summaryrefslogtreecommitdiff
path: root/man/systemd.exec.xml
blob: b49fc21cc5911341429d54c8f35dc078cc815c04 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->

<refentry id="systemd.exec">
  <refentryinfo>
    <title>systemd.exec</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>Lennart</firstname>
        <surname>Poettering</surname>
        <email>lennart@poettering.net</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd.exec</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd.exec</refname>
    <refpurpose>Execution environment configuration</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename><replaceable>service</replaceable>.service</filename>,
    <filename><replaceable>socket</replaceable>.socket</filename>,
    <filename><replaceable>mount</replaceable>.mount</filename>,
    <filename><replaceable>swap</replaceable>.swap</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>Unit configuration files for services, sockets, mount
    points, and swap devices share a subset of configuration options
    which define the execution environment of spawned
    processes.</para>

    <para>This man page lists the configuration options shared by
    these four unit types. See
    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for the common options of all unit configuration files, and
    <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    and
    <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for more information on the specific unit configuration files. The
    execution specific configuration options are configured in the
    [Service], [Socket], [Mount], or [Swap] sections, depending on the
    unit type.</para>
  </refsect1>

  <refsect1>
    <title>Options</title>

    <variablelist class='unit-directives'>

      <varlistentry>
        <term><varname>WorkingDirectory=</varname></term>

        <listitem><para>Takes an absolute directory path, or the
        special value <literal>~</literal>. Sets the working directory
        for executed processes. If set to <literal>~</literal>, the
        home directory of the user specified in
        <varname>User=</varname> is used. If not set, defaults to the
        root directory when systemd is running as a system instance
        and the respective user's home directory if run as user. If
        the setting is prefixed with the <literal>-</literal>
        character, a missing working directory is not considered
        fatal.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>RootDirectory=</varname></term>

        <listitem><para>Takes an absolute directory path. Sets the
        root directory for executed processes, with the <citerefentry
        project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        system call. If this is used, it must be ensured that the
        process binary and all its auxiliary files are available in
        the <function>chroot()</function> jail.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>User=</varname></term>
        <term><varname>Group=</varname></term>

        <listitem><para>Sets the Unix user or group that the processes
        are executed as, respectively. Takes a single user or group
        name or ID as argument. If no group is set, the default group
        of the user is chosen.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SupplementaryGroups=</varname></term>

        <listitem><para>Sets the supplementary Unix groups the
        processes are executed as. This takes a space-separated list
        of group names or IDs. This option may be specified more than
        once, in which case all listed groups are set as supplementary
        groups. When the empty string is assigned, the list of
        supplementary groups is reset, and all assignments prior to
        this one will have no effect. In any way, this option does not
        override, but extends the list of supplementary groups
        configured in the system group database for the
        user.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Nice=</varname></term>

        <listitem><para>Sets the default nice level (scheduling
        priority) for executed processes. Takes an integer between -20
        (highest priority) and 19 (lowest priority). See
        <citerefentry><refentrytitle>setpriority</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>OOMScoreAdjust=</varname></term>

        <listitem><para>Sets the adjustment level for the
        Out-Of-Memory killer for executed processes. Takes an integer
        between -1000 (to disable OOM killing for this process) and
        1000 (to make killing of this process under memory pressure
        very likely). See <ulink
        url="https://www.kernel.org/doc/Documentation/filesystems/proc.txt">proc.txt</ulink>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>IOSchedulingClass=</varname></term>

        <listitem><para>Sets the I/O scheduling class for executed
        processes. Takes an integer between 0 and 3 or one of the
        strings <option>none</option>, <option>realtime</option>,
        <option>best-effort</option> or <option>idle</option>. See
        <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>IOSchedulingPriority=</varname></term>

        <listitem><para>Sets the I/O scheduling priority for executed
        processes. Takes an integer between 0 (highest priority) and 7
        (lowest priority). The available priorities depend on the
        selected I/O scheduling class (see above). See
        <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>CPUSchedulingPolicy=</varname></term>

        <listitem><para>Sets the CPU scheduling policy for executed
        processes. Takes one of
        <option>other</option>,
        <option>batch</option>,
        <option>idle</option>,
        <option>fifo</option> or
        <option>rr</option>. See
        <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>CPUSchedulingPriority=</varname></term>

        <listitem><para>Sets the CPU scheduling priority for executed
        processes. The available priority range depends on the
        selected CPU scheduling policy (see above). For real-time
        scheduling policies an integer between 1 (lowest priority) and
        99 (highest priority) can be used. See
        <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for details. </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>CPUSchedulingResetOnFork=</varname></term>

        <listitem><para>Takes a boolean argument. If true, elevated
        CPU scheduling priorities and policies will be reset when the
        executed processes fork, and can hence not leak into child
        processes. See
        <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for details. Defaults to false.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>CPUAffinity=</varname></term>

        <listitem><para>Controls the CPU affinity of the executed
        processes. Takes a list of CPU indices or ranges separated by
        either whitespace or commas. CPU ranges are specified by the
        lower and upper CPU indices separated by a dash.
        This option may be specified more than once, in which case the
        specified CPU affinity masks are merged. If the empty string
        is assigned, the mask is reset, all assignments prior to this
        will have no effect. See
        <citerefentry><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>UMask=</varname></term>

