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.service</filename>,
  61                 <filename>final.service</filename>,
  62                 <filename>getty.target</filename>,
  63                 <filename>graphical.target</filename>,
  64                 <filename>hibernate.target</filename>,
  65                 <filename>http-daemon.target</filename>,
  66                 <filename>halt.target</filename>,
  67                 <filename>kbrequest.target</filename>,
  68                 <filename>kexec.target</filename>,
  69                 <filename>local-fs.target</filename>,
  70                 <filename>local-fs-pre.target</filename>,
  71                 <filename>mail-transfer-agent.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>poweroff.target</filename>,
  77                 <filename>printer.target</filename>,
  78                 <filename>reboot.target</filename>,
  79                 <filename>remote-fs.target</filename>,
  80                 <filename>remote-fs-pre.target</filename>,
  81                 <filename>rescue.target</filename>,
  82                 <filename>rpcbind.target</filename>,
  83                 <filename>runlevel2.target</filename>,
  84                 <filename>runlevel3.target</filename>,
  85                 <filename>runlevel4.target</filename>,
  86                 <filename>runlevel5.target</filename>,
  87                 <filename>shutdown.target</filename>,
  88                 <filename>sigpwr.target</filename>,
  89                 <filename>sleep.target</filename>,
  90                 <filename>smartcard.target</filename>,
  91                 <filename>sockets.target</filename>,
  92                 <filename>sound.target</filename>,
  93                 <filename>suspend.target</filename>,
  94                 <filename>swap.target</filename>,
  95                 <filename>sysinit.target</filename>,
  96                 <filename>syslog.service</filename>,
  97                 <filename>syslog.socket</filename>,
  98                 <filename>syslog.target</filename>,
  99                 <filename>time-sync.target</filename>,
 100                 <filename>umount.target</filename></para>
 101         </refsynopsisdiv>
 102
 103         <refsect1>
 104                 <title>Description</title>
 105
 106                 <para>A few units are treated specially by
 107                 systemd. They have special internal semantics and
 108                 cannot be renamed.</para>
 109         </refsect1>
 110
 111         <refsect1>
 112                 <title>Special System Units</title>
 113
 114                 <variablelist>
 115                         <varlistentry>
 116                                 <term><filename>basic.target</filename></term>
 117                                 <listitem>
 118                                         <para>A special target unit
 119                                         covering early boot-up.</para>
 120                                         <para>systemd automatically
 121                                         adds dependencies of the types
 122                                         Requires and After for this
 123                                         target unit to all SysV
 124                                         service units configured for
 125                                         runlevel 1 to 5.</para>
 126                                         <para>Usually this should pull-in
 127                                         all sockets, mount points,
 128                                         swap devices and other basic
 129                                         initialization necessary for
 130                                         the general purpose
 131                                         daemons. Most normal daemons
 132                                         should have dependencies of
 133                                         type After and Requires on
 134                                         this unit.</para>
 135                                 </listitem>
 136                         </varlistentry>
 137                         <varlistentry>
 138                                 <term><filename>bluetooth.target</filename></term>
 139                                 <listitem>
 140                                         <para>This target is started
 141                                         automatically as soon as a
 142                                         bluetooth controller is
 143                                         plugged in or becomes
 144                                         available at boot.</para>
 145                                 </listitem>
 146                         </varlistentry>
 147                         <varlistentry>
 148                                 <term><filename>ctrl-alt-del.target</filename></term>
 149                                 <listitem>
 150                                         <para>systemd starts this
 151                                         target whenever
 152                                         Control+Alt+Del is pressed on
 153                                         the console. Usually this
 154                                         should be aliased (symlinked)
 155                                         to
 156                                         <filename>reboot.target</filename>.</para>
 157                                 </listitem>
 158                         </varlistentry>
 159                         <varlistentry>
 160                                 <term><filename>cryptsetup.target</filename></term>
 161                                 <listitem>
 162                                         <para>A target that pulls in
 163                                         setup services for all
 164                                         encrypted block
 165                                         devices.</para>
 166                                 </listitem>
 167                         </varlistentry>
