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.
  15
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  18   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  19   Lesser General Public License for more details.
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  21   You should have received a copy of the GNU Lesser General Public License
  22   along with systemd; If not, see <http://www.gnu.org/licenses/>.
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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>, but its use
 305                                 is otherwise recommended if the process
 306                                 takes a name on the D-Bus bus.</para>
 307                                 </listitem>
 308                         </varlistentry>
 309
 310                         <varlistentry>
 311                                 <term><varname>BusPolicy=</varname></term>
 312
 313                                 <listitem><para>If specified, a custom
 314                                 <ulink url="https://code.google.com/p/d-bus/">kdbus</ulink>
 315                                 endpoint will be created and installed as the
 316                                 default bus node for the service. Such a custom
 317                                 endpoint can hold an own set of policy rules
 318                                 that are enforced on top of the bus-wide ones.
 319                                 The custom endpoint is named after the service
 320                                 it was created for, and its node will be
 321                                 bind-mounted over the default bus node
 322                                 location, so the service can only access the
 323                                 bus through its own endpoint. Note that custom
 324                                 bus endpoints default to a 'deny all' policy.
 325                                 Hence, if at least one
 326                                 <varname>BusPolicy=</varname> directive is
 327                                 given, you have to make sure to add explicit
 328                                 rules for everything the service should be able
 329                                 to do.</para>
 330                                 <para>The value of this directive is comprised
 331                                 of two parts; the bus name, and a verb to
 332                                 specify to granted access, which is one of
 333                                 <option>see</option>,
 334                                 <option>talk</option>, or
 335                                 <option>own</option>.
 336                                 <option>talk</option> implies
 337                                 <option>see</option>, and <option>own</option>
 338                                 implies both <option>talk</option> and
 339                                 <option>see</option>.
 340                                 If multiple access levels are specified for the
 341                                 same bus name, the most powerful one takes
 342                                 effect.
 343                                 </para>
 344                                 <para>Examples:</para>
 345                                 <programlisting>BusPolicy=org.freedesktop.systemd1 talk</programlisting>
 346                                 <programlisting>BusPolicy=org.foo.bar see</programlisting>
 347                                 <para>This option is only available on kdbus enabled systems.</para>
 348                                 </listitem>
 349                         </varlistentry>
 350
 351                         <varlistentry>
 352                                 <term><varname>ExecStart=</varname></term>
 353                                 <listitem><para>Commands with their
 354                                 arguments that are executed when this
 355                                 service is started. The value is split
 356                                 into zero or more command lines is
 357                                 according to the rules described below
 358                                 (see section "Command Lines" below).
 359                                 </para>
 360
 361                                 <para>When <varname>Type</varname> is
 362                                 not <option>oneshot</option>, only one
 363                                 command may and must be given. When
 364                                 <varname>Type=oneshot</varname> is
 365                                 used, zero or more commands may be
 366                                 specified. This can be specified by
 367                                 providing multiple command lines in
 368                                 the same directive, or alternatively,
 369                                 this directive may be specified more
 370                                 than once with the same effect. If the
 371                                 empty string is assigned to this
 372                                 option, the list of commands to start
 373                                 is reset, prior assignments of this
 374                                 option will have no effect. If no
 375                                 <varname>ExecStart=</varname> is
 376                                 specified, then the service must have
 377                                 <varname>RemainAfterExit=yes</varname>
 378                                 set.</para>
 379
 380                                 <para>For each of the specified
 381                                 commands, the first argument must be
 382                                 an absolute and literal path to an
 383                                 executable. Optionally, if the
 384                                 absolute file name is prefixed with
 385                                 <literal>@</literal>, the second token
 386                                 will be passed as
 387                                 <literal>argv[0]</literal> to the
 388                                 executed process, followed by the
 389                                 further arguments specified. If the
 390                                 absolute filename is prefixed with
 391                                 <literal>-</literal>, an exit code of
 392                                 the command normally considered a
 393                                 failure (i.e. non-zero exit status or
 394                                 abnormal exit due to signal) is
 395                                 ignored and considered success. If
 396                                 both <literal>-</literal> and
 397                                 <literal>@</literal> are used, they
 398                                 can appear in either order.</para>
 399
 400                                 <para>If more than one command is
 401                                 specified, the commands are invoked
 402                                 sequentially in the order they appear
 403                                 in the unit file. If one of the
 404                                 commands fails (and is not prefixed
 405                                 with <literal>-</literal>), other
 406                                 lines are not executed, and the unit
 407                                 is considered failed.</para>
 408
 409                                 <para>Unless
 410                                 <varname>Type=forking</varname> is
 411                                 set, the process started via this
 412                                 command line will be considered the
 413                                 main process of the daemon.</para>
 414
 415                               </listitem>
 416                         </varlistentry>
 417
 418                         <varlistentry>
 419                                 <term><varname>ExecStartPre=</varname></term>
 420                                 <term><varname>ExecStartPost=</varname></term>
 421                                 <listitem><para>Additional commands
 422                                 that are executed before or after
 423                                 the command in
 424                                 <varname>ExecStart=</varname>, respectively.
