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">
   4
   5 <!--
   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
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
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  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  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>bluetooth.target</filename>,
  53                 <filename>ctrl-alt-del.target</filename>,
  54                 <filename>cryptsetup.target</filename>,
  55                 <filename>dbus.service</filename>,
  56                 <filename>dbus.socket</filename>,
  57                 <filename>default.target</filename>,
  58                 <filename>display-manager.service</filename>,
  59                 <filename>emergency.target</filename>,
  60                 <filename>exit.target</filename>,
  61                 <filename>final.target</filename>,
  62                 <filename>getty.target</filename>,
  63                 <filename>graphical.target</filename>,
  64                 <filename>halt.target</filename>,
  65                 <filename>hibernate.target</filename>,
  66                 <filename>hybrid-sleep.target</filename>,
  67                 <filename>kbrequest.target</filename>,
  68                 <filename>kexec.target</filename>,
  69                 <filename>local-fs.target</filename>,
  70                 <filename>local-fs-pre.target</filename>,
  71                 <filename>multi-user.target</filename>,
  72                 <filename>network.target</filename>,
  73                 <filename>nss-lookup.target</filename>,
  74                 <filename>nss-user-lookup.target</filename>,
  75                 <filename>poweroff.target</filename>,
  76                 <filename>printer.target</filename>,
  77                 <filename>reboot.target</filename>,
  78                 <filename>remote-fs.target</filename>,
  79                 <filename>remote-fs-pre.target</filename>,
  80                 <filename>rescue.target</filename>,
  81                 <filename>rpcbind.target</filename>,
  82                 <filename>runlevel2.target</filename>,
  83                 <filename>runlevel3.target</filename>,
  84                 <filename>runlevel4.target</filename>,
  85                 <filename>runlevel5.target</filename>,
  86                 <filename>shutdown.target</filename>,
  87                 <filename>sigpwr.target</filename>,
  88                 <filename>sleep.target</filename>,
  89                 <filename>smartcard.target</filename>,
  90                 <filename>sockets.target</filename>,
  91                 <filename>sound.target</filename>,
  92                 <filename>suspend.target</filename>,
  93                 <filename>swap.target</filename>,
  94                 <filename>sysinit.target</filename>,
  95                 <filename>syslog.socket</filename>,
  96                 <filename>syslog.target</filename>,
  97                 <filename>system-update.target</filename>,
  98                 <filename>time-sync.target</filename>,
  99                 <filename>umount.target</filename></para>
 100         </refsynopsisdiv>
 101
 102         <refsect1>
 103                 <title>Description</title>
 104
 105                 <para>A few units are treated specially by
 106                 systemd. They have special internal semantics and
 107                 cannot be renamed.</para>
 108         </refsect1>
 109
 110         <refsect1>
 111                 <title>Special System Units</title>
 112
 113                 <variablelist>
 114                         <varlistentry>
 115                                 <term><filename>basic.target</filename></term>
 116                                 <listitem>
 117                                         <para>A special target unit
 118                                         covering early boot-up.</para>
 119                                         <para>systemd automatically
 120                                         adds dependencies of the types
 121                                         Requires and After for this
 122                                         target unit to all SysV
 123                                         service units configured for
 124                                         runlevel 1 to 5.</para>
 125                                         <para>Usually this should pull-in
 126                                         all sockets, mount points,
 127                                         swap devices and other basic
 128                                         initialization necessary for
 129                                         the general purpose
 130                                         daemons. Most normal daemons
 131                                         should have dependencies of
 132                                         type After and Requires on
 133                                         this unit.</para>
 134                                 </listitem>
 135                         </varlistentry>
 136                         <varlistentry>
 137                                 <term><filename>bluetooth.target</filename></term>
 138                                 <listitem>
 139                                         <para>This target is started
 140                                         automatically as soon as a
 141                                         bluetooth controller is
 142                                         plugged in or becomes
 143                                         available at boot.</para>
 144                                 </listitem>
 145                         </varlistentry>
 146                         <varlistentry>
 147                                 <term><filename>ctrl-alt-del.target</filename></term>
 148                                 <listitem>
 149                                         <para>systemd starts this
 150                                         target whenever
 151                                         Control+Alt+Del is pressed on
 152                                         the console. Usually this
