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
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   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
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  11   under the terms of the GNU Lesser General Public License as published by
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  13   (at your option) any later version.
  14
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  18   Lesser General Public License for more details.
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  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>paths.target</filename>,
  77                 <filename>poweroff.target</filename>,
  78                 <filename>printer.target</filename>,
  79                 <filename>reboot.target</filename>,
  80                 <filename>remote-fs.target</filename>,
  81                 <filename>remote-fs-pre.target</filename>,
  82                 <filename>remote-fs-setup.target</filename>,
  83                 <filename>rescue.target</filename>,
  84                 <filename>initrd-root-fs.target</filename>,
  85                 <filename>rpcbind.target</filename>,
  86                 <filename>runlevel2.target</filename>,
  87                 <filename>runlevel3.target</filename>,
  88                 <filename>runlevel4.target</filename>,
  89                 <filename>runlevel5.target</filename>,
  90                 <filename>shutdown.target</filename>,
  91                 <filename>sigpwr.target</filename>,
  92                 <filename>sleep.target</filename>,
  93                 <filename>smartcard.target</filename>,
  94                 <filename>sockets.target</filename>,
  95                 <filename>sound.target</filename>,
  96                 <filename>suspend.target</filename>,
  97                 <filename>swap.target</filename>,
  98                 <filename>sysinit.target</filename>,
  99                 <filename>syslog.socket</filename>,
 100                 <filename>system-update.target</filename>,
 101                 <filename>time-sync.target</filename>,
 102                 <filename>timers.target</filename>,
 103                 <filename>umount.target</filename></para>
 104         </refsynopsisdiv>
 105
 106         <refsect1>
 107                 <title>Description</title>
 108
 109                 <para>A few units are treated specially by
 110                 systemd. They have special internal semantics and
 111                 cannot be renamed.</para>
 112         </refsect1>
 113
 114         <refsect1>
 115                 <title>Special System Units</title>
 116
 117                 <variablelist>
 118                         <varlistentry>
 119                                 <term><filename>basic.target</filename></term>
 120                                 <listitem>
 121                                         <para>A special target unit
 122                                         covering basic boot-up.</para>
 123                                         <para>systemd automatically
 124                                         adds dependencies of the types
 125                                         <varname>Requires=</varname>
 126                                         and <varname>After=</varname>
 127                                         for this target unit to all
 128                                         services (except for those
 129                                         with
 130                                         <varname>DefaultDependencies=no</varname>).</para>
 131
 132                                         <para>Usually this should
 133                                         pull-in all mount points, swap
 134                                         devices, sockets, timers, and
 135                                         path units and other basic
 136                                         initialization necessary for
 137                                         general purpose
 138                                         daemons.</para>
 139                                 </listitem>
 140                         </varlistentry>
 141                         <varlistentry>
 142                                 <term><filename>ctrl-alt-del.target</filename></term>
 143                                 <listitem>
 144                                         <para>systemd starts this
 145                                         target whenever
 146                                         Control+Alt+Del is pressed on
 147                                         the console. Usually this
 148                                         should be aliased (symlinked)
 149                                         to
 150                                         <filename>reboot.target</filename>.</para>
 151                                 </listitem>
 152                         </varlistentry>
 153                         <varlistentry>
 154                                 <term><filename>cryptsetup.target</filename></term>
 155                                 <listitem>
 156                                         <para>A target that pulls in
 157                                         setup services for all
 158                                         encrypted block
 159                                         devices.</para>
 160                                 </listitem>
 161                         </varlistentry>
 162                         <varlistentry>
 163                                 <term><filename>dbus.service</filename></term>
 164                                 <listitem>
 165                                         <para>A special unit for the
 166                                         D-Bus bus daemon. As soon as
 167                                         this service is fully started
 168                                         up systemd will connect to it
 169                                         and register its
 170                                         service.</para>
 171                                 </listitem>
 172                         </varlistentry>
 173                         <varlistentry>
 174                                 <term><filename>dbus.socket</filename></term>
 175                                 <listitem>
 176                                         <para>A special unit for the
 177                                         D-Bus system bus socket. All
 178                                         units with
 179                                         <varname>Type=dbus</varname>
 180                                         automatically gain a
 181                                         dependency on this
 182                                         unit.</para>
 183                                 </listitem>
 184                         </varlistentry>
 185                         <varlistentry>
 186                                 <term><filename>default.target</filename></term>
 187                                 <listitem>
 188                                         <para>The default unit systemd
 189                                         starts at bootup. Usually this
 190                                         should be aliased (symlinked)
 191                                         to
 192                                         <filename>multi-user.target</filename>
 193                                         or
 194                                         <filename>graphical.target</filename>.</para>
 195
 196                                         <para>The default unit systemd
 197                                         starts at bootup can be
 198                                         overridden with the
 199                                         <varname>systemd.unit=</varname>