        <listitem><para>Controls the file mode creation mask. Takes an
        access mode in octal notation. See
        <citerefentry><refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for details. Defaults to 0022.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Environment=</varname></term>

        <listitem><para>Sets environment variables for executed
        processes. Takes a space-separated list of variable
        assignments. This option may be specified more than once, in
        which case all listed variables will be set. If the same
        variable is set twice, the later setting will override the
        earlier setting. If the empty string is assigned to this
        option, the list of environment variables is reset, all prior
        assignments have no effect. Variable expansion is not
        performed inside the strings, however, specifier expansion is
        possible. The $ character has no special meaning. If you need
        to assign a value containing spaces to a variable, use double
        quotes (") for the assignment.</para>

        <para>Example:
        <programlisting>Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"</programlisting>
        gives three variables <literal>VAR1</literal>,
        <literal>VAR2</literal>, <literal>VAR3</literal>
        with the values <literal>word1 word2</literal>,
        <literal>word3</literal>, <literal>$word 5 6</literal>.
        </para>

        <para>
        See
        <citerefentry project='man-pages'><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
        for details about environment variables.</para></listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>EnvironmentFile=</varname></term>
        <listitem><para>Similar to <varname>Environment=</varname> but
        reads the environment variables from a text file. The text
        file should contain new-line-separated variable assignments.
        Empty lines, lines without an <literal>=</literal> separator,
        or lines starting with ; or # will be ignored,
        which may be used for commenting. A line ending with a
        backslash will be concatenated with the following one,
        allowing multiline variable definitions. The parser strips
        leading and trailing whitespace from the values of
        assignments, unless you use double quotes (").</para>

        <para>The argument passed should be an absolute filename or
        wildcard expression, optionally prefixed with
        <literal>-</literal>, which indicates that if the file does
        not exist, it will not be read and no error or warning message
        is logged. This option may be specified more than once in
        which case all specified files are read. If the empty string
        is assigned to this option, the list of file to read is reset,
        all prior assignments have no effect.</para>

        <para>The files listed with this directive will be read
        shortly before the process is executed (more specifically,
        after all processes from a previous unit state terminated.
        This means you can generate these files in one unit state, and
        read it with this option in the next).</para>

        <para>Settings from these
        files override settings made with
        <varname>Environment=</varname>. If the same variable is set
        twice from these files, the files will be read in the order
        they are specified and the later setting will override the
        earlier setting.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>StandardInput=</varname></term>
        <listitem><para>Controls where file descriptor 0 (STDIN) of
        the executed processes is connected to. Takes one of
        <option>null</option>,
        <option>tty</option>,
        <option>tty-force</option>,
        <option>tty-fail</option> or
        <option>socket</option>.</para>

        <para>If <option>null</option> is selected, standard input
        will be connected to <filename>/dev/null</filename>, i.e. all
        read attempts by the process will result in immediate
        EOF.</para>

        <para>If <option>tty</option> is selected, standard input is
        connected to a TTY (as configured by
        <varname>TTYPath=</varname>, see below) and the executed
        process becomes the controlling process of the terminal. If
        the terminal is already being controlled by another process,
        the executed process waits until the current controlling
        process releases the terminal.</para>

        <para><option>tty-force</option> is similar to
        <option>tty</option>, but the executed process is forcefully
        and immediately made the controlling process of the terminal,
        potentially removing previous controlling processes from the
        terminal.</para>

        <para><option>tty-fail</option> is similar to
        <option>tty</option> but if the terminal already has a
        controlling process start-up of the executed process
        fails.</para>

        <para>The <option>socket</option> option is only valid in
        socket-activated services, and only when the socket
        configuration file (see
        <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for details) specifies a single socket only. If this option is
        set, standard input will be connected to the socket the
        service was activated from, which is primarily useful for
        compatibility with daemons designed for use with the
        traditional
        <citerefentry project='freebsd'><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        daemon.</para>

        <para>This setting defaults to
        <option>null</option>.</para></listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>StandardOutput=</varname></term>
        <listitem><para>Controls where file descriptor 1 (STDOUT) of
        the executed processes is connected to. Takes one of
        <option>inherit</option>,
        <option>null</option>,
        <option>tty</option>,
        <option>journal</option>,
        <option>syslog</option>,
        <option>kmsg</option>,
        <option>journal+console</option>,
        <option>syslog+console</option>,
        <option>kmsg+console</option> or
        <option>socket</option>.</para>

        <para><option>inherit</option> duplicates the file descriptor
        of standard input for standard output.</para>

        <para><option>null</option> connects standard output to
        <filename>/dev/null</filename>, i.e. everything written to it
        will be lost.</para>

        <para><option>tty</option> connects standard output to a tty
        (as configured via <varname>TTYPath=</varname>, see below). If
        the TTY is used for output only, the executed process will not
        become the controlling process of the terminal, and will not
        fail or wait for other processes to release the
        terminal.</para>

        <para><option>journal</option> connects standard output with
        the journal which is accessible via
        <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
        Note that everything that is written to syslog or kmsg (see
        below) is implicitly stored in the journal as well, the
        specific two options listed below are hence supersets of this
        one.</para>

        <para><option>syslog</option> connects standard output to the
        <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
        system syslog service, in addition to the journal. Note that
        the journal daemon is usually configured to forward everything
        it receives to syslog anyway, in which case this option is no
        different from <option>journal</option>.</para>

