man/systemd.exec.xml

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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 Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
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  14
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  18   Lesser General Public License for more details.
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  23
  24 <refentry id="systemd.exec">
  25         <refentryinfo>
  26                 <title>systemd.exec</title>
  27                 <productname>systemd</productname>
  28
  29                 <authorgroup>
  30                         <author>
  31                                 <contrib>Developer</contrib>
  32                                 <firstname>Lennart</firstname>
  33                                 <surname>Poettering</surname>
  34                                 <email>lennart@poettering.net</email>
  35                         </author>
  36                 </authorgroup>
  37         </refentryinfo>
  38
  39         <refmeta>
  40                 <refentrytitle>systemd.exec</refentrytitle>
  41                 <manvolnum>5</manvolnum>
  42         </refmeta>
  43
  44         <refnamediv>
  45                 <refname>systemd.exec</refname>
  46                 <refpurpose>Execution environment configuration</refpurpose>
  47         </refnamediv>
  48
  49         <refsynopsisdiv>
  50                 <para><filename><replaceable>service</replaceable>.service</filename>,
  51                 <filename><replaceable>socket</replaceable>.socket</filename>,
  52                 <filename><replaceable>mount</replaceable>.mount</filename>,
  53                 <filename><replaceable>swap</replaceable>.swap</filename></para>
  54         </refsynopsisdiv>
  55
  56         <refsect1>
  57                 <title>Description</title>
  58
  59                 <para>Unit configuration files for services, sockets,
  60                 mount points, and swap devices share a subset of
  61                 configuration options which define the execution
  62                 environment of spawned processes.</para>
  63
  64                 <para>This man page lists the configuration options
  65                 shared by these four unit types. See
  66                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  67                 for the common options of all unit configuration
  68                 files, and
  69                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  70                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  71                 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  72                 and
  73                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  74                 for more information on the specific unit
  75                 configuration files. The execution specific
  76                 configuration options are configured in the [Service],
  77                 [Socket], [Mount], or [Swap] sections, depending on the unit
  78                 type.</para>
  79         </refsect1>
  80
  81         <refsect1>
  82                 <title>Options</title>
  83
  84                 <variablelist class='unit-directives'>
  85
  86                         <varlistentry>
  87                                 <term><varname>WorkingDirectory=</varname></term>
  88
  89                                 <listitem><para>Takes an absolute
  90                                 directory path. Sets the working
  91                                 directory for executed processes. If
  92                                 not set, defaults to the root directory
  93                                 when systemd is running as a system
  94                                 instance and the respective user's
  95                                 home directory if run as
  96                                 user.</para></listitem>
  97                         </varlistentry>
  98
  99                         <varlistentry>
 100                                 <term><varname>RootDirectory=</varname></term>
 101
 102                                 <listitem><para>Takes an absolute
 103                                 directory path. Sets the root
 104                                 directory for executed processes, with
 105                                 the
 106                                 <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 107                                 system call. If this is used, it must
 108                                 be ensured that the process and all
 109                                 its auxiliary files are available in
 110                                 the <function>chroot()</function>
 111                                 jail.</para></listitem>
 112                         </varlistentry>
 113
 114                         <varlistentry>
 115                                 <term><varname>User=</varname></term>
 116                                 <term><varname>Group=</varname></term>
 117
 118                                 <listitem><para>Sets the Unix user
 119                                 or group that the processes are executed
 120                                 as, respectively. Takes a single user or group
 121                                 name or ID as argument. If no group is
 122                                 set, the default group of the user is
 123                                 chosen.</para></listitem>
 124                         </varlistentry>
 125
 126                         <varlistentry>
 127                                 <term><varname>SupplementaryGroups=</varname></term>
 128
 129                                 <listitem><para>Sets the supplementary
 130                                 Unix groups the processes are executed
 131                                 as. This takes a space-separated list
 132                                 of group names or IDs. This option may
 133                                 be specified more than once in which
 134                                 case all listed groups are set as
 135                                 supplementary groups. When the empty
 136                                 string is assigned the list of
 137                                 supplementary groups is reset, and all
 138                                 assignments prior to this one will
 139                                 have no effect. In any way, this
 140                                 option does not override, but extends
 141                                 the list of supplementary groups
 142                                 configured in the system group
 143                                 database for the
 144                                 user.</para></listitem>
 145                         </varlistentry>
 146
 147                         <varlistentry>
 148                                 <term><varname>Nice=</varname></term>
 149
 150                                 <listitem><para>Sets the default nice
 151                                 level (scheduling priority) for
 152                                 executed processes. Takes an integer
 153                                 between -20 (highest priority) and 19
 154                                 (lowest priority). See
 155                                 <citerefentry><refentrytitle>setpriority</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 156                                 for details.</para></listitem>
 157                         </varlistentry>
 158
 159                         <varlistentry>
 160                                 <term><varname>OOMScoreAdjust=</varname></term>
 161
 162                                 <listitem><para>Sets the adjustment
 163                                 level for the Out-Of-Memory killer for
 164                                 executed processes. Takes an integer
 165                                 between -1000 (to disable OOM killing
 166                                 for this process) and 1000 (to make
 167                                 killing of this process under memory
 168                                 pressure very likely). See <ulink
 169                                 url="https://www.kernel.org/doc/Documentation/filesystems/proc.txt">proc.txt</ulink>
 170                                 for details.</para></listitem>
 171                         </varlistentry>
 172
 173                         <varlistentry>
 174                                 <term><varname>IOSchedulingClass=</varname></term>
 175
 176                                 <listitem><para>Sets the IO scheduling
 177                                 class for executed processes. Takes an
 178                                 integer between 0 and 3 or one of the
 179                                 strings <option>none</option>,
 180                                 <option>realtime</option>,
 181                                 <option>best-effort</option> or
 182                                 <option>idle</option>. See
 183                                 <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 184                                 for details.</para></listitem>
 185                         </varlistentry>
 186
 187                         <varlistentry>
 188                                 <term><varname>IOSchedulingPriority=</varname></term>
 189
 190                                 <listitem><para>Sets the IO scheduling
 191                                 priority for executed processes. Takes
 192                                 an integer between 0 (highest
 193                                 priority) and 7 (lowest priority). The
 194                                 available priorities depend on the
 195                                 selected IO scheduling class (see
 196                                 above). See
 197                                 <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 198                                 for details.</para></listitem>
 199                         </varlistentry>
 200
 201                         <varlistentry>
 202                                 <term><varname>CPUSchedulingPolicy=</varname></term>
 203
 204                                 <listitem><para>Sets the CPU
 205                                 scheduling policy for executed
 206                                 processes. Takes one of
 207                                 <option>other</option>,
 208                                 <option>batch</option>,
 209                                 <option>idle</option>,
 210                                 <option>fifo</option> or
 211                                 <option>rr</option>. See
 212                                 <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 213                                 for details.</para></listitem>
 214                         </varlistentry>
 215
 216                         <varlistentry>
 217                                 <term><varname>CPUSchedulingPriority=</varname></term>
 218
 219                                 <listitem><para>Sets the CPU
 220                                 scheduling priority for executed
 221                                 processes. The available priority
 222                                 range depends on the selected CPU
 223                                 scheduling policy (see above). For
 224                                 real-time scheduling policies an
 225                                 integer between 1 (lowest priority)
 226                                 and 99 (highest priority) can be used.
