man/systemd.special.xml

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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>network-online.target</filename>,
  75                 <filename>nss-lookup.target</filename>,
  76                 <filename>nss-user-lookup.target</filename>,
  77                 <filename>paths.target</filename>,
  78                 <filename>poweroff.target</filename>,
  79                 <filename>printer.target</filename>,
  80                 <filename>reboot.target</filename>,
  81                 <filename>remote-fs.target</filename>,
  82                 <filename>remote-fs-pre.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>network-online.target</filename></term>
 392                                 <listitem>
 393                                         <para>Units that strictly
 394                                         require a configured network
 395                                         connection should pull in
 396                                         <filename>network-online.target</filename>
 397                                         (via a
 398                                         <varname>Wants=</varname> type
 399                                         dependency) and order
 400                                         themselves after it. This
 401                                         target unit is intended to
 402                                         pull in a service that delays
 403                                         further execution until the
 404                                         network is sufficiently set
 405                                         up. What precisely this
 406                                         requires is left to the
 407                                         implementation of the network
 408                                         managing service.</para>
 409
 410                                         <para>Note the distinction
 411                                         between this unit and
 412                                         <filename>network.target</filename>. This
 413                                         unit is an active unit
 414                                         (i.e. pulled in by the
 415                                         consumer rather than the
 416                                         provider of this
 417                                         functionality) and pulls in a
 418                                         service which possibly adds
 419                                         substantial delays to further
 420                                         execution. In contrast,
 421                                         <filename>network.target</filename>
 422                                         is a passive unit (i.e. pulled
 423                                         in by the provider of the
 424                                         functionality, rather than the
 425                                         consumer) that usually does
 426                                         not delay execution
 427                                         much. Usually,
 428                                         <filename>network.target</filename>
 429                                         is part of the boot of most
 430                                         systems, while
 431                                         <filename>network-online.target</filename>
 432                                         is not, except when at least
 433                                         one unit requires it. Also see
 434                                         <ulink
 435                                         url="http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running
 436                                         Services After the Network is
 437                                         up</ulink> for more
 438                                         information.</para>
 439
 440                                         <para>All mount units for
 441                                         remote network file systems
 442                                         automatically pull in this
 443                                         unit, and order themselves
 444                                         after it. Note that networking
 445                                         daemons that simply provide
 446                                         functionality to other hosts
 447                                         generally don't need to pull
 448                                         this in.</para>
 449                                         </listitem>
 450                         </varlistentry>
 451                         <varlistentry>
 452                                 <term><filename>paths.target</filename></term>
 453                                 <listitem>
 454                                         <para>A special target unit
 455                                         that sets up all path units
 456                                         (see
 457                                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 458                                         for details) that shall be
 459                                         active after boot.</para>
 460
 461                                         <para>It is recommended that
 462                                         path units installed by
 463                                         applications get pulled in via
 464                                         <varname>Wants=</varname>
 465                                         dependencies from this
 466                                         unit. This is best configured
 467                                         via a
 468                                         <varname>WantedBy=paths.target</varname>
 469                                         in the path unit's
 470                                         <literal>[Install]</literal>
 471                                         section.</para>
 472                                 </listitem>
 473                         </varlistentry>
 474                         <varlistentry>
 475                                 <term><filename>poweroff.target</filename></term>
 476                                 <listitem>
 477                                         <para>A special target unit
 478                                         for shutting down and powering off the system.</para>
 479
 480                                         <para>Applications wanting to
 481                                         power off the system should start
 482                                         this unit.</para>
 483
 484                                         <para><filename>runlevel0.target</filename>
 485                                         is an alias for this target
 486                                         unit, for compatibility with SysV.</para>
 487                                 </listitem>
 488                         </varlistentry>
 489                         <varlistentry>
 490                                 <term><filename>reboot.target</filename></term>
 491                                 <listitem>
 492                                         <para>A special target unit
 493                                         for shutting down and rebooting the system.</para>
 494
 495                                         <para>Applications wanting to
 496                                         reboot the system should start
 497                                         this unit.</para>
 498
 499                                         <para><filename>runlevel6.target</filename>
 500                                         is an alias for this target
 501                                         unit, for compatibility with SysV.</para>
 502                                 </listitem>
 503                         </varlistentry>
 504                         <varlistentry>
 505                                 <term><filename>remote-fs.target</filename></term>
 506                                 <listitem>
 507                                         <para>Similar to
 508                                         <filename>local-fs.target</filename>,
 509                                         but for remote mount
 510                                         points.</para>
 511
 512                                         <para>systemd automatically
 513                                         adds dependencies of type
 514                                         <varname>After=</varname> for
 515                                         this target unit to all SysV
 516                                         init script service units with
 517                                         an LSB header referring to the
 518                                         <literal>$remote_fs</literal>
 519                                         facility.</para>
 520                                 </listitem>
 521                         </varlistentry>
 522                         <varlistentry>
 523                                 <term><filename>rescue.target</filename></term>
 524                                 <listitem>
 525                                         <para>A special target unit
 526                                         for setting up the base system
 527                                         and a rescue shell.</para>
 528
 529                                         <para><filename>runlevel1.target</filename>
 530                                         is an alias for this target
 531                                         unit, for compatibility with SysV.</para>
 532                                 </listitem>
 533                         </varlistentry>
 534                         <varlistentry>
 535                                 <term><filename>initrd-root-fs.target</filename></term>
 536                                 <listitem>
 537                                         <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 538                                         automatically adds
 539                                         dependencies of type
 540                                         <varname>Before=</varname> to
 541                                         the
 542                                         <filename>sysroot.mount</filename>
 543                                         unit, which is generated from
 544                                         the kernel command line.
