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></listitem>
 367                         </varlistentry>
 368
 369                         <varlistentry>
 370                                 <term><varname>RequiresOverridable=</varname></term>
 371
 372                                 <listitem><para>Similar to
 373                                 <varname>Requires=</varname>.
 374                                 Dependencies listed in
 375                                 <varname>RequiresOverridable=</varname>
 376                                 which cannot be fulfilled or fail to
 377                                 start are ignored if the startup was
 378                                 explicitly requested by the user. If
 379                                 the start-up was pulled in indirectly
 380                                 by some dependency or automatic
 381                                 start-up of units that is not
 382                                 requested by the user this dependency
 383                                 must be fulfilled and otherwise the
 384                                 transaction fails. Hence, this option
 385                                 may be used to configure dependencies
 386                                 that are normally honored unless the
 387                                 user explicitly starts up the unit, in
 388                                 which case whether they failed or not
 389                                 is irrelevant.</para></listitem>
 390
 391                         </varlistentry>
 392                         <varlistentry>
 393                                 <term><varname>Requisite=</varname></term>
 394                                 <term><varname>RequisiteOverridable=</varname></term>
 395
 396                                 <listitem><para>Similar to
 397                                 <varname>Requires=</varname>
 398                                 resp. <varname>RequiresOverridable=</varname>. However,
 399                                 if a unit listed here is not started
 400                                 already it will not be started and the
 401                                 transaction fails
 402                                 immediately.</para></listitem>
 403                         </varlistentry>
 404
 405                         <varlistentry>
 406                                 <term><varname>Wants=</varname></term>
 407
 408                                 <listitem><para>A weaker version of
 409                                 <varname>Requires=</varname>. A unit
 410                                 listed in this option will be started
 411                                 if the configuring unit is. However,
 412                                 if the listed unit fails to start up
 413                                 or cannot be added to the transaction
 414                                 this has no impact on the validity of
 415                                 the transaction as a whole. This is
 416                                 the recommended way to hook start-up
 417                                 of one unit to the start-up of another
 418                                 unit. Note that dependencies of this
 419                                 type may also be configured outside of
 420                                 the unit configuration file by
 421                                 adding a symlink to a
 422                                 <filename>.wants/</filename> directory
 423                                 accompanying the unit file. For
 424                                 details see above.</para></listitem>
 425                         </varlistentry>
 426
 427                         <varlistentry>
 428                                 <term><varname>BindsTo=</varname></term>
 429
 430                                 <listitem><para>Configures requirement
 431                                 dependencies, very similar in style to
 432                                 <varname>Requires=</varname>, however
 433                                 in addition to this behaviour it also
 434                                 declares that this unit is stopped
 435                                 when any of the units listed suddenly
 436                                 disappears. Units can suddenly,
 437                                 unexpectedly disappear if a service
 438                                 terminates on its own choice, a device
 439                                 is unplugged or a mount point
 440                                 unmounted without involvement of
 441                                 systemd.</para></listitem>
 442                         </varlistentry>
 443
 444                         <varlistentry>
 445                                 <term><varname>Conflicts=</varname></term>
 446
 447                                 <listitem><para>Configures negative
 448                                 requirement dependencies. If a unit
 449                                 has a
 450                                 <varname>Conflicts=</varname> setting
 451                                 on another unit, starting the former
 452                                 will stop the latter and vice
 453                                 versa. Note that this setting is
 454                                 independent of and orthogonal to the
 455                                 <varname>After=</varname> and
 456                                 <varname>Before=</varname> ordering
 457                                 dependencies.</para>
 458
 459                                 <para>If a unit A that conflicts with
 460                                 a unit B is scheduled to be started at
