man/systemd.special.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="systemd.special">
  25
  26         <refentryinfo>
  27                 <title>systemd.special</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.special</refentrytitle>
  42                 <manvolnum>7</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.special</refname>
  47                 <refpurpose>Special systemd units</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename>basic.target</filename>,
  52                 <filename>bluetooth.target</filename>,
  53                 <filename>ctrl-alt-del.target</filename>,
  54                 <filename>cryptsetup.target</filename>,
  55                 <filename>dbus.service</filename>,
  56                 <filename>dbus.socket</filename>,
  57                 <filename>default.target</filename>,
  58                 <filename>display-manager.service</filename>,
  59                 <filename>emergency.target</filename>,
  60                 <filename>exit.target</filename>,
  61                 <filename>final.target</filename>,
  62                 <filename>getty.target</filename>,
  63                 <filename>graphical.target</filename>,
  64                 <filename>halt.target</filename>,
  65                 <filename>hibernate.target</filename>,
  66                 <filename>hybrid-sleep.target</filename>,
  67                 <filename>initrd-fs.target</filename>,
  68                 <filename>kbrequest.target</filename>,
  69                 <filename>kexec.target</filename>,
  70                 <filename>local-fs.target</filename>,
  71                 <filename>local-fs-pre.target</filename>,
  72                 <filename>multi-user.target</filename>,
  73                 <filename>network.target</filename>,
  74                 <filename>nss-lookup.target</filename>,
  75                 <filename>nss-user-lookup.target</filename>,
  76                 <filename>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>bluetooth.target</filename></term>
 143                                 <listitem>
 144                                         <para>This target is started
 145                                         automatically as soon as a
 146                                         Bluetooth controller is
 147                                         plugged in or becomes
 148                                         available at boot.</para>
 149
 150                                         <para>This may be used to pull
 151                                         in Bluetooth management
 152                                         daemons dynamically when
 153                                         Bluetooth hardware is
 154                                         found.</para>
 155                                 </listitem>
 156                         </varlistentry>
 157                         <varlistentry>
 158                                 <term><filename>ctrl-alt-del.target</filename></term>
 159                                 <listitem>
 160                                         <para>systemd starts this
 161                                         target whenever
 162                                         Control+Alt+Del is pressed on
 163                                         the console. Usually this
 164                                         should be aliased (symlinked)
 165                                         to
 166                                         <filename>reboot.target</filename>.</para>
 167                                 </listitem>
 168                         </varlistentry>
 169                         <varlistentry>
 170                                 <term><filename>cryptsetup.target</filename></term>
 171                                 <listitem>
 172                                         <para>A target that pulls in
 173                                         setup services for all
 174                                         encrypted block
 175                                         devices.</para>
 176                                 </listitem>
 177                         </varlistentry>
 178                         <varlistentry>
 179                                 <term><filename>dbus.service</filename></term>
 180                                 <listitem>
 181                                         <para>A special unit for the
 182                                         D-Bus bus daemon. As soon as
 183                                         this service is fully started
 184                                         up systemd will connect to it
 185                                         and register its
 186                                         service.</para>
 187                                 </listitem>
 188                         </varlistentry>
 189                         <varlistentry>
 190                                 <term><filename>dbus.socket</filename></term>
 191                                 <listitem>
 192                                         <para>A special unit for the
 193                                         D-Bus system bus socket. All
 194                                         units with
 195                                         <varname>Type=dbus</varname>
 196                                         automatically gain a
 197                                         dependency on this
 198                                         unit.</para>
 199                                 </listitem>
 200                         </varlistentry>
 201                         <varlistentry>
 202                                 <term><filename>default.target</filename></term>
 203                                 <listitem>
 204                                         <para>The default unit systemd
 205                                         starts at bootup. Usually this
 206                                         should be aliased (symlinked)
 207                                         to
 208                                         <filename>multi-user.target</filename>
 209                                         or
 210                                         <filename>graphical.target</filename>.</para>
 211
 212                                         <para>The default unit systemd
 213                                         starts at bootup can be
 214                                         overridden with the
 215                                         <varname>systemd.unit=</varname>
 216                                         kernel command line option.</para>
 217                                 </listitem>
 218                         </varlistentry>
 219                         <varlistentry>
 220                                 <term><filename>display-manager.service</filename></term>
 221                                 <listitem>
 222                                         <para>The display manager
 223                                         service. Usually this should
 224                                         be aliased (symlinked) to
 225                                         <filename>gdm.service</filename>
 226                                         or a similar display manager
 227                                         service.</para>
 228                                 </listitem>
 229                         </varlistentry>
 230                         <varlistentry>
 231                                 <term><filename>emergency.target</filename></term>
 232                                 <listitem>
 233                                         <para>A special target unit
 234                                         that starts an emergency
 235                                         shell on the main
 236                                         console. This unit is supposed
 237                                         to be used with the kernel
 238                                         command line option
 239                                         <varname>systemd.unit=</varname>
 240                                         and has otherwise little use.
