man/systemd.special.xml

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  23
  24 <refentry id="systemd.special">
  25
  26         <refentryinfo>
  27                 <title>systemd.special</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.special</refentrytitle>
  42                 <manvolnum>7</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.special</refname>
  47                 <refpurpose>Special systemd units</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename>basic.target</filename>,
  52                 <filename>bluetooth.target</filename>,
  53                 <filename>ctrl-alt-del.target</filename>,
  54                 <filename>cryptsetup.target</filename>,
  55                 <filename>dbus.service</filename>,
  56                 <filename>dbus.socket</filename>,
  57                 <filename>default.target</filename>,
  58                 <filename>display-manager.service</filename>,
  59                 <filename>emergency.target</filename>,
  60                 <filename>exit.target</filename>,
  61                 <filename>final.target</filename>,
  62                 <filename>getty.target</filename>,
  63                 <filename>graphical.target</filename>,
  64                 <filename>hibernate.target</filename>,
  65                 <filename>http-daemon.target</filename>,
  66                 <filename>hybrid-sleep.target</filename>,
  67                 <filename>halt.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>mail-transfer-agent.target</filename>,
  73                 <filename>multi-user.target</filename>,
  74                 <filename>network.target</filename>,
  75                 <filename>nss-lookup.target</filename>,
  76                 <filename>nss-user-lookup.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>rpcbind.target</filename>,
  84                 <filename>runlevel2.target</filename>,
  85                 <filename>runlevel3.target</filename>,
  86                 <filename>runlevel4.target</filename>,
  87                 <filename>runlevel5.target</filename>,
  88                 <filename>shutdown.target</filename>,
  89                 <filename>sigpwr.target</filename>,
  90                 <filename>sleep.target</filename>,
  91                 <filename>smartcard.target</filename>,
  92                 <filename>sockets.target</filename>,
  93                 <filename>sound.target</filename>,
  94                 <filename>suspend.target</filename>,
  95                 <filename>swap.target</filename>,
  96                 <filename>sysinit.target</filename>,
  97                 <filename>syslog.socket</filename>,
  98                 <filename>syslog.target</filename>,
  99                 <filename>system-update.target</filename>,
 100                 <filename>time-sync.target</filename>,
 101                 <filename>umount.target</filename></para>
 102         </refsynopsisdiv>
 103
 104         <refsect1>
 105                 <title>Description</title>
 106
 107                 <para>A few units are treated specially by
 108                 systemd. They have special internal semantics and
 109                 cannot be renamed.</para>
 110         </refsect1>
 111
 112         <refsect1>
 113                 <title>Special System Units</title>
 114
 115                 <variablelist>
 116                         <varlistentry>
 117                                 <term><filename>basic.target</filename></term>
 118                                 <listitem>
 119                                         <para>A special target unit
 120                                         covering early boot-up.</para>
 121                                         <para>systemd automatically
 122                                         adds dependencies of the types
 123                                         Requires and After for this
 124                                         target unit to all SysV
 125                                         service units configured for
 126                                         runlevel 1 to 5.</para>
 127                                         <para>Usually this should pull-in
 128                                         all sockets, mount points,
 129                                         swap devices and other basic
 130                                         initialization necessary for
 131                                         the general purpose
 132                                         daemons. Most normal daemons
 133                                         should have dependencies of
 134                                         type After and Requires on
 135                                         this unit.</para>
 136                                 </listitem>
 137                         </varlistentry>
 138                         <varlistentry>
 139                                 <term><filename>bluetooth.target</filename></term>
 140                                 <listitem>
 141                                         <para>This target is started
 142                                         automatically as soon as a
 143                                         bluetooth controller is
 144                                         plugged in or becomes
 145                                         available at boot.</para>
 146                                 </listitem>
 147                         </varlistentry>
 148                         <varlistentry>
 149                                 <term><filename>ctrl-alt-del.target</filename></term>
 150                                 <listitem>
 151                                         <para>systemd starts this
 152                                         target whenever
 153                                         Control+Alt+Del is pressed on
 154                                         the console. Usually this
 155                                         should be aliased (symlinked)
 156                                         to
 157                                         <filename>reboot.target</filename>.</para>
 158                                 </listitem>
 159                         </varlistentry>
 160                         <varlistentry>
 161                                 <term><filename>cryptsetup.target</filename></term>
 162                                 <listitem>
 163                                         <para>A target that pulls in
 164                                         setup services for all
 165                                         encrypted block
 166                                         devices.</para>
 167                                 </listitem>
 168                         </varlistentry>
 169                         <varlistentry>
 170                                 <term><filename>dbus.service</filename></term>
 171                                 <listitem>
 172                                         <para>A special unit for the
 173                                         D-Bus system bus. As soon as
 174                                         this service is fully started
 175                                         up systemd will connect to it
 176                                         and register its
 177                                         service.</para>
 178                                 </listitem>
 179                         </varlistentry>
 180                         <varlistentry>
 181                                 <term><filename>dbus.socket</filename></term>
 182                                 <listitem>
 183                                         <para>A special unit for the
 184                                         D-Bus system bus socket. All
 185                                         units with
 186                                         <literal>Type=dbus</literal>
