man/systemd.special.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
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  18   Lesser General Public License for more details.
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  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
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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>network.target</filename></term>
 392                                 <listitem>
 393                                         <para>systemd automatically
 394                                         adds dependencies of type
 395                                         <varname>After=</varname> for
 396                                         this target unit to all SysV
 397                                         init script service units with
 398                                         an LSB header referring to the
 399                                         <literal>$network</literal>
 400                                         facility.</para>
 401
 402                                         <para>This unit is supposed to
 403                                         indicate when the network is
 404                                         "up", but it is only very
 405                                         loosely defined what that is
 406                                         supposed to mean. Also see <ulink
 407                                         url="http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running
 408                                         Services After the Network is
 409                                         up</ulink> for more
 410                                         information.</para>
 411                                 </listitem>
 412                         </varlistentry>
 413                         <varlistentry>
 414                                 <term><filename>paths.target</filename></term>
 415                                 <listitem>
 416                                         <para>A special target unit
 417                                         that sets up all path units
 418                                         (see
 419                                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 420                                         for details) that shall be
 421                                         active after boot.</para>
 422
 423                                         <para>It is recommended that
 424                                         path units installed by
 425                                         applications get pulled in via
 426                                         <varname>Wants=</varname>
 427                                         dependencies from this
 428                                         unit. This is best configured
 429                                         via a
 430                                         <varname>WantedBy=paths.target</varname>
 431                                         in the path unit's
 432                                         <literal>[Install]</literal>
 433                                         section.</para>
 434                                 </listitem>
 435                         </varlistentry>
 436                         <varlistentry>
 437                                 <term><filename>poweroff.target</filename></term>
 438                                 <listitem>
 439                                         <para>A special target unit
 440                                         for shutting down and powering off the system.</para>
 441
 442                                         <para>Applications wanting to
 443                                         power off the system should start
 444                                         this unit.</para>
 445
 446                                         <para><filename>runlevel0.target</filename>
 447                                         is an alias for this target
 448                                         unit, for compatibility with SysV.</para>
 449                                 </listitem>
 450                         </varlistentry>
 451                         <varlistentry>
 452                                 <term><filename>reboot.target</filename></term>
 453                                 <listitem>
 454                                         <para>A special target unit
 455                                         for shutting down and rebooting the system.</para>
 456
 457                                         <para>Applications wanting to
 458                                         reboot the system should start
 459                                         this unit.</para>
 460
 461                                         <para><filename>runlevel6.target</filename>
 462                                         is an alias for this target
 463                                         unit, for compatibility with SysV.</para>
 464                                 </listitem>
 465                         </varlistentry>
 466                         <varlistentry>
 467                                 <term><filename>remote-fs.target</filename></term>
 468                                 <listitem>
 469                                         <para>Similar to
 470                                         <filename>local-fs.target</filename>,
 471                                         but for remote mount
 472                                         points.</para>
 473
 474                                         <para>systemd automatically
 475                                         adds dependencies of type
 476                                         <varname>After=</varname> for
 477                                         this target unit to all SysV
 478                                         init script service units with
 479                                         an LSB header referring to the
 480                                         <literal>$remote_fs</literal>
 481                                         facility.</para>
 482                                 </listitem>
 483                         </varlistentry>
 484                         <varlistentry>
 485                                 <term><filename>remote-fs-setup.target</filename></term>
 486                                 <listitem>
 487                                         <para>This target unit is
 488                                         automatically pulled in (by a
 489                                         <varname>Wants=</varname> type
 490                                         dependency) by all remote
 491                                         mount points. It can be used
 492                                         to run certain units when at
 493                                         least one remote file system
 494                                         is to be mounted. Note that
 495                                         this target is not ordered
 496                                         against the remote mounts, use
 497                                         <filename>remote-fs-pre.target</filename>
 498                                         for that (see below).</para>
 499
 500                                         <para>Again, this target unit
 501                                         is <emphasis>not</emphasis>
 502                                         suitable for ordering, it is
 503                                         only useful for pulling in
 504                                         other units.</para>
 505                                 </listitem>
 506                         </varlistentry>
 507                         <varlistentry>
 508                                 <term><filename>rescue.target</filename></term>
 509                                 <listitem>
 510                                         <para>A special target unit
 511                                         for setting up the base system
 512                                         and a rescue shell.</para>
 513
 514                                         <para><filename>runlevel1.target</filename>
 515                                         is an alias for this target
 516                                         unit, for compatibility with SysV.</para>
 517                                 </listitem>
 518                         </varlistentry>
 519                         <varlistentry>
 520                                 <term><filename>initrd-root-fs.target</filename></term>
 521                                 <listitem>
 522                                         <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 523                                         automatically adds
 524                                         dependencies of type
 525                                         <varname>Before=</varname> to
 526                                         the
 527                                         <filename>sysroot.mount</filename>
 528                                         unit, which is generated from
 529                                         the kernel command line.