 545                                         </para>
 546                                 </listitem>
 547                         </varlistentry>
 548                         <varlistentry>
 549                                 <term><filename>runlevel2.target</filename></term>
 550                                 <term><filename>runlevel3.target</filename></term>
 551                                 <term><filename>runlevel4.target</filename></term>
 552                                 <term><filename>runlevel5.target</filename></term>
 553                                 <listitem>
 554                                         <para>These are targets that
 555                                         are called whenever the SysV
 556                                         compatibility code asks for
 557                                         runlevel 2, 3, 4, 5,
 558                                         respectively. It is a good
 559                                         idea to make this an alias for
 560                                         (i.e. symlink to)
 561                                         <filename>multi-user.target</filename>
 562                                         (for runlevel 2) or
 563                                         <filename>graphical.target</filename>
 564                                         (the others).</para>
 565                                 </listitem>
 566                         </varlistentry>
 567                         <varlistentry>
 568                                 <term><filename>shutdown.target</filename></term>
 569                                 <listitem>
 570                                         <para>A special target unit
 571                                         that terminates the services
 572                                         on system shutdown.</para>
 573
 574                                         <para>Services that shall be
 575                                         terminated on system shutdown
 576                                         shall add <varname>Conflicts=</varname>
 577                                         dependencies to this unit for
 578                                         their service unit, which is
 579                                         implicitly done when
 580                                         <varname>DefaultDependencies=yes</varname>
 581                                         is set (the default).</para>
 582                                 </listitem>
 583                         </varlistentry>
 584                         <varlistentry>
 585                                 <term><filename>sigpwr.target</filename></term>
 586                                 <listitem>
 587                                         <para>A special target that is
 588                                         started when systemd receives
 589                                         the SIGPWR process signal,
 590                                         which is normally sent by the
 591                                         kernel or UPS daemons when
 592                                         power fails.</para>
 593                                 </listitem>
 594                         </varlistentry>
 595                         <varlistentry>
 596                                 <term><filename>sleep.target</filename></term>
 597                                 <listitem>
 598                                         <para>A special target unit
 599                                         that is pulled in by
 600                                         <filename>suspend.target</filename>,
 601                                         <filename>hibernate.target</filename>
 602                                         and
 603                                         <filename>hybrid-sleep.target</filename>
 604                                         and may be used to hook units
 605                                         into the sleep state
 606                                         logic.</para>
 607                                 </listitem>
 608                         </varlistentry>
 609                         <varlistentry>
 610                                 <term><filename>sockets.target</filename></term>
 611                                 <listitem>
 612                                         <para>A special target unit
 613                                         that sets up all socket
 614                                         units.(see
 615                                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 616                                         for details) that shall be
 617                                         active after boot.</para>
 618
 619                                         <para>Services that can be
 620                                         socket-activated shall add
 621                                         <varname>Wants=</varname>
 622                                         dependencies to this unit for
 623                                         their socket unit during
 624                                         installation. This is best
 625                                         configured via a
 626                                         <varname>WantedBy=sockets.target</varname>
 627                                         in the socket unit's
 628                                         <literal>[Install]</literal>
 629                                         section.</para>
 630                                 </listitem>
 631                         </varlistentry>
 632                         <varlistentry>
 633                                 <term><filename>suspend.target</filename></term>
 634                                 <listitem>
 635                                         <para>A special target unit
 636                                         for suspending the
 637                                         system. This pulls in
 638                                         <filename>sleep.target</filename>.</para>
 639                                 </listitem>
 640                         </varlistentry>
 641                         <varlistentry>
 642                                 <term><filename>swap.target</filename></term>
 643                                 <listitem>
 644                                         <para>Similar to
 645                                         <filename>local-fs.target</filename>, but for swap
 646                                         partitions and swap
 647                                         files.</para>
 648                                 </listitem>
 649                         </varlistentry>
 650                         <varlistentry>
 651                                 <term><filename>sysinit.target</filename></term>
 652                                 <listitem>
 653                                         <para>A special target unit
 654                                         covering early boot-up scripts.</para>
 655                                 </listitem>
 656                         </varlistentry>
 657                         <varlistentry>
 658                                 <term><filename>syslog.socket</filename></term>
 659                                 <listitem>
 660                                         <para>The socket unit
 661                                         syslog implementations should
 662                                         listen on. All userspace log
 663                                         messages will be made