        <para><option>kmsg</option> connects standard output with the
        kernel log buffer which is accessible via
        <citerefentry project='man-pages'><refentrytitle>dmesg</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        in addition to the journal. The journal daemon might be
        configured to send all logs to kmsg anyway, in which case this
        option is no different from <option>journal</option>.</para>

        <para><option>journal+console</option>,
        <option>syslog+console</option> and
        <option>kmsg+console</option> work in a similar way as the
        three options above but copy the output to the system console
        as well.</para>

        <para><option>socket</option> connects standard output to a
        socket acquired via socket activation. The semantics are
        similar to the same option of
        <varname>StandardInput=</varname>.</para>

        <para>This setting defaults to the value set with
        <option>DefaultStandardOutput=</option> in
        <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        which defaults to <option>journal</option>.</para></listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>StandardError=</varname></term>
        <listitem><para>Controls where file descriptor 2 (STDERR) of
        the executed processes is connected to. The available options
        are identical to those of <varname>StandardOutput=</varname>,
        with one exception: if set to <option>inherit</option> the
        file descriptor used for standard output is duplicated for
        standard error. This setting defaults to the value set with
        <option>DefaultStandardError=</option> in
        <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        which defaults to <option>inherit</option>.</para></listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>TTYPath=</varname></term>
        <listitem><para>Sets the terminal device node to use if
        standard input, output, or error are connected to a TTY (see
        above). Defaults to
        <filename>/dev/console</filename>.</para></listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>TTYReset=</varname></term>
        <listitem><para>Reset the terminal device specified with
        <varname>TTYPath=</varname> before and after execution.
        Defaults to <literal>no</literal>.</para></listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>TTYVHangup=</varname></term>
        <listitem><para>Disconnect all clients which have opened the
        terminal device specified with <varname>TTYPath=</varname>
        before and after execution. Defaults to
        <literal>no</literal>.</para></listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>TTYVTDisallocate=</varname></term>
        <listitem><para>If the terminal device specified with
        <varname>TTYPath=</varname> is a virtual console terminal, try
        to deallocate the TTY before and after execution. This ensures
        that the screen and scrollback buffer is cleared. Defaults to
        <literal>no</literal>.</para></listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>SyslogIdentifier=</varname></term>
        <listitem><para>Sets the process name to prefix log lines sent
        to the logging system or the kernel log buffer with. If not
        set, defaults to the process name of the executed process.
        This option is only useful when
        <varname>StandardOutput=</varname> or
        <varname>StandardError=</varname> are set to
        <option>syslog</option>, <option>journal</option> or
        <option>kmsg</option> (or to the same settings in combination
        with <option>+console</option>).</para></listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>SyslogFacility=</varname></term>
        <listitem><para>Sets the syslog facility to use when logging
        to syslog. One of <option>kern</option>,
        <option>user</option>, <option>mail</option>,
        <option>daemon</option>, <option>auth</option>,
        <option>syslog</option>, <option>lpr</option>,
        <option>news</option>, <option>uucp</option>,
        <option>cron</option>, <option>authpriv</option>,
        <option>ftp</option>, <option>local0</option>,
        <option>local1</option>, <option>local2</option>,
        <option>local3</option>, <option>local4</option>,
        <option>local5</option>, <option>local6</option> or
        <option>local7</option>. See
        <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
        for details. This option is only useful when
        <varname>StandardOutput=</varname> or
        <varname>StandardError=</varname> are set to
        <option>syslog</option>. Defaults to
        <option>daemon</option>.</para></listitem>
      </varlistentry>
      <varlistentry>
        <term><varname>SyslogLevel=</varname></term>
        <listitem><para>The default syslog level to use when logging to
        syslog or the kernel log buffer. One of
        <option>emerg</option>,
        <option>alert</option>,
        <option>crit</option>,
        <option>err</option>,
        <option>warning</option>,
        <option>notice</option>,
        <option>info</option>,
        <option>debug</option>. See
        <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
        for details. This option is only useful when
        <varname>StandardOutput=</varname> or
        <varname>StandardError=</varname> are set to
        <option>syslog</option> or <option>kmsg</option>. Note that
        individual lines output by the daemon might be prefixed with a
        different log level which can be used to override the default
        log level specified here. The interpretation of these prefixes
        may be disabled with <varname>SyslogLevelPrefix=</varname>,
        see below. For details, see
        <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.

