man/systemd.special.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
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  13   (at your option) any later version.
  14
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  18   Lesser General Public License for more details.
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  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="systemd.special">
  25
  26         <refentryinfo>
  27                 <title>systemd.special</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.special</refentrytitle>
  42                 <manvolnum>7</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.special</refname>
  47                 <refpurpose>Special systemd units</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename>basic.target</filename>,
  52                 <filename>ctrl-alt-del.target</filename>,
  53                 <filename>dbus.service</filename>,
  54                 <filename>dbus.socket</filename>,
  55                 <filename>default.target</filename>,
  56                 <filename>display-manager.service</filename>,
  57                 <filename>emergency.target</filename>,
  58                 <filename>exit.service</filename>,
  59                 <filename>final.service</filename>,
  60                 <filename>graphical.target</filename>,
  61                 <filename>hibernate.target</filename>,
  62                 <filename>http-daemon.target</filename>,
  63                 <filename>halt.target</filename>,
  64                 <filename>kbrequest.target</filename>,
  65                 <filename>kexec.target</filename>,
  66                 <filename>local-fs.target</filename>,
  67                 <filename>local-fs-pre.target</filename>,
  68                 <filename>mail-transfer-agent.target</filename>,
  69                 <filename>multi-user.target</filename>,
  70                 <filename>network.target</filename>,
  71                 <filename>nss-lookup.target</filename>,
  72                 <filename>poweroff.target</filename>,
  73                 <filename>reboot.target</filename>,
  74                 <filename>remote-fs.target</filename>,
  75                 <filename>remote-fs-pre.target</filename>,
  76                 <filename>rescue.target</filename>,
  77                 <filename>rpcbind.target</filename>,
  78                 <filename>runlevel2.target</filename>,
  79                 <filename>runlevel3.target</filename>,
  80                 <filename>runlevel4.target</filename>,
  81                 <filename>runlevel5.target</filename>,
  82                 <filename>shutdown.target</filename>,
  83                 <filename>sigpwr.target</filename>,
  84                 <filename>sleep.target</filename>,
  85                 <filename>sockets.target</filename>,
  86                 <filename>suspend.target</filename>,
  87                 <filename>swap.target</filename>,
  88                 <filename>sysinit.target</filename>,
  89                 <filename>syslog.service</filename>,
  90                 <filename>syslog.socket</filename>,
  91                 <filename>syslog.target</filename>,
  92                 <filename>time-sync.target</filename>,
  93                 <filename>umount.target</filename></para>
  94         </refsynopsisdiv>
  95
  96         <refsect1>
  97                 <title>Description</title>
  98
  99                 <para>A few units are treated specially by
 100                 systemd. They have special internal semantics and
 101                 cannot be renamed.</para>
 102         </refsect1>
 103
 104         <refsect1>
 105                 <title>Special System Units</title>
 106
 107                 <variablelist>
 108                         <varlistentry>
 109                                 <term><filename>basic.target</filename></term>
 110                                 <listitem>
 111                                         <para>A special target unit
 112                                         covering early boot-up.</para>
 113                                         <para>systemd automatically
 114                                         adds dependencies of the types
 115                                         Requires and After for this
 116                                         target unit to all SysV
 117                                         service units configured for
 118                                         runlevel 1 to 5.</para>
 119                                         <para>Usually this should pull-in
 120                                         all sockets, mount points,
 121                                         swap devices and other basic
 122                                         initialization necessary for
 123                                         the general purpose
 124                                         daemons. Most normal daemons
 125                                         should have dependencies of
 126                                         type After and Requires on
 127                                         this unit.</para>
 128                                 </listitem>
 129                         </varlistentry>
 130                         <varlistentry>
 131                                 <term><filename>ctrl-alt-del.target</filename></term>
 132                                 <listitem>
 133                                         <para>systemd starts this
 134                                         target whenever
 135                                         Control+Alt+Del is pressed on
 136                                         the console. Usually this
 137                                         should be aliased (symlinked)
 138                                         to
 139                                         <filename>reboot.target</filename>.</para>
 140                                 </listitem>
 141                         </varlistentry>
 142                         <varlistentry>
 143                                 <term><filename>dbus.service</filename></term>
 144                                 <listitem>
 145                                         <para>A special unit for the
 146                                         D-Bus system bus. As soon as
 147                                         this service is fully started
 148                                         up systemd will connect to it
 149                                         and register its
 150                                         service.</para>
 151                                 </listitem>
 152                         </varlistentry>
 153                         <varlistentry>
 154                                 <term><filename>dbus.socket</filename></term>
 155                                 <listitem>
 156                                         <para>A special unit for the
 157                                         D-Bus system bus socket. All
 158                                         units with
 159                                         <literal>Type=dbus</literal>
 160                                         automatically gain a
 161                                         dependency on this
 162                                         unit.</para>
 163                                 </listitem>
 164                         </varlistentry>
 165                         <varlistentry>
 166                                 <term><filename>default.target</filename></term>
 167                                 <listitem>
 168                                         <para>The default unit systemd
 169                                         starts at bootup. Usually this
 170                                         should be aliased (symlinked)
 171                                         to
