transaction fails. Hence, this option
 393                                 may be used to configure dependencies
 394                                 that are normally honored unless the
 395                                 user explicitly starts up the unit, in
 396                                 which case whether they failed or not
 397                                 is irrelevant.</para></listitem>
 398
 399                         </varlistentry>
 400                         <varlistentry>
 401                                 <term><varname>Requisite=</varname></term>
 402                                 <term><varname>RequisiteOverridable=</varname></term>
 403
 404                                 <listitem><para>Similar to
 405                                 <varname>Requires=</varname>
 406                                 resp. <varname>RequiresOverridable=</varname>. However,
 407                                 if a unit listed here is not started
 408                                 already it will not be started and the
 409                                 transaction fails
 410                                 immediately.</para></listitem>
 411                         </varlistentry>
 412
 413                         <varlistentry>
 414                                 <term><varname>Wants=</varname></term>
 415
 416                                 <listitem><para>A weaker version of
 417                                 <varname>Requires=</varname>. A unit
 418                                 listed in this option will be started
 419                                 if the configuring unit is. However,
 420                                 if the listed unit fails to start up
 421                                 or cannot be added to the transaction
 422                                 this has no impact on the validity of
 423                                 the transaction as a whole. This is
 424                                 the recommended way to hook start-up
 425                                 of one unit to the start-up of another
 426                                 unit.</para>
 427
 428                                 <para>Note that dependencies of this
 429                                 type may also be configured outside of
 430                                 the unit configuration file by
 431                                 adding a symlink to a
 432                                 <filename>.wants/</filename> directory
 433                                 accompanying the unit file. For
 434                                 details see above.</para></listitem>
 435                         </varlistentry>
 436
 437                         <varlistentry>
 438                                 <term><varname>BindsTo=</varname></term>
 439
 440                                 <listitem><para>Configures requirement
 441                                 dependencies, very similar in style to
 442                                 <varname>Requires=</varname>, however
 443                                 in addition to this behaviour it also
 444                                 declares that this unit is stopped
 445                                 when any of the units listed suddenly
 446                                 disappears. Units can suddenly,
 447                                 unexpectedly disappear if a service
 448                                 terminates on its own choice, a device
 449                                 is unplugged or a mount point
 450                                 unmounted without involvement of
 451                                 systemd.</para></listitem>
 452                         </varlistentry>
 453
 454                         <varlistentry>
 455                                 <term><varname>PartOf=</varname></term>
 456
 457                                 <listitem><para>Configures dependencies
 458                                 similar to <varname>Requires=</varname>,
 459                                 but limited to stopping and restarting
 460                                 of units. When systemd stops or restarts
 461                                 the units listed here, the action is
 462                                 propagated to this unit.
 463                                 Note that this is a one way dependency -
 464                                 changes to this unit do not affect the
 465                                 listed units.
 466                                 </para></listitem>
 467                         </varlistentry>
 468
 469                         <varlistentry>
 470                                 <term><varname>Conflicts=</varname></term>
 471
 472                                 <listitem><para>Configures negative
 473                                 requirement dependencies. If a unit
 474                                 has a
 475                                 <varname>Conflicts=</varname> setting
 476                                 on another unit, starting the former
 477                                 will stop the latter and vice
 478                                 versa. Note that this setting is
 479                                 independent of and orthogonal to the
 480                                 <varname>After=</varname> and
 481                                 <varname>Before=</varname> ordering
 482                                 dependencies.</para>
 483
 484                                 <para>If a unit A that conflicts with
 485                                 a unit B is scheduled to be started at
 486                                 the same time as B, the transaction
 487                                 will either fail (in case both are
 488                                 required part of the transaction) or
 489                                 be modified to be fixed (in case one
 490                                 or both jobs are not a required part
 491                                 of the transaction). In the latter
 492                                 case the job that is not the required
 493                                 will be removed, or in case both are
 494                                 not required the unit that conflicts
 495                                 will be started and the unit that is
 496                                 conflicted is