 425                                 Syntax is the same as for
 426                                 <varname>ExecStart=</varname>, except
 427                                 that multiple command lines are allowed
 428                                 and the commands are executed one
 429                                 after the other, serially.</para>
 430
 431                                 <para>If any of those commands (not
 432                                 prefixed with <literal>-</literal>)
 433                                 fail, the rest are not executed and
 434                                 the unit is considered failed.</para>
 435                                 </listitem>
 436                         </varlistentry>
 437
 438                         <varlistentry>
 439                                 <term><varname>ExecReload=</varname></term>
 440                                 <listitem><para>Commands to execute to
 441                                 trigger a configuration reload in the
 442                                 service. This argument takes multiple
 443                                 command lines, following the same
 444                                 scheme as described for
 445                                 <varname>ExecStart=</varname>
 446                                 above. Use of this setting is
 447                                 optional. Specifier and environment
 448                                 variable substitution is supported
 449                                 here following the same scheme as for
 450                                 <varname>ExecStart=</varname>.</para>
 451
 452                                 <para>One additional, special
 453                                 environment variable is set: if known,
 454                                 <varname>$MAINPID</varname> is set to
 455                                 the main process of the daemon, and
 456                                 may be used for command lines like the
 457                                 following:</para>
 458
 459                                 <programlisting>/bin/kill -HUP $MAINPID</programlisting>
 460
 461                                 <para>Note however that reloading a
 462                                 daemon by sending a signal (as with
 463                                 the example line above) is usually not
 464                                 a good choice, because this is an
 465                                 asynchronous operation and hence not
 466                                 suitable to order reloads of multiple
 467                                 services against each other. It is
 468                                 strongly recommended to set
 469                                 <varname>ExecReload=</varname> to a
 470                                 command that not only triggers a
 471                                 configuration reload of the daemon,
 472                                 but also synchronously waits for it to
 473                                 complete.</para>
 474                                 </listitem>
 475                         </varlistentry>
 476
 477                         <varlistentry>
 478                                 <term><varname>ExecStop=</varname></term>
 479                                 <listitem><para>Commands to execute to
 480                                 stop the service started via
 481                                 <varname>ExecStart=</varname>. This
 482                                 argument takes multiple command lines,
 483                                 following the same scheme as described
 484                                 for <varname>ExecStart=</varname>
 485                                 above. Use of this setting is
 486                                 optional. After the commands configured
 487                                 in this option are run, all processes
 488                                 remaining for a service are
 489                                 terminated according to the
 490                                 <varname>KillMode=</varname> setting
 491                                 (see
 492                                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>). If
 493                                 this option is not specified, the
 494                                 process is terminated immediately when
 495                                 service stop is requested. Specifier
 496                                 and environment variable substitution
 497                                 is supported (including
 498                                 <varname>$MAINPID</varname>, see
 499                                 above).</para></listitem>
 500                         </varlistentry>
 501
 502                         <varlistentry>
 503                                 <term><varname>ExecStopPost=</varname></term>
 504                                 <listitem><para>Additional commands
 505                                 that are executed after the service
 506                                 was stopped. This includes cases where
 507                                 the commands configured in
 508                                 <varname>ExecStop=</varname> were used,
 509                                 where the service does not have any
 510                                 <varname>ExecStop=</varname> defined, or
 511                                 where the service exited unexpectedly. This
 512                                 argument takes multiple command lines,
 513                                 following the same scheme as described
 514                                 for <varname>ExecStart</varname>. Use
 515                                 of these settings is
 516                                 optional. Specifier and environment
 517                                 variable substitution is
 518                                 supported.</para></listitem>
 519                         </varlistentry>
 520
 521                         <varlistentry>
 522                                 <term><varname>RestartSec=</varname></term>
 523                                 <listitem><para>Configures the time to
 524                                 sleep before restarting a service (as
 525                                 configured with
 526                                 <varname>Restart=</varname>). Takes a
 527                                 unit-less value in seconds, or a time
 528                                 span value such as "5min
 529                                 20s". Defaults to
 530                                 100ms.</para></listitem>
 531                         </varlistentry>
 532
 533                         <varlistentry>
 534                                 <term><varname>TimeoutStartSec=</varname></term>
 535                                 <listitem><para>Configures the time to
 536                                 wait for start-up. If a
 537                                 daemon service does not signal
 538                                 start-up completion within the
 539                                 configured time, the service will be
 540                                 considered failed and will be shut
 541                                 down again.