 241                                         </para>
 242                                 </listitem>
 243                         </varlistentry>
 244                         <varlistentry>
 245                                 <term><filename>final.target</filename></term>
 246                                 <listitem>
 247                                         <para>A special target unit
 248                                         that is used during the
 249                                         shutdown logic and may be used
 250                                         to pull in late services after
 251                                         all normal services are
 252                                         already terminated and all
 253                                         mounts unmounted.
 254                                         </para>
 255                                 </listitem>
 256                         </varlistentry>
 257                         <varlistentry>
 258                                 <term><filename>getty.target</filename></term>
 259                                 <listitem>
 260                                         <para>A special target unit
 261                                         that pulls in statically
 262                                         configured local TTY
 263                                         <filename>getty</filename>
 264                                         instances.
 265                                         </para>
 266                                 </listitem>
 267                         </varlistentry>
 268                         <varlistentry>
 269                                 <term><filename>graphical.target</filename></term>
 270                                 <listitem>
 271                                         <para>A special target unit
 272                                         for setting up a graphical
 273                                         login screen. This pulls in
 274                                         <filename>multi-user.target</filename>.</para>
 275
 276                                         <para>Units that are needed
 277                                         for graphical logins shall add
 278                                         <varname>Wants=</varname>
 279                                         dependencies for their unit to
 280                                         this unit (or
 281                                         <filename>multi-user.target</filename>)
 282                                         during installation. This is
 283                                         best configured via
 284                                         <varname>WantedBy=graphical.target</varname>
 285                                         in the unit's
 286                                         <literal>[Install]</literal>
 287                                         section.</para>
 288                                 </listitem>
 289                         </varlistentry>
 290                         <varlistentry>
 291                                 <term><filename>hibernate.target</filename></term>
 292                                 <listitem>
 293                                         <para>A special target unit
 294                                         for hibernating the
 295                                         system. This pulls in
 296                                         <filename>sleep.target</filename>.</para>
 297                                 </listitem>
 298                         </varlistentry>
 299                         <varlistentry>
 300                                 <term><filename>hybrid-sleep.target</filename></term>
 301                                 <listitem>
 302                                         <para>A special target unit
 303                                         for hibernating and suspending the
 304                                         system at the same time. This pulls in
 305                                         <filename>sleep.target</filename>.</para>
 306                                 </listitem>
 307                         </varlistentry>
 308                         <varlistentry>
 309                                 <term><filename>halt.target</filename></term>
 310                                 <listitem>
 311                                         <para>A special target unit
 312                                         for shutting down and halting
 313                                         the system. Note that this
 314                                         target is distinct from
 315                                         <filename>poweroff.target</filename>
 316                                         in that it generally really
 317                                         just halts the system rather
 318                                         than powering it down.</para>
 319
 320                                         <para>Applications wanting to
 321                                         halt the system should start
 322                                         this unit.</para>
 323                                 </listitem>
 324                         </varlistentry>
 325                         <varlistentry>
 326                                 <term><filename>initrd-fs.target</filename></term>
 327                                 <listitem>
 328                                         <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 329                                         automatically adds
 330                                         dependencies of type
 331                                         <varname>Before=</varname> to
 332                                         <filename>sysroot-usr.mount</filename>
 333                                         and all mount points fround in
 334                                         <filename>/etc/fstab</filename>
 335                                         that have the
 336                                         <option>auto</option> and
 337                                         <option>x-initrd.mount</option>
 338                                         mount options set.