 168                         <varlistentry>
 169                                 <term><filename>dbus.service</filename></term>
 170                                 <listitem>
 171                                         <para>A special unit for the
 172                                         D-Bus system bus. As soon as
 173                                         this service is fully started
 174                                         up systemd will connect to it
 175                                         and register its
 176                                         service.</para>
 177                                 </listitem>
 178                         </varlistentry>
 179                         <varlistentry>
 180                                 <term><filename>dbus.socket</filename></term>
 181                                 <listitem>
 182                                         <para>A special unit for the
 183                                         D-Bus system bus socket. All
 184                                         units with
 185                                         <literal>Type=dbus</literal>
 186                                         automatically gain a
 187                                         dependency on this
 188                                         unit.</para>
 189                                 </listitem>
 190                         </varlistentry>
 191                         <varlistentry>
 192                                 <term><filename>default.target</filename></term>
 193                                 <listitem>
 194                                         <para>The default unit systemd
 195                                         starts at bootup. Usually this
 196                                         should be aliased (symlinked)
 197                                         to
 198                                         <filename>multi-user.target</filename>
 199                                         or
 200                                         <filename>graphical.target</filename>.</para>
 201                                         <para>The default unit systemd
 202                                         starts at bootup can be
 203                                         overridden with the
 204                                         <varname>systemd.unit=</varname>
 205                                         kernel command line option.</para>
 206                                 </listitem>
 207                         </varlistentry>
 208                         <varlistentry>
 209                                 <term><filename>display-manager.service</filename></term>
 210                                 <listitem>
 211                                         <para>The display manager
 212                                         service. Usually this should
 213                                         be aliased (symlinked) to
 214                                         <filename>gdm.service</filename>
 215                                         or a similar display manager
 216                                         service.</para>
 217                                         <para>systemd automatically
 218                                         adds dependencies of type
 219                                         After for this target unit to
 220                                         all SysV init script service
 221                                         units with a LSB header
 222                                         referring to the
 223                                         <literal>$x-display-manager</literal>
 224                                         facility, for compatibility
 225                                         with Debian.</para>
 226                                 </listitem>
 227                         </varlistentry>
 228                         <varlistentry>
 229                                 <term><filename>emergency.target</filename></term>
 230                                 <listitem>
 231                                         <para>A special target unit
 232                                         that starts an emergency
 233                                         shell on the main
 234                                         console. This unit is supposed
 235                                         to be used with the kernel
 236                                         command line option
 237                                         <varname>systemd.unit=</varname>
 238                                         and has otherwise little use.
 239                                         </para>
 240                                 </listitem>
 241                         </varlistentry>
 242                         <varlistentry>
 243                                 <term><filename>final.target</filename></term>
 244                                 <listitem>
 245                                         <para>A special target unit
 246                                         that is used during the
 247                                         shutdown logic and may be used
 248                                         to pull in late services after
 249                                         all normal services are
 250                                         already terminated and all
 251                                         mounts unmounted.
 252                                         </para>
 253                                 </listitem>
 254                         </varlistentry>
 255                         <varlistentry>
 256                                 <term><filename>getty.target</filename></term>
 257                                 <listitem>
 258                                         <para>A special target unit
 259                                         that pulls in all local TTY
 260                                         <filename>getty</filename> instances.