 200                                         kernel command line option.</para>
 201                                 </listitem>
 202                         </varlistentry>
 203                         <varlistentry>
 204                                 <term><filename>display-manager.service</filename></term>
 205                                 <listitem>
 206                                         <para>The display manager
 207                                         service. Usually this should
 208                                         be aliased (symlinked) to
 209                                         <filename>gdm.service</filename>
 210                                         or a similar display manager
 211                                         service.</para>
 212                                 </listitem>
 213                         </varlistentry>
 214                         <varlistentry>
 215                                 <term><filename>emergency.target</filename></term>
 216                                 <listitem>
 217                                         <para>A special target unit
 218                                         that starts an emergency
 219                                         shell on the main
 220                                         console. This unit is supposed
 221                                         to be used with the kernel
 222                                         command line option
 223                                         <varname>systemd.unit=</varname>
 224                                         and has otherwise little use.
 225                                         </para>
 226                                 </listitem>
 227                         </varlistentry>
 228                         <varlistentry>
 229                                 <term><filename>final.target</filename></term>
 230                                 <listitem>
 231                                         <para>A special target unit
 232                                         that is used during the
 233                                         shutdown logic and may be used
 234                                         to pull in late services after
 235                                         all normal services are
 236                                         already terminated and all
 237                                         mounts unmounted.
 238                                         </para>
 239                                 </listitem>
 240                         </varlistentry>
 241                         <varlistentry>
 242                                 <term><filename>getty.target</filename></term>
 243                                 <listitem>
 244                                         <para>A special target unit
 245                                         that pulls in statically
 246                                         configured local TTY
 247                                         <filename>getty</filename>
 248                                         instances.
 249                                         </para>
 250                                 </listitem>
 251                         </varlistentry>
 252                         <varlistentry>
 253                                 <term><filename>graphical.target</filename></term>
 254                                 <listitem>
 255                                         <para>A special target unit
 256                                         for setting up a graphical
 257                                         login screen. This pulls in
 258                                         <filename>multi-user.target</filename>.</para>
 259
 260                                         <para>Units that are needed
 261                                         for graphical logins shall add
 262                                         <varname>Wants=</varname>
 263                                         dependencies for their unit to
 264                                         this unit (or
 265                                         <filename>multi-user.target</filename>)
 266                                         during installation. This is
 267                                         best configured via
 268                                         <varname>WantedBy=graphical.target</varname>
 269                                         in the unit's
 270                                         <literal>[Install]</literal>
 271                                         section.</para>
 272                                 </listitem>
 273                         </varlistentry>
 274                         <varlistentry>
 275                                 <term><filename>hibernate.target</filename></term>
 276                                 <listitem>
 277                                         <para>A special target unit
 278                                         for hibernating the
 279                                         system. This pulls in
 280                                         <filename>sleep.target</filename>.</para>
 281                                 </listitem>
 282                         </varlistentry>
 283                         <varlistentry>
 284                                 <term><filename>hybrid-sleep.target</filename></term>
 285                                 <listitem>
 286                                         <para>A special target unit
 287                                         for hibernating and suspending the
 288                                         system at the same time. This pulls in
 289                                         <filename>sleep.target</filename>.</para>
 290                                 </listitem>
 291                         </varlistentry>
 292                         <varlistentry>
 293                                 <term><filename>halt.target</filename></term>
 294                                 <listitem>
 295                                         <para>A special target unit
 296                                         for shutting down and halting
 297                                         the system. Note that this
 298                                         target is distinct from
 299                                         <filename>poweroff.target</filename>
 300                                         in that it generally really
 301                                         just halts the system rather
 302                                         than powering it down.</para>
 303
 304                                         <para>Applications wanting to
 305                                         halt the system should start
 306                                         this unit.</para>
 307                                 </listitem>
 308                         </varlistentry>
 309                         <varlistentry>
 310                                 <term><filename>initrd-fs.target</filename></term>
 311                                 <listitem>
 312                                         <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 313                                         automatically adds
 314                                         dependencies of type
 315                                         <varname>Before=</varname> to
 316                                         <filename>sysroot-usr.mount</filename>
 317                                         and all mount points fround in
 318                                         <filename>/etc/fstab</filename>
 319                                         that have the
 320                                         <option>auto</option> and
 321                                         <option>x-initrd.mount</option>
 322                                         mount options set.
