man/systemctl.xml

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   8 Copyright 2010 Lennart Poettering
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  23
  24 <refentry id="systemctl">
  25
  26   <refentryinfo>
  27     <title>systemctl</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>systemctl</refentrytitle>
  42     <manvolnum>1</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>systemctl</refname>
  47     <refpurpose>Control the systemd system and service manager</refpurpose>
  48   </refnamediv>
  49
  50   <refsynopsisdiv>
  51     <cmdsynopsis>
  52       <command>systemctl</command>
  53       <arg choice="opt" rep="repeat">OPTIONS</arg>
  54       <arg choice="plain">COMMAND</arg>
  55       <arg choice="opt" rep="repeat">NAME</arg>
  56     </cmdsynopsis>
  57   </refsynopsisdiv>
  58
  59   <refsect1>
  60     <title>Description</title>
  61
  62     <para><command>systemctl</command> may be used to
  63     introspect and control the state of the
  64     <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  65     system and service manager.</para>
  66   </refsect1>
  67
  68   <refsect1>
  69     <title>Options</title>
  70
  71     <para>The following options are understood:</para>
  72
  73     <variablelist>
  74       <varlistentry>
  75         <term><option>-h</option></term>
  76         <term><option>--help</option></term>
  77
  78         <listitem><para>Prints a short help
  79         text and exits.</para></listitem>
  80       </varlistentry>
  81
  82       <varlistentry>
  83         <term><option>--version</option></term>
  84
  85         <listitem>
  86           <para>Prints a short version string and exits.</para>
  87         </listitem>
  88       </varlistentry>
  89
  90       <varlistentry>
  91         <term><option>-t</option></term>
  92         <term><option>--type=</option></term>
  93
  94         <listitem>
  95           <para>The argument should be a comma-separated list of unit
  96           types such as <option>service</option> and
  97           <option>socket</option>.
  98           </para>
  99
 100           <para>If one of the arguments is a unit type, when listing
 101           units, limit display to certain unit types. Otherwise, units
 102           of all types will be shown.</para>
 103
 104           <para>As a special case, if one of the arguments is
 105           <option>help</option>, a list of allowed values will be
 106           printed and the program will exit.</para>
 107         </listitem>
 108       </varlistentry>
 109
 110       <varlistentry>
 111         <term><option>--state=</option></term>
 112
 113         <listitem>
 114         <para>The argument should be a comma-separated list of unit LOAD,
 115         SUB, or ACTIVE states. When listing units, show only those
 116         in specified states.</para>
 117         </listitem>
 118       </varlistentry>
 119
 120       <varlistentry>
 121         <term><option>-p</option></term>
 122         <term><option>--property=</option></term>
 123
 124         <listitem>
 125           <para>When showing unit/job/manager properties with the
 126           <command>show</command> command, limit display to certain
 127           properties as specified as argument. If not specified, all
 128           set properties are shown. The argument should be a
 129           comma-separated list of property names, such as
 130           <literal>MainPID</literal>. If specified more than once, all
 131           properties with the specified names are shown.</para>
 132         </listitem>
 133       </varlistentry>
 134
 135       <varlistentry>
 136         <term><option>-a</option></term>
 137         <term><option>--all</option></term>
 138
 139         <listitem>
 140           <para>When listing units, show all loaded units, regardless
 141           of their state, including inactive units. When showing
 142           unit/job/manager properties, show all properties regardless
 143           whether they are set or not.</para>
 144           <para>To list all units installed on the system, use the
 145           <command>list-unit-files</command> command instead.</para>
 146         </listitem>
 147       </varlistentry>
 148
 149       <varlistentry>
 150         <term><option>--reverse</option></term>
 151
 152         <listitem>
 153           <para>Show reverse dependencies between units with
 154           <command>list-dependencies</command>, i.e. units with
 155           dependencies of type <varname>Wants=</varname> or
 156           <varname>Requires=</varname> on the given unit.
 157           </para>
 158         </listitem>
 159       </varlistentry>
 160
 161       <varlistentry>
 162         <term><option>--after</option></term>
 163         <term><option>--before</option></term>
 164
 165         <listitem>
 166           <para>Show which units are started after or before
 167           with <command>list-dependencies</command>, respectively.
 168           </para>
 169         </listitem>
 170       </varlistentry>
 171
 172       <varlistentry>
 173         <term><option>-l</option></term>
 174         <term><option>--full</option></term>
 175
 176         <listitem>
 177           <para>Do not ellipsize unit names, process tree entries,
 178           journal output, or truncate unit descriptions in the output
 179           of <command>status</command>, <command>list-units</command>,
 180           <command>list-jobs</command>, and
 181           <command>list-timers</command>.</para>
 182         </listitem>
 183       </varlistentry>
 184
 185       <varlistentry>
 186         <term><option>--show-types</option></term>
 187
 188         <listitem>
 189           <para>When showing sockets, show the type of the socket.</para>
 190         </listitem>
 191       </varlistentry>
 192
 193       <varlistentry>
 194         <term><option>--job-mode=</option></term>
 195
 196         <listitem>
 197         <para>When queuing a new job, this option controls how to deal with
 198         already queued jobs. It takes one of <literal>fail</literal>,
 199         <literal>replace</literal>,
 200         <literal>replace-irreversibly</literal>,
 201         <literal>isolate</literal>,
 202         <literal>ignore-dependencies</literal>,
 203         <literal>ignore-requirements</literal> or
 204         <literal>flush</literal>. Defaults to
 205         <literal>replace</literal>, except when the
 206         <command>isolate</command> command is used which implies the
 207         <literal>isolate</literal> job mode.</para>
 208
 209         <para>If <literal>fail</literal> is specified and a requested
 210         operation conflicts with a pending job (more specifically:
 211         causes an already pending start job to be reversed into a stop
 212         job or vice versa), cause the operation to fail.</para>
 213
 214         <para>If <literal>replace</literal> (the default) is
 215         specified, any conflicting pending job will be replaced, as
 216         necessary.</para>
 217
 218         <para>If <literal>replace-irreversibly</literal> is specified,
 219         operate like <literal>replace</literal>, but also mark the new
 220         jobs as irreversible. This prevents future conflicting
 221         transactions from replacing these jobs. The jobs can still be