 187                                         automatically gain a
 188                                         dependency on this
 189                                         unit.</para>
 190                                 </listitem>
 191                         </varlistentry>
 192                         <varlistentry>
 193                                 <term><filename>default.target</filename></term>
 194                                 <listitem>
 195                                         <para>The default unit systemd
 196                                         starts at bootup. Usually this
 197                                         should be aliased (symlinked)
 198                                         to
 199                                         <filename>multi-user.target</filename>
 200                                         or
 201                                         <filename>graphical.target</filename>.</para>
 202                                         <para>The default unit systemd
 203                                         starts at bootup can be
 204                                         overridden with the
 205                                         <varname>systemd.unit=</varname>
 206                                         kernel command line option.</para>
 207                                 </listitem>
 208                         </varlistentry>
 209                         <varlistentry>
 210                                 <term><filename>display-manager.service</filename></term>
 211                                 <listitem>
 212                                         <para>The display manager
 213                                         service. Usually this should
 214                                         be aliased (symlinked) to
 215                                         <filename>gdm.service</filename>
 216                                         or a similar display manager
 217                                         service.</para>
 218                                         <para>systemd automatically
 219                                         adds dependencies of type
 220                                         After for this target unit to
 221                                         all SysV init script service
 222                                         units with a LSB header
 223                                         referring to the
 224                                         <literal>$x-display-manager</literal>
 225                                         facility, for compatibility
 226                                         with Debian.</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 all local TTY
 261                                         <filename>getty</filename> instances.
 262                                         </para>
 263                                 </listitem>
 264                         </varlistentry>
 265                         <varlistentry>
 266                                 <term><filename>graphical.target</filename></term>
 267                                 <listitem>
 268                                         <para>A special target unit
 269                                         for setting up a graphical
 270                                         login screen. This pulls in
 271                                         <filename>multi-user.target</filename>.</para>
 272
 273                                         <para>Units that are needed
 274                                         for graphical login shall add
 275                                         Wants dependencies for their
 276                                         unit to this unit (or
 277                                         <filename>multi-user.target</filename>)
 278                                         during installation.</para>
 279                                 </listitem>
 280                         </varlistentry>
 281                         <varlistentry>
 282                                 <term><filename>hibernate.target</filename></term>
 283                                 <listitem>
 284                                         <para>A special target unit
 285                                         for hibernating the
 286                                         system. This pulls in
 287                                         <filename>sleep.target</filename>.</para>
 288                                 </listitem>
 289                         </varlistentry>
 290                         <varlistentry>
 291                                 <term><filename>http-daemon.target</filename></term>
 292                                 <listitem>
 293                                         <para>A target for pulling in
 294                                         an HTTP server if there is
 295                                         any.</para>
 296                                         <para>systemd automatically
 297                                         adds dependencies of type
 298                                         After for this target unit to
 299                                         all SysV init script service
 300                                         units with a LSB header
 301                                         referring to the
 302                                         <literal>$httpd</literal>
 303                                         facility.</para>
 304                                 </listitem>
 305                         </varlistentry>
 306                         <varlistentry>
 307                                 <term><filename>hybrid-sleep.target</filename></term>
 308                                 <listitem>
 309                                         <para>A special target unit
 310                                         for hibernating and suspending the
 311                                         system at the same time. This pulls in
 312                                         <filename>sleep.target</filename>.</para>
 313                                 </listitem>
 314                         </varlistentry>
 315                         <varlistentry>
 316                                 <term><filename>halt.target</filename></term>
 317                                 <listitem>
 318                                         <para>A special target unit
 319                                         for shutting down and halting the system.</para>
 320
 321                                         <para>Applications wanting to
 322                                         halt the system should start
 323                                         this unit.</para>
 324                                 </listitem>
 325                         </varlistentry>
 326                         <varlistentry>
 327                                 <term><filename>kbrequest.target</filename></term>
 328                                 <listitem>
 329                                         <para>systemd starts this
 330                                         target whenever Alt+ArrowUp is
 331                                         pressed on the console. This
 332                                         is a good candidate to be
 333                                         aliased (symlinked) to
 334                                         <filename>rescue.target</filename>.</para>
 335                                 </listitem>
 336                         </varlistentry>
 337                         <varlistentry>
 338                                 <term><filename>kexec.target</filename></term>
 339                                 <listitem>
 340                                         <para>A special target unit
 341                                         for shutting down and rebooting the system via kexec.</para>
 342