 542                                 Takes a unit-less value in seconds, or a
 543                                 time span value such as "5min
 544                                 20s". Pass <literal>0</literal> to
 545                                 disable the timeout logic. Defaults to
 546                                 <varname>DefaultTimeoutStartSec=</varname> from
 547                                 the manager configuration file, except
 548                                 when <varname>Type=oneshot</varname> is
 549                                 used, in which case the timeout
 550                                 is disabled by default
 551                                 (see <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
 552                                 </para></listitem>
 553                         </varlistentry>
 554
 555                         <varlistentry>
 556                                 <term><varname>TimeoutStopSec=</varname></term>
 557                                 <listitem><para>Configures the time to
 558                                 wait for stop. If a service is asked
 559                                 to stop, but does not terminate in the
 560                                 specified time, it will be terminated
 561                                 forcibly via <constant>SIGTERM</constant>,
 562                                 and after another timeout of equal duration
 563                                 with <constant>SIGKILL</constant> (see
 564                                 <varname>KillMode=</varname>
 565                                 in <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
 566                                 Takes a unit-less value in seconds, or a
 567                                 time span value such as "5min
 568                                 20s". Pass <literal>0</literal> to disable
 569                                 the timeout logic. Defaults to
 570                                 <varname>DefaultTimeoutStopSec=</varname> from the
 571                                 manager configuration file
 572                                 (see <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
 573                                 </para></listitem>
 574                         </varlistentry>
 575
 576                         <varlistentry>
 577                                 <term><varname>TimeoutSec=</varname></term>
 578                                 <listitem><para>A shorthand for configuring
 579                                 both <varname>TimeoutStartSec=</varname>
 580                                 and <varname>TimeoutStopSec=</varname>
 581                                 to the specified value.
 582                                 </para></listitem>
 583                         </varlistentry>
 584
 585                         <varlistentry>
 586                                 <term><varname>WatchdogSec=</varname></term>
 587                                 <listitem><para>Configures the
 588                                 watchdog timeout for a service. The
 589                                 watchdog is activated when the start-up is
 590                                 completed. The service must call
 591                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 592                                 regularly with <literal>WATCHDOG=1</literal>
 593                                 (i.e. the "keep-alive ping"). If the time
 594                                 between two such calls is larger than
 595                                 the configured time, then the service
 596                                 is placed in a failed state. By
 597                                 setting <varname>Restart=</varname> to
 598                                 <option>on-failure</option> or
 599                                 <option>always</option>, the service
 600                                 will be automatically restarted. The
 601                                 time configured here will be passed to
 602                                 the executed service process in the
 603                                 <varname>WATCHDOG_USEC=</varname>
 604                                 environment variable. This allows
 605                                 daemons to automatically enable the
 606                                 keep-alive pinging logic if watchdog
 607                                 support is enabled for the service. If
 608                                 this option is used,
 609                                 <varname>NotifyAccess=</varname> (see
 610                                 below) should be set to open access to
 611                                 the notification socket provided by
 612                                 systemd. If
 613                                 <varname>NotifyAccess=</varname> is
 614                                 not set, it will be implicitly set to
 615                                 <option>main</option>. Defaults to 0,
 616                                 which disables this
 617                                 feature.</para></listitem>
 618                         </varlistentry>
 619
 620                         <varlistentry>
 621                                 <term><varname>Restart=</varname></term>
 622                                 <listitem><para>Configures whether the
 623                                 service shall be restarted when the
 624                                 service process exits, is killed,
 625                                 or a timeout is reached. The service
 626                                 process may be the main service
 627                                 process, but it may also be one of the
 628                                 processes specified with
 629                                 <varname>ExecStartPre=</varname>,
 630                                 <varname>ExecStartPost=</varname>,
 631                                 <varname>ExecStop=</varname>,
 632                                 <varname>ExecStopPost=</varname>, or
 633                                 <varname>ExecReload=</varname>.
 634                                 When the death of the process is a
 635                                 result of systemd operation (e.g. service
 636                                 stop or restart), the service will not be
 637                                 restarted. Timeouts include missing
 638                                 the watchdog "keep-alive ping"
 639                                 deadline and a service start, reload,
 640                                 and stop operation timeouts.</para>
 641
 642                                 <para>Takes one of
 643                                 <option>no</option>,
 644                                 <option>on-success</option>,
 645                                 <option>on-failure</option>,
 646                                 <option>on-abnormal</option>,
 647                                 <option>on-watchdog</option>,
 648                                 <option>on-abort</option>, or
 649                                 <option>always</option>. If set to
 650                                 <option>no</option> (the default), the
 651                                 service will not be restarted. If set
 652                                 to <option>on-success</option>, it
 653                                 will be restarted only when the
 654                                 service process exits cleanly.  In
 655                                 this context, a clean exit means an
 656                                 exit code of 0, or one of the signals
 657                                 <constant>SIGHUP</constant>,
 658                                 <constant>SIGINT</constant>,
 659                                 <constant>SIGTERM</constant> or
 660                                 <constant>SIGPIPE</constant>, and
 661                                 additionally, exit statuses and
 662                                 signals specified in
 663                                 <varname>SuccessExitStatus=</varname>.