 172                                         <filename>multi-user.target</filename>
 173                                         or
 174                                         <filename>graphical.target</filename>.</para>
 175                                         <para>The default unit systemd
 176                                         starts at bootup can be
 177                                         overridden with the
 178                                         <varname>systemd.unit=</varname>
 179                                         kernel command line option.</para>
 180                                 </listitem>
 181                         </varlistentry>
 182                         <varlistentry>
 183                                 <term><filename>display-manager.service</filename></term>
 184                                 <listitem>
 185                                         <para>The display manager
 186                                         service. Usually this should
 187                                         be aliased (symlinked) to
 188                                         <filename>gdm.service</filename>
 189                                         or a similar display manager
 190                                         service.</para>
 191                                         <para>systemd automatically
 192                                         adds dependencies of type
 193                                         After for this target unit to
 194                                         all SysV init script service
 195                                         units with a LSB header
 196                                         referring to the
 197                                         <literal>$x-display-manager</literal>
 198                                         facility, for compatibility
 199                                         with Debian.</para>
 200                                 </listitem>
 201                         </varlistentry>
 202                         <varlistentry>
 203                                 <term><filename>emergency.target</filename></term>
 204                                 <listitem>
 205                                         <para>A special target unit
 206                                         that starts an emergency
 207                                         shell on the main
 208                                         console. This unit is supposed
 209                                         to be used with the kernel
 210                                         command line option
 211                                         <varname>systemd.unit=</varname>
 212                                         and has otherwise little use.
 213                                         </para>
 214                                 </listitem>
 215                         </varlistentry>
 216                         <varlistentry>
 217                                 <term><filename>final.target</filename></term>
 218                                 <listitem>
 219                                         <para>A special target unit
 220                                         that is used during the
 221                                         shutdown logic and may be used
 222                                         to pull in late services after
 223                                         all normal services are
 224                                         already terminated and all
 225                                         mounts unmounted.
 226                                         </para>
 227                                 </listitem>
 228                         </varlistentry>
 229                         <varlistentry>
 230                                 <term><filename>graphical.target</filename></term>
 231                                 <listitem>
 232                                         <para>A special target unit
 233                                         for setting up a graphical
 234                                         login screen. This pulls in
 235                                         <filename>multi-user.target</filename>.</para>
 236
 237                                         <para>Units that are needed
 238                                         for graphical login shall add
 239                                         Wants dependencies for their
 240                                         unit to this unit (or
 241                                         <filename>multi-user.target</filename>)
 242                                         during installation.</para>
 243                                 </listitem>
 244                         </varlistentry>
 245                         <varlistentry>
 246                                 <term><filename>hibernate.target</filename></term>
 247                                 <listitem>
 248                                         <para>A special target unit
 249                                         for hibernating the
 250                                         system. This pulls in
 251                                         <filename>sleep.target</filename>.</para>
 252                                 </listitem>
 253                         </varlistentry>
 254                         <varlistentry>
 255                                 <term><filename>http-daemon.target</filename></term>
 256                                 <listitem>
 257                                         <para>A target for pulling in
 258                                         an HTTP server if there is
 259                                         any.</para>
 260                                         <para>systemd automatically
 261                                         adds dependencies of type
 262                                         After for this target unit to
 263                                         all SysV init script service
 264                                         units with a LSB header
 265                                         referring to the
 266                                         <literal>$httpd</literal>
 267                                         facility.</para>
 268                                 </listitem>
 269                         </varlistentry>
 270                         <varlistentry>
 271                                 <term><filename>halt.target</filename></term>
 272                                 <listitem>
 273                                         <para>A special target unit
 274                                         for shutting down and halting the system.</para>
 275
 276                                         <para>Applications wanting to
 277                                         halt the system should start
 278                                         this unit.</para>
 279                                 </listitem>
 280                         </varlistentry>
 281                         <varlistentry>
 282                                 <term><filename>kbrequest.target</filename></term>
 283                                 <listitem>
 284                                         <para>systemd starts this
 285                                         target whenever Alt+ArrowUp is
 286                                         pressed on the console. This
 287                                         is a good candidate to be
 288                                         aliased (symlinked) to
 289                                         <filename>rescue.target</filename>.</para>
 290                                 </listitem>
 291                         </varlistentry>
 292                         <varlistentry>