 153                                         should be aliased (symlinked)
 154                                         to
 155                                         <filename>reboot.target</filename>.</para>
 156                                 </listitem>
 157                         </varlistentry>
 158                         <varlistentry>
 159                                 <term><filename>cryptsetup.target</filename></term>
 160                                 <listitem>
 161                                         <para>A target that pulls in
 162                                         setup services for all
 163                                         encrypted block
 164                                         devices.</para>
 165                                 </listitem>
 166                         </varlistentry>
 167                         <varlistentry>
 168                                 <term><filename>dbus.service</filename></term>
 169                                 <listitem>
 170                                         <para>A special unit for the
 171                                         D-Bus system bus. As soon as
 172                                         this service is fully started
 173                                         up systemd will connect to it
 174                                         and register its
 175                                         service.</para>
 176                                 </listitem>
 177                         </varlistentry>
 178                         <varlistentry>
 179                                 <term><filename>dbus.socket</filename></term>
 180                                 <listitem>
 181                                         <para>A special unit for the
 182                                         D-Bus system bus socket. All
 183                                         units with
 184                                         <literal>Type=dbus</literal>
 185                                         automatically gain a
 186                                         dependency on this
 187                                         unit.</para>
 188                                 </listitem>
 189                         </varlistentry>
 190                         <varlistentry>
 191                                 <term><filename>default.target</filename></term>
 192                                 <listitem>
 193                                         <para>The default unit systemd
 194                                         starts at bootup. Usually this
 195                                         should be aliased (symlinked)
 196                                         to
 197                                         <filename>multi-user.target</filename>
 198                                         or
 199                                         <filename>graphical.target</filename>.</para>
 200                                         <para>The default unit systemd
 201                                         starts at bootup can be
 202                                         overridden with the
 203                                         <varname>systemd.unit=</varname>
 204                                         kernel command line option.</para>
 205                                 </listitem>
 206                         </varlistentry>
 207                         <varlistentry>
 208                                 <term><filename>display-manager.service</filename></term>
 209                                 <listitem>
 210                                         <para>The display manager
 211                                         service. Usually this should
 212                                         be aliased (symlinked) to
 213                                         <filename>gdm.service</filename>
 214                                         or a similar display manager
 215                                         service.</para>
 216                                 </listitem>
 217                         </varlistentry>
 218                         <varlistentry>
 219                                 <term><filename>emergency.target</filename></term>
 220                                 <listitem>
 221                                         <para>A special target unit
 222                                         that starts an emergency
 223                                         shell on the main
 224                                         console. This unit is supposed
 225                                         to be used with the kernel
 226                                         command line option
 227                                         <varname>systemd.unit=</varname>
 228                                         and has otherwise little use.
 229                                         </para>
 230                                 </listitem>
 231                         </varlistentry>
 232                         <varlistentry>
 233                                 <term><filename>final.target</filename></term>
 234                                 <listitem>
 235                                         <para>A special target unit
 236                                         that is used during the
 237                                         shutdown logic and may be used
 238                                         to pull in late services after
 239                                         all normal services are
 240                                         already terminated and all
 241                                         mounts unmounted.
 242                                         </para>
 243                                 </listitem>
 244                         </varlistentry>
 245                         <varlistentry>
 246                                 <term><filename>getty.target</filename></term>
 247                                 <listitem>
 248                                         <para>A special target unit
 249                                         that pulls in all local TTY
 250                                         <filename>getty</filename> instances.