 664                                 If set to <option>on-failure</option>,
 665                                 the service will be restarted when the
 666                                 process exits with a non-zero exit
 667                                 code, is terminated by a signal
 668                                 (including on core dump, but excluding
 669                                 the aforementiond four signals), when
 670                                 an operation (such as service reload)
 671                                 times out, and when the configured
 672                                 watchdog timeout is triggered.  If set
 673                                 to <option>on-abnormal</option>, the
 674                                 service will be restarted when the
 675                                 process is terminated by a signal
 676                                 (including on core dump, excluding the
 677                                 aforementioned four signals), when an
 678                                 operation times out, or when the
 679                                 watchdog timeout is triggered. If set
 680                                 to <option>on-abort</option>, the
 681                                 service will be restarted only if the
 682                                 service process exits due to an
 683                                 uncaught signal not specified as a
 684                                 clean exit status.  If set to
 685                                 <option>on-watchdog</option>, the
 686                                 service will be restarted only if the
 687                                 watchdog timeout for the service
 688                                 expires.  If set to
 689                                 <option>always</option>, the service
 690                                 will be restarted regardless of
 691                                 whether it exited cleanly or not, got
 692                                 terminated abnormally by a signal, or
 693                                 hit a timeout.</para>
 694
 695                                 <table>
 696                                         <title>Exit causes and the effect of the <varname>Restart=</varname> settings on them</title>
 697
 698                                         <tgroup cols='2'>
 699                                                 <colspec colname='path' />
 700                                                 <colspec colname='expl' />
 701                                                 <thead>
 702                                                         <row>
 703                                                                 <entry>Restart settings/Exit causes</entry>
 704                                                                 <entry><option>no</option></entry>
 705                                                                 <entry><option>always</option></entry>
 706                                                                 <entry><option>on-success</option></entry>
 707                                                                 <entry><option>on-failure</option></entry>
 708                                                                 <entry><option>on-abnormal</option></entry>
 709                                                                 <entry><option>on-abort</option></entry>
 710                                                                 <entry><option>on-watchdog</option></entry>
 711                                                         </row>
 712                                                 </thead>
 713                                                 <tbody>
 714                                                         <row>
 715                                                                 <entry>Clean exit code or signal</entry>
 716                                                                 <entry/>
 717                                                                 <entry>X</entry>
 718                                                                 <entry>X</entry>
 719                                                                 <entry/>
 720                                                                 <entry/>
 721                                                                 <entry/>
 722                                                                 <entry/>
 723                                                         </row>
 724                                                         <row>
 725                                                                 <entry>Unclean exit code</entry>
 726                                                                 <entry/>
 727                                                                 <entry>X</entry>
 728                                                                 <entry/>
 729                                                                 <entry>X</entry>
 730                                                                 <entry/>
 731                                                                 <entry/>
 732                                                                 <entry/>
 733                                                         </row>
 734                                                         <row>
 735                                                                 <entry>Unclean signal</entry>
 736                                                                 <entry/>
 737                                                                 <entry>X</entry>
 738                                                                 <entry/>
 739                                                                 <entry>X</entry>
 740                                                                 <entry>X</entry>
 741                                                                 <entry>X</entry>
 742                                                                 <entry/>
 743                                                         </row>
 744                                                         <row>
 745                                                                 <entry>Timeout</entry>
 746                                                                 <entry/>
 747                                                                 <entry>X</entry>
 748                                                                 <entry/>
 749                                                                 <entry>X</entry>
 750                                                                 <entry>X</entry>
 751                                                                 <entry/>
 752                                                                 <entry/>
 753                                                         </row>
 754                                                         <row>
 755                                                                 <entry>Watchdog</entry>
 756                                                                 <entry/>
 757                                                                 <entry>X</entry>
 758                                                                 <entry/>
 759                                                                 <entry>X</entry>
 760                                                                 <entry>X</entry>
 761                                                                 <entry/>
 762                                                                 <entry>X</entry>
 763                                                         </row>
 764                                                 </tbody>
 765                                         </tgroup>
 766                                 </table>
 767
 768                                 <para>As exceptions to the setting
 769                                 above the service will not be
 770                                 restarted if the exit code or signal
 771                                 is specified in
 772                                 <varname>RestartPreventExitStatus=</varname>
 773                                 (see below). Also, the services will
 774                                 always be restarted if the exit code
 775                                 or signal is specified in
 776                                 <varname>RestartForceExitStatus=</varname>
 777                                 (see below).</para>
 778
 779                                 <para>Setting this to
 780                                 <option>on-failure</option> is the
 781                                 recommended choice for long-running
 782                                 services, in order to increase
 783                                 reliability by attempting automatic
 784                                 recovery from errors. For services
 785                                 that shall be able to terminate on
 786                                 their own choice (and avoid
 787                                 immediate restarting),
 788                                 <option>on-abnormal</option> is an
 789                                 alternative choice.</para>
 790                                 </listitem>
 791                         </varlistentry>
 792
 793                         <varlistentry>
 794                                 <term><varname>SuccessExitStatus=</varname></term>
 795                                 <listitem><para>Takes a list of exit
 796                                 status definitions that when returned
 797                                 by the main service process will be
 798                                 considered successful termination, in
 799                                 addition to the normal successful exit
 800                                 code 0 and the signals <constant>SIGHUP</constant>, <constant>SIGINT</constant>,
 801                                 <constant>SIGTERM</constant>, and <constant>SIGPIPE</constant>. Exit status
 802                                 definitions can either be numeric exit
 803                                 codes or termination signal names,
 804                                 separated by spaces. For example:
 805                                 <programlisting>SuccessExitStatus=1 2 8 SIGKILL</programlisting>
 806                                 ensures that exit codes 1, 2, 8 and
 807                                 the termination signal
 808                                 <constant>SIGKILL</constant> are
 809                                 considered clean service terminations.
