man/systemd.service.xml

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   7   This file is part of systemd.
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   9   Copyright 2010 Lennart Poettering
  10
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  24
  25 <refentry id="systemd.service">
  26         <refentryinfo>
  27                 <title>systemd.service</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.service</refentrytitle>
  42                 <manvolnum>5</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.service</refname>
  47                 <refpurpose>systemd service configuration files</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename>systemd.service</filename></para>
  52         </refsynopsisdiv>
  53
  54         <refsect1>
  55                 <title>Description</title>
  56
  57                 <para>A unit configuration file whose name ends in
  58                 <filename>.service</filename> encodes information
  59                 about a process controlled and supervised by
  60                 systemd.</para>
  61
  62                 <para>This man page lists the configuration options
  63                 specific to this unit type. See
  64                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  65                 for the common options of all unit configuration
  66                 files. The common configuration items are configured
  67                 in the generic <literal>[Unit]</literal> and
  68                 <literal>[Install]</literal> sections. The service
  69                 specific configuration options are configured in the
  70                 <literal>[Service]</literal> section.</para>
  71
  72                 <para>Additional options are listed in
  73                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  74                 which define the execution environment the commands
  75                 are executed in.</para>
  76
  77                 <para>Unless <varname>DefaultDependencies=</varname>
  78                 is set to <option>false</option>, service units will
  79                 implicitly have dependencies of type
  80                 <varname>Requires=</varname> and
  81                 <varname>After=</varname> on
  82                 <filename>basic.target</filename> as well as
  83                 dependencies of type <varname>Conflicts=</varname> and
  84                 <varname>Before=</varname> on
  85                 <filename>shutdown.target</filename>. These ensure
  86                 that normal service units pull in basic system
  87                 initialization, and are terminated cleanly prior to
  88                 system shutdown. Only services involved with early
  89                 boot or late system shutdown should disable this
  90                 option.</para>
  91
  92                 <para>If a service is requested under a certain name
  93                 but no unit configuration file is found, systemd looks
  94                 for a SysV init script by the same name (with the
  95                 <filename>.service</filename> suffix removed) and
  96                 dynamically creates a service unit from that
  97                 script. This is useful for compatibility with
  98                 SysV.</para>
  99         </refsect1>
 100
 101         <refsect1>
 102                 <title>Options</title>
 103
 104                 <para>Service files must include a
 105                 <literal>[Service]</literal> section, which carries
 106                 information about the service and the process it
 107                 supervises. A number of options that may be used in
 108                 this section are shared with other unit types. These
 109                 options are documented in
 110                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
 111                 options specific to the <literal>[Service]</literal>
 112                 section of service units are the following:</para>
 113
 114                 <variablelist>
 115                         <varlistentry>
 116                                 <term><varname>Type=</varname></term>
 117
 118                                 <listitem><para>Configures the process
 119                                 start-up type for this service
 120                                 unit. One of <option>simple</option>,
 121                                 <option>forking</option>,
 122                                 <option>oneshot</option>,
 123                                 <option>dbus</option>,
 124                                 <option>notify</option>.</para>
 125
 126                                 <para>If set to
 127                                 <option>simple</option> (the default
 128                                 value) it is expected that the process
 129                                 configured with
 130                                 <varname>ExecStart=</varname> is the
 131                                 main process of the service. In this
 132                                 mode, if the process offers
 133                                 functionality to other processes on
 134                                 the system its communication channels
 135                                 should be installed before the daemon
 136                                 is started up (e.g. sockets set up by
 137                                 systemd, via socket activation), as
 138                                 systemd will immediately proceed
 139                                 starting follow-up units.</para>
 140
 141                                 <para>If set to
 142                                 <option>forking</option> it is
 143                                 expected that the process configured
 144                                 with <varname>ExecStart=</varname>
 145                                 will call <function>fork()</function>
 146                                 as part of its start-up. The parent process is
 147                                 expected to exit when start-up is
 148                                 complete and all communication
 149                                 channels set up. The child continues
 150                                 to run as the main daemon
 151                                 process. This is the behaviour of
 152                                 traditional UNIX daemons. If this
 153                                 setting is used, it is recommended to
 154                                 also use the
 155                                 <varname>PIDFile=</varname> option, so
 156                                 that systemd can identify the main
 157                                 process of the daemon. systemd will
 158                                 proceed starting follow-up units as
 159                                 soon as the parent process
 160                                 exits.</para>
 161
 162                                 <para>Behaviour of
 163                                 <option>oneshot</option> is similar