 339                                         </para>
 340                                 </listitem>
 341                         </varlistentry>
 342                         <varlistentry>
 343                                 <term><filename>kbrequest.target</filename></term>
 344                                 <listitem>
 345                                         <para>systemd starts this
 346                                         target whenever Alt+ArrowUp is
 347                                         pressed on the console. This
 348                                         is a good candidate to be
 349                                         aliased (symlinked) to
 350                                         <filename>rescue.target</filename>.</para>
 351                                 </listitem>
 352                         </varlistentry>
 353                         <varlistentry>
 354                                 <term><filename>kexec.target</filename></term>
 355                                 <listitem>
 356                                         <para>A special target unit
 357                                         for shutting down and rebooting the system via kexec.</para>
 358
 359                                         <para>Applications wanting to
 360                                         reboot the system with kexec should start
 361                                         this unit.</para>
 362                                 </listitem>
 363                         </varlistentry>
 364                         <varlistentry>
 365                                 <term><filename>local-fs.target</filename></term>
 366                                 <listitem>
 367                                         <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 368                                         automatically adds
 369                                         dependencies of type
 370                                         <varname>Before=</varname> to
 371                                         all mount units that refer to
 372                                         local mount points for this
 373                                         target unit. In addition, it
 374                                         adds dependencies of type
 375                                         <varname>Wants=</varname> to
 376                                         this target unit for those
 377                                         mounts listed in
 378                                         <filename>/etc/fstab</filename>
 379                                         that have the
 380                                         <option>auto</option> mount
 381                                         option set.</para>
 382                                 </listitem>
 383                         </varlistentry>
 384                         <varlistentry>
 385                                 <term><filename>local-fs-pre.target</filename></term>
 386                                 <listitem>
 387                                         <para>This target unit is
 388                                         automatically ordered before
 389                                         all local mount points marked
 390                                         with <option>auto</option>
 391                                         (see above). It can be used to
 392                                         execute certain units before
 393                                         all local mounts.</para>
 394                                 </listitem>
 395                         </varlistentry>
 396                         <varlistentry>
 397                                 <term><filename>multi-user.target</filename></term>
 398                                 <listitem>
 399                                         <para>A special target unit
 400                                         for setting up a multi-user
 401                                         system (non-graphical). This
 402                                         is pulled in by
 403                                         <filename>graphical.target</filename>.</para>
 404
 405                                         <para>Units that are needed
 406                                         for a multi-user system shall
 407                                         add <varname>Wants=</varname>
 408                                         dependencies for their unit to
 409                                         this unit during
 410                                         installation. This is best
 411                                         configured via
 412                                         <varname>WantedBy=multi-uer.target</varname>
 413                                         in the unit's
 414                                         <literal>[Install]</literal>
 415                                         section.</para>
 416                                 </listitem>
 417                         </varlistentry>
 418                         <varlistentry>
 419                                 <term><filename>network.target</filename></term>
 420                                 <listitem>
 421                                         <para>systemd automatically
 422                                         adds dependencies of type
 423                                         <varname>After=</varname> for
 424                                         this target unit to all SysV
 425                                         init script service units with
 426                                         an LSB header referring to the
 427                                         <literal>$network</literal>
 428                                         facility.</para>
 429
 430                                         <para>This unit is supposed to
 431                                         indicate when the network is
 432                                         "up", but it is only very
 433                                         loosely defined what that is
 434                                         supposed to mean. Also see <ulink
 435                                         url="http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running
 436                                         Services After the Network is
 437                                         up</ulink> for more
 438                                         information.</para>
 439                                 </listitem>
 440                         </varlistentry>
 441                         <varlistentry>
 442                                 <term><filename>nss-lookup.target</filename></term>
 443                                 <listitem>
 444                                         <para>A target that should be
 445                                         used as synchronization point
 446                                         for all host/network name
 447                                         service lookups. Note that
 448                                         this is independent of
 449                                         user/group name lookups for
 450                                         which
 451                                         <filename>nss-user-lookup.target</filename>
 452                                         should be used. systemd
 453                                         automatically adds
 454                                         dependencies of type
 455                                         <varname>After=</varname> for
 456                                         this target unit to all SysV