 810                                 </para>
 811
 812                                 <para>Note that if a process has a
 813                                 signal handler installed and exits by
 814                                 calling
 815                                 <citerefentry><refentrytitle>_exit</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 816                                 in response to a signal, the
 817                                 information about the signal is lost.
 818                                 Programs should instead perform cleanup and kill themselves with the same signal instead. See
 819                                 <ulink url="http://www.cons.org/cracauer/sigint.html">Proper handling of SIGINT/SIGQUIT — How to be a proper program</ulink>.</para>
 820
 821                                 <para>This option may appear more than once,
 822                                 in which case the list of successful
 823                                 exit statuses is merged. If the empty
 824                                 string is assigned to this option, the
 825                                 list is reset, all prior assignments
 826                                 of this option will have no
 827                                 effect.</para></listitem>
 828                         </varlistentry>
 829
 830                         <varlistentry>
 831                                 <term><varname>RestartPreventExitStatus=</varname></term>
 832                                 <listitem><para>Takes a list of exit
 833                                 status definitions that when returned
 834                                 by the main service process will
 835                                 prevent automatic service restarts,
 836                                 regardless of the restart setting
 837                                 configured with
 838                                 <varname>Restart=</varname>. Exit
 839                                 status definitions can either be
 840                                 numeric exit codes or termination
 841                                 signal names, and are separated by
 842                                 spaces. Defaults to the empty list, so
 843                                 that, by default, no exit status is
 844                                 excluded from the configured restart
 845                                 logic. For example:
 846                                 <programlisting>RestartPreventExitStatus=1 6 SIGABRT</programlisting> ensures that exit
 847                                 codes 1 and 6 and the termination
 848                                 signal <constant>SIGABRT</constant> will
 849                                 not result in automatic service
 850                                 restarting. This
 851                                 option may appear more than once, in
 852                                 which case the list of restart-preventing
 853                                 statuses is merged. If the empty
 854                                 string is assigned to this option, the
 855                                 list is reset and all prior assignments
 856                                 of this option will have no
 857                                 effect.</para></listitem>
 858                         </varlistentry>
 859
 860                         <varlistentry>
 861                                 <term><varname>RestartForceExitStatus=</varname></term>
 862                                 <listitem><para>Takes a list of exit
 863                                 status definitions that when returned
 864                                 by the main service process will force
 865                                 automatic service restarts, regardless
 866                                 of the restart setting configured with
 867                                 <varname>Restart=</varname>. The
 868                                 argument format is similar to
 869                                 <varname>RestartPreventExitStatus=</varname>.</para></listitem>
 870                         </varlistentry>
 871
 872                         <varlistentry>
 873                                 <term><varname>PermissionsStartOnly=</varname></term>
 874                                 <listitem><para>Takes a boolean
 875                                 argument. If true, the permission-related
 876                                 execution options, as
 877                                 configured with
 878                                 <varname>User=</varname> and similar
 879                                 options (see
 880                                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 881                                 for more information), are only applied
 882                                 to the process started with
 883                                 <varname>ExecStart=</varname>, and not
 884                                 to the various other
 885                                 <varname>ExecStartPre=</varname>,
 886                                 <varname>ExecStartPost=</varname>,
 887                                 <varname>ExecReload=</varname>,
 888                                 <varname>ExecStop=</varname>, and
 889                                 <varname>ExecStopPost=</varname>
 890                                 commands. If false, the setting is
 891                                 applied to all configured commands the
 892                                 same way. Defaults to
 893                                 false.</para></listitem>
 894                         </varlistentry>
 895
 896                         <varlistentry>
 897                                 <term><varname>RootDirectoryStartOnly=</varname></term>
 898                                 <listitem><para>Takes a boolean
 899                                 argument. If true, the root directory,
 900                                 as configured with the
 901                                 <varname>RootDirectory=</varname>
 902                                 option (see
 903                                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 904                                 for more information), is only applied
 905                                 to the process started with
 906                                 <varname>ExecStart=</varname>, and not
 907                                 to the various other
 908                                 <varname>ExecStartPre=</varname>,
 909                                 <varname>ExecStartPost=</varname>,
 910                                 <varname>ExecReload=</varname>,
 911                                 <varname>ExecStop=</varname>, and
 912                                 <varname>ExecStopPost=</varname>
 913                                 commands. If false, the setting is
 914                                 applied to all configured commands the
 915                                 same way. Defaults to
 916                                 false.</para></listitem>
 917                         </varlistentry>
 918
 919                         <varlistentry>
 920                                 <term><varname>NonBlocking=</varname></term>
 921                                 <listitem><para>Set the