 293                                 <term><filename>kexec.target</filename></term>
 294                                 <listitem>
 295                                         <para>A special target unit
 296                                         for shutting down and rebooting the system via kexec.</para>
 297
 298                                         <para>Applications wanting to
 299                                         reboot the system with kexec should start
 300                                         this unit.</para>
 301                                 </listitem>
 302                         </varlistentry>
 303                         <varlistentry>
 304                                 <term><filename>local-fs.target</filename></term>
 305                                 <listitem>
 306                                         <para>systemd automatically
 307                                         adds dependencies of type
 308                                         After to all mount units that
 309                                         refer to local mount points
 310                                         for this target unit. In
 311                                         addition, systemd adds
 312                                         dependencies of type Wants to
 313                                         this target unit for those
 314                                         mounts listed in
 315                                         <filename>/etc/fstab</filename>
 316                                         that have the
 317                                         <option>auto</option> and
 318                                         <option>comment=systemd.mount</option>
 319                                         mount options set.</para>
 320
 321                                         <para>systemd automatically
 322                                         adds dependencies of type
 323                                         After for this target unit to
 324                                         all SysV init script service
 325                                         units with an LSB header
 326                                         referring to the
 327                                         <literal>$local_fs</literal>
 328                                         facility.</para>
 329                                 </listitem>
 330                         </varlistentry>
 331                         <varlistentry>
 332                                 <term><filename>local-fs-pre.target</filename></term>
 333                                 <listitem>
 334                                         <para>This target unit is
 335                                         automatically ordered before
 336                                         all local mount points marked
 337                                         with <option>auto</option>
 338                                         (see above). It can be used to
 339                                         execute certain units before
 340                                         all local mounts.</para>
 341                                 </listitem>
 342                         </varlistentry>
 343                         <varlistentry>
 344                                 <term><filename>mail-transfer-agent.target</filename></term>
 345                                 <listitem>
 346                                         <para>The mail transfer agent
 347                                         (MTA) service. Usually this
 348                                         should pull-in all units
 349                                         necessary for
 350                                         sending/receiving mails on the
 351                                         local host.</para>
 352
 353                                         <para>systemd automatically
 354                                         adds dependencies of type
 355                                         After for this target unit to
 356                                         all SysV init script service
 357                                         units with an LSB header
 358                                         referring to the
 359                                         <literal>$mail-transfer-agent</literal>
 360                                         or
 361                                         <literal>$mail-transport-agent</literal>
 362                                         facilities, for compatibility
 363                                         with Debian.</para>
 364                                 </listitem>
 365                         </varlistentry>
 366                         <varlistentry>
 367                                 <term><filename>multi-user.target</filename></term>
 368                                 <listitem>
 369                                         <para>A special target unit
 370                                         for setting up a multi-user
 371                                         system (non-graphical). This
 372                                         is pulled in by
 373                                         <filename>graphical.target</filename>.</para>
 374
 375                                         <para>Units that are needed
 376                                         for a multi-user system shall
 377                                         add Wants dependencies to
 378                                         this unit for their unit during
 379                                         installation.</para>
 380                                 </listitem>
 381                         </varlistentry>
 382                         <varlistentry>
 383                                 <term><filename>network.target</filename></term>
 384                                 <listitem>
 385                                         <para>systemd automatically
 386                                         adds dependencies of type
 387                                         After for this target unit to
 388                                         all SysV init script service
 389                                         units with an LSB header
 390                                         referring to the
 391                                         <literal>$network</literal>
 392                                         facility.</para>
 393                                 </listitem>
 394                         </varlistentry>
 395                         <varlistentry>
 396                                 <term><filename>nss-lookup.target</filename></term>
 397                                 <listitem>
 398                                         <para>A target that should be
 399                                         used as synchronization point
 400                                         for all host/network name
 401                                         service lookups. Note that
 402                                         this is independent of
 403                                         user/group name lookups for
 404                                         which
 405                                         <filename>nss-user-lookup.target</filename>
 406                                         should be used. systemd
 407                                         automatically adds
 408                                         dependencies of type After for
 409                                         this target unit to all SysV
 410                                         init script service units with
 411                                         an LSB header referring to the
 412                                         <literal>$named</literal>
 413                                         facility.</para>