 457                                         init script service units with
 458                                         an LSB header referring to the
 459                                         <literal>$named</literal>
 460                                         facility.</para>
 461                                 </listitem>
 462                         </varlistentry>
 463                         <varlistentry>
 464                                 <term><filename>nss-user-lookup.target</filename></term>
 465                                 <listitem>
 466                                         <para>A target that should be
 467                                         used as synchronization point
 468                                         for all user/group name
 469                                         service lookups. Note that
 470                                         this is independent of
 471                                         host/network name lookups for
 472                                         which
 473                                         <filename>nss-lookup.target</filename>
 474                                         should be used. </para>
 475                                 </listitem>
 476                         </varlistentry>
 477                         <varlistentry>
 478                                 <term><filename>paths.target</filename></term>
 479                                 <listitem>
 480                                         <para>A special target unit
 481                                         that sets up all path units
 482                                         (see
 483                                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 484                                         for details) that shall be
 485                                         active after boot.</para>
 486
 487                                         <para>It is recommended that
 488                                         path units installed by
 489                                         applications get pulled in via
 490                                         <varname>Wants=</varname>
 491                                         dependencies from this
 492                                         unit. This is best configured
 493                                         via a
 494                                         <varname>WantedBy=paths.target</varname>
 495                                         in the path unit's
 496                                         <literal>[Install]</literal>
 497                                         section.</para>
 498                                 </listitem>
 499                         </varlistentry>
 500                         <varlistentry>
 501                                 <term><filename>poweroff.target</filename></term>
 502                                 <listitem>
 503                                         <para>A special target unit
 504                                         for shutting down and powering off the system.</para>
 505
 506                                         <para>Applications wanting to
 507                                         power off the system should start
 508                                         this unit.</para>
 509
 510                                         <para><filename>runlevel0.target</filename>
 511                                         is an alias for this target
 512                                         unit, for compatibility with SysV.</para>
 513                                 </listitem>
 514                         </varlistentry>
 515                         <varlistentry>
 516                                 <term><filename>printer.target</filename></term>
 517                                 <listitem>
 518                                         <para>This target is started
 519                                         automatically as soon as a
 520                                         printer is plugged in or
 521                                         becomes available at
 522                                         boot.</para>
 523
 524                                         <para>This may be used to pull
 525                                         in printer management
 526                                         daemons dynamically when
 527                                         printer hardware is
 528                                         found.</para>
 529                                 </listitem>
 530                         </varlistentry>
 531                         <varlistentry>
 532                                 <term><filename>reboot.target</filename></term>
 533                                 <listitem>
 534                                         <para>A special target unit
 535                                         for shutting down and rebooting the system.</para>
 536
 537                                         <para>Applications wanting to
 538                                         reboot the system should start
 539                                         this unit.</para>
 540
 541                                         <para><filename>runlevel6.target</filename>
 542                                         is an alias for this target
 543                                         unit, for compatibility with SysV.</para>
 544                                 </listitem>
 545                         </varlistentry>
 546                         <varlistentry>
 547                                 <term><filename>remote-fs.target</filename></term>
 548                                 <listitem>
 549                                         <para>Similar to
 550                                         <filename>local-fs.target</filename>,
 551                                         but for remote mount
 552                                         points.</para>
 553
 554                                         <para>systemd automatically
 555                                         adds dependencies of type
 556                                         <varname>After=</varname> for
 557                                         this target unit to all SysV
 558                                         init script service units with
 559                                         an LSB header referring to the
 560                                         <literal>$remote_fs</literal>
 561                                         facility.</para>
 562                                 </listitem>
 563                         </varlistentry>
 564                         <varlistentry>
 565                                 <term><filename>remote-fs-pre.target</filename></term>
 566                                 <listitem>
 567                                         <para>This target unit is
 568                                         automatically ordered before
 569                                         all remote mount point units
 570                                         (see above). It can be used to
 571                                         run certain units before the
 572                                         remote mounts are
 573                                         established. Note that this
 574                                         unit is generally not part of
 575                                         the initial transaction,
 576                                         unless the unit that wants to
 577                                         be ordered before all remote