 530                                         </para>
 531                                 </listitem>
 532                         </varlistentry>
 533                         <varlistentry>
 534                                 <term><filename>runlevel2.target</filename></term>
 535                                 <term><filename>runlevel3.target</filename></term>
 536                                 <term><filename>runlevel4.target</filename></term>
 537                                 <term><filename>runlevel5.target</filename></term>
 538                                 <listitem>
 539                                         <para>These are targets that
 540                                         are called whenever the SysV
 541                                         compatibility code asks for
 542                                         runlevel 2, 3, 4, 5,
 543                                         respectively. It is a good
 544                                         idea to make this an alias for
 545                                         (i.e. symlink to)
 546                                         <filename>multi-user.target</filename>
 547                                         (for runlevel 2) or
 548                                         <filename>graphical.target</filename>
 549                                         (the others).</para>
 550                                 </listitem>
 551                         </varlistentry>
 552                         <varlistentry>
 553                                 <term><filename>shutdown.target</filename></term>
 554                                 <listitem>
 555                                         <para>A special target unit
 556                                         that terminates the services
 557                                         on system shutdown.</para>
 558
 559                                         <para>Services that shall be
 560                                         terminated on system shutdown
 561                                         shall add <varname>Conflicts=</varname>
 562                                         dependencies to this unit for
 563                                         their service unit, which is
 564                                         implicitly done when
 565                                         <varname>DefaultDependencies=yes</varname>
 566                                         is set (the default).</para>
 567                                 </listitem>
 568                         </varlistentry>
 569                         <varlistentry>
 570                                 <term><filename>sigpwr.target</filename></term>
 571                                 <listitem>
 572                                         <para>A special target that is
 573                                         started when systemd receives
 574                                         the SIGPWR process signal,
 575                                         which is normally sent by the
 576                                         kernel or UPS daemons when
 577                                         power fails.</para>
 578                                 </listitem>
 579                         </varlistentry>
 580                         <varlistentry>
 581                                 <term><filename>sleep.target</filename></term>
 582                                 <listitem>
 583                                         <para>A special target unit
 584                                         that is pulled in by
 585                                         <filename>suspend.target</filename>,
 586                                         <filename>hibernate.target</filename>
 587                                         and
 588                                         <filename>hybrid-sleep.target</filename>
 589                                         and may be used to hook units
 590                                         into the sleep state
 591                                         logic.</para>
 592                                 </listitem>
 593                         </varlistentry>
 594                         <varlistentry>
 595                                 <term><filename>sockets.target</filename></term>
 596                                 <listitem>
 597                                         <para>A special target unit
 598                                         that sets up all socket
 599                                         units.(see
 600                                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 601                                         for details) that shall be
 602                                         active after boot.</para>
 603
 604                                         <para>Services that can be
 605                                         socket-activated shall add
 606                                         <varname>Wants=</varname>
 607                                         dependencies to this unit for
 608                                         their socket unit during
 609                                         installation. This is best
 610                                         configured via a
 611                                         <varname>WantedBy=sockets.target</varname>
 612                                         in the socket unit's
 613                                         <literal>[Install]</literal>
 614                                         section.</para>
 615                                 </listitem>
 616                         </varlistentry>
 617                         <varlistentry>
 618                                 <term><filename>suspend.target</filename></term>
 619                                 <listitem>
 620                                         <para>A special target unit
 621                                         for suspending the
 622                                         system. This pulls in
 623                                         <filename>sleep.target</filename>.</para>
 624                                 </listitem>
 625                         </varlistentry>
 626                         <varlistentry>