 222         cancelled using the <command>cancel</command> command.</para>
 223
 224         <para><literal>isolate</literal> is only valid for start
 225         operations and causes all other units to be stopped when the
 226         specified unit is started. This mode is always used when the
 227         <command>isolate</command> command is used.</para>
 228
 229         <para><literal>flush</literal> will cause all queued jobs to
 230         be canceled when the new job is enqueued.</para>
 231
 232         <para>If <literal>ignore-dependencies</literal> is specified,
 233         then all unit dependencies are ignored for this new job and
 234         the operation is executed immediately. If passed, no required
 235         units of the unit passed will be pulled in, and no ordering
 236         dependencies will be honored. This is mostly a debugging and
 237         rescue tool for the administrator and should not be used by
 238         applications.</para>
 239
 240         <para><literal>ignore-requirements</literal> is similar to
 241         <literal>ignore-dependencies</literal>, but only causes the
 242         requirement dependencies to be ignored, the ordering
 243         dependencies will still be honoured.</para>
 244         </listitem>
 245
 246       </varlistentry>
 247
 248       <varlistentry>
 249         <term><option>-i</option></term>
 250         <term><option>--ignore-inhibitors</option></term>
 251
 252         <listitem>
 253           <para>When system shutdown or a sleep state is requested,
 254           ignore inhibitor locks. Applications can establish inhibitor
 255           locks to avoid that certain important operations (such as CD
 256           burning or suchlike) are interrupted by system shutdown or a
 257           sleep state. Any user may take these locks and privileged
 258           users may override these locks. If any locks are taken,
 259           shutdown and sleep state requests will normally fail
 260           (regardless of whether privileged or not) and a list of active locks
 261           is printed. However, if <option>--ignore-inhibitors</option>
 262           is specified, the locks are ignored and not printed, and the
 263           operation attempted anyway, possibly requiring additional
 264           privileges.</para>
 265         </listitem>
 266       </varlistentry>
 267
 268       <varlistentry>
 269         <term><option>-q</option></term>
 270         <term><option>--quiet</option></term>
 271
 272         <listitem>
 273           <para>Suppress output to standard output in
 274           <command>snapshot</command>,
 275           <command>is-active</command>,
 276           <command>is-failed</command>,
 277           <command>enable</command> and
 278         <command>disable</command>.</para>
 279         </listitem>
 280       </varlistentry>
 281
 282       <varlistentry>
 283         <term><option>--no-block</option></term>
 284
 285         <listitem>
 286           <para>Do not synchronously wait for the requested operation
 287           to finish. If this is not specified, the job will be
 288           verified, enqueued and <command>systemctl</command> will
 289           wait until it is completed. By passing this argument, it is
 290           only verified and enqueued.</para>
 291         </listitem>
 292       </varlistentry>
 293
 294       <varlistentry>
 295         <term><option>--no-legend</option></term>
 296
 297         <listitem>
 298           <para>Do not print the legend, i.e. the column headers and
 299           the footer with hints.</para>
 300         </listitem>
 301       </varlistentry>
 302
 303       <varlistentry>
 304         <term><option>--no-pager</option></term>
 305
 306         <listitem>
 307           <para>Do not pipe output into a pager.</para>
 308         </listitem>
 309       </varlistentry>
 310
 311       <varlistentry>
 312         <term><option>--system</option></term>
 313
 314         <listitem>
 315           <para>Talk to the systemd system manager. (Default)</para>
 316         </listitem>
 317       </varlistentry>
 318
 319       <varlistentry>
 320         <term><option>--user</option></term>
 321
 322         <listitem>
 323           <para>Talk to the systemd manager of the calling
 324           user.</para>
 325         </listitem>
 326       </varlistentry>
 327
 328       <varlistentry>
 329         <term><option>--no-wall</option></term>
 330
 331         <listitem>
 332           <para>Do not send wall message before halt, power-off,
 333           reboot.</para>
 334         </listitem>
 335       </varlistentry>
 336
 337       <varlistentry>
 338         <term><option>--global</option></term>
 339
 340         <listitem>
 341           <para>When used with <command>enable</command> and
 342           <command>disable</command>, operate on the global user
 343           configuration directory, thus enabling or disabling a unit
 344           file globally for all future logins of all users.</para>
 345         </listitem>
 346       </varlistentry>
 347
 348       <varlistentry>
 349         <term><option>--no-reload</option></term>
 350
 351         <listitem>
 352           <para>When used with <command>enable</command> and
 353           <command>disable</command>, do not implicitly reload daemon
 354           configuration after executing the changes.</para>
 355         </listitem>
 356       </varlistentry>
 357
 358       <varlistentry>
 359         <term><option>--no-ask-password</option></term>
 360
 361         <listitem>
 362           <para>When used with <command>start</command> and related
 363           commands, disables asking for passwords. Background services
 364           may require input of a password or passphrase string, for
 365           example to unlock system hard disks or cryptographic
 366           certificates. Unless this option is specified and the
 367           command is invoked from a terminal,
 368           <command>systemctl</command> will query the user on the
 369           terminal for the necessary secrets. Use this option to
 370           switch this behavior off. In this case, the password must be
 371           supplied by some other means (for example graphical password
 372           agents) or the service might fail. This also disables
 373           querying the user for authentication for privileged
 374           operations.</para>
 375         </listitem>
 376
 377       </varlistentry>
 378
 379       <varlistentry>
 380         <term><option>--kill-who=</option></term>
 381
 382         <listitem>
 383           <para>When used with <command>kill</command>, choose which
 384           processes to kill. Must be one of <option>main</option>,
 385           <option>control</option> or <option>all</option> to select
 386           whether to kill only the main process of the unit, the
 387           control process or all processes of the unit. If omitted,
 388           defaults to <option>all</option>.</para>
 389         </listitem>
 390
 391       </varlistentry>
 392
 393       <varlistentry>
 394         <term><option>-s</option></term>
 395         <term><option>--signal=</option></term>
 396
 397         <listitem>
 398           <para>When used with <command>kill</command>, choose which