 343                                         <para>Applications wanting to
 344                                         reboot the system with kexec should start
 345                                         this unit.</para>
 346                                 </listitem>
 347                         </varlistentry>
 348                         <varlistentry>
 349                                 <term><filename>local-fs.target</filename></term>
 350                                 <listitem>
 351                                         <para>systemd automatically
 352                                         adds dependencies of type
 353                                         After to all mount units that
 354                                         refer to local mount points
 355                                         for this target unit. In
 356                                         addition, systemd adds
 357                                         dependencies of type Wants to
 358                                         this target unit for those
 359                                         mounts listed in
 360                                         <filename>/etc/fstab</filename>
 361                                         that have the
 362                                         <option>auto</option> and
 363                                         <option>comment=systemd.mount</option>
 364                                         mount options set.</para>
 365
 366                                         <para>systemd automatically
 367                                         adds dependencies of type
 368                                         After for this target unit to
 369                                         all SysV init script service
 370                                         units with an LSB header
 371                                         referring to the
 372                                         <literal>$local_fs</literal>
 373                                         facility.</para>
 374                                 </listitem>
 375                         </varlistentry>
 376                         <varlistentry>
 377                                 <term><filename>local-fs-pre.target</filename></term>
 378                                 <listitem>
 379                                         <para>This target unit is
 380                                         automatically ordered before
 381                                         all local mount points marked
 382                                         with <option>auto</option>
 383                                         (see above). It can be used to
 384                                         execute certain units before
 385                                         all local mounts.</para>
 386                                 </listitem>
 387                         </varlistentry>
 388                         <varlistentry>
 389                                 <term><filename>mail-transfer-agent.target</filename></term>
 390                                 <listitem>
 391                                         <para>The mail transfer agent
 392                                         (MTA) service. Usually this
 393                                         should pull-in all units
 394                                         necessary for
 395                                         sending/receiving mails on the
 396                                         local host.</para>
 397
 398                                         <para>systemd automatically
 399                                         adds dependencies of type
 400                                         After for this target unit to
 401                                         all SysV init script service
 402                                         units with an LSB header
 403                                         referring to the
 404                                         <literal>$mail-transfer-agent</literal>
 405                                         or
 406                                         <literal>$mail-transport-agent</literal>
 407                                         facilities, for compatibility
 408                                         with Debian.</para>
 409                                 </listitem>
 410                         </varlistentry>
 411                         <varlistentry>
 412                                 <term><filename>multi-user.target</filename></term>
 413                                 <listitem>
 414                                         <para>A special target unit
 415                                         for setting up a multi-user
 416                                         system (non-graphical). This
 417                                         is pulled in by
 418                                         <filename>graphical.target</filename>.</para>
 419
 420                                         <para>Units that are needed
 421                                         for a multi-user system shall
 422                                         add Wants dependencies to
 423                                         this unit for their unit during
 424                                         installation.</para>
 425                                 </listitem>
 426                         </varlistentry>
 427                         <varlistentry>
 428                                 <term><filename>network.target</filename></term>
 429                                 <listitem>
 430                                         <para>systemd automatically
 431                                         adds dependencies of type
 432                                         After for this target unit to
 433                                         all SysV init script service
 434                                         units with an LSB header
 435                                         referring to the
 436                                         <literal>$network</literal>
 437                                         facility.</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 After for
 454                                         this target unit to all SysV
 455                                         init script service units with
 456                                         an LSB header referring to the
 457                                         <literal>$named</literal>
 458                                         facility.</para>
 459                                 </listitem>
 460                         </varlistentry>
 461                         <varlistentry>
 462                                 <term><filename>nss-user-lookup.target</filename></term>
 463                                 <listitem>
 464                                         <para>A target that should be
 465                                         used as synchronization point
 466                                         for all user/group name
 467                                         service lookups. Note that
 468                                         this is independent of
 469                                         host/network name lookups for
 470                                         which
 471                                         <filename>nss-lookup.target</filename>
 472                                         should be used. </para>
 473                                 </listitem>
 474                         </varlistentry>
 475                         <varlistentry>
 476                                 <term><filename>poweroff.target</filename></term>
 477                                 <listitem>
 478                                         <para>A special target unit
 479                                         for shutting down and powering off the system.</para>
 480
