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6 This file is part of systemd.
8 Copyright 2010 Lennart Poettering
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
13 (at your option) any later version.
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24 <refentry id="systemd.exec">
26 <title>systemd.exec</title>
27 <productname>systemd</productname>
31 <contrib>Developer</contrib>
32 <firstname>Lennart</firstname>
33 <surname>Poettering</surname>
34 <email>lennart@poettering.net</email>
40 <refentrytitle>systemd.exec</refentrytitle>
41 <manvolnum>5</manvolnum>
45 <refname>systemd.exec</refname>
46 <refpurpose>Execution environment configuration</refpurpose>
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>
57 <title>Description</title>
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>
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
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>,
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
82 <title>Options</title>
84 <variablelist class='unit-directives'>
87 <term><varname>WorkingDirectory=</varname></term>
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>
100 <term><varname>RootDirectory=</varname></term>
102 <listitem><para>Takes an absolute
103 directory path. Sets the root
104 directory for executed processes, with
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>
115 <term><varname>User=</varname></term>
116 <term><varname>Group=</varname></term>
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>
127 <term><varname>SupplementaryGroups=</varname></term>
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
144 user.</para></listitem>
148 <term><varname>Nice=</varname></term>
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>
160 <term><varname>OOMScoreAdjust=</varname></term>
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>
174 <term><varname>IOSchedulingClass=</varname></term>
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>
188 <term><varname>IOSchedulingPriority=</varname></term>
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
197 <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
198 for details.</para></listitem>
202 <term><varname>CPUSchedulingPolicy=</varname></term>
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>
217 <term><varname>CPUSchedulingPriority=</varname></term>
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>
233 <term><varname>CPUSchedulingResetOnFork=</varname></term>
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>
246 <term><varname>CPUAffinity=</varname></term>
248 <listitem><para>Controls the CPU
249 affinity of the executed
250 processes. Takes a space-separated
251 list of CPU indices. 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
258 <citerefentry><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry>
259 for details.</para></listitem>
263 <term><varname>UMask=</varname></term>
265 <listitem><para>Controls the file mode
266 creation mask. Takes an access mode in
268 <citerefentry><refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum></citerefentry>
269 for details. Defaults to
270 0022.</para></listitem>
274 <term><varname>Environment=</varname></term>
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
293 If you need to assign a value containing spaces
294 to a variable, use double quotes (")
295 for the assignment.</para>
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>.
307 <citerefentry><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
308 for details about environment variables.</para></listitem>
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>
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
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
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>
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
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
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
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
392 <option>socket</option> option is only
393 valid in socket-activated services,
394 and only when the socket configuration
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
404 <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
405 daemon. This setting defaults to
406 <option>null</option>.</para></listitem>
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>
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
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
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
466 <option>DefaultStandardOutput=</option>
468 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
470 <option>journal</option>.</para></listitem>
473 <term><varname>StandardError=</varname></term>
474 <listitem><para>Controls where file
475 descriptor 2 (STDERR) of the
476 executed processes is connected to.
477 The available options are identical to
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>
487 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
489 <option>inherit</option>.</para></listitem>
492 <term><varname>TTYPath=</varname></term>
493 <listitem><para>Sets the terminal
494 device node to use if standard input, output,
495 or error are connected to a
496 TTY (see above). Defaults to
497 <filename>/dev/console</filename>.</para></listitem>
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>
508 <term><varname>TTYVHangup=</varname></term>
509 <listitem><para>Disconnect all clients
510 which have opened the terminal device
512 <varname>TTYPath=</varname>
513 before and after execution. Defaults
515 <literal>no</literal>.</para></listitem>
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
527 <literal>no</literal>.</para></listitem>
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
537 <varname>StandardOutput=</varname> or
538 <varname>StandardError=</varname> are
539 set to <option>syslog</option> or
540 <option>kmsg</option>.</para></listitem>
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
569 <varname>StandardOutput=</varname> or
570 <varname>StandardError=</varname> are
571 set to <option>syslog</option>.
573 <option>daemon</option>.</para></listitem>
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
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>.