 497                                 stopped.</para></listitem>
 498                         </varlistentry>
 499
 500                         <varlistentry>
 501                                 <term><varname>Before=</varname></term>
 502                                 <term><varname>After=</varname></term>
 503
 504                                 <listitem><para>Configures ordering
 505                                 dependencies between units. If a unit
 506                                 <filename>foo.service</filename>
 507                                 contains a setting
 508                                 <option>Before=bar.service</option>
 509                                 and both units are being started,
 510                                 <filename>bar.service</filename>'s
 511                                 start-up is delayed until
 512                                 <filename>foo.service</filename> is
 513                                 started up. Note that this setting is
 514                                 independent of and orthogonal to the
 515                                 requirement dependencies as configured
 516                                 by <varname>Requires=</varname>. It is
 517                                 a common pattern to include a unit
 518                                 name in both the
 519                                 <varname>After=</varname> and
 520                                 <varname>Requires=</varname> option in
 521                                 which case the unit listed will be
 522                                 started before the unit that is
 523                                 configured with these options. This
 524                                 option may be specified more than
 525                                 once, in which case ordering
 526                                 dependencies for all listed names are
 527                                 created. <varname>After=</varname> is
 528                                 the inverse of
 529                                 <varname>Before=</varname>, i.e. while
 530                                 <varname>After=</varname> ensures that
 531                                 the configured unit is started after
 532                                 the listed unit finished starting up,
 533                                 <varname>Before=</varname> ensures the
 534                                 opposite, i.e.  that the configured
 535                                 unit is fully started up before the
 536                                 listed unit is started. Note that when
 537                                 two units with an ordering dependency
 538                                 between them are shut down, the
 539                                 inverse of the start-up order is
 540                                 applied. i.e. if a unit is configured
 541                                 with <varname>After=</varname> on
 542                                 another unit, the former is stopped
 543                                 before the latter if both are shut
 544                                 down. If one unit with an ordering
 545                                 dependency on another unit is shut
 546                                 down while the latter is started up,
 547                                 the shut down is ordered before the
 548                                 start-up regardless whether the
 549                                 ordering dependency is actually of
 550                                 type <varname>After=</varname> or
 551                                 <varname>Before=</varname>. If two
 552                                 units have no ordering dependencies
 553                                 between them they are shut down
 554                                 resp. started up simultaneously, and
 555                                 no ordering takes
 556                                 place. </para></listitem>
 557                         </varlistentry>
 558
 559                         <varlistentry>
 560                                 <term><varname>OnFailure=</varname></term>
 561
 562                                 <listitem><para>Lists one or more
 563                                 units that are activated when this
 564                                 unit enters the
 565                                 '<literal>failed</literal>'
 566                                 state.</para></listitem>
 567                         </varlistentry>
 568
 569                         <varlistentry>
 570                                 <term><varname>PropagatesReloadTo=</varname></term>
 571                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 572
 573                                 <listitem><para>Lists one or more
 574                                 units where reload requests on the
 575                                 unit will be propagated to/on the
 576                                 other unit will be propagated
 577                                 from. Issuing a reload request on a
 578                                 unit will automatically also enqueue a
 579                                 reload request on all units that the
 580                                 reload request shall be propagated to
 581                                 via these two
 582                                 settings.</para></listitem>
 583                         </varlistentry>
 584
 585                         <varlistentry>
 586                                 <term><varname>RequiresMountsFor=</varname></term>
 587
 588                                 <listitem><para>Takes a space
 589                                 separated list of absolute paths. Automatically
 590                                 adds dependencies of type
 591                                 <varname>Requires=</varname> and
 592                                 <varname>After=</varname> for all
 593                                 mount units required to access the
 594                                 specified path.</para></listitem>
 595                         </varlistentry>
 596
 597                         <varlistentry>
 598                                 <term><varname>OnFailureIsolate=</varname></term>
 599