 664                                         available on this socket. For
 665                                         more information about syslog
 666                                         integration, please consult
 667                                         the <ulink
 668                                         url="http://www.freedesktop.org/wiki/Software/systemd/syslog">Syslog
 669                                         Interface</ulink>
 670                                         document.</para>
 671                                 </listitem>
 672                         </varlistentry>
 673                         <varlistentry>
 674                                 <term><filename>system-update.target</filename></term>
 675                                 <listitem>
 676                                         <para>A special target unit
 677                                         that is used for off-line
 678                                         system updates.
 679                                         <citerefentry><refentrytitle>systemd-system-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 680                                         will redirect the boot process
 681                                         to this target if
 682                                         <filename>/system-update</filename>
 683                                         exists. For more information
 684                                         see the <ulink
 685                                         url="http://freedesktop.org/wiki/Software/systemd/SystemUpdates">System
 686                                         Updates
 687                                         Specification</ulink>.</para>
 688                                 </listitem>
 689                         </varlistentry>
 690                         <varlistentry>
 691                                 <term><filename>timers.target</filename></term>
 692                                 <listitem>
 693                                         <para>A special target unit
 694                                         that sets up all timer
 695                                         units (see
 696                                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 697                                         for details) that shall be
 698                                         active after boot.</para>
 699
 700                                         <para>It is recommended that
 701                                         timer units installed by
 702                                         applications get pulled in via
 703                                         <varname>Wants=</varname>
 704                                         dependencies from this
 705                                         unit. This is best configured
 706                                         via
 707                                         <varname>WantedBy=timers.target</varname>
 708                                         in the timer unit's
 709                                         <literal>[Install]</literal>
 710                                         section.</para>
 711                                 </listitem>
 712                         </varlistentry>
 713                         <varlistentry>
 714                                 <term><filename>umount.target</filename></term>
 715                                 <listitem>
 716                                         <para>A special target unit
 717                                         that umounts all mount and
 718                                         automount points on system
 719                                         shutdown.</para>
 720
 721                                         <para>Mounts that shall be
 722                                         unmounted on system shutdown
 723                                         shall add Conflicts
 724                                         dependencies to this unit for
 725                                         their mount unit, which is
 726                                         implicitly done when
 727                                         <varname>DefaultDependencies=yes</varname>
 728                                         is set (the default).</para>
 729                                 </listitem>
 730                         </varlistentry>
 731
 732                 </variablelist>
 733         </refsect1>
 734
 735         <refsect1>
 736                 <title>Special System Units for Devices</title>
 737
 738                 <para>Some target units are automatically pulled in as
 739                 devices of certain kinds show up in the system. These
 740                 may be used to automatically activate various services
 741                 based on the specific type of the available
 742                 hardware.</para>
 743
 744                 <variablelist>
 745                         <varlistentry>
 746                                 <term><filename>bluetooth.target</filename></term>
 747                                 <listitem>
 748                                         <para>This target is started
 749                                         automatically as soon as a
 750                                         Bluetooth controller is
 751                                         plugged in or becomes
 752                                         available at boot.</para>
 753
 754                                         <para>This may be used to pull
 755                                         in Bluetooth management
 756                                         daemons dynamically when
 757                                         Bluetooth hardware is
 758                                         found.</para>
 759                                 </listitem>
 760                         </varlistentry>
 761                         <varlistentry>
 762                                 <term><filename>printer.target</filename></term>
 763                                 <listitem>
 764                                         <para>This target is started
 765                                         automatically as soon as a
 766                                         printer is plugged in or
 767                                         becomes available at
 768                                         boot.</para>
 769
 770                                         <para>This may be used to pull
 771                                         in printer management
 772                                         daemons dynamically when
 773                                         printer hardware is
 774                                         found.</para>
 775                                 </listitem>
 776                         </varlistentry>
 777                         <varlistentry>
 778                                 <term><filename>smartcard.target</filename></term>
 779                                 <listitem>
 780                                         <para>This target is started
 781                                         automatically as soon as a
 782                                         smartcard controller is
 783                                         plugged in or becomes
 784                                         available at boot.</para>
 785
 786                                         <para>This may be used to pull
 787                                         in printer management
 788                                         daemons dynamically when