 399           signal to send to selected processes. Must be one of the
 400           well known signal specifiers such as <constant>SIGTERM</constant>, <constant>SIGINT</constant> or
 401           <constant>SIGSTOP</constant>. If omitted, defaults to
 402           <option>SIGTERM</option>.</para>
 403         </listitem>
 404       </varlistentry>
 405
 406       <varlistentry>
 407         <term><option>-f</option></term>
 408         <term><option>--force</option></term>
 409
 410         <listitem>
 411           <para>When used with <command>enable</command>, overwrite
 412           any existing conflicting symlinks.</para>
 413
 414           <para>When used with <command>halt</command>,
 415           <command>poweroff</command>, <command>reboot</command> or
 416           <command>kexec</command>, execute the selected operation
 417           without shutting down all units. However, all processes will
 418           be killed forcibly and all file systems are unmounted or
 419           remounted read-only. This is hence a drastic but relatively
 420           safe option to request an immediate reboot. If
 421           <option>--force</option> is specified twice for these
 422           operations, they will be executed immediately without
 423           terminating any processes or umounting any file
 424           systems. Warning: specifying <option>--force</option> twice
 425           with any of these operations might result in data
 426           loss.</para>
 427         </listitem>
 428       </varlistentry>
 429
 430       <varlistentry>
 431         <term><option>--root=</option></term>
 432
 433         <listitem>
 434           <para>When used with
 435           <command>enable</command>/<command>disable</command>/<command>is-enabled</command>
 436           (and related commands), use alternative root path when
 437           looking for unit files.</para>
 438         </listitem>
 439
 440       </varlistentry>
 441
 442       <varlistentry>
 443         <term><option>--runtime</option></term>
 444
 445         <listitem>
 446           <para>When used with <command>enable</command>,
 447           <command>disable</command>,
 448           (and related commands), make changes only temporarily, so
 449           that they are lost on the next reboot. This will have the
 450           effect that changes are not made in subdirectories of
 451           <filename>/etc</filename> but in <filename>/run</filename>,
 452           with identical immediate effects, however, since the latter
 453           is lost on reboot, the changes are lost too.</para>
 454
 455           <para>Similarly, when used with
 456           <command>set-property</command>, make changes only
 457           temporarily, so that they are lost on the next
 458           reboot.</para>
 459         </listitem>
 460       </varlistentry>
 461
 462       <varlistentry>
 463         <term><option>-H</option></term>
 464         <term><option>--host</option></term>
 465
 466         <listitem>
 467           <para>Execute the operation remotely. Specify a hostname, or
 468           username and hostname separated by <literal>@</literal>, to
 469           connect to. This will use SSH to talk to the remote systemd
 470           instance.</para>
 471         </listitem>
 472       </varlistentry>
 473
 474       <varlistentry>
 475           <term><option>-M</option></term>
 476           <term><option>--machine=</option></term>
 477
 478           <listitem><para>Execute the operation on a local
 479           container. Specify a container name to connect
 480           to.</para></listitem>
 481       </varlistentry>
 482
 483       <varlistentry>
 484         <term><option>-n</option></term>
 485         <term><option>--lines=</option></term>
 486
 487         <listitem>
 488           <para>When used with <command>status</command>, controls the
 489           number of journal lines to show, counting from the most
 490           recent ones. Takes a positive integer argument. Defaults to
 491           10.</para>
 492         </listitem>
 493       </varlistentry>
 494
 495       <varlistentry>
 496         <term><option>-o</option></term>
 497         <term><option>--output=</option></term>
 498
 499         <listitem>
 500           <para>When used with <command>status</command>, controls the
 501           formatting of the journal entries that are shown. For the
 502           available choices, see
 503           <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 504           Defaults to <literal>short</literal>.</para>
 505         </listitem>
 506       </varlistentry>
 507
 508       <varlistentry>
 509         <term><option>--plain</option></term>
 510
 511         <listitem>
 512           <para>When used with <command>list-dependencies</command>,
 513           the output is printed as a list instead of a tree.</para>
 514         </listitem>
 515       </varlistentry>
 516
 517     </variablelist>
 518   </refsect1>
 519
 520   <refsect1>
 521     <title>Commands</title>
 522
 523     <para>The following commands are understood:</para>
 524
 525     <refsect2>
 526       <title>Unit Commands</title>
 527
 528       <variablelist>
 529         <varlistentry>
 530           <term><command>list-units <optional><replaceable>PATTERN</replaceable>...</optional></command></term>
 531
 532           <listitem>
 533             <para>List known units (subject to limitations specified
 534             with <option>-t</option>). If one or more
 535             <replaceable>PATTERN</replaceable>s are specified, only
 536             units matching one of them are shown.</para>
 537
 538             <para>This is the default command.</para>
 539           </listitem>
 540         </varlistentry>
 541
 542         <varlistentry>
 543           <term><command>list-sockets <optional><replaceable>PATTERN</replaceable>...</optional></command></term>
 544
 545           <listitem>
 546             <para>List socket units ordered by listening address.
 547             If one or more <replaceable>PATTERN</replaceable>s are
 548             specified, only socket units matching one of them are
 549             shown. Produces output similar to
 550             <programlisting>
 551 LISTEN           UNIT                        ACTIVATES
 552 /dev/initctl     systemd-initctl.socket      systemd-initctl.service
 553 ...
 554 [::]:22          sshd.socket                 sshd.service
 555 kobject-uevent 1 systemd-udevd-kernel.socket systemd-udevd.service
 556
 557 5 sockets listed.
 558             </programlisting>
 559             Note: because the addresses might contains spaces, this output
 560             is not suitable for programmatic consumption.
 561             </para>
 562
 563             <para>See also the options <option>--show-types</option>,
 564             <option>--all</option>, and <option>--failed</option>.</para>
 565           </listitem>
 566         </varlistentry>
 567
 568         <varlistentry>
 569           <term><command>list-timers <optional><replaceable>PATTERN</replaceable>...</optional></command></term>
 570
 571           <listitem>
 572             <para>List timer units ordered by the time they elapse
 573             next. If one or more <replaceable>PATTERN</replaceable>s
 574             are specified, only units matching one of them are shown.