 578                                         mounts pulls it in via a
 579                                         <varname>Wants=</varname> type
 580                                         dependency. If the unit wants
 581                                         to be pulled in by the first
 582                                         remote mount showing up it
 583                                         should use
 584                                         <filename>remote-fs-setup.target</filename>
 585                                         (see below).</para>
 586
 587                                         <para>Again, this target unit
 588                                         is <emphasis>not</emphasis>
 589                                         suitable for pulling in other
 590                                         units, it is only useful for
 591                                         ordering.</para>
 592                                 </listitem>
 593                         </varlistentry>
 594                         <varlistentry>
 595                                 <term><filename>remote-fs-setup.target</filename></term>
 596                                 <listitem>
 597                                         <para>This target unit is
 598                                         automatically pulled in (by a
 599                                         <varname>Wants=</varname> type
 600                                         dependency) by all remote
 601                                         mount points. It can be used
 602                                         to run certain units when at
 603                                         least one remote file system
 604                                         is to be mounted. Note that
 605                                         this target is not ordered
 606                                         against the remote mounts, use
 607                                         <filename>remote-fs-pre.target</filename>
 608                                         for that.</para>
 609
 610                                         <para>Again, this target unit
 611                                         is <emphasis>not</emphasis>
 612                                         suitable for ordering, it is
 613                                         only useful for pulling in
 614                                         other units.</para>
 615                                 </listitem>
 616                         </varlistentry>
 617                         <varlistentry>
 618                                 <term><filename>rescue.target</filename></term>
 619                                 <listitem>
 620                                         <para>A special target unit
 621                                         for setting up the base system
 622                                         and a rescue shell.</para>
 623
 624                                         <para><filename>runlevel1.target</filename>
 625                                         is an alias for this target
 626                                         unit, for compatibility with SysV.</para>
 627                                 </listitem>
 628                         </varlistentry>
 629                         <varlistentry>
 630                                 <term><filename>initrd-root-fs.target</filename></term>
 631                                 <listitem>
 632                                         <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 633                                         automatically adds
 634                                         dependencies of type
 635                                         <varname>Before=</varname> to
 636                                         the
 637                                         <filename>sysroot.mount</filename>
 638                                         unit, which is generated from
 639                                         the kernel command line.
 640                                         </para>
 641                                 </listitem>
 642                         </varlistentry>
 643                         <varlistentry>
 644                                 <term><filename>rpcbind.target</filename></term>
 645                                 <listitem>
 646                                         <para>systemd automatically
 647                                         adds dependencies of type
 648                                         <varname>After=</varname> for
 649                                         this target unit to all SysV
 650                                         init script service units with
 651                                         an LSB header referring to the
 652                                         <literal>$portmap</literal>
 653                                         facility.</para>
 654                                 </listitem>
 655                         </varlistentry>
 656                         <varlistentry>
 657                                 <term><filename>runlevel2.target</filename></term>
 658                                 <term><filename>runlevel3.target</filename></term>
 659                                 <term><filename>runlevel4.target</filename></term>
 660                                 <term><filename>runlevel5.target</filename></term>
 661                                 <listitem>
 662                                         <para>These are targets that
 663                                         are called whenever the SysV
 664                                         compatibility code asks for
 665                                         runlevel 2, 3, 4, 5,
 666                                         respectively. It is a good
 667                                         idea to make this an alias for
 668                                         (i.e. symlink to)
 669                                         <filename>multi-user.target</filename>
 670                                         (for runlevel 2) or
 671                                         <filename>graphical.target</filename>
 672                                         (the others).</para>
 673                                 </listitem>
 674                         </varlistentry>
 675                         <varlistentry>
 676                                 <term><filename>shutdown.target</filename></term>
 677                                 <listitem>
 678                                         <para>A special target unit
 679                                         that terminates the services
 680                                         on system shutdown.</para>
 681
 682                                         <para>Services that shall be
 683                                         terminated on system shutdown
 684                                         shall add <varname>Conflicts=</varname>
 685                                         dependencies to this unit for
 686                                         their service unit, which is
 687                                         implicitly done when
 688                                         <varname>DefaultDependencies=yes</varname>
 689                                         is set (the default).</para>
 690                                 </listitem>
 691                         </varlistentry>
 692                         <varlistentry>
 693                                 <term><filename>sigpwr.target</filename></term>
 694                                 <listitem>
 695                                         <para>A special target that is