 481                                         <para>Applications wanting to
 482                                         power off the system should start
 483                                         this unit.</para>
 484
 485                                         <para><filename>runlevel0.target</filename>
 486                                         is an alias for this target
 487                                         unit, for compatibility with SysV.</para>
 488                                 </listitem>
 489                         </varlistentry>
 490                         <varlistentry>
 491                                 <term><filename>printer.target</filename></term>
 492                                 <listitem>
 493                                         <para>This target is started
 494                                         automatically as soon as a
 495                                         printer is plugged in or
 496                                         becomes available at
 497                                         boot.</para>
 498                                 </listitem>
 499                         </varlistentry>
 500                         <varlistentry>
 501                                 <term><filename>reboot.target</filename></term>
 502                                 <listitem>
 503                                         <para>A special target unit
 504                                         for shutting down and rebooting the system.</para>
 505
 506                                         <para>Applications wanting to
 507                                         reboot the system should start
 508                                         this unit.</para>
 509
 510                                         <para><filename>runlevel6.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>remote-fs.target</filename></term>
 517                                 <listitem>
 518                                         <para>Similar to
 519                                         <filename>local-fs.target</filename>,
 520                                         but for remote mount
 521                                         points.</para>
 522
 523                                         <para>systemd automatically
 524                                         adds dependencies of type
 525                                         After for this target unit to
 526                                         all SysV init script service
 527                                         units with an LSB header
 528                                         referring to the
 529                                         <literal>$remote_fs</literal>
 530                                         facility.</para>
 531                                 </listitem>
 532                         </varlistentry>
 533                         <varlistentry>
 534                                 <term><filename>remote-fs-pre.target</filename></term>
 535                                 <listitem>
 536                                         <para>This target unit is
 537                                         automatically ordered before
 538                                         all remote mount points marked
 539                                         with <option>auto</option>
 540                                         (see above). It can be used to
 541                                         execute certain units before
 542                                         all remote mounts.</para>
 543                                 </listitem>
 544                         </varlistentry>
 545                         <varlistentry>
 546                                 <term><filename>rescue.target</filename></term>
 547                                 <listitem>
 548                                         <para>A special target unit
 549                                         for setting up the base system
 550                                         and a rescue shell.</para>
 551
 552                                         <para><filename>runlevel1.target</filename>
 553                                         is an alias for this target
 554                                         unit, for compatibility with SysV.</para>
 555                                 </listitem>
 556                         </varlistentry>
 557                         <varlistentry>
 558                                 <term><filename>rpcbind.target</filename></term>
 559                                 <listitem>
 560                                         <para>systemd automatically
 561                                         adds dependencies of type
 562                                         After for this target unit to
 563                                         all SysV init script service
 564                                         units with an LSB header
 565                                         referring to the
 566                                         <literal>$portmap</literal>
 567                                         facility.</para>
 568                                 </listitem>
 569                         </varlistentry>
 570                         <varlistentry>
 571                                 <term><filename>runlevel2.target</filename></term>
 572                                 <listitem>
 573                                         <para>This is a target that is
 574                                         called whenever the SysV
 575                                         compatibility code asks for
 576                                         runlevel 2. It is a good idea
 577                                         to make this an alias for
 578                                         (i.e. symlink to)
 579                                         <filename>multi-user.target</filename>.</para>
 580                                 </listitem>
 581                         </varlistentry>
 582                         <varlistentry>
 583                                 <term><filename>runlevel3.target</filename></term>
 584                                 <listitem>
 585                                         <para>This is a target that is
 586                                         called whenever the SysV
 587                                         compatibility code asks for
 588                                         runlevel 3. It is a good idea
 589                                         to make this an alias for
 590                                         (i.e. symlink to)
 591                                         <filename>multi-user.target</filename>
 592                                         or
 593                                         <filename>graphical.target</filename>.</para>
 594                                 </listitem>
 595                         </varlistentry>
 596                         <varlistentry>
 597                                 <term><filename>runlevel4.target</filename></term>
 598                                 <listitem>
 599                                         <para>This is a target that is
 600                                         called whenever the SysV
 601                                         compatibility code asks for
 602                                         runlevel 4. It is a good idea
 603                                         to make this an alias for
 604                                         (i.e. symlink to)
 605                                         <filename>multi-user.target</filename>
 606                                         or
 607                                         <filename>graphical.target</filename>.</para>
 608                                 </listitem>
 609                         </varlistentry>
 610                         <varlistentry>