 461                                 the same time as B, the transaction
 462                                 will either fail (in case both are
 463                                 required part of the transaction) or
 464                                 be modified to be fixed (in case one
 465                                 or both jobs are not a required part
 466                                 of the transaction). In the latter
 467                                 case the job that is not the required
 468                                 will be removed, or in case both are
 469                                 not required the unit that conflicts
 470                                 will be started and the unit that is
 471                                 conflicted is
 472                                 stopped.</para></listitem>
 473                         </varlistentry>
 474
 475                         <varlistentry>
 476                                 <term><varname>Before=</varname></term>
 477                                 <term><varname>After=</varname></term>
 478
 479                                 <listitem><para>Configures ordering
 480                                 dependencies between units. If a unit
 481                                 <filename>foo.service</filename>
 482                                 contains a setting
 483                                 <option>Before=bar.service</option>
 484                                 and both units are being started,
 485                                 <filename>bar.service</filename>'s
 486                                 start-up is delayed until
 487                                 <filename>foo.service</filename> is
 488                                 started up. Note that this setting is
 489                                 independent of and orthogonal to the
 490                                 requirement dependencies as configured
 491                                 by <varname>Requires=</varname>. It is
 492                                 a common pattern to include a unit
 493                                 name in both the
 494                                 <varname>After=</varname> and
 495                                 <varname>Requires=</varname> option in
 496                                 which case the unit listed will be
 497                                 started before the unit that is
 498                                 configured with these options. This
 499                                 option may be specified more than
 500                                 once, in which case ordering
 501                                 dependencies for all listed names are
 502                                 created. <varname>After=</varname> is
 503                                 the inverse of
 504                                 <varname>Before=</varname>, i.e. while
 505                                 <varname>After=</varname> ensures that
 506                                 the configured unit is started after
 507                                 the listed unit finished starting up,
 508                                 <varname>Before=</varname> ensures the
 509                                 opposite, i.e.  that the configured
 510                                 unit is fully started up before the
 511                                 listed unit is started. Note that when
 512                                 two units with an ordering dependency
 513                                 between them are shut down, the
 514                                 inverse of the start-up order is
 515                                 applied. i.e. if a unit is configured
 516                                 with <varname>After=</varname> on
 517                                 another unit, the former is stopped
 518                                 before the latter if both are shut
 519                                 down. If one unit with an ordering
 520                                 dependency on another unit is shut
 521                                 down while the latter is started up,
 522                                 the shut down is ordered before the
 523                                 start-up regardless whether the
 524                                 ordering dependency is actually of
 525                                 type <varname>After=</varname> or
 526                                 <varname>Before=</varname>. If two
 527                                 units have no ordering dependencies
 528                                 between them they are shut down
 529                                 resp. started up simultaneously, and
 530                                 no ordering takes
 531                                 place. </para></listitem>
 532                         </varlistentry>
 533
 534                         <varlistentry>
 535                                 <term><varname>OnFailure=</varname></term>
 536
 537                                 <listitem><para>Lists one or more
 538                                 units that are activated when this
 539                                 unit enters the
 540                                 '<literal>failed</literal>'
 541                                 state.</para></listitem>
 542                         </varlistentry>
 543
 544                         <varlistentry>
 545                                 <term><varname>PropagatesReloadTo=</varname></term>
 546                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 547
 548                                 <listitem><para>Lists one or more
 549                                 units where reload requests on the
 550                                 unit will be propagated to/on the