        Defaults to
        <option>info</option>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SyslogLevelPrefix=</varname></term>
        <listitem><para>Takes a boolean argument. If true and
        <varname>StandardOutput=</varname> or
        <varname>StandardError=</varname> are set to
        <option>syslog</option>, <option>kmsg</option> or
        <option>journal</option>, log lines written by the executed
        process that are prefixed with a log level will be passed on
        to syslog with this log level set but the prefix removed. If
        set to false, the interpretation of these prefixes is disabled
        and the logged lines are passed on as-is. For details about
        this prefixing see
        <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
        Defaults to true.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>TimerSlackNSec=</varname></term>
        <listitem><para>Sets the timer slack in nanoseconds for the
        executed processes. The timer slack controls the accuracy of
        wake-ups triggered by timers. See
        <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for more information. Note that in contrast to most other time
        span definitions this parameter takes an integer value in
        nano-seconds if no unit is specified. The usual time units are
        understood too.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>LimitCPU=</varname></term>
        <term><varname>LimitFSIZE=</varname></term>
        <term><varname>LimitDATA=</varname></term>
        <term><varname>LimitSTACK=</varname></term>
        <term><varname>LimitCORE=</varname></term>
        <term><varname>LimitRSS=</varname></term>
        <term><varname>LimitNOFILE=</varname></term>
        <term><varname>LimitAS=</varname></term>
        <term><varname>LimitNPROC=</varname></term>
        <term><varname>LimitMEMLOCK=</varname></term>
        <term><varname>LimitLOCKS=</varname></term>
        <term><varname>LimitSIGPENDING=</varname></term>
        <term><varname>LimitMSGQUEUE=</varname></term>
        <term><varname>LimitNICE=</varname></term>
        <term><varname>LimitRTPRIO=</varname></term>
        <term><varname>LimitRTTIME=</varname></term>
        <listitem><para>These settings set both soft and hard limits
        of various resources for executed processes. See
        <citerefentry><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for details. Use the string <varname>infinity</varname> to
        configure no limit on a specific resource.</para></listitem>

        <table>
          <title>Limit directives and their equivalent with ulimit</title>

          <tgroup cols='2'>
            <colspec colname='directive' />
            <colspec colname='equivalent' />
            <thead>
              <row>
                <entry>Directive</entry>
                <entry>ulimit equivalent</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>LimitCPU</entry>
                <entry>ulimit -t</entry>
              </row>
              <row>
                <entry>LimitFSIZE</entry>
                <entry>ulimit -f</entry>
              </row>
              <row>
                <entry>LimitDATA</entry>
                <entry>ulimit -d</entry>
              </row>
              <row>
                <entry>LimitSTACK</entry>
                <entry>ulimit -s</entry>
              </row>
              <row>
                <entry>LimitCORE</entry>
                <entry>ulimit -c</entry>
              </row>
              <row>
                <entry>LimitRSS</entry>
                <entry>ulimit -m</entry>
              </row>
              <row>
                <entry>LimitNOFILE</entry>
                <entry>ulimit -n</entry>
              </row>
              <row>
                <entry>LimitAS</entry>
                <entry>ulimit -v</entry>
              </row>
              <row>
                <entry>LimitNPROC</entry>
                <entry>ulimit -u</entry>
              </row>
              <row>
                <entry>LimitMEMLOCK</entry>
                <entry>ulimit -l</entry>
              </row>
              <row>
                <entry>LimitLOCKS</entry>
                <entry>ulimit -x</entry>
              </row>
              <row>
                <entry>LimitSIGPENDING</entry>
                <entry>ulimit -i</entry>
              </row>
              <row>
                <entry>LimitMSGQUEUE</entry>
                <entry>ulimit -q</entry>
              </row>
              <row>
                <entry>LimitNICE</entry>
                <entry>ulimit -e</entry>
              </row>
              <row>
                <entry>LimitRTPRIO</entry>
                <entry>ulimit -r</entry>
              </row>
              <row>
                <entry>LimitRTTIME</entry>
                <entry>No equivalent</entry>
              </row>
            </tbody>
          </tgroup>
        </table>
      </varlistentry>

      <varlistentry>
        <term><varname>PAMName=</varname></term>
        <listitem><para>Sets the PAM service name to set up a session
        as. If set, the executed process will be registered as a PAM
        session under the specified service name. This is only useful
        in conjunction with the <varname>User=</varname> setting. If
        not set, no PAM session will be opened for the executed
        processes. See
        <citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>CapabilityBoundingSet=</varname></term>

        <listitem><para>Controls which capabilities to include in the
        capability bounding set for the executed process. See
        <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
        for details. Takes a whitespace-separated list of capability
        names as read by
        <citerefentry project='mankier'><refentrytitle>cap_from_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
        e.g. <constant>CAP_SYS_ADMIN</constant>,
        <constant>CAP_DAC_OVERRIDE</constant>,
        <constant>CAP_SYS_PTRACE</constant>. Capabilities listed will
        be included in the bounding set, all others are removed. If
        the list of capabilities is prefixed with
        <literal>~</literal>, all but the listed capabilities will be
        included, the effect of the assignment inverted. Note that
        this option also affects the respective capabilities in the
        effective, permitted and inheritable capability sets, on top
        of what <varname>Capabilities=</varname> does. If this option
        is not used, the capability bounding set is not modified on
        process execution, hence no limits on the capabilities of the
        process are enforced. This option may appear more than once, in
        which case the bounding sets are merged. If the empty string
        is assigned to this option, the bounding set is reset to the
        empty capability set, and all prior settings have no effect.
        If set to <literal>~</literal> (without any further argument),
        the bounding set is reset to the full set of available
        capabilities, also undoing any previous
        settings.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SecureBits=</varname></term>
        <listitem><para>Controls the secure bits set for the executed
        process. Takes a space-separated combination of options from
        the following list:
        <option>keep-caps</option>,
        <option>keep-caps-locked</option>,
        <option>no-setuid-fixup</option>,
        <option>no-setuid-fixup-locked</option>,
        <option>noroot</option>, and
        <option>noroot-locked</option>.
        This option may appear more than once, in which case the secure
        bits are ORed. If the empty string is assigned to this option,
        the bits are reset to 0. See
        <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Capabilities=</varname></term>
        <listitem><para>Controls the
        <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
        set for the executed process. Take a capability string
        describing the effective, permitted and inherited capability
        sets as documented in
        <citerefentry project='mankier'><refentrytitle>cap_from_text</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
        Note that these capability sets are usually influenced (and
        filtered) by the capabilities attached to the executed file.
        Due to that <varname>CapabilityBoundingSet=</varname> is
        probably a much more useful setting.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ReadWriteDirectories=</varname></term>
        <term><varname>ReadOnlyDirectories=</varname></term>
        <term><varname>InaccessibleDirectories=</varname></term>

