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. For details see <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</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>%U</literal></entry>
 268                         <entry>User uid</entry>
 269                         <entry>This is the uid 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>%h</literal></entry>
 273                         <entry>User home directory</entry>
 274                         <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>
 275                       </row>
 276                       <row>
 277                         <entry><literal>%s</literal></entry>
 278                         <entry>User shell</entry>
 279                         <entry>This is the shell of the configured user of the unit, or (if none is set) the user running the systemd instance.</entry>
 280                       </row>
 281                       <row>
 282                         <entry><literal>%m</literal></entry>
 283                         <entry>Machine ID</entry>
 284                         <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>
 285                       </row>
 286                       <row>
 287                         <entry><literal>%b</literal></entry>
 288                         <entry>Boot ID</entry>
 289                         <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
 290                       </row>
 291                       <row>
 292                         <entry><literal>%H</literal></entry>
 293                         <entry>Host name</entry>
 294                         <entry>The host name of the running system.</entry>
 295                       </row>
 296                     </tbody>
 297                   </tgroup>
 298                 </table>
 299
 300                 <para>If a unit file is empty (i.e. has the file size
 301                 0) or is symlinked to <filename>/dev/null</filename>
 302                 its configuration will not be loaded and it appears
 303                 with a load state of <literal>masked</literal>, and
 304                 cannot be activated. Use this as an effective way to
 305                 fully disable a unit, making it impossible to start it
 306                 even manually.</para>
 307
 308                 <para>The unit file format is covered by the
 309                 <ulink
 310                 url="http://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
 311                 Stability Promise</ulink>.</para>
 312         </refsect1>
 313
 314         <refsect1>
 315                 <title>Options</title>
 316
 317                 <para>Unit file may include a [Unit] section, which
 318                 carries generic information about the unit that is not
 319                 dependent on the type of unit:</para>
 320
 321                 <variablelist>
 322
 323                         <varlistentry>
 324                                 <term><varname>Description=</varname></term>
 325                                 <listitem><para>A free-form string
 326                                 describing the unit. This is intended
 327                                 for use in UIs to show descriptive
 328                                 information along with the unit
 329                                 name.</para></listitem>
 330                         </varlistentry>
 331
 332                         <varlistentry>
 333                                 <term><varname>Documentation=</varname></term>
 334                                 <listitem><para>A space separated list
 335                                 of URIs referencing documentation for
 336                                 this unit or its
 337                                 configuration. Accepted are only URIs
 338                                 of the types
 339                                 <literal>http://</literal>,
 340                                 <literal>https://</literal>,
 341                                 <literal>file:</literal>,
 342                                 <literal>info:</literal>,
 343                                 <literal>man:</literal>. For more
 344                                 information about the syntax of these
 345                                 URIs see
 346                                 <citerefentry><refentrytitle>uri</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
 347                                 URIs should be listed in order of
 348                                 relevance, starting with the most
 349                                 relevant. It is a good idea to first
 350                                 reference documentation that explains
 351                                 what the unit's purpose is, followed
 352                                 by how it is configured, followed by
 353                                 any other related
 354                                 documentation.</para></listitem>
 355                         </varlistentry>
 356
 357                         <varlistentry>
 358                                 <term><varname>Requires=</varname></term>
 359
 360                                 <listitem><para>Configures requirement
 361                                 dependencies on other units. If this
 362                                 unit gets activated, the units listed
 363                                 here will be activated as well. If one
 364                                 of the other units gets deactivated or
 365                                 its activation fails, this unit will
 366                                 be deactivated. This option may be
 367                                 specified more than once, in which
 368                                 case requirement dependencies for all
 369                                 listed names are created. Note that
 370                                 requirement dependencies do not
 371                                 influence the order in which services
 372                                 are started or stopped. This has to be
 373                                 configured independently with the
 374                                 <varname>After=</varname> or
 375                                 <varname>Before=</varname> options. If
 376                                 a unit
 377                                 <filename>foo.service</filename>
 378                                 requires a unit
 379                                 <filename>bar.service</filename> as
 380                                 configured with
 381                                 <varname>Requires=</varname> and no