 227                                 See <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 228                                 for details.
 229                                 </para></listitem>
 230                         </varlistentry>
 231
 232                         <varlistentry>
 233                                 <term><varname>CPUSchedulingResetOnFork=</varname></term>
 234
 235                                 <listitem><para>Takes a boolean
 236                                 argument. If true, elevated CPU
 237                                 scheduling priorities and policies
 238                                 will be reset when the executed
 239                                 processes fork, and can hence not leak
 240                                 into child processes. See
 241                                 <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 242                                 for details. Defaults to false.</para></listitem>
 243                         </varlistentry>
 244
 245                         <varlistentry>
 246                                 <term><varname>CPUAffinity=</varname></term>
 247
 248                                 <listitem><para>Controls the CPU
 249                                 affinity of the executed
 250                                 processes. Takes a space-separated
 251                                 list of CPU indexes. This option may
 252                                 be specified more than once in which
 253                                 case the specificed CPU affinity masks
 254                                 are merged. If the empty string is
 255                                 assigned, the mask is reset, all
 256                                 assignments prior to this will have no
 257                                 effect. See
 258                                 <citerefentry><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 259                                 for details.</para></listitem>
 260                         </varlistentry>
 261
 262                         <varlistentry>
 263                                 <term><varname>UMask=</varname></term>
 264
 265                                 <listitem><para>Controls the file mode
 266                                 creation mask. Takes an access mode in
 267                                 octal notation. See
 268                                 <citerefentry><refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 269                                 for details. Defaults to
 270                                 0022.</para></listitem>
 271                         </varlistentry>
 272
 273                         <varlistentry>
 274                                 <term><varname>Environment=</varname></term>
 275
 276                                 <listitem><para>Sets environment
 277                                 variables for executed
 278                                 processes. Takes a space-separated
 279                                 list of variable assignments. This
 280                                 option may be specified more than once
 281                                 in which case all listed variables
 282                                 will be set. If the same variable is
 283                                 set twice, the later setting will
 284                                 override the earlier setting. If the
 285                                 empty string is assigned to this
 286                                 option, the list of environment
 287                                 variables is reset, all prior
 288                                 assignments have no effect.
 289                                 Variable expansion is not performed
 290                                 inside the strings, however, specifier
 291                                 expansion is possible. The $ character has
 292                                 no special meaning.
 293                                 If you need to assign a value containing spaces
 294                                 to a variable, use double quotes (")
 295                                 for the assignment.</para>
 296
 297                                 <para>Example:
 298                                 <programlisting>Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"</programlisting>
 299                                 gives three variables <literal>VAR1</literal>,
 300                                 <literal>VAR2</literal>, <literal>VAR3</literal>
 301                                 with the values <literal>word1 word2</literal>,
 302                                 <literal>word3</literal>, <literal>$word 5 6</literal>.
 303                                 </para>
 304
 305                                 <para>
 306                                 See
 307                                 <citerefentry><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 308                                 for details about environment variables.</para></listitem>
 309                         </varlistentry>
 310                         <varlistentry>
 311                                 <term><varname>EnvironmentFile=</varname></term>
 312                                 <listitem><para>Similar to
 313                                 <varname>Environment=</varname> but
 314                                 reads the environment variables from a
 315                                 text file. The text file should
 316                                 contain new-line-separated variable
 317                                 assignments. Empty lines and lines
 318                                 starting with ; or # will be ignored,
 319                                 which may be used for commenting. A line
 320                                 ending with a backslash will be concatenated
 321                                 with the following one, allowing multiline variable
 322                                 definitions. The parser strips leading
 323                                 and trailing whitespace from the values
 324                                 of assignments, unless you use
 325                                 double quotes (").</para>
 326
 327                                 <para>The argument passed should be an
 328                                 absolute filename or wildcard
 329                                 expression, optionally prefixed with
 330                                 <literal>-</literal>, which indicates
 331                                 that if the file does not exist, it
 332                                 will not be read and no error or warning
 333                                 message is logged.  This option may be
 334                                 specified more than once in which case
 335                                 all specified files are read. If the
 336                                 empty string is assigned to this
 337                                 option, the list of file to read is
 338                                 reset, all prior assignments have no
 339                                 effect.</para>
 340
 341                                 <para>The files listed with this
 342                                 directive will be read shortly before
 343                                 the process is executed. Settings from
 344                                 these files override settings made
 345                                 with
 346                                 <varname>Environment=</varname>. If
 347                                 the same variable is set twice from
 348                                 these files, the files will be read in
 349                                 the order they are specified and the
 350                                 later setting will override the
 351                                 earlier setting.</para></listitem>
 352                         </varlistentry>
 353
 354                         <varlistentry>
 355                                 <term><varname>StandardInput=</varname></term>
 356                                 <listitem><para>Controls where file
 357                                 descriptor 0 (STDIN) of the executed
 358                                 processes is connected to. Takes one
 359                                 of <option>null</option>,
 360                                 <option>tty</option>,
 361                                 <option>tty-force</option>,
 362                                 <option>tty-fail</option> or
 363                                 <option>socket</option>. If
 364                                 <option>null</option> is selected,
 365                                 standard input will be connected to
 366                                 <filename>/dev/null</filename>,
 367                                 i.e. all read attempts by the process
 368                                 will result in immediate EOF. If
 369                                 <option>tty</option> is selected,
 370                                 standard input is connected to a TTY
 371                                 (as configured by
 372                                 <varname>TTYPath=</varname>, see
 373                                 below) and the executed process
 374                                 becomes the controlling process of the
 375                                 terminal. If the terminal is already
 376                                 being controlled by another process, the
 377                                 executed process waits until the current
 378                                 controlling process releases the
 379                                 terminal.