        <listitem><para>Sets up a new file system namespace for
        executed processes. These options may be used to limit access
        a process might have to the main file system hierarchy. Each
        setting takes a space-separated list of absolute directory
        paths. Directories listed in
        <varname>ReadWriteDirectories=</varname> are accessible from
        within the namespace with the same access rights as from
        outside. Directories listed in
        <varname>ReadOnlyDirectories=</varname> are accessible for
        reading only, writing will be refused even if the usual file
        access controls would permit this. Directories listed in
        <varname>InaccessibleDirectories=</varname> will be made
        inaccessible for processes inside the namespace. Note that
        restricting access with these options does not extend to
        submounts of a directory that are created later on. These
        options may be specified more than once, in which case all
        directories listed will have limited access from within the
        namespace. If the empty string is assigned to this option, the
        specific list is reset, and all prior assignments have no
        effect.</para>
        <para>Paths in
        <varname>ReadOnlyDirectories=</varname>
        and
        <varname>InaccessibleDirectories=</varname>
        may be prefixed with
        <literal>-</literal>, in which case
        they will be ignored when they do not
        exist. Note that using this
        setting will disconnect propagation of
        mounts from the service to the host
        (propagation in the opposite direction
        continues to work). This means that
        this setting may not be used for
        services which shall be able to
        install mount points in the main mount
        namespace.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>PrivateTmp=</varname></term>

        <listitem><para>Takes a boolean argument. If true, sets up a
        new file system namespace for the executed processes and
        mounts private <filename>/tmp</filename> and
        <filename>/var/tmp</filename> directories inside it that is
        not shared by processes outside of the namespace. This is
        useful to secure access to temporary files of the process, but
        makes sharing between processes via <filename>/tmp</filename>
        or <filename>/var/tmp</filename> impossible. If this is
        enabled, all temporary files created by a service in these
        directories will be removed after the service is stopped.
        Defaults to false. It is possible to run two or more units
        within the same private <filename>/tmp</filename> and
        <filename>/var/tmp</filename> namespace by using the
        <varname>JoinsNamespaceOf=</varname> directive, see
        <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for details. Note that using this setting will disconnect
        propagation of mounts from the service to the host
        (propagation in the opposite direction continues to work).
        This means that this setting may not be used for services
        which shall be able to install mount points in the main mount
        namespace.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>PrivateDevices=</varname></term>

        <listitem><para>Takes a boolean argument. If true, sets up a
        new /dev namespace for the executed processes and only adds
        API pseudo devices such as <filename>/dev/null</filename>,
        <filename>/dev/zero</filename> or
        <filename>/dev/random</filename> (as well as the pseudo TTY
        subsystem) to it, but no physical devices such as
        <filename>/dev/sda</filename>. This is useful to securely turn
        off physical device access by the executed process. Defaults
        to false. Enabling this option will also remove
        <constant>CAP_MKNOD</constant> from the capability bounding
        set for the unit (see above), and set
        <varname>DevicePolicy=closed</varname> (see
        <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for details). Note that using this setting will disconnect
        propagation of mounts from the service to the host
        (propagation in the opposite direction continues to work).
        This means that this setting may not be used for services
        which shall be able to install mount points in the main mount
        namespace.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>PrivateNetwork=</varname></term>

        <listitem><para>Takes a boolean argument. If true, sets up a
        new network namespace for the executed processes and
        configures only the loopback network device
        <literal>lo</literal> inside it. No other network devices will
        be available to the executed process. This is useful to
        securely turn off network access by the executed process.
        Defaults to false. It is possible to run two or more units
        within the same private network namespace by using the
        <varname>JoinsNamespaceOf=</varname> directive, see
        <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for details. Note that this option will disconnect all socket
        families from the host, this includes AF_NETLINK and AF_UNIX.
        The latter has the effect that AF_UNIX sockets in the abstract
        socket namespace will become unavailable to the processes
        (however, those located in the file system will continue to be
        accessible).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ProtectSystem=</varname></term>

        <listitem><para>Takes a boolean argument or
        <literal>full</literal>. If true, mounts the
        <filename>/usr</filename> and <filename>/boot</filename>
        directories read-only for processes invoked by this unit. If
        set to <literal>full</literal>, the <filename>/etc</filename>
        directory is mounted read-only, too. This setting ensures that
        any modification of the vendor-supplied operating system (and
        optionally its configuration) is prohibited for the service.
        It is recommended to enable this setting for all long-running
        services, unless they are involved with system updates or need
        to modify the operating system in other ways. Note however
        that processes retaining the CAP_SYS_ADMIN capability can undo
        the effect of this setting. This setting is hence particularly
        useful for daemons which have this capability removed, for
        example with <varname>CapabilityBoundingSet=</varname>.
        Defaults to off.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ProtectHome=</varname></term>