 382                                 ordering is configured with
 383                                 <varname>After=</varname> or
 384                                 <varname>Before=</varname>, then both
 385                                 units will be started simultaneously
 386                                 and without any delay between them if
 387                                 <filename>foo.service</filename> is
 388                                 activated. Often it is a better choice
 389                                 to use <varname>Wants=</varname>
 390                                 instead of
 391                                 <varname>Requires=</varname> in order
 392                                 to achieve a system that is more
 393                                 robust when dealing with failing
 394                                 services.</para>
 395
 396                                 <para>Note that dependencies of this
 397                                 type may also be configured outside of
 398                                 the unit configuration file by
 399                                 adding a symlink to a
 400                                 <filename>.requires/</filename> directory
 401                                 accompanying the unit file. For
 402                                 details see above.</para></listitem>
 403                         </varlistentry>
 404
 405                         <varlistentry>
 406                                 <term><varname>RequiresOverridable=</varname></term>
 407
 408                                 <listitem><para>Similar to
 409                                 <varname>Requires=</varname>.
 410                                 Dependencies listed in
 411                                 <varname>RequiresOverridable=</varname>
 412                                 which cannot be fulfilled or fail to
 413                                 start are ignored if the startup was
 414                                 explicitly requested by the user. If
 415                                 the start-up was pulled in indirectly
 416                                 by some dependency or automatic
 417                                 start-up of units that is not
 418                                 requested by the user this dependency
 419                                 must be fulfilled and otherwise the
 420                                 transaction fails. Hence, this option
 421                                 may be used to configure dependencies
 422                                 that are normally honored unless the
 423                                 user explicitly starts up the unit, in
 424                                 which case whether they failed or not
 425                                 is irrelevant.</para></listitem>
 426
 427                         </varlistentry>
 428                         <varlistentry>
 429                                 <term><varname>Requisite=</varname></term>
 430                                 <term><varname>RequisiteOverridable=</varname></term>
 431
 432                                 <listitem><para>Similar to
 433                                 <varname>Requires=</varname>
 434                                 and <varname>RequiresOverridable=</varname>, respectively. However,
 435                                 if a unit listed here is not started
 436                                 already it will not be started and the
 437                                 transaction fails
 438                                 immediately.</para></listitem>
 439                         </varlistentry>
 440
 441                         <varlistentry>
 442                                 <term><varname>Wants=</varname></term>
 443
 444                                 <listitem><para>A weaker version of
 445                                 <varname>Requires=</varname>. A unit
 446                                 listed in this option will be started
 447                                 if the configuring unit is. However,
 448                                 if the listed unit fails to start up
 449                                 or cannot be added to the transaction
 450                                 this has no impact on the validity of
 451                                 the transaction as a whole. This is
 452                                 the recommended way to hook start-up
 453                                 of one unit to the start-up of another
 454                                 unit.</para>
 455
 456                                 <para>Note that dependencies of this
 457                                 type may also be configured outside of
 458                                 the unit configuration file by
 459                                 adding a symlink to a
 460                                 <filename>.wants/</filename> directory
 461                                 accompanying the unit file. For
 462                                 details see above.</para></listitem>
 463                         </varlistentry>
 464
 465                         <varlistentry>
 466                                 <term><varname>BindsTo=</varname></term>
 467
 468                                 <listitem><para>Configures requirement
 469                                 dependencies, very similar in style to
 470                                 <varname>Requires=</varname>, however
 471                                 in addition to this behavior it also
 472                                 declares that this unit is stopped
 473                                 when any of the units listed suddenly
 474                                 disappears. Units can suddenly,
 475                                 unexpectedly disappear if a service
 476                                 terminates on its own choice, a device
 477                                 is unplugged or a mount point
 478                                 unmounted without involvement of
 479                                 systemd.</para></listitem>
 480                         </varlistentry>
 481
 482                         <varlistentry>
 483                                 <term><varname>PartOf=</varname></term>
 484
 485                                 <listitem><para>Configures dependencies
 486                                 similar to <varname>Requires=</varname>,
 487                                 but limited to stopping and restarting
 488                                 of units. When systemd stops or restarts
 489                                 the units listed here, the action is
 490                                 propagated to this unit.