 380                                 <option>tty-force</option>
 381                                 is similar to <option>tty</option>,
 382                                 but the executed process is forcefully
 383                                 and immediately made the controlling
 384                                 process of the terminal, potentially
 385                                 removing previous controlling
 386                                 processes from the
 387                                 terminal. <option>tty-fail</option> is
 388                                 similar to <option>tty</option> but if
 389                                 the terminal already has a controlling
 390                                 process start-up of the executed
 391                                 process fails.  The
 392                                 <option>socket</option> option is only
 393                                 valid in socket-activated services,
 394                                 and only when the socket configuration
 395                                 file (see
 396                                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 397                                 for details) specifies a single socket
 398                                 only. If this option is set, standard
 399                                 input will be connected to the socket
 400                                 the service was activated from, which
 401                                 is primarily useful for compatibility
 402                                 with daemons designed for use with the
 403                                 traditional
 404                                 <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 405                                 daemon. This setting defaults to
 406                                 <option>null</option>.</para></listitem>
 407                         </varlistentry>
 408                         <varlistentry>
 409                                 <term><varname>StandardOutput=</varname></term>
 410                                 <listitem><para>Controls where file
 411                                 descriptor 1 (STDOUT) of the executed
 412                                 processes is connected to. Takes one
 413                                 of <option>inherit</option>,
 414                                 <option>null</option>,
 415                                 <option>tty</option>,
 416                                 <option>syslog</option>,
 417                                 <option>kmsg</option>,
 418                                 <option>journal</option>,
 419                                 <option>syslog+console</option>,
 420                                 <option>kmsg+console</option>,
 421                                 <option>journal+console</option> or
 422                                 <option>socket</option>. If set to
 423                                 <option>inherit</option>, the file
 424                                 descriptor of standard input is
 425                                 duplicated for standard output. If set
 426                                 to <option>null</option>, standard
 427                                 output will be connected to
 428                                 <filename>/dev/null</filename>,
 429                                 i.e. everything written to it will be
 430                                 lost. If set to <option>tty</option>,
 431                                 standard output will be connected to a
 432                                 tty (as configured via
 433                                 <varname>TTYPath=</varname>, see
 434                                 below). If the TTY is used for output
 435                                 only, the executed process will not
 436                                 become the controlling process of the
 437                                 terminal, and will not fail or wait
 438                                 for other processes to release the
 439                                 terminal. <option>syslog</option>
 440                                 connects standard output to the
 441                                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 442                                 system syslog
 443                                 service. <option>kmsg</option>
 444                                 connects it with the kernel log buffer
 445                                 which is accessible via
 446                                 <citerefentry><refentrytitle>dmesg</refentrytitle><manvolnum>1</manvolnum></citerefentry>. <option>journal</option>
 447                                 connects it with the journal which is
 448                                 accessible via
 449                                 <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 450                                 (Note that everything that is written
 451                                 to syslog or kmsg is implicitly stored
 452                                 in the journal as well, those options
 453                                 are hence supersets of this
 454                                 one). <option>syslog+console</option>,
 455                                 <option>journal+console</option> and
 456                                 <option>kmsg+console</option> work
 457                                 similarly but copy the output to the
 458                                 system console as
 459                                 well. <option>socket</option> connects
 460                                 standard output to a socket from
 461                                 socket activation, semantics are
 462                                 similar to the respective option of
 463                                 <varname>StandardInput=</varname>.
