man/systemd.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU 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
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   General Public License for more details.
  19
  20   You should have received a copy of the GNU General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="systemd">
  25
  26         <refentryinfo>
  27                 <title>systemd</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</refentrytitle>
  42                 <manvolnum>1</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd</refname>
  47                 <refname>init</refname>
  48                 <refpurpose>systemd System and Session Manager</refpurpose>
  49         </refnamediv>
  50
  51         <refsynopsisdiv>
  52                 <cmdsynopsis>
  53                         <command>systemd <arg choice="opt" rep="repeat">OPTIONS</arg></command>
  54                 </cmdsynopsis>
  55                 <cmdsynopsis>
  56                         <command>init <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="req">COMMAND</arg></command>
  57                 </cmdsynopsis>
  58         </refsynopsisdiv>
  59
  60         <refsect1>
  61                 <title>Description</title>
  62
  63                 <para>systemd is a system and session manager for
  64                 Linux operating systems. When run as first process on
  65                 boot (as PID 1), it acts as init system that brings
  66                 up and maintains userspace services.</para>
  67
  68                 <para>For compatibility with SysV, if systemd is called
  69                 as <command>init</command> and a PID that is not
  70                 1, it will execute <command>telinit</command> and pass
  71                 all command line arguments unmodified. That means
  72                 <command>init</command> and <command>telinit</command>
  73                 are mostly equivalent when invoked from normal login sessions. See
  74                 <citerefentry><refentrytitle>telinit</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  75                 for more information.</para>
  76         </refsect1>
  77
  78         <refsect1>
  79                 <title>Options</title>
  80
  81                 <para>The following options are understood:</para>
  82
  83                 <variablelist>
  84                         <varlistentry>
  85                                 <term><option>-h</option></term>
  86                                 <term><option>--help</option></term>
  87
  88                                 <listitem><para>Prints a short help
  89                                 text and exits.</para></listitem>
  90                         </varlistentry>
  91                         <varlistentry>
  92                                 <term><option>--unit=</option></term>
  93
  94                                 <listitem><para>Set default unit to
  95                                 activate on startup. If not specified
  96                                 defaults to
  97                                 <filename>default.target</filename>.</para></listitem>
  98                         </varlistentry>
  99                         <varlistentry>
 100                                 <term><option>--running-as=</option></term>
 101
 102                                 <listitem><para>Tell systemd to run in
 103                                 a particular mode. Argument is one of
 104                                 <option>system</option>,
 105                                 <option>session</option>. Normally it
 106                                 should not be necessary to pass this
 107                                 option, as systemd automatically
 108                                 detects the mode it is started
 109                                 in. This call is hence of little use
 110                                 except for
 111                                 debugging.</para></listitem>
 112                         </varlistentry>
 113                         <varlistentry>
 114                                 <term><option>--test</option></term>
 115
 116                                 <listitem><para>Determine startup
 117                                 sequence, dump it and exit. This is an
 118                                 option useful for debugging
 119                                 only.</para></listitem>
 120                         </varlistentry>
 121                         <varlistentry>
 122                                 <term><option>--dump-configuration-items</option></term>
 123
 124                                 <listitem><para>Dump understood unit
 125                                 configuration items. This outputs a
 126                                 terse but complete list of
 127                                 configuration items understood in unit
 128                                 definition files.</para></listitem>
 129                         </varlistentry>
 130                         <varlistentry>
 131                                 <term><option>--confirm-spawn</option></term>
 132
 133                                 <listitem><para>Ask for confirmation when spawning processes.</para></listitem>
 134                         </varlistentry>
 135                         <varlistentry>
 136                                 <term><option>--introspect=</option></term>
 137
 138                                 <listitem><para>Extract D-Bus
 139                                 interface introspection data. This is
 140                                 mostly useful at build at install time
 141                                 to generate data suitable for the
 142                                 D-Bus interfaces
 143                                 repository. Optionally the interface
 144                                 name for the introspection data may be
 145                                 specified. If omitted, the
 146                                 introspection data for all interfaces
 147                                 is dumped.</para></listitem>
 148                         </varlistentry>
 149                         <varlistentry>
 150                                 <term><option>--log-level=</option></term>
 151
 152                                 <listitem><para>Set log level. As
 153                                 argument this accepts a numerical log
 154                                 level or the well-known <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 155                                 symbolic names (lowercase):
 156                                 <option>emerg</option>,