 251                                         </para>
 252                                 </listitem>
 253                         </varlistentry>
 254                         <varlistentry>
 255                                 <term><filename>graphical.target</filename></term>
 256                                 <listitem>
 257                                         <para>A special target unit
 258                                         for setting up a graphical
 259                                         login screen. This pulls in
 260                                         <filename>multi-user.target</filename>.</para>
 261
 262                                         <para>Units that are needed
 263                                         for graphical login shall add
 264                                         Wants dependencies for their
 265                                         unit to this unit (or
 266                                         <filename>multi-user.target</filename>)
 267                                         during installation.</para>
 268                                 </listitem>
 269                         </varlistentry>
 270                         <varlistentry>
 271                                 <term><filename>hibernate.target</filename></term>
 272                                 <listitem>
 273                                         <para>A special target unit
 274                                         for hibernating the
 275                                         system. This pulls in
 276                                         <filename>sleep.target</filename>.</para>
 277                                 </listitem>
 278                         </varlistentry>
 279                         <varlistentry>
 280                                 <term><filename>hybrid-sleep.target</filename></term>
 281                                 <listitem>
 282                                         <para>A special target unit
 283                                         for hibernating and suspending the
 284                                         system at the same time. This pulls in
 285                                         <filename>sleep.target</filename>.</para>
 286                                 </listitem>
 287                         </varlistentry>
 288                         <varlistentry>
 289                                 <term><filename>halt.target</filename></term>
 290                                 <listitem>
 291                                         <para>A special target unit
 292                                         for shutting down and halting the system.</para>
 293
 294                                         <para>Applications wanting to
 295                                         halt the system should start
 296                                         this unit.</para>
 297                                 </listitem>
 298                         </varlistentry>
 299                         <varlistentry>
 300                                 <term><filename>kbrequest.target</filename></term>
 301                                 <listitem>
 302                                         <para>systemd starts this
 303                                         target whenever Alt+ArrowUp is
 304                                         pressed on the console. This
 305                                         is a good candidate to be
 306                                         aliased (symlinked) to
 307                                         <filename>rescue.target</filename>.</para>
 308                                 </listitem>
 309                         </varlistentry>
 310                         <varlistentry>
 311                                 <term><filename>kexec.target</filename></term>
 312                                 <listitem>
 313                                         <para>A special target unit
 314                                         for shutting down and rebooting the system via kexec.</para>
 315
 316                                         <para>Applications wanting to
 317                                         reboot the system with kexec should start
 318                                         this unit.</para>
 319                                 </listitem>
 320                         </varlistentry>
 321                         <varlistentry>
 322                                 <term><filename>local-fs.target</filename></term>
 323                                 <listitem>
 324                                         <para>systemd automatically
 325                                         adds dependencies of type
 326                                         After to all mount units that
 327                                         refer to local mount points
 328                                         for this target unit. In
 329                                         addition, systemd adds
 330                                         dependencies of type Wants to
 331                                         this target unit for those
 332                                         mounts listed in
 333                                         <filename>/etc/fstab</filename>
 334                                         that have the
 335                                         <option>auto</option> and
 336                                         <option>comment=systemd.mount</option>
 337                                         mount options set.</para>
 338
 339                                         <para>systemd automatically
 340                                         adds dependencies of type
 341                                         After for this target unit to
 342                                         all SysV init script service
 343                                         units with an LSB header
 344                                         referring to the
 345                                         <literal>$local_fs</literal>
 346                                         facility.</para>
 347                                 </listitem>
 348                         </varlistentry>
 349                         <varlistentry>
 350                                 <term><filename>local-fs-pre.target</filename></term>
 351                                 <listitem>
 352                                         <para>This target unit is
 353                                         automatically ordered before
 354                                         all local mount points marked
 355                                         with <option>auto</option>
 356                                         (see above). It can be used to
 357                                         execute certain units before
 358                                         all local mounts.</para>
 359                                 </listitem>
 360                         </varlistentry>
 361                         <varlistentry>
 362                                 <term><filename>multi-user.target</filename></term>
 363                                 <listitem>
 364                                         <para>A special target unit
 365                                         for setting up a multi-user
 366                                         system (non-graphical). This
 367                                         is pulled in by
 368                                         <filename>graphical.target</filename>.</para>
 369
 370                                         <para>Units that are needed
 371                                         for a multi-user system shall
 372                                         add Wants dependencies to
 373                                         this unit for their unit during
 374                                         installation.</para>
 375                                 </listitem>
 376                         </varlistentry>
 377                         <varlistentry>
 378                                 <term><filename>network.target</filename></term>
 379                                 <listitem>
 380                                         <para>systemd automatically
 381                                         adds dependencies of type
 382                                         After for this target unit to
 383                                         all SysV init script service
 384                                         units with an LSB header
 385                                         referring to the
 386                                         <literal>$network</literal>