 323                                         </para>
 324                                 </listitem>
 325                         </varlistentry>
 326                         <varlistentry>
 327                                 <term><filename>kbrequest.target</filename></term>
 328                                 <listitem>
 329                                         <para>systemd starts this
 330                                         target whenever Alt+ArrowUp is
 331                                         pressed on the console. This
 332                                         is a good candidate to be
 333                                         aliased (symlinked) to
 334                                         <filename>rescue.target</filename>.</para>
 335                                 </listitem>
 336                         </varlistentry>
 337                         <varlistentry>
 338                                 <term><filename>kexec.target</filename></term>
 339                                 <listitem>
 340                                         <para>A special target unit
 341                                         for shutting down and rebooting the system via kexec.</para>
 342
 343                                         <para>Applications wanting to
 344                                         reboot the system with kexec should start
 345                                         this unit.</para>
 346                                 </listitem>
 347                         </varlistentry>
 348                         <varlistentry>
 349                                 <term><filename>local-fs.target</filename></term>
 350                                 <listitem>
 351                                         <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 352                                         automatically adds
 353                                         dependencies of type
 354                                         <varname>Before=</varname> to
 355                                         all mount units that refer to
 356                                         local mount points for this
 357                                         target unit. In addition, it
 358                                         adds dependencies of type
 359                                         <varname>Wants=</varname> to
 360                                         this target unit for those
 361                                         mounts listed in
 362                                         <filename>/etc/fstab</filename>
 363                                         that have the
 364                                         <option>auto</option> mount
 365                                         option set.</para>
 366                                 </listitem>
 367                         </varlistentry>
 368                         <varlistentry>
 369                                 <term><filename>multi-user.target</filename></term>
 370                                 <listitem>
 371                                         <para>A special target unit
 372                                         for setting up a multi-user
 373                                         system (non-graphical). This
 374                                         is pulled in by
 375                                         <filename>graphical.target</filename>.</para>
 376
 377                                         <para>Units that are needed
 378                                         for a multi-user system shall
 379                                         add <varname>Wants=</varname>
 380                                         dependencies for their unit to
 381                                         this unit during
 382                                         installation. This is best
 383                                         configured via
 384                                         <varname>WantedBy=multi-uer.target</varname>
 385                                         in the unit's
 386                                         <literal>[Install]</literal>
 387                                         section.</para>
 388                                 </listitem>
 389                         </varlistentry>
 390                         <varlistentry>
 391                                 <term><filename>paths.target</filename></term>
 392                                 <listitem>
 393                                         <para>A special target unit
 394                                         that sets up all path units
 395                                         (see
 396                                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 397                                         for details) that shall be
 398                                         active after boot.</para>
 399
 400                                         <para>It is recommended that
 401                                         path units installed by
 402                                         applications get pulled in via
 403                                         <varname>Wants=</varname>
 404                                         dependencies from this
 405                                         unit. This is best configured
 406                                         via a
 407                                         <varname>WantedBy=paths.target</varname>
 408                                         in the path unit's
 409                                         <literal>[Install]</literal>
 410                                         section.</para>
 411                                 </listitem>
 412                         </varlistentry>
 413                         <varlistentry>
 414                                 <term><filename>poweroff.target</filename></term>
