man/systemd.special.xml.in

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU General Public License as published by
  12   the Free Software Foundation; either version 2 of the License, or
  13   (at your option) any later version.
  14
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  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   General Public License for more details.
  19
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  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="systemd.special">
  25
  26         <refentryinfo>
  27                 <title>systemd.special</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.special</refentrytitle>
  42                 <manvolnum>7</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.special</refname>
  47                 <refpurpose>special systemd units</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename>basic.target</filename>,
  52                 <filename>ctrl-alt-del.target</filename>,
  53                 <filename>default.target</filename>,
  54                 <filename>emergency.service</filename>,
  55                 <filename>graphical.target</filename>,
  56                 <filename>halt.target</filename>,
  57                 <filename>kbrequest.target</filename>,
  58                 <filename>local-fs.target</filename>,
  59                 <filename>multi-user.target</filename>,
  60                 <filename>network.target</filename>,
  61                 <filename>nss-lookup.target</filename>,
  62                 <filename>poweroff.target</filename>,
  63                 <filename>reboot.target</filename>,
  64                 <filename>remote-fs.target</filename>,
  65                 <filename>rescue.target</filename>,
  66                 <filename>rpcbind.target</filename>,
  67                 <filename>rtc-set.target</filename>,
  68                 <filename>runlevel0.target</filename>,
  69                 <filename>runlevel1.target</filename>,
  70                 <filename>runlevel2.target</filename>,
  71                 <filename>runlevel3.target</filename>,
  72                 <filename>runlevel4.target</filename>,
  73                 <filename>runlevel5.target</filename>,
  74                 <filename>runlevel6.target</filename>
  75                 <filename>shutdown.target</filename>,
  76                 <filename>sigpwr.target</filename>,
  77                 <filename>sockets.target</filename>,
  78                 <filename>swap.target</filename>,
  79                 <filename>syslog.target</filename>,
  80                 <filename>systemd-initctl.service</filename>,
  81                 <filename>systemd-initctl.socket</filename>,
  82                 <filename>systemd-logger.service</filename>,
  83                 <filename>systemd-logger.socket</filename></para>
  84         </refsynopsisdiv>
  85
  86         <refsect1>
  87                 <title>Description</title>
  88
  89                 <para>A few units are treated specially by
  90                 systemd. They have special internal semantics and
  91                 cannot be renamed.</para>
  92         </refsect1>
  93
  94         <refsect1>
  95                 <title>Special System Units</title>
  96
  97                 <variablelist>
  98                         <varlistentry>
  99                                 <term><filename>basic.target</filename></term>
 100                                 <listitem>
 101                                         <para>A special target unit
 102                                         covering early boot-up.</para>
 103                                         <para>systemd automatically
 104                                         adds dependencies of the types
 105                                         Requires and After for this
 106                                         target unit to all SysV
 107                                         service units configured for
 108                                         runlevel 1 to 5.</para>
 109                                         <para>systemd automatically
 110                                         adds dependencies of the types
 111                                         Wants and After for all
 112                                         SysV service units configured
 113                                         for runlevels that are not 0
 114                                         to 6 to this target unit.
 115                                         This covers the special
 116                                         boot-up runlevels some
 117                                         distributions have, such as S
 118                                         or b.</para>
 119                                 </listitem>
 120                         </varlistentry>
 121                         <varlistentry>
 122                                 <term><filename>ctrl-alt-del.target</filename></term>
 123                                 <listitem>
 124                                         <para>systemd starts this
 125                                         target whenever
 126                                         Control+Alt+Del is pressed on
 127                                         the console. Usually this
 128                                         should be aliased (symlinked)
 129                                         to
 130                                         <filename>reboot.target</filename>.</para>
 131                                 </listitem>
 132                         </varlistentry>
 133                         <varlistentry>
 134                                 <term><filename>default.target</filename></term>
 135                                 <listitem>
 136                                         <para>The default unit systemd
 137                                         starts at bootup. Usually this
 138                                         should be aliased (symlinked)
 139                                         to
 140                                         <filename>multi-user.target</filename>
 141                                         or
 142                                         <filename>graphical.target</filename>.</para>
 143                                         <para>The default unit systemd
 144                                         starts at bootup can be
 145                                         overriden with the
 146                                         <varname>systemd.default=</varname>
 147                                         kernel command line option.</para>
 148                                 </listitem>
 149                         </varlistentry>
 150                         <varlistentry>
 151                                 <term><filename>emergency.service</filename></term>
 152                                 <listitem>
 153                                         <para>A special service unit
 154                                         that starts an emergency
 155                                         shell on the main
 156                                         console. This unit is supposed
 157                                         to be used with the kernel
 158                                         command line option
 159                                         <varname>systemd.default=</varname>
 160                                         and has otherwise little use.