 611                                 <term><filename>runlevel5.target</filename></term>
 612                                 <listitem>
 613                                         <para>This is a target that is
 614                                         called whenever the SysV
 615                                         compatibility code asks for
 616                                         runlevel 5. It is a good idea
 617                                         to make this an alias for
 618                                         (i.e. symlink to)
 619                                         <filename>multi-user.target</filename>
 620                                         or
 621                                         <filename>graphical.target</filename>.</para>
 622                                 </listitem>
 623                         </varlistentry>
 624                         <varlistentry>
 625                                 <term><filename>shutdown.target</filename></term>
 626                                 <listitem>
 627                                         <para>A special target unit
 628                                         that terminates the services
 629                                         on system shutdown.</para>
 630
 631                                         <para>Services that shall be
 632                                         terminated on system shutdown
 633                                         shall add Conflicts
 634                                         dependencies to this unit for
 635                                         their service unit, which is
 636                                         implicitly done when
 637                                         <varname>DefaultDependencies=yes</varname>
 638                                         is set (the default).</para>
 639
 640                                         <para>systemd automatically
 641                                         adds dependencies of type
 642                                         Conflicts to this target unit
 643                                         for all SysV init script
 644                                         service units that shall be
 645                                         terminated in SysV runlevels 0
 646                                         or 6.</para>
 647                                 </listitem>
 648                         </varlistentry>
 649                         <varlistentry>
 650                                 <term><filename>sigpwr.target</filename></term>
 651                                 <listitem>
 652                                         <para>A special target that is
 653                                         started when systemd receives
 654                                         the SIGPWR process signal,
 655                                         which is normally sent by the
 656                                         kernel or UPS daemons when
 657                                         power fails.</para>
 658                                 </listitem>
 659                         </varlistentry>
 660                         <varlistentry>
 661                                 <term><filename>sleep.target</filename></term>
 662                                 <listitem>
 663                                         <para>A special target unit
 664                                         that is pulled in by
 665                                         <filename>suspend.target</filename>,
 666                                         <filename>hibernate.target</filename> and <filename>hybrid-sleep.target</filename>
 667                                         and may be used to hook units
 668                                         into the sleep state
 669                                         logic.</para>
 670                                 </listitem>
 671                         </varlistentry>
 672                         <varlistentry>
 673                                 <term><filename>smartcard.target</filename></term>
 674                                 <listitem>
 675                                         <para>This target is started
 676                                         automatically as soon as a
 677                                         smartcard controller is
 678                                         plugged in or becomes
 679                                         available at boot.</para>
 680                                 </listitem>
 681                         </varlistentry>
 682                         <varlistentry>
 683                                 <term><filename>sockets.target</filename></term>
 684                                 <listitem>
 685                                         <para>A special target unit
 686                                         that sets up all service
 687                                         sockets.</para>
 688
 689                                         <para>Services that can be
 690                                         socket-activated shall add
 691                                         Wants dependencies to this
 692                                         unit for their socket unit
 693                                         during installation.</para>
 694                                 </listitem>
 695                         </varlistentry>
 696                         <varlistentry>
 697                                 <term><filename>sound.target</filename></term>
 698                                 <listitem>
 699                                         <para>This target is started
 700                                         automatically as soon as a
 701                                         sound card is plugged in or
 702                                         becomes available at
 703                                         boot.</para>
 704                                 </listitem>
 705                         </varlistentry>
 706                         <varlistentry>
 707                                 <term><filename>suspend.target</filename></term>
 708                                 <listitem>
 709                                         <para>A special target unit
 710                                         for suspending the
 711                                         system. This pulls in
 712                                         <filename>sleep.target</filename>.</para>
 713                                 </listitem>
 714                         </varlistentry>
 715                         <varlistentry>
 716                                 <term><filename>swap.target</filename></term>
 717                                 <listitem>
 718                                         <para>Similar to
 719                                         <filename>local-fs.target</filename>, but for swap
 720                                         partitions and swap
 721                                         files.</para>
 722                                 </listitem>
 723                         </varlistentry>
 724                         <varlistentry>
 725                                 <term><filename>sysinit.target</filename></term>
 726                                 <listitem>
 727                                         <para>A special target unit
 728                                         covering early boot-up scripts.</para>
 729                                         <para>systemd automatically
 730                                         adds dependencies of the types
 731                                         Wants and After for all
 732                                         SysV service units configured
 733                                         for runlevels that are not 0
 734                                         to 6 to this target unit.