 415                                 <listitem>
 416                                         <para>A special target unit
 417                                         for shutting down and powering off the system.</para>
 418
 419                                         <para>Applications wanting to
 420                                         power off the system should start
 421                                         this unit.</para>
 422
 423                                         <para><filename>runlevel0.target</filename>
 424                                         is an alias for this target
 425                                         unit, for compatibility with SysV.</para>
 426                                 </listitem>
 427                         </varlistentry>
 428                         <varlistentry>
 429                                 <term><filename>reboot.target</filename></term>
 430                                 <listitem>
 431                                         <para>A special target unit
 432                                         for shutting down and rebooting the system.</para>
 433
 434                                         <para>Applications wanting to
 435                                         reboot the system should start
 436                                         this unit.</para>
 437
 438                                         <para><filename>runlevel6.target</filename>
 439                                         is an alias for this target
 440                                         unit, for compatibility with SysV.</para>
 441                                 </listitem>
 442                         </varlistentry>
 443                         <varlistentry>
 444                                 <term><filename>remote-fs.target</filename></term>
 445                                 <listitem>
 446                                         <para>Similar to
 447                                         <filename>local-fs.target</filename>,
 448                                         but for remote mount
 449                                         points.</para>
 450
 451                                         <para>systemd automatically
 452                                         adds dependencies of type
 453                                         <varname>After=</varname> for
 454                                         this target unit to all SysV
 455                                         init script service units with
 456                                         an LSB header referring to the
 457                                         <literal>$remote_fs</literal>
 458                                         facility.</para>
 459                                 </listitem>
 460                         </varlistentry>
 461                         <varlistentry>
 462                                 <term><filename>remote-fs-setup.target</filename></term>
 463                                 <listitem>
 464                                         <para>This target unit is
 465                                         automatically pulled in (by a
 466                                         <varname>Wants=</varname> type
 467                                         dependency) by all remote
 468                                         mount points. It can be used
 469                                         to run certain units when at
 470                                         least one remote file system
 471                                         is to be mounted. Note that
 472                                         this target is not ordered
 473                                         against the remote mounts, use
 474                                         <filename>remote-fs-pre.target</filename>
 475                                         for that (see below).</para>
 476
 477                                         <para>Again, this target unit
 478                                         is <emphasis>not</emphasis>
 479                                         suitable for ordering, it is
 480                                         only useful for pulling in
 481                                         other units.</para>
 482                                 </listitem>
 483                         </varlistentry>
 484                         <varlistentry>
 485                                 <term><filename>rescue.target</filename></term>
 486                                 <listitem>
 487                                         <para>A special target unit
 488                                         for setting up the base system
 489                                         and a rescue shell.</para>
 490
 491                                         <para><filename>runlevel1.target</filename>
 492                                         is an alias for this target
 493                                         unit, for compatibility with SysV.</para>
 494                                 </listitem>
 495                         </varlistentry>
 496                         <varlistentry>
 497                                 <term><filename>initrd-root-fs.target</filename></term>
 498                                 <listitem>
 499                                         <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 500                                         automatically adds
 501                                         dependencies of type
 502                                         <varname>Before=</varname> to
 503                                         the
 504                                         <filename>sysroot.mount</filename>
 505                                         unit, which is generated from
 506                                         the kernel command line.