 161                                         </para>
 162                                 </listitem>
 163                         </varlistentry>
 164                         <varlistentry>
 165                                 <term><filename>graphical.target</filename></term>
 166                                 <listitem>
 167                                         <para>A special target unit
 168                                         for setting up a graphical
 169                                         login screen. This pulls in
 170                                         <filename>multi-user.target</filename>.</para>
 171
 172                                         <para>Units that are needed
 173                                         for graphical login shall add
 174                                         Wants dependencies for their
 175                                         unit to this unit (or
 176                                         <filename>multi-user.target</filename>)
 177                                         during installation.</para>
 178                                 </listitem>
 179                         </varlistentry>
 180                         <varlistentry>
 181                                 <term><filename>halt.target</filename></term>
 182                                 <listitem>
 183                                         <para>A special target unit
 184                                         for shutting down and halting the system.</para>
 185
 186                                         <para>Applications wanting to
 187                                         halt the system should start
 188                                         this unit.</para>
 189                                 </listitem>
 190                         </varlistentry>
 191                         <varlistentry>
 192                                 <term><filename>kbrequest.target</filename></term>
 193                                 <listitem>
 194                                         <para>systemd starts this
 195                                         target whenever Alt+ArrowUp is
 196                                         pressed on the console. This
 197                                         is a good candidate to be
 198                                         aliased (symlinked) to
 199                                         <filename>rescue.target</filename>.</para>
 200                                 </listitem>
 201                         </varlistentry>
 202                         <varlistentry>
 203                                 <term><filename>local-fs.target</filename></term>
 204                                 <listitem>
 205                                         <para>systemd automatically
 206                                         adds dependencies of type
 207                                         After to all mount units that
 208                                         refer to local mount points
 209                                         for this target unit. In
 210                                         addition, systemd adds
 211                                         dependencies of type Wants to
 212                                         this target unit for those
 213                                         mounts listed in
 214                                         <filename>/etc/fstab</filename>
 215                                         that have the
 216                                         <literal>auto</literal> and
 217                                         <literal>comment=systemd.mount</literal>
 218                                         mount options set.</para>
 219
 220                                         <para>systemd automatically
 221                                         adds dependencies of type
 222                                         After for this target unit to
 223                                         all SysV init script service
 224                                         units with an LSB header
 225                                         referring to the
 226                                         <literal>$local_fs</literal>
 227                                         facility.</para>
 228                                 </listitem>
 229                         </varlistentry>
 230                         <varlistentry>
 231                                 <term><filename>multi-user.target</filename></term>
 232                                 <listitem>
 233                                         <para>A special target unit
 234                                         for setting up a multi-user
 235                                         system (non-graphical). This
 236                                         is pulled in by
 237                                         <filename>graphical.target</filename>.</para>
 238
 239                                         <para>Units that are needed
 240                                         for a multi-user system shall
 241                                         add Wants dependencies to
 242                                         this unit for their unit during
 243                                         installation.</para>
 244                                 </listitem>
 245                         </varlistentry>
 246                         <varlistentry>
 247                                 <term><filename>network.target</filename></term>
 248                                 <listitem>
 249                                         <para>systemd automatically
 250                                         adds dependencies of type
 251                                         After for this target unit to
 252                                         all SysV init script service
 253                                         units with an LSB header
 254                                         referring to the
 255                                         <literal>$network</literal>
 256                                         facility.</para>
 257                                 </listitem>
 258                         </varlistentry>
 259                         <varlistentry>
 260                                 <term><filename>nss-lookup.target</filename></term>
 261                                 <listitem>
 262                                         <para>systemd automatically
 263                                         adds dependencies of type
 264                                         After for this target unit to
 265                                         all SysV init script service
 266                                         units with an LSB header
 267                                         referring to the
 268                                         <literal>$named</literal>