 414                                 </listitem>
 415                         </varlistentry>
 416                         <varlistentry>
 417                                 <term><filename>nss-user-lookup.target</filename></term>
 418                                 <listitem>
 419                                         <para>A target that should be
 420                                         used as synchronization point
 421                                         for all user/group name
 422                                         service lookups. Note that
 423                                         this is independent of
 424                                         host/network name lookups for
 425                                         which
 426                                         <filename>nss-lookup.target</filename>
 427                                         should be used. </para>
 428                                 </listitem>
 429                         </varlistentry>
 430                         <varlistentry>
 431                                 <term><filename>poweroff.target</filename></term>
 432                                 <listitem>
 433                                         <para>A special target unit
 434                                         for shutting down and powering off the system.</para>
 435
 436                                         <para>Applications wanting to
 437                                         power off the system should start
 438                                         this unit.</para>
 439
 440                                         <para><filename>runlevel0.target</filename>
 441                                         is an alias for this target
 442                                         unit, for compatibility with SysV.</para>
 443                                 </listitem>
 444                         </varlistentry>
 445                         <varlistentry>
 446                                 <term><filename>reboot.target</filename></term>
 447                                 <listitem>
 448                                         <para>A special target unit
 449                                         for shutting down and rebooting the system.</para>
 450
 451                                         <para>Applications wanting to
 452                                         reboot the system should start
 453                                         this unit.</para>
 454
 455                                         <para><filename>runlevel6.target</filename>
 456                                         is an alias for this target
 457                                         unit, for compatibility with SysV.</para>
 458                                 </listitem>
 459                         </varlistentry>
 460                         <varlistentry>
 461                                 <term><filename>remote-fs.target</filename></term>
 462                                 <listitem>
 463                                         <para>Similar to
 464                                         <filename>local-fs.target</filename>,
 465                                         but for remote mount
 466                                         points.</para>
 467
 468                                         <para>systemd automatically
 469                                         adds dependencies of type
 470                                         After for this target unit to
 471                                         all SysV init script service
 472                                         units with an LSB header
 473                                         referring to the
 474                                         <literal>$remote_fs</literal>
 475                                         facility.</para>
 476                                 </listitem>
 477                         </varlistentry>
 478                         <varlistentry>
 479                                 <term><filename>remote-fs-pre.target</filename></term>
 480                                 <listitem>
 481                                         <para>This target unit is
 482                                         automatically ordered before
 483                                         all remote mount points marked
 484                                         with <option>auto</option>
 485                                         (see above). It can be used to
 486                                         execute certain units before
 487                                         all remote mounts.</para>
 488                                 </listitem>
 489                         </varlistentry>
 490                         <varlistentry>
 491                                 <term><filename>rescue.target</filename></term>
 492                                 <listitem>
 493                                         <para>A special target unit
 494                                         for setting up the base system
 495                                         and a rescue shell.</para>
 496
 497                                         <para><filename>runlevel1.target</filename>
 498                                         is an alias for this target
 499                                         unit, for compatibility with SysV.</para>
 500                                 </listitem>
 501                         </varlistentry>
 502                         <varlistentry>
 503                                 <term><filename>rpcbind.target</filename></term>
 504                                 <listitem>
 505                                         <para>systemd automatically
 506                                         adds dependencies of type
 507                                         After for this target unit to
 508                                         all SysV init script service
 509                                         units with an LSB header
 510                                         referring to the
 511                                         <literal>$rpcbind</literal>
 512                                         facility.</para>
 513                                 </listitem>
 514                         </varlistentry>
 515                         <varlistentry>
 516                                 <term><filename>runlevel2.target</filename></term>
 517                                 <listitem>
 518                                         <para>This is a target that is
 519                                         called whenever the SysV
 520                                         compatibility code asks for
 521                                         runlevel 2. It is a good idea
 522                                         to make this an alias for
 523                                         (i.e. symlink to)
 524                                         <filename>multi-user.target</filename>.</para>
 525                                 </listitem>
 526                         </varlistentry>
 527                         <varlistentry>
 528                                 <term><filename>runlevel3.target</filename></term>
 529                                 <listitem>
 530                                         <para>This is a target that is
 531                                         called whenever the SysV
 532                                         compatibility code asks for
 533                                         runlevel 3. It is a good idea
 534                                         to make this an alias for
 535                                         (i.e. symlink to)
 536                                         <filename>multi-user.target</filename>
 537                                         or