 157                                 <option>alert</option>,
 158                                 <option>crit</option>,
 159                                 <option>err</option>,
 160                                 <option>warning</option>,
 161                                 <option>notice</option>,
 162                                 <option>info</option>,
 163                                 <option>debug</option>.</para></listitem>
 164                         </varlistentry>
 165                         <varlistentry>
 166                                 <term><option>--log-target=</option></term>
 167
 168                                 <listitem><para>Set log
 169                                 target. Argument must be one of
 170                                 <option>console</option>,
 171                                 <option>syslog</option>,
 172                                 <option>kmsg</option>,
 173                                 <option>syslog-or-kmsg</option>,
 174                                 <option>null</option>.</para></listitem>
 175                         </varlistentry>
 176                         <varlistentry>
 177                                 <term><option>--log-color=</option></term>
 178
 179                                 <listitem><para>Highlight important
 180                                 log messages. Argument is a boolean
 181                                 value. If the argument is omitted it
 182                                 defaults to
 183                                 <option>true</option>.</para></listitem>
 184                         </varlistentry>
 185                         <varlistentry>
 186                                 <term><option>--log-location=</option></term>
 187
 188                                 <listitem><para>Include code location
 189                                 in log messages. This is mostly
 190                                 relevant for debugging
 191                                 purposes. Argument is a boolean
 192                                 value. If the argument is omitted
 193                                 it defaults to
 194                                 <option>true</option>.</para></listitem>
 195                         </varlistentry>
 196                 </variablelist>
 197         </refsect1>
 198
 199         <refsect1>
 200                 <title>Concepts</title>
 201
 202                 <para>systemd provides a dependency system between
 203                 various entities called "units". Units encapsulate
 204                 various objects that are relevant for system boot-up
 205                 and maintainance. The majority of units are configured
 206                 in unit configuration files, whose syntax and basic
 207                 set of options is described in
 208                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 209                 however some are created automatically from other
 210                 configuration or dynamically from system state. Units
 211                 may be active (meaning started, bound, plugged in, ...
 212                 depending on the unit type), or inactive (meaning
 213                 stopped, unbound, unplugged, ...), as well is in the
 214                 process of being activated or deactivated,
 215                 i.e. between the two states. The following unit types
 216                 are available:</para>
 217
 218                 <orderedlist>
 219                         <listitem><para>Service units, which control
 220                         daemons and the processes they consist of. For
 221                         details see
 222                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 223
 224                         <listitem><para>Socket units, which
 225                         encapsulate local IPC or network sockets in
 226                         the system, useful for socket-based
 227                         activation. For details about socket units see
 228                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 229                         for details on socket-based activation and
 230                         other forms of activation, see
 231                         <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
 232
 233                         <listitem><para>Target units are useful to
 234                         group units, or provide well-known
 235                         synchronization points during boot-up, see
 236                         <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 237
 238                         <listitem><para>Device units expose kernel
 239                         devices in systemd and may be used to
 240                         implement device-based activation. For details
 241                         see
 242                         <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 243
 244                         <listitem><para>Mount units control mount
 245                         points in the file system, for details see
 246                         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 247
 248                         <listitem><para>Automount units provide
 249                         automount capabilities, for on-demand mounting
 250                         of file systems as well as parallelized
 251                         boot-up. See
 252                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 253
 254                         <listitem><para>Snapshot units can be used to
 255                         temporarily save the state of the set of
 256                         systemd units, which later may be restored by
 257                         activating the saved snapshot unit. For more
 258                         information see
 259                         <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 260
 261                         <listitem><para>Timer units are useful for
 262                         triggering activation of other units based on
 263                         timers. You may find details in
 264                         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 265
 266                         <listitem><para>Swap units are very similar to
 267                         mount units and encapsulated memory swap
 268                         partitions or files of the operating
 269                         systemd. They are described in <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 270
 271                         <listitem><para>Path units may be used
 272                         activate other services when file system
