man/systemd.special.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
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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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  18   General Public License for more details.
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  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
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  23
  24 <refentry id="systemd.special">
  25
  26         <refentryinfo>
  27                 <title>systemd.special</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.special</refentrytitle>
  42                 <manvolnum>7</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.special</refname>
  47                 <refpurpose>special systemd units</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename>basic.target</filename></para>
  52                 <para><filename>ctrl-alt-del.target</filename></para>
  53                 <para><filename>default.target</filename></para>
  54                 <para><filename>emergency.service</filename></para>
  55                 <para><filename>graphical.target</filename></para>
  56                 <para><filename>halt.target</filename></para>
  57                 <para><filename>kbrequest.target</filename></para>
  58                 <para><filename>local-fs.target</filename></para>
  59                 <para><filename>multi-user.target</filename></para>
  60                 <para><filename>network.target</filename></para>
  61                 <para><filename>nss-lookup.target</filename></para>
  62                 <para><filename>poweroff.target</filename></para>
  63                 <para><filename>reboot.target</filename></para>
  64                 <para><filename>remote-fs.target</filename></para>
  65                 <para><filename>rescue.target</filename></para>
  66                 <para><filename>rpcbind.target</filename></para>
  67                 <para><filename>rtc-set.target</filename></para>
  68                 <para><filename>runlevel0.target</filename>,
  69                         <filename>runlevel0.target</filename>,
  70                         <filename>runlevel1.target</filename>,
  71                         <filename>runlevel2.target</filename>,
  72                         <filename>runlevel3.target</filename>,
  73                         <filename>runlevel4.target</filename>,
  74                         <filename>runlevel5.target</filename>,
  75                         <filename>runlevel6.target</filename></para>
  76                 <para><filename>shutdown.target</filename></para>
  77                 <para><filename>sigpwr.target</filename></para>
  78                 <para><filename>sockets.target</filename></para>
  79                 <para><filename>swap.target</filename></para>
  80                 <para><filename>syslog.target</filename></para>
  81                 <para><filename>systemd-initctl.service</filename>, <filename>systemd-initctl.socket</filename></para>
  82                 <para><filename>systemd-logger.service</filename>, <filename>systemd-logger.socket</filename></para>
  83         </refsynopsisdiv>
  84
  85         <refsect1>
  86                 <title>Description</title>
  87
  88                 <para>A few units are treated specially by
  89                 systemd. They have special internal semantics and
  90                 cannot be renamed.</para>
  91         </refsect1>
  92
  93         <refsect1>
  94                 <title>Special System Units</title>
  95
  96                 <variablelist>
  97                         <varlistentry>
  98                                 <term><filename>basic.target</filename></term>
  99                                 <listitem>
 100                                         <para>A special target unit
 101                                         covering early boot-up.</para>
 102                                         <para>systemd automatically
 103                                         adds dependencies of the types
 104                                         Requires and After for this
 105                                         target unit to all SysV
 106                                         service units configured for
 107                                         runlevel 1 to 5.</para>
 108                                         <para>systemd automatically
 109                                         adds dependencies of the types
 110                                         Wants and After for all
 111                                         SysV service units configured
 112                                         for runlevels that are not 0
 113                                         to 6 to this target unit.
 114                                         This covers the special
 115                                         boot-up runlevels some
 116                                         distributions have, such as S
 117                                         or b.</para>
 118                                 </listitem>
 119                         </varlistentry>
 120                         <varlistentry>
 121                                 <term><filename>ctrl-alt-del.target</filename></term>
 122                                 <listitem>
 123                                         <para>systemd starts this
 124                                         target whenever
 125                                         Control+Alt+Del is pressed on
 126                                         the console. Usually this
 127                                         should be aliased (symlinked)
 128                                         to
 129                                         <filename>reboot.target</filename>.</para>
 130                                 </listitem>
 131                         </varlistentry>
 132                         <varlistentry>
 133                                 <term><filename>default.target</filename></term>
 134                                 <listitem>
 135                                         <para>The default unit systemd
 136                                         starts at bootup. Usually this
 137                                         should be aliased (symlinked)
 138                                         to
 139                                         <filename>multi-user.target</filename>
 140                                         or
 141                                         <filename>graphical.target</filename>.</para>
 142                                         <para>The default unit systemd
 143                                         starts at bootup can be
 144                                         overriden with the
 145                                         <varname>systemd.default=</varname>
 146                                         kernel command line option.</para>
 147                                 </listitem>
 148                         </varlistentry>
 149                         <varlistentry>
 150                                 <term><filename>emergency.service</filename></term>
 151                                 <listitem>
 152                                         <para>A special service unit
 153                                         that starts an emergency
 154                                         shell on the main
 155                                         console. This unit is supposed
 156                                         to be used with the kernel
 157                                         command line option
 158                                         <varname>systemd.default=</varname>
 159                                         and has otherwise little use.
