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 page lists the common configuration
  79                 options of all the unit types. These options need to
  80                 be configured in the [Unit] or [Install]
  81                 sections 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                       <row>
 277                         <entry><literal>%m</literal></entry>
 278                         <entry>Machine ID</entry>
 279                         <entry>The machine ID of the running system, formatted as string. See <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information.</entry>
 280                       </row>
 281                       <row>
 282                         <entry><literal>%b</literal></entry>
 283                         <entry>Boot ID</entry>
 284                         <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
 285                       </row>
 286                       <row>
 287                         <entry><literal>%H</literal></entry>
 288                         <entry>Host name</entry>
 289                         <entry>The host name of the running system.</entry>
 290                       </row>
 291                     </tbody>
 292                   </tgroup>
 293                 </table>
 294
 295                 <para>If a unit file is empty (i.e. has the file size
 296                 0) or is symlinked to <filename>/dev/null</filename>
 297                 its configuration will not be loaded and it appears
 298                 with a load state of <literal>masked</literal>, and
 299                 cannot be activated. Use this as an effective way to
 300                 fully disable a unit, making it impossible to start it
 301                 even manually.</para>
 302
 303                 <para>The unit file format is covered by the
 304                 <ulink
 305                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 306                 Stability Promise</ulink>.</para>
 307         </refsect1>
 308
 309         <refsect1>
 310                 <title>Options</title>
 311
 312                 <para>Unit file may include a [Unit] section, which
 313                 carries generic information about the unit that is not
 314                 dependent on the type of unit:</para>
 315
 316                 <variablelist>
 317
 318                         <varlistentry>
 319                                 <term><varname>Description=</varname></term>
 320                                 <listitem><para>A free-form string
 321                                 describing the unit. This is intended
 322                                 for use in UIs to show descriptive
 323                                 information along with the unit
 324                                 name.</para></listitem>
 325                         </varlistentry>
 326
 327                         <varlistentry>
 328                                 <term><varname>Documentation=</varname></term>
 329                                 <listitem><para>A space separated list
 330                                 of URIs referencing documentation for
 331                                 this unit or its
 332                                 configuration. Accepted are only URIs
 333                                 of the types
 334                                 <literal>http://</literal>,
 335                                 <literal>https://</literal>,
 336                                 <literal>file:</literal>,
 337                                 <literal>info:</literal>,
 338                                 <literal>man:</literal>. For more
 339                                 information about the syntax of these
 340                                 URIs see
 341                                 <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
 342                                 URIs should be listed in order of
 343                                 relevance, starting with the most
 344                                 relevant. It is a good idea to first
 345                                 reference documentation that explains
 346                                 what the unit's purpose is, followed
 347                                 by how it is configured, followed by
 348                                 any other related
 349                                 documentation.</para></listitem>
 350                         </varlistentry>
 351
 352                         <varlistentry>
 353                                 <term><varname>Requires=</varname></term>
 354
 355                                 <listitem><para>Configures requirement
 356                                 dependencies on other units. If this
 357                                 unit gets activated, the units listed
 358                                 here will be activated as well. If one
 359                                 of the other units gets deactivated or
 360                                 its activation fails, this unit will
 361                                 be deactivated. This option may be
 362                                 specified more than once, in which
 363                                 case requirement dependencies for all
 364                                 listed names are created. Note that
 365                                 requirement dependencies do not
 366                                 influence the order in which services
 367                                 are started or stopped. This has to be
 368                                 configured independently with the
 369                                 <varname>After=</varname> or
 370                                 <varname>Before=</varname> options. If
 371                                 a unit
 372                                 <filename>foo.service</filename>
 373                                 requires a unit
 374                                 <filename>bar.service</filename> as
 375                                 configured with
 376                                 <varname>Requires=</varname> and no
 377                                 ordering is configured with
 378                                 <varname>After=</varname> or
 379                                 <varname>Before=</varname>, then both
 380                                 units will be started simultaneously
 381                                 and without any delay between them if
 382                                 <filename>foo.service</filename> is
 383                                 activated. Often it is a better choice
 384                                 to use <varname>Wants=</varname>
 385                                 instead of
 386                                 <varname>Requires=</varname> in order
 387                                 to achieve a system that is more
 388                                 robust when dealing with failing
 389                                 services.</para>
 390
 391                                 <para>Note that dependencies of this
 392                                 type may also be configured outside of
 393                                 the unit configuration file by
 394                                 adding a symlink to a
 395                                 <filename>.requires/</filename> directory
 396                                 accompanying the unit file. For
 397                                 details see above.</para></listitem>
 398                         </varlistentry>
 399
 400                         <varlistentry>
 401                                 <term><varname>RequiresOverridable=</varname></term>
 402
 403                                 <listitem><para>Similar to
 404                                 <varname>Requires=</varname>.
