man/systemd.service.xml

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   7   This file is part of systemd.
   8
   9   Copyright 2010 Lennart Poettering
  10
  11   systemd is free software; you can redistribute it and/or modify it
  12   under the terms of the GNU Lesser General Public License as published by
  13   the Free Software Foundation; either version 2.1 of the License, or
  14   (at your option) any later version.
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  19   Lesser General Public License for more details.
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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>Service unit configuration</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename><replaceable>service</replaceable>.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, and in
  76                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  77                 which define the way the processes of the service are
  78                 terminated, and in
  79                 <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  80                 which configure resource control settings for the
  81                 processes of the service.</para>
  82
  83                 <para>Unless <varname>DefaultDependencies=</varname>
  84                 is set to <option>false</option>, service units will
  85                 implicitly have dependencies of type
  86                 <varname>Requires=</varname> and
  87                 <varname>After=</varname> on
  88                 <filename>basic.target</filename> as well as
  89                 dependencies of type <varname>Conflicts=</varname> and
  90                 <varname>Before=</varname> on
  91                 <filename>shutdown.target</filename>. These ensure
  92                 that normal service units pull in basic system
  93                 initialization, and are terminated cleanly prior to
  94                 system shutdown. Only services involved with early
  95                 boot or late system shutdown should disable this
  96                 option.</para>
  97
  98                 <para>If a service is requested under a certain name
  99                 but no unit configuration file is found, systemd looks
 100                 for a SysV init script by the same name (with the
 101                 <filename>.service</filename> suffix removed) and
 102                 dynamically creates a service unit from that
 103                 script. This is useful for compatibility with
 104                 SysV. Note that this compatibility is quite
 105                 comprehensive but not 100%. For details about the
 106                 incompatibilities, see the <ulink
 107                 url="http://www.freedesktop.org/wiki/Software/systemd/Incompatibilities">Incompatibilities
 108                 with SysV</ulink> document.
 109                 </para>
 110         </refsect1>
 111
 112         <refsect1>
 113                 <title>Options</title>
 114
 115                 <para>Service files must include a
 116                 <literal>[Service]</literal> section, which carries
 117                 information about the service and the process it
 118                 supervises. A number of options that may be used in
 119                 this section are shared with other unit types. These
 120                 options are documented in
 121                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 122                 and
 123                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
 124                 options specific to the <literal>[Service]</literal>
 125                 section of service units are the following:</para>
 126
 127                 <variablelist class='unit-directives'>
 128                         <varlistentry>
 129                                 <term><varname>Type=</varname></term>
 130
 131                                 <listitem><para>Configures the process
 132                                 start-up type for this service
 133                                 unit. One of <option>simple</option>,
 134                                 <option>forking</option>,
 135                                 <option>oneshot</option>,
 136                                 <option>dbus</option>,
 137                                 <option>notify</option> or
 138                                 <option>idle</option>.</para>
 139
 140                                 <para>If set to
 141                                 <option>simple</option> (the default
 142                                 if neither
 143                                 <varname>Type=</varname> nor
 144                                 <varname>BusName=</varname>, but
 145                                 <varname>ExecStart=</varname> are
 146                                 specified), it is expected that the
 147                                 process configured with
 148                                 <varname>ExecStart=</varname> is the
 149                                 main process of the service. In this
 150                                 mode, if the process offers
 151                                 functionality to other processes on
 152                                 the system, its communication channels
 153                                 should be installed before the daemon
 154                                 is started up (e.g. sockets set up by
 155                                 systemd, via socket activation), as
 156                                 systemd will immediately proceed
 157                                 starting follow-up units.</para>
 158
 159                                 <para>If set to
 160                                 <option>forking</option>, it is
 161                                 expected that the process configured
 162                                 with <varname>ExecStart=</varname>
 163                                 will call <function>fork()</function>
 164                                 as part of its start-up. The parent process is
 165                                 expected to exit when start-up is
 166                                 complete and all communication
 167                                 channels are set up. The child continues
 168                                 to run as the main daemon
 169                                 process. This is the behavior of
 170                                 traditional UNIX daemons. If this
 171                                 setting is used, it is recommended to
 172                                 also use the
 173                                 <varname>PIDFile=</varname> option, so
 174                                 that systemd can identify the main
 175                                 process of the daemon. systemd will
 176                                 proceed with starting follow-up units
 177                                 as soon as the parent process
 178                                 exits.</para>
 179
 180                                 <para>Behavior of
 181                                 <option>oneshot</option> is similar to
 182                                 <option>simple</option>; however, it
 183                                 is expected that the process has to
 184                                 exit before systemd starts follow-up
 185                                 units. <varname>RemainAfterExit=</varname>
 186                                 is particularly useful for this type
 187                                 of service. This is the implied
 188                                 default if neither
 189                                 <varname>Type=</varname> or
 190                                 <varname>ExecStart=</varname> are
 191                                 specified.</para>
 192
 193                                 <para>Behavior of
 194                                 <option>dbus</option> is similar to
 195                                 <option>simple</option>; however, it is
 196                                 expected that the daemon acquires a
 197                                 name on the D-Bus bus, as configured
 198                                 by
 199                                 <varname>BusName=</varname>. systemd
 200                                 will proceed with starting follow-up
 201                                 units after the D-Bus bus name has been
 202                                 acquired. Service units with this
 203                                 option configured implicitly gain
 204                                 dependencies on the
 205                                 <filename>dbus.socket</filename>
 206                                 unit. This type is the default if
 207                                 <varname>BusName=</varname> is
 208                                 specified.</para>
 209
 210                                 <para>Behavior of
 211                                 <option>notify</option> is similar to
 212                                 <option>simple</option>; however, it is
 213                                 expected that the daemon sends a
 214                                 notification message via
 215                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 216                                 or an equivalent call when it has finished
 217                                 starting up. systemd will proceed with
 218                                 starting follow-up units after this
 219                                 notification message has been sent. If
 220                                 this option is used,
 221                                 <varname>NotifyAccess=</varname> (see
 222                                 below) should be set to open access to
 223                                 the notification socket provided by