 261                                         </para>
 262                                 </listitem>
 263                         </varlistentry>
 264                         <varlistentry>
 265                                 <term><filename>graphical.target</filename></term>
 266                                 <listitem>
 267                                         <para>A special target unit
 268                                         for setting up a graphical
 269                                         login screen. This pulls in
 270                                         <filename>multi-user.target</filename>.</para>
 271
 272                                         <para>Units that are needed
 273                                         for graphical login shall add
 274                                         Wants dependencies for their
 275                                         unit to this unit (or
 276                                         <filename>multi-user.target</filename>)
 277                                         during installation.</para>
 278                                 </listitem>
 279                         </varlistentry>
 280                         <varlistentry>
 281                                 <term><filename>hibernate.target</filename></term>
 282                                 <listitem>
 283                                         <para>A special target unit
 284                                         for hibernating the
 285                                         system. This pulls in
 286                                         <filename>sleep.target</filename>.</para>
 287                                 </listitem>
 288                         </varlistentry>
 289                         <varlistentry>
 290                                 <term><filename>http-daemon.target</filename></term>
 291                                 <listitem>
 292                                         <para>A target for pulling in
 293                                         an HTTP server if there is
 294                                         any.</para>
 295                                         <para>systemd automatically
 296                                         adds dependencies of type
 297                                         After for this target unit to
 298                                         all SysV init script service
 299                                         units with a LSB header
 300                                         referring to the
 301                                         <literal>$httpd</literal>
 302                                         facility.</para>
 303                                 </listitem>
 304                         </varlistentry>
 305                         <varlistentry>
 306                                 <term><filename>halt.target</filename></term>
 307                                 <listitem>
 308                                         <para>A special target unit
 309                                         for shutting down and halting the system.</para>
 310
 311                                         <para>Applications wanting to
 312                                         halt the system should start
 313                                         this unit.</para>
 314                                 </listitem>
 315                         </varlistentry>
 316                         <varlistentry>
 317                                 <term><filename>kbrequest.target</filename></term>
 318                                 <listitem>
 319                                         <para>systemd starts this
 320                                         target whenever Alt+ArrowUp is
 321                                         pressed on the console. This
 322                                         is a good candidate to be
 323                                         aliased (symlinked) to
 324                                         <filename>rescue.target</filename>.</para>
 325                                 </listitem>
 326                         </varlistentry>
 327                         <varlistentry>
 328                                 <term><filename>kexec.target</filename></term>
 329                                 <listitem>
 330                                         <para>A special target unit
 331                                         for shutting down and rebooting the system via kexec.</para>
 332
 333                                         <para>Applications wanting to
 334                                         reboot the system with kexec should start
 335                                         this unit.</para>
 336                                 </listitem>
 337                         </varlistentry>
 338                         <varlistentry>
 339                                 <term><filename>local-fs.target</filename></term>
 340                                 <listitem>
 341                                         <para>systemd automatically
 342                                         adds dependencies of type
 343                                         After to all mount units that
 344                                         refer to local mount points
 345                                         for this target unit. In
 346                                         addition, systemd adds
 347                                         dependencies of type Wants to
 348                                         this target unit for those
 349                                         mounts listed in
 350                                         <filename>/etc/fstab</filename>
 351                                         that have the
 352                                         <option>auto</option> and
 353                                         <option>comment=systemd.mount</option>
 354                                         mount options set.</para>
 355
 356                                         <para>systemd automatically
 357                                         adds dependencies of type
 358                                         After for this target unit to
 359                                         all SysV init script service
 360                                         units with an LSB header
 361                                         referring to the
 362                                         <literal>$local_fs</literal>
 363                                         facility.</para>
 364                                 </listitem>
 365                         </varlistentry>
 366                         <varlistentry>
 367                                 <term><filename>local-fs-pre.target</filename></term>
 368                                 <listitem>
 369                                         <para>This target unit is
 370                                         automatically ordered before
 371                                         all local mount points marked
 372                                         with <option>auto</option>
 373                                         (see above). It can be used to
 374                                         execute certain units before
 375                                         all local mounts.</para>
 376                                 </listitem>