 405                                 Dependencies listed in
 406                                 <varname>RequiresOverridable=</varname>
 407                                 which cannot be fulfilled or fail to
 408                                 start are ignored if the startup was
 409                                 explicitly requested by the user. If
 410                                 the start-up was pulled in indirectly
 411                                 by some dependency or automatic
 412                                 start-up of units that is not
 413                                 requested by the user this dependency
 414                                 must be fulfilled and otherwise the
 415                                 transaction fails. Hence, this option
 416                                 may be used to configure dependencies
 417                                 that are normally honored unless the
 418                                 user explicitly starts up the unit, in
 419                                 which case whether they failed or not
 420                                 is irrelevant.</para></listitem>
 421
 422                         </varlistentry>
 423                         <varlistentry>
 424                                 <term><varname>Requisite=</varname></term>
 425                                 <term><varname>RequisiteOverridable=</varname></term>
 426
 427                                 <listitem><para>Similar to
 428                                 <varname>Requires=</varname>
 429                                 and <varname>RequiresOverridable=</varname>, respectively. However,
 430                                 if a unit listed here is not started
 431                                 already it will not be started and the
 432                                 transaction fails
 433                                 immediately.</para></listitem>
 434                         </varlistentry>
 435
 436                         <varlistentry>
 437                                 <term><varname>Wants=</varname></term>
 438
 439                                 <listitem><para>A weaker version of
 440                                 <varname>Requires=</varname>. A unit
 441                                 listed in this option will be started
 442                                 if the configuring unit is. However,
 443                                 if the listed unit fails to start up
 444                                 or cannot be added to the transaction
 445                                 this has no impact on the validity of
 446                                 the transaction as a whole. This is
 447                                 the recommended way to hook start-up
 448                                 of one unit to the start-up of another
 449                                 unit.</para>
 450
 451                                 <para>Note that dependencies of this
 452                                 type may also be configured outside of
 453                                 the unit configuration file by
 454                                 adding a symlink to a
 455                                 <filename>.wants/</filename> directory
 456                                 accompanying the unit file. For
 457                                 details see above.</para></listitem>
 458                         </varlistentry>
 459
 460                         <varlistentry>
 461                                 <term><varname>BindsTo=</varname></term>
 462
 463                                 <listitem><para>Configures requirement
 464                                 dependencies, very similar in style to
 465                                 <varname>Requires=</varname>, however
 466                                 in addition to this behavior it also
 467                                 declares that this unit is stopped
 468                                 when any of the units listed suddenly
 469                                 disappears. Units can suddenly,
 470                                 unexpectedly disappear if a service
 471                                 terminates on its own choice, a device
 472                                 is unplugged or a mount point
 473                                 unmounted without involvement of
 474                                 systemd.</para></listitem>
 475                         </varlistentry>
 476
 477                         <varlistentry>
 478                                 <term><varname>PartOf=</varname></term>
 479
 480                                 <listitem><para>Configures dependencies
 481                                 similar to <varname>Requires=</varname>,
 482                                 but limited to stopping and restarting
 483                                 of units. When systemd stops or restarts
 484                                 the units listed here, the action is
 485                                 propagated to this unit.
 486                                 Note that this is a one way dependency -
 487                                 changes to this unit do not affect the
 488                                 listed units.