 224                                 systemd. If
 225                                 <varname>NotifyAccess=</varname> is
 226                                 not set, it will be implicitly set to
 227                                 <option>main</option>. Note that
 228                                 currently
 229                                 <varname>Type=</varname><option>notify</option>
 230                                 will not work if used in combination with
 231                                 <varname>PrivateNetwork=</varname><option>yes</option>.</para>
 232
 233                                 <para>Behavior of
 234                                 <option>idle</option> is very similar
 235                                 to <option>simple</option>; however,
 236                                 actual execution of the service
 237                                 binary is delayed until all jobs are
 238                                 dispatched. This may be used to avoid
 239                                 interleaving of output of shell
 240                                 services with the status output on the
 241                                 console.</para>
 242                                 </listitem>
 243                         </varlistentry>
 244
 245                         <varlistentry>
 246                                 <term><varname>RemainAfterExit=</varname></term>
 247
 248                                 <listitem><para>Takes a boolean value
 249                                 that specifies whether the service
 250                                 shall be considered active even when
 251                                 all its processes exited. Defaults to
 252                                 <option>no</option>.</para>
 253                                 </listitem>
 254                         </varlistentry>
 255
 256                         <varlistentry>
 257                                 <term><varname>GuessMainPID=</varname></term>
 258
 259                                 <listitem><para>Takes a boolean value
 260                                 that specifies whether systemd should
 261                                 try to guess the main PID of a service
 262                                 if it cannot be determined
 263                                 reliably. This option is ignored
 264                                 unless <option>Type=forking</option>
 265                                 is set and <option>PIDFile=</option>
 266                                 is unset because for the other types
 267                                 or with an explicitly configured PID
 268                                 file, the main PID is always known. The
 269                                 guessing algorithm might come to
 270                                 incorrect conclusions if a daemon
 271                                 consists of more than one process. If
 272                                 the main PID cannot be determined,
 273                                 failure detection and automatic
 274                                 restarting of a service will not work
 275                                 reliably. Defaults to
 276                                 <option>yes</option>.</para>
 277                                 </listitem>
 278                         </varlistentry>
 279
 280                         <varlistentry>
 281                                 <term><varname>PIDFile=</varname></term>
 282
 283                                 <listitem><para>Takes an absolute file
 284                                 name pointing to the PID file of this
 285                                 daemon. Use of this option is
 286                                 recommended for services where
 287                                 <varname>Type=</varname> is set to
 288                                 <option>forking</option>. systemd will
 289                                 read the PID of the main process of
 290                                 the daemon after start-up of the
 291                                 service. systemd will not write to the
 292                                 file configured here.</para>
 293                                 </listitem>
 294                         </varlistentry>
 295
 296                         <varlistentry>
 297                                 <term><varname>BusName=</varname></term>
 298
 299                                 <listitem><para>Takes a D-Bus bus
 300                                 name that this service is reachable
 301                                 as. This option is mandatory for
 302                                 services where
 303                                 <varname>Type=</varname> is set to
 304                                 <option>dbus</option>.</para>
 305                                 </listitem>
 306                         </varlistentry>
 307
 308                         <varlistentry>
 309                                 <term><varname>BusPolicy=</varname></term>
 310
 311                                 <listitem><para>If specified, a custom
 312                                 <ulink url="https://code.google.com/p/d-bus/">kdbus</ulink>
 313                                 endpoint will be created and installed as the
 314                                 default bus node for the service. Such a custom
 315                                 endpoint can hold an own set of policy rules
 316                                 that are enforced on top of the bus-wide ones.
 317                                 The custom endpoint is named after the service
 318                                 it was created for, and its node will be
 319                                 bind-mounted over the default bus node
 320                                 location, so the service can only access the
 321                                 bus through its own endpoint. Note that custom
 322                                 bus endpoints default to a 'deny all' policy.
 323                                 Hence, if at least one
 324                                 <varname>BusPolicy=</varname> directive is
 325                                 given, you have to make sure to add explicit
 326                                 rules for everything the service should be able
 327                                 to do.</para>
 328                                 <para>The value of this directive is comprised
 329                                 of two parts; the bus name, and a verb to
 330                                 specify to granted access, which is one of
 331                                 <option>see</option>,
 332                                 <option>talk</option>, or
 333                                 <option>own</option>.
 334                                 <option>talk</option> implies
 335                                 <option>see</option>, and <option>own</option>
 336                                 implies both <option>talk</option> and
 337                                 <option>see</option>.
 338                                 If multiple access levels are specified for the
 339                                 same bus name, the most powerful one takes
 340                                 effect.
 341                                 </para>
 342                                 <para>Examples:</para>
 343                                 <programlisting>BusPolicy=org.freedesktop.systemd1 talk</programlisting>
 344                                 <programlisting>BusPolicy=org.foo.bar see</programlisting>
 345                                 <para>This option is only available on kdbus enabled systems.</para>
 346                                 </listitem>
 347                         </varlistentry>
 348
 349                         <varlistentry>
 350                                 <term><varname>ExecStart=</varname></term>
 351                                 <listitem><para>Commands with their
 352                                 arguments that are executed when this
 353                                 service is started. The value is split
 354                                 into zero or more command lines is
 355                                 according to the rules described below
 356                                 (see section "Command Lines" below).
 357                                 </para>
 358
 359                                 <para>When <varname>Type</varname> is
 360                                 not <option>oneshot</option>, only one
 361                                 command may and must be given. When
 362                                 <varname>Type=oneshot</varname> is
 363                                 used, zero or more commands may be
 364                                 specified. This can be specified by
 365                                 providing multiple command lines in
 366                                 the same directive, or alternatively,
 367                                 this directive may be specified more
 368                                 than once with the same effect. If the
 369                                 empty string is assigned to this
 370                                 option, the list of commands to start
 371                                 is reset, prior assignments of this
 372                                 option will have no effect. If no
 373                                 <varname>ExecStart=</varname> is
 374                                 specified, then the service must have
 375                                 <varname>RemainAfterExit=yes</varname>
 376                                 set.</para>
 377
 378                                 <para>For each of the specified
 379                                 commands, the first argument must be
 380                                 an absolute path to an executable.