 377                         </varlistentry>
 378                         <varlistentry>
 379                                 <term><filename>mail-transfer-agent.target</filename></term>
 380                                 <listitem>
 381                                         <para>The mail transfer agent
 382                                         (MTA) service. Usually this
 383                                         should pull-in all units
 384                                         necessary for
 385                                         sending/receiving mails on the
 386                                         local host.</para>
 387
 388                                         <para>systemd automatically
 389                                         adds dependencies of type
 390                                         After for this target unit to
 391                                         all SysV init script service
 392                                         units with an LSB header
 393                                         referring to the
 394                                         <literal>$mail-transfer-agent</literal>
 395                                         or
 396                                         <literal>$mail-transport-agent</literal>
 397                                         facilities, for compatibility
 398                                         with Debian.</para>
 399                                 </listitem>
 400                         </varlistentry>
 401                         <varlistentry>
 402                                 <term><filename>multi-user.target</filename></term>
 403                                 <listitem>
 404                                         <para>A special target unit
 405                                         for setting up a multi-user
 406                                         system (non-graphical). This
 407                                         is pulled in by
 408                                         <filename>graphical.target</filename>.</para>
 409
 410                                         <para>Units that are needed
 411                                         for a multi-user system shall
 412                                         add Wants dependencies to
 413                                         this unit for their unit during
 414                                         installation.</para>
 415                                 </listitem>
 416                         </varlistentry>
 417                         <varlistentry>
 418                                 <term><filename>network.target</filename></term>
 419                                 <listitem>
 420                                         <para>systemd automatically
 421                                         adds dependencies of type
 422                                         After for this target unit to
 423                                         all SysV init script service
 424                                         units with an LSB header
 425                                         referring to the
 426                                         <literal>$network</literal>
 427                                         facility.</para>
 428                                 </listitem>
 429                         </varlistentry>
 430                         <varlistentry>
 431                                 <term><filename>nss-lookup.target</filename></term>
 432                                 <listitem>
 433                                         <para>A target that should be
 434                                         used as synchronization point
 435                                         for all host/network name
 436                                         service lookups. Note that
 437                                         this is independent of
 438                                         user/group name lookups for
 439                                         which
 440                                         <filename>nss-user-lookup.target</filename>
 441                                         should be used. systemd
 442                                         automatically adds
 443                                         dependencies of type After for
 444                                         this target unit to all SysV
 445                                         init script service units with
 446                                         an LSB header referring to the
 447                                         <literal>$named</literal>
 448                                         facility.</para>
 449                                 </listitem>
 450                         </varlistentry>
 451                         <varlistentry>
 452                                 <term><filename>nss-user-lookup.target</filename></term>
 453                                 <listitem>
 454                                         <para>A target that should be
 455                                         used as synchronization point
 456                                         for all user/group name
 457                                         service lookups. Note that
 458                                         this is independent of
 459                                         host/network name lookups for
 460                                         which
 461                                         <filename>nss-lookup.target</filename>
 462                                         should be used. </para>
 463                                 </listitem>
 464                         </varlistentry>
 465                         <varlistentry>
 466                                 <term><filename>poweroff.target</filename></term>
 467                                 <listitem>
 468                                         <para>A special target unit
 469                                         for shutting down and powering off the system.</para>
 470
 471                                         <para>Applications wanting to
 472                                         power off the system should start
 473                                         this unit.</para>
 474
 475                                         <para><filename>runlevel0.target</filename>
 476                                         is an alias for this target
 477                                         unit, for compatibility with SysV.</para>
 478                                 </listitem>
 479                         </varlistentry>
 480                         <varlistentry>
 481                                 <term><filename>printer.target</filename></term>
 482                                 <listitem>
 483                                         <para>This target is started
 484                                         automatically as soon as a
 485                                         printer is plugged in or
 486                                         becomes available at
 487                                         boot.</para>
 488                                 </listitem>
 489                         </varlistentry>
 490                         <varlistentry>
 491                                 <term><filename>reboot.target</filename></term>
 492                                 <listitem>