 507                                         </para>
 508                                 </listitem>
 509                         </varlistentry>
 510                         <varlistentry>
 511                                 <term><filename>runlevel2.target</filename></term>
 512                                 <term><filename>runlevel3.target</filename></term>
 513                                 <term><filename>runlevel4.target</filename></term>
 514                                 <term><filename>runlevel5.target</filename></term>
 515                                 <listitem>
 516                                         <para>These are targets that
 517                                         are called whenever the SysV
 518                                         compatibility code asks for
 519                                         runlevel 2, 3, 4, 5,
 520                                         respectively. It is a good
 521                                         idea to make this an alias for
 522                                         (i.e. symlink to)
 523                                         <filename>multi-user.target</filename>
 524                                         (for runlevel 2) or
 525                                         <filename>graphical.target</filename>
 526                                         (the others).</para>
 527                                 </listitem>
 528                         </varlistentry>
 529                         <varlistentry>
 530                                 <term><filename>shutdown.target</filename></term>
 531                                 <listitem>
 532                                         <para>A special target unit
 533                                         that terminates the services
 534                                         on system shutdown.</para>
 535
 536                                         <para>Services that shall be
 537                                         terminated on system shutdown
 538                                         shall add <varname>Conflicts=</varname>
 539                                         dependencies to this unit for
 540                                         their service unit, which is
 541                                         implicitly done when
 542                                         <varname>DefaultDependencies=yes</varname>
 543                                         is set (the default).</para>
 544                                 </listitem>
 545                         </varlistentry>
 546                         <varlistentry>
 547                                 <term><filename>sigpwr.target</filename></term>
 548                                 <listitem>
 549                                         <para>A special target that is
 550                                         started when systemd receives
 551                                         the SIGPWR process signal,
 552                                         which is normally sent by the
 553                                         kernel or UPS daemons when
 554                                         power fails.</para>
 555                                 </listitem>
 556                         </varlistentry>
 557                         <varlistentry>
 558                                 <term><filename>sleep.target</filename></term>
 559                                 <listitem>
 560                                         <para>A special target unit
 561                                         that is pulled in by
 562                                         <filename>suspend.target</filename>,
 563                                         <filename>hibernate.target</filename>
 564                                         and
 565                                         <filename>hybrid-sleep.target</filename>
 566                                         and may be used to hook units
 567                                         into the sleep state
 568                                         logic.</para>
 569                                 </listitem>
 570                         </varlistentry>
 571                         <varlistentry>
 572                                 <term><filename>sockets.target</filename></term>
 573                                 <listitem>
 574                                         <para>A special target unit
 575                                         that sets up all socket
 576                                         units.(see
 577                                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 578                                         for details) that shall be
 579                                         active after boot.</para>
 580
 581                                         <para>Services that can be
 582                                         socket-activated shall add
 583                                         <varname>Wants=</varname>
 584                                         dependencies to this unit for
 585                                         their socket unit during
 586                                         installation. This is best
 587                                         configured via a
 588                                         <varname>WantedBy=sockets.target</varname>
 589                                         in the socket unit's
 590                                         <literal>[Install]</literal>
 591                                         section.</para>
 592                                 </listitem>
 593                         </varlistentry>
 594                         <varlistentry>
 595                                 <term><filename>suspend.target</filename></term>
 596                                 <listitem>
 597                                         <para>A special target unit
 598                                         for suspending the
 599                                         system. This pulls in
 600                                         <filename>sleep.target</filename>.</para>
 601                                 </listitem>
 602                         </varlistentry>
 603                         <varlistentry>
 604                                 <term><filename>swap.target</filename></term>
 605                                 <listitem>
 606                                         <para>Similar to
 607                                         <filename>local-fs.target</filename>, but for swap
 608                                         partitions and swap
 609                                         files.</para>
 610                                 </listitem>
 611                         </varlistentry>
 612                         <varlistentry>
 613                                 <term><filename>sysinit.target</filename></term>
 614                                 <listitem>
 615                                         <para>A special target unit
 616                                         covering early boot-up scripts.</para>
 617                                 </listitem>
 618                         </varlistentry>
 619                         <varlistentry>
 620                                 <term><filename>syslog.socket</filename></term>
 621                                 <listitem>
 622                                         <para>The socket unit
 623                                         syslog implementations should
 624                                         listen on. All userspace log
 625                                         messages will be made
 626                                         available on this socket. For
 627                                         more information about syslog
 628                                         integration, please consult
 629                                         the <ulink
 630                                         url="http://www.freedesktop.org/wiki/Software/systemd/syslog">Syslog
 631                                         Interface</ulink>
 632                                         document.</para>
 633                                 </listitem>
 634                         </varlistentry>
 635                         <varlistentry>
 636                                 <term><filename>system-update.target</filename></term>
 637                                 <listitem>
 638                                         <para>A special target unit
 639                                         that is used for off-line
 640                                         system updates.