 381                                 Optionally, if this file name is
 382                                 prefixed with <literal>@</literal>,
 383                                 the second token will be passed as
 384                                 <literal>argv[0]</literal> to the
 385                                 executed process, followed by the
 386                                 further arguments specified. If the
 387                                 absolute filename is prefixed with
 388                                 <literal>-</literal>, an exit code of
 389                                 the command normally considered a
 390                                 failure (i.e. non-zero exit status or
 391                                 abnormal exit due to signal) is
 392                                 ignored and considered success. If
 393                                 both <literal>-</literal> and
 394                                 <literal>@</literal> are used, they
 395                                 can appear in either order.</para>
 396
 397                                 <para>If more than one command is
 398                                 specified, the commands are invoked
 399                                 sequentially in the order they appear
 400                                 in the unit file. If one of the
 401                                 commands fails (and is not prefixed
 402                                 with <literal>-</literal>), other
 403                                 lines are not executed, and the unit
 404                                 is considered failed.</para>
 405
 406                                 <para>Unless
 407                                 <varname>Type=forking</varname> is
 408                                 set, the process started via this
 409                                 command line will be considered the
 410                                 main process of the daemon.</para>
 411
 412                               </listitem>
 413                         </varlistentry>
 414
 415                         <varlistentry>
 416                                 <term><varname>ExecStartPre=</varname></term>
 417                                 <term><varname>ExecStartPost=</varname></term>
 418                                 <listitem><para>Additional commands
 419                                 that are executed before or after
 420                                 the command in
 421                                 <varname>ExecStart=</varname>, respectively.
 422                                 Syntax is the same as for
 423                                 <varname>ExecStart=</varname>, except
 424                                 that multiple command lines are allowed
 425                                 and the commands are executed one
 426                                 after the other, serially.</para>
 427
 428                                 <para>If any of those commands (not
 429                                 prefixed with <literal>-</literal>)
 430                                 fail, the rest are not executed and
 431                                 the unit is considered failed.</para>
 432                                 </listitem>
 433                         </varlistentry>
 434
 435                         <varlistentry>
 436                                 <term><varname>ExecReload=</varname></term>
 437                                 <listitem><para>Commands to execute to
 438                                 trigger a configuration reload in the
 439                                 service. This argument takes multiple
 440                                 command lines, following the same
 441                                 scheme as described for
 442                                 <varname>ExecStart=</varname>
 443                                 above. Use of this setting is
 444                                 optional. Specifier and environment
 445                                 variable substitution is supported
 446                                 here following the same scheme as for
 447                                 <varname>ExecStart=</varname>.</para>
 448
 449                                 <para>One additional, special
 450                                 environment variable is set: if known,
 451                                 <varname>$MAINPID</varname> is set to
 452                                 the main process of the daemon, and
 453                                 may be used for command lines like the
 454                                 following:</para>
 455
 456                                 <programlisting>/bin/kill -HUP $MAINPID</programlisting>
 457
 458                                 <para>Note however that reloading a
 459                                 daemon by sending a signal (as with
 460                                 the example line above) is usually not
 461                                 a good choice, because this is an
 462                                 asynchronous operation and hence not
 463                                 suitable to order reloads of multiple
 464                                 services against each other. It is
 465                                 strongly recommended to set
 466                                 <varname>ExecReload=</varname> to a
 467                                 command that not only triggers a
 468                                 configuration reload of the daemon,
 469                                 but also synchronously waits for it to
 470                                 complete.</para>
 471                                 </listitem>
 472                         </varlistentry>
 473
 474                         <varlistentry>
 475                                 <term><varname>ExecStop=</varname></term>
 476                                 <listitem><para>Commands to execute to
 477                                 stop the service started via
 478                                 <varname>ExecStart=</varname>. This
 479                                 argument takes multiple command lines,
 480                                 following the same scheme as described
 481                                 for <varname>ExecStart=</varname>
 482                                 above. Use of this setting is
 483                                 optional. After the commands configured
 484                                 in this option are run, all processes
 485                                 remaining for a service are
 486                                 terminated according to the
 487                                 <varname>KillMode=</varname> setting
 488                                 (see
 489                                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>). If
 490                                 this option is not specified, the
 491                                 process is terminated immediately when
 492                                 service stop is requested. Specifier
 493                                 and environment variable substitution
 494                                 is supported (including
 495                                 <varname>$MAINPID</varname>, see
 496                                 above).</para></listitem>
 497                         </varlistentry>
 498
 499                         <varlistentry>
 500                                 <term><varname>ExecStopPost=</varname></term>
 501                                 <listitem><para>Additional commands
 502                                 that are executed after the service
 503                                 was stopped. This includes cases where
 504                                 the commands configured in
 505                                 <varname>ExecStop=</varname> were used,
 506                                 where the service does not have any
 507                                 <varname>ExecStop=</varname> defined, or
 508                                 where the service exited unexpectedly. This
 509                                 argument takes multiple command lines,
 510                                 following the same scheme as described
 511                                 for <varname>ExecStart</varname>. Use
 512                                 of these settings is
 513                                 optional. Specifier and environment
 514                                 variable substitution is
 515                                 supported.</para></listitem>
 516                         </varlistentry>
 517
 518                         <varlistentry>
 519                                 <term><varname>RestartSec=</varname></term>
 520                                 <listitem><para>Configures the time to
 521                                 sleep before restarting a service (as
 522                                 configured with
 523                                 <varname>Restart=</varname>). Takes a
 524                                 unit-less value in seconds, or a time
 525                                 span value such as "5min
 526                                 20s". Defaults to
 527                                 100ms.</para></listitem>
 528                         </varlistentry>
 529
 530                         <varlistentry>
 531                                 <term><varname>TimeoutStartSec=</varname></term>
 532                                 <listitem><para>Configures the time to
 533                                 wait for start-up. If a
 534                                 daemon service does not signal
 535                                 start-up completion within the
 536                                 configured time, the service will be
 537                                 considered failed and will be shut
 538                                 down again.