 160                                         </para>
 161                                 </listitem>
 162                         </varlistentry>
 163                         <varlistentry>
 164                                 <term><filename>graphical.target</filename></term>
 165                                 <listitem>
 166                                         <para>A special target unit
 167                                         for setting up a graphical
 168                                         login screen. This pulls in
 169                                         <filename>multi-user.target</filename>.</para>
 170
 171                                         <para>Units that are needed
 172                                         for graphical login shall add
 173                                         Wants dependencies for their
 174                                         unit to this unit (or
 175                                         <filename>multi-user.target</filename>)
 176                                         during installation.</para>
 177                                 </listitem>
 178                         </varlistentry>
 179                         <varlistentry>
 180                                 <term><filename>halt.target</filename></term>
 181                                 <listitem>
 182                                         <para>A special target unit
 183                                         for shutting down and halting the system.</para>
 184
 185                                         <para>Applications wanting to
 186                                         halt the system should start
 187                                         this unit.</para>
 188                                 </listitem>
 189                         </varlistentry>
 190                         <varlistentry>
 191                                 <term><filename>kbrequest.target</filename></term>
 192                                 <listitem>
 193                                         <para>systemd starts this
 194                                         target whenever Alt+ArrowUp is
 195                                         pressed on the console. This
 196                                         is a good candidate to be
 197                                         aliased (symlinked) to
 198                                         <filename>rescue.target</filename>.</para>
 199                                 </listitem>
 200                         </varlistentry>
 201                         <varlistentry>
 202                                 <term><filename>local-fs.target</filename></term>
 203                                 <listitem>
 204                                         <para>systemd automatically
 205                                         adds dependencies of type
 206                                         After to all mount units that
 207                                         refer to local mount points
 208                                         for this target unit. In
 209                                         addition, systemd adds
 210                                         dependencies of type Wants to
 211                                         this target unit for those
 212                                         mounts listed in
 213                                         <filename>/etc/fstab</filename>
 214                                         that have the
 215                                         <literal>auto</literal> and
 216                                         <literal>comment=systemd.mount</literal>
 217                                         mount options set.</para>
 218
 219                                         <para>systemd automatically
 220                                         adds dependencies of type
 221                                         After for this target unit to
 222                                         all SysV init script service
 223                                         units with an LSB header
 224                                         referring to the
 225                                         <literal>$local_fs</literal>
 226                                         facility.</para>
 227                                 </listitem>
 228                         </varlistentry>
 229                         <varlistentry>
 230                                 <term><filename>multi-user.target</filename></term>
 231                                 <listitem>
 232                                         <para>A special target unit
 233                                         for setting up a multi-user
 234                                         system (non-graphical). This
 235                                         is pulled in by
 236                                         <filename>graphical.target</filename>.</para>
 237
 238                                         <para>Units that are needed
 239                                         for a multi-user system shall
 240                                         add Wants dependencies to
 241                                         this unit for their unit during
 242                                         installation.</para>
 243                                 </listitem>
 244                         </varlistentry>
 245                         <varlistentry>
 246                                 <term><filename>network.target</filename></term>
 247                                 <listitem>
 248                                         <para>systemd automatically
 249                                         adds dependencies of type
 250                                         After for this target unit to
 251                                         all SysV init script service
 252                                         units with an LSB header
 253                                         referring to the
 254                                         <literal>$network</literal>
 255                                         facility.</para>
 256                                 </listitem>
 257                         </varlistentry>
 258                         <varlistentry>
 259                                 <term><filename>nss-lookup.target</filename></term>
 260                                 <listitem>
 261                                         <para>systemd automatically
 262                                         adds dependencies of type
 263                                         After for this target unit to
 264                                         all SysV init script service
 265                                         units with an LSB header
 266                                         referring to the
 267                                         <literal>$named</literal>