 696                                         started when systemd receives
 697                                         the SIGPWR process signal,
 698                                         which is normally sent by the
 699                                         kernel or UPS daemons when
 700                                         power fails.</para>
 701                                 </listitem>
 702                         </varlistentry>
 703                         <varlistentry>
 704                                 <term><filename>sleep.target</filename></term>
 705                                 <listitem>
 706                                         <para>A special target unit
 707                                         that is pulled in by
 708                                         <filename>suspend.target</filename>,
 709                                         <filename>hibernate.target</filename>
 710                                         and
 711                                         <filename>hybrid-sleep.target</filename>
 712                                         and may be used to hook units
 713                                         into the sleep state
 714                                         logic.</para>
 715                                 </listitem>
 716                         </varlistentry>
 717                         <varlistentry>
 718                                 <term><filename>smartcard.target</filename></term>
 719                                 <listitem>
 720                                         <para>This target is started
 721                                         automatically as soon as a
 722                                         smartcard controller is
 723                                         plugged in or becomes
 724                                         available at boot.</para>
 725
 726                                         <para>This may be used to pull
 727                                         in printer management
 728                                         daemons dynamically when
 729                                         smartcard hardware is
 730                                         found.</para>
 731                                 </listitem>
 732                         </varlistentry>
 733                         <varlistentry>
 734                                 <term><filename>sockets.target</filename></term>
 735                                 <listitem>
 736                                         <para>A special target unit
 737                                         that sets up all socket
 738                                         units.(see
 739                                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 740                                         for details) that shall be
 741                                         active after boot.</para>
 742
 743                                         <para>Services that can be
 744                                         socket-activated shall add
 745                                         <varname>Wants=</varname>
 746                                         dependencies to this unit for
 747                                         their socket unit during
 748                                         installation. This is best
 749                                         configured via a
 750                                         <varname>WantedBy=sockets.target</varname>
 751                                         in the socket unit's
 752                                         <literal>[Install]</literal>
 753                                         section.</para>
 754                                 </listitem>
 755                         </varlistentry>
 756                         <varlistentry>
 757                                 <term><filename>sound.target</filename></term>
 758                                 <listitem>
 759                                         <para>This target is started
 760                                         automatically as soon as a
 761                                         sound card is plugged in or
 762                                         becomes available at
 763                                         boot.</para>
 764
 765                                         <para>This may be used to pull
 766                                         in audio management daemons
 767                                         dynamically when printer
 768                                         hardware is found.</para>
 769                                 </listitem>
 770                         </varlistentry>
 771                         <varlistentry>
 772                                 <term><filename>suspend.target</filename></term>
 773                                 <listitem>
 774                                         <para>A special target unit
 775                                         for suspending the
 776                                         system. This pulls in
 777                                         <filename>sleep.target</filename>.</para>
 778                                 </listitem>
 779                         </varlistentry>
 780                         <varlistentry>
 781                                 <term><filename>swap.target</filename></term>
 782                                 <listitem>
 783                                         <para>Similar to
 784                                         <filename>local-fs.target</filename>, but for swap
 785                                         partitions and swap
 786                                         files.</para>
 787                                 </listitem>
 788                         </varlistentry>
 789                         <varlistentry>
 790                                 <term><filename>sysinit.target</filename></term>
 791                                 <listitem>
 792                                         <para>A special target unit
 793                                         covering early boot-up scripts.</para>
 794                                 </listitem>
 795                         </varlistentry>
 796                         <varlistentry>
 797                                 <term><filename>syslog.socket</filename></term>
 798                                 <listitem>
 799                                         <para>The socket unit
 800                                         syslog implementations should
 801                                         listen on. All userspace log
 802                                         messages will be made
 803                                         available on this socket. For
 804                                         more information about syslog
 805                                         integration, please consult
 806                                         the <ulink
 807                                         url="http://www.freedesktop.org/wiki/Software/systemd/syslog">Syslog
 808                                         Interface</ulink>
 809                                         document.</para>
 810                                 </listitem>
 811                         </varlistentry>
 812                         <varlistentry>
 813                                 <term><filename>system-update.target</filename></term>
 814                                 <listitem>
 815                                         <para>A special target unit
 816                                         that is used for off-line
 817                                         system updates.