606 <option>info</option>.</para></listitem>
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>
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
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
644 too.</para></listitem>
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
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>
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>
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
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
710 <citerefentry><refentrytitle>hosts_options</refentrytitle><manvolnum>5</manvolnum></citerefentry>
711 are not supported.</para></listitem>
715 <term><varname>CapabilityBoundingSet=</varname></term>
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
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>
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
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
790 <varname>CapabilityBoundingSet=</varname>
791 is probably the much more useful
792 setting.</para></listitem>
796 <term><varname>ReadWriteDirectories=</varname></term>
797 <term><varname>ReadOnlyDirectories=</varname></term>
798 <term><varname>InaccessibleDirectories=</varname></term>
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
834 <varname>ReadOnlyDirectories=</varname>
836 <varname>InaccessibleDirectories=</varname>
838 <literal>-</literal>, in which case
839 they will be ignored when they do not
840 exist.</para></listitem>
844 <term><varname>PrivateTmp=</varname></term>
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
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>
870 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
871 for details.</para></listitem>
875 <term><varname>PrivateNetwork=</varname></term>
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>
893 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
894 for details.</para></listitem>
898 <term><varname>PrivateDevices=</varname></term>
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
912 false.</para></listitem>
916 <term><varname>MountFlags=</varname></term>
918 <listitem><para>Takes a mount
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
927 <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>2</manvolnum></citerefentry>
928 for details. Default to
929 <option>shared</option>.</para></listitem>
933 <term><varname>UtmpIdentifier=</varname></term>
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>
954 <term><varname>SELinuxContext=</varname></term>
956 <listitem><para>Set the SELinux
957 security context of the executed
958 process. If set, this will override
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
966 <citerefentry><refentrytitle>setexeccon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
967 for details.</para></listitem>
971 <term><varname>AppArmorProfile=</varname></term>
973 <listitem><para>Take a profile name as argument.
974 The process executed by the unit will switch to
975 this profile when started. Profiles must already
976 be loaded in the kernel, or the unit will fail.
977 This result in a non operation if AppArmor is not
978 enabled. If prefixed by <literal>-</literal>, all errors
984 <term><varname>IgnoreSIGPIPE=</varname></term>
986 <listitem><para>Takes a boolean
987 argument. If true, causes <constant>SIGPIPE</constant> to be
988 ignored in the executed
989 process. Defaults to true because
990 <constant>SIGPIPE</constant> generally is useful only in
991 shell pipelines.</para></listitem>
995 <term><varname>NoNewPrivileges=</varname></term>
997 <listitem><para>Takes a boolean
998 argument. If true, ensures that the
999 service process and all its children
1000 can never gain new privileges. This
1001 option is more powerful than the respective
1002 secure bits flags (see above), as it
1003 also prohibits UID changes of any
1004 kind. This is the simplest, most
1005 effective way to ensure that a process
1006 and its children can never elevate
1007 privileges again.</para></listitem>
1011 <term><varname>SystemCallFilter=</varname></term>
1013 <listitem><para>Takes a
1014 space-separated list of system call
1015 names. If this setting is used, all
1016 system calls executed by the unit
1017 processes except for the listed ones
1018 will result in immediate process
1019 termination with the
1020 <constant>SIGSYS</constant> signal
1021 (whitelisting). If the first character
1022 of the list is <literal>~</literal>,
1023 the effect is inverted: only the
1024 listed system calls will result in
1025 immediate process termination
1026 (blacklisting). If running in user
1027 mode and this option is used,
1028 <varname>NoNewPrivileges=yes</varname>
1029 is implied. This feature makes use of the
1030 Secure Computing Mode 2 interfaces of
1031 the kernel ('seccomp filtering') and
1032 is useful for enforcing a minimal
1033 sandboxing environment. Note that the
1034 <function>execve</function>,
1035 <function>rt_sigreturn</function>,
1036 <function>sigreturn</function>,
1037 <function>exit_group</function>,
1038 <function>exit</function> system calls
1039 are implicitly whitelisted and do not
1040 need to be listed explicitly. This
1041 option may be specified more than once
1042 in which case the filter masks are
1043 merged. If the empty string is
1044 assigned, the filter is reset, all
1045 prior assignments will have no
1048 <para>If you specify both types of
1049 this option (i.e. whitelisting and
1050 blacklisting), the first encountered
1051 will take precedence and will dictate
1052 the default action (termination or
1053 approval of a system call). Then the
1054 next occurrences of this option will
1055 add or delete the listed system calls
1056 from the set of the filtered system
1057 calls, depending of its type and the
1058 default action. (For example, if you have started
1059 with a whitelisting of
1060 <function>read</function> and
1061 <function>write</function>, and right
1062 after it add a blacklisting of
1063 <function>write</function>, then
1064 <function>write</function> will be
1065 removed from the set.)