 600                                 <listitem><para>Takes a boolean
 601                                 argument. If <option>true</option> the
 602                                 unit listed in
 603                                 <varname>OnFailure=</varname> will be
 604                                 enqueued in isolation mode, i.e. all
 605                                 units that are not its dependency will
 606                                 be stopped. If this is set only a
 607                                 single unit may be listed in
 608                                 <varname>OnFailure=</varname>. Defaults
 609                                 to
 610                                 <option>false</option>.</para></listitem>
 611                         </varlistentry>
 612
 613                         <varlistentry>
 614                                 <term><varname>IgnoreOnIsolate=</varname></term>
 615
 616                                 <listitem><para>Takes a boolean
 617                                 argument. If <option>true</option>
 618                                 this unit will not be stopped when
 619                                 isolating another unit. Defaults to
 620                                 <option>false</option>.</para></listitem>
 621                         </varlistentry>
 622
 623                         <varlistentry>
 624                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 625
 626                                 <listitem><para>Takes a boolean
 627                                 argument. If <option>true</option>
 628                                 this unit will not be included in
 629                                 snapshots. Defaults to
 630                                 <option>true</option> for device and
 631                                 snapshot units, <option>false</option>
 632                                 for the others.</para></listitem>
 633                         </varlistentry>
 634
 635                         <varlistentry>
 636                                 <term><varname>StopWhenUnneeded=</varname></term>
 637
 638                                 <listitem><para>Takes a boolean
 639                                 argument. If <option>true</option>
 640                                 this unit will be stopped when it is
 641                                 no longer used. Note that in order to
 642                                 minimize the work to be executed,
 643                                 systemd will not stop units by default
 644                                 unless they are conflicting with other
 645                                 units, or the user explicitly
 646                                 requested their shut down. If this
 647                                 option is set, a unit will be
 648                                 automatically cleaned up if no other
 649                                 active unit requires it. Defaults to
 650                                 <option>false</option>.</para></listitem>
 651                         </varlistentry>
 652
 653                         <varlistentry>
 654                                 <term><varname>RefuseManualStart=</varname></term>
 655                                 <term><varname>RefuseManualStop=</varname></term>
 656
 657                                 <listitem><para>Takes a boolean
 658                                 argument. If <option>true</option>
 659                                 this unit can only be activated
 660                                 (resp. deactivated) indirectly. In
 661                                 this case explicit start-up
 662                                 (resp. termination) requested by the
 663                                 user is denied, however if it is
 664                                 started (resp. stopped) as a
 665                                 dependency of another unit, start-up
 666                                 (resp. termination) will succeed. This
 667                                 is mostly a safety feature to ensure
 668                                 that the user does not accidentally
 669                                 activate units that are not intended
 670                                 to be activated explicitly, and not
 671                                 accidentally deactivate units that are
 672                                 not intended to be deactivated.
 673                                 These options default to
 674                                 <option>false</option>.</para></listitem>
 675                         </varlistentry>
 676
 677                         <varlistentry>
 678                                 <term><varname>AllowIsolate=</varname></term>
 679
 680                                 <listitem><para>Takes a boolean
 681                                 argument. If <option>true</option>
 682                                 this unit may be used with the
 683                                 <command>systemctl isolate</command>
 684                                 command. Otherwise this will be
 685                                 refused. It probably is a good idea to
 686                                 leave this disabled except for target
 687                                 units that shall be used similar to
 688                                 runlevels in SysV init systems, just
 689                                 as a precaution to avoid unusable
 690                                 system states. This option defaults to
 691                                 <option>false</option>.</para></listitem>
 692                         </varlistentry>
 693
 694                         <varlistentry>
 695                                 <term><varname>DefaultDependencies=</varname></term>
 696
 697                                 <listitem><para>Takes a boolean
 698                                 argument. If <option>true</option>
 699                                 (the default), a few default
 700                                 dependencies will implicitly be
 701                                 created for the unit. The actual
 702                                 dependencies created depend on the
 703                                 unit type. For example, for service