 464                                 This setting defaults to the value set
 465                                 with
 466                                 <option>DefaultStandardOutput=</option>
 467                                 in
 468                                 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 469                                 which defaults to
 470                                 <option>journal</option>.</para></listitem>
 471                         </varlistentry>
 472                         <varlistentry>
 473                                 <term><varname>StandardError=</varname></term>
 474                                 <listitem><para>Controls where file
 475                                 descriptor 2 (STDERR) of the executed
 476                                 processes is connected to. The
 477                                 available options are identical to
 478                                 those of
 479                                 <varname>StandardOutput=</varname>,
 480                                 with one exception: if set to
 481                                 <option>inherit</option> the file
 482                                 descriptor used for standard output is
 483                                 duplicated for standard error. This
 484                                 setting defaults to the value set with
 485                                 <option>DefaultStandardError=</option>
 486                                 in
 487                                 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 488                                 which defaults to
 489                                 <option>inherit</option>.</para></listitem>
 490                         </varlistentry>
 491                         <varlistentry>
 492                                 <term><varname>TTYPath=</varname></term>
 493                                 <listitem><para>Sets the terminal
 494                                 device node to use if standard input,
 495                                 output or stderr are connected to a
 496                                 TTY (see above). Defaults to
 497                                 <filename>/dev/console</filename>.</para></listitem>
 498                         </varlistentry>
 499                         <varlistentry>
 500                                 <term><varname>TTYReset=</varname></term>
 501                                 <listitem><para>Reset the terminal
 502                                 device specified with
 503                                 <varname>TTYPath=</varname> before and
 504                                 after execution. Defaults to
 505                                 <literal>no</literal>.</para></listitem>
 506                         </varlistentry>
 507                         <varlistentry>
 508                                 <term><varname>TTYVHangup=</varname></term>
 509                                 <listitem><para>Disconnect all clients
 510                                 which have opened the terminal device
 511                                 specified with
 512                                 <varname>TTYPath=</varname>
 513                                 before and after execution. Defaults
 514                                 to
 515                                 <literal>no</literal>.</para></listitem>
 516                         </varlistentry>
 517                         <varlistentry>
 518                                 <term><varname>TTYVTDisallocate=</varname></term>
 519                                 <listitem><para>If the terminal
 520                                 device specified with
 521                                 <varname>TTYPath=</varname> is a
 522                                 virtual console terminal, try to
 523                                 deallocate the TTY before and after
 524                                 execution. This ensures that the
 525                                 screen and scrollback buffer is
 526                                 cleared. Defaults to
 527                                 <literal>no</literal>.</para></listitem>
 528                         </varlistentry>
 529                         <varlistentry>
 530                                 <term><varname>SyslogIdentifier=</varname></term>
 531                                 <listitem><para>Sets the process name
 532                                 to prefix log lines sent to syslog or
 533                                 the kernel log buffer with. If not set,
 534                                 defaults to the process name of the
 535                                 executed process. This option is only
 536                                 useful when
 537                                 <varname>StandardOutput=</varname> or
 538                                 <varname>StandardError=</varname> are
 539                                 set to <option>syslog</option> or
 540                                 <option>kmsg</option>.</para></listitem>
 541                         </varlistentry>
 542                         <varlistentry>
 543                                 <term><varname>SyslogFacility=</varname></term>
 544                                 <listitem><para>Sets the syslog
 545                                 facility to use when logging to
 546                                 syslog. One of <option>kern</option>,
 547                                 <option>user</option>,
 548                                 <option>mail</option>,
 549                                 <option>daemon</option>,
 550                                 <option>auth</option>,
 551                                 <option>syslog</option>,
 552                                 <option>lpr</option>,
 553                                 <option>news</option>,
 554                                 <option>uucp</option>,
 555                                 <option>cron</option>,
 556                                 <option>authpriv</option>,
 557                                 <option>ftp</option>,
 558                                 <option>local0</option>,
 559                                 <option>local1</option>,
 560                                 <option>local2</option>,
 561                                 <option>local3</option>,
 562                                 <option>local4</option>,
 563                                 <option>local5</option>,
 564                                 <option>local6</option> or
 565                                 <option>local7</option>. See
 566                                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 567                                 for details. This option is only
 568                                 useful when
 569                                 <varname>StandardOutput=</varname> or
 570                                 <varname>StandardError=</varname> are
 571                                 set to <option>syslog</option>.
 572                                 Defaults to
 573                                 <option>daemon</option>.</para></listitem>
 574                         </varlistentry>
 575                         <varlistentry>
 576                                 <term><varname>SyslogLevel=</varname></term>
 577                                 <listitem><para>Default syslog level
 578                                 to use when logging to syslog or the
 579                                 kernel log buffer. One of
 580                                 <option>emerg</option>,
 581                                 <option>alert</option>,
 582                                 <option>crit</option>,
 583                                 <option>err</option>,
 584                                 <option>warning</option>,
 585                                 <option>notice</option>,
 586                                 <option>info</option>,
 587                                 <option>debug</option>. See
 588                                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 589                                 for details. This option is only
 590                                 useful when
 591                                 <varname>StandardOutput=</varname> or
 592                                 <varname>StandardError=</varname> are
 593                                 set to <option>syslog</option> or
 594                                 <option>kmsg</option>. Note that
 595                                 individual lines output by the daemon
 596                                 might be prefixed with a different log
 597                                 level which can be used to override
 598                                 the default log level specified
 599                                 here. The interpretation of these
 600                                 prefixes may be disabled with
 601                                 <varname>SyslogLevelPrefix=</varname>,
 602                                 see below. For details see
 603                                 <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 604
 605                                 Defaults to
 606                                 <option>info</option>.</para></listitem>
 607                         </varlistentry>
 608
 609                         <varlistentry>
 610                                 <term><varname>SyslogLevelPrefix=</varname></term>
 611                                 <listitem><para>Takes a boolean
 612                                 argument. If true and
 613                                 <varname>StandardOutput=</varname> or
 614                                 <varname>StandardError=</varname> are
 615                                 set to <option>syslog</option>,
 616                                 <option>kmsg</option> or
 617                                 <option>journal</option>, log lines
 618                                 written by the executed process that
 619                                 are prefixed with a log level will be
 620                                 passed on to syslog with this log
 621                                 level set but the prefix removed. If
 622                                 set to false, the interpretation of
 623                                 these prefixes is disabled and the
 624                                 logged lines are passed on as-is. For
 625                                 details about this prefixing see
 626                                 <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 627                                 Defaults to true.</para></listitem>
 628                         </varlistentry>
 629
 630                         <varlistentry>
 631                                 <term><varname>TimerSlackNSec=</varname></term>