 493                                         <para>A special target unit
 494                                         for shutting down and rebooting the system.</para>
 495
 496                                         <para>Applications wanting to
 497                                         reboot the system should start
 498                                         this unit.</para>
 499
 500                                         <para><filename>runlevel6.target</filename>
 501                                         is an alias for this target
 502                                         unit, for compatibility with SysV.</para>
 503                                 </listitem>
 504                         </varlistentry>
 505                         <varlistentry>
 506                                 <term><filename>remote-fs.target</filename></term>
 507                                 <listitem>
 508                                         <para>Similar to
 509                                         <filename>local-fs.target</filename>,
 510                                         but for remote mount
 511                                         points.</para>
 512
 513                                         <para>systemd automatically
 514                                         adds dependencies of type
 515                                         After for this target unit to
 516                                         all SysV init script service
 517                                         units with an LSB header
 518                                         referring to the
 519                                         <literal>$remote_fs</literal>
 520                                         facility.</para>
 521                                 </listitem>
 522                         </varlistentry>
 523                         <varlistentry>
 524                                 <term><filename>remote-fs-pre.target</filename></term>
 525                                 <listitem>
 526                                         <para>This target unit is
 527                                         automatically ordered before
 528                                         all remote mount points marked
 529                                         with <option>auto</option>
 530                                         (see above). It can be used to
 531                                         execute certain units before
 532                                         all remote mounts.</para>
 533                                 </listitem>
 534                         </varlistentry>
 535                         <varlistentry>
 536                                 <term><filename>rescue.target</filename></term>
 537                                 <listitem>
 538                                         <para>A special target unit
 539                                         for setting up the base system
 540                                         and a rescue shell.</para>
 541
 542                                         <para><filename>runlevel1.target</filename>
 543                                         is an alias for this target
 544                                         unit, for compatibility with SysV.</para>
 545                                 </listitem>
 546                         </varlistentry>
 547                         <varlistentry>
 548                                 <term><filename>rpcbind.target</filename></term>
 549                                 <listitem>
 550                                         <para>systemd automatically
 551                                         adds dependencies of type
 552                                         After for this target unit to
 553                                         all SysV init script service
 554                                         units with an LSB header
 555                                         referring to the
 556                                         <literal>$rpcbind</literal>
 557                                         facility.</para>
 558                                 </listitem>
 559                         </varlistentry>
 560                         <varlistentry>
 561                                 <term><filename>runlevel2.target</filename></term>
 562                                 <listitem>
 563                                         <para>This is a target that is
 564                                         called whenever the SysV
 565                                         compatibility code asks for
 566                                         runlevel 2. It is a good idea
 567                                         to make this an alias for
 568                                         (i.e. symlink to)
 569                                         <filename>multi-user.target</filename>.</para>
 570                                 </listitem>
 571                         </varlistentry>
 572                         <varlistentry>
 573                                 <term><filename>runlevel3.target</filename></term>
 574                                 <listitem>
 575                                         <para>This is a target that is
 576                                         called whenever the SysV
 577                                         compatibility code asks for
 578                                         runlevel 3. It is a good idea
 579                                         to make this an alias for
 580                                         (i.e. symlink to)
 581                                         <filename>multi-user.target</filename>
 582                                         or
 583                                         <filename>graphical.target</filename>.</para>
 584                                 </listitem>
 585                         </varlistentry>
 586                         <varlistentry>
 587                                 <term><filename>runlevel4.target</filename></term>
 588                                 <listitem>
 589                                         <para>This is a target that is
 590                                         called whenever the SysV
 591                                         compatibility code asks for
 592                                         runlevel 4. It is a good idea
 593                                         to make this an alias for
 594                                         (i.e. symlink to)
 595                                         <filename>multi-user.target</filename>
 596                                         or
 597                                         <filename>graphical.target</filename>.</para>
 598                                 </listitem>
 599                         </varlistentry>
 600                         <varlistentry>
 601                                 <term><filename>runlevel5.target</filename></term>
 602                                 <listitem>
 603                                         <para>This is a target that is
 604                                         called whenever the SysV
 605                                         compatibility code asks for
 606                                         runlevel 5. It is a good idea
 607                                         to make this an alias for
 608                                         (i.e. symlink to)