 922                                 <constant>O_NONBLOCK</constant> flag
 923                                 for all file descriptors passed via
 924                                 socket-based activation. If true, all
 925                                 file descriptors >= 3 (i.e. all except
 926                                 stdin, stdout, and stderr) will have
 927                                 the <constant>O_NONBLOCK</constant> flag
 928                                 set and hence are in
 929                                 non-blocking mode. This option is only
 930                                 useful in conjunction with a socket
 931                                 unit, as described in
 932                                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Defaults
 933                                 to false.</para></listitem>
 934                         </varlistentry>
 935
 936                         <varlistentry>
 937                                 <term><varname>NotifyAccess=</varname></term>
 938                                 <listitem><para>Controls access to the
 939                                 service status notification socket, as
 940                                 accessible via the
 941                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 942                                 call. Takes one of
 943                                 <option>none</option> (the default),
 944                                 <option>main</option> or
 945                                 <option>all</option>. If
 946                                 <option>none</option>, no daemon status
 947                                 updates are accepted from the service
 948                                 processes, all status update messages
 949                                 are ignored. If <option>main</option>,
 950                                 only service updates sent from the
 951                                 main process of the service are
 952                                 accepted. If <option>all</option>, all
 953                                 services updates from all members of
 954                                 the service's control group are
 955                                 accepted. This option should be set to
 956                                 open access to the notification socket
 957                                 when using
 958                                 <varname>Type=notify</varname> or
 959                                 <varname>WatchdogSec=</varname> (see
 960                                 above). If those options are used but
 961                                 <varname>NotifyAccess=</varname> is not
 962                                 configured, it will be implicitly set
 963                                 to
 964                                 <option>main</option>.</para></listitem>
 965                         </varlistentry>
 966
 967                         <varlistentry>
 968                                 <term><varname>Sockets=</varname></term>
 969                                 <listitem><para>Specifies the name of
 970                                 the socket units this service shall
 971                                 inherit socket file descriptors
 972                                 from when the service is
 973                                 started. Normally it should not be
 974                                 necessary to use this setting as all
 975                                 socket file descriptors whose unit
 976                                 shares the same name as the service
 977                                 (subject to the different unit name
 978                                 suffix of course) are passed to the
 979                                 spawned process.</para>
 980
 981                                 <para>Note that the same socket file
 982                                 descriptors may be passed to multiple
 983                                 processes simultaneously. Also note
 984                                 that a different service may be
 985                                 activated on incoming socket traffic
 986                                 than the one which is ultimately
 987                                 configured to inherit the socket file
 988                                 descriptors. Or in other words: the
 989                                 <varname>Service=</varname> setting of
 990                                 <filename>.socket</filename> units
 991                                 does not have to match the inverse of
 992                                 the <varname>Sockets=</varname>
 993                                 setting of the
 994                                 <filename>.service</filename> it
 995                                 refers to.</para>
 996
 997                                 <para>This option may appear more than
 998                                 once, in which case the list of socket
 999                                 units is merged. If the empty string
1000                                 is assigned to this option, the list of
1001                                 sockets is reset, and all prior uses of
1002                                 this setting will have no
1003                                 effect.</para></listitem>
1004                         </varlistentry>
1005
1006                         <varlistentry>
1007                                 <term><varname>StartLimitInterval=</varname></term>
1008                                 <term><varname>StartLimitBurst=</varname></term>
1009
1010                                 <listitem><para>Configure service
1011                                 start rate limiting. By default,
1012                                 services which are started more
1013                                 than 5 times within 10 seconds are not
1014                                 permitted to start any more times
1015                                 until the 10 second interval ends. With
1016                                 these two options, this rate limiting
1017                                 may be modified. Use
1018                                 <varname>StartLimitInterval=</varname>
1019                                 to configure the checking interval (defaults to
1020                                 <varname>DefaultStartLimitInterval=</varname> in
1021                                 manager configuration file, set to 0 to disable
1022                                 any kind of rate limiting). Use
1023                                 <varname>StartLimitBurst=</varname> to
1024                                 configure how many starts per interval
1025                                 are allowed (defaults to
1026                                 <varname>DefaultStartLimitBurst=</varname> in
1027                                 manager configuration file). These
1028                                 configuration options are particularly
1029                                 useful in conjunction with
1030                                 <varname>Restart=</varname>; however,
1031                                 they apply to all kinds of starts
1032                                 (including manual), not just those
1033                                 triggered by the
1034                                 <varname>Restart=</varname> logic.