 489                                 </para></listitem>
 490                         </varlistentry>
 491
 492                         <varlistentry>
 493                                 <term><varname>Conflicts=</varname></term>
 494
 495                                 <listitem><para>Configures negative
 496                                 requirement dependencies. If a unit
 497                                 has a
 498                                 <varname>Conflicts=</varname> setting
 499                                 on another unit, starting the former
 500                                 will stop the latter and vice
 501                                 versa. Note that this setting is
 502                                 independent of and orthogonal to the
 503                                 <varname>After=</varname> and
 504                                 <varname>Before=</varname> ordering
 505                                 dependencies.</para>
 506
 507                                 <para>If a unit A that conflicts with
 508                                 a unit B is scheduled to be started at
 509                                 the same time as B, the transaction
 510                                 will either fail (in case both are
 511                                 required part of the transaction) or
 512                                 be modified to be fixed (in case one
 513                                 or both jobs are not a required part
 514                                 of the transaction). In the latter
 515                                 case the job that is not the required
 516                                 will be removed, or in case both are
 517                                 not required the unit that conflicts
 518                                 will be started and the unit that is
 519                                 conflicted is
 520                                 stopped.</para></listitem>
 521                         </varlistentry>
 522
 523                         <varlistentry>
 524                                 <term><varname>Before=</varname></term>
 525                                 <term><varname>After=</varname></term>
 526
 527                                 <listitem><para>Configures ordering
 528                                 dependencies between units. If a unit
 529                                 <filename>foo.service</filename>
 530                                 contains a setting
 531                                 <option>Before=bar.service</option>
 532                                 and both units are being started,
 533                                 <filename>bar.service</filename>'s
 534                                 start-up is delayed until
 535                                 <filename>foo.service</filename> is
 536                                 started up. Note that this setting is
 537                                 independent of and orthogonal to the
 538                                 requirement dependencies as configured
 539                                 by <varname>Requires=</varname>. It is
 540                                 a common pattern to include a unit
 541                                 name in both the
 542                                 <varname>After=</varname> and
 543                                 <varname>Requires=</varname> option in
 544                                 which case the unit listed will be
 545                                 started before the unit that is
 546                                 configured with these options. This
 547                                 option may be specified more than
 548                                 once, in which case ordering
 549                                 dependencies for all listed names are
 550                                 created. <varname>After=</varname> is
 551                                 the inverse of
 552                                 <varname>Before=</varname>, i.e. while
 553                                 <varname>After=</varname> ensures that
 554                                 the configured unit is started after
 555                                 the listed unit finished starting up,
 556                                 <varname>Before=</varname> ensures the
 557                                 opposite, i.e.  that the configured
 558                                 unit is fully started up before the
 559                                 listed unit is started. Note that when
 560                                 two units with an ordering dependency
 561                                 between them are shut down, the
 562                                 inverse of the start-up order is
 563                                 applied. i.e. if a unit is configured
 564                                 with <varname>After=</varname> on
 565                                 another unit, the former is stopped
 566                                 before the latter if both are shut
 567                                 down. If one unit with an ordering
 568                                 dependency on another unit is shut
 569                                 down while the latter is started up,
 570                                 the shut down is ordered before the
 571                                 start-up regardless whether the
 572                                 ordering dependency is actually of
 573                                 type <varname>After=</varname> or
 574                                 <varname>Before=</varname>. If two
 575                                 units have no ordering dependencies
 576                                 between them they are shut down
 577                                 or started up simultaneously, and
 578                                 no ordering takes
 579                                 place. </para></listitem>
 580                         </varlistentry>
 581
 582                         <varlistentry>
 583                                 <term><varname>OnFailure=</varname></term>
 584
 585                                 <listitem><para>Lists one or more
 586                                 units that are activated when this
 587                                 unit enters the
 588                                 '<literal>failed</literal>'