 273                         objects change or are modified. See
 274                         <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
 275
 276                 </orderedlist>
 277
 278                 <para>Units are named as their configuration
 279                 files. Some units have special semantics. A detailed
 280                 list you may find in
 281                 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 282
 283                 <para>On boot systemd activates the target unit
 284                 <filename>default.target</filename> whose job it is to
 285                 activate on-boot services and other on-boot units by
 286                 pulling them in via dependencies. Usually the unit
 287                 name is just an alias (symlink) for either
 288                 <filename>graphical.target</filename> (for
 289                 fully-featured boots into the UI) or
 290                 <filename>multi-user.target</filename> (for limited
 291                 console-only boots for use in embedded or server
 292                 environments, or similar; a subset of
 293                 graphical.target). However it is at the discretion of
 294                 the administrator to configure it as an alias to any
 295                 other target unit. See
 296                 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 297                 for details about these target units.</para>
 298
 299                 <para>For more information about the concepts and
 300                 ideas behind systemd please refer to the <ulink
 301                 url="http://0pointer.de/blog/projects/systemd.html">Original
 302                 Announcement Document</ulink>.</para>
 303         </refsect1>
 304
 305         <refsect1>
 306                 <title>Directories</title>
 307
 308                 <variablelist>
 309                         <varlistentry>
 310                                 <term>System unit directories</term>
 311
 312                                 <listitem><para>The systemd system
 313                                 manager reads unit configuration from
 314                                 various directories. Packages that
 315                                 want to install unit files shall place
 316                                 them in the directory returned by
 317                                 <command>pkg-config systemd
 318                                 --variable=systemdsystemunitdir</command>. Other
 319                                 directories checked are
 320                                 <filename>/usr/local/share/systemd/system</filename>
 321                                 and
 322                                 <filename>/usr/share/systemd/system</filename>. User
 323                                 configuration always takes
 324                                 precedence. <command>pkg-config
 325                                 systemd
 326                                 --variable=systemdsystemconfdir</command>
 327                                 returns the path of the system
 328                                 configuration directory. Packages
 329                                 should alter the content of these directories
 330                                 only with the
 331                                 <citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 332                                 tool.</para></listitem>
 333                         </varlistentry>
 334                 </variablelist>
 335
 336                 <variablelist>
 337                         <varlistentry>
 338                                 <term>Session unit directories</term>
 339
 340                                 <listitem><para>Similar rules apply
 341                                 for the session unit
 342                                 directories. However, here the <ulink
 343                                 url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
 344                                 Base Directory specification</ulink>
 345                                 is followed to find
 346                                 units. Applications should place their
 347                                 unit files in the directory returned
 348                                 by <command>pkg-config systemd
 349                                 --variable=systemdsessionunitdir</command>. Global
 350                                 configuration is done in the
 351                                 directory reported by
 352                                 <command>pkg-config systemd
 353                                 --variable=systemdsessionconfdir</command>. The
 354                                 <citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 355                                 tool can handle both global (i.e. for
 356                                 all users) and private (for one user)
 357                                 enabling/disabling of
 358                                 units.</para></listitem>
 359                         </varlistentry>
 360                 </variablelist>
 361
 362                 <variablelist>
 363                         <varlistentry>
 364                                 <term>SysV init scripts directory</term>
 365
 366                                 <listitem><para>The location of the
 367                                 SysV init script directory varies
 368                                 between distributions. If systemd
 369                                 cannot find a native unit file for a
 370                                 requested service, it will look for a
 371                                 SysV init script of the same name
 372                                 (with the
 373                                 <filename>.service</filename> suffix
 374                                 removed).</para></listitem>
 375                         </varlistentry>
 376                 </variablelist>
 377
 378                 <variablelist>
 379                         <varlistentry>
 380                                 <term>SysV runlevel link farm directory</term>
 381
 382                                 <listitem><para>The location of the
 383                                 SysV runlevel link farm directory
 384                                 varies between distributions. systemd
 385                                 will take the link farm into account
 386                                 when figuring out whether a service
 387                                 shall be enabled. Note that a service
 388                                 unit with a native unit configuration