 538                                         <filename>graphical.target</filename>.</para>
 539                                 </listitem>
 540                         </varlistentry>
 541                         <varlistentry>
 542                                 <term><filename>runlevel4.target</filename></term>
 543                                 <listitem>
 544                                         <para>This is a target that is
 545                                         called whenever the SysV
 546                                         compatibility code asks for
 547                                         runlevel 4. It is a good idea
 548                                         to make this an alias for
 549                                         (i.e. symlink to)
 550                                         <filename>multi-user.target</filename>
 551                                         or
 552                                         <filename>graphical.target</filename>.</para>
 553                                 </listitem>
 554                         </varlistentry>
 555                         <varlistentry>
 556                                 <term><filename>runlevel5.target</filename></term>
 557                                 <listitem>
 558                                         <para>This is a target that is
 559                                         called whenever the SysV
 560                                         compatibility code asks for
 561                                         runlevel 5. It is a good idea
 562                                         to make this an alias for
 563                                         (i.e. symlink to)
 564                                         <filename>multi-user.target</filename>
 565                                         or
 566                                         <filename>graphical.target</filename>.</para>
 567                                 </listitem>
 568                         </varlistentry>
 569                         <varlistentry>
 570                                 <term><filename>shutdown.target</filename></term>
 571                                 <listitem>
 572                                         <para>A special target unit
 573                                         that terminates the services
 574                                         on system shutdown.</para>
 575
 576                                         <para>Services that shall be
 577                                         terminated on system shutdown
 578                                         shall add Conflicts
 579                                         dependencies to this unit for
 580                                         their service unit, which is
 581                                         implicitly done when
 582                                         <varname>DefaultDependencies=yes</varname>
 583                                         is set (the default).</para>
 584
 585                                         <para>systemd automatically
 586                                         adds dependencies of type
 587                                         Conflicts to this target unit
 588                                         for all SysV init script
 589                                         service units that shall be
 590                                         terminated in SysV runlevels 0
 591                                         or 6.</para>
 592                                 </listitem>
 593                         </varlistentry>
 594                         <varlistentry>
 595                                 <term><filename>sigpwr.target</filename></term>
 596                                 <listitem>
 597                                         <para>A special target that is
 598                                         started when systemd receives
 599                                         the SIGPWR process signal,
 600                                         which is normally sent by the
 601                                         kernel or UPS daemons when
 602                                         power fails.</para>
 603                                 </listitem>
 604                         </varlistentry>
 605                         <varlistentry>
 606                                 <term><filename>sleep.target</filename></term>
 607                                 <listitem>
 608                                         <para>A special target unit
 609                                         that is pulled in by
 610                                         <filename>suspend.target</filename>
 611                                         and
 612                                         <filename>hibernate.target</filename>
 613                                         and may be used to hook units
 614                                         into the sleep state
 615                                         logic.</para>
 616                                 </listitem>
 617                         </varlistentry>
 618                         <varlistentry>
 619                                 <term><filename>sockets.target</filename></term>
 620                                 <listitem>
 621                                         <para>A special target unit
 622                                         that sets up all service
 623                                         sockets.</para>
 624
 625                                         <para>Services that can be
 626                                         socket-activated shall add
 627                                         Wants dependencies to this
 628                                         unit for their socket unit
 629                                         during installation.</para>
 630                                 </listitem>
 631                         </varlistentry>
 632                         <varlistentry>
 633                                 <term><filename>suspend.target</filename></term>
 634                                 <listitem>
 635                                         <para>A special target unit
 636                                         for suspending the
 637                                         system. This pulls in
 638                                         <filename>sleep.target</filename>.</para>
 639                                 </listitem>
 640                         </varlistentry>
 641                         <varlistentry>
 642                                 <term><filename>swap.target</filename></term>
 643                                 <listitem>
 644                                         <para>Similar to
 645                                         <filename>local-fs.target</filename>, but for swap
 646                                         partitions and swap
 647                                         files.</para>
 648                                 </listitem>
 649                         </varlistentry>
 650                         <varlistentry>
 651                                 <term><filename>sysinit.target</filename></term>
 652                                 <listitem>
 653                                         <para>A special target unit
 654                                         covering early boot-up scripts.</para>
 655                                         <para>systemd automatically
 656                                         adds dependencies of the types
 657                                         Wants and After for all
 658                                         SysV service units configured
 659                                         for runlevels that are not 0
 660                                         to 6 to this target unit.