 627                                 <term><filename>swap.target</filename></term>
 628                                 <listitem>
 629                                         <para>Similar to
 630                                         <filename>local-fs.target</filename>, but for swap
 631                                         partitions and swap
 632                                         files.</para>
 633                                 </listitem>
 634                         </varlistentry>
 635                         <varlistentry>
 636                                 <term><filename>sysinit.target</filename></term>
 637                                 <listitem>
 638                                         <para>A special target unit
 639                                         covering early boot-up scripts.</para>
 640                                 </listitem>
 641                         </varlistentry>
 642                         <varlistentry>
 643                                 <term><filename>syslog.socket</filename></term>
 644                                 <listitem>
 645                                         <para>The socket unit
 646                                         syslog implementations should
 647                                         listen on. All userspace log
 648                                         messages will be made
 649                                         available on this socket. For
 650                                         more information about syslog
 651                                         integration, please consult
 652                                         the <ulink
 653                                         url="http://www.freedesktop.org/wiki/Software/systemd/syslog">Syslog
 654                                         Interface</ulink>
 655                                         document.</para>
 656                                 </listitem>
 657                         </varlistentry>
 658                         <varlistentry>
 659                                 <term><filename>system-update.target</filename></term>
 660                                 <listitem>
 661                                         <para>A special target unit
 662                                         that is used for off-line
 663                                         system updates.
 664                                         <citerefentry><refentrytitle>systemd-system-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 665                                         will redirect the boot process
 666                                         to this target if
 667                                         <filename>/system-update</filename>
 668                                         exists. For more information
 669                                         see the <ulink
 670                                         url="http://freedesktop.org/wiki/Software/systemd/SystemUpdates">System
 671                                         Updates
 672                                         Specification</ulink>.</para>
 673                                 </listitem>
 674                         </varlistentry>
 675                         <varlistentry>
 676                                 <term><filename>timers.target</filename></term>
 677                                 <listitem>
 678                                         <para>A special target unit
 679                                         that sets up all timer
 680                                         units (see
 681                                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 682                                         for details) that shall be
 683                                         active after boot.</para>
 684
 685                                         <para>It is recommended that
 686                                         timer units installed by
 687                                         applications get pulled in via
 688                                         <varname>Wants=</varname>
 689                                         dependencies from this
 690                                         unit. This is best configured
 691                                         via
 692                                         <varname>WantedBy=timers.target</varname>
 693                                         in the timer unit's
 694                                         <literal>[Install]</literal>
 695                                         section.</para>
 696                                 </listitem>
 697                         </varlistentry>
 698                         <varlistentry>
 699                                 <term><filename>umount.target</filename></term>
 700                                 <listitem>
 701                                         <para>A special target unit
 702                                         that umounts all mount and
 703                                         automount points on system
 704                                         shutdown.</para>
 705
 706                                         <para>Mounts that shall be
 707                                         unmounted on system shutdown
 708                                         shall add Conflicts
 709                                         dependencies to this unit for
 710                                         their mount unit, which is
 711                                         implicitly done when
 712                                         <varname>DefaultDependencies=yes</varname>
 713                                         is set (the default).</para>
 714                                 </listitem>
 715                         </varlistentry>
 716
 717                 </variablelist>
 718         </refsect1>
 719
 720         <refsect1>
 721                 <title>Special System Units for Devices</title>
 722
 723                 <para>Some target units are automatically pulled in as
 724                 devices of certain kinds show up in the system. These
 725                 may be used to automatically activate various services
 726                 based on the specific type of the available