        <listitem><para>Takes a boolean argument or
        <literal>read-only</literal>. If true, the directories
        <filename>/home</filename>, <filename>/root</filename> and
        <filename>/run/user</filename>
        are made inaccessible and empty for processes invoked by this
        unit. If set to <literal>read-only</literal>, the three
        directories are made read-only instead. It is recommended to
        enable this setting for all long-running services (in
        particular network-facing ones), to ensure they cannot get
        access to private user data, unless the services actually
        require access to the user's private data. Note however that
        processes retaining the CAP_SYS_ADMIN capability can undo the
        effect of this setting. This setting is hence particularly
        useful for daemons which have this capability removed, for
        example with <varname>CapabilityBoundingSet=</varname>.
        Defaults to off.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MountFlags=</varname></term>

        <listitem><para>Takes a mount propagation flag:
        <option>shared</option>, <option>slave</option> or
        <option>private</option>, which control whether mounts in the
        file system namespace set up for this unit's processes will
        receive or propagate mounts or unmounts. See
        <citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        for details. Defaults to <option>shared</option>. Use
        <option>shared</option> to ensure that mounts and unmounts are
        propagated from the host to the container and vice versa. Use
        <option>slave</option> to run processes so that none of their
        mounts and unmounts will propagate to the host. Use
        <option>private</option> to also ensure that no mounts and
        unmounts from the host will propagate into the unit processes'
        namespace. Note that <option>slave</option> means that file
        systems mounted on the host might stay mounted continuously in
        the unit's namespace, and thus keep the device busy. Note that
        the file system namespace related options
        (<varname>PrivateTmp=</varname>,
        <varname>PrivateDevices=</varname>,
        <varname>ProtectSystem=</varname>,
        <varname>ProtectHome=</varname>,
        <varname>ReadOnlyDirectories=</varname>,
        <varname>InaccessibleDirectories=</varname> and
        <varname>ReadWriteDirectories=</varname>) require that mount
        and unmount propagation from the unit's file system namespace
        is disabled, and hence downgrade <option>shared</option> to
        <option>slave</option>. </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>UtmpIdentifier=</varname></term>

        <listitem><para>Takes a four character identifier string for
        an <citerefentry
        project='man-pages'><refentrytitle>utmp</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        and wtmp entry for this service. This should only be
        set for services such as <command>getty</command>
        implementations (such as <citerefentry
        project='die-net'><refentrytitle>agetty</refentrytitle><manvolnum>8</manvolnum></citerefentry>)
        where utmp/wtmp entries must be created and cleared before and
        after execution, or for services that shall be executed as if
        they were run by a <command>getty</command> process (see
        below). If the configured string is longer than four
        characters, it is truncated and the terminal four characters
        are used. This setting interprets %I style string
        replacements. This setting is unset by default, i.e. no
        utmp/wtmp entries are created or cleaned up for this
        service.</para></listitem>
      </varlistentry>

      <varlistentry>
         <term><varname>UtmpMode=</varname></term>

         <listitem><para>Takes one of <literal>init</literal>,
         <literal>login</literal> or <literal>user</literal>. If
         <varname>UtmpIdentifier=</varname> is set, controls which
         type of <citerefentry
         project='man-pages'><refentrytitle>utmp</refentrytitle><manvolnum>5</manvolnum></citerefentry>/wtmp
         entries for this service are generated. This setting has no
         effect unless <varname>UtmpIdentifier=</varname> is set
         too. If <literal>init</literal> is set, only an
         <constant>INIT_PROCESS</constant> entry is generated and the
         invoked process must implement a
         <command>getty</command>-compatible utmp/wtmp logic. If
         <literal>login</literal> is set, first an
         <constant>INIT_PROCESS</constant> entry, followed by a
         <constant>LOGIN_PROCESS</constant> entry is generated. In
         this case, the invoked process must implement a <citerefentry
         project='die-net'><refentrytitle>login</refentrytitle><manvolnum>1</manvolnum></citerefentry>-compatible
         utmp/wtmp logic. If <literal>user</literal> is set, first an
         <constant>INIT_PROCESS</constant> entry, then a
         <constant>LOGIN_PROCESS</constant> entry and finally a
         <constant>USER_PROCESS</constant> entry is generated. In this
         case, the invoked process may be any process that is suitable
         to be run as session leader. Defaults to
         <literal>init</literal>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SELinuxContext=</varname></term>

        <listitem><para>Set the SELinux security context of the
        executed process. If set, this will override the automated
        domain transition. However, the policy still needs to
        authorize the transition. This directive is ignored if SELinux
        is disabled. If prefixed by <literal>-</literal>, all errors
        will be ignored. See
        <citerefentry project='die-net'><refentrytitle>setexeccon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>AppArmorProfile=</varname></term>

        <listitem><para>Takes a profile name as argument. The process
        executed by the unit will switch to this profile when started.
        Profiles must already be loaded in the kernel, or the unit
        will fail. This result in a non operation if AppArmor is not
        enabled. If prefixed by <literal>-</literal>, all errors will
        be ignored. </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SmackProcessLabel=</varname></term>