 269                                         facility.</para>
 270                                 </listitem>
 271                         </varlistentry>
 272                         <varlistentry>
 273                                 <term><filename>poweroff.target</filename></term>
 274                                 <listitem>
 275                                         <para>A special target unit
 276                                         for shutting down and powering off the system.</para>
 277
 278                                         <para>Applications wanting to
 279                                         power off the system should start
 280                                         this unit.</para>
 281
 282                                         <para><filename>runlevel0.target</filename>
 283                                         is an alias for this target
 284                                         unit, for compatibility with SysV.</para>
 285                                 </listitem>
 286                         </varlistentry>
 287                         <varlistentry>
 288                                 <term><filename>reboot.target</filename></term>
 289                                 <listitem>
 290                                         <para>A special target unit
 291                                         for shutting down and rebooting the system.</para>
 292
 293                                         <para>Applications wanting to
 294                                         reboot the system should start
 295                                         this unit.</para>
 296
 297                                         <para><filename>runlevel6.target</filename>
 298                                         is an alias for this target
 299                                         unit, for compatibility with SysV.</para>
 300                                 </listitem>
 301                         </varlistentry>
 302                         <varlistentry>
 303                                 <term><filename>remote-fs.target</filename></term>
 304                                 <listitem>
 305                                         <para>Similar to
 306                                         <filename>local-fs.target</filename>,
 307                                         but for remote mount
 308                                         points.</para>
 309
 310                                         <para>systemd automatically
 311                                         adds dependencies of type
 312                                         After for this target unit to
 313                                         all SysV init script service
 314                                         units with an LSB header
 315                                         referring to the
 316                                         <literal>$remote-fs</literal>
 317                                         facility.</para>
 318                                 </listitem>
 319                         </varlistentry>
 320                         <varlistentry>
 321                                 <term><filename>rescue.target</filename></term>
 322                                 <listitem>
 323                                         <para>A special target unit
 324                                         for setting up the base system
 325                                         and a rescue shell.</para>
 326
 327                                         <para><filename>runlevel1.target</filename>
 328                                         is an alias for this target
 329                                         unit, for compatibility with SysV.</para>
 330                                 </listitem>
 331                         </varlistentry>
 332                         <varlistentry>
 333                                 <term><filename>rpcbind.target</filename></term>
 334                                 <listitem>
 335                                         <para>systemd automatically
 336                                         adds dependencies of type
 337                                         After for this target unit to
 338                                         all SysV init script service
 339                                         units with an LSB header
 340                                         referring to the
 341                                         <literal>$rpcbind</literal>
 342                                         facility.</para>
 343                                 </listitem>
 344                         </varlistentry>
 345                         <varlistentry>
 346                                 <term><filename>rtc-set.target</filename></term>
 347                                 <listitem>
 348                                         <para>systemd automatically
 349                                         adds dependencies of type
 350                                         After for this target unit to
 351                                         all SysV init script service
 352                                         units with an LSB header
 353                                         referring to the
 354                                         <literal>$time</literal>
 355                                         facility.</para>
 356                                 </listitem>
 357                         </varlistentry>
 358                         <varlistentry>
 359                                 <term><filename>runlevel0.target</filename></term>
 360                                 <listitem>
 361                                         <para>This is a target that is
 362                                         called whever the SysV
 363                                         compatibility code asks for
 364                                         runlevel 0. This is an alias
 365                                         for
 366                                         <filename>poweroff.target</filename>,
 367                                         for compatibility with
 368                                         SysV.</para>
 369                                 </listitem>
 370                         </varlistentry>
 371                         <varlistentry>
 372                                 <term><filename>runlevel1.target</filename></term>
 373                                 <listitem>
 374                                         <para>This is a target that is
 375                                         called whever the SysV
 376                                         compatibility code asks for
 377                                         runlevel 1. This is an alias
 378                                         for
 379                                         <filename>rescue.target</filename>,