 164                                 to <option>simple</option>, however
 165                                 it is expected that the process has to
 166                                 exit before systemd starts follow-up
 167                                 units. <varname>RemainAfterExit=</varname>
 168                                 is particularly useful for this type
 169                                 of service.</para>
 170
 171                                 <para>Behaviour of
 172                                 <option>dbus</option> is similar to
 173                                 <option>simple</option>, however it is
 174                                 expected that the daemon acquires a
 175                                 name on the D-Bus bus, as configured
 176                                 by
 177                                 <varname>BusName=</varname>. systemd
 178                                 will proceed starting follow-up units
 179                                 after the D-Bus bus name has been
 180                                 acquired. Service units with this
 181                                 option configured implicitly gain
 182                                 dependencies on the
 183                                 <filename>dbus.target</filename>
 184                                 unit.</para>
 185
 186                                 <para>Behaviour of
 187                                 <option>notify</option> is similar to
 188                                 <option>simple</option>, however it is
 189                                 expected that the daemon sends a
 190                                 notification message via
 191                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 192                                 or an equivalent call when it finished
 193                                 starting up. systemd will proceed
 194                                 starting follow-up units after this
 195                                 notification message has been sent. If
 196                                 this option is used
 197                                 <varname>NotifyAccess=</varname> (see
 198                                 below) should be set to open access to
 199                                 the notification socket provided by
 200                                 systemd. If
 201                                 <varname>NotifyAccess=</varname> is not
 202                                 set, it will implicitly be set to
 203                                 <option>main</option>.</para>
 204                                 </listitem>
 205                         </varlistentry>
 206
 207                         <varlistentry>
 208                                 <term><varname>RemainAfterExit=</varname></term>
 209
 210                                 <listitem><para>Takes a boolean value
 211                                 that specifies whether the service
 212                                 shall be considered active even when
 213                                 all its processes exited. Defaults to
 214                                 <option>no</option>.</para>
 215                                 </listitem>
 216                         </varlistentry>
 217
 218                         <varlistentry>
 219                                 <term><varname>PIDFile=</varname></term>
 220
 221                                 <listitem><para>Takes an absolute file
 222                                 name pointing to the PID file of this
 223                                 daemon. Use of this option is
 224                                 recommended for services where
 225                                 <varname>Type=</varname> is set to
 226                                 <option>forking</option>.</para>
 227                                 </listitem>
 228                         </varlistentry>
 229
 230                         <varlistentry>
 231                                 <term><varname>BusName=</varname></term>
 232
 233                                 <listitem><para>Takes a D-Bus bus
 234                                 name, where this service is reachable
 235                                 as. This option is mandatory for
 236                                 services where
 237                                 <varname>Type=</varname> is set to
 238                                 <option>dbus</option>, but its use
 239                                 is otherwise recommended as well if
 240                                 the process takes a name on the D-Bus
 241                                 bus.</para>
 242                                 </listitem>
 243                         </varlistentry>
 244
 245                         <varlistentry>
 246                                 <term><varname>ExecStart=</varname></term>
 247                                 <listitem><para>Takes a command line
 248                                 that is executed when this service
 249                                 shall be started up. The first token
 250                                 of the command line must be an
 251                                 absolute file name, then followed by
 252                                 arguments for the process. It is
 253                                 mandatory to set this option for all
 254                                 services. This option may not be
 255                                 specified more than once, except when
 256                                 <varname>Type=oneshot</varname> is
 257                                 used in which case more than one
 258                                 <varname>ExecStart=</varname> line is
 259                                 accepted which are then invoked one by
 260                                 one, sequentially in the order they
 261                                 appear in the unit file.</para>
 262
 263                                 <para>Optionally, if the absolute file
 264                                 name is prefixed with
 265                                 <literal>@</literal>, the second token
 266                                 will be passed as
 267                                 <literal>argv[0]</literal> to the
 268                                 executed process, followed by the
 269                                 further arguments specified. If the
 270                                 first token is prefixed with
 271                                 <literal>-</literal> an exit code of
 272                                 the command normally considered a
 273                                 failure (i.e. non-zero exit status or
 274                                 abormal exit due to signal) is ignored
 275                                 and considered success. If both
 276                                 <literal>-</literal> and
 277                                 <literal>@</literal> are used for the
 278                                 same command the former must preceed
