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