 387                                         facility.</para>
 388
 389                                         <para>This unit is supposed to
 390                                         indicate when the network is
 391                                         "up", but it is only very
 392                                         loosely defined what that is
 393                                         supposed to mean. Also see <ulink
 394                                         url="http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running
 395                                         Services After the Network is
 396                                         up</ulink> for more
 397                                         information.</para>
 398                                 </listitem>
 399                         </varlistentry>
 400                         <varlistentry>
 401                                 <term><filename>nss-lookup.target</filename></term>
 402                                 <listitem>
 403                                         <para>A target that should be
 404                                         used as synchronization point
 405                                         for all host/network name
 406                                         service lookups. Note that
 407                                         this is independent of
 408                                         user/group name lookups for
 409                                         which
 410                                         <filename>nss-user-lookup.target</filename>
 411                                         should be used. systemd
 412                                         automatically adds
 413                                         dependencies of type After for
 414                                         this target unit to all SysV
 415                                         init script service units with
 416                                         an LSB header referring to the
 417                                         <literal>$named</literal>
 418                                         facility.</para>
 419                                 </listitem>
 420                         </varlistentry>
 421                         <varlistentry>
 422                                 <term><filename>nss-user-lookup.target</filename></term>
 423                                 <listitem>
 424                                         <para>A target that should be
 425                                         used as synchronization point
 426                                         for all user/group name
 427                                         service lookups. Note that
 428                                         this is independent of
 429                                         host/network name lookups for
 430                                         which
 431                                         <filename>nss-lookup.target</filename>
 432                                         should be used. </para>
 433                                 </listitem>
 434                         </varlistentry>
 435                         <varlistentry>
 436                                 <term><filename>poweroff.target</filename></term>
 437                                 <listitem>
 438                                         <para>A special target unit
 439                                         for shutting down and powering off the system.</para>
 440
 441                                         <para>Applications wanting to
 442                                         power off the system should start
 443                                         this unit.</para>
 444
 445                                         <para><filename>runlevel0.target</filename>
 446                                         is an alias for this target
 447                                         unit, for compatibility with SysV.</para>
 448                                 </listitem>
 449                         </varlistentry>
 450                         <varlistentry>
 451                                 <term><filename>printer.target</filename></term>
 452                                 <listitem>
 453                                         <para>This target is started
 454                                         automatically as soon as a
 455                                         printer is plugged in or
 456                                         becomes available at
 457                                         boot.</para>
 458                                 </listitem>
 459                         </varlistentry>
 460                         <varlistentry>
 461                                 <term><filename>reboot.target</filename></term>
 462                                 <listitem>
 463                                         <para>A special target unit
 464                                         for shutting down and rebooting the system.</para>
 465
 466                                         <para>Applications wanting to
 467                                         reboot the system should start
 468                                         this unit.</para>
 469
 470                                         <para><filename>runlevel6.target</filename>
 471                                         is an alias for this target
 472                                         unit, for compatibility with SysV.</para>
 473                                 </listitem>
 474                         </varlistentry>
 475                         <varlistentry>
 476                                 <term><filename>remote-fs.target</filename></term>
 477                                 <listitem>
 478                                         <para>Similar to
 479                                         <filename>local-fs.target</filename>,
 480                                         but for remote mount
 481                                         points.</para>
 482
 483                                         <para>systemd automatically
 484                                         adds dependencies of type
 485                                         After for this target unit to
 486                                         all SysV init script service
 487                                         units with an LSB header
 488                                         referring to the
 489                                         <literal>$remote_fs</literal>
 490                                         facility.</para>
 491                                 </listitem>
 492                         </varlistentry>
 493                         <varlistentry>
 494                                 <term><filename>remote-fs-pre.target</filename></term>
 495                                 <listitem>
 496                                         <para>This target unit is
 497                                         automatically ordered before
 498                                         all remote mount points marked
 499                                         with <option>auto</option>
 500                                         (see above). It can be used to
 501                                         execute certain units before
 502                                         all remote mounts.</para>
 503                                 </listitem>
 504                         </varlistentry>
 505                         <varlistentry>
 506                                 <term><filename>rescue.target</filename></term>
 507                                 <listitem>
 508                                         <para>A special target unit
 509                                         for setting up the base system
 510                                         and a rescue shell.</para>
 511
 512                                         <para><filename>runlevel1.target</filename>
 513                                         is an alias for this target
 514                                         unit, for compatibility with SysV.</para>
 515                                 </listitem>
 516                         </varlistentry>
 517                         <varlistentry>
 518                                 <term><filename>rpcbind.target</filename></term>
 519                                 <listitem>
 520                                         <para>systemd automatically
 521                                         adds dependencies of type
 522                                         After for this target unit to
 523                                         all SysV init script service