 609                                         <filename>multi-user.target</filename>
 610                                         or
 611                                         <filename>graphical.target</filename>.</para>
 612                                 </listitem>
 613                         </varlistentry>
 614                         <varlistentry>
 615                                 <term><filename>shutdown.target</filename></term>
 616                                 <listitem>
 617                                         <para>A special target unit
 618                                         that terminates the services
 619                                         on system shutdown.</para>
 620
 621                                         <para>Services that shall be
 622                                         terminated on system shutdown
 623                                         shall add Conflicts
 624                                         dependencies to this unit for
 625                                         their service unit, which is
 626                                         implicitly done when
 627                                         <varname>DefaultDependencies=yes</varname>
 628                                         is set (the default).</para>
 629
 630                                         <para>systemd automatically
 631                                         adds dependencies of type
 632                                         Conflicts to this target unit
 633                                         for all SysV init script
 634                                         service units that shall be
 635                                         terminated in SysV runlevels 0
 636                                         or 6.</para>
 637                                 </listitem>
 638                         </varlistentry>
 639                         <varlistentry>
 640                                 <term><filename>sigpwr.target</filename></term>
 641                                 <listitem>
 642                                         <para>A special target that is
 643                                         started when systemd receives
 644                                         the SIGPWR process signal,
 645                                         which is normally sent by the
 646                                         kernel or UPS daemons when
 647                                         power fails.</para>
 648                                 </listitem>
 649                         </varlistentry>
 650                         <varlistentry>
 651                                 <term><filename>sleep.target</filename></term>
 652                                 <listitem>
 653                                         <para>A special target unit
 654                                         that is pulled in by
 655                                         <filename>suspend.target</filename>
 656                                         and
 657                                         <filename>hibernate.target</filename>
 658                                         and may be used to hook units
 659                                         into the sleep state
 660                                         logic.</para>
 661                                 </listitem>
 662                         </varlistentry>
 663                         <varlistentry>
 664                                 <term><filename>smartcard.target</filename></term>
 665                                 <listitem>
 666                                         <para>This target is started
 667                                         automatically as soon as a
 668                                         smartcard controller is
 669                                         plugged in or becomes
 670                                         available at boot.</para>
 671                                 </listitem>
 672                         </varlistentry>
 673                         <varlistentry>
 674                                 <term><filename>sockets.target</filename></term>
 675                                 <listitem>
 676                                         <para>A special target unit
 677                                         that sets up all service
 678                                         sockets.</para>
 679
 680                                         <para>Services that can be
 681                                         socket-activated shall add
 682                                         Wants dependencies to this
 683                                         unit for their socket unit
 684                                         during installation.</para>
 685                                 </listitem>
 686                         </varlistentry>
 687                         <varlistentry>
 688                                 <term><filename>sound.target</filename></term>
 689                                 <listitem>
 690                                         <para>This target is started
 691                                         automatically as soon as a
 692                                         sound card is plugged in or
 693                                         becomes available at
 694                                         boot.</para>
 695                                 </listitem>
 696                         </varlistentry>
 697                         <varlistentry>
 698                                 <term><filename>suspend.target</filename></term>
 699                                 <listitem>
 700                                         <para>A special target unit
 701                                         for suspending the
 702                                         system. This pulls in
 703                                         <filename>sleep.target</filename>.</para>
 704                                 </listitem>
 705                         </varlistentry>
 706                         <varlistentry>
 707                                 <term><filename>swap.target</filename></term>
 708                                 <listitem>
 709                                         <para>Similar to
 710                                         <filename>local-fs.target</filename>, but for swap
 711                                         partitions and swap
 712                                         files.</para>
 713                                 </listitem>
 714                         </varlistentry>
 715                         <varlistentry>
 716                                 <term><filename>sysinit.target</filename></term>
 717                                 <listitem>
 718                                         <para>A special target unit
 719                                         covering early boot-up scripts.</para>
 720                                         <para>systemd automatically
 721                                         adds dependencies of the types
 722                                         Wants and After for all
 723                                         SysV service units configured
 724                                         for runlevels that are not 0
 725                                         to 6 to this target unit.