 389                                 file can be started by activating it
 390                                 in the SysV runlevel link
 391                                 farm.</para></listitem>
 392                         </varlistentry>
 393                 </variablelist>
 394         </refsect1>
 395
 396         <refsect1>
 397                 <title>Signals</title>
 398
 399                 <variablelist>
 400                         <varlistentry>
 401                                 <term>SIGTERM</term>
 402
 403                                 <listitem><para>Upon receiving this
 404                                 signal the systemd system manager
 405                                 serializes its state, reexecutes
 406                                 itself and deserializes the saved
 407                                 state again. This is mostly equivalent
 408                                 to <command>systemctl
 409                                 daemon-reexec</command>.</para>
 410
 411                                 <para>systemd session managers will
 412                                 start the
 413                                 <filename>exit.target</filename> unit
 414                                 when this signal is received. This is
 415                                 mostly equivalent to
 416                                 <command>systemctl --session start
 417                                 exit.target</command>.</para></listitem>
 418                         </varlistentry>
 419
 420                         <varlistentry>
 421                                 <term>SIGINT</term>
 422
 423                                 <listitem><para>Upon receiving this
 424                                 signal the systemd system manager will
 425                                 start the
 426                                 <filename>ctrl-alt-del.target</filename> unit. This
 427                                 is mostly equivalent to
 428                                 <command>systemctl start
 429                                 ctl-alt-del.target</command>.</para>
 430
 431                                 <para>systemd session managers
 432                                 treat this signal the same way as
 433                                 SIGTERM.</para></listitem>
 434                         </varlistentry>
 435
 436                         <varlistentry>
 437                                 <term>SIGWINCH</term>
 438
 439                                 <listitem><para>When this signal is
 440                                 received the systemd system manager
 441                                 will start the
 442                                 <filename>kbrequest.target</filename>
 443                                 unit. This is mostly equivalent to
 444                                 <command>systemctl start
 445                                 kbrequest.target</command>.</para>
 446
 447                                 <para>This signal is ignored by
 448                                 systemd session
 449                                 managers.</para></listitem>
 450                         </varlistentry>
 451
 452                         <varlistentry>
 453                                 <term>SIGPWR</term>
 454
 455                                 <listitem><para>When this signal is
 456                                 received the systemd manager
 457                                 will start the
 458                                 <filename>sigpwr.target</filename>
 459                                 unit. This is mostly equivalent to
 460                                 <command>systemctl start
 461                                 sigpwr.target</command>.</para></listitem>
 462                         </varlistentry>
 463
 464                         <varlistentry>
 465                                 <term>SIGUSR1</term>
 466
 467                                 <listitem><para>When this signal is
 468                                 received the systemd manager will try
 469                                 to reconnect to the D-Bus
 470                                 bus.</para></listitem>
 471                         </varlistentry>
 472
 473                         <varlistentry>
 474                                 <term>SIGUSR2</term>
 475
 476                                 <listitem><para>When this signal is
 477                                 received the systemd manager will log
 478                                 its complete state in human readable
 479                                 form. The data logged is the same as
 480                                 printed by <command>systemctl
 481                                 dump</command>.</para></listitem>
 482                         </varlistentry>
 483
 484                         <varlistentry>
 485                                 <term>SIGHUP</term>
 486
 487                                 <listitem><para>Reloads the complete
 488                                 daemon configuration. This is mostly
 489                                 equivalent to <command>systemctl
 490                                 daemon-reload</command>.</para></listitem>
 491                         </varlistentry>
 492
 493                         <varlistentry>
 494                                 <term>SIGRTMIN+0</term>
 495
 496                                 <listitem><para>Enters default mode, starts the
 497                                 <filename>default.target</filename>
 498                                 unit. This is mostly equivalent to
 499                                 <command>systemctl start
 500                                 default.target</command>.</para></listitem>
 501                         </varlistentry>
 502
 503                         <varlistentry>
 504                                 <term>SIGRTMIN+1</term>
 505
 506                                 <listitem><para>Enters rescue mode,
 507                                 starts the
 508                                 <filename>rescue.target</filename>
 509                                 unit. This is mostly equivalent to
 510                                 <command>systemctl isolate
 511                                 rescue.target</command>.</para></listitem>
 512                         </varlistentry>
 513
 514                         <varlistentry>
 515                                 <term>SIGRTMIN+2</term>
 516
 517                                 <listitem><para>Enters emergency mode,
 518                                 starts the
 519                                 <filename>emergency.service</filename>