 380                                         for compatibility with
 381                                         SysV.</para>
 382                                 </listitem>
 383                         </varlistentry>
 384                         <varlistentry>
 385                                 <term><filename>runlevel2.target</filename></term>
 386                                 <listitem>
 387                                         <para>This is a target that is
 388                                         called whever the SysV
 389                                         compatibility code asks for
 390                                         runlevel 2. It is a good idea
 391                                         to make this an alias for
 392                                         (i.e. symlink to)
 393                                         <filename>multi-user.target</filename>.</para>
 394                                 </listitem>
 395                         </varlistentry>
 396                         <varlistentry>
 397                                 <term><filename>runlevel3.target</filename></term>
 398                                 <listitem>
 399                                         <para>This is a target that is
 400                                         called whever the SysV
 401                                         compatibility code asks for
 402                                         runlevel 3. It is a good idea
 403                                         to make this an alias for
 404                                         (i.e. symlink to)
 405                                         <filename>multi-user.target</filename>
 406                                         or
 407                                         <filename>graphical.target</filename>.</para>
 408                                 </listitem>
 409                         </varlistentry>
 410                         <varlistentry>
 411                                 <term><filename>runlevel4.target</filename></term>
 412                                 <listitem>
 413                                         <para>This is a target that is
 414                                         called whever the SysV
 415                                         compatibility code asks for
 416                                         runlevel 4. It is a good idea
 417                                         to make this an alias for
 418                                         (i.e. symlink to)
 419                                         <filename>multi-user.target</filename>
 420                                         or
 421                                         <filename>graphical.target</filename>.</para>
 422                                 </listitem>
 423                         </varlistentry>
 424                         <varlistentry>
 425                                 <term><filename>runlevel5.target</filename></term>
 426                                 <listitem>
 427                                         <para>This is a target that is
 428                                         called whever the SysV
 429                                         compatibility code asks for
 430                                         runlevel 5. It is a good idea
 431                                         to make this an alias for
 432                                         (i.e. symlink to)
 433                                         <filename>multi-user.target</filename>
 434                                         or
 435                                         <filename>graphical.target</filename>.</para>
 436                                 </listitem>
 437                         </varlistentry>
 438                         <varlistentry>
 439                                 <term><filename>runlevel6.target</filename></term>
 440                                 <listitem>
 441                                         <para>This is a target that is
 442                                         called whever the SysV
 443                                         compatibility code asks for
 444                                         runlevel 6. This is an alias
 445                                         for
 446                                         <filename>reboot.target</filename>,
 447                                         for compatibility with
 448                                         SysV.</para>
 449                                 </listitem>
 450                         </varlistentry>
 451                         <varlistentry>
 452                                 <term><filename>shutdown.target</filename></term>
 453                                 <listitem>
 454                                         <para>A special target unit
 455                                         that terminates the services
 456                                         on system shutdown.</para>
 457
 458                                         <para>Services that shall be
 459                                         terminated on system shutdown
 460                                         shall add Conflicts
 461                                         dependencies to this unit for
 462                                         their service unit during
 463                                         installation.</para>
 464
 465                                         <para>systemd automatically
 466                                         adds dependencies of type
 467                                         Conflicts to this target unit
 468                                         for all SysV init script
 469                                         service units that shall be
 470                                         terminated in SysV runlevels 0
 471                                         or 6.</para>
 472                                 </listitem>
 473                         </varlistentry>
 474                         <varlistentry>
 475                                 <term><filename>sigpwr.target</filename></term>
 476                                 <listitem>
 477                                         <para>A special target that is
 478                                         started when systemd receives
 479                                         the SIGPWR process signal,
 480                                         which is normally sent by the
 481                                         kernel or UPS daemons when
 482                                         power fails.</para>
 483                                 </listitem>
 484                         </varlistentry>
 485                         <varlistentry>
 486                                 <term><filename>sockets.target</filename></term>
 487                                 <listitem>
 488                                         <para>A special target unit