 575             </para>
 576
 577             <para>See also the options <option>--all</option> and
 578             <option>--failed</option>.</para>
 579           </listitem>
 580         </varlistentry>
 581
 582         <varlistentry>
 583           <term><command>start <replaceable>NAME</replaceable>...</command></term>
 584
 585           <listitem>
 586             <para>Start (activate) one or more units specified on the
 587             command line.</para>
 588           </listitem>
 589         </varlistentry>
 590         <varlistentry>
 591           <term><command>stop <replaceable>NAME</replaceable>...</command></term>
 592
 593           <listitem>
 594             <para>Stop (deactivate) one or more units specified on the
 595             command line.</para>
 596           </listitem>
 597         </varlistentry>
 598         <varlistentry>
 599           <term><command>reload <replaceable>NAME</replaceable>...</command></term>
 600
 601           <listitem>
 602             <para>Asks all units listed on the command line to reload
 603             their configuration. Note that this will reload the
 604             service-specific configuration, not the unit configuration
 605             file of systemd. If you want systemd to reload the
 606             configuration file of a unit, use the
 607             <command>daemon-reload</command> command. In other words:
 608             for the example case of Apache, this will reload Apache's
 609             <filename>httpd.conf</filename> in the web server, not the
 610             <filename>apache.service</filename> systemd unit
 611             file.</para>
 612
 613             <para>This command should not be confused with the
 614             <command>daemon-reload</command> or <command>load</command>
 615             commands.</para>
 616           </listitem>
 617
 618         </varlistentry>
 619         <varlistentry>
 620           <term><command>restart <replaceable>NAME</replaceable>...</command></term>
 621
 622           <listitem>
 623             <para>Restart one or more units specified on the command
 624             line. If the units are not running yet, they will be
 625             started.</para>
 626           </listitem>
 627         </varlistentry>
 628         <varlistentry>
 629           <term><command>try-restart <replaceable>NAME</replaceable>...</command></term>
 630
 631           <listitem>
 632             <para>Restart one or more units specified on the command
 633             line if the units are running. This does nothing if units are not
 634             running.  Note that, for compatibility with Red Hat init
 635             scripts, <command>condrestart</command> is equivalent to this
 636             command.</para>
 637           </listitem>
 638         </varlistentry>
 639         <varlistentry>
 640           <term><command>reload-or-restart <replaceable>NAME</replaceable>...</command></term>
 641
 642           <listitem>
 643             <para>Reload one or more units if they support it. If not,
 644             restart them instead. If the units are not running yet, they
 645             will be started.</para>
 646           </listitem>
 647         </varlistentry>
 648         <varlistentry>
 649           <term><command>reload-or-try-restart <replaceable>NAME</replaceable>...</command></term>
 650
 651           <listitem>
 652             <para>Reload one or more units if they support it. If not,
 653             restart them instead. This does nothing if the units are not
 654             running. Note that, for compatibility with SysV init scripts,
 655             <command>force-reload</command> is equivalent to this
 656             command.</para>
 657           </listitem>
 658         </varlistentry>
 659         <varlistentry>
 660           <term><command>isolate <replaceable>NAME</replaceable></command></term>
 661
 662           <listitem>
 663             <para>Start the unit specified on the command line and its
 664             dependencies and stop all others.</para>
 665
 666             <para>This is similar to changing the runlevel in a
 667             traditional init system. The <command>isolate</command>
 668             command will immediately stop processes that are not enabled
 669             in the new unit, possibly including the graphical
 670             environment or terminal you are currently using.</para>
 671
 672             <para>Note that this is allowed only on units where
 673             <option>AllowIsolate=</option> is enabled. See
 674             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 675             for details.</para>
 676           </listitem>
 677         </varlistentry>
 678         <varlistentry>
 679           <term><command>kill <replaceable>NAME</replaceable>...</command></term>
 680
 681           <listitem>
 682             <para>Send a signal to one or more processes of the
 683             unit. Use <option>--kill-who=</option> to select which
 684             process to kill. Use <option>--kill-mode=</option> to select
 685             the kill mode and <option>--signal=</option> to select the
 686             signal to send.</para>
 687           </listitem>
 688         </varlistentry>
 689         <varlistentry>
 690           <term><command>is-active <replaceable>NAME</replaceable>...</command></term>
 691
 692           <listitem>
 693             <para>Check whether any of the specified units are active
 694             (i.e. running). Returns an exit code 0 if at least one is
 695             active, or non-zero otherwise. Unless <option>--quiet</option>
 696             is specified, this will also print the current unit state to
 697             STDOUT.</para>
 698           </listitem>
 699         </varlistentry>
 700         <varlistentry>
 701           <term><command>is-failed <replaceable>NAME</replaceable>...</command></term>
 702
 703           <listitem>
 704             <para>Check whether any of the specified units are in a "failed" state.
 705             Returns an exit code 0 if at least one has failed, non-zero
 706             otherwise. Unless <option>--quiet</option> is specified, this
 707             will also print the current unit state to
 708             STDOUT.</para>
 709           </listitem>
 710         </varlistentry>
 711         <varlistentry>
 712           <term><command>status</command> <optional><replaceable>NAME</replaceable>...|<replaceable>PID</replaceable>...]</optional></term>
 713
 714           <listitem>
 715             <para>Show terse runtime status information about one or
 716             more units, followed by most recent log data from the
 717             journal. If no units are specified, show all units (subject
 718             to limitations specified with <option>-t</option>). If a PID
 719             is passed, show information about the unit the process
 720             belongs to.</para>
 721
 722             <para>This function is intended to generate human-readable
 723             output. If you are looking for computer-parsable output,
 724             use <command>show</command> instead. By default this
 725             function only shows 10 lines of output and ellipsizes
 726             lines to fit in the terminal window. This can be changes
 727             with <option>--lines</option> and <option>--full</option>,
 728             see above. In addition, <command>journalctl
 729             --unit=<replaceable>NAME</replaceable></command> or
 730             <command>journalctl
 731             --user-unit=<replaceable>NAME</replaceable></command> use
 732             a similar filter for messages and might be more
 733             convenient.