 727                 hardware.</para>
 728
 729                 <variablelist>
 730                         <varlistentry>
 731                                 <term><filename>bluetooth.target</filename></term>
 732                                 <listitem>
 733                                         <para>This target is started
 734                                         automatically as soon as a
 735                                         Bluetooth controller is
 736                                         plugged in or becomes
 737                                         available at boot.</para>
 738
 739                                         <para>This may be used to pull
 740                                         in Bluetooth management
 741                                         daemons dynamically when
 742                                         Bluetooth hardware is
 743                                         found.</para>
 744                                 </listitem>
 745                         </varlistentry>
 746                         <varlistentry>
 747                                 <term><filename>printer.target</filename></term>
 748                                 <listitem>
 749                                         <para>This target is started
 750                                         automatically as soon as a
 751                                         printer is plugged in or
 752                                         becomes available at
 753                                         boot.</para>
 754
 755                                         <para>This may be used to pull
 756                                         in printer management
 757                                         daemons dynamically when
 758                                         printer hardware is
 759                                         found.</para>
 760                                 </listitem>
 761                         </varlistentry>
 762                         <varlistentry>
 763                                 <term><filename>smartcard.target</filename></term>
 764                                 <listitem>
 765                                         <para>This target is started
 766                                         automatically as soon as a
 767                                         smartcard controller is
 768                                         plugged in or becomes
 769                                         available at boot.</para>
 770
 771                                         <para>This may be used to pull
 772                                         in printer management
 773                                         daemons dynamically when
 774                                         smartcard hardware is
 775                                         found.</para>
 776                                 </listitem>
 777                         </varlistentry>
 778                         <varlistentry>
 779                                 <term><filename>sound.target</filename></term>
 780                                 <listitem>
 781                                         <para>This target is started
 782                                         automatically as soon as a
 783                                         sound card is plugged in or
 784                                         becomes available at
 785                                         boot.</para>
 786
 787                                         <para>This may be used to pull
 788                                         in audio management daemons
 789                                         dynamically when printer
 790                                         hardware is found.</para>
 791                                 </listitem>
 792                         </varlistentry>
 793                 </variablelist>
 794         </refsect1>
 795
 796         <refsect1>
 797                 <title>Special Passive System Units </title>
 798
 799                 <para>A number of special system targets are defined
 800                 that can be used to properly order boot-up of optional
 801                 services. These targets are generally not part of the
 802                 initial boot transaction, unless they are explicitly
 803                 pulled in by one of the implementing services. Note
 804                 specifically, that these <emphasis>passive</emphasis>
 805                 target units are generally not pulled in by the
 806                 consumer of a service, but by the provider of the
 807                 service. This means: a consuming service should order
 808                 itself after these targets (as appropriate), but not
 809                 pull it in. A providing service should order itself
 810                 before these targets (as appropriate) and pull it in
 811                 (via a <varname>Wants=</varname> type
 812                 dependency).</para>
 813
 814                 <para>Note that these passive units cannot be started
 815                 manually, i.e. <literal>systemctl start
 816                 time-sync.target</literal> will fail with an
 817                 error. They can only be pulled in by dependency. This
 818                 is enforced since they exist for ordering purposes
 819                 only and thus are not useful as only unit within a
 820                 transaction.</para>
 821
 822                 <variablelist>
 823                         <varlistentry>
 824                                 <term><filename>local-fs-pre.target</filename></term>
 825                                 <listitem>
 826                                         <para>This target unit is
 827                                         automatically ordered before
 828                                         all local mount points marked
 829                                         with <option>auto</option>
 830                                         (see above). It can be used to
 831                                         execute certain units before
 832                                         all local mounts.</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>