 641                                         <citerefentry><refentrytitle>systemd-system-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 642                                         will redirect the boot process
 643                                         to this target if
 644                                         <filename>/system-update</filename>
 645                                         exists. For more information
 646                                         see the <ulink
 647                                         url="http://freedesktop.org/wiki/Software/systemd/SystemUpdates">System
 648                                         Updates
 649                                         Specification</ulink>.</para>
 650                                 </listitem>
 651                         </varlistentry>
 652                         <varlistentry>
 653                                 <term><filename>timers.target</filename></term>
 654                                 <listitem>
 655                                         <para>A special target unit
 656                                         that sets up all timer
 657                                         units (see
 658                                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 659                                         for details) that shall be
 660                                         active after boot.</para>
 661
 662                                         <para>It is recommended that
 663                                         timer units installed by
 664                                         applications get pulled in via
 665                                         <varname>Wants=</varname>
 666                                         dependencies from this
 667                                         unit. This is best configured
 668                                         via
 669                                         <varname>WantedBy=timers.target</varname>
 670                                         in the timer unit's
 671                                         <literal>[Install]</literal>
 672                                         section.</para>
 673                                 </listitem>
 674                         </varlistentry>
 675                         <varlistentry>
 676                                 <term><filename>umount.target</filename></term>
 677                                 <listitem>
 678                                         <para>A special target unit
 679                                         that umounts all mount and
 680                                         automount points on system
 681                                         shutdown.</para>
 682
 683                                         <para>Mounts that shall be
 684                                         unmounted on system shutdown
 685                                         shall add Conflicts
 686                                         dependencies to this unit for
 687                                         their mount unit, which is
 688                                         implicitly done when
 689                                         <varname>DefaultDependencies=yes</varname>
 690                                         is set (the default).</para>
 691                                 </listitem>
 692                         </varlistentry>
 693
 694                 </variablelist>
 695         </refsect1>
 696
 697         <refsect1>
 698                 <title>Special System Units for Devices</title>
 699
 700                 <para>Some target units are automatically pulled in as
 701                 devices of certain kinds show up in the system. These
 702                 may be used to automatically activate various services
 703                 based on the specific type of the available
 704                 hardware.</para>
 705
 706                 <variablelist>
 707                         <varlistentry>
 708                                 <term><filename>bluetooth.target</filename></term>
 709                                 <listitem>
 710                                         <para>This target is started
 711                                         automatically as soon as a
 712                                         Bluetooth controller is
 713                                         plugged in or becomes
 714                                         available at boot.</para>
 715
 716                                         <para>This may be used to pull
 717                                         in Bluetooth management
 718                                         daemons dynamically when
 719                                         Bluetooth hardware is
 720                                         found.</para>
 721                                 </listitem>
 722                         </varlistentry>
 723                         <varlistentry>
 724                                 <term><filename>printer.target</filename></term>
 725                                 <listitem>
 726                                         <para>This target is started
 727                                         automatically as soon as a
 728                                         printer is plugged in or
 729                                         becomes available at
 730                                         boot.</para>
 731
 732                                         <para>This may be used to pull
 733                                         in printer management
 734                                         daemons dynamically when
 735                                         printer hardware is
 736                                         found.</para>
 737                                 </listitem>
 738                         </varlistentry>
 739                         <varlistentry>
 740                                 <term><filename>smartcard.target</filename></term>
 741                                 <listitem>
 742                                         <para>This target is started
 743                                         automatically as soon as a
 744                                         smartcard controller is
 745                                         plugged in or becomes
 746                                         available at boot.</para>
 747
 748                                         <para>This may be used to pull
 749                                         in printer management
 750                                         daemons dynamically when
 751                                         smartcard hardware is
 752                                         found.</para>
 753                                 </listitem>
 754                         </varlistentry>
 755                         <varlistentry>
 756                                 <term><filename>sound.target</filename></term>
 757                                 <listitem>