        <listitem><para>Takes a <option>SMACK64</option> security
        label as argument. The process executed by the unit will be
        started under this label and SMACK will decide whether the
        process is allowed to run or not, based on it. The process
        will continue to run under the label specified here unless the
        executable has its own <option>SMACK64EXEC</option> label, in
        which case the process will transition to run under that
        label. When not specified, the label that systemd is running
        under is used. This directive is ignored if SMACK is
        disabled.</para>

        <para>The value may be prefixed by <literal>-</literal>, in
        which case all errors will be ignored. An empty value may be
        specified to unset previous assignments.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>IgnoreSIGPIPE=</varname></term>

        <listitem><para>Takes a boolean argument. If true, causes
        <constant>SIGPIPE</constant> to be ignored in the executed
        process. Defaults to true because <constant>SIGPIPE</constant>
        generally is useful only in shell pipelines.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>NoNewPrivileges=</varname></term>

        <listitem><para>Takes a boolean argument. If true, ensures
        that the service process and all its children can never gain
        new privileges. This option is more powerful than the
        respective secure bits flags (see above), as it also prohibits
        UID changes of any kind. This is the simplest, most effective
        way to ensure that a process and its children can never
        elevate privileges again.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SystemCallFilter=</varname></term>

        <listitem><para>Takes a space-separated list of system call
        names. If this setting is used, all system calls executed by
        the unit processes except for the listed ones will result in
        immediate process termination with the
        <constant>SIGSYS</constant> signal (whitelisting). If the
        first character of the list is <literal>~</literal>, the
        effect is inverted: only the listed system calls will result
        in immediate process termination (blacklisting). If running in
        user mode and this option is used,
        <varname>NoNewPrivileges=yes</varname> is implied. This
        feature makes use of the Secure Computing Mode 2 interfaces of
        the kernel ('seccomp filtering') and is useful for enforcing a
        minimal sandboxing environment. Note that the
        <function>execve</function>,
        <function>rt_sigreturn</function>,
        <function>sigreturn</function>,
        <function>exit_group</function>, <function>exit</function>
        system calls are implicitly whitelisted and do not need to be
        listed explicitly. This option may be specified more than once,
        in which case the filter masks are merged. If the empty string
        is assigned, the filter is reset, all prior assignments will
        have no effect.</para>

        <para>If you specify both types of this option (i.e.
        whitelisting and blacklisting), the first encountered will
        take precedence and will dictate the default action
        (termination or approval of a system call). Then the next
        occurrences of this option will add or delete the listed
        system calls from the set of the filtered system calls,
        depending of its type and the default action. (For example, if
        you have started with a whitelisting of
        <function>read</function> and <function>write</function>, and
        right after it add a blacklisting of
        <function>write</function>, then <function>write</function>
        will be removed from the set.) </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SystemCallErrorNumber=</varname></term>

        <listitem><para>Takes an <literal>errno</literal> error number
        name to return when the system call filter configured with
        <varname>SystemCallFilter=</varname> is triggered, instead of
        terminating the process immediately. Takes an error name such
        as <constant>EPERM</constant>, <constant>EACCES</constant> or
        <constant>EUCLEAN</constant>. When this setting is not used,
        or when the empty string is assigned, the process will be
        terminated immediately when the filter is
        triggered.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SystemCallArchitectures=</varname></term>

        <listitem><para>Takes a space-separated list of architecture
        identifiers to include in the system call filter. The known
        architecture identifiers are <constant>x86</constant>,
        <constant>x86-64</constant>, <constant>x32</constant>,
        <constant>arm</constant> as well as the special identifier
        <constant>native</constant>. Only system calls of the
        specified architectures will be permitted to processes of this
        unit. This is an effective way to disable compatibility with
        non-native architectures for processes, for example to
        prohibit execution of 32-bit x86 binaries on 64-bit x86-64
        systems. The special <constant>native</constant> identifier
        implicitly maps to the native architecture of the system (or
        more strictly: to the architecture the system manager is
        compiled for). If running in user mode and this option is
        used, <varname>NoNewPrivileges=yes</varname> is implied. Note
        that setting this option to a non-empty list implies that
        <constant>native</constant> is included too. By default, this
        option is set to the empty list, i.e. no architecture system
        call filtering is applied.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>RestrictAddressFamilies=</varname></term>

        <listitem><para>Restricts the set of socket address families
        accessible to the processes of this unit. Takes a
        space-separated list of address family names to whitelist,
        such as
        <constant>AF_UNIX</constant>,
        <constant>AF_INET</constant> or
        <constant>AF_INET6</constant>. When
        prefixed with <constant>~</constant> the listed address
        families will be applied as blacklist, otherwise as whitelist.
        Note that this restricts access to the
        <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        system call only. Sockets passed into the process by other
        means (for example, by using socket activation with socket
        units, see
        <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
        are unaffected. Also, sockets created with
        <function>socketpair()</function> (which creates connected
        AF_UNIX sockets only) are unaffected. Note that this option
        has no effect on 32-bit x86 and is ignored (but works
        correctly on x86-64). If running in user mode and this option
        is used, <varname>NoNewPrivileges=yes</varname> is implied. By
        default, no restriction applies, all address families are
        accessible to processes. If assigned the empty string, any
        previous list changes are undone.</para>