 524                                         units with an LSB header
 525                                         referring to the
 526                                         <literal>$portmap</literal>
 527                                         facility.</para>
 528                                 </listitem>
 529                         </varlistentry>
 530                         <varlistentry>
 531                                 <term><filename>runlevel2.target</filename></term>
 532                                 <term><filename>runlevel3.target</filename></term>
 533                                 <term><filename>runlevel4.target</filename></term>
 534                                 <term><filename>runlevel5.target</filename></term>
 535                                 <listitem>
 536                                         <para>These are targets that
 537                                         are called whenever the SysV
 538                                         compatibility code asks for
 539                                         runlevel 2, 3, 4, 5,
 540                                         respectively. It is a good
 541                                         idea to make this an alias for
 542                                         (i.e. symlink to)
 543                                         <filename>multi-user.target</filename>
 544                                         (for runlevel 2) or
 545                                         <filename>graphical.target</filename>
 546                                         (the others).</para>
 547                                 </listitem>
 548                         </varlistentry>
 549                         <varlistentry>
 550                                 <term><filename>shutdown.target</filename></term>
 551                                 <listitem>
 552                                         <para>A special target unit
 553                                         that terminates the services
 554                                         on system shutdown.</para>
 555
 556                                         <para>Services that shall be
 557                                         terminated on system shutdown
 558                                         shall add Conflicts
 559                                         dependencies to this unit for
 560                                         their service unit, which is
 561                                         implicitly done when
 562                                         <varname>DefaultDependencies=yes</varname>
 563                                         is set (the default).</para>
 564
 565                                         <para>systemd automatically
 566                                         adds dependencies of type
 567                                         Conflicts to this target unit
 568                                         for all SysV init script
 569                                         service units that shall be
 570                                         terminated in SysV runlevels 0
 571                                         or 6.</para>
 572                                 </listitem>
 573                         </varlistentry>
 574                         <varlistentry>
 575                                 <term><filename>sigpwr.target</filename></term>
 576                                 <listitem>
 577                                         <para>A special target that is
 578                                         started when systemd receives
 579                                         the SIGPWR process signal,
 580                                         which is normally sent by the
 581                                         kernel or UPS daemons when
 582                                         power fails.</para>
 583                                 </listitem>
 584                         </varlistentry>
 585                         <varlistentry>
 586                                 <term><filename>sleep.target</filename></term>
 587                                 <listitem>
 588                                         <para>A special target unit
 589                                         that is pulled in by
 590                                         <filename>suspend.target</filename>,
 591                                         <filename>hibernate.target</filename> and <filename>hybrid-sleep.target</filename>
 592                                         and may be used to hook units
 593                                         into the sleep state
 594                                         logic.</para>
 595                                 </listitem>
 596                         </varlistentry>
 597                         <varlistentry>
 598                                 <term><filename>smartcard.target</filename></term>
 599                                 <listitem>
 600                                         <para>This target is started
 601                                         automatically as soon as a
 602                                         smartcard controller is
 603                                         plugged in or becomes
 604                                         available at boot.</para>
 605                                 </listitem>
 606                         </varlistentry>
 607                         <varlistentry>
 608                                 <term><filename>sockets.target</filename></term>
 609                                 <listitem>
 610                                         <para>A special target unit
 611                                         that sets up all service
 612                                         sockets.</para>
 613
 614                                         <para>Services that can be
 615                                         socket-activated shall add
 616                                         Wants dependencies to this
 617                                         unit for their socket unit
 618                                         during installation.</para>
 619                                 </listitem>
 620                         </varlistentry>
 621                         <varlistentry>
 622                                 <term><filename>sound.target</filename></term>
 623                                 <listitem>
 624                                         <para>This target is started
 625                                         automatically as soon as a
 626                                         sound card is plugged in or
 627                                         becomes available at
 628                                         boot.</para>
 629                                 </listitem>
 630                         </varlistentry>
 631                         <varlistentry>
 632                                 <term><filename>suspend.target</filename></term>
 633                                 <listitem>
 634                                         <para>A special target unit
 635                                         for suspending the
 636                                         system. This pulls in
 637                                         <filename>sleep.target</filename>.</para>
 638                                 </listitem>
 639                         </varlistentry>
 640                         <varlistentry>
 641                                 <term><filename>swap.target</filename></term>
 642                                 <listitem>
 643                                         <para>Similar to
 644                                         <filename>local-fs.target</filename>, but for swap
 645                                         partitions and swap
 646                                         files.</para>
 647                                 </listitem>
 648                         </varlistentry>
 649                         <varlistentry>
 650                                 <term><filename>sysinit.target</filename></term>
 651                                 <listitem>
 652                                         <para>A special target unit
 653                                         covering early boot-up scripts.</para>
 654                                         <para>systemd automatically
 655                                         adds dependencies of the types
 656                                         Wants and After for all
 657                                         SysV service units configured
 658                                         for runlevels that are not 0
 659                                         to 6 to this target unit.