 491                                 Note that this is a one way dependency -
 492                                 changes to this unit do not affect the
 493                                 listed units.
 494                                 </para></listitem>
 495                         </varlistentry>
 496
 497                         <varlistentry>
 498                                 <term><varname>Conflicts=</varname></term>
 499
 500                                 <listitem><para>Configures negative
 501                                 requirement dependencies. If a unit
 502                                 has a
 503                                 <varname>Conflicts=</varname> setting
 504                                 on another unit, starting the former
 505                                 will stop the latter and vice
 506                                 versa. Note that this setting is
 507                                 independent of and orthogonal to the
 508                                 <varname>After=</varname> and
 509                                 <varname>Before=</varname> ordering
 510                                 dependencies.</para>
 511
 512                                 <para>If a unit A that conflicts with
 513                                 a unit B is scheduled to be started at
 514                                 the same time as B, the transaction
 515                                 will either fail (in case both are
 516                                 required part of the transaction) or
 517                                 be modified to be fixed (in case one
 518                                 or both jobs are not a required part
 519                                 of the transaction). In the latter
 520                                 case the job that is not the required
 521                                 will be removed, or in case both are
 522                                 not required the unit that conflicts
 523                                 will be started and the unit that is
 524                                 conflicted is
 525                                 stopped.</para></listitem>
 526                         </varlistentry>
 527
 528                         <varlistentry>
 529                                 <term><varname>Before=</varname></term>
 530                                 <term><varname>After=</varname></term>
 531
 532                                 <listitem><para>Configures ordering
 533                                 dependencies between units. If a unit
 534                                 <filename>foo.service</filename>
 535                                 contains a setting
 536                                 <option>Before=bar.service</option>
 537                                 and both units are being started,
 538                                 <filename>bar.service</filename>'s
 539                                 start-up is delayed until
 540                                 <filename>foo.service</filename> is
 541                                 started up. Note that this setting is
 542                                 independent of and orthogonal to the
 543                                 requirement dependencies as configured
 544                                 by <varname>Requires=</varname>. It is
 545                                 a common pattern to include a unit
 546                                 name in both the
 547                                 <varname>After=</varname> and
 548                                 <varname>Requires=</varname> option in
 549                                 which case the unit listed will be
 550                                 started before the unit that is
 551                                 configured with these options. This
 552                                 option may be specified more than
 553                                 once, in which case ordering
 554                                 dependencies for all listed names are
 555                                 created. <varname>After=</varname> is
 556                                 the inverse of
 557                                 <varname>Before=</varname>, i.e. while
 558                                 <varname>After=</varname> ensures that
 559                                 the configured unit is started after
 560                                 the listed unit finished starting up,
 561                                 <varname>Before=</varname> ensures the
 562                                 opposite, i.e.  that the configured
 563                                 unit is fully started up before the
 564                                 listed unit is started. Note that when
 565                                 two units with an ordering dependency
 566                                 between them are shut down, the
 567                                 inverse of the start-up order is
 568                                 applied. i.e. if a unit is configured
 569                                 with <varname>After=</varname> on
 570                                 another unit, the former is stopped
 571                                 before the latter if both are shut
 572                                 down. If one unit with an ordering
 573                                 dependency on another unit is shut
 574                                 down while the latter is started up,
 575                                 the shut down is ordered before the
 576                                 start-up regardless whether the
 577                                 ordering dependency is actually of
 578                                 type <varname>After=</varname> or
 579                                 <varname>Before=</varname>. If two
 580                                 units have no ordering dependencies
 581                                 between them they are shut down
 582                                 or started up simultaneously, and
 583                                 no ordering takes
 584                                 place. </para></listitem>
 585                         </varlistentry>
 586
 587                         <varlistentry>
 588                                 <term><varname>OnFailure=</varname></term>
 589
 590                                 <listitem><para>Lists one or more
 591                                 units that are activated when this