 789                                         smartcard hardware is
 790                                         found.</para>
 791                                 </listitem>
 792                         </varlistentry>
 793                         <varlistentry>
 794                                 <term><filename>sound.target</filename></term>
 795                                 <listitem>
 796                                         <para>This target is started
 797                                         automatically as soon as a
 798                                         sound card is plugged in or
 799                                         becomes available at
 800                                         boot.</para>
 801
 802                                         <para>This may be used to pull
 803                                         in audio management daemons
 804                                         dynamically when printer
 805                                         hardware is found.</para>
 806                                 </listitem>
 807                         </varlistentry>
 808                 </variablelist>
 809         </refsect1>
 810
 811         <refsect1>
 812                 <title>Special Passive System Units </title>
 813
 814                 <para>A number of special system targets are defined
 815                 that can be used to properly order boot-up of optional
 816                 services. These targets are generally not part of the
 817                 initial boot transaction, unless they are explicitly
 818                 pulled in by one of the implementing services. Note
 819                 specifically, that these <emphasis>passive</emphasis>
 820                 target units are generally not pulled in by the
 821                 consumer of a service, but by the provider of the
 822                 service. This means: a consuming service should order
 823                 itself after these targets (as appropriate), but not
 824                 pull it in. A providing service should order itself
 825                 before these targets (as appropriate) and pull it in
 826                 (via a <varname>Wants=</varname> type
 827                 dependency).</para>
 828
 829                 <para>Note that these passive units cannot be started
 830                 manually, i.e. <literal>systemctl start
 831                 time-sync.target</literal> will fail with an
 832                 error. They can only be pulled in by dependency. This
 833                 is enforced since they exist for ordering purposes
 834                 only and thus are not useful as only unit within a
 835                 transaction.</para>
 836
 837                 <variablelist>
 838                         <varlistentry>
 839                                 <term><filename>local-fs-pre.target</filename></term>
 840                                 <listitem>
 841                                         <para>This target unit is
 842                                         automatically ordered before
 843                                         all local mount points marked
 844                                         with <option>auto</option>
 845                                         (see above). It can be used to
 846                                         execute certain units before
 847                                         all local mounts.</para>
 848                                 </listitem>
 849                         </varlistentry>
 850                         <varlistentry>
 851                                 <term><filename>network.target</filename></term>
 852                                 <listitem>
 853                                         <para>This unit is supposed to
 854                                         indicate when network
 855                                         functionality is available,
 856                                         but it is only very weakly
 857                                         defined what that is supposed
 858                                         to mean, with one exception:
 859                                         at shutdown, a unit that is
 860                                         ordered after
 861                                         <filename>network.target</filename>
 862                                         will be stopped before the
 863                                         network -- to whatever level
 864                                         it might be set up then -- is
 865                                         shut down. Also see <ulink
 866                                         url="http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running
 867                                         Services After the Network is
 868                                         up</ulink> for more
 869                                         information. Also see
 870                                         <filename>network-online.target</filename>
 871                                         described above.</para>
 872
 873                                         <para>systemd automatically
 874                                         adds dependencies of type
 875                                         <varname>After=</varname> for
 876                                         this target unit to all SysV
 877                                         init script service units with
 878                                         an LSB header referring to the
 879                                         <literal>$network</literal>
 880                                         facility.</para>
 881
 882                                 </listitem>
 883                         </varlistentry>
 884                         <varlistentry>
 885                                 <term><filename>nss-lookup.target</filename></term>
 886                                 <listitem>
 887                                         <para>A target that should be
 888                                         used as synchronization point
 889                                         for all host/network name
 890                                         service lookups. Note that
 891                                         this is independent of
 892                                         user/group name lookups for
 893                                         which
 894                                         <filename>nss-user-lookup.target</filename>
 895                                         should be used. systemd
 896                                         automatically adds
 897                                         dependencies of type
 898                                         <varname>After=</varname> for
 899                                         this target unit to all SysV
 900                                         init script service units with
 901                                         an LSB header referring to the
 902                                         <literal>$named</literal>
 903                                         facility.</para>
 904                                 </listitem>
 905                         </varlistentry>
 906                         <varlistentry>
 907                                 <term><filename>nss-user-lookup.target</filename></term>
 908                                 <listitem>
 909                                         <para>A target that should be
 910                                         used as synchronization point