 551                                 other unit will be propagated
 552                                 from. Issuing a reload request on a
 553                                 unit will automatically also enqueue a
 554                                 reload request on all units that the
 555                                 reload request shall be propagated to
 556                                 via these two
 557                                 settings.</para></listitem>
 558                         </varlistentry>
 559
 560                         <varlistentry>
 561                                 <term><varname>RequiresMountsFor=</varname></term>
 562
 563                                 <listitem><para>Takes a space
 564                                 separated list of paths. Automatically
 565                                 adds dependencies of type
 566                                 <varname>Requires=</varname> and
 567                                 <varname>After=</varname> for all
 568                                 mount units required to access the
 569                                 specified path.</para></listitem>
 570                         </varlistentry>
 571
 572                         <varlistentry>
 573                                 <term><varname>OnFailureIsolate=</varname></term>
 574
 575                                 <listitem><para>Takes a boolean
 576                                 argument. If <option>true</option> the
 577                                 unit listed in
 578                                 <varname>OnFailure=</varname> will be
 579                                 enqueued in isolation mode, i.e. all
 580                                 units that are not its dependency will
 581                                 be stopped. If this is set only a
 582                                 single unit may be listed in
 583                                 <varname>OnFailure=</varname>. Defaults
 584                                 to
 585                                 <option>false</option>.</para></listitem>
 586                         </varlistentry>
 587
 588                         <varlistentry>
 589                                 <term><varname>IgnoreOnIsolate=</varname></term>
 590
 591                                 <listitem><para>Takes a boolean
 592                                 argument. If <option>true</option>
 593                                 this unit will not be stopped when
 594                                 isolating another unit. Defaults to
 595                                 <option>false</option>.</para></listitem>
 596                         </varlistentry>
 597
 598                         <varlistentry>
 599                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 600
 601                                 <listitem><para>Takes a boolean
 602                                 argument. If <option>true</option>
 603                                 this unit will not be included in
 604                                 snapshots. Defaults to
 605                                 <option>true</option> for device and
 606                                 snapshot units, <option>false</option>
 607                                 for the others.</para></listitem>
 608                         </varlistentry>
 609
 610                         <varlistentry>
 611                                 <term><varname>StopWhenUnneeded=</varname></term>
 612
 613                                 <listitem><para>Takes a boolean
 614                                 argument. If <option>true</option>
 615                                 this unit will be stopped when it is
 616                                 no longer used. Note that in order to
 617                                 minimize the work to be executed,
 618                                 systemd will not stop units by default
 619                                 unless they are conflicting with other
 620                                 units, or the user explicitly
 621                                 requested their shut down. If this
 622                                 option is set, a unit will be
 623                                 automatically cleaned up if no other
 624                                 active unit requires it. Defaults to
 625                                 <option>false</option>.</para></listitem>
 626                         </varlistentry>
 627
 628                         <varlistentry>
 629                                 <term><varname>RefuseManualStart=</varname></term>
 630                                 <term><varname>RefuseManualStop=</varname></term>
 631
 632                                 <listitem><para>Takes a boolean
 633                                 argument. If <option>true</option>
 634                                 this unit can only be activated
 635                                 (resp. deactivated) indirectly. In
 636                                 this case explicit start-up
 637                                 (resp. termination) requested by the
 638                                 user is denied, however if it is
 639                                 started (resp. stopped) as a
 640                                 dependency of another unit, start-up
 641                                 (resp. termination) will succeed. This
 642                                 is mostly a safety feature to ensure
 643                                 that the user does not accidentally
 644                                 activate units that are not intended
 645                                 to be activated explicitly, and not
 646                                 accidentally deactivate units that are
 647                                 not intended to be deactivated.