 539                                 Takes a unit-less value in seconds, or a
 540                                 time span value such as "5min
 541                                 20s". Pass <literal>0</literal> to
 542                                 disable the timeout logic. Defaults to
 543                                 <varname>DefaultTimeoutStartSec=</varname> from
 544                                 the manager configuration file, except
 545                                 when <varname>Type=oneshot</varname> is
 546                                 used, in which case the timeout
 547                                 is disabled by default
 548                                 (see <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
 549                                 </para></listitem>
 550                         </varlistentry>
 551
 552                         <varlistentry>
 553                                 <term><varname>TimeoutStopSec=</varname></term>
 554                                 <listitem><para>Configures the time to
 555                                 wait for stop. If a service is asked
 556                                 to stop, but does not terminate in the
 557                                 specified time, it will be terminated
 558                                 forcibly via <constant>SIGTERM</constant>,
 559                                 and after another timeout of equal duration
 560                                 with <constant>SIGKILL</constant> (see
 561                                 <varname>KillMode=</varname>
 562                                 in <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
 563                                 Takes a unit-less value in seconds, or a
 564                                 time span value such as "5min
 565                                 20s". Pass <literal>0</literal> to disable
 566                                 the timeout logic. Defaults to
 567                                 <varname>DefaultTimeoutStopSec=</varname> from the
 568                                 manager configuration file
 569                                 (see <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
 570                                 </para></listitem>
 571                         </varlistentry>
 572
 573                         <varlistentry>
 574                                 <term><varname>TimeoutSec=</varname></term>
 575                                 <listitem><para>A shorthand for configuring
 576                                 both <varname>TimeoutStartSec=</varname>
 577                                 and <varname>TimeoutStopSec=</varname>
 578                                 to the specified value.
 579                                 </para></listitem>
 580                         </varlistentry>
 581
 582                         <varlistentry>
 583                                 <term><varname>WatchdogSec=</varname></term>
 584                                 <listitem><para>Configures the
 585                                 watchdog timeout for a service. The
 586                                 watchdog is activated when the start-up is
 587                                 completed. The service must call
 588                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 589                                 regularly with <literal>WATCHDOG=1</literal>
 590                                 (i.e. the "keep-alive ping"). If the time
 591                                 between two such calls is larger than
 592                                 the configured time, then the service
 593                                 is placed in a failed state and it will
 594                                 be terminated with <varname>SIGABRT</varname>.
 595                                 By setting <varname>Restart=</varname> to
 596                                 <option>on-failure</option> or
 597                                 <option>always</option>, the service
 598                                 will be automatically restarted. The
 599                                 time configured here will be passed to
 600                                 the executed service process in the
 601                                 <varname>WATCHDOG_USEC=</varname>
 602                                 environment variable. This allows
 603                                 daemons to automatically enable the
 604                                 keep-alive pinging logic if watchdog
 605                                 support is enabled for the service. If
 606                                 this option is used,
 607                                 <varname>NotifyAccess=</varname> (see
 608                                 below) should be set to open access to
 609                                 the notification socket provided by
 610                                 systemd. If
 611                                 <varname>NotifyAccess=</varname> is
 612                                 not set, it will be implicitly set to
 613                                 <option>main</option>. Defaults to 0,
 614                                 which disables this
 615                                 feature.</para></listitem>
 616                         </varlistentry>
 617
 618                         <varlistentry>
 619                                 <term><varname>Restart=</varname></term>
 620                                 <listitem><para>Configures whether the
 621                                 service shall be restarted when the
 622                                 service process exits, is killed,
 623                                 or a timeout is reached. The service
 624                                 process may be the main service
 625                                 process, but it may also be one of the
 626                                 processes specified with
 627                                 <varname>ExecStartPre=</varname>,
 628                                 <varname>ExecStartPost=</varname>,
 629                                 <varname>ExecStop=</varname>,
 630                                 <varname>ExecStopPost=</varname>, or
 631                                 <varname>ExecReload=</varname>.
 632                                 When the death of the process is a
 633                                 result of systemd operation (e.g. service
 634                                 stop or restart), the service will not be
 635                                 restarted. Timeouts include missing
 636                                 the watchdog "keep-alive ping"
 637                                 deadline and a service start, reload,
 638                                 and stop operation timeouts.</para>
 639
 640                                 <para>Takes one of
 641                                 <option>no</option>,
 642                                 <option>on-success</option>,
 643                                 <option>on-failure</option>,
 644                                 <option>on-abnormal</option>,
 645                                 <option>on-watchdog</option>,
 646                                 <option>on-abort</option>, or
 647                                 <option>always</option>. If set to
 648                                 <option>no</option> (the default), the
 649                                 service will not be restarted. If set
 650                                 to <option>on-success</option>, it
 651                                 will be restarted only when the
 652                                 service process exits cleanly.  In
 653                                 this context, a clean exit means an
 654                                 exit code of 0, or one of the signals
 655                                 <constant>SIGHUP</constant>,
 656                                 <constant>SIGINT</constant>,
 657                                 <constant>SIGTERM</constant> or
 658                                 <constant>SIGPIPE</constant>, and
 659                                 additionally, exit statuses and
 660                                 signals specified in
 661                                 <varname>SuccessExitStatus=</varname>.