 592                                 unit enters the
 593                                 '<literal>failed</literal>'
 594                                 state.</para></listitem>
 595                         </varlistentry>
 596
 597                         <varlistentry>
 598                                 <term><varname>PropagatesReloadTo=</varname></term>
 599                                 <term><varname>ReloadPropagatedFrom=</varname></term>
 600
 601                                 <listitem><para>Lists one or more
 602                                 units where reload requests on the
 603                                 unit will be propagated to/on the
 604                                 other unit will be propagated
 605                                 from. Issuing a reload request on a
 606                                 unit will automatically also enqueue a
 607                                 reload request on all units that the
 608                                 reload request shall be propagated to
 609                                 via these two
 610                                 settings.</para></listitem>
 611                         </varlistentry>
 612
 613                         <varlistentry>
 614                                 <term><varname>RequiresMountsFor=</varname></term>
 615
 616                                 <listitem><para>Takes a space
 617                                 separated list of absolute paths. Automatically
 618                                 adds dependencies of type
 619                                 <varname>Requires=</varname> and
 620                                 <varname>After=</varname> for all
 621                                 mount units required to access the
 622                                 specified path.</para></listitem>
 623                         </varlistentry>
 624
 625                         <varlistentry>
 626                                 <term><varname>OnFailureIsolate=</varname></term>
 627
 628                                 <listitem><para>Takes a boolean
 629                                 argument. If <option>true</option> the
 630                                 unit listed in
 631                                 <varname>OnFailure=</varname> will be
 632                                 enqueued in isolation mode, i.e. all
 633                                 units that are not its dependency will
 634                                 be stopped. If this is set only a
 635                                 single unit may be listed in
 636                                 <varname>OnFailure=</varname>. Defaults
 637                                 to
 638                                 <option>false</option>.</para></listitem>
 639                         </varlistentry>
 640
 641                         <varlistentry>
 642                                 <term><varname>IgnoreOnIsolate=</varname></term>
 643
 644                                 <listitem><para>Takes a boolean
 645                                 argument. If <option>true</option>
 646                                 this unit will not be stopped when
 647                                 isolating another unit. Defaults to
 648                                 <option>false</option>.</para></listitem>
 649                         </varlistentry>
 650
 651                         <varlistentry>
 652                                 <term><varname>IgnoreOnSnapshot=</varname></term>
 653
 654                                 <listitem><para>Takes a boolean
 655                                 argument. If <option>true</option>
 656                                 this unit will not be included in
 657                                 snapshots. Defaults to
 658                                 <option>true</option> for device and
 659                                 snapshot units, <option>false</option>
 660                                 for the others.</para></listitem>
 661                         </varlistentry>
 662
 663                         <varlistentry>
 664                                 <term><varname>StopWhenUnneeded=</varname></term>
 665
 666                                 <listitem><para>Takes a boolean
 667                                 argument. If <option>true</option>
 668                                 this unit will be stopped when it is
 669                                 no longer used. Note that in order to
 670                                 minimize the work to be executed,
 671                                 systemd will not stop units by default
 672                                 unless they are conflicting with other
 673                                 units, or the user explicitly
 674                                 requested their shut down. If this
 675                                 option is set, a unit will be
 676                                 automatically cleaned up if no other
 677                                 active unit requires it. Defaults to
 678                                 <option>false</option>.</para></listitem>
 679                         </varlistentry>
 680
 681                         <varlistentry>
 682                                 <term><varname>RefuseManualStart=</varname></term>
 683                                 <term><varname>RefuseManualStop=</varname></term>
 684
 685                                 <listitem><para>Takes a boolean
 686                                 argument. If <option>true</option>
 687                                 this unit can only be activated
 688                                 or deactivated indirectly. In
 689                                 this case explicit start-up
 690                                 or termination requested by the
 691                                 user is denied, however if it is
 692                                 started or stopped as a
 693                                 dependency of another unit, start-up
 694                                 or termination will succeed. This
 695                                 is mostly a safety feature to ensure
 696                                 that the user does not accidentally
 697                                 activate units that are not intended
 698                                 to be activated explicitly, and not
 699                                 accidentally deactivate units that are
 700                                 not intended to be deactivated.