 758                                         <para>This target is started
 759                                         automatically as soon as a
 760                                         sound card is plugged in or
 761                                         becomes available at
 762                                         boot.</para>
 763
 764                                         <para>This may be used to pull
 765                                         in audio management daemons
 766                                         dynamically when printer
 767                                         hardware is found.</para>
 768                                 </listitem>
 769                         </varlistentry>
 770                 </variablelist>
 771         </refsect1>
 772
 773         <refsect1>
 774                 <title>Special Passive System Units </title>
 775
 776                 <para>A number of special system targets are defined
 777                 that can be used to properly order boot-up of optional
 778                 services. These targets are generally not part of the
 779                 initial boot transaction, unless they are explicitly
 780                 pulled in by one of the implementing services. Note
 781                 specifically, that these <emphasis>passive</emphasis>
 782                 target units are generally not pulled in by the
 783                 consumer of a service, but by the provider of the
 784                 service. This means: a consuming service should order
 785                 itself after these targets (as appropriate), but not
 786                 pull it in. A providing service should order itself
 787                 before these targets (as appropriate) and pull it in
 788                 (via a <varname>Wants=</varname> type
 789                 dependency).</para>
 790
 791                 <para>Note that these passive units cannot be started
 792                 manually, i.e. <literal>systemctl start
 793                 time-sync.target</literal> will fail with an
 794                 error. They can only be pulled in by dependency. This
 795                 is enforced since they exist for ordering purposes
 796                 only and thus are not useful as only unit within a
 797                 transaction.</para>
 798
 799                 <variablelist>
 800                         <varlistentry>
 801                                 <term><filename>local-fs-pre.target</filename></term>
 802                                 <listitem>
 803                                         <para>This target unit is
 804                                         automatically ordered before
 805                                         all local mount points marked
 806                                         with <option>auto</option>
 807                                         (see above). It can be used to
 808                                         execute certain units before
 809                                         all local mounts.</para>
 810                                 </listitem>
 811                         </varlistentry>
 812                         <varlistentry>
 813                                 <term><filename>network.target</filename></term>
 814                                 <listitem>
 815                                         <para>systemd automatically
 816                                         adds dependencies of type
 817                                         <varname>After=</varname> for
 818                                         this target unit to all SysV
 819                                         init script service units with
 820                                         an LSB header referring to the
 821                                         <literal>$network</literal>
 822                                         facility.</para>
 823
 824                                         <para>This unit is supposed to
 825                                         indicate when the network is
 826                                         "up", but it is only very
 827                                         loosely defined what that is
 828                                         supposed to mean. Also see <ulink
 829                                         url="http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running
 830                                         Services After the Network is
 831                                         up</ulink> for more
 832                                         information.</para>
 833                                 </listitem>
 834                         </varlistentry>
 835                         <varlistentry>
 836                                 <term><filename>nss-lookup.target</filename></term>
 837                                 <listitem>
 838                                         <para>A target that should be
 839                                         used as synchronization point
 840                                         for all host/network name
 841                                         service lookups. Note that
 842                                         this is independent of
 843                                         user/group name lookups for
 844                                         which
 845                                         <filename>nss-user-lookup.target</filename>
 846                                         should be used. systemd
 847                                         automatically adds
 848                                         dependencies of type
 849                                         <varname>After=</varname> for
 850                                         this target unit to all SysV
 851                                         init script service units with
 852                                         an LSB header referring to the
 853                                         <literal>$named</literal>
 854                                         facility.</para>
 855                                 </listitem>
 856                         </varlistentry>
 857                         <varlistentry>
 858                                 <term><filename>nss-user-lookup.target</filename></term>
 859                                 <listitem>
 860                                         <para>A target that should be
 861                                         used as synchronization point
 862                                         for all user/group name
 863                                         service lookups. Note that
 864                                         this is independent of
 865                                         host/network name lookups for
 866                                         which
 867                                         <filename>nss-lookup.target</filename>
 868                                         should be used. </para>
 869                                 </listitem>