 632                                 <listitem><para>Sets the timer slack
 633                                 in nanoseconds for the executed
 634                                 processes. The timer slack controls
 635                                 the accuracy of wake-ups triggered by
 636                                 timers. See
 637                                 <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 638                                 for more information. Note that in
 639                                 contrast to most other time span
 640                                 definitions this parameter takes an
 641                                 integer value in nano-seconds if no
 642                                 unit is specified. The usual time
 643                                 units are understood
 644                                 too.</para></listitem>
 645                         </varlistentry>
 646
 647                         <varlistentry>
 648                                 <term><varname>LimitCPU=</varname></term>
 649                                 <term><varname>LimitFSIZE=</varname></term>
 650                                 <term><varname>LimitDATA=</varname></term>
 651                                 <term><varname>LimitSTACK=</varname></term>
 652                                 <term><varname>LimitCORE=</varname></term>
 653                                 <term><varname>LimitRSS=</varname></term>
 654                                 <term><varname>LimitNOFILE=</varname></term>
 655                                 <term><varname>LimitAS=</varname></term>
 656                                 <term><varname>LimitNPROC=</varname></term>
 657                                 <term><varname>LimitMEMLOCK=</varname></term>
 658                                 <term><varname>LimitLOCKS=</varname></term>
 659                                 <term><varname>LimitSIGPENDING=</varname></term>
 660                                 <term><varname>LimitMSGQUEUE=</varname></term>
 661                                 <term><varname>LimitNICE=</varname></term>
 662                                 <term><varname>LimitRTPRIO=</varname></term>
 663                                 <term><varname>LimitRTTIME=</varname></term>
 664                                 <listitem><para>These settings control
 665                                 various resource limits for executed
 666                                 processes. See
 667                                 <citerefentry><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 668                                 for details. Use the string
 669                                 <varname>infinity</varname> to
 670                                 configure no limit on a specific
 671                                 resource.</para></listitem>
 672                         </varlistentry>
 673
 674                         <varlistentry>
 675                                 <term><varname>PAMName=</varname></term>
 676                                 <listitem><para>Sets the PAM service
 677                                 name to set up a session as. If set,
 678                                 the executed process will be
 679                                 registered as a PAM session under the
 680                                 specified service name. This is only
 681                                 useful in conjunction with the
 682                                 <varname>User=</varname> setting. If
 683                                 not set, no PAM session will be opened
 684                                 for the executed processes. See
 685                                 <citerefentry><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 686                                 for details.</para></listitem>
 687                         </varlistentry>
 688
 689                         <varlistentry>
 690                                 <term><varname>TCPWrapName=</varname></term>
 691                                 <listitem><para>If this is a
 692                                 socket-activated service, this sets the
 693                                 tcpwrap service name to check the
 694                                 permission for the current connection
 695                                 with. This is only useful in
 696                                 conjunction with socket-activated
 697                                 services, and stream sockets (TCP) in
 698                                 particular. It has no effect on other
 699                                 socket types (e.g. datagram/UDP) and
 700                                 on processes unrelated to socket-based
 701                                 activation. If the tcpwrap
 702                                 verification fails, daemon start-up
 703                                 will fail and the connection is
 704                                 terminated. See
 705                                 <citerefentry><refentrytitle>tcpd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 706                                 for details. Note that this option may
 707                                 be used to do access control checks
 708                                 only. Shell commands and commands
 709                                 described in
 710                                 <citerefentry><refentrytitle>hosts_options</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 711                                 are not supported.</para></listitem>
 712                         </varlistentry>
 713
 714                         <varlistentry>
 715                                 <term><varname>CapabilityBoundingSet=</varname></term>
 716
 717                                 <listitem><para>Controls which
 718                                 capabilities to include in the
 719                                 capability bounding set for the
 720                                 executed process. See
 721                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 722                                 for details. Takes a whitespace-separated
 723                                 list of capability names as read by
 724                                 <citerefentry><refentrytitle>cap_from_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 725                                 e.g. <constant>CAP_SYS_ADMIN</constant>,
 726                                 <constant>CAP_DAC_OVERRIDE</constant>,
 727                                 <constant>CAP_SYS_PTRACE</constant>.
 728                                 Capabilities listed will be included
 729                                 in the bounding set, all others are
 730                                 removed. If the list of capabilities
 731                                 is prefixed with <literal>~</literal>,
 732                                 all but the listed capabilities will
 733                                 be included, the effect of the
 734                                 assignment inverted. Note that this
 735                                 option also affects the respective
 736                                 capabilities in the effective,
 737                                 permitted and inheritable capability
 738                                 sets, on top of what
 739                                 <varname>Capabilities=</varname>
 740                                 does. If this option is not used, the
 741                                 capability bounding set is not
 742                                 modified on process execution, hence
 743                                 no limits on the capabilities of the
 744                                 process are enforced. This option may
 745                                 appear more than once in which case
 746                                 the bounding sets are merged. If the
 747                                 empty string is assigned to this
 748                                 option, the bounding set is reset to
 749                                 the empty capability set, and all
 750                                 prior settings have no effect. If set
 751                                 to <literal>~</literal> (without any
 752                                 further argument), the bounding set is
 753                                 reset to the full set of available
 754                                 capabilities, also undoing any
 755                                 previous settings.</para></listitem>
 756                         </varlistentry>
 757
 758                         <varlistentry>
 759                                 <term><varname>SecureBits=</varname></term>
 760                                 <listitem><para>Controls the secure
 761                                 bits set for the executed process. See
 762                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 763                                 for details. Takes a list of strings:
 764                                 <option>keep-caps</option>,
 765                                 <option>keep-caps-locked</option>,
 766                                 <option>no-setuid-fixup</option>,
 767                                 <option>no-setuid-fixup-locked</option>,
 768                                 <option>noroot</option> and/or
 769                                 <option>noroot-locked</option>. This
 770                                 option may appear more than once in
 771                                 which case the secure bits are
 772                                 ORed. If the empty string is assigned
 773                                 to this option, the bits are reset to
 774                                 0.</para></listitem>
 775                         </varlistentry>
 776
 777                         <varlistentry>
 778                                 <term><varname>Capabilities=</varname></term>
 779                                 <listitem><para>Controls the
 780                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 781                                 set for the executed process. Take a
 782                                 capability string describing the
 783                                 effective, permitted and inherited
 784                                 capability sets as documented in
 785                                 <citerefentry><refentrytitle>cap_from_text</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 786                                 Note that these capability sets are
 787                                 usually influenced by the capabilities
 788                                 attached to the executed file. Due to
 789                                 that