 662                                 If set to <option>on-failure</option>,
 663                                 the service will be restarted when the
 664                                 process exits with a non-zero exit
 665                                 code, is terminated by a signal
 666                                 (including on core dump, but excluding
 667                                 the aforementiond four signals), when
 668                                 an operation (such as service reload)
 669                                 times out, and when the configured
 670                                 watchdog timeout is triggered.  If set
 671                                 to <option>on-abnormal</option>, the
 672                                 service will be restarted when the
 673                                 process is terminated by a signal
 674                                 (including on core dump, excluding the
 675                                 aforementioned four signals), when an
 676                                 operation times out, or when the
 677                                 watchdog timeout is triggered. If set
 678                                 to <option>on-abort</option>, the
 679                                 service will be restarted only if the
 680                                 service process exits due to an
 681                                 uncaught signal not specified as a
 682                                 clean exit status.  If set to
 683                                 <option>on-watchdog</option>, the
 684                                 service will be restarted only if the
 685                                 watchdog timeout for the service
 686                                 expires.  If set to
 687                                 <option>always</option>, the service
 688                                 will be restarted regardless of
 689                                 whether it exited cleanly or not, got
 690                                 terminated abnormally by a signal, or
 691                                 hit a timeout.</para>
 692
 693                                 <table>
 694                                         <title>Exit causes and the effect of the <varname>Restart=</varname> settings on them</title>
 695
 696                                         <tgroup cols='2'>
 697                                                 <colspec colname='path' />
 698                                                 <colspec colname='expl' />
 699                                                 <thead>
 700                                                         <row>
 701                                                                 <entry>Restart settings/Exit causes</entry>
 702                                                                 <entry><option>no</option></entry>
 703                                                                 <entry><option>always</option></entry>
 704                                                                 <entry><option>on-success</option></entry>
 705                                                                 <entry><option>on-failure</option></entry>
 706                                                                 <entry><option>on-abnormal</option></entry>
 707                                                                 <entry><option>on-abort</option></entry>
 708                                                                 <entry><option>on-watchdog</option></entry>
 709                                                         </row>
 710                                                 </thead>
 711                                                 <tbody>
 712                                                         <row>
 713                                                                 <entry>Clean exit code or signal</entry>
 714                                                                 <entry/>
 715                                                                 <entry>X</entry>
 716                                                                 <entry>X</entry>
 717                                                                 <entry/>
 718                                                                 <entry/>
 719                                                                 <entry/>
 720                                                                 <entry/>
 721                                                         </row>
 722                                                         <row>
 723                                                                 <entry>Unclean exit code</entry>
 724                                                                 <entry/>
 725                                                                 <entry>X</entry>
 726                                                                 <entry/>
 727                                                                 <entry>X</entry>
 728                                                                 <entry/>
 729                                                                 <entry/>
 730                                                                 <entry/>
 731                                                         </row>
 732                                                         <row>
 733                                                                 <entry>Unclean signal</entry>
 734                                                                 <entry/>
 735                                                                 <entry>X</entry>
 736                                                                 <entry/>
 737                                                                 <entry>X</entry>
 738                                                                 <entry>X</entry>
 739                                                                 <entry>X</entry>
 740                                                                 <entry/>
 741                                                         </row>
 742                                                         <row>
 743                                                                 <entry>Timeout</entry>
 744                                                                 <entry/>
 745                                                                 <entry>X</entry>
 746                                                                 <entry/>
 747                                                                 <entry>X</entry>
 748                                                                 <entry>X</entry>
 749                                                                 <entry/>
 750                                                                 <entry/>
 751                                                         </row>
 752                                                         <row>
 753                                                                 <entry>Watchdog</entry>
 754                                                                 <entry/>
 755                                                                 <entry>X</entry>
 756                                                                 <entry/>
 757                                                                 <entry>X</entry>
 758                                                                 <entry>X</entry>
 759                                                                 <entry/>
 760                                                                 <entry>X</entry>
 761                                                         </row>
 762                                                 </tbody>
 763                                         </tgroup>
 764                                 </table>
 765
 766                                 <para>As exceptions to the setting
 767                                 above the service will not be
 768                                 restarted if the exit code or signal
 769                                 is specified in
 770                                 <varname>RestartPreventExitStatus=</varname>
 771                                 (see below). Also, the services will
 772                                 always be restarted if the exit code
 773                                 or signal is specified in
 774                                 <varname>RestartForceExitStatus=</varname>
 775                                 (see below).</para>
 776
 777                                 <para>Setting this to
 778                                 <option>on-failure</option> is the
 779                                 recommended choice for long-running
 780                                 services, in order to increase
 781                                 reliability by attempting automatic
 782                                 recovery from errors. For services
 783                                 that shall be able to terminate on
 784                                 their own choice (and avoid
 785                                 immediate restarting),
 786                                 <option>on-abnormal</option> is an
 787                                 alternative choice.</para>
 788                                 </listitem>
 789                         </varlistentry>
 790
 791                         <varlistentry>
 792                                 <term><varname>SuccessExitStatus=</varname></term>
 793                                 <listitem><para>Takes a list of exit
 794                                 status definitions that when returned
 795                                 by the main service process will be
 796                                 considered successful termination, in
 797                                 addition to the normal successful exit
 798                                 code 0 and the signals <constant>SIGHUP</constant>, <constant>SIGINT</constant>,
 799                                 <constant>SIGTERM</constant>, and <constant>SIGPIPE</constant>. Exit status
 800                                 definitions can either be numeric exit
 801                                 codes or termination signal names,
 802                                 separated by spaces. For example:
 803                                 <programlisting>SuccessExitStatus=1 2 8 SIGKILL</programlisting>
 804                                 ensures that exit codes 1, 2, 8 and
 805                                 the termination signal
 806                                 <constant>SIGKILL</constant> are
 807                                 considered clean service terminations.
 808                                 </para>
 809
 810                                 <para>Note that if a process has a
 811                                 signal handler installed and exits by
 812                                 calling
 813                                 <citerefentry><refentrytitle>_exit</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 814                                 in response to a signal, the
 815                                 information about the signal is lost.
 816                                 Programs should instead perform cleanup and kill themselves with the same signal instead. See
 817                                 <ulink url="http://www.cons.org/cracauer/sigint.html">Proper handling of SIGINT/SIGQUIT — How to be a proper program</ulink>.</para>
 818
 819                                 <para>This option may appear more than once,
 820                                 in which case the list of successful
 821                                 exit statuses is merged. If the empty
 822                                 string is assigned to this option, the
 823                                 list is reset, all prior assignments
 824                                 of this option will have no
 825                                 effect.</para></listitem>
 826                         </varlistentry>
 827
 828                         <varlistentry>
 829                                 <term><varname>RestartPreventExitStatus=</varname></term>
 830                                 <listitem><para>Takes a list of exit
 831                                 status definitions that when returned
 832                                 by the main service process will
 833                                 prevent automatic service restarts,
 834                                 regardless of the restart setting
 835                                 configured with
 836                                 <varname>Restart=</varname>. Exit
 837                                 status definitions can either be