 911                                         for all user/group name
 912                                         service lookups. Note that
 913                                         this is independent of
 914                                         host/network name lookups for
 915                                         which
 916                                         <filename>nss-lookup.target</filename>
 917                                         should be used. </para>
 918                                 </listitem>
 919                         </varlistentry>
 920                         <varlistentry>
 921                                 <term><filename>remote-fs-pre.target</filename></term>
 922                                 <listitem>
 923                                         <para>This target unit is
 924                                         automatically ordered before
 925                                         all remote mount point units
 926                                         (see above). It can be used to
 927                                         run certain units before the
 928                                         remote mounts are
 929                                         established. Note that this
 930                                         unit is generally not part of
 931                                         the initial transaction,
 932                                         unless the unit that wants to
 933                                         be ordered before all remote
 934                                         mounts pulls it in via a
 935                                         <varname>Wants=</varname> type
 936                                         dependency. If the unit wants
 937                                         to be pulled in by the first
 938                                         remote mount showing up it
 939                                         should use
 940                                         <filename>remote-fs-setup.target</filename>
 941                                         (see above).</para>
 942
 943                                         <para>Again, this target unit
 944                                         is <emphasis>not</emphasis>
 945                                         suitable for pulling in other
 946                                         units, it is only useful for
 947                                         ordering.</para>
 948                                 </listitem>
 949                         </varlistentry>
 950                         <varlistentry>
 951                                 <term><filename>rpcbind.target</filename></term>
 952                                 <listitem>
 953                                         <para>systemd automatically
 954                                         adds dependencies of type
 955                                         <varname>After=</varname> for
 956                                         this target unit to all SysV
 957                                         init script service units with
 958                                         an LSB header referring to the
 959                                         <literal>$portmap</literal>
 960                                         facility.</para>
 961                                 </listitem>
 962                         </varlistentry>
 963                         <varlistentry>
 964                                 <term><filename>time-sync.target</filename></term>
 965                                 <listitem>
 966                                         <para>systemd automatically
 967                                         adds dependencies of type
 968                                         <varname>After=</varname> for
 969                                         this target unit to all SysV
 970                                         init script service units with
 971                                         an LSB header referring to the
 972                                         <literal>$time</literal>
 973                                         facility.</para>
 974                                 </listitem>
 975                         </varlistentry>
 976                 </variablelist>
 977         </refsect1>
 978
 979         <refsect1>
 980                 <title>Special User Units</title>
 981
 982                 <para>When systemd runs as a user instance, the
 983                 following special units are available, which have
 984                 similar definitions as their system counterparts:
 985                 <filename>default.target</filename>,
 986                 <filename>shutdown.target</filename>,
 987                 <filename>sockets.target</filename>,
 988                 <filename>timers.target</filename>,
 989                 <filename>paths.target</filename>,
 990                 <filename>bluetooth.target</filename>,
 991                 <filename>printer.target</filename>,
 992                 <filename>smartcard.target</filename>,
 993                 <filename>sound.target</filename>.</para>
 994
 995                 <para>In addition the following special unit is
 996                 understood only when systemd runs as service instance:</para>
 997
 998                 <variablelist>
 999                         <varlistentry>
1000                                 <term><filename>exit.target</filename></term>
1001                                 <listitem>
1002                                         <para>A special service unit
1003                                         for shutting down the
1004                                         user service manager.</para>
1005
1006                                         <para>Applications wanting to
1007                                         terminate the user service
1008                                         manager should start this
1009                                         unit. If systemd receives
1010                                         SIGTERM or SIGINT when running
1011                                         as user service daemon it will
1012                                         start this unit.</para>
1013
1014                                         <para>Normally, this pulls in
1015                                         <filename>shutdown.target</filename>
1016                                         which in turn should be
1017                                         conflicted by all units that
1018                                         want to be shut down on
1019                                         user service manager exit.</para>
1020                                 </listitem>
1021                         </varlistentry>
1022                 </variablelist>
1023         </refsect1>
1024
1025         <refsect1>
1026                   <title>See Also</title>
1027                   <para>
1028                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1029                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1030                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1031                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1032                           <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1033                           <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1034                           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1035                   </para>
1036         </refsect1>
1037
1038 </refentry>