 701                                 These options default to
 702                                 <option>false</option>.</para></listitem>
 703                         </varlistentry>
 704
 705                         <varlistentry>
 706                                 <term><varname>AllowIsolate=</varname></term>
 707
 708                                 <listitem><para>Takes a boolean
 709                                 argument. If <option>true</option>
 710                                 this unit may be used with the
 711                                 <command>systemctl isolate</command>
 712                                 command. Otherwise this will be
 713                                 refused. It probably is a good idea to
 714                                 leave this disabled except for target
 715                                 units that shall be used similar to
 716                                 runlevels in SysV init systems, just
 717                                 as a precaution to avoid unusable
 718                                 system states. This option defaults to
 719                                 <option>false</option>.</para></listitem>
 720                         </varlistentry>
 721
 722                         <varlistentry>
 723                                 <term><varname>DefaultDependencies=</varname></term>
 724
 725                                 <listitem><para>Takes a boolean
 726                                 argument. If <option>true</option>
 727                                 (the default), a few default
 728                                 dependencies will implicitly be
 729                                 created for the unit. The actual
 730                                 dependencies created depend on the
 731                                 unit type. For example, for service
 732                                 units, these dependencies ensure that
 733                                 the service is started only after
 734                                 basic system initialization is
 735                                 completed and is properly terminated on
 736                                 system shutdown. See the respective
 737                                 man pages for details. Generally, only
 738                                 services involved with early boot or
 739                                 late shutdown should set this option
 740                                 to <option>false</option>. It is
 741                                 highly recommended to leave this
 742                                 option enabled for the majority of
 743                                 common units. If set to
 744                                 <option>false</option> this option
 745                                 does not disable all implicit
 746                                 dependencies, just non-essential
 747                                 ones.</para></listitem>
 748                         </varlistentry>
 749
 750                         <varlistentry>
 751                                 <term><varname>JobTimeoutSec=</varname></term>
 752
 753                                 <listitem><para>When clients are
 754                                 waiting for a job of this unit to
 755                                 complete, time out after the specified
 756                                 time. If this time limit is reached
 757                                 the job will be cancelled, the unit
 758                                 however will not change state or even
 759                                 enter the '<literal>failed</literal>'
 760                                 mode. This value defaults to 0 (job
 761                                 timeouts disabled), except for device
 762                                 units. NB: this timeout is independent
 763                                 from any unit-specific timeout (for
 764                                 example, the timeout set with
 765                                 <varname>Timeout=</varname> in service
 766                                 units) as the job timeout has no
 767                                 effect on the unit itself, only on the
 768                                 job that might be pending for it. Or
 769                                 in other words: unit-specific timeouts
 770                                 are useful to abort unit state
 771                                 changes, and revert them. The job
 772                                 timeout set with this option however
 773                                 is useful to abort only the job
 774                                 waiting for the unit state to
 775                                 change.</para></listitem>
 776                         </varlistentry>
 777
 778                         <varlistentry>
 779                                 <term><varname>ConditionPathExists=</varname></term>
 780                                 <term><varname>ConditionPathExistsGlob=</varname></term>
 781                                 <term><varname>ConditionPathIsDirectory=</varname></term>
 782                                 <term><varname>ConditionPathIsSymbolicLink=</varname></term>
 783                                 <term><varname>ConditionPathIsMountPoint=</varname></term>
 784                                 <term><varname>ConditionPathIsReadWrite=</varname></term>
 785                                 <term><varname>ConditionDirectoryNotEmpty=</varname></term>
 786                                 <term><varname>ConditionFileNotEmpty=</varname></term>
 787                                 <term><varname>ConditionFileIsExecutable=</varname></term>
 788                                 <term><varname>ConditionKernelCommandLine=</varname></term>
 789                                 <term><varname>ConditionVirtualization=</varname></term>
 790                                 <term><varname>ConditionSecurity=</varname></term>
 791                                 <term><varname>ConditionCapability=</varname></term>