 790                                 <varname>CapabilityBoundingSet=</varname>
 791                                 is probably the much more useful
 792                                 setting.</para></listitem>
 793                         </varlistentry>
 794
 795                         <varlistentry>
 796                                 <term><varname>ReadWriteDirectories=</varname></term>
 797                                 <term><varname>ReadOnlyDirectories=</varname></term>
 798                                 <term><varname>InaccessibleDirectories=</varname></term>
 799
 800                                 <listitem><para>Sets up a new
 801                                 file system namespace for executed
 802                                 processes. These options may be used
 803                                 to limit access a process might have
 804                                 to the main file system
 805                                 hierarchy. Each setting takes a
 806                                 space-separated list of absolute
 807                                 directory paths. Directories listed in
 808                                 <varname>ReadWriteDirectories=</varname>
 809                                 are accessible from within the
 810                                 namespace with the same access rights
 811                                 as from outside. Directories listed in
 812                                 <varname>ReadOnlyDirectories=</varname>
 813                                 are accessible for reading only,
 814                                 writing will be refused even if the
 815                                 usual file access controls would
 816                                 permit this. Directories listed in
 817                                 <varname>InaccessibleDirectories=</varname>
 818                                 will be made inaccessible for
 819                                 processes inside the namespace. Note
 820                                 that restricting access with these
 821                                 options does not extend to submounts
 822                                 of a directory. You must list
 823                                 submounts separately in these settings
 824                                 to ensure the same limited
 825                                 access. These options may be specified
 826                                 more than once in which case all
 827                                 directories listed will have limited
 828                                 access from within the namespace. If
 829                                 the empty string is assigned to this
 830                                 option, the specific list is reset, and
 831                                 all prior assignments have no
 832                                 effect.</para>
 833                                 <para>Paths in
 834                                 <varname>ReadOnlyDirectories=</varname>
 835                                 and
 836                                 <varname>InaccessibleDirectories=</varname>
 837                                 may be prefixed with
 838                                 <literal>-</literal>, in which case
 839                                 they will be ignored when they do not
 840                                 exist.</para></listitem>
 841                         </varlistentry>
 842
 843                         <varlistentry>
 844                                 <term><varname>PrivateTmp=</varname></term>
 845
 846                                 <listitem><para>Takes a boolean
 847                                 argument. If true, sets up a new file
 848                                 system namespace for the executed
 849                                 processes and mounts private
 850                                 <filename>/tmp</filename> and
 851                                 <filename>/var/tmp</filename>
 852                                 directories inside it that is not
 853                                 shared by processes outside of the
 854                                 namespace. This is useful to secure
 855                                 access to temporary files of the
 856                                 process, but makes sharing between
 857                                 processes via
 858                                 <filename>/tmp</filename> or
 859                                 <filename>/var/tmp</filename>
 860                                 impossible. All temporary data created
 861                                 by service will be removed after
 862                                 the service is stopped. Defaults to
 863                                 false. Note that it is possible to run
 864                                 two or more units within the same
 865                                 private <filename>/tmp</filename> and
 866                                 <filename>/var/tmp</filename>
 867                                 namespace by using the
 868                                 <varname>JoinsNamespaceOf=</varname>
 869                                 directive, see
 870                                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 871                                 for details.</para></listitem>
 872                         </varlistentry>
 873
 874                         <varlistentry>
 875                                 <term><varname>PrivateNetwork=</varname></term>
 876
 877                                 <listitem><para>Takes a boolean
 878                                 argument. If true, sets up a new
 879                                 network namespace for the executed
 880                                 processes and configures only the
 881                                 loopback network device
 882                                 <literal>lo</literal> inside it. No
 883                                 other network devices will be
 884                                 available to the executed process.
 885                                 This is useful to securely turn off
 886                                 network access by the executed
 887                                 process. Defaults to false. Note that
 888                                 it is possible to run two or more
 889                                 units within the same private network
 890                                 namespace by using the
 891                                 <varname>JoinsNamespaceOf=</varname>
 892                                 directive, see
 893                                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 894                                 for details.</para></listitem>
 895                         </varlistentry>
 896
 897                         <varlistentry>
 898                                 <term><varname>PrivateDevices=</varname></term>
 899
 900                                 <listitem><para>Takes a boolean
 901                                 argument. If true, sets up a new /dev
 902                                 namespace for the executed processes
 903                                 and only adds API pseudo devices such
 904                                 as <filename>/dev/null</filename>,
 905                                 <filename>/dev/zero</filename> or
 906                                 <filename>/dev/random</filename> to
 907                                 it, but no physical devices such as
 908                                 <filename>/dev/sda</filename>. This is
 909                                 useful to securely turn off physical
 910                                 device access by the executed
 911                                 process. Defaults to
 912                                 false.</para></listitem>
 913                         </varlistentry>
 914
 915                         <varlistentry>
 916                                 <term><varname>MountFlags=</varname></term>
 917
 918                                 <listitem><para>Takes a mount
 919                                 propagation flag:
 920                                 <option>shared</option>,
 921                                 <option>slave</option> or
 922                                 <option>private</option>, which
 923                                 control whether the file system
 924                                 namespace set up for this unit's
 925                                 processes will receive or propagate
 926                                 new mounts. See
 927                                 <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 928                                 for details. Default to
 929                                 <option>shared</option>.</para></listitem>
 930                         </varlistentry>
 931
 932                         <varlistentry>
 933                                 <term><varname>UtmpIdentifier=</varname></term>
 934
 935                                 <listitem><para>Takes a four
 936                                 character identifier string for an
 937                                 utmp/wtmp entry for this service. This
 938                                 should only be set for services such
 939                                 as <command>getty</command>
 940                                 implementations where utmp/wtmp
 941                                 entries must be created and cleared
 942                                 before and after execution. If the
 943                                 configured string is longer than four
 944                                 characters, it is truncated and the
 945                                 terminal four characters are
 946                                 used. This setting interprets %I style
 947                                 string replacements. This setting is
 948                                 unset by default, i.e. no utmp/wtmp
 949                                 entries are created or cleaned up for
 950                                 this service.</para></listitem>
 951                         </varlistentry>
 952
 953                         <varlistentry>
 954                                 <term><varname>SELinuxContext=</varname></term>
 955
 956                                 <listitem><para>Set the SELinux
 957                                 security context of the executed
 958                                 process. If set, this will override
 959                                 the automated domain
 960                                 transition. However, the policy still
 961                                 needs to autorize the transition. This
 962                                 directive is ignored if SELinux is