 818                                         <citerefentry><refentrytitle>systemd-system-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 819                                         will redirect the boot process
 820                                         to this target if
 821                                         <filename>/system-update</filename>
 822                                         exists. For more information
 823                                         see the <ulink
 824                                         url="http://freedesktop.org/wiki/Software/systemd/SystemUpdates">System
 825                                         Updates
 826                                         Specification</ulink>.</para>
 827                                 </listitem>
 828                         </varlistentry>
 829                         <varlistentry>
 830                                 <term><filename>time-sync.target</filename></term>
 831                                 <listitem>
 832                                         <para>systemd automatically
 833                                         adds dependencies of type
 834                                         <varname>After=</varname> for
 835                                         this target unit to all SysV
 836                                         init script service units with
 837                                         an LSB header referring to the
 838                                         <literal>$time</literal>
 839                                         facility.</para>
 840                                 </listitem>
 841                         </varlistentry>
 842                         <varlistentry>
 843                                 <term><filename>timers.target</filename></term>
 844                                 <listitem>
 845                                         <para>A special target unit
 846                                         that sets up all timer
 847                                         units (see
 848                                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 849                                         for details) that shall be
 850                                         active after boot.</para>
 851
 852                                         <para>It is recommended that
 853                                         timer units installed by
 854                                         applications get pulled in via
 855                                         <varname>Wants=</varname>
 856                                         dependencies from this
 857                                         unit. This is best configured
 858                                         via
 859                                         <varname>WantedBy=timers.target</varname>
 860                                         in the timer unit's
 861                                         <literal>[Install]</literal>
 862                                         section.</para>
 863                                 </listitem>
 864                         </varlistentry>
 865                         <varlistentry>
 866                                 <term><filename>umount.target</filename></term>
 867                                 <listitem>
 868                                         <para>A special target unit
 869                                         that umounts all mount and
 870                                         automount points on system
 871                                         shutdown.</para>
 872
 873                                         <para>Mounts that shall be
 874                                         unmounted on system shutdown
 875                                         shall add Conflicts
 876                                         dependencies to this unit for
 877                                         their mount unit, which is
 878                                         implicitly done when
 879                                         <varname>DefaultDependencies=yes</varname>
 880                                         is set (the default).</para>
 881                                 </listitem>
 882                         </varlistentry>
 883
 884                 </variablelist>
 885         </refsect1>
 886
 887         <refsect1>
 888                 <title>Special User Units</title>
 889
 890                 <para>When systemd runs as a user instance, the
 891                 following special units are available, which have
 892                 similar definitions as their system counterparts:
 893                 <filename>default.target</filename>,
 894                 <filename>shutdown.target</filename>,
 895                 <filename>sockets.target</filename></para>
 896
 897                 <para>In addition the following special unit is
 898                 understood only when systemd runs as service instance:</para>
 899
 900                 <variablelist>
 901                         <varlistentry>
 902                                 <term><filename>exit.target</filename></term>
 903                                 <listitem>
 904                                         <para>A special service unit
 905                                         for shutting down the
 906                                         user service manager.</para>
 907
 908                                         <para>Applications wanting to
 909                                         terminate the user service
 910                                         manager should start this
 911                                         unit. If systemd receives
 912                                         SIGTERM or SIGINT when running
 913                                         as user service daemon it will
 914                                         start this unit.</para>
 915
 916                                         <para>Normally, this pulls in
 917                                         <filename>shutdown.target</filename>
 918                                         which in turn should be
 919                                         conflicted by all units that
 920                                         want to be shut down on
 921                                         user service manager exit.</para>
 922                                 </listitem>
 923                         </varlistentry>
 924                 </variablelist>
 925         </refsect1>
 926
 927         <refsect1>
 928                   <title>See Also</title>
 929                   <para>
 930                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 931                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 932                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 933                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 934                           <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 935                           <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 936                           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 937                   </para>
 938         </refsect1>
 939
 940 </refentry>