 268                                         facility.</para>
 269                                 </listitem>
 270                         </varlistentry>
 271                         <varlistentry>
 272                                 <term><filename>poweroff.target</filename></term>
 273                                 <listitem>
 274                                         <para>A special target unit
 275                                         for shutting down and powering off the system.</para>
 276
 277                                         <para>Applications wanting to
 278                                         power off the system should start
 279                                         this unit.</para>
 280
 281                                         <para><filename>runlevel0.target</filename>
 282                                         is an alias for this target
 283                                         unit, for compatibility with SysV.</para>
 284                                 </listitem>
 285                         </varlistentry>
 286                         <varlistentry>
 287                                 <term><filename>reboot.target</filename></term>
 288                                 <listitem>
 289                                         <para>A special target unit
 290                                         for shutting down and rebooting the system.</para>
 291
 292                                         <para>Applications wanting to
 293                                         reboot the system should start
 294                                         this unit.</para>
 295
 296                                         <para><filename>runlevel6.target</filename>
 297                                         is an alias for this target
 298                                         unit, for compatibility with SysV.</para>
 299                                 </listitem>
 300                         </varlistentry>
 301                         <varlistentry>
 302                                 <term><filename>remote-fs.target</filename></term>
 303                                 <listitem>
 304                                         <para>Similar to
 305                                         <filename>local-fs.target</filename>,
 306                                         but for remote mount
 307                                         points.</para>
 308
 309                                         <para>systemd automatically
 310                                         adds dependencies of type
 311                                         After for this target unit to
 312                                         all SysV init script service
 313                                         units with an LSB header
 314                                         referring to the
 315                                         <literal>$remote-fs</literal>
 316                                         facility.</para>
 317                                 </listitem>
 318                         </varlistentry>
 319                         <varlistentry>
 320                                 <term><filename>rescue.target</filename></term>
 321                                 <listitem>
 322                                         <para>A special target unit
 323                                         for setting up the base system
 324                                         and a rescue shell.</para>
 325
 326                                         <para><filename>runlevel1.target</filename>
 327                                         is an alias for this target
 328                                         unit, for compatibility with SysV.</para>
 329                                 </listitem>
 330                         </varlistentry>
 331                         <varlistentry>
 332                                 <term><filename>rpcbind.target</filename></term>
 333                                 <listitem>
 334                                         <para>systemd automatically
 335                                         adds dependencies of type
 336                                         After for this target unit to
 337                                         all SysV init script service
 338                                         units with an LSB header
 339                                         referring to the
 340                                         <literal>$rpcbind</literal>
 341                                         facility.</para>
 342                                 </listitem>
 343                         </varlistentry>
 344                         <varlistentry>
 345                                 <term><filename>rtc-set.target</filename></term>
 346                                 <listitem>
 347                                         <para>systemd automatically
 348                                         adds dependencies of type
 349                                         After for this target unit to
 350                                         all SysV init script service
 351                                         units with an LSB header
 352                                         referring to the
 353                                         <literal>$time</literal>
 354                                         facility.</para>
 355                                 </listitem>
 356                         </varlistentry>
 357                         <varlistentry>
 358                                 <term><filename>runlevel0.target</filename></term>
 359                                 <listitem>
 360                                         <para>This is a target that is
 361                                         called whever the SysV
 362                                         compatibility code asks for
 363                                         runlevel 0. This is an alias
 364                                         for
 365                                         <filename>poweroff.target</filename>,
 366                                         for compatibility with
 367                                         SysV.</para>
 368                                 </listitem>
 369                         </varlistentry>
 370                         <varlistentry>
 371                                 <term><filename>runlevel1.target</filename></term>
 372                                 <listitem>
 373                                         <para>This is a target that is
 374                                         called whever the SysV
 375                                         compatibility code asks for
 376                                         runlevel 1. This is an alias
 377                                         for
 378                                         <filename>rescue.target</filename>,