1035                                 Note that units which are configured
1036                                 for <varname>Restart=</varname> and
1037                                 which reach the start limit are not
1038                                 attempted to be restarted anymore;
1039                                 however, they may still be restarted
1040                                 manually at a later point, from which
1041                                 point on, the restart logic is again
1042                                 activated. Note that
1043                                 <command>systemctl
1044                                 reset-failed</command> will cause the
1045                                 restart rate counter for a service to
1046                                 be flushed, which is useful if the
1047                                 administrator wants to manually start
1048                                 a service and the start limit
1049                                 interferes with
1050                                 that.</para></listitem>
1051                         </varlistentry>
1052
1053                         <varlistentry>
1054                                 <term><varname>StartLimitAction=</varname></term>
1055
1056                                 <listitem><para>Configure the action
1057                                 to take if the rate limit configured
1058                                 with
1059                                 <varname>StartLimitInterval=</varname>
1060                                 and
1061                                 <varname>StartLimitBurst=</varname> is
1062                                 hit. Takes one of
1063                                 <option>none</option>,
1064                                 <option>reboot</option>,
1065                                 <option>reboot-force</option>,
1066                                 <option>reboot-immediate</option>,
1067                                 <option>poweroff</option>,
1068                                 <option>poweroff-force</option> or
1069                                 <option>poweroff-immediate</option>. If
1070                                 <option>none</option> is set, hitting
1071                                 the rate limit will trigger no action
1072                                 besides that the start will not be
1073                                 permitted. <option>reboot</option>
1074                                 causes a reboot following the normal
1075                                 shutdown procedure (i.e. equivalent to
1076                                 <command>systemctl reboot</command>).
1077                                 <option>reboot-force</option> causes a
1078                                 forced reboot which will terminate all
1079                                 processes forcibly but should cause no
1080                                 dirty file systems on reboot
1081                                 (i.e. equivalent to <command>systemctl
1082                                 reboot -f</command>) and
1083                                 <option>reboot-immediate</option>
1084                                 causes immediate execution of the
1085                                 <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
1086                                 system call, which might result in
1087                                 data loss. Similar,
1088                                 <option>poweroff</option>,
1089                                 <option>poweroff-force</option>,
1090                                 <option>poweroff-immediate</option>
1091                                 have the effect of powering down the
1092                                 system with similar
1093                                 semantics. Defaults to
1094                                 <option>none</option>.</para></listitem>
1095                         </varlistentry>
1096
1097                         <varlistentry>
1098                                 <term><varname>FailureAction=</varname></term>
1099                                 <listitem><para>Configure the action
1100                                 to take when the service enters a failed
1101                                 state. Takes the same values as
1102                                 <varname>StartLimitAction=</varname>
1103                                 and executes the same actions.
1104                                 Defaults to <option>none</option>.
1105                                 </para></listitem>
1106                         </varlistentry>
1107
1108                         <varlistentry>
1109                                 <term><varname>RebootArgument=</varname></term>
1110                                 <listitem><para>Configure the optional
1111                                 argument for the
1112                                 <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
1113                                 system call if
1114                                 <varname>StartLimitAction=</varname>
1115                                 or <varname>FailureAction=</varname>
1116                                 is a reboot action. This works just
1117                                 like the optional argument to
1118                                 <command>systemctl reboot</command>
1119                                 command.</para></listitem>
1120                         </varlistentry>
1121
1122                 </variablelist>
1123
1124                 <para>Check
1125                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1126                 and
1127                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1128                 for more settings.</para>
1129
1130         </refsect1>
1131
1132         <refsect1>
1133                 <title>Compatibility Options</title>
1134
1135                 <para>The following options are also available in the
1136                 <literal>[Service]</literal> section, but exist purely
1137                 for compatibility reasons and should not be used in
1138                 newly written service files.</para>
1139
1140                 <variablelist class='unit-directives'>
1141                         <varlistentry>
1142                                 <term><varname>SysVStartPriority=</varname></term>
1143                                 <listitem><para>Set the SysV start
1144                                 priority to use to order this service
1145                                 in relation to SysV services lacking
1146                                 LSB headers. This option is only
1147                                 necessary to fix ordering in relation
1148                                 to legacy SysV services that have no
1149                                 ordering information encoded in the
1150                                 script headers. As such, it should only
1151                                 be used as a temporary compatibility
1152                                 option and should not be used in new unit
1153                                 files. Almost always, it is a better
1154                                 choice to add explicit ordering
1155                                 directives via
1156                                 <varname>After=</varname> or
1157                                 <varname>Before=</varname>,
1158                                 instead. For more details, see
1159                                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1160                                 If used, pass an integer value in the
1161                                 range 0-99.</para></listitem>
1162                         </varlistentry>
1163                 </variablelist>
1164         </refsect1>
1165
1166         <refsect1>
1167                 <title>Command lines</title>
1168
1169                 <para>This section describes command line parsing and
1170                 variable and specifier substitions for
1171                 <varname>ExecStart=</varname>,
1172                 <varname>ExecStartPre=</varname>,
1173                 <varname>ExecStartPost=</varname>,
1174                 <varname>ExecReload=</varname>,
1175                 <varname>ExecStop=</varname>, and
1176                 <varname>ExecStopPost=</varname> options.</para>
1177
1178                 <para>Multiple command lines may be concatenated in a
1179                 single directive by separating them with semicolons
1180                 (these semicolons must be passed as separate words).