 279                                 the latter. Unless
 280                                 <varname>Type=forking</varname> is
 281                                 set, the process started via this
 282                                 command line will be considered the
 283                                 main process of the daemon. The
 284                                 command line accepts % specifiers as
 285                                 described in
 286                                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. On
 287                                 top of that basic environment variable
 288                                 substitution is supported, where
 289                                 <literal>${FOO}</literal> is replaced
 290                                 by the string value of the environment
 291                                 variable of the same name. Also
 292                                 <literal>$FOO</literal> may appear as
 293                                 seperate word on the command line in
 294                                 which case the variable is replaced by
 295                                 its value split at
 296                                 whitespaces.</para></listitem>
 297                         </varlistentry>
 298
 299                         <varlistentry>
 300                                 <term><varname>ExecStartPre=</varname></term>
 301                                 <term><varname>ExecStartPost=</varname></term>
 302                                 <listitem><para>Additional commands
 303                                 that are executed before (resp. after)
 304                                 the command in
 305                                 <varname>ExecStart=</varname>. Multiple
 306                                 command lines may be concatenated in a
 307                                 single directive, by seperating them
 308                                 by semicolons (these semicolons must
 309                                 be passed as seperate words). In that
 310                                 case, the commands are executed one
 311                                 after the other,
 312                                 serially. Alternatively, these
 313                                 directives may be specified more than
 314                                 once whith the same effect. However,
 315                                 the latter syntax is not recommended
 316                                 for compatibility with parsers
 317                                 suitable for XDG
 318                                 <filename>.desktop</filename> files.
 319                                 Use of these settings is
 320                                 optional. Specifier and environment
 321                                 variable substitution is
 322                                 supported.</para></listitem>
 323                         </varlistentry>
 324
 325                         <varlistentry>
 326                                 <term><varname>ExecReload=</varname></term>
 327                                 <listitem><para>Commands to execute to
 328                                 trigger a configuration reload in the
 329                                 service. This argument takes multiple
 330                                 command lines, following the same
 331                                 scheme as pointed out for
 332                                 <varname>ExecStartPre=</varname>
 333                                 above. Use of this setting is
 334                                 optional. Specifier and environment
 335                                 variable substitution is supported
 336                                 here following the same scheme as for
 337                                 <varname>ExecStart=</varname>. One
 338                                 special environment variable is set:
 339                                 if known <literal>$MAINPID</literal> is
 340                                 set to the main process of the
 341                                 daemon, and may be used for command
 342                                 lines like the following:
 343                                 <command>/bin/kill -HUP
 344                                 $(MAINPID)</command>.</para></listitem>
 345                         </varlistentry>
 346
 347                         <varlistentry>
 348                                 <term><varname>ExecStop=</varname></term>
 349                                 <listitem><para>Commands to execute to
 350                                 stop the service started via
 351                                 <varname>ExecStart=</varname>. This
 352                                 argument takes multiple command lines,
 353                                 following the same scheme as pointed
 354                                 out for
 355                                 <varname>ExecStartPre=</varname>
 356                                 above. Use of this setting is
 357                                 optional. All processes remaining for
 358                                 a service after the commands
 359                                 configured in this option are run are
 360                                 terminated according to the
 361                                 <varname>KillMode=</varname> setting
 362                                 (see below). If this option is not
 363                                 specified the process is terminated
 364                                 right-away when service stop is
 365                                 requested. Specifier and environment
 366                                 variable substitution is supported
 367                                 (including
 368                                 <literal>$(MAINPID)</literal>, see
 369                                 above).</para></listitem>
 370                         </varlistentry>
 371
 372                         <varlistentry>
 373                                 <term><varname>ExecStopPost=</varname></term>
 374                                 <listitem><para>Additional commands
 375                                 that are executed after the service
 376                                 was stopped using the commands
 377                                 configured in
 378                                 <varname>ExecStop=</varname>. This
 379                                 argument takes multiple command lines,
 380                                 following the same scheme as pointed
 381                                 out for
 382                                 <varname>ExecStartPre</varname>. Use
 383                                 of these settings is
 384                                 optional. Specifier and environment
 385                                 variable substitution is
 386                                 supported.</para></listitem>
 387                         </varlistentry>
 388
 389                         <varlistentry>