 838                                 numeric exit codes or termination
 839                                 signal names, and are separated by
 840                                 spaces. Defaults to the empty list, so
 841                                 that, by default, no exit status is
 842                                 excluded from the configured restart
 843                                 logic. For example:
 844                                 <programlisting>RestartPreventExitStatus=1 6 SIGABRT</programlisting> ensures that exit
 845                                 codes 1 and 6 and the termination
 846                                 signal <constant>SIGABRT</constant> will
 847                                 not result in automatic service
 848                                 restarting. This
 849                                 option may appear more than once, in
 850                                 which case the list of restart-preventing
 851                                 statuses is merged. If the empty
 852                                 string is assigned to this option, the
 853                                 list is reset and all prior assignments
 854                                 of this option will have no
 855                                 effect.</para></listitem>
 856                         </varlistentry>
 857
 858                         <varlistentry>
 859                                 <term><varname>RestartForceExitStatus=</varname></term>
 860                                 <listitem><para>Takes a list of exit
 861                                 status definitions that when returned
 862                                 by the main service process will force
 863                                 automatic service restarts, regardless
 864                                 of the restart setting configured with
 865                                 <varname>Restart=</varname>. The
 866                                 argument format is similar to
 867                                 <varname>RestartPreventExitStatus=</varname>.</para></listitem>
 868                         </varlistentry>
 869
 870                         <varlistentry>
 871                                 <term><varname>PermissionsStartOnly=</varname></term>
 872                                 <listitem><para>Takes a boolean
 873                                 argument. If true, the permission-related
 874                                 execution options, as
 875                                 configured with
 876                                 <varname>User=</varname> and similar
 877                                 options (see
 878                                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 879                                 for more information), are only applied
 880                                 to the process started with
 881                                 <varname>ExecStart=</varname>, and not
 882                                 to the various other
 883                                 <varname>ExecStartPre=</varname>,
 884                                 <varname>ExecStartPost=</varname>,
 885                                 <varname>ExecReload=</varname>,
 886                                 <varname>ExecStop=</varname>, and
 887                                 <varname>ExecStopPost=</varname>
 888                                 commands. If false, the setting is
 889                                 applied to all configured commands the
 890                                 same way. Defaults to
 891                                 false.</para></listitem>
 892                         </varlistentry>
 893
 894                         <varlistentry>
 895                                 <term><varname>RootDirectoryStartOnly=</varname></term>
 896                                 <listitem><para>Takes a boolean
 897                                 argument. If true, the root directory,
 898                                 as configured with the
 899                                 <varname>RootDirectory=</varname>
 900                                 option (see
 901                                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 902                                 for more information), is only applied
 903                                 to the process started with
 904                                 <varname>ExecStart=</varname>, and not
 905                                 to the various other
 906                                 <varname>ExecStartPre=</varname>,
 907                                 <varname>ExecStartPost=</varname>,
 908                                 <varname>ExecReload=</varname>,
 909                                 <varname>ExecStop=</varname>, and
 910                                 <varname>ExecStopPost=</varname>
 911                                 commands. If false, the setting is
 912                                 applied to all configured commands the
 913                                 same way. Defaults to
 914                                 false.</para></listitem>
 915                         </varlistentry>
 916
 917                         <varlistentry>
 918                                 <term><varname>NonBlocking=</varname></term>
 919                                 <listitem><para>Set the
 920                                 <constant>O_NONBLOCK</constant> flag
 921                                 for all file descriptors passed via
 922                                 socket-based activation. If true, all
 923                                 file descriptors >= 3 (i.e. all except
 924                                 stdin, stdout, and stderr) will have
 925                                 the <constant>O_NONBLOCK</constant> flag
 926                                 set and hence are in
 927                                 non-blocking mode. This option is only
 928                                 useful in conjunction with a socket
 929                                 unit, as described in
 930                                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Defaults
 931                                 to false.</para></listitem>
 932                         </varlistentry>
 933
 934                         <varlistentry>
 935                                 <term><varname>NotifyAccess=</varname></term>
 936                                 <listitem><para>Controls access to the
 937                                 service status notification socket, as
 938                                 accessible via the
 939                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 940                                 call. Takes one of
 941                                 <option>none</option> (the default),
 942                                 <option>main</option> or
 943                                 <option>all</option>. If
 944                                 <option>none</option>, no daemon status
 945                                 updates are accepted from the service
 946                                 processes, all status update messages
 947                                 are ignored. If <option>main</option>,
 948                                 only service updates sent from the
 949                                 main process of the service are
 950                                 accepted. If <option>all</option>, all
 951                                 services updates from all members of
 952                                 the service's control group are
 953                                 accepted. This option should be set to
 954                                 open access to the notification socket
 955                                 when using
 956                                 <varname>Type=notify</varname> or
 957                                 <varname>WatchdogSec=</varname> (see
 958                                 above). If those options are used but
 959                                 <varname>NotifyAccess=</varname> is not
 960                                 configured, it will be implicitly set
 961                                 to
 962                                 <option>main</option>.</para></listitem>
 963                         </varlistentry>
 964
 965                         <varlistentry>
 966                                 <term><varname>Sockets=</varname></term>
 967                                 <listitem><para>Specifies the name of
 968                                 the socket units this service shall
 969                                 inherit socket file descriptors
 970                                 from when the service is
 971                                 started. Normally it should not be
 972                                 necessary to use this setting as all
 973                                 socket file descriptors whose unit
 974                                 shares the same name as the service
 975                                 (subject to the different unit name
 976                                 suffix of course) are passed to the
 977                                 spawned process.</para>
 978
 979                                 <para>Note that the same socket file
 980                                 descriptors may be passed to multiple
 981                                 processes simultaneously. Also note
 982                                 that a different service may be
 983                                 activated on incoming socket traffic
 984                                 than the one which is ultimately
 985                                 configured to inherit the socket file
 986                                 descriptors. Or in other words: the
 987                                 <varname>Service=</varname> setting of
 988                                 <filename>.socket</filename> units
 989                                 does not have to match the inverse of
 990                                 the <varname>Sockets=</varname>
 991                                 setting of the
 992                                 <filename>.service</filename> it
 993                                 refers to.</para>
 994
 995                                 <para>This option may appear more than
 996                                 once, in which case the list of socket
 997                                 units is merged. If the empty string
 998                                 is assigned to this option, the list of
 999                                 sockets is reset, and all prior uses of
1000                                 this setting will have no
1001                                 effect.</para></listitem>
1002                         </varlistentry>
1003
1004                         <varlistentry>
1005                                 <term><varname>StartLimitInterval=</varname></term>
1006                                 <term><varname>StartLimitBurst=</varname></term>
1007
1008                                 <listitem><para>Configure service
1009                                 start rate limiting. By default,
1010                                 services which are started more
1011                                 than 5 times within 10 seconds are not
1012                                 permitted to start any more times
1013                                 until the 10 second interval ends. With
1014                                 these two options, this rate limiting
1015                                 may be modified. Use
1016                                 <varname>StartLimitInterval=</varname>
1017                                 to configure the checking interval (defaults to
1018                                 <varname>DefaultStartLimitInterval=</varname> in
1019                                 manager configuration file, set to 0 to disable
1020                                 any kind of rate limiting). Use
1021                                 <varname>StartLimitBurst=</varname> to
1022                                 configure how many starts per interval
1023                                 are allowed (defaults to
1024                                 <varname>DefaultStartLimitBurst=</varname> in
1025                                 manager configuration file). These
1026                                 configuration options are particularly
1027                                 useful in conjunction with
1028                                 <varname>Restart=</varname>; however,
1029                                 they apply to all kinds of starts
1030                                 (including manual), not just those
1031                                 triggered by the
1032                                 <varname>Restart=</varname> logic.