 648                                 These options default to
 649                                 <option>false</option>.</para></listitem>
 650                         </varlistentry>
 651
 652                         <varlistentry>
 653                                 <term><varname>AllowIsolate=</varname></term>
 654
 655                                 <listitem><para>Takes a boolean
 656                                 argument. If <option>true</option>
 657                                 this unit may be used with the
 658                                 <command>systemctl isolate</command>
 659                                 command. Otherwise this will be
 660                                 refused. It probably is a good idea to
 661                                 leave this disabled except for target
 662                                 units that shall be used similar to
 663                                 runlevels in SysV init systems, just
 664                                 as a precaution to avoid unusable
 665                                 system states. This option defaults to
 666                                 <option>false</option>.</para></listitem>
 667                         </varlistentry>
 668
 669                         <varlistentry>
 670                                 <term><varname>DefaultDependencies=</varname></term>
 671
 672                                 <listitem><para>Takes a boolean
 673                                 argument. If <option>true</option>
 674                                 (the default), a few default
 675                                 dependencies will implicitly be
 676                                 created for the unit. The actual
 677                                 dependencies created depend on the
 678                                 unit type. For example, for service
 679                                 units, these dependencies ensure that
 680                                 the service is started only after
 681                                 basic system initialization is
 682                                 completed and is properly terminated on
 683                                 system shutdown. See the respective
 684                                 man pages for details. Generally, only
 685                                 services involved with early boot or
 686                                 late shutdown should set this option
 687                                 to <option>false</option>. It is
 688                                 highly recommended to leave this
 689                                 option enabled for the majority of
 690                                 common units. If set to
 691                                 <option>false</option> this option
 692                                 does not disable all implicit
 693                                 dependencies, just non-essential
 694                                 ones.</para></listitem>
 695                         </varlistentry>
 696
 697                         <varlistentry>
 698                                 <term><varname>JobTimeoutSec=</varname></term>
 699
 700                                 <listitem><para>When clients are
 701                                 waiting for a job of this unit to
 702                                 complete, time out after the specified
 703                                 time. If this time limit is reached
 704                                 the job will be cancelled, the unit
 705                                 however will not change state or even
 706                                 enter the '<literal>failed</literal>'
 707                                 mode. This value defaults to 0 (job
 708                                 timeouts disabled), except for device
 709                                 units. NB: this timeout is independent
 710                                 from any unit-specific timeout (for
 711                                 example, the timeout set with
 712                                 <varname>Timeout=</varname> in service
 713                                 units) as the job timeout has no
 714                                 effect on the unit itself, only on the
 715                                 job that might be pending for it. Or
 716                                 in other words: unit-specific timeouts
 717                                 are useful to abort unit state
 718                                 changes, and revert them. The job
 719                                 timeout set with this option however
 720                                 is useful to abort only the job
 721                                 waiting for the unit state to
 722                                 change.</para></listitem>
 723                         </varlistentry>
 724
 725                         <varlistentry>
 726                                 <term><varname>ConditionPathExists=</varname></term>
 727                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 728                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 729                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 730                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 731                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 732                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 733                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 734                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 735                                 <term><varname>ConditionVirtualization=</varname></term>
 736                                 <term><varname>ConditionSecurity=</varname></term>
 737                                 <term><varname>ConditionCapability=</varname></term>
 738                                 <term><varname>ConditionNull=</varname></term>
 739
 740                                 <listitem><para>Before starting a unit
 741                                 verify that the specified condition is
 742                                 true. With
 743                                 <varname>ConditionPathExists=</varname>
 744                                 a file existence condition can be
 745                                 checked before a unit is started. If
 746                                 the specified absolute path name does
 747                                 not exist, startup of a unit will not
 748                                 actually happen, however the unit is
 749                                 still useful for ordering purposes in
 750                                 this case. The condition is checked at
 751                                 the time the queued start job is to be
 752                                 executed. If the absolute path name
 753                                 passed to
 754                                 <varname>ConditionPathExists=</varname>
 755                                 is prefixed with an exclamation mark
 756                                 (!), the test is negated, and the unit
 757                                 is only started if the path does not
 758                                 exist.