 589                                 state.</para></listitem>
 590                         </varlistentry>
 591
 592                         <varlistentry>
 593                                 <term><varname>PropagatesReloadTo=</varname></term>
 594                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 595
 596                                 <listitem><para>Lists one or more
 597                                 units where reload requests on the
 598                                 unit will be propagated to/on the
 599                                 other unit will be propagated
 600                                 from. Issuing a reload request on a
 601                                 unit will automatically also enqueue a
 602                                 reload request on all units that the
 603                                 reload request shall be propagated to
 604                                 via these two
 605                                 settings.</para></listitem>
 606                         </varlistentry>
 607
 608                         <varlistentry>
 609                                 <term><varname>RequiresMountsFor=</varname></term>
 610
 611                                 <listitem><para>Takes a space
 612                                 separated list of absolute paths. Automatically
 613                                 adds dependencies of type
 614                                 <varname>Requires=</varname> and
 615                                 <varname>After=</varname> for all
 616                                 mount units required to access the
 617                                 specified path.</para></listitem>
 618                         </varlistentry>
 619
 620                         <varlistentry>
 621                                 <term><varname>OnFailureIsolate=</varname></term>
 622
 623                                 <listitem><para>Takes a boolean
 624                                 argument. If <option>true</option> the
 625                                 unit listed in
 626                                 <varname>OnFailure=</varname> will be
 627                                 enqueued in isolation mode, i.e. all
 628                                 units that are not its dependency will
 629                                 be stopped. If this is set only a
 630                                 single unit may be listed in
 631                                 <varname>OnFailure=</varname>. Defaults
 632                                 to
 633                                 <option>false</option>.</para></listitem>
 634                         </varlistentry>
 635
 636                         <varlistentry>
 637                                 <term><varname>IgnoreOnIsolate=</varname></term>
 638
 639                                 <listitem><para>Takes a boolean
 640                                 argument. If <option>true</option>
 641                                 this unit will not be stopped when
 642                                 isolating another unit. Defaults to
 643                                 <option>false</option>.</para></listitem>
 644                         </varlistentry>
 645
 646                         <varlistentry>
 647                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 648
 649                                 <listitem><para>Takes a boolean
 650                                 argument. If <option>true</option>
 651                                 this unit will not be included in
 652                                 snapshots. Defaults to
 653                                 <option>true</option> for device and
 654                                 snapshot units, <option>false</option>
 655                                 for the others.</para></listitem>
 656                         </varlistentry>
 657
 658                         <varlistentry>
 659                                 <term><varname>StopWhenUnneeded=</varname></term>
 660
 661                                 <listitem><para>Takes a boolean
 662                                 argument. If <option>true</option>
 663                                 this unit will be stopped when it is
 664                                 no longer used. Note that in order to
 665                                 minimize the work to be executed,
 666                                 systemd will not stop units by default
 667                                 unless they are conflicting with other
 668                                 units, or the user explicitly
 669                                 requested their shut down. If this
 670                                 option is set, a unit will be
 671                                 automatically cleaned up if no other
 672                                 active unit requires it. Defaults to
 673                                 <option>false</option>.</para></listitem>
 674                         </varlistentry>
 675
 676                         <varlistentry>
 677                                 <term><varname>RefuseManualStart=</varname></term>
 678                                 <term><varname>RefuseManualStop=</varname></term>
 679
 680                                 <listitem><para>Takes a boolean
 681                                 argument. If <option>true</option>
 682                                 this unit can only be activated
 683                                 or deactivated indirectly. In
 684                                 this case explicit start-up
 685                                 or termination requested by the
 686                                 user is denied, however if it is
 687                                 started or stopped as a
 688                                 dependency of another unit, start-up
 689                                 or termination will succeed. This
 690                                 is mostly a safety feature to ensure
 691                                 that the user does not accidentally
 692                                 activate units that are not intended
 693                                 to be activated explicitly, and not
 694                                 accidentally deactivate units that are
 695                                 not intended to be deactivated.