1033                                 Note that units which are configured
1034                                 for <varname>Restart=</varname> and
1035                                 which reach the start limit are not
1036                                 attempted to be restarted anymore;
1037                                 however, they may still be restarted
1038                                 manually at a later point, from which
1039                                 point on, the restart logic is again
1040                                 activated. Note that
1041                                 <command>systemctl
1042                                 reset-failed</command> will cause the
1043                                 restart rate counter for a service to
1044                                 be flushed, which is useful if the
1045                                 administrator wants to manually start
1046                                 a service and the start limit
1047                                 interferes with
1048                                 that.</para></listitem>
1049                         </varlistentry>
1050
1051                         <varlistentry>
1052                                 <term><varname>StartLimitAction=</varname></term>
1053
1054                                 <listitem><para>Configure the action
1055                                 to take if the rate limit configured
1056                                 with
1057                                 <varname>StartLimitInterval=</varname>
1058                                 and
1059                                 <varname>StartLimitBurst=</varname> is
1060                                 hit. Takes one of
1061                                 <option>none</option>,
1062                                 <option>reboot</option>,
1063                                 <option>reboot-force</option>,
1064                                 <option>reboot-immediate</option>,
1065                                 <option>poweroff</option>,
1066                                 <option>poweroff-force</option> or
1067                                 <option>poweroff-immediate</option>. If
1068                                 <option>none</option> is set, hitting
1069                                 the rate limit will trigger no action
1070                                 besides that the start will not be
1071                                 permitted. <option>reboot</option>
1072                                 causes a reboot following the normal
1073                                 shutdown procedure (i.e. equivalent to
1074                                 <command>systemctl reboot</command>).
1075                                 <option>reboot-force</option> causes a
1076                                 forced reboot which will terminate all
1077                                 processes forcibly but should cause no
1078                                 dirty file systems on reboot
1079                                 (i.e. equivalent to <command>systemctl
1080                                 reboot -f</command>) and
1081                                 <option>reboot-immediate</option>
1082                                 causes immediate execution of the
1083                                 <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
1084                                 system call, which might result in
1085                                 data loss. Similar,
1086                                 <option>poweroff</option>,
1087                                 <option>poweroff-force</option>,
1088                                 <option>poweroff-immediate</option>
1089                                 have the effect of powering down the
1090                                 system with similar
1091                                 semantics. Defaults to
1092                                 <option>none</option>.</para></listitem>
1093                         </varlistentry>
1094
1095                         <varlistentry>
1096                                 <term><varname>FailureAction=</varname></term>
1097                                 <listitem><para>Configure the action
1098                                 to take when the service enters a failed
1099                                 state. Takes the same values as
1100                                 <varname>StartLimitAction=</varname>
1101                                 and executes the same actions.
1102                                 Defaults to <option>none</option>.
1103                                 </para></listitem>
1104                         </varlistentry>
1105
1106                         <varlistentry>
1107                                 <term><varname>RebootArgument=</varname></term>
1108                                 <listitem><para>Configure the optional
1109                                 argument for the
1110                                 <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
1111                                 system call if
1112                                 <varname>StartLimitAction=</varname>
1113                                 or <varname>FailureAction=</varname>
1114                                 is a reboot action. This works just
1115                                 like the optional argument to
1116                                 <command>systemctl reboot</command>
1117                                 command.</para></listitem>
1118                         </varlistentry>
1119
1120                 </variablelist>
1121
1122                 <para>Check
1123                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1124                 and
1125                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1126                 for more settings.</para>
1127
1128         </refsect1>
1129
1130         <refsect1>
1131                 <title>Command lines</title>
1132
1133                 <para>This section describes command line parsing and
1134                 variable and specifier substitions for
1135                 <varname>ExecStart=</varname>,
1136                 <varname>ExecStartPre=</varname>,
1137                 <varname>ExecStartPost=</varname>,
1138                 <varname>ExecReload=</varname>,
1139                 <varname>ExecStop=</varname>, and
1140                 <varname>ExecStopPost=</varname> options.</para>
1141
1142                 <para>Multiple command lines may be concatenated in a
1143                 single directive by separating them with semicolons
1144                 (these semicolons must be passed as separate words).
1145                 Lone semicolons may be escaped as
1146                 <literal>\;</literal>.</para>
1147
1148                 <para>Each command line is split on whitespace, with
1149                 the first item being the command to execute, and the
1150                 subsequent items being the arguments. Double quotes
1151                 ("...") and single quotes ('...') may be used, in
1152                 which case everything until the next matching quote
1153                 becomes part of the same argument. C-style escapes are
1154                 also supported, see table below. Quotes themselves are
1155                 removed after parsing and escape sequences
1156                 substituted. In addition, a trailing backslash
1157                 (<literal>\</literal>) may be used to merge lines.