1070 <term><varname>SystemCallErrorNumber=</varname></term>
1072 <listitem><para>Takes an
1073 <literal>errno</literal> error number
1074 name to return when the system call
1075 filter configured with
1076 <varname>SystemCallFilter=</varname>
1077 is triggered, instead of terminating
1078 the process immediately. Takes an
1080 <constant>EPERM</constant>,
1081 <constant>EACCES</constant> or
1082 <constant>EUCLEAN</constant>. When this
1083 setting is not used, or when the empty
1084 string is assigned, the process will be
1085 terminated immediately when the filter
1086 is triggered.</para></listitem>
1090 <term><varname>SystemCallArchitectures=</varname></term>
1092 <listitem><para>Takes a space
1093 separated list of architecture
1094 identifiers to include in the system
1095 call filter. The known architecture
1097 <constant>x86</constant>,
1098 <constant>x86-64</constant>,
1099 <constant>x32</constant>,
1100 <constant>arm</constant> as well as
1101 the special identifier
1102 <constant>native</constant>. Only
1103 system calls of the specified
1104 architectures will be permitted to
1105 processes of this unit. This is an
1106 effective way to disable compatibility
1107 with non-native architectures for
1108 processes, for example to prohibit
1109 execution of 32-bit x86 binaries on
1110 64-bit x86-64 systems. The special
1111 <constant>native</constant> identifier
1112 implicitly maps to the native
1113 architecture of the system (or more
1114 strictly: to the architecture the
1115 system manager is compiled for). If
1116 running in user mode and this option
1118 <varname>NoNewPrivileges=yes</varname>
1119 is implied. Note that setting this
1120 option to a non-empty list implies
1121 that <constant>native</constant> is
1122 included too. By default, this option
1123 is set to the empty list, i.e. no
1124 architecture system call filtering is
1125 applied.</para></listitem>
1129 <term><varname>RestrictAddressFamilies=</varname></term>
1131 <listitem><para>Restricts the set of
1132 socket address families accessible to
1133 the processes of this unit. Takes a
1134 space-separated list of address family
1135 names to whitelist, such as
1136 <constant>AF_UNIX</constant>,
1137 <constant>AF_INET</constant> or
1138 <constant>AF_INET6</constant>. When
1139 prefixed with <constant>~</constant>
1140 the listed address families will be
1141 applied as blacklist, otherwise as
1142 whitelist. Note that this restricts
1144 <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>2</manvolnum></citerefentry>
1145 system call only. Sockets passed into
1146 the process by other means (for
1147 example, by using socket activation
1148 with socket units, see
1149 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
1150 are unaffected. Also, sockets created
1151 with <function>socketpair()</function>
1152 (which creates connected AF_UNIX
1153 sockets only) are unaffected. Note
1154 that this option has no effect on
1155 32bit x86 and is ignored (but works
1156 correctly on x86-64). If running in user
1157 mode and this option is used,
1158 <varname>NoNewPrivileges=yes</varname>
1159 is implied. By default no
1160 restriction applies, all address
1161 families are accessible to
1162 processes. If assigned the empty
1163 string any previous list changes are
1166 <para>Use this option to limit
1167 exposure of processes to remote
1168 systems, in particular via exotic
1169 network protocols. Note that in most
1171 <constant>AF_UNIX</constant> address
1172 family should be included in the
1173 configured whitelist as it is
1174 frequently used for local
1175 communication, including for
1176 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>2</manvolnum></citerefentry>
1177 logging.</para></listitem>
1181 <term><varname>Personality=</varname></term>
1183 <listitem><para>Controls which
1185 <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
1186 shall report, when invoked by unit
1187 processes. Takes one of
1188 <constant>x86</constant> and
1189 <constant>x86-64</constant>. This is
1190 useful when running 32bit services on
1191 a 64bit host system. If not specified
1192 the personality is left unmodified and
1193 thus reflects the personality of the
1195 kernel.</para></listitem>
1199 <term><varname>RuntimeDirectory=</varname></term>
1200 <term><varname>RuntimeDirectoryMode=</varname></term>
1202 <listitem><para>Takes a list of
1203 directory names. If set one or more
1204 directories by the specified names
1205 will be created below
1206 <filename>/run</filename> (for system
1208 <varname>$XDG_RUNTIME_DIR</varname>
1209 (for user services) when the unit is
1210 started and removed when the unit is
1211 stopped. The directories will have the
1212 access mode specified in
1213 <varname>RuntimeDirectoryMode=</varname>,
1214 and will be owned by the user and
1216 <varname>User=</varname> and
1217 <varname>Group=</varname>. Use this to
1218 manage one or more runtime directories
1219 of the unit and bind their lifetime to
1220 the daemon runtime. The specified
1221 directory names must be relative, and
1223 <literal>/</literal>, i.e. must refer
1224 to simple directories to create or
1225 remove. This is particularly useful
1226 for unpriviliges daemons that cannot
1227 create runtime directories in
1228 <filename>/run</filename> due to lack
1229 of privileges, and to make sure the
1230 runtime directory is cleaned up
1231 automatically after use. For runtime
1232 directories that require more complex
1233 or different configuration or lifetime
1234 guarantees, please consider using
1235 <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
1242 <title>Environment variables in spawned processes</title>
1244 <para>Processes started by the system are executed in
1245 a clean environment in which select variables
1246 listed below are set. System processes started by systemd
1247 do not inherit variables from PID 1, but processes
1248 started by user systemd instances inherit all
1249 environment variables from the user systemd instance.