 759                                 <varname>ConditionPathExistsGlob=</varname>
 760                                 works in a similar way, but checks for
 761                                 the existence of at least one file or
 762                                 directory matching the specified
 763                                 globbing
 764                                 pattern. <varname>ConditionPathIsDirectory=</varname>
 765                                 is similar to
 766                                 <varname>ConditionPathExists=</varname>
 767                                 but verifies whether a certain path
 768                                 exists and is a
 769                                 directory. <varname>ConditionPathIsSymbolicLink=</varname>
 770                                 is similar to
 771                                 <varname>ConditionPathExists=</varname>
 772                                 but verifies whether a certain path
 773                                 exists and is a symbolic
 774                                 link. <varname>ConditionPathIsMountPoint=</varname>
 775                                 is similar to
 776                                 <varname>ConditionPathExists=</varname>
 777                                 but verifies whether a certain path
 778                                 exists and is a mount
 779                                 point. <varname>ConditionPathIsReadWrite=</varname>
 780                                 is similar to
 781                                 <varname>ConditionPathExists=</varname>
 782                                 but verifies whether the underlying
 783                                 file system is read and writable
 784                                 (i.e. not mounted
 785                                 read-only). <varname>ConditionFileIsExecutable=</varname>
 786                                 is similar to
 787                                 <varname>ConditionPathExists=</varname>
 788                                 but verifies whether a certain path
 789                                 exists, is a regular file and marked
 790                                 executable.
 791                                 <varname>ConditionDirectoryNotEmpty=</varname>
 792                                 is similar to
 793                                 <varname>ConditionPathExists=</varname>
 794                                 but verifies whether a certain path
 795                                 exists and is a non-empty
 796                                 directory. Similarly
 797                                 <varname>ConditionKernelCommandLine=</varname>
 798                                 may be used to check whether a
 799                                 specific kernel command line option is
 800                                 set (or if prefixed with the
 801                                 exclamation mark unset). The argument
 802                                 must either be a single word, or an
 803                                 assignment (i.e. two words, separated
 804                                 by the equality sign). In the former
 805                                 case the kernel command line is
 806                                 searched for the word appearing as is,
 807                                 or as left hand side of an
 808                                 assignment. In the latter case the
 809                                 exact assignment is looked for with
 810                                 right and left hand side
 811                                 matching. <varname>ConditionVirtualization=</varname>
 812                                 may be used to check whether the
 813                                 system is executed in a virtualized
 814                                 environment and optionally test
 815                                 whether it is a specific
 816                                 implementation. Takes either boolean
 817                                 value to check if being executed in
 818                                 any virtualized environment, or one of
 819                                 <varname>vm</varname> and
 820                                 <varname>container</varname> to test
 821                                 against a specific type of
 822                                 virtualization solution, or one of
 823                                 <varname>qemu</varname>,
 824                                 <varname>kvm</varname>,
 825                                 <varname>vmware</varname>,
 826                                 <varname>microsoft</varname>,
 827                                 <varname>oracle</varname>,
 828                                 <varname>xen</varname>,
 829                                 <varname>bochs</varname>,
 830                                 <varname>chroot</varname>,
 831                                 <varname>openvz</varname>,
 832                                 <varname>lxc</varname>,
 833                                 <varname>lxc-libvirt</varname>,
 834                                 <varname>systemd-nspawn</varname> to
 835                                 test against a specific
 836                                 implementation. If multiple
 837                                 virtualization technologies are nested
 838                                 only the innermost is considered. The
 839                                 test may be negated by prepending an
 840                                 exclamation mark.
 841                                 <varname>ConditionSecurity=</varname>
 842                                 may be used to check whether the given
 843                                 security module is enabled on the
 844                                 system.  Currently the only recognized
 845                                 value is <varname>selinux</varname>.