 390                                 <term><varname>RestartSec=</varname></term>
 391                                 <listitem><para>Configures the time to
 392                                 sleep before restarting a service (as
 393                                 configured with
 394                                 <varname>Restart=</varname>). Takes a
 395                                 unit-less value in seconds, or a time
 396                                 span value such as "5min
 397                                 20s". Defaults to
 398                                 100ms.</para></listitem>
 399                         </varlistentry>
 400
 401                         <varlistentry>
 402                                 <term><varname>TimeoutSec=</varname></term>
 403                                 <listitem><para>Configures the time to
 404                                 wait for start-up and stop. If a
 405                                 daemon service does not signal
 406                                 start-up completion within the
 407                                 configured time the service will be
 408                                 considered failed and be shut down
 409                                 again. If a service is asked to stop
 410                                 but does not terminate in the
 411                                 specified time it will be terminated
 412                                 forcibly via SIGTERM, and after
 413                                 another delay of this time with
 414                                 SIGKILL. (See
 415                                 <varname>KillMode=</varname>
 416                                 below.) Takes a unit-less value in seconds, or a
 417                                 time span value such as "5min
 418                                 20s". Pass 0 to disable the timeout
 419                                 logic. Defaults to
 420                                 60s.</para></listitem>
 421                         </varlistentry>
 422
 423                         <varlistentry>
 424                                 <term><varname>Restart=</varname></term>
 425                                 <listitem><para>Configures whether the
 426                                 main service process shall be restarted when
 427                                 it exists. Takes one of
 428                                 <option>once</option>,
 429                                 <option>restart-on-success</option> or
 430                                 <option>restart-always</option>. If
 431                                 set to <option>once</option> (the
 432                                 default) the service will not be
 433                                 restarted when it exits. If set to
 434                                 <option>restart-on-success</option> it
 435                                 will be restarted only when it exited
 436                                 cleanly, i.e. terminated with an exit
 437                                 code of 0. If set to
 438                                 <option>restart-always</option> the
 439                                 service will be restarted regardless
 440                                 whether it exited cleanly or not, or
 441                                 got terminated abnormally by a
 442                                 signal.</para></listitem>
 443                         </varlistentry>
 444
 445                         <varlistentry>
 446                                 <term><varname>PermissionsStartOnly=</varname></term>
 447                                 <listitem><para>Takes a boolean
 448                                 argument. If true, the permission
 449                                 related execution options as
 450                                 configured with
 451                                 <varname>User=</varname> and similar
 452                                 options (see
 453                                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 454                                 for more information) are only applied
 455                                 to the process started with
 456                                 <varname>ExecStart=</varname>, and not
 457                                 to the various other
 458                                 <varname>ExecStartPre=</varname>,
 459                                 <varname>ExecStartPost=</varname>,
 460                                 <varname>ExecReload=</varname>,
 461                                 <varname>ExecStop=</varname>,
 462                                 <varname>ExecStopPost=</varname>
 463                                 commands. If false, the setting is
 464                                 applied to all configured commands the
 465                                 same way. Defaults to
 466                                 false.</para></listitem>
 467                         </varlistentry>
 468
 469                         <varlistentry>
 470                                 <term><varname>RootDirectoryStartOnly=</varname></term>
 471                                 <listitem><para>Takes a boolean
 472                                 argument. If true, the root directory
 473                                 as configured with the
 474                                 <varname>RootDirectory=</varname>
 475                                 option (see
 476                                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 477                                 for more information) is only applied
 478                                 to the process started with
 479                                 <varname>ExecStart=</varname>, and not
 480                                 to the various other
 481                                 <varname>ExecStartPre=</varname>,
 482                                 <varname>ExecStartPost=</varname>,
 483                                 <varname>ExecReload=</varname>,
 484                                 <varname>ExecStop=</varname>,
 485                                 <varname>ExecStopPost=</varname>
 486                                 commands. If false, the setting is
 487                                 applied to all configured commands the
 488                                 same way. Defaults to
 489                                 false.</para></listitem>
 490                         </varlistentry>
 491
 492                         <varlistentry>
 493                                 <term><varname>SysVStartPriority=</varname></term>
 494                                 <listitem><para>Set the SysV start
 495                                 priority to use to order this service
 496                                 in relation to SysV services lacking
 497                                 LSB headers. This option is only
 498                                 necessary to fix ordering in relation
 499                                 to legacy SysV services, that have no
