man/systemd.unit.xml

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