 734             </para>
 735           </listitem>
 736         </varlistentry>
 737         <varlistentry>
 738           <term><command>show</command> <optional><replaceable>NAME</replaceable>...|<replaceable>JOB</replaceable>...</optional></term>
 739
 740           <listitem>
 741             <para>Show properties of one or more units, jobs, or the
 742             manager itself. If no argument is specified, properties of
 743             the manager will be shown. If a unit name is specified,
 744             properties of the unit is shown, and if a job id is
 745             specified, properties of the job is shown. By default, empty
 746             properties are suppressed. Use <option>--all</option> to
 747             show those too. To select specific properties to show, use
 748             <option>--property=</option>. This command is intended to be
 749             used whenever computer-parsable output is required. Use
 750             <command>status</command> if you are looking for formatted
 751             human-readable output.</para>
 752           </listitem>
 753         </varlistentry>
 754         <varlistentry>
 755           <term><command>cat <replaceable>NAME</replaceable>...</command></term>
 756
 757           <listitem>
 758             <para>Show backing files of one or more units. Prints the
 759             "fragment" and "drop-ins" (source files) of units. Each
 760             file is preceded by a comment which includes the file
 761             name.</para>
 762           </listitem>
 763         </varlistentry>
 764         <varlistentry>
 765           <term><command>set-property <replaceable>NAME</replaceable> <replaceable>ASSIGNMENT</replaceable>...</command></term>
 766
 767           <listitem>
 768             <para>Set the specified unit properties at runtime where
 769             this is supported. This allows changing configuration
 770             parameter properties such as resource control settings at
 771             runtime. Not all properties may be changed at runtime, but
 772             many resource control settings (primarily those in
 773             <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
 774             may. The changes are applied instantly, and stored on disk
 775             for future boots, unless <option>--runtime</option> is
 776             passed, in which case the settings only apply until the
 777             next reboot. The syntax of the property assignment follows
 778             closely the syntax of assignments in unit files.</para>
 779
 780             <para>Example: <command>systemctl set-property foobar.service CPUShares=777</command></para>
 781
 782             <para>Note that this command allows changing multiple
 783             properties at the same time, which is preferable over
 784             setting them individually. Like unit file configuration
 785             settings, assigning the empty list to list parameters will
 786             reset the list.</para>
 787           </listitem>
 788         </varlistentry>
 789
 790         <varlistentry>
 791           <term><command>help <replaceable>NAME</replaceable>...|<replaceable>PID</replaceable>...</command></term>
 792
 793           <listitem>
 794             <para>Show manual pages for one or more units, if
 795             available. If a PID is given, the manual pages for the unit
 796             the process belongs to are shown.</para>
 797           </listitem>
 798         </varlistentry>
 799
 800         <varlistentry>
 801           <term><command>reset-failed [<replaceable>NAME</replaceable>...]</command></term>
 802
 803           <listitem>
 804             <para>Reset the <literal>failed</literal> state of the
 805             specified units, or if no unit name is passed, reset the state of all
 806             units. When a unit fails in some way (i.e. process exiting
 807             with non-zero error code, terminating abnormally or timing
 808             out), it will automatically enter the
 809             <literal>failed</literal> state and its exit code and status
 810             is recorded for introspection by the administrator until the
 811             service is restarted or reset with this command.</para>
 812           </listitem>
 813         </varlistentry>
 814
 815         <varlistentry>
 816           <term><command>list-dependencies <replaceable>NAME</replaceable></command></term>
 817
 818           <listitem>
 819             <para>Shows required and wanted units of the specified
 820             unit. If no unit is specified,
 821             <filename>default.target</filename> is implied. Target units
 822             are recursively expanded.  When <option>--all</option> is
 823             passed, all other units are recursively expanded as
 824             well.</para>
 825           </listitem>
 826         </varlistentry>
 827       </variablelist>
 828     </refsect2>
 829
 830     <refsect2>
 831       <title>Unit File Commands</title>
 832
 833       <variablelist>
 834         <varlistentry>
 835           <term><command>list-unit-files <optional><replaceable>PATTERN...</replaceable></optional></command></term>
 836
 837           <listitem>
 838             <para>List installed unit files. If one or more
 839             <replaceable>PATTERN</replaceable>s are specified, only
 840             units whose filename (just the last component of the path)
 841             matches one of them are shown.</para>
 842           </listitem>
 843         </varlistentry>
 844
 845         <varlistentry>
 846           <term><command>enable <replaceable>NAME</replaceable>...</command></term>
 847
 848           <listitem>
 849             <para>Enable one or more unit files or unit file instances,
 850             as specified on the command line. This will create a number
 851             of symlinks as encoded in the <literal>[Install]</literal>
 852             sections of the unit files. After the symlinks have been
 853             created, the systemd configuration is reloaded (in a way that
 854             is equivalent to <command>daemon-reload</command>) to ensure
 855             the changes are taken into account immediately. Note that
 856             this does <emphasis>not</emphasis> have the effect of also
 857             starting any of the units being enabled. If this
 858             is desired, a separate <command>start</command> command must
 859             be invoked for the unit. Also note that in case of instance
 860             enablement, symlinks named the same as instances are created in
 861             the install location, however they all point to the same
 862             template unit file.</para>
 863
 864             <para>This command will print the actions executed. This
 865             output may be suppressed by passing <option>--quiet</option>.
 866             </para>
 867
 868             <para>Note that this operation creates only the suggested
 869             symlinks for the units. While this command is the
 870             recommended way to manipulate the unit configuration
 871             directory, the administrator is free to make additional
 872             changes manually by placing or removing symlinks in the
 873             directory. This is particularly useful to create
 874             configurations that deviate from the suggested default
 875             installation. In this case, the administrator must make sure
 876             to invoke <command>daemon-reload</command> manually as
 877             necessary to ensure the changes are taken into account.
 878             </para>
 879
 880             <para>Enabling units should not be confused with starting
 881             (activating) units, as done by the <command>start</command>
 882             command. Enabling and starting units is orthogonal: units
 883             may be enabled without being started and started without
 884             being enabled. Enabling simply hooks the unit into various
 885             suggested places (for example, so that the unit is
 886             automatically started on boot or when a particular kind of
 887             hardware is plugged in). Starting actually spawns the daemon
 888             process (in case of service units), or binds the socket (in
 889             case of socket units), and so on.</para>
 890
 891             <para>Depending on whether <option>--system</option>,
 892             <option>--user</option>, <option>--runtime</option>,
 893             or <option>--global</option> is specified, this enables the unit
 894             for the system, for the calling user only, for only this boot of
 895             the system, or for all future logins of all users, or only this
 896             boot.  Note that in the last case, no systemd daemon
 897             configuration is reloaded.</para>
 898           </listitem>
 899         </varlistentry>
 900
 901         <varlistentry>
 902           <term><command>disable <replaceable>NAME</replaceable>...</command></term>
 903
 904           <listitem>
 905             <para>Disables one or more units. This removes all symlinks
 906             to the specified unit files from the unit configuration
 907             directory, and hence undoes the changes made by
 908             <command>enable</command>. Note however that this removes
 909             all symlinks to the unit files (i.e. including manual
 910             additions), not just those actually created by
 911             <command>enable</command>. This call implicitly reloads the
 912             systemd daemon configuration after completing the disabling
 913             of the units. Note that this command does not implicitly
 914             stop the units that are being disabled. If this is desired,
 915             an additional <command>stop</command> command should be
 916             executed afterwards.</para>
 917
 918             <para>This command will print the actions executed. This
 919             output may be suppressed by passing <option>--quiet</option>.