 846                                 The test may be negated by prepending
 847                                 an exclamation
 848                                 mark. <varname>ConditionCapability=</varname>
 849                                 may be used to check whether the given
 850                                 capability exists in the capability
 851                                 bounding set of the service manager
 852                                 (i.e. this does not check whether
 853                                 capability is actually available in
 854                                 the permitted or effective sets, see
 855                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 856                                 for details). Pass a capability name
 857                                 such as <literal>CAP_MKNOD</literal>,
 858                                 possibly prefixed with an exclamation
 859                                 mark to negate the check. Finally,
 860                                 <varname>ConditionNull=</varname> may
 861                                 be used to add a constant condition
 862                                 check value to the unit. It takes a
 863                                 boolean argument. If set to
 864                                 <varname>false</varname> the condition
 865                                 will always fail, otherwise
 866                                 succeed. If multiple conditions are
 867                                 specified the unit will be executed if
 868                                 all of them apply (i.e. a logical AND
 869                                 is applied). Condition checks can be
 870                                 prefixed with a pipe symbol (|) in
 871                                 which case a condition becomes a
 872                                 triggering condition. If at least one
 873                                 triggering condition is defined for a
 874                                 unit then the unit will be executed if
 875                                 at least one of the triggering
 876                                 conditions apply and all of the
 877                                 non-triggering conditions. If you
 878                                 prefix an argument with the pipe
 879                                 symbol and an exclamation mark the
 880                                 pipe symbol must be passed first, the
 881                                 exclamation second. Except for
 882                                 <varname>ConditionPathIsSymbolicLink=</varname>,
 883                                 all path checks follow
 884                                 symlinks.</para></listitem>
 885                         </varlistentry>
 886
 887                         <varlistentry>
 888                                 <term><varname>SourcePath=</varname></term>
 889                                 <listitem><para>A path to a
 890                                 configuration file this unit has been
 891                                 generated from. This is primarily
 892                                 useful for implementation of generator
 893                                 tools that convert configuration from
 894                                 an external configuration file format
 895                                 into native unit files. Thus
 896                                 functionality should not be used in
 897                                 normal units.</para></listitem>
 898                         </varlistentry>
 899                 </variablelist>
 900
 901                 <para>Unit file may include a [Install] section, which
 902                 carries installation information for the unit. This
 903                 section is not interpreted by
 904                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 905                 during runtime. It is used exclusively by the
 906                 <command>enable</command> and
 907                 <command>disable</command> commands of the
 908                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 909                 tool during installation of a unit:</para>
 910
 911                 <variablelist>
 912                         <varlistentry>
 913                                 <term><varname>Alias=</varname></term>
 914
 915                                 <listitem><para>Additional names this
 916                                 unit shall be installed under. The
 917                                 names listed here must have the same
 918                                 suffix (i.e. type) as the unit file
 919                                 name. This option may be specified
 920                                 more than once, in which case all
 921                                 listed names are used. At installation
 922                                 time,
 923                                 <command>systemctl enable</command>
 924                                 will create symlinks from these names
 925                                 to the unit file name.</para></listitem>
 926                         </varlistentry>
 927
 928                         <varlistentry>
 929                                 <term><varname>WantedBy=</varname></term>
 930                                 <term><varname>RequiredBy=</varname></term>
 931
 932                                 <listitem><para>Installs a symlink in
 933                                 the <filename>.wants/</filename>
 934                                 resp. <filename>.requires/</filename>
 935                                 subdirectory for a unit. This has the
 936                                 effect that when the listed unit name
 937                                 is activated the unit listing it is
 938                                 activated
 939                                 too. <command>WantedBy=foo.service</command>
 940                                 in a service
 941                                 <filename>bar.service</filename> is
 942                                 mostly equivalent to
 943                                 <command>Alias=foo.service.wants/bar.service</command>
 944                                 in the same file.</para></listitem>
 945                         </varlistentry>
 946
 947                         <varlistentry>
 948                                 <term><varname>Also=</varname></term>
 949
 950                                 <listitem><para>Additional units to
 951                                 install when this unit is
 952                                 installed. If the user requests
 953                                 installation of a unit with this
 954                                 option configured,
 955                                 <command>systemctl enable</command>
 956                                 will automatically install units
 957                                 listed in this option as
 958                                 well.</para></listitem>
 959                         </varlistentry>
 960                 </variablelist>
 961
 962         </refsect1>
 963
 964         <refsect1>
 965                 <title>See Also</title>
 966                 <para>
 967                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 968                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 969                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 970                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 971                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 972                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 973                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 974                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 975                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 976                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 977                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 978                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 979                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 980                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 981                 </para>
 982         </refsect1>
 983
 984 </refentry>