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