 920             </para>
 921
 922             <para>This command honors <option>--system</option>,
 923             <option>--user</option>, <option>--runtime</option> and
 924             <option>--global</option> in a similar way as
 925             <command>enable</command>.</para>
 926           </listitem>
 927         </varlistentry>
 928
 929         <varlistentry>
 930           <term><command>is-enabled <replaceable>NAME</replaceable>...</command></term>
 931
 932           <listitem>
 933             <para>Checks whether any of the specified unit files are
 934             enabled (as with <command>enable</command>). Returns an
 935             exit code of 0 if at least one is enabled, non-zero
 936             otherwise. Prints the current enable status (see table).
 937             To suppress this output, use <option>--quiet</option>.
 938             </para>
 939
 940             <table>
 941               <title>
 942                 <command>is-enabled</command> output
 943               </title>
 944
 945               <tgroup cols='3'>
 946                 <thead>
 947                   <row>
 948                     <entry>Printed string</entry>
 949                     <entry>Meaning</entry>
 950                     <entry>Return value</entry>
 951                   </row>
 952                 </thead>
 953                 <tbody>
 954                   <row>
 955                     <entry><literal>enabled</literal></entry>
 956                     <entry morerows='1'>Enabled through a symlink in <filename>.wants</filename> directory (permanently or just in <filename>/run</filename>)</entry>
 957                     <entry morerows='1'>0</entry>
 958                   </row>
 959                   <row>
 960                     <entry><literal>enabled-runtime</literal></entry>
 961                   </row>
 962                   <row>
 963                     <entry><literal>linked</literal></entry>
 964                     <entry morerows='1'>Made available through a symlink to the unit file (permanently or just in <filename>/run</filename>)</entry>
 965                     <entry morerows='1'>1</entry>
 966                   </row>
 967                   <row>
 968                     <entry><literal>linked-runtime</literal></entry>
 969                   </row>
 970                   <row>
 971                     <entry><literal>masked</literal></entry>
 972                     <entry morerows='1'>Disabled entirely (permanently or just in <filename>/run</filename>)</entry>
 973                     <entry morerows='1'>1</entry>
 974                   </row>
 975                   <row>
 976                     <entry><literal>masked-runtime</literal></entry>
 977                   </row>
 978                   <row>
 979                     <entry><literal>static</literal></entry>
 980                     <entry>Unit is not enabled, but has no provisions for enabling in [Install] section</entry>
 981                     <entry>1</entry>
 982                   </row>
 983                   <row>
 984                     <entry><literal>disabled</literal></entry>
 985                     <entry>Unit is not enabled</entry>
 986                     <entry>1</entry>
 987                   </row>
 988                 </tbody>
 989               </tgroup>
 990             </table>
 991
 992           </listitem>
 993         </varlistentry>
 994
 995         <varlistentry>
 996           <term><command>reenable <replaceable>NAME</replaceable>...</command></term>
 997
 998           <listitem>
 999             <para>Reenable one or more unit files, as specified on the
1000             command line. This is a combination of
1001             <command>disable</command> and <command>enable</command> and
1002             is useful to reset the symlinks a unit is enabled with to
1003             the defaults configured in the <literal>[Install]</literal>
1004             section of the unit file.</para>
1005           </listitem>
1006         </varlistentry>
1007
1008         <varlistentry>
1009           <term><command>preset <replaceable>NAME</replaceable>...</command></term>
1010
1011           <listitem>
1012             <para>Reset one or more unit files, as specified on the
1013             command line, to the defaults configured in the preset
1014             policy files. This has the same effect as
1015             <command>disable</command> or <command>enable</command>,
1016             depending how the unit is listed in the preset files. For
1017             more information on the preset policy format, see
1018             <citerefentry><refentrytitle>systemd.preset</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1019             For more information on the concept of presets, please
1020             consult the
1021             <ulink url="http://freedesktop.org/wiki/Software/systemd/Preset">Preset</ulink>
1022             document.</para>
1023           </listitem>
1024         </varlistentry>
1025
1026         <varlistentry>
1027           <term><command>mask <replaceable>NAME</replaceable>...</command></term>
1028
1029           <listitem>
1030             <para>Mask one or more unit files, as specified on the
1031             command line. This will link these units to
1032             <filename>/dev/null</filename>, making it impossible to
1033             start them. This is a stronger version of
1034             <command>disable</command>, since it prohibits all kinds of
1035             activation of the unit, including manual activation. Use
1036             this option with care. This honors the
1037             <option>--runtime</option> option to only mask temporarily
1038             until the next reoobt of the system.</para>
1039           </listitem>
1040         </varlistentry>
1041
1042         <varlistentry>
1043           <term><command>unmask <replaceable>NAME</replaceable>...</command></term>
1044
1045           <listitem>
1046             <para>Unmask one or more unit files, as specified on the
1047             command line. This will undo the effect of
1048             <command>mask</command>.</para>
1049           </listitem>
1050         </varlistentry>
1051
1052         <varlistentry>
1053           <term><command>link <replaceable>FILENAME</replaceable>...</command></term>
1054
1055           <listitem>
1056             <para>Link a unit file that is not in the unit file search
1057             paths into the unit file search path. This requires an
1058             absolute path to a unit file. The effect of this can be
1059             undone with <command>disable</command>. The effect of this
1060             command is that a unit file is available for
1061             <command>start</command> and other commands although it
1062             is not installed directly in the unit search path.</para>
1063           </listitem>
1064         </varlistentry>
1065
1066         <varlistentry>
1067           <term><command>get-default</command></term>
1068
1069           <listitem>
1070             <para>Get the default target specified
1071             via <filename>default.target</filename> link.</para>
1072           </listitem>
1073         </varlistentry>
1074
1075         <varlistentry>
1076           <term><command>set-default <replaceable>NAME</replaceable></command></term>
1077
1078           <listitem>
1079             <para>Set the default target to boot into. Command links
1080             <filename>default.target</filename> to the given unit.</para>
1081           </listitem>
1082         </varlistentry>
1083       </variablelist>
1084     </refsect2>
1085
1086     <refsect2>
1087       <title>Job Commands</title>
1088
1089       <variablelist>
1090         <varlistentry>
1091           <term><command>list-jobs <optional><replaceable>PATTERN...</replaceable></optional></command></term>
1092
1093           <listitem>
1094             <para>List jobs that are in progress. If one or more
1095             <replaceable>PATTERN</replaceable>s are specified, only
1096             jobs for units matching one of them are shown.</para>
1097           </listitem>
1098         </varlistentry>
1099         <varlistentry>
1100           <term><command>cancel <replaceable>JOB</replaceable>...</command></term>
1101
1102           <listitem>
1103             <para>Cancel one or more jobs specified on the command line
1104             by their numeric job IDs. If no job ID is specified, cancel
1105             all pending jobs.</para>
1106           </listitem>
1107         </varlistentry>
1108       </variablelist>
1109     </refsect2>
1110
1111     <refsect2>
1112       <title>Snapshot Commands</title>
1113
1114       <variablelist>
1115         <varlistentry>
1116           <term><command>snapshot <optional><replaceable>NAME</replaceable></optional></command></term>
1117
1118           <listitem>
1119             <para>Create a snapshot. If a snapshot name is specified,
1120             the new snapshot will be named after it. If none is
1121             specified, an automatic snapshot name is generated. In either
1122             case, the snapshot name used is printed to STDOUT, unless
1123             <option>--quiet</option> is specified.</para>
1124
1125             <para>A snapshot refers to a saved state of the systemd
1126             manager. It is implemented itself as a unit that is
1127             generated dynamically with this command and has dependencies
1128             on all units active at the time. At a later time, the user
1129             may return to this state by using the
1130             <command>isolate</command> command on the snapshot unit.