 520                                 unit. This is mostly equivalent to
 521                                 <command>systemctl isolate
 522                                 emergency.service</command>.</para></listitem>
 523                         </varlistentry>
 524
 525                         <varlistentry>
 526                                 <term>SIGRTMIN+3</term>
 527
 528                                 <listitem><para>Halts the machine,
 529                                 starts the
 530                                 <filename>halt.target</filename>
 531                                 unit. This is mostly equivalent to
 532                                 <command>systemctl start
 533                                 halt.target</command>.</para></listitem>
 534                         </varlistentry>
 535
 536                         <varlistentry>
 537                                 <term>SIGRTMIN+4</term>
 538
 539                                 <listitem><para>Powers off the machine,
 540                                 starts the
 541                                 <filename>poweroff.target</filename>
 542                                 unit. This is mostly equivalent to
 543                                 <command>systemctl start
 544                                 poweroff.target</command>.</para></listitem>
 545                         </varlistentry>
 546
 547                         <varlistentry>
 548                                 <term>SIGRTMIN+5</term>
 549
 550                                 <listitem><para>Reboots the machine,
 551                                 starts the
 552                                 <filename>reboot.target</filename>
 553                                 unit. This is mostly equivalent to
 554                                 <command>systemctl start
 555                                 reboot.target</command>.</para></listitem>
 556                         </varlistentry>
 557                 </variablelist>
 558         </refsect1>
 559
 560         <refsect1>
 561                 <title>Environment</title>
 562
 563                 <variablelist>
 564                         <varlistentry>
 565                                 <term><varname>$SYSTEMD_LOG_LEVEL</varname></term>
 566                                 <listitem><para>systemd reads the
 567                                 log level from this environment
 568                                 variable. This can be overridden with
 569                                 <option>--log-level=</option>.</para></listitem>
 570                         </varlistentry>
 571
 572                         <varlistentry>
 573                                 <term><varname>$SYSTEMD_LOG_TARGET</varname></term>
 574                                 <listitem><para>systemd reads the
 575                                 log target from this environment
 576                                 variable. This can be overridden with
 577                                 <option>--log-target=</option>.</para></listitem>
 578                         </varlistentry>
 579
 580                         <varlistentry>
 581                                 <term><varname>$SYSTEMD_LOG_COLOR</varname></term>
 582                                 <listitem><para>Controls whether
 583                                 systemd highlights important log
 584                                 messages. This can be overridden with
 585                                 <option>--log-color=</option>.</para></listitem>
 586                         </varlistentry>
 587
 588                         <varlistentry>
 589                                 <term><varname>$SYSTEMD_LOG_LOCATION</varname></term>
 590                                 <listitem><para>Controls whether
 591                                 systemd prints the code location along
 592                                 with log messages. This can be
 593                                 overridden with
 594                                 <option>--log-location=</option>.</para></listitem>
 595                         </varlistentry>
 596
 597                         <varlistentry>
 598                                 <term><varname>$XDG_CONFIG_HOME</varname></term>
 599                                 <term><varname>$XDG_CONFIG_DIRS</varname></term>
 600                                 <term><varname>$XDG_DATA_HOME</varname></term>
 601                                 <term><varname>$XDG_DATA_DIRS</varname></term>
 602
 603                                 <listitem><para>The systemd session
 604                                 manager uses these variables in
 605                                 accordance to the <ulink
 606                                 url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
 607                                 Base Directory specification</ulink>
 608                                 to find its configuration.</para></listitem>
 609                         </varlistentry>
 610
 611                         <varlistentry>
 612                                 <term><varname>$SYSTEMD_UNIT_PATH</varname></term>
 613
 614                                 <listitem><para>Controls where systemd
 615                                 looks for unit
 616                                 files.</para></listitem>
 617                         </varlistentry>
 618
 619                         <varlistentry>
 620                                 <term><varname>$SYSTEMD_SYSVINIT_PATH</varname></term>
 621
 622                                 <listitem><para>Controls where systemd
 623                                 looks for SysV init scripts.</para></listitem>
 624                         </varlistentry>
 625
 626                         <varlistentry>
 627                                 <term><varname>$SYSTEMD_SYSVRCND_PATH</varname></term>
 628
 629                                 <listitem><para>Controls where systemd
 630                                 looks for SysV init script runlevel link
 631                                 farms.</para></listitem>
 632                         </varlistentry>
 633
 634                         <varlistentry>
 635                                 <term><varname>$LISTEN_PID</varname></term>
 636                                 <term><varname>$LISTEN_FDS</varname></term>
 637
 638                                 <listitem><para>Set by systemd for
 639                                 supervised processes during
 640                                 socket-based activation. See
 641                                 <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 642                                 for more information.