 792                                 <term><varname>ConditionHost=</varname></term>
 793                                 <term><varname>ConditionNull=</varname></term>
 794
 795                                 <listitem><para>Before starting a unit
 796                                 verify that the specified condition is
 797                                 true. If it is not true the starting
 798                                 of the unit will be skipped, however
 799                                 all ordering dependencies of it are
 800                                 still respected. A failing condition
 801                                 will not result in the unit being
 802                                 moved into a failure state. The
 803                                 condition is checked at the time the
 804                                 queued start job is to be
 805                                 executed.</para>
 806
 807                                 <para>With
 808                                 <varname>ConditionPathExists=</varname>
 809                                 a file existence condition is
 810                                 checked before a unit is started. If
 811                                 the specified absolute path name does
 812                                 not exist the condition will
 813                                 fail. If the absolute path name passed
 814                                 to
 815                                 <varname>ConditionPathExists=</varname>
 816                                 is prefixed with an exclamation mark
 817                                 ('!'), the test is negated, and the unit
 818                                 is only started if the path does not
 819                                 exist.</para>
 820
 821                                 <para><varname>ConditionPathExistsGlob=</varname>
 822                                 is similar to
 823                                 <varname>ConditionPathExists=</varname>,
 824                                 but checks for the existence of at
 825                                 least one file or directory matching
 826                                 the specified globbing pattern.</para>
 827
 828                                 <para><varname>ConditionPathIsDirectory=</varname>
 829                                 is similar to
 830                                 <varname>ConditionPathExists=</varname>
 831                                 but verifies whether a certain path
 832                                 exists and is a
 833                                 directory.</para>
 834
 835                                 <para><varname>ConditionPathIsSymbolicLink=</varname>
 836                                 is similar to
 837                                 <varname>ConditionPathExists=</varname>
 838                                 but verifies whether a certain path
 839                                 exists and is a symbolic
 840                                 link.</para>
 841
 842                                 <para><varname>ConditionPathIsMountPoint=</varname>
 843                                 is similar to
 844                                 <varname>ConditionPathExists=</varname>
 845                                 but verifies whether a certain path
 846                                 exists and is a mount
 847                                 point.</para>
 848
 849                                 <para><varname>ConditionPathIsReadWrite=</varname>
 850                                 is similar to
 851                                 <varname>ConditionPathExists=</varname>
 852                                 but verifies whether the underlying
 853                                 file system is readable and writable
 854                                 (i.e. not mounted
 855                                 read-only).</para>
 856
 857                                 <para><varname>ConditionDirectoryNotEmpty=</varname>
 858                                 is similar to
 859                                 <varname>ConditionPathExists=</varname>
 860                                 but verifies whether a certain path
 861                                 exists and is a non-empty
 862                                 directory.</para>
 863
 864                                 <para><varname>ConditionFileNotEmpty=</varname>
 865                                 is similar to
 866                                 <varname>ConditionPathExists=</varname>
 867                                 but verifies whether a certain path
 868                                 exists and refers to a regular file
 869                                 with a non-zero size.</para>
 870
 871                                 <para><varname>ConditionFileIsExecutable=</varname>
 872                                 is similar to
 873                                 <varname>ConditionPathExists=</varname>
 874                                 but verifies whether a certain path
 875                                 exists, is a regular file and marked
 876                                 executable.</para>
 877
 878                                 <para>Similar,
 879                                 <varname>ConditionKernelCommandLine=</varname>
 880                                 may be used to check whether a
 881                                 specific kernel command line option is
 882                                 set (or if prefixed with the
 883                                 exclamation mark unset). The argument
 884                                 must either be a single word, or an
 885                                 assignment (i.e. two words, separated
 886                                 '='). In the former
 887                                 case the kernel command line is
 888                                 searched for the word appearing as is,
 889                                 or as left hand side of an
 890                                 assignment. In the latter case the
 891                                 exact assignment is looked for with