 696                                 These options default to
 697                                 <option>false</option>.</para></listitem>
 698                         </varlistentry>
 699
 700                         <varlistentry>
 701                                 <term><varname>AllowIsolate=</varname></term>
 702
 703                                 <listitem><para>Takes a boolean
 704                                 argument. If <option>true</option>
 705                                 this unit may be used with the
 706                                 <command>systemctl isolate</command>
 707                                 command. Otherwise this will be
 708                                 refused. It probably is a good idea to
 709                                 leave this disabled except for target
 710                                 units that shall be used similar to
 711                                 runlevels in SysV init systems, just
 712                                 as a precaution to avoid unusable
 713                                 system states. This option defaults to
 714                                 <option>false</option>.</para></listitem>
 715                         </varlistentry>
 716
 717                         <varlistentry>
 718                                 <term><varname>DefaultDependencies=</varname></term>
 719
 720                                 <listitem><para>Takes a boolean
 721                                 argument. If <option>true</option>
 722                                 (the default), a few default
 723                                 dependencies will implicitly be
 724                                 created for the unit. The actual
 725                                 dependencies created depend on the
 726                                 unit type. For example, for service
 727                                 units, these dependencies ensure that
 728                                 the service is started only after
 729                                 basic system initialization is
 730                                 completed and is properly terminated on
 731                                 system shutdown. See the respective
 732                                 man pages for details. Generally, only
 733                                 services involved with early boot or
 734                                 late shutdown should set this option
 735                                 to <option>false</option>. It is
 736                                 highly recommended to leave this
 737                                 option enabled for the majority of
 738                                 common units. If set to
 739                                 <option>false</option> this option
 740                                 does not disable all implicit
 741                                 dependencies, just non-essential
 742                                 ones.</para></listitem>
 743                         </varlistentry>
 744
 745                         <varlistentry>
 746                                 <term><varname>JobTimeoutSec=</varname></term>
 747
 748                                 <listitem><para>When clients are
 749                                 waiting for a job of this unit to
 750                                 complete, time out after the specified
 751                                 time. If this time limit is reached
 752                                 the job will be cancelled, the unit
 753                                 however will not change state or even
 754                                 enter the '<literal>failed</literal>'
 755                                 mode. This value defaults to 0 (job
 756                                 timeouts disabled), except for device
 757                                 units. NB: this timeout is independent
 758                                 from any unit-specific timeout (for
 759                                 example, the timeout set with
 760                                 <varname>Timeout=</varname> in service
 761                                 units) as the job timeout has no
 762                                 effect on the unit itself, only on the
 763                                 job that might be pending for it. Or
 764                                 in other words: unit-specific timeouts
 765                                 are useful to abort unit state
 766                                 changes, and revert them. The job
 767                                 timeout set with this option however
 768                                 is useful to abort only the job
 769                                 waiting for the unit state to
 770                                 change.</para></listitem>
 771                         </varlistentry>
 772
 773                         <varlistentry>
 774                                 <term><varname>ConditionPathExists=</varname></term>
 775                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 776                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 777                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 778                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 779                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 780                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 781                                 <term><varname>ConditionFileNotEmpty=</varname></term>
 782                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 783                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 784                                 <term><varname>ConditionVirtualization=</varname></term>
 785                                 <term><varname>ConditionSecurity=</varname></term>
 786                                 <term><varname>ConditionCapability=</varname></term>
 787                                 <term><varname>ConditionHost=</varname></term>
 788                                 <term><varname>ConditionNull=</varname></term>
 789
 790                                 <listitem><para>Before starting a unit
 791                                 verify that the specified condition is
 792                                 true. If it is not true the starting
 793                                 of the unit will be skipped, however
 794                                 all ordering dependencies of it are
 795                                 still respected. A failing condition
 796                                 will not result in the unit being
 797                                 moved into a failure state. The
 798                                 condition is checked at the time the
 799                                 queued start job is to be
 800                                 executed.</para>
 801
 802                                 <para>With
 803                                 <varname>ConditionPathExists=</varname>
 804                                 a file existence condition is
 805                                 checked before a unit is started. If
 806                                 the specified absolute path name does
 807                                 not exist the condition will
