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