1181                 Lone semicolons may be escaped as
1182                 <literal>\;</literal>.</para>
1183
1184                 <para>Each command line is split on whitespace, with
1185                 the first item being the command to execute, and the
1186                 subsequent items being the arguments.  Double quotes
1187                 ("...") and single quotes ('...') may be used, in
1188                 which case everything until the next matching quote
1189                 becomes part of the same argument. Quotes themselves
1190                 are removed after parsing. In addition, a trailing
1191                 backslash (<literal>\</literal>) may be used to merge
1192                 lines. </para>
1193
1194                 <para>This syntax is intended to be very similar to
1195                 shell syntax, but only the meta-characters and
1196                 expansions described in the following paragraphs are
1197                 understood.  Specifically, redirection using
1198                 <literal>&lt;</literal>, <literal>&lt;&lt;</literal>,
1199                 <literal>&gt;</literal>, and
1200                 <literal>&gt;&gt;</literal>, pipes using
1201                 <literal>|</literal>, running programs in the
1202                 background using <literal>&amp;</literal>, and
1203                 <emphasis>other elements of shell syntax are not
1204                 supported</emphasis>.</para>
1205
1206                 <para>The command line accepts <literal>%</literal>
1207                 specifiers as described in
1208                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1209                 Note that the first argument of the command line
1210                 (i.e. the program to execute) may not include
1211                 specifiers.</para>
1212
1213                 <para>Basic environment variable substitution is
1214                 supported. Use <literal>${FOO}</literal> as part of a
1215                 word, or as a word of its own, on the command line, in
1216                 which case it will be replaced by the value of the
1217                 environment variable including all whitespace it
1218                 contains, resulting in a single argument. Use
1219                 <literal>$FOO</literal> as a separate word on the
1220                 command line, in which case it will be replaced by the
1221                 value of the environment variable split at whitespace
1222                 resulting in zero or more arguments. For this type of
1223                 expansion, quotes and respected when splitting into
1224                 words, and afterwards removed.</para>
1225
1226                 <para>Example:</para>
1227
1228                 <programlisting>Environment="ONE=one" 'TWO=two two'
1229 ExecStart=/bin/echo $ONE $TWO ${TWO}</programlisting>
1230
1231                 <para>This will execute <command>/bin/echo</command>
1232                 with four arguments: <literal>one</literal>,
1233                 <literal>two</literal>, <literal>two</literal>, and
1234                 <literal>two two</literal>.</para>
1235
1236                 <para>Example:</para>
1237                 <programlisting>Environment=ONE='one' "TWO='two two' too" THREE=
1238 ExecStart=/bin/echo ${ONE} ${TWO} ${THREE}
1239 ExecStart=/bin/echo $ONE $TWO $THREE</programlisting>
1240                 <para>This results in <filename>echo</filename> being
1241                 called twice, the first time with arguments
1242                 <literal>'one'</literal>,
1243                 <literal>'two two' too</literal>, <literal></literal>,
1244                 and the second time with arguments
1245                 <literal>one</literal>, <literal>two two</literal>,
1246                 <literal>too</literal>.
1247                 </para>
1248
1249                 <para>To pass a literal dollar sign, use
1250                 <literal>$$</literal>. Variables whose value is not
1251                 known at expansion time are treated as empty
1252                 strings. Note that the first argument (i.e. the
1253                 program to execute) may not be a variable.</para>
1254
1255                 <para>Variables to be used in this fashion may be
1256                 defined through <varname>Environment=</varname> and
1257                 <varname>EnvironmentFile=</varname>.  In addition,
1258                 variables listed in the section "Environment variables
1259                 in spawned processes" in
1260                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1261                 which are considered "static configuration", may be
1262                 used (this includes e.g. <varname>$USER</varname>, but
1263                 not <varname>$TERM</varname>).</para>
1264
1265                 <para>Note that shell command lines are not directly
1266                 supported. If shell command lines are to be used, they
1267                 need to be passed explicitly to a shell implementation
1268                 of some kind. Example:</para>
1269                 <programlisting>ExecStart=/bin/sh -c 'dmesg | tac'</programlisting>
1270
1271                 <para>Example:</para>
1272
1273                 <programlisting>ExecStart=/bin/echo one ; /bin/echo "two two"</programlisting>
1274
1275                 <para>This will execute <command>/bin/echo</command>
1276                 two times, each time with one argument:
1277                 <literal>one</literal> and <literal>two two</literal>,
1278                 respectively. Because two commands are specified,
1279                 <varname>Type=oneshot</varname> must be used.</para>
1280
1281                 <para>Example:</para>
1282
1283                 <programlisting>ExecStart=/bin/echo / &gt;/dev/null &amp; \; \
1284 /bin/ls</programlisting>
1285
1286                 <para>This will execute <command>/bin/echo</command>
1287                 with five arguments: <literal>/</literal>,
1288                 <literal>&gt;/dev/null</literal>,
1289                 <literal>&amp;</literal>, <literal>;</literal>, and
1290                 <literal>/bin/ls</literal>.</para>
1291         </refsect1>
1292
1293         <refsect1>
1294                   <title>See Also</title>
1295                   <para>
1296                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1297                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1298                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1299                           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1300                           <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1301                           <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1302                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1303                   </para>
1304         </refsect1>
1305
1306 </refentry>