 704                                 units, these dependencies ensure that
 705                                 the service is started only after
 706                                 basic system initialization is
 707                                 completed and is properly terminated on
 708                                 system shutdown. See the respective
 709                                 man pages for details. Generally, only
 710                                 services involved with early boot or
 711                                 late shutdown should set this option
 712                                 to <option>false</option>. It is
 713                                 highly recommended to leave this
 714                                 option enabled for the majority of
 715                                 common units. If set to
 716                                 <option>false</option> this option
 717                                 does not disable all implicit
 718                                 dependencies, just non-essential
 719                                 ones.</para></listitem>
 720                         </varlistentry>
 721
 722                         <varlistentry>
 723                                 <term><varname>JobTimeoutSec=</varname></term>
 724
 725                                 <listitem><para>When clients are
 726                                 waiting for a job of this unit to
 727                                 complete, time out after the specified
 728                                 time. If this time limit is reached
 729                                 the job will be cancelled, the unit
 730                                 however will not change state or even
 731                                 enter the '<literal>failed</literal>'
 732                                 mode. This value defaults to 0 (job
 733                                 timeouts disabled), except for device
 734                                 units. NB: this timeout is independent
 735                                 from any unit-specific timeout (for
 736                                 example, the timeout set with
 737                                 <varname>Timeout=</varname> in service
 738                                 units) as the job timeout has no
 739                                 effect on the unit itself, only on the
 740                                 job that might be pending for it. Or
 741                                 in other words: unit-specific timeouts
 742                                 are useful to abort unit state
 743                                 changes, and revert them. The job
 744                                 timeout set with this option however
 745                                 is useful to abort only the job
 746                                 waiting for the unit state to
 747                                 change.</para></listitem>
 748                         </varlistentry>
 749
 750                         <varlistentry>
 751                                 <term><varname>ConditionPathExists=</varname></term>
 752                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 753                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 754                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 755                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 756                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 757                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 758                                 <term><varname>ConditionFileNotEmpty=</varname></term>
 759                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 760                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 761                                 <term><varname>ConditionVirtualization=</varname></term>
 762                                 <term><varname>ConditionSecurity=</varname></term>
 763                                 <term><varname>ConditionCapability=</varname></term>
 764                                 <term><varname>ConditionHost=</varname></term>
 765                                 <term><varname>ConditionNull=</varname></term>
 766
 767                                 <listitem><para>Before starting a unit
 768                                 verify that the specified condition is
 769                                 true. If it is not true the starting
 770                                 of the unit will be skipped, however
 771                                 all ordering dependencies of it are
 772                                 still respected. A failing condition
 773                                 will not result in the unit being
 774                                 moved into a failure state. The
 775                                 condition is checked at the time the
 776                                 queued start job is to be
 777                                 executed.</para>
 778
 779                                 <para>With
 780                                 <varname>ConditionPathExists=</varname>
 781                                 a file existence condition is
 782                                 checked before a unit is started. If
 783                                 the specified absolute path name does
 784                                 not exist the condition will
 785                                 fail. If the absolute path name passed
 786                                 to
 787                                 <varname>ConditionPathExists=</varname>
 788                                 is prefixed with an exclamation mark
 789                                 ('!'), the test is negated, and the unit
 790                                 is only started if the path does not
 791                                 exist.</para>
 792
 793                                 <para><varname>ConditionPathExistsGlob=</varname>
 794                                 is similar to
 795                                 <varname>ConditionPathExists=</varname>,
 796                                 but checks for the existence of at
 797                                 least one file or directory matching
 798                                 the specified globbing pattern.</para>
 799
 800                                 <para><varname>ConditionPathIsDirectory=</varname>