1252 <variablelist class='environment-variables'>
1254 <term><varname>$PATH</varname></term>
1256 <listitem><para>Colon-separated list
1257 of directiories to use when launching
1258 executables. Systemd uses a fixed
1260 <filename>/usr/local/sbin</filename>:<filename>/usr/local/bin</filename>:<filename>/usr/sbin</filename>:<filename>/usr/bin</filename>:<filename>/sbin</filename>:<filename>/bin</filename>.
1265 <term><varname>$LANG</varname></term>
1267 <listitem><para>Locale. Can be set in
1268 <citerefentry><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1269 or on the kernel command line (see
1270 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1272 <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>).
1277 <term><varname>$USER</varname></term>
1278 <term><varname>$LOGNAME</varname></term>
1279 <term><varname>$HOME</varname></term>
1280 <term><varname>$SHELL</varname></term>
1282 <listitem><para>User name (twice), home
1283 directory, and the login shell.
1284 The variables are set for the units that
1285 have <varname>User=</varname> set,
1287 <command>systemd</command> instances.
1289 <citerefentry><refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1294 <term><varname>$XDG_RUNTIME_DIR</varname></term>
1296 <listitem><para>The directory for volatile
1297 state. Set for the user <command>systemd</command>
1298 instance, and also in user sessions.
1300 <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
1305 <term><varname>$XDG_SESSION_ID</varname></term>
1306 <term><varname>$XDG_SEAT</varname></term>
1307 <term><varname>$XDG_VTNR</varname></term>
1309 <listitem><para>The identifier of the
1310 session, the seat name, and
1311 virtual terminal of the session. Set
1313 <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1315 <varname>$XDG_SEAT</varname> and
1316 <varname>$XDG_VTNR</varname> will
1317 only be set when attached to a seat and a
1318 tty.</para></listitem>
1322 <term><varname>$MAINPID</varname></term>
1324 <listitem><para>The PID of the units
1325 main process if it is known. This is
1326 only set for control processes as
1328 <varname>ExecReload=</varname> and
1329 similar. </para></listitem>
1333 <term><varname>$MANAGERPID</varname></term>
1335 <listitem><para>The PID of the user
1336 <command>systemd</command> instance,
1337 set for processes spawned by it.
1342 <term><varname>$LISTEN_FDS</varname></term>
1343 <term><varname>$LISTEN_PID</varname></term>
1345 <listitem><para>Information about file
1346 descriptors passed to a service for
1347 socket activation. See
1348 <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
1353 <term><varname>$TERM</varname></term>
1355 <listitem><para>Terminal type, set
1356 only for units connected to a terminal
1357 (<varname>StandardInput=tty</varname>,
1358 <varname>StandardOutput=tty</varname>,
1360 <varname>StandardError=tty</varname>).
1362 <citerefentry><refentrytitle>termcap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1367 <para>Additional variables may be configured by the
1368 following means: for processes spawned in specific
1369 units, use the <varname>Environment=</varname> and
1370 <varname>EnvironmentFile=</varname> options above; to
1371 specify variables globally, use
1372 <varname>DefaultEnvironment=</varname> (see
1373 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
1374 or the kernel option
1375 <varname>systemd.setenv=</varname> (see
1376 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>). Additional
1377 variables may also be set through PAM,
1378 c.f. <citerefentry><refentrytitle>pam_env</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
1382 <title>See Also</title>
1384 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1385 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1386 <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1387 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1388 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1389 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1390 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1391 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1392 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1393 <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1394 <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1395 <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1396 <citerefentry><refentrytitle>exec</refentrytitle><manvolnum>3</manvolnum></citerefentry>