1131             </para>
1132
1133             <para>Snapshots are only useful for saving and restoring
1134             which units are running or are stopped, they do not
1135             save/restore any other state. Snapshots are dynamic and lost
1136             on reboot.</para>
1137           </listitem>
1138         </varlistentry>
1139         <varlistentry>
1140           <term><command>delete <replaceable>NAME</replaceable>...</command></term>
1141
1142           <listitem>
1143             <para>Remove a snapshot previously created with
1144             <command>snapshot</command>.</para>
1145           </listitem>
1146         </varlistentry>
1147       </variablelist>
1148     </refsect2>
1149
1150     <refsect2>
1151       <title>Environment Commands</title>
1152
1153       <variablelist>
1154         <varlistentry>
1155           <term><command>show-environment</command></term>
1156
1157           <listitem>
1158             <para>Dump the systemd manager environment block. The
1159             environment block will be dumped in straight-forward form
1160             suitable for sourcing into a shell script. This environment
1161             block will be passed to all processes the manager
1162             spawns.</para>
1163           </listitem>
1164         </varlistentry>
1165         <varlistentry>
1166           <term><command>set-environment <replaceable>VARIABLE=VALUE</replaceable>...</command></term>
1167
1168           <listitem>
1169             <para>Set one or more systemd manager environment variables,
1170             as specified on the command line.</para>
1171           </listitem>
1172         </varlistentry>
1173         <varlistentry>
1174           <term><command>unset-environment <replaceable>VARIABLE</replaceable>...</command></term>
1175
1176           <listitem>
1177             <para>Unset one or more systemd manager environment
1178             variables. If only a variable name is specified, it will be
1179             removed regardless of its value. If a variable and a value
1180             are specified, the variable is only removed if it has the
1181             specified value.</para>
1182           </listitem>
1183         </varlistentry>
1184       </variablelist>
1185     </refsect2>
1186
1187     <refsect2>
1188       <title>Manager Lifecycle Commands</title>
1189
1190       <variablelist>
1191         <varlistentry>
1192           <term><command>daemon-reload</command></term>
1193
1194           <listitem>
1195             <para>Reload systemd manager configuration. This will reload
1196             all unit files and recreate the entire dependency
1197             tree. While the daemon is being reloaded, all sockets systemd
1198             listens on on behalf of user configuration will stay
1199             accessible.</para> <para>This command should not be confused
1200             with the <command>load</command> or
1201             <command>reload</command> commands.</para>
1202           </listitem>
1203         </varlistentry>
1204         <varlistentry>
1205           <term><command>daemon-reexec</command></term>
1206
1207           <listitem>
1208             <para>Reexecute the systemd manager. This will serialize the
1209             manager state, reexecute the process and deserialize the
1210             state again. This command is of little use except for
1211             debugging and package upgrades. Sometimes, it might be
1212             helpful as a heavy-weight <command>daemon-reload</command>.
1213             While the daemon is being reexecuted, all sockets systemd listening
1214             on behalf of user configuration will stay accessible.
1215             </para>
1216           </listitem>
1217         </varlistentry>
1218       </variablelist>
1219     </refsect2>
1220
1221     <refsect2>
1222       <title>System Commands</title>
1223
1224       <variablelist>
1225         <varlistentry>
1226           <term><command>default</command></term>
1227
1228           <listitem>
1229             <para>Enter default mode. This is mostly equivalent to
1230             <command>isolate default.target</command>.</para>
1231           </listitem>
1232         </varlistentry>
1233         <varlistentry>
1234           <term><command>rescue</command></term>
1235
1236           <listitem>
1237             <para>Enter rescue mode. This is mostly equivalent to
1238             <command>isolate rescue.target</command>, but also prints a
1239             wall message to all users.</para>
1240           </listitem>
1241         </varlistentry>
1242         <varlistentry>
1243           <term><command>emergency</command></term>
1244
1245           <listitem>
1246             <para>Enter emergency mode. This is mostly equivalent to
1247             <command>isolate emergency.target</command>, but also prints
1248             a wall message to all users.</para>
1249           </listitem>
1250         </varlistentry>
1251         <varlistentry>
1252           <term><command>halt</command></term>
1253
1254           <listitem>
1255             <para>Shut down and halt the system. This is mostly equivalent to
1256             <command>start halt.target --irreversible</command>, but also
1257             prints a wall message to all users.  If combined with
1258             <option>--force</option>, shutdown of all running services is
1259             skipped, however all processes are killed and all file
1260             systems are unmounted or mounted read-only, immediately
1261             followed by the system halt.  If <option>--force</option> is
1262             specified twice, the operation is immediately executed
1263             without terminating any processes or unmounting any file
1264             systems. This may result in data loss.</para>
1265           </listitem>
1266         </varlistentry>
1267         <varlistentry>
1268           <term><command>poweroff</command></term>
1269
1270           <listitem>
1271             <para>Shut down and power-off the system. This is mostly
1272             equivalent to <command>start poweroff.target --irreversible</command>,
1273             but also prints a wall message to all users. If combined with
1274             <option>--force</option>, shutdown of all running services is
1275             skipped, however all processes are killed and all file
1276             systems are unmounted or mounted read-only, immediately
1277             followed by the powering off. If <option>--force</option> is
1278             specified twice, the operation is immediately executed
1279             without terminating any processes or unmounting any file
1280             systems. This may result in data loss.</para>
1281           </listitem>
1282         </varlistentry>
1283         <varlistentry>
1284           <term><command>reboot <optional><replaceable>arg</replaceable></optional></command></term>
1285
1286           <listitem>
1287             <para>Shut down and reboot the system. This is mostly
1288             equivalent to <command>start reboot.target --irreversible</command>,
1289             but also prints a wall message to all users. If combined with
1290             <option>--force</option>, shutdown of all running services is
1291             skipped, however all processes are killed and all file
1292             systems are unmounted or mounted read-only, immediately