 643                                 </para></listitem>
 644                         </varlistentry>
 645
 646                         <varlistentry>
 647                                 <term><varname>$NOTIFY_SOCKET</varname></term>
 648
 649                                 <listitem><para>Set by systemd for
 650                                 supervised processes for status and
 651                                 start-up completion notification. See
 652                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 653                                 for more information.
 654                                 </para></listitem>
 655                         </varlistentry>
 656                 </variablelist>
 657         </refsect1>
 658
 659         <refsect1>
 660                 <title>Sockets and FIFOs</title>
 661
 662                 <variablelist>
 663                         <varlistentry>
 664                                 <term><filename>@/org/freedesktop/systemd1/notify</filename></term>
 665
 666                                 <listitem><para>Daemon status
 667                                 notification socket. This is an AF_UNIX
 668                                 datagram socket in the Linux abstract
 669                                 namespace, and is used to implement
 670                                 the daemon notification logic as
 671                                 implemented by
 672                                 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 673
 674                         </varlistentry>
 675
 676                         <varlistentry>
 677                                 <term><filename>@/org/freedesktop/systemd1/logger</filename></term>
 678
 679                                 <listitem><para>Used internally by the
 680                                 <filename>systemd-logger.service</filename>
 681                                 unit to connect STDOUT and/or STDERR
 682                                 of spawned processes to
 683                                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 684                                 or the kernel log buffer. This is an
 685                                 AF_UNIX stream socket in the Linux
 686                                 abstract namespace.</para></listitem>
 687                         </varlistentry>
 688
 689                         <varlistentry>
 690                                 <term><filename>@/org/freedesktop/systemd1/private</filename></term>
 691
 692                                 <listitem><para>Used internally as
 693                                 communication channel between
 694                                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 695                                 and the systemd process. This is an
 696                                 AF_UNIX stream socket in the Linux
 697                                 abstract namespace. This interface is
 698                                 private to systemd and should not be
 699                                 used in external
 700                                 projects.</para></listitem>
 701                         </varlistentry>
 702
 703                         <varlistentry>
 704                                 <term><filename>/dev/initctl</filename></term>
 705
 706                                 <listitem><para>Limited compatibility
 707                                 support for the SysV client interface,
 708                                 as implemented by the
 709                                 <filename>systemd-initctl.service</filename>
 710                                 unit. This is a named pipe in the file
 711                                 system. This interface is obsolete and
 712                                 should not be used in new
 713                                 applications.</para></listitem>
 714                         </varlistentry>
 715                 </variablelist>
 716         </refsect1>
 717
 718         <refsect1>
 719                 <title>See Also</title>
 720                 <para>
 721                         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 722                         <citerefentry><refentrytitle>systemadm</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 723                         <citerefentry><refentrytitle>systemd-install</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 724                         <citerefentry><refentrytitle>systemd-notify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 725                         <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 726                         <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 727                         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 728                         <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 729                         <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 730                 </para>
 731         </refsect1>
 732
 733 </refentry>