        <para>Use this option to limit exposure of processes to remote
        systems, in particular via exotic network protocols. Note that
        in most cases, the local <constant>AF_UNIX</constant> address
        family should be included in the configured whitelist as it is
        frequently used for local communication, including for
        <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        logging.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Personality=</varname></term>

        <listitem><para>Controls which kernel architecture
        <citerefentry project='man-pages'><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
        shall report, when invoked by unit processes. Takes one of
        <constant>x86</constant> and <constant>x86-64</constant>. This
        is useful when running 32-bit services on a 64-bit host
        system. If not specified, the personality is left unmodified
        and thus reflects the personality of the host system's
        kernel.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>RuntimeDirectory=</varname></term>
        <term><varname>RuntimeDirectoryMode=</varname></term>

        <listitem><para>Takes a list of directory names. If set, one
        or more directories by the specified names will be created
        below <filename>/run</filename> (for system services) or below
        <varname>$XDG_RUNTIME_DIR</varname> (for user services) when
        the unit is started, and removed when the unit is stopped. The
        directories will have the access mode specified in
        <varname>RuntimeDirectoryMode=</varname>, and will be owned by
        the user and group specified in <varname>User=</varname> and
        <varname>Group=</varname>. Use this to manage one or more
        runtime directories of the unit and bind their lifetime to the
        daemon runtime. The specified directory names must be
        relative, and may not include a <literal>/</literal>, i.e.
        must refer to simple directories to create or remove. This is
        particularly useful for unprivileged daemons that cannot
        create runtime directories in <filename>/run</filename> due to
        lack of privileges, and to make sure the runtime directory is
        cleaned up automatically after use. For runtime directories
        that require more complex or different configuration or
        lifetime guarantees, please consider using
        <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
      </varlistentry>

    </variablelist>
  </refsect1>

  <refsect1>
    <title>Environment variables in spawned processes</title>

    <para>Processes started by the system are executed in a clean
    environment in which select variables listed below are set. System
    processes started by systemd do not inherit variables from PID 1,
    but processes started by user systemd instances inherit all
    environment variables from the user systemd instance.
    </para>

    <variablelist class='environment-variables'>
      <varlistentry>
        <term><varname>$PATH</varname></term>

        <listitem><para>Colon-separated list of directories to use
        when launching executables. Systemd uses a fixed value of
        <filename>/usr/local/sbin</filename>:<filename>/usr/local/bin</filename>:<filename>/usr/sbin</filename>:<filename>/usr/bin</filename>:<filename>/sbin</filename>:<filename>/bin</filename>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>$LANG</varname></term>

        <listitem><para>Locale. Can be set in
        <citerefentry project='man-pages'><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        or on the kernel command line (see
        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
        and
        <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>$USER</varname></term>
        <term><varname>$LOGNAME</varname></term>
        <term><varname>$HOME</varname></term>
        <term><varname>$SHELL</varname></term>

        <listitem><para>User name (twice), home directory, and the
        login shell. The variables are set for the units that have
        <varname>User=</varname> set, which includes user
        <command>systemd</command> instances. See
        <citerefentry project='die-net'><refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>$XDG_RUNTIME_DIR</varname></term>

        <listitem><para>The directory for volatile state. Set for the
        user <command>systemd</command> instance, and also in user
        sessions. See
        <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>$XDG_SESSION_ID</varname></term>
        <term><varname>$XDG_SEAT</varname></term>
        <term><varname>$XDG_VTNR</varname></term>

        <listitem><para>The identifier of the session, the seat name,
        and virtual terminal of the session. Set by
        <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        for login sessions. <varname>$XDG_SEAT</varname> and
        <varname>$XDG_VTNR</varname> will only be set when attached to
        a seat and a tty.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>$MAINPID</varname></term>

        <listitem><para>The PID of the units main process if it is
        known. This is only set for control processes as invoked by
        <varname>ExecReload=</varname> and similar. </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>$MANAGERPID</varname></term>

        <listitem><para>The PID of the user <command>systemd</command>
        instance, set for processes spawned by it. </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>$LISTEN_FDS</varname></term>
        <term><varname>$LISTEN_PID</varname></term>

        <listitem><para>Information about file descriptors passed to a
        service for socket activation. See
        <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>$TERM</varname></term>

        <listitem><para>Terminal type, set only for units connected to
        a terminal (<varname>StandardInput=tty</varname>,
        <varname>StandardOutput=tty</varname>, or
        <varname>StandardError=tty</varname>). See
        <citerefentry project='man-pages'><refentrytitle>termcap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
        </para></listitem>
      </varlistentry>
    </variablelist>

    <para>Additional variables may be configured by the following
    means: for processes spawned in specific units, use the
    <varname>Environment=</varname> and
    <varname>EnvironmentFile=</varname> options above; to specify
    variables globally, use <varname>DefaultEnvironment=</varname>
    (see
    <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
    or the kernel option <varname>systemd.setenv=</varname> (see
    <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
    Additional variables may also be set through PAM,
    cf. <citerefentry project='man-pages'><refentrytitle>pam_env</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
  </refsect1>

  <refsect1>
      <title>See Also</title>
      <para>
        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry project='man-pages'><refentrytitle>exec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
      </para>
  </refsect1>

</refentry>