 500                                 ordering information encoded in the
 501                                 script headers. As such it should only
 502                                 be used as temporary compatibility
 503                                 option, and not be used in new unit
 504                                 files. Almost always it is a better
 505                                 choice to add explicit ordering
 506                                 directives via
 507                                 <varname>After=</varname> or
 508                                 <varname>Before=</varname>,
 509                                 instead. For more details see
 510                                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. If
 511                                 used, pass an integer value in the
 512                                 range 0-99.</para></listitem>
 513                         </varlistentry>
 514
 515                         <varlistentry>
 516                                 <term><varname>KillMode=</varname></term>
 517                                 <listitem><para>Specifies how
 518                                 processes of this service shall be
 519                                 killed. One of
 520                                 <option>control-group</option>,
 521                                 <option>process-group</option>,
 522                                 <option>process</option>,
 523                                 <option>none</option>.</para>
 524
 525                                 <para>If set to
 526                                 <option>control-group</option> all
 527                                 remaining processes in the control
 528                                 group of this service will be
 529                                 terminated on service stop, after the
 530                                 stop command (as configured with
 531                                 <varname>ExecStop=</varname>) is
 532                                 executed. If set to
 533                                 <option>process-group</option> only
 534                                 the members of the process group of
 535                                 the main service process are
 536                                 killed. If set to
 537                                 <option>process</option> only the main
 538                                 process itself is killed. If set to
 539                                 <option>none</option> no process is
 540                                 killed. In this case only the stop
 541                                 command will be executed on service
 542                                 stop, but no process be killed
 543                                 otherwise. Processes remaining alive
 544                                 after stop are left in their control
 545                                 group and the control group continues
 546                                 to exist after stop unless it is
 547                                 empty. Defaults to
 548                                 <option>control-croup</option>.</para>
 549
 550                                 <para>Processes will first be
 551                                 terminated via SIGTERM. If then after
 552                                 a delay (configured via the
 553                                 <varname>TimeoutSec=</varname> option)
 554                                 processes still remain, the
 555                                 termination request is repeated with
 556                                 the SIGKILL signal. See
 557                                 <citerefentry><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 558                                 for more
 559                                 information.</para></listitem>
 560                         </varlistentry>
 561
 562                         <varlistentry>
 563                                 <term><varname>NonBlocking=</varname></term>
 564                                 <listitem><para>Set O_NONBLOCK flag
 565                                 for all file descriptors passed via
 566                                 socket-based activation. If true, all
 567                                 file descriptors >= 3 (i.e. all except
 568                                 STDIN/STDOUT/STDERR) will have
 569                                 the O_NONBLOCK flag set and hence are in
 570                                 non-blocking mode. This option is only
 571                                 useful in conjunction with a socket
 572                                 unit, as described in
 573                                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Defaults
 574                                 to false.</para></listitem>
 575                         </varlistentry>
 576
 577                         <varlistentry>
 578                                 <term><varname>NotifyAccess=</varname></term>
 579                                 <listitem><para>Controls access to the
 580                                 service status notification socket, as
 581                                 accessible via the
 582                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 583                                 call. Takes one of
 584                                 <option>none</option> (the default),
 585                                 <option>main</option> or
 586                                 <option>all</option>. If
 587                                 <option>none</option> no daemon status
 588                                 updates are accepted by the service
 589                                 processes, all status update messages
 590                                 are ignored. If <option>main</option>
 591                                 only service updates sent from the
 592                                 main process of the service are
 593                                 accepted. If <option>all</option> all
 594                                 services updates from all members of
 595                                 the service's control group are
 596                                 accepted. This option must be set to
 597                                 open access to the notification socket
 598                                 when using
 599                                 <varname>Type=notify</varname> (see above).</para></listitem>
 600                         </varlistentry>
 601
 602                 </variablelist>
 603         </refsect1>
 604
 605         <refsect1>
 606                   <title>See Also</title>
 607                   <para>
 608                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 609                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 610                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 611                           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 612                   </para>
 613         </refsect1>
 614
 615 </refentry>