 801                                 is similar to
 802                                 <varname>ConditionPathExists=</varname>
 803                                 but verifies whether a certain path
 804                                 exists and is a
 805                                 directory.</para>
 806
 807                                 <para><varname>ConditionPathIsSymbolicLink=</varname>
 808                                 is similar to
 809                                 <varname>ConditionPathExists=</varname>
 810                                 but verifies whether a certain path
 811                                 exists and is a symbolic
 812                                 link.</para>
 813
 814                                 <para><varname>ConditionPathIsMountPoint=</varname>
 815                                 is similar to
 816                                 <varname>ConditionPathExists=</varname>
 817                                 but verifies whether a certain path
 818                                 exists and is a mount
 819                                 point.</para>
 820
 821                                 <para><varname>ConditionPathIsReadWrite=</varname>
 822                                 is similar to
 823                                 <varname>ConditionPathExists=</varname>
 824                                 but verifies whether the underlying
 825                                 file system is readable and writable
 826                                 (i.e. not mounted
 827                                 read-only).</para>
 828
 829                                 <para><varname>ConditionDirectoryNotEmpty=</varname>
 830                                 is similar to
 831                                 <varname>ConditionPathExists=</varname>
 832                                 but verifies whether a certain path
 833                                 exists and is a non-empty
 834                                 directory.</para>
 835
 836                                 <para><varname>ConditionFileNotEmpty=</varname>
 837                                 is similar to
 838                                 <varname>ConditionPathExists=</varname>
 839                                 but verifies whether a certain path
 840                                 exists and refers to a regular file
 841                                 with a non-zero size.</para>
 842
 843                                 <para><varname>ConditionFileIsExecutable=</varname>
 844                                 is similar to
 845                                 <varname>ConditionPathExists=</varname>
 846                                 but verifies whether a certain path
 847                                 exists, is a regular file and marked
 848                                 executable.</para>
 849
 850                                 <para>Similar,
 851                                 <varname>ConditionKernelCommandLine=</varname>
 852                                 may be used to check whether a
 853                                 specific kernel command line option is
 854                                 set (or if prefixed with the
 855                                 exclamation mark unset). The argument
 856                                 must either be a single word, or an
 857                                 assignment (i.e. two words, separated
 858                                 '='). In the former
 859                                 case the kernel command line is
 860                                 searched for the word appearing as is,
 861                                 or as left hand side of an
 862                                 assignment. In the latter case the
 863                                 exact assignment is looked for with
 864                                 right and left hand side
 865                                 matching.</para>
 866
 867                                 <para><varname>ConditionVirtualization=</varname>
 868                                 may be used to check whether the
 869                                 system is executed in a virtualized
 870                                 environment and optionally test
 871                                 whether it is a specific
 872                                 implementation. Takes either boolean
 873                                 value to check if being executed in
 874                                 any virtualized environment, or one of
 875                                 <varname>vm</varname> and
 876                                 <varname>container</varname> to test
 877                                 against a generic type of
 878                                 virtualization solution, or one of
 879                                 <varname>qemu</varname>,
 880                                 <varname>kvm</varname>,
 881                                 <varname>vmware</varname>,
 882                                 <varname>microsoft</varname>,
 883                                 <varname>oracle</varname>,
 884                                 <varname>xen</varname>,
 885                                 <varname>bochs</varname>,
 886                                 <varname>chroot</varname>,
 887                                 <varname>openvz</varname>,
 888                                 <varname>lxc</varname>,
 889                                 <varname>lxc-libvirt</varname>,
 890                                 <varname>systemd-nspawn</varname> to
 891                                 test against a specific
 892                                 implementation. If multiple
 893                                 virtualization technologies are nested
 894                                 only the innermost is considered. The
 895                                 test may be negated by prepending an
 896                                 exclamation mark.</para>
 897
 898                                 <para><varname>ConditionSecurity=</varname>
 899                                 may be used to check whether the given
 900                                 security module is enabled on the
 901                                 system.  Currently the only recognized
 902                                 value is <varname>selinux</varname>.