 892                                 right and left hand side
 893                                 matching.</para>
 894
 895                                 <para><varname>ConditionVirtualization=</varname>
 896                                 may be used to check whether the
 897                                 system is executed in a virtualized
 898                                 environment and optionally test
 899                                 whether it is a specific
 900                                 implementation. Takes either boolean
 901                                 value to check if being executed in
 902                                 any virtualized environment, or one of
 903                                 <varname>vm</varname> and
 904                                 <varname>container</varname> to test
 905                                 against a generic type of
 906                                 virtualization solution, or one of
 907                                 <varname>qemu</varname>,
 908                                 <varname>kvm</varname>,
 909                                 <varname>vmware</varname>,
 910                                 <varname>microsoft</varname>,
 911                                 <varname>oracle</varname>,
 912                                 <varname>xen</varname>,
 913                                 <varname>bochs</varname>,
 914                                 <varname>chroot</varname>,
 915                                 <varname>openvz</varname>,
 916                                 <varname>lxc</varname>,
 917                                 <varname>lxc-libvirt</varname>,
 918                                 <varname>systemd-nspawn</varname> to
 919                                 test against a specific
 920                                 implementation. If multiple
 921                                 virtualization technologies are nested
 922                                 only the innermost is considered. The
 923                                 test may be negated by prepending an
 924                                 exclamation mark.</para>
 925
 926                                 <para><varname>ConditionSecurity=</varname>
 927                                 may be used to check whether the given
 928                                 security module is enabled on the
 929                                 system.  Currently the only recognized
 930                                 value is <varname>selinux</varname>.
 931                                 The test may be negated by prepending
 932                                 an exclamation
 933                                 mark.</para>
 934
 935                                 <para><varname>ConditionCapability=</varname>
 936                                 may be used to check whether the given
 937                                 capability exists in the capability
 938                                 bounding set of the service manager
 939                                 (i.e. this does not check whether
 940                                 capability is actually available in
 941                                 the permitted or effective sets, see
 942                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 943                                 for details). Pass a capability name
 944                                 such as <literal>CAP_MKNOD</literal>,
 945                                 possibly prefixed with an exclamation
 946                                 mark to negate the check.</para>
 947
 948                                 <para><varname>ConditionHost=</varname>
 949                                 may be used to match against the
 950                                 host name or machine ID of the
 951                                 host. This either takes a host name
 952                                 string (optionally with shell style
 953                                 globs) which is tested against the
 954                                 locally set host name as returned by
 955                                 <citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 956                                 or a machine ID formatted as string
 957                                 (see
 958                                 <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
 959                                 The test may be negated by prepending
 960                                 an exclamation mark.</para>
 961
 962                                 <para>Finally,
 963                                 <varname>ConditionNull=</varname> may
 964                                 be used to add a constant condition
 965                                 check value to the unit. It takes a
 966                                 boolean argument. If set to
 967                                 <varname>false</varname> the condition
 968                                 will always fail, otherwise
 969                                 succeed.</para>
 970
 971                                 <para>If multiple conditions are
 972                                 specified the unit will be executed if
 973                                 all of them apply (i.e. a logical AND
 974                                 is applied). Condition checks can be
 975                                 prefixed with a pipe symbol (|) in
 976                                 which case a condition becomes a
 977                                 triggering condition. If at least one
 978                                 triggering condition is defined for a
 979                                 unit then the unit will be executed if
 980                                 at least one of the triggering
 981                                 conditions apply and all of the
 982                                 non-triggering conditions. If you
 983                                 prefix an argument with the pipe
 984                                 symbol and an exclamation mark the
 985                                 pipe symbol must be passed first, the