 661                                         This covers the special
 662                                         boot-up runlevels some
 663                                         distributions have, such as S
 664                                         or b.</para>
 665                                 </listitem>
 666                         </varlistentry>
 667                         <varlistentry>
 668                                 <term><filename>syslog.service</filename></term>
 669                                 <listitem>
 670                                         <para>The syslog service if
 671                                         any. Implementations should
 672                                         create a symlink from the
 673                                         actual syslog implementation
 674                                         to this generic name for
 675                                         activating it.</para>
 676                                 </listitem>
 677                         </varlistentry>
 678                         <varlistentry>
 679                                 <term><filename>syslog.socket</filename></term>
 680                                 <listitem>
 681                                         <para>The socket unit where
 682                                         syslog implementations should
 683                                         listen on. All userspace log
 684                                         messages will be made
 685                                         available on this
 686                                         socket.</para>
 687                                 </listitem>
 688                         </varlistentry>
 689                         <varlistentry>
 690                                 <term><filename>syslog.target</filename></term>
 691                                 <listitem>
 692                                         <para>systemd automatically
 693                                         adds dependencies of type
 694                                         After for this target unit to
 695                                         all SysV init script service
 696                                         units with an LSB header
 697                                         referring to the
 698                                         <literal>$syslog</literal>
 699                                         facility.</para>
 700                                 </listitem>
 701                         </varlistentry>
 702                         <varlistentry>
 703                                 <term><filename>time-sync.target</filename></term>
 704                                 <listitem>
 705                                         <para>systemd automatically
 706                                         adds dependencies of type
 707                                         After for this target unit to
 708                                         all SysV init script service
 709                                         units with an LSB header
 710                                         referring to the
 711                                         <literal>$time</literal>
 712                                         facility.</para>
 713                                 </listitem>
 714                         </varlistentry>
 715                         <varlistentry>
 716                                 <term><filename>umount.target</filename></term>
 717                                 <listitem>
 718                                         <para>A special target unit
 719                                         that umounts all mount and
 720                                         automount points on system
 721                                         shutdown.</para>
 722
 723                                         <para>Mounts that shall be
 724                                         unmounted on system shutdown
 725                                         shall add Conflicts
 726                                         dependencies to this unit for
 727                                         their mount unit, which is
 728                                         implicitly done when
 729                                         <varname>DefaultDependencies=yes</varname>
 730                                         is set (the default).</para>
 731                                 </listitem>
 732                         </varlistentry>
 733                 </variablelist>
 734         </refsect1>
 735
 736         <refsect1>
 737                 <title>Special User Units</title>
 738
 739                 <para>When systemd runs as a user instance, the
 740                 following special units are available, which have
 741                 similar definitions as their system counterparts:
 742                 <filename>default.target</filename>,
 743                 <filename>shutdown.target</filename>,
 744                 <filename>sockets.target</filename></para>
 745
 746                 <para>In addition the following special unit is
 747                 understood only when systemd runs as service instance:</para>
 748
 749                 <variablelist>
 750                         <varlistentry>
 751                                 <term><filename>exit.service</filename></term>
 752                                 <listitem>
 753                                         <para>A special service unit
 754                                         for shutting down the
 755                                         user service manager.</para>
 756
 757                                         <para>Applications wanting to
 758                                         terminate the user service
 759                                         manager should start this
 760                                         unit. If systemd receives
 761                                         SIGTERM or SIGINT when running
 762                                         as user service daemon it will
 763                                         start this unit.</para>
 764
 765                                         <para>Normally, this pulls in
 766                                         <filename>shutdown.target</filename>
 767                                         which in turn should be
 768                                         conflicted by all units that
 769                                         want to be shut down on
 770                                         user service manager exit.</para>
 771                                 </listitem>
 772                         </varlistentry>
 773                 </variablelist>
 774         </refsect1>
 775
 776         <refsect1>
 777                   <title>See Also</title>
 778                   <para>
 779                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 780                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 781                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 782                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 783                           <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 784                   </para>
 785         </refsect1>
 786
 787 </refentry>