1158                 </para>
1159
1160                 <para>This syntax is intended to be very similar to
1161                 shell syntax, but only the meta-characters and
1162                 expansions described in the following paragraphs are
1163                 understood.  Specifically, redirection using
1164                 <literal>&lt;</literal>, <literal>&lt;&lt;</literal>,
1165                 <literal>&gt;</literal>, and
1166                 <literal>&gt;&gt;</literal>, pipes using
1167                 <literal>|</literal>, running programs in the
1168                 background using <literal>&amp;</literal>, and
1169                 <emphasis>other elements of shell syntax are not
1170                 supported</emphasis>.</para>
1171
1172                 <para>The command to execute must an absolute path
1173                 name. It may contain spaces, but control characters
1174                 are not allowed.</para>
1175
1176                 <para>The command line accepts <literal>%</literal>
1177                 specifiers as described in
1178                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1179                 Note that the first argument of the command line
1180                 (i.e. the program to execute) may not include
1181                 specifiers.</para>
1182
1183                 <para>Basic environment variable substitution is
1184                 supported. Use <literal>${FOO}</literal> as part of a
1185                 word, or as a word of its own, on the command line, in
1186                 which case it will be replaced by the value of the
1187                 environment variable including all whitespace it
1188                 contains, resulting in a single argument. Use
1189                 <literal>$FOO</literal> as a separate word on the
1190                 command line, in which case it will be replaced by the
1191                 value of the environment variable split at whitespace
1192                 resulting in zero or more arguments. For this type of
1193                 expansion, quotes and respected when splitting into
1194                 words, and afterwards removed.</para>
1195
1196                 <para>Example:</para>
1197
1198                 <programlisting>Environment="ONE=one" 'TWO=two two'
1199 ExecStart=/bin/echo $ONE $TWO ${TWO}</programlisting>
1200
1201                 <para>This will execute <command>/bin/echo</command>
1202                 with four arguments: <literal>one</literal>,
1203                 <literal>two</literal>, <literal>two</literal>, and
1204                 <literal>two two</literal>.</para>
1205
1206                 <para>Example:</para>
1207                 <programlisting>Environment=ONE='one' "TWO='two two' too" THREE=
1208 ExecStart=/bin/echo ${ONE} ${TWO} ${THREE}
1209 ExecStart=/bin/echo $ONE $TWO $THREE</programlisting>
1210                 <para>This results in <filename>echo</filename> being
1211                 called twice, the first time with arguments
1212                 <literal>'one'</literal>,
1213                 <literal>'two two' too</literal>, <literal></literal>,
1214                 and the second time with arguments
1215                 <literal>one</literal>, <literal>two two</literal>,
1216                 <literal>too</literal>.
1217                 </para>
1218
1219                 <para>To pass a literal dollar sign, use
1220                 <literal>$$</literal>. Variables whose value is not
1221                 known at expansion time are treated as empty
1222                 strings. Note that the first argument (i.e. the
1223                 program to execute) may not be a variable.</para>
1224
1225                 <para>Variables to be used in this fashion may be
1226                 defined through <varname>Environment=</varname> and
1227                 <varname>EnvironmentFile=</varname>.  In addition,
1228                 variables listed in the section "Environment variables
1229                 in spawned processes" in
1230                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1231                 which are considered "static configuration", may be
1232                 used (this includes e.g. <varname>$USER</varname>, but
1233                 not <varname>$TERM</varname>).</para>
1234
1235                 <para>Note that shell command lines are not directly
1236                 supported. If shell command lines are to be used, they
1237                 need to be passed explicitly to a shell implementation
1238                 of some kind. Example:</para>
1239                 <programlisting>ExecStart=/bin/sh -c 'dmesg | tac'</programlisting>
1240
1241                 <para>Example:</para>
1242
1243                 <programlisting>ExecStart=/bin/echo one ; /bin/echo "two two"</programlisting>
1244
1245                 <para>This will execute <command>/bin/echo</command>
1246                 two times, each time with one argument:
1247                 <literal>one</literal> and <literal>two two</literal>,
1248                 respectively. Because two commands are specified,
1249                 <varname>Type=oneshot</varname> must be used.</para>
1250
1251                 <para>Example:</para>
1252
1253                 <programlisting>ExecStart=/bin/echo / &gt;/dev/null &amp; \; \
1254 /bin/ls</programlisting>
1255
1256                 <para>This will execute <command>/bin/echo</command>
1257                 with five arguments: <literal>/</literal>,
1258                 <literal>&gt;/dev/null</literal>,
1259                 <literal>&amp;</literal>, <literal>;</literal>, and
1260                 <literal>/bin/ls</literal>.</para>
1261
1262                 <table>
1263                         <title>C escapes supported in command lines and environment variables</title>
1264                         <tgroup cols='2'>
1265                                 <colspec colname='escape' />
1266                                 <colspec colname='meaning' />
1267                                 <thead>
1268                                         <row>
1269                                                 <entry>Literal</entry>
1270                                                 <entry>Actual value</entry>
1271                                         </row>
1272                                 </thead>
1273                                 <tbody>
1274                                         <row>
1275                                                 <entry><literal>\a</literal></entry>
1276                                                 <entry>bell</entry>
1277                                         </row>
1278                                         <row>
1279                                                 <entry><literal>\b</literal></entry>
1280                                                 <entry>backspace</entry>
1281                                         </row>
1282                                         <row>
1283                                                 <entry><literal>\f</literal></entry>
1284                                                 <entry>form feed</entry>
1285                                         </row>
1286                                         <row>
1287                                                 <entry><literal>\n</literal></entry>
1288                                                 <entry>newline</entry>
1289                                         </row>
1290                                         <row>
1291                                                 <entry><literal>\r</literal></entry>
1292                                                 <entry>carriage return</entry>
1293                                         </row>
1294                                         <row>
1295                                                 <entry><literal>\t</literal></entry>
1296                                                 <entry>tab</entry>
1297                                         </row>
1298                                         <row>
1299                                                 <entry><literal>\v</literal></entry>
1300                                                 <entry>vertical tab</entry>
1301                                         </row>
1302                                         <row>
1303                                                 <entry><literal>\\</literal></entry>
1304                                                 <entry>backslash</entry>
1305                                         </row>
1306                                         <row>
1307                                                 <entry><literal>\"</literal></entry>
1308                                                 <entry>double quotation mark</entry>
1309                                         </row>
1310                                         <row>
1311                                                 <entry><literal>\'</literal></entry>
1312                                                 <entry>single quotation mark</entry>
1313                                         </row>
1314                                         <row>
1315                                                 <entry><literal>\s</literal></entry>
1316                                                 <entry>space</entry>
1317                                         </row>
1318                                         <row>
1319                                                 <entry><literal>\x<replaceable>xx</replaceable></literal></entry>
1320                                                 <entry>character number <replaceable>xx</replaceable> in hexadecimal encoding</entry>
1321                                         </row>
1322                                         <row>
1323                                                 <entry><literal>\<replaceable>nnn</replaceable></literal></entry>
1324                                                 <entry>character number <replaceable>nnn</replaceable> in octal encoding</entry>
1325                                         </row>
1326                                 </tbody>
1327                         </tgroup>
1328                 </table>
1329         </refsect1>
1330
1331         <refsect1>
1332                   <title>See Also</title>
1333                   <para>
1334                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1335                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1336                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1337                           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1338                           <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1339                           <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1340                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1341                   </para>
1342         </refsect1>
1343
1344 </refentry>