 808                                 fail. If the absolute path name passed
 809                                 to
 810                                 <varname>ConditionPathExists=</varname>
 811                                 is prefixed with an exclamation mark
 812                                 ('!'), the test is negated, and the unit
 813                                 is only started if the path does not
 814                                 exist.</para>
 815
 816                                 <para><varname>ConditionPathExistsGlob=</varname>
 817                                 is similar to
 818                                 <varname>ConditionPathExists=</varname>,
 819                                 but checks for the existence of at
 820                                 least one file or directory matching
 821                                 the specified globbing pattern.</para>
 822
 823                                 <para><varname>ConditionPathIsDirectory=</varname>
 824                                 is similar to
 825                                 <varname>ConditionPathExists=</varname>
 826                                 but verifies whether a certain path
 827                                 exists and is a
 828                                 directory.</para>
 829
 830                                 <para><varname>ConditionPathIsSymbolicLink=</varname>
 831                                 is similar to
 832                                 <varname>ConditionPathExists=</varname>
 833                                 but verifies whether a certain path
 834                                 exists and is a symbolic
 835                                 link.</para>
 836
 837                                 <para><varname>ConditionPathIsMountPoint=</varname>
 838                                 is similar to
 839                                 <varname>ConditionPathExists=</varname>
 840                                 but verifies whether a certain path
 841                                 exists and is a mount
 842                                 point.</para>
 843
 844                                 <para><varname>ConditionPathIsReadWrite=</varname>
 845                                 is similar to
 846                                 <varname>ConditionPathExists=</varname>
 847                                 but verifies whether the underlying
 848                                 file system is readable and writable
 849                                 (i.e. not mounted
 850                                 read-only).</para>
 851
 852                                 <para><varname>ConditionDirectoryNotEmpty=</varname>
 853                                 is similar to
 854                                 <varname>ConditionPathExists=</varname>
 855                                 but verifies whether a certain path
 856                                 exists and is a non-empty
 857                                 directory.</para>
 858
 859                                 <para><varname>ConditionFileNotEmpty=</varname>
 860                                 is similar to
 861                                 <varname>ConditionPathExists=</varname>
 862                                 but verifies whether a certain path
 863                                 exists and refers to a regular file
 864                                 with a non-zero size.</para>
 865
 866                                 <para><varname>ConditionFileIsExecutable=</varname>
 867                                 is similar to
 868                                 <varname>ConditionPathExists=</varname>
 869                                 but verifies whether a certain path
 870                                 exists, is a regular file and marked
 871                                 executable.</para>
 872
 873                                 <para>Similar,
 874                                 <varname>ConditionKernelCommandLine=</varname>
 875                                 may be used to check whether a
 876                                 specific kernel command line option is
 877                                 set (or if prefixed with the
 878                                 exclamation mark unset). The argument
 879                                 must either be a single word, or an
 880                                 assignment (i.e. two words, separated
 881                                 '='). In the former
 882                                 case the kernel command line is
 883                                 searched for the word appearing as is,
 884                                 or as left hand side of an
 885                                 assignment. In the latter case the
 886                                 exact assignment is looked for with
 887                                 right and left hand side
 888                                 matching.</para>
 889
 890                                 <para><varname>ConditionVirtualization=</varname>
 891                                 may be used to check whether the
 892                                 system is executed in a virtualized
 893                                 environment and optionally test
 894                                 whether it is a specific
 895                                 implementation. Takes either boolean
 896                                 value to check if being executed in
 897                                 any virtualized environment, or one of
 898                                 <varname>vm</varname> and
 899                                 <varname>container</varname> to test
 900                                 against a generic type of
 901                                 virtualization solution, or one of
 902                                 <varname>qemu</varname>,
 903                                 <varname>kvm</varname>,
 904                                 <varname>vmware</varname>,
 905                                 <varname>microsoft</varname>,
 906                                 <varname>oracle</varname>,
 907                                 <varname>xen</varname>,
 908                                 <varname>bochs</varname>,
 909                                 <varname>chroot</varname>,
 910                                 <varname>openvz</varname>,
 911                                 <varname>lxc</varname>,
 912                                 <varname>lxc-libvirt</varname>,
 913                                 <varname>systemd-nspawn</varname> to
 914                                 test against a specific
 915                                 implementation. If multiple
 916                                 virtualization technologies are nested
 917                                 only the innermost is considered. The
 918                                 test may be negated by prepending an
 919                                 exclamation mark.</para>
 920
 921                                 <para><varname>ConditionSecurity=</varname>
 922                                 may be used to check whether the given
 923                                 security module is enabled on the
 924                                 system.  Currently the only recognized
 925                                 value is <varname>selinux</varname>.