 903                                 The test may be negated by prepending
 904                                 an exclamation
 905                                 mark.</para>
 906
 907                                 <para><varname>ConditionCapability=</varname>
 908                                 may be used to check whether the given
 909                                 capability exists in the capability
 910                                 bounding set of the service manager
 911                                 (i.e. this does not check whether
 912                                 capability is actually available in
 913                                 the permitted or effective sets, see
 914                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 915                                 for details). Pass a capability name
 916                                 such as <literal>CAP_MKNOD</literal>,
 917                                 possibly prefixed with an exclamation
 918                                 mark to negate the check.</para>
 919
 920                                 <para><varname>ConditionHost=</varname>
 921                                 may be used to match against the
 922                                 host name or machine ID of the
 923                                 host. This either takes a host name
 924                                 string (optionally with shell style
 925                                 globs) which is tested against the
 926                                 locally set host name as returned by
 927                                 <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 928                                 or a machine ID formatted as string
 929                                 (see
 930                                 <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
 931                                 The test may be negated by prepending
 932                                 an exclamation mark.</para>
 933
 934                                 <para>Finally,
 935                                 <varname>ConditionNull=</varname> may
 936                                 be used to add a constant condition
 937                                 check value to the unit. It takes a
 938                                 boolean argument. If set to
 939                                 <varname>false</varname> the condition
 940                                 will always fail, otherwise
 941                                 succeed.</para>
 942
 943                                 <para>If multiple conditions are
 944                                 specified the unit will be executed if
 945                                 all of them apply (i.e. a logical AND
 946                                 is applied). Condition checks can be
 947                                 prefixed with a pipe symbol (|) in
 948                                 which case a condition becomes a
 949                                 triggering condition. If at least one
 950                                 triggering condition is defined for a
 951                                 unit then the unit will be executed if
 952                                 at least one of the triggering
 953                                 conditions apply and all of the
 954                                 non-triggering conditions. If you
 955                                 prefix an argument with the pipe
 956                                 symbol and an exclamation mark the
 957                                 pipe symbol must be passed first, the
 958                                 exclamation second. Except for
 959                                 <varname>ConditionPathIsSymbolicLink=</varname>,
 960                                 all path checks follow
 961                                 symlinks.</para></listitem>
 962                         </varlistentry>
 963
 964                         <varlistentry>
 965                                 <term><varname>SourcePath=</varname></term>
 966                                 <listitem><para>A path to a
 967                                 configuration file this unit has been
 968                                 generated from. This is primarily
 969                                 useful for implementation of generator
 970                                 tools that convert configuration from
 971                                 an external configuration file format
 972                                 into native unit files. Thus
 973                                 functionality should not be used in
 974                                 normal units.</para></listitem>
 975                         </varlistentry>
 976                 </variablelist>
 977
 978                 <para>Unit file may include a [Install] section, which
 979                 carries installation information for the unit. This
 980                 section is not interpreted by
 981                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 982                 during runtime. It is used exclusively by the
 983                 <command>enable</command> and
 984                 <command>disable</command> commands of the
 985                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 986                 tool during installation of a unit:</para>
 987
 988                 <variablelist>
 989                         <varlistentry>
 990                                 <term><varname>Alias=</varname></term>
 991
 992                                 <listitem><para>Additional names this
 993                                 unit shall be installed under. The
 994                                 names listed here must have the same
 995                                 suffix (i.e. type) as the unit file
 996                                 name. This option may be specified
 997                                 more than once, in which case all
 998                                 listed names are used. At installation
 999                                 time,
1000                                 <command>systemctl enable</command>
1001                                 will create symlinks from these names
1002                                 to the unit file name.</para></listitem>
1003                         </varlistentry>
1004
1005                         <varlistentry>
1006                                 <term><varname>WantedBy=</varname></term>
1007                                 <term><varname>RequiredBy=</varname></term>
1008
1009                                 <listitem><para>Installs a symlink in
1010                                 the <filename>.wants/</filename>
1011                                 resp. <filename>.requires/</filename>
1012                                 subdirectory for a unit. This has the
1013                                 effect that when the listed unit name
1014                                 is activated the unit listing it is
1015                                 activated
1016                                 too. <command>WantedBy=foo.service</command>
1017                                 in a service
1018                                 <filename>bar.service</filename> is
1019                                 mostly equivalent to
1020                                 <command>Alias=foo.service.wants/bar.service</command>
1021                                 in the same file.</para></listitem>
1022                         </varlistentry>
1023
1024                         <varlistentry>
1025                                 <term><varname>Also=</varname></term>
1026
1027                                 <listitem><para>Additional units to
1028                                 install when this unit is
1029                                 installed. If the user requests
1030                                 installation of a unit with this
1031                                 option configured,
1032                                 <command>systemctl enable</command>
1033                                 will automatically install units
1034                                 listed in this option as
1035                                 well.</para></listitem>
1036                         </varlistentry>
1037                 </variablelist>
1038
1039         </refsect1>
1040
1041         <refsect1>
1042                 <title>See Also</title>
1043                 <para>
1044                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1045                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1046                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1047                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1048                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1049                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1050                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1051                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1052                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1053                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1054                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1055                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1056                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1057                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1058                 </para>
1059         </refsect1>
1060
1061 </refentry>