1293             followed by the reboot. If <option>--force</option> is
1294             specified twice, the operation is immediately executed
1295             without terminating any processes or unmounting any file
1296             systems. This may result in data loss.</para>
1297
1298             <para>If the optional argument
1299             <replaceable>arg</replaceable> is given, it will be passed
1300             as the optional argument to the
1301             <citerefentry><refentrytitle>reboot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
1302             system call. The value is architecture and firmware
1303             specific. As an example, <literal>recovery</literal> might
1304             be used to trigger system recovery, and
1305             <literal>fota</literal> might be used to trigger a
1306             <quote>firmware over the air</quote> update.</para>
1307           </listitem>
1308         </varlistentry>
1309         <varlistentry>
1310           <term><command>kexec</command></term>
1311
1312           <listitem>
1313             <para>Shut down and reboot the system via kexec. This is
1314             mostly equivalent to <command>start kexec.target --irreversible</command>,
1315             but also prints a wall message to all users. If combined
1316             with <option>--force</option>, shutdown of all running
1317             services is skipped, however all processes are killed and
1318             all file systems are unmounted or mounted read-only,
1319             immediately followed by the reboot.</para>
1320           </listitem>
1321         </varlistentry>
1322         <varlistentry>
1323           <term><command>exit</command></term>
1324
1325           <listitem>
1326             <para>Ask the systemd manager to quit. This is only
1327             supported for user service managers (i.e. in conjunction
1328             with the <option>--user</option> option) and will fail
1329             otherwise.</para>
1330           </listitem>
1331
1332         </varlistentry>
1333         <varlistentry>
1334           <term><command>suspend</command></term>
1335
1336           <listitem>
1337             <para>Suspend the system. This will trigger activation of
1338             the special <filename>suspend.target</filename> target.
1339             </para>
1340           </listitem>
1341         </varlistentry>
1342         <varlistentry>
1343           <term><command>hibernate</command></term>
1344
1345           <listitem>
1346             <para>Hibernate the system. This will trigger activation of
1347             the special <filename>hibernate.target</filename> target.
1348             </para>
1349           </listitem>
1350         </varlistentry>
1351         <varlistentry>
1352           <term><command>hybrid-sleep</command></term>
1353
1354           <listitem>
1355             <para>Hibernate and suspend the system. This will trigger
1356             activation of the special
1357             <filename>hybrid-sleep.target</filename> target.</para>
1358           </listitem>
1359         </varlistentry>
1360         <varlistentry>
1361           <term><command>switch-root <replaceable>ROOT</replaceable> <optional><replaceable>INIT</replaceable></optional></command></term>
1362
1363           <listitem>
1364             <para>Switches to a different root directory and executes a
1365             new system manager process below it. This is intended for
1366             usage in initial RAM disks ("initrd"), and will transition
1367             from the initrd's system manager process (a.k.a "init"
1368             process) to the main system manager process. This call takes two
1369             arguments: the directory that is to become the new root directory, and
1370             the path to the new system manager binary below it to
1371             execute as PID 1. If the latter is omitted or the empty
1372             string, a systemd binary will automatically be searched for
1373             and used as init. If the system manager path is omitted or
1374             equal to the empty string, the state of the initrd's system
1375             manager process is passed to the main system manager, which
1376             allows later introspection of the state of the services
1377             involved in the initrd boot.</para>
1378           </listitem>
1379         </varlistentry>
1380       </variablelist>
1381     </refsect2>
1382
1383     <refsect2>
1384       <title>Parameter Syntax</title>
1385
1386     <para>For unit commands, the specified
1387     <replaceable>NAME</replaceable> should be the full name of the
1388     unit, or an abbreviated name which is automatically extended with
1389     the <literal>.service</literal> suffix.
1390     <programlisting># systemctl start foo.service</programlisting> is equivalent to:
1391     <programlisting># systemctl start foo</programlisting>
1392     Note that (absolute) paths to device nodes are automatically converted to device unit names, and other (absolute) paths to mount unit names.
1393     <programlisting># systemctl status /dev/sda
1394 # systemctl status /home</programlisting> is equivalent to:
1395     <programlisting># systemctl status dev-sda.device
1396 # systemctl status home.mount</programlisting></para>
1397
1398     <para>For unit file commands, the
1399     specified <replaceable>NAME</replaceable> should be the full name
1400     of the unit file, or the absolute path to the unit file.
1401     <programlisting># systemctl link /path/to/foo.service</programlisting>
1402     </para>
1403     </refsect2>
1404
1405   </refsect1>
1406
1407   <refsect1>
1408     <title>Exit status</title>
1409
1410     <para>On success, 0 is returned, a non-zero failure
1411     code otherwise.</para>
1412   </refsect1>
1413
1414   <refsect1>
1415     <title>Environment</title>
1416
1417     <variablelist class='environment-variables'>
1418       <varlistentry>
1419         <term><varname>$SYSTEMD_PAGER</varname></term>
1420
1421         <listitem>
1422           <para>Pager to use when <option>--no-pager</option> is not
1423           given; overrides <varname>$PAGER</varname>.  Setting this to
1424           an empty string or the value <literal>cat</literal> is
1425           equivalent to passing
1426           <option>--no-pager</option>.</para>
1427         </listitem>
1428       </varlistentry>
1429     </variablelist>
1430   </refsect1>
1431
1432   <refsect1>
1433     <title>See Also</title>
1434     <para>
1435       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1436       <citerefentry><refentrytitle>systemadm</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1437       <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1438       <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1439       <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1440       <citerefentry><refentrytitle>systemd.resource-management</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1441       <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1442       <citerefentry><refentrytitle>wall</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1443       <citerefentry><refentrytitle>systemd.preset</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1444     </para>
1445   </refsect1>
1446
1447 </refentry>