 870                         </varlistentry>
 871                         <varlistentry>
 872                                 <term><filename>remote-fs-pre.target</filename></term>
 873                                 <listitem>
 874                                         <para>This target unit is
 875                                         automatically ordered before
 876                                         all remote mount point units
 877                                         (see above). It can be used to
 878                                         run certain units before the
 879                                         remote mounts are
 880                                         established. Note that this
 881                                         unit is generally not part of
 882                                         the initial transaction,
 883                                         unless the unit that wants to
 884                                         be ordered before all remote
 885                                         mounts pulls it in via a
 886                                         <varname>Wants=</varname> type
 887                                         dependency. If the unit wants
 888                                         to be pulled in by the first
 889                                         remote mount showing up it
 890                                         should use
 891                                         <filename>remote-fs-setup.target</filename>
 892                                         (see above).</para>
 893
 894                                         <para>Again, this target unit
 895                                         is <emphasis>not</emphasis>
 896                                         suitable for pulling in other
 897                                         units, it is only useful for
 898                                         ordering.</para>
 899                                 </listitem>
 900                         </varlistentry>
 901                         <varlistentry>
 902                                 <term><filename>rpcbind.target</filename></term>
 903                                 <listitem>
 904                                         <para>systemd automatically
 905                                         adds dependencies of type
 906                                         <varname>After=</varname> for
 907                                         this target unit to all SysV
 908                                         init script service units with
 909                                         an LSB header referring to the
 910                                         <literal>$portmap</literal>
 911                                         facility.</para>
 912                                 </listitem>
 913                         </varlistentry>
 914                         <varlistentry>
 915                                 <term><filename>time-sync.target</filename></term>
 916                                 <listitem>
 917                                         <para>systemd automatically
 918                                         adds dependencies of type
 919                                         <varname>After=</varname> for
 920                                         this target unit to all SysV
 921                                         init script service units with
 922                                         an LSB header referring to the
 923                                         <literal>$time</literal>
 924                                         facility.</para>
 925                                 </listitem>
 926                         </varlistentry>
 927                 </variablelist>
 928         </refsect1>
 929
 930         <refsect1>
 931                 <title>Special User Units</title>
 932
 933                 <para>When systemd runs as a user instance, the
 934                 following special units are available, which have
 935                 similar definitions as their system counterparts:
 936                 <filename>default.target</filename>,
 937                 <filename>shutdown.target</filename>,
 938                 <filename>sockets.target</filename>,
 939                 <filename>timers.target</filename>,
 940                 <filename>paths.target</filename>,
 941                 <filename>bluetooth.target</filename>,
 942                 <filename>printer.target</filename>,
 943                 <filename>smartcard.target</filename>,
 944                 <filename>sound.target</filename>.</para>
 945
 946                 <para>In addition the following special unit is
 947                 understood only when systemd runs as service instance:</para>
 948
 949                 <variablelist>
 950                         <varlistentry>
 951                                 <term><filename>exit.target</filename></term>
 952                                 <listitem>
 953                                         <para>A special service unit
 954                                         for shutting down the
 955                                         user service manager.</para>
 956
 957                                         <para>Applications wanting to
 958                                         terminate the user service
 959                                         manager should start this
 960                                         unit. If systemd receives
 961                                         SIGTERM or SIGINT when running
 962                                         as user service daemon it will
 963                                         start this unit.</para>
 964
 965                                         <para>Normally, this pulls in
 966                                         <filename>shutdown.target</filename>
 967                                         which in turn should be
 968                                         conflicted by all units that
 969                                         want to be shut down on
 970                                         user service manager exit.</para>
 971                                 </listitem>
 972                         </varlistentry>
 973                 </variablelist>
 974         </refsect1>
 975
 976         <refsect1>
 977                   <title>See Also</title>
 978                   <para>
 979                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 980                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 981                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 982                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 983                           <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 984                           <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 985                           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 986                   </para>
 987         </refsect1>
 988
 989 </refentry>