 963                                 disabled. If prefixed by
 964                                 <literal>-</literal>, all errors will
 965                                 be ignored. See
 966                                 <citerefentry><refentrytitle>setexeccon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 967                                 for details.</para></listitem>
 968                         </varlistentry>
 969
 970                         <varlistentry>
 971                                 <term><varname>IgnoreSIGPIPE=</varname></term>
 972
 973                                 <listitem><para>Takes a boolean
 974                                 argument. If true, causes <constant>SIGPIPE</constant> to be
 975                                 ignored in the executed
 976                                 process. Defaults to true because
 977                                 <constant>SIGPIPE</constant> generally is useful only in
 978                                 shell pipelines.</para></listitem>
 979                         </varlistentry>
 980
 981                         <varlistentry>
 982                                 <term><varname>NoNewPrivileges=</varname></term>
 983
 984                                 <listitem><para>Takes a boolean
 985                                 argument. If true, ensures that the
 986                                 service process and all its children
 987                                 can never gain new privileges. This
 988                                 option is more powerful than the respective
 989                                 secure bits flags (see above), as it
 990                                 also prohibits UID changes of any
 991                                 kind. This is the simplest, most
 992                                 effective way to ensure that a process
 993                                 and its children can never elevate
 994                                 privileges again.</para></listitem>
 995                         </varlistentry>
 996
 997                         <varlistentry>
 998                                 <term><varname>SystemCallFilter=</varname></term>
 999
1000                                 <listitem><para>Takes a space-separated
1001                                 list of system call
1002                                 names. If this setting is used, all
1003                                 system calls executed by the unit
1004                                 processes except for the listed ones
1005                                 will result in immediate process
1006                                 termination with the
1007                                 <constant>SIGSYS</constant> signal
1008                                 (whitelisting). If the first character
1009                                 of the list is <literal>~</literal>,
1010                                 the effect is inverted: only the
1011                                 listed system calls will result in
1012                                 immediate process termination
1013                                 (blacklisting). If this option is used,
1014                                 <varname>NoNewPrivileges=yes</varname>
1015                                 is implied. This feature makes use of
1016                                 the Secure Computing Mode 2 interfaces
1017                                 of the kernel ('seccomp filtering')
1018                                 and is useful for enforcing a minimal
1019                                 sandboxing environment. Note that the
1020                                 <function>execve</function>,
1021                                 <function>rt_sigreturn</function>,
1022                                 <function>sigreturn</function>,
1023                                 <function>exit_group</function>,
1024                                 <function>exit</function> system calls
1025                                 are implicitly whitelisted and do not
1026                                 need to be listed explicitly. This
1027                                 option may be specified more than once
1028                                 in which case the filter masks are
1029                                 merged. If the empty string is
1030                                 assigned, the filter is reset, all
1031                                 prior assignments will have no
1032                                 effect.</para>
1033
1034                                 <para>If you specify both types of
1035                                 this option (i.e. whitelisting and
1036                                 blacklisting) the first encountered
1037                                 will take precedence and will dictate
1038                                 the default action (termination or
1039                                 approval of a system call). Then the
1040                                 next occurrences of this option will
1041                                 add or delete the listed system calls
1042                                 from the set of the filtered system
1043                                 calls, depending of its type and the
1044                                 default action (e.g. You have started
1045                                 with a whitelisting of
1046                                 <function>read</function> and
1047                                 <function>write</function> and right
1048                                 after it add a blacklisting of
1049                                 <function>write</function>, then
1050                                 <function>write</function> will be
1051                                 removed from the set).
1052                                 </para></listitem>
1053
1054                                 <para>Note that setting
1055                                 <varname>SystemCallFilter=</varname>
1056                                 implies a
1057                                 <varname>SystemCallArchitectures=</varname>
1058                                 setting of <literal>native</literal>
1059                                 (see below), unless that option is
1060                                 configured otherwise.</para>
1061                         </varlistentry>
1062
1063                         <varlistentry>
1064                                 <term><varname>SystemCallErrorNumber=</varname></term>
1065
1066                                 <listitem><para>Takes an
1067                                 <literal>errno</literal> error number
1068                                 name to return when the system call
1069                                 filter configured with
1070                                 <varname>SystemCallFilter=</varname>
1071                                 is triggered, instead of terminating
1072                                 the process immediately. Takes an
1073                                 error name such as
1074                                 <literal>EPERM</literal>,
1075                                 <literal>EACCES</literal> or
1076                                 <literal>EUCLEAN</literal>. When this
1077                                 setting is not used, or when the empty
1078                                 string is assigned the process will be
1079                                 terminated immediately when the filter
1080                                 is triggered.</para></listitem>
1081                         </varlistentry>
1082
1083                         <varlistentry>
1084                                 <term><varname>SystemCallArchitectures=</varname></term>
1085
1086                                 <listitem><para>Takes a space
1087                                 separated list of architecture
1088                                 identifiers to include in the system
1089                                 call filter. The known architecture
1090                                 identifiers are
1091                                 <literal>x86</literal>,
1092                                 <literal>x86-64</literal>,
1093                                 <literal>x32</literal>,
1094                                 <literal>arm</literal> as well as the
1095                                 special identifier
1096                                 <literal>native</literal>. Only system
1097                                 calls of the specified architectures
1098                                 will be permitted to processes of this
1099                                 unit. This is an effective way to
1100                                 disable compatibility with non-native
1101                                 architectures for processes, for
1102                                 example to prohibit execution of 32bit
1103                                 x86 binaries on 64bit x86-64
1104                                 systems. The special
1105                                 <literal>native</literal> identifier
1106                                 implicitly maps to the native
1107                                 architecture of the system (or more
1108                                 strictly: to the architecture the
1109                                 system manager is compiled for). Note
1110                                 that setting this option to a
1111                                 non-empty list implies that
1112                                 <literal>native</literal> is included
1113                                 too. By default this option is set to
1114                                 the empty list, i.e. no architecture
1115                                 system call filtering is applied. Note
1116                                 that configuring a system call filter
1117                                 with
1118                                 <varname>SystemCallFilter=</varname>
1119                                 (above) implies a
1120                                 <literal>native</literal> architecture
1121                                 list, unless configured
1122                                 otherwise.</para></listitem>
1123                         </varlistentry>
1124
1125                 </variablelist>
1126         </refsect1>
1127
1128         <refsect1>
1129                 <title>Environment variables in spawned processes</title>
1130
1131                 <para>Processes started by the system are executed in
1132                 a clean environment in which select variables
1133                 listed below are set. System processes started by systemd
1134                 do not inherit variables from PID 1, but processes
1135                 started by user systemd instances inherit all
1136                 environment variables from the user systemd instance.