 489                                         that sets up all service
 490                                         sockets.</para>
 491
 492                                         <para>Services that can be
 493                                         socket-activated shall add
 494                                         Wants dependencies to this
 495                                         unit for their socket unit
 496                                         during installation.</para>
 497                                 </listitem>
 498                         </varlistentry>
 499                         <varlistentry>
 500                                 <term><filename>swap.target</filename></term>
 501                                 <listitem>
 502                                         <para>Similar to
 503                                         <filename>local-fs.target</filename>, but for swap
 504                                         partitions and swap
 505                                         files.</para>
 506                                 </listitem>
 507                         </varlistentry>
 508                         <varlistentry>
 509                                 <term><filename>syslog.target</filename></term>
 510                                 <listitem>
 511                                         <para>systemd automatically
 512                                         adds dependencies of type
 513                                         After for this target unit to
 514                                         all SysV init script service
 515                                         units with an LSB header
 516                                         referring to the
 517                                         <literal>$syslog</literal>
 518                                         facility.</para>
 519
 520                                         <para>Administrators should
 521                                         ensure that this target pulls
 522                                         in a service unit with the
 523                                         name or alias of
 524                                         <filename>@SPECIAL_SYSLOG_SERVICE@</filename>
 525                                         (or a socket unit that
 526                                         activates this
 527                                         service).</para>
 528                                 </listitem>
 529                         </varlistentry>
 530                         <varlistentry>
 531                                 <term><filename>systemd-initctl.service</filename></term>
 532                                 <listitem>
 533                                         <para>This provides
 534                                         compatibility with the SysV
 535                                         /dev/initctl file system FIFO
 536                                         for communication with the
 537                                         init system.</para>
 538                                         <para>This is a
 539                                         socket-activated service, see
 540                                         <filename>system-initctl.socket</filename>.</para>
 541                                 </listitem>
 542                         </varlistentry>
 543                         <varlistentry>
 544                                 <term><filename>systemd-initctl.socket</filename></term>
 545                                 <listitem>
 546                                         <para>Socket activation unit
 547                                         for
 548                                         <filename>system-initctl.service</filename>.</para>
 549                                 </listitem>
 550                         </varlistentry>
 551                         <varlistentry>
 552                                 <term><filename>systemd-logger.service</filename></term>
 553                                 <listitem>
 554                                         <para>This is internally used
 555                                         by systemd to provide syslog
 556                                         logging to the processes it
 557                                         maintains.</para>
 558                                         <para>This is a
 559                                         socket-activated service, see
 560                                         <filename>system-logger.socket</filename>.</para>
 561                                 </listitem>
 562                         </varlistentry>
 563                         <varlistentry>
 564                                 <term><filename>systemd-logger.socket</filename></term>
 565                                 <listitem>
 566                                         <para>Socket activation unit
 567                                         for
 568                                         <filename>system-logger.service</filename>. systemd
 569                                         will automatically add
 570                                         dependencies of types Requires
 571                                         and After to all units that
 572                                         have been configured for
 573                                         stdout or stderr to be
 574                                         connected to syslog or the
 575                                         kernel log buffer.</para>
 576                                 </listitem>
 577                         </varlistentry>
 578                 </variablelist>
 579         </refsect1>
 580
 581         <refsect1>
 582                 <title>Special Session Units</title>
 583
 584                 <para>When systemd runs as a service instance, the
 585                 following special units are available, which have
 586                 similar definitions as their system counterparts:
 587                 <filename>default.target</filename>,
 588                 <filename>local-fs.target</filename>,
 589                 <filename>remote-fs.target</filename>,
 590                 <filename>shutdown.target</filename>,
 591                 <filename>sockets.target</filename>,
 592                 <filename>swap.target</filename>.</para>
 593         </refsect1>
 594
 595         <refsect1>
 596                   <title>See Also</title>
 597                   <para>
 598                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 599                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 600                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 601                           <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 602                   </para>
 603         </refsect1>
 604
 605 </refentry>