 986                                 exclamation second. Except for
 987                                 <varname>ConditionPathIsSymbolicLink=</varname>,
 988                                 all path checks follow
 989                                 symlinks.</para></listitem>
 990                         </varlistentry>
 991
 992                         <varlistentry>
 993                                 <term><varname>SourcePath=</varname></term>
 994                                 <listitem><para>A path to a
 995                                 configuration file this unit has been
 996                                 generated from. This is primarily
 997                                 useful for implementation of generator
 998                                 tools that convert configuration from
 999                                 an external configuration file format
1000                                 into native unit files. Thus
1001                                 functionality should not be used in
1002                                 normal units.</para></listitem>
1003                         </varlistentry>
1004                 </variablelist>
1005
1006                 <para>Unit file may include a [Install] section, which
1007                 carries installation information for the unit. This
1008                 section is not interpreted by
1009                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1010                 during runtime. It is used exclusively by the
1011                 <command>enable</command> and
1012                 <command>disable</command> commands of the
1013                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1014                 tool during installation of a unit:</para>
1015
1016                 <variablelist>
1017                         <varlistentry>
1018                                 <term><varname>Alias=</varname></term>
1019
1020                                 <listitem><para>Additional names this
1021                                 unit shall be installed under. The
1022                                 names listed here must have the same
1023                                 suffix (i.e. type) as the unit file
1024                                 name. This option may be specified
1025                                 more than once, in which case all
1026                                 listed names are used. At installation
1027                                 time,
1028                                 <command>systemctl enable</command>
1029                                 will create symlinks from these names
1030                                 to the unit file name.</para></listitem>
1031                         </varlistentry>
1032
1033                         <varlistentry>
1034                                 <term><varname>WantedBy=</varname></term>
1035                                 <term><varname>RequiredBy=</varname></term>
1036
1037                                 <listitem><para>Installs a symlink in
1038                                 the <filename>.wants/</filename>
1039                                 or <filename>.requires/</filename>
1040                                 subdirectory for a unit, respectively. This has the
1041                                 effect that when the listed unit name
1042                                 is activated the unit listing it is
1043                                 activated
1044                                 too. <command>WantedBy=foo.service</command>
1045                                 in a service
1046                                 <filename>bar.service</filename> is
1047                                 mostly equivalent to
1048                                 <command>Alias=foo.service.wants/bar.service</command>
1049                                 in the same file.</para></listitem>
1050                         </varlistentry>
1051
1052                         <varlistentry>
1053                                 <term><varname>Also=</varname></term>
1054
1055                                 <listitem><para>Additional units to
1056                                 install when this unit is
1057                                 installed. If the user requests
1058                                 installation of a unit with this
1059                                 option configured,
1060                                 <command>systemctl enable</command>
1061                                 will automatically install units
1062                                 listed in this option as
1063                                 well.</para></listitem>
1064                         </varlistentry>
1065                 </variablelist>
1066
1067         </refsect1>
1068
1069         <refsect1>
1070                 <title>See Also</title>
1071                 <para>
1072                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1073                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1074                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1075                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1076                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1077                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1078                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1079                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1080                         <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1081                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1082                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1083                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1084                         <citerefentry><refentrytitle>systemd.snapshot</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1085                         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1086                         <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1087                 </para>
1088         </refsect1>
1089
1090 </refentry>