 726                                         This covers the special
 727                                         boot-up runlevels some
 728                                         distributions have, such as S
 729                                         or b.</para>
 730                                 </listitem>
 731                         </varlistentry>
 732                         <varlistentry>
 733                                 <term><filename>syslog.service</filename></term>
 734                                 <listitem>
 735                                         <para>The syslog service if
 736                                         any. Implementations should
 737                                         create a symlink from the
 738                                         actual syslog implementation
 739                                         to this generic name for
 740                                         activating it.</para>
 741                                 </listitem>
 742                         </varlistentry>
 743                         <varlistentry>
 744                                 <term><filename>syslog.socket</filename></term>
 745                                 <listitem>
 746                                         <para>The socket unit where
 747                                         syslog implementations should
 748                                         listen on. All userspace log
 749                                         messages will be made
 750                                         available on this
 751                                         socket.</para>
 752                                 </listitem>
 753                         </varlistentry>
 754                         <varlistentry>
 755                                 <term><filename>syslog.target</filename></term>
 756                                 <listitem>
 757                                         <para>systemd automatically
 758                                         adds dependencies of type
 759                                         After for this target unit to
 760                                         all SysV init script service
 761                                         units with an LSB header
 762                                         referring to the
 763                                         <literal>$syslog</literal>
 764                                         facility.</para>
 765                                 </listitem>
 766                         </varlistentry>
 767                         <varlistentry>
 768                                 <term><filename>time-sync.target</filename></term>
 769                                 <listitem>
 770                                         <para>systemd automatically
 771                                         adds dependencies of type
 772                                         After for this target unit to
 773                                         all SysV init script service
 774                                         units with an LSB header
 775                                         referring to the
 776                                         <literal>$time</literal>
 777                                         facility.</para>
 778                                 </listitem>
 779                         </varlistentry>
 780                         <varlistentry>
 781                                 <term><filename>umount.target</filename></term>
 782                                 <listitem>
 783                                         <para>A special target unit
 784                                         that umounts all mount and
 785                                         automount points on system
 786                                         shutdown.</para>
 787
 788                                         <para>Mounts that shall be
 789                                         unmounted on system shutdown
 790                                         shall add Conflicts
 791                                         dependencies to this unit for
 792                                         their mount unit, which is
 793                                         implicitly done when
 794                                         <varname>DefaultDependencies=yes</varname>
 795                                         is set (the default).</para>
 796                                 </listitem>
 797                         </varlistentry>
 798                 </variablelist>
 799         </refsect1>
 800
 801         <refsect1>
 802                 <title>Special User Units</title>
 803
 804                 <para>When systemd runs as a user instance, the
 805                 following special units are available, which have
 806                 similar definitions as their system counterparts:
 807                 <filename>default.target</filename>,
 808                 <filename>shutdown.target</filename>,
 809                 <filename>sockets.target</filename></para>
 810
 811                 <para>In addition the following special unit is
 812                 understood only when systemd runs as service instance:</para>
 813
 814                 <variablelist>
 815                         <varlistentry>
 816                                 <term><filename>exit.service</filename></term>
 817                                 <listitem>
 818                                         <para>A special service unit
 819                                         for shutting down the
 820                                         user service manager.</para>
 821
 822                                         <para>Applications wanting to
 823                                         terminate the user service
 824                                         manager should start this
 825                                         unit. If systemd receives
 826                                         SIGTERM or SIGINT when running
 827                                         as user service daemon it will
 828                                         start this unit.</para>
 829
 830                                         <para>Normally, this pulls in
 831                                         <filename>shutdown.target</filename>
 832                                         which in turn should be
 833                                         conflicted by all units that
 834                                         want to be shut down on
 835                                         user service manager exit.</para>
 836                                 </listitem>
 837                         </varlistentry>
 838                 </variablelist>
 839         </refsect1>
 840
 841         <refsect1>
 842                   <title>See Also</title>
 843                   <para>
 844                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 845                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 846                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 847                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 848                           <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 849                           <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 850                   </para>
 851         </refsect1>
 852
 853 </refentry>