1137                 </para>
1138
1139                 <variablelist class='environment-variables'>
1140                         <varlistentry>
1141                                 <term><varname>$PATH</varname></term>
1142
1143                                 <listitem><para>Colon-separated list
1144                                 of directiories to use when launching
1145                                 executables. Systemd uses a fixed
1146                                 value of
1147                                 <filename>/usr/local/sbin</filename>:<filename>/usr/local/bin</filename>:<filename>/usr/sbin</filename>:<filename>/usr/bin</filename>:<filename>/sbin</filename>:<filename>/bin</filename>.
1148                                 </para></listitem>
1149                         </varlistentry>
1150
1151                         <varlistentry>
1152                                 <term><varname>$LANG</varname></term>
1153
1154                                 <listitem><para>Locale. Can be set in
1155                                 <citerefentry><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1156                                 or on the kernel command line (see
1157                                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1158                                 and
1159                                 <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>).
1160                                 </para></listitem>
1161                         </varlistentry>
1162
1163                         <varlistentry>
1164                                 <term><varname>$USER</varname></term>
1165                                 <term><varname>$LOGNAME</varname></term>
1166                                 <term><varname>$HOME</varname></term>
1167                                 <term><varname>$SHELL</varname></term>
1168
1169                                 <listitem><para>User name (twice), home
1170                                 directory, and the login shell.
1171                                 The variables are set for the units that
1172                                 have <varname>User=</varname> set,
1173                                 which includes user
1174                                 <command>systemd</command> instances.
1175                                 See
1176                                 <citerefentry><refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1177                                 </para></listitem>
1178                         </varlistentry>
1179
1180                         <varlistentry>
1181                                 <term><varname>$XDG_RUNTIME_DIR</varname></term>
1182
1183                                 <listitem><para>The directory for volatile
1184                                 state. Set for the user <command>systemd</command>
1185                                 instance, and also in user sessions.
1186                                 See
1187                                 <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
1188                                 </para></listitem>
1189                         </varlistentry>
1190
1191                         <varlistentry>
1192                                 <term><varname>$XDG_SESSION_ID</varname></term>
1193                                 <term><varname>$XDG_SEAT</varname></term>
1194                                 <term><varname>$XDG_VTNR</varname></term>
1195
1196                                 <listitem><para>The identifier of the
1197                                 session, the seat name, and
1198                                 virtual terminal of the session. Set
1199                                 by
1200                                 <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1201                                 for login sessions.
1202                                 <varname>$XDG_SEAT</varname> and
1203                                 <varname>$XDG_VTNR</varname> will
1204                                 only be set when attached to a seat and a
1205                                 tty.</para></listitem>
1206                         </varlistentry>
1207
1208                         <varlistentry>
1209                                 <term><varname>$MANAGERPID</varname></term>
1210
1211                                 <listitem><para>The PID of the user
1212                                 <command>systemd</command> instance,
1213                                 set for processes spawned by it.
1214                                 </para></listitem>
1215                         </varlistentry>
1216
1217                         <varlistentry>
1218                                 <term><varname>$LISTEN_FDS</varname></term>
1219                                 <term><varname>$LISTEN_PID</varname></term>
1220
1221                                 <listitem><para>Information about file
1222                                 descriptors passed to a service for
1223                                 socket activation.  See
1224                                 <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
1225                                 </para></listitem>
1226                         </varlistentry>
1227
1228                         <varlistentry>
1229                                 <term><varname>$TERM</varname></term>
1230
1231                                 <listitem><para>Terminal type, set
1232                                 only for units connected to a terminal
1233                                 (<varname>StandardInput=tty</varname>,
1234                                 <varname>StandardOutput=tty</varname>,
1235                                 or
1236                                 <varname>StandardError=tty</varname>).
1237                                 See
1238                                 <citerefentry><refentrytitle>termcap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1239                                 </para></listitem>
1240                         </varlistentry>
1241                 </variablelist>
1242
1243                 <para>Additional variables may be configured by the
1244                 following means: for processes spawned in specific
1245                 units, use the <varname>Environment=</varname> and
1246                 <varname>EnvironmentFile=</varname> options above; to
1247                 specify variables globally, use
1248                 <varname>DefaultEnvironment=</varname> (see
1249                 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
1250                 or the kernel option
1251                 <varname>systemd.setenv=</varname> (see
1252                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>). Additional
1253                 variables may also be set through PAM,
1254                 c.f. <citerefentry><refentrytitle>pam_env</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
1255         </refsect1>
1256
1257         <refsect1>
1258                   <title>See Also</title>
1259                   <para>
1260                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1261                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1262                           <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1263                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1264                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1265                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1266                           <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1267                           <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1268                           <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1269                           <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1270                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1271                           <citerefentry><refentrytitle>exec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
1272                   </para>
1273         </refsect1>
1274
1275 </refentry>