 379                                         for compatibility with
 380                                         SysV.</para>
 381                                 </listitem>
 382                         </varlistentry>
 383                         <varlistentry>
 384                                 <term><filename>runlevel2.target</filename></term>
 385                                 <listitem>
 386                                         <para>This is a target that is
 387                                         called whever the SysV
 388                                         compatibility code asks for
 389                                         runlevel 2. It is a good idea
 390                                         to make this an alias for
 391                                         (i.e. symlink to)
 392                                         <filename>multi-user.target</filename>.</para>
 393                                 </listitem>
 394                         </varlistentry>
 395                         <varlistentry>
 396                                 <term><filename>runlevel3.target</filename></term>
 397                                 <listitem>
 398                                         <para>This is a target that is
 399                                         called whever the SysV
 400                                         compatibility code asks for
 401                                         runlevel 3. It is a good idea
 402                                         to make this an alias for
 403                                         (i.e. symlink to)
 404                                         <filename>multi-user.target</filename>
 405                                         or
 406                                         <filename>graphical.target</filename>.</para>
 407                                 </listitem>
 408                         </varlistentry>
 409                         <varlistentry>
 410                                 <term><filename>runlevel4.target</filename></term>
 411                                 <listitem>
 412                                         <para>This is a target that is
 413                                         called whever the SysV
 414                                         compatibility code asks for
 415                                         runlevel 4. It is a good idea
 416                                         to make this an alias for
 417                                         (i.e. symlink to)
 418                                         <filename>multi-user.target</filename>
 419                                         or
 420                                         <filename>graphical.target</filename>.</para>
 421                                 </listitem>
 422                         </varlistentry>
 423                         <varlistentry>
 424                                 <term><filename>runlevel5.target</filename></term>
 425                                 <listitem>
 426                                         <para>This is a target that is
 427                                         called whever the SysV
 428                                         compatibility code asks for
 429                                         runlevel 5. It is a good idea
 430                                         to make this an alias for
 431                                         (i.e. symlink to)
 432                                         <filename>multi-user.target</filename>
 433                                         or
 434                                         <filename>graphical.target</filename>.</para>
 435                                 </listitem>
 436                         </varlistentry>
 437                         <varlistentry>
 438                                 <term><filename>runlevel6.target</filename></term>
 439                                 <listitem>
 440                                         <para>This is a target that is
 441                                         called whever the SysV
 442                                         compatibility code asks for
 443                                         runlevel 6. This is an alias
 444                                         for
 445                                         <filename>reboot.target</filename>,
 446                                         for compatibility with
 447                                         SysV.</para>
 448                                 </listitem>
 449                         </varlistentry>
 450                         <varlistentry>
 451                                 <term><filename>shutdown.target</filename></term>
 452                                 <listitem>
 453                                         <para>A special target unit
 454                                         that terminates the services
 455                                         on system shutdown.</para>
 456
 457                                         <para>Services that shall be
 458                                         terminated on system shutdown
 459                                         shall add Conflicts
 460                                         dependencies to this unit for
 461                                         their service unit during
 462                                         installation.</para>
 463
 464                                         <para>systemd automatically
 465                                         adds dependencies of type
 466                                         Conflicts to this target unit
 467                                         for all SysV init script
 468                                         service units that shall be
 469                                         terminated in SysV runlevels 0
 470                                         or 6.</para>
 471                                 </listitem>
 472                         </varlistentry>
 473                         <varlistentry>
 474                                 <term><filename>sigpwr.target</filename></term>
 475                                 <listitem>
 476                                         <para>A special target that is
 477                                         started when systemd receives
 478                                         the SIGPWR process signal,
 479                                         which is normally sent by the
 480                                         kernel or UPS daemons when
 481                                         power fails.</para>
 482                                 </listitem>
 483                         </varlistentry>
 484                         <varlistentry>
 485                                 <term><filename>sockets.target</filename></term>
 486                                 <listitem>
 487                                         <para>A special target unit