 735                                         This covers the special
 736                                         boot-up runlevels some
 737                                         distributions have, such as S
 738                                         or b.</para>
 739                                 </listitem>
 740                         </varlistentry>
 741                         <varlistentry>
 742                                 <term><filename>syslog.socket</filename></term>
 743                                 <listitem>
 744                                         <para>The socket unit where
 745                                         syslog implementations should
 746                                         listen on. All userspace log
 747                                         messages will be made
 748                                         available on this socket. For
 749                                         more information about syslog
 750                                         integration, please consult
 751                                         the <ulink
 752                                         url="http://www.freedesktop.org/wiki/Software/systemd/syslog">Syslog
 753                                         Interface</ulink>
 754                                         document.</para>
 755                                 </listitem>
 756                         </varlistentry>
 757                         <varlistentry>
 758                                 <term><filename>syslog.target</filename></term>
 759                                 <listitem>
 760                                         <para>systemd automatically
 761                                         adds dependencies of type
 762                                         After for this target unit to
 763                                         all SysV init script service
 764                                         units with an LSB header
 765                                         referring to the
 766                                         <literal>$syslog</literal>
 767                                         facility.</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                                         After for this target unit to
 793                                         all SysV init script service
 794                                         units with an LSB header
 795                                         referring to the
 796                                         <literal>$time</literal>
 797                                         facility.</para>
 798                                 </listitem>
 799                         </varlistentry>
 800                         <varlistentry>
 801                                 <term><filename>umount.target</filename></term>
 802                                 <listitem>
 803                                         <para>A special target unit
 804                                         that umounts all mount and
 805                                         automount points on system
 806                                         shutdown.</para>
 807
 808                                         <para>Mounts that shall be
 809                                         unmounted on system shutdown
 810                                         shall add Conflicts
 811                                         dependencies to this unit for
 812                                         their mount unit, which is
 813                                         implicitly done when
 814                                         <varname>DefaultDependencies=yes</varname>
 815                                         is set (the default).</para>
 816                                 </listitem>
 817                         </varlistentry>
 818
 819                 </variablelist>
 820         </refsect1>
 821
 822         <refsect1>
 823                 <title>Special User Units</title>
 824
 825                 <para>When systemd runs as a user instance, the
 826                 following special units are available, which have
 827                 similar definitions as their system counterparts:
 828                 <filename>default.target</filename>,
 829                 <filename>shutdown.target</filename>,
 830                 <filename>sockets.target</filename></para>
 831
 832                 <para>In addition the following special unit is
 833                 understood only when systemd runs as service instance:</para>
 834
 835                 <variablelist>
 836                         <varlistentry>
 837                                 <term><filename>exit.target</filename></term>
 838                                 <listitem>
 839                                         <para>A special service unit
 840                                         for shutting down the
 841                                         user service manager.</para>
 842
 843                                         <para>Applications wanting to
 844                                         terminate the user service
 845                                         manager should start this
 846                                         unit. If systemd receives
 847                                         SIGTERM or SIGINT when running
 848                                         as user service daemon it will
 849                                         start this unit.</para>
 850
 851                                         <para>Normally, this pulls in
 852                                         <filename>shutdown.target</filename>
 853                                         which in turn should be
 854                                         conflicted by all units that
 855                                         want to be shut down on
 856                                         user service manager exit.</para>
 857                                 </listitem>
 858                         </varlistentry>
 859                 </variablelist>
 860         </refsect1>
 861
 862         <refsect1>
 863                   <title>See Also</title>
 864                   <para>
 865                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 866                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 867                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 868                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 869                           <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 870                           <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 871                   </para>
 872         </refsect1>
 873
 874 </refentry>