 660                                         This covers the special
 661                                         boot-up runlevels some
 662                                         distributions have, such as S
 663                                         or b.</para>
 664                                 </listitem>
 665                         </varlistentry>
 666                         <varlistentry>
 667                                 <term><filename>syslog.socket</filename></term>
 668                                 <listitem>
 669                                         <para>The socket unit
 670                                         syslog implementations should
 671                                         listen on. All userspace log
 672                                         messages will be made
 673                                         available on this socket. For
 674                                         more information about syslog
 675                                         integration, please consult
 676                                         the <ulink
 677                                         url="http://www.freedesktop.org/wiki/Software/systemd/syslog">Syslog
 678                                         Interface</ulink>
 679                                         document.</para>
 680                                 </listitem>
 681                         </varlistentry>
 682                         <varlistentry>
 683                                 <term><filename>syslog.target</filename></term>
 684                                 <listitem>
 685                                         <para>systemd automatically
 686                                         adds dependencies of type
 687                                         After for this target unit to
 688                                         all SysV init script service
 689                                         units with an LSB header
 690                                         referring to the
 691                                         <literal>$syslog</literal>
 692                                         facility.</para>
 693                                 </listitem>
 694                         </varlistentry>
 695                         <varlistentry>
 696                                 <term><filename>system-update.target</filename></term>
 697                                 <listitem>
 698                                         <para>A special target unit
 699                                         that is used for off-line
 700                                         system updates.
 701                                         <citerefentry><refentrytitle>systemd-system-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 702                                         will redirect the boot process
 703                                         to this target if
 704                                         <filename>/system-update</filename>
 705                                         exists. For more information
 706                                         see the <ulink
 707                                         url="http://freedesktop.org/wiki/Software/systemd/SystemUpdates">System
 708                                         Updates
 709                                         Specification</ulink>.</para>
 710                                 </listitem>
 711                         </varlistentry>
 712                         <varlistentry>
 713                                 <term><filename>time-sync.target</filename></term>
 714                                 <listitem>
 715                                         <para>systemd automatically
 716                                         adds dependencies of type
 717                                         After for this target unit to
 718                                         all SysV init script service
 719                                         units with an LSB header
 720                                         referring to the
 721                                         <literal>$time</literal>
 722                                         facility.</para>
 723                                 </listitem>
 724                         </varlistentry>
 725                         <varlistentry>
 726                                 <term><filename>umount.target</filename></term>
 727                                 <listitem>
 728                                         <para>A special target unit
 729                                         that umounts all mount and
 730                                         automount points on system
 731                                         shutdown.</para>
 732
 733                                         <para>Mounts that shall be
 734                                         unmounted on system shutdown
 735                                         shall add Conflicts
 736                                         dependencies to this unit for
 737                                         their mount unit, which is
 738                                         implicitly done when
 739                                         <varname>DefaultDependencies=yes</varname>
 740                                         is set (the default).</para>
 741                                 </listitem>
 742                         </varlistentry>
 743
 744                 </variablelist>
 745         </refsect1>
 746
 747         <refsect1>
 748                 <title>Special User Units</title>
 749
 750                 <para>When systemd runs as a user instance, the
 751                 following special units are available, which have
 752                 similar definitions as their system counterparts:
 753                 <filename>default.target</filename>,
 754                 <filename>shutdown.target</filename>,
 755                 <filename>sockets.target</filename></para>
 756
 757                 <para>In addition the following special unit is
 758                 understood only when systemd runs as service instance:</para>
 759
 760                 <variablelist>
 761                         <varlistentry>
 762                                 <term><filename>exit.target</filename></term>
 763                                 <listitem>
 764                                         <para>A special service unit
 765                                         for shutting down the
 766                                         user service manager.</para>
 767
 768                                         <para>Applications wanting to
 769                                         terminate the user service
 770                                         manager should start this
 771                                         unit. If systemd receives
 772                                         SIGTERM or SIGINT when running
 773                                         as user service daemon it will
 774                                         start this unit.</para>
 775
 776                                         <para>Normally, this pulls in
 777                                         <filename>shutdown.target</filename>
 778                                         which in turn should be
 779                                         conflicted by all units that
 780                                         want to be shut down on
 781                                         user service manager exit.</para>
 782                                 </listitem>
 783                         </varlistentry>
 784                 </variablelist>
 785         </refsect1>
 786
 787         <refsect1>
 788                   <title>See Also</title>
 789                   <para>
 790                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 791                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 792                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 793                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 794                           <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 795                           <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 796                   </para>
 797         </refsect1>
 798
 799 </refentry>