 488                                         that sets up all service
 489                                         sockets.</para>
 490
 491                                         <para>Services that can be
 492                                         socket-activated shall add
 493                                         Wants dependencies to this
 494                                         unit for their socket unit
 495                                         during installation.</para>
 496                                 </listitem>
 497                         </varlistentry>
 498                         <varlistentry>
 499                                 <term><filename>swap.target</filename></term>
 500                                 <listitem>
 501                                         <para>Similar to
 502                                         <filename>local-fs.target</filename>, but for swap
 503                                         partitions and swap
 504                                         files.</para>
 505                                 </listitem>
 506                         </varlistentry>
 507                         <varlistentry>
 508                                 <term><filename>syslog.target</filename></term>
 509                                 <listitem>
 510                                         <para>systemd automatically
 511                                         adds dependencies of type
 512                                         After for this target unit to
 513                                         all SysV init script service
 514                                         units with an LSB header
 515                                         referring to the
 516                                         <literal>$syslog</literal>
 517                                         facility.</para>
 518
 519                                         <para>Administrators should
 520                                         ensure that this target pulls
 521                                         in a service unit with the
 522                                         name or alias of
 523                                         <filename>@SPECIAL_SYSLOG_SERVICE@</filename>
 524                                         (or a socket unit that
 525                                         activates this
 526                                         service).</para>
 527                                 </listitem>
 528                         </varlistentry>
 529                         <varlistentry>
 530                                 <term><filename>systemd-initctl.service</filename></term>
 531                                 <listitem>
 532                                         <para>This provides
 533                                         compatibility with the SysV
 534                                         /dev/initctl file system FIFO
 535                                         for communication with the
 536                                         init system.</para>
 537                                         <para>This is a
 538                                         socket-activated service, see
 539                                         <filename>system-initctl.socket</filename>.</para>
 540                                 </listitem>
 541                         </varlistentry>
 542                         <varlistentry>
 543                                 <term><filename>systemd-initctl.socket</filename></term>
 544                                 <listitem>
 545                                         <para>Socket activation unit
 546                                         for
 547                                         <filename>system-initctl.service</filename>.</para>
 548                                 </listitem>
 549                         </varlistentry>
 550                         <varlistentry>
 551                                 <term><filename>systemd-logger.service</filename></term>
 552                                 <listitem>
 553                                         <para>This is internally used
 554                                         by systemd to provide syslog
 555                                         logging to the processes it
 556                                         maintains.</para>
 557                                         <para>This is a
 558                                         socket-activated service, see
 559                                         <filename>system-logger.socket</filename>.</para>
 560                                 </listitem>
 561                         </varlistentry>
 562                         <varlistentry>
 563                                 <term><filename>systemd-logger.socket</filename></term>
 564                                 <listitem>
 565                                         <para>Socket activation unit
 566                                         for
 567                                         <filename>system-logger.service</filename>. systemd
 568                                         will automatically add
 569                                         dependencies of types Requires
 570                                         and After to all units that
 571                                         have been configured for
 572                                         stdout or stderr to be
 573                                         connected to syslog or the
 574                                         kernel log buffer.</para>
 575                                 </listitem>
 576                         </varlistentry>
 577                 </variablelist>
 578         </refsect1>
 579
 580         <refsect1>
 581                 <title>Special Session Units</title>
 582
 583                 <para>When systemd runs as a service instance, the
 584                 following special units are available, which have
 585                 similar definitions as their system counterparts:
 586                 <filename>default.target</filename>,
 587                 <filename>local-fs.target</filename>,
 588                 <filename>remote-fs.target</filename>,
 589                 <filename>shutdown.target</filename>,
 590                 <filename>sockets.target</filename>,
 591                 <filename>swap.target</filename>.</para>
 592         </refsect1>
 593
 594         <refsect1>
 595                   <title>See Also</title>
 596                   <para>
 597                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 598                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 599                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 600                           <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 601                   </para>
 602         </refsect1>
 603
 604 </refentry>