 926                                 The test may be negated by prepending
 927                                 an exclamation
 928                                 mark.</para>
 929
 930                                 <para><varname>ConditionCapability=</varname>
 931                                 may be used to check whether the given
 932                                 capability exists in the capability
 933                                 bounding set of the service manager
 934                                 (i.e. this does not check whether
 935                                 capability is actually available in
 936                                 the permitted or effective sets, see
 937                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 938                                 for details). Pass a capability name
 939                                 such as <literal>CAP_MKNOD</literal>,
 940                                 possibly prefixed with an exclamation
 941                                 mark to negate the check.</para>
 942
 943                                 <para><varname>ConditionHost=</varname>
 944                                 may be used to match against the
 945                                 host name or machine ID of the
 946                                 host. This either takes a host name
 947                                 string (optionally with shell style
 948                                 globs) which is tested against the
 949                                 locally set host name as returned by
 950                                 <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 951                                 or a machine ID formatted as string
 952                                 (see
 953                                 <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
 954                                 The test may be negated by prepending
 955                                 an exclamation mark.</para>
 956
 957                                 <para>Finally,
 958                                 <varname>ConditionNull=</varname> may
 959                                 be used to add a constant condition
 960                                 check value to the unit. It takes a
 961                                 boolean argument. If set to
 962                                 <varname>false</varname> the condition
 963                                 will always fail, otherwise
 964                                 succeed.</para>
 965
 966                                 <para>If multiple conditions are
 967                                 specified the unit will be executed if
 968                                 all of them apply (i.e. a logical AND
 969                                 is applied). Condition checks can be
 970                                 prefixed with a pipe symbol (|) in
 971                                 which case a condition becomes a
 972                                 triggering condition. If at least one
 973                                 triggering condition is defined for a
 974                                 unit then the unit will be executed if
 975                                 at least one of the triggering
 976                                 conditions apply and all of the
 977                                 non-triggering conditions. If you
 978                                 prefix an argument with the pipe
 979                                 symbol and an exclamation mark the
 980                                 pipe symbol must be passed first, the
 981                                 exclamation second. Except for
 982                                 <varname>ConditionPathIsSymbolicLink=</varname>,
 983                                 all path checks follow
 984                                 symlinks.</para></listitem>
 985                         </varlistentry>
 986
 987                         <varlistentry>
 988                                 <term><varname>SourcePath=</varname></term>
 989                                 <listitem><para>A path to a
 990                                 configuration file this unit has been
 991                                 generated from. This is primarily
 992                                 useful for implementation of generator
 993                                 tools that convert configuration from
 994                                 an external configuration file format
 995                                 into native unit files. Thus
 996                                 functionality should not be used in
 997                                 normal units.</para></listitem>
 998                         </varlistentry>
 999                 </variablelist>
1000
1001                 <para>Unit file may include a [Install] section, which
1002                 carries installation information for the unit. This
1003                 section is not interpreted by
1004                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1005                 during runtime. It is used exclusively by the
1006                 <command>enable</command> and
1007                 <command>disable</command> commands of the
1008                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1009                 tool during installation of a unit:</para>
1010
1011                 <variablelist>
1012                         <varlistentry>
1013                                 <term><varname>Alias=</varname></term>
1014
1015                                 <listitem><para>Additional names this
1016                                 unit shall be installed under. The
1017                                 names listed here must have the same
1018                                 suffix (i.e. type) as the unit file
1019                                 name. This option may be specified
1020                                 more than once, in which case all
1021                                 listed names are used. At installation
1022                                 time,
1023                                 <command>systemctl enable</command>
1024                                 will create symlinks from these names
1025                                 to the unit file name.</para></listitem>
1026                         </varlistentry>
1027
1028                         <varlistentry>
1029                                 <term><varname>WantedBy=</varname></term>
1030                                 <term><varname>RequiredBy=</varname></term>
1031
1032                                 <listitem><para>Installs a symlink in
1033                                 the <filename>.wants/</filename>
1034                                 or <filename>.requires/</filename>
1035                                 subdirectory for a unit, respectively. This has the
1036                                 effect that when the listed unit name
1037                                 is activated the unit listing it is
1038                                 activated
1039                                 too. <command>WantedBy=foo.service</command>
1040                                 in a service
1041                                 <filename>bar.service</filename> is
1042                                 mostly equivalent to
1043                                 <command>Alias=foo.service.wants/bar.service</command>
1044                                 in the same file.</para></listitem>
1045                         </varlistentry>
1046
1047                         <varlistentry>
1048                                 <term><varname>Also=</varname></term>
1049
1050                                 <listitem><para>Additional units to
1051                                 install when this unit is
1052                                 installed. If the user requests
1053                                 installation of a unit with this
1054                                 option configured,
1055                                 <command>systemctl enable</command>
1056                                 will automatically install units
1057                                 listed in this option as
1058                                 well.</para></listitem>
1059                         </varlistentry>
1060                 </variablelist>
1061
1062         </refsect1>
1063
1064         <refsect1>
1065                 <title>See Also</title>
1066                 <para>
1067                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1068                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1069                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1070                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1071                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1072                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1073                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1074                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1075                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1076                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1077                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1078                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1079                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1080                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1081                 </para>
1082         </refsect1>
1083
1084 </refentry>