summaryrefslogtreecommitdiff
path: root/man/systemd.resource-control.xml
blob: 0551d750269508af7e6296e9d07b424b536f23af (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
<?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 2013 Zbigniew Jędrzejewski-Szmek

  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.resource-control">
  <refentryinfo>
    <title>systemd.resource-control</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.resource-control</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd.resource-control</refname>
    <refpurpose>Resource control unit settings</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para>
      <filename><replaceable>slice</replaceable>.slice</filename>,
      <filename><replaceable>scope</replaceable>.scope</filename>,
      <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, slices, scopes,
    sockets, mount points, and swap devices share a subset of
    configuration options for resource control of spawned
    processes. Internally, this relies on the Control Groups
    kernel concept for organizing processes in a hierarchical tree of
    named groups for the purpose of resource management.</para>

    <para>This man page lists the configuration options shared by
    those six 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.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>systemd.scope</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.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    and
    <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for more information on the specific unit configuration files. The
    resource control configuration options are configured in the
    [Slice], [Scope], [Service], [Socket], [Mount], or [Swap]
    sections, depending on the unit type.</para>

    <para>See the <ulink
    url="http://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/">New
    Control Group Interfaces</ulink> for an introduction on how to make
    use of resource control APIs from programs.</para>
  </refsect1>

  <refsect1>
    <title>Automatic Dependencies</title>

    <para>Units with the <varname>Slice=</varname> setting set get
    automatic <varname>Requires=</varname> and
    <varname>After=</varname> dependencies on the specified slice
    unit.</para>
  </refsect1>

  <refsect1>
    <title>Unified and Legacy Control Group Hierarchies</title>

    <para>Unified control group hierarchy is the new version of kernel control group interface. Depending on the
    resource type, there are differences in resource control capabilities.  Also, because of interface changes, some
    resource types have a separate set of options on the unified hierarchy.</para>

    <para>
      <variablelist>
        <varlistentry>
          <term><option>IO</option></term>
          <listitem>
            <para><varname>IO</varname> prefixed settings are superset of and replace <varname>BlockIO</varname>
            prefixed ones. On unified hierarchy, IO resource control also applies to buffered writes.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><option>Memory</option></term>
          <listitem>
            <para><varname>MemoryMax</varname> replaces <varname>MemoryLimit</varname>. <varname>MemoryLow</varname>
            and <varname>MemoryHigh</varname> are effective only on unified hierarchy.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </para>

    <para>To ease the transition, there is best-effort translation between the two versions of settings. If all
    settings of a unit for a given resource type are for the other hierarchy type, the settings are translated and
    applied. If there are any valid settings for the hierarchy in use, all translations are disabled for the resource
    type. Mixing the two types of settings on a unit can lead to confusing results.</para>
  </refsect1>

  <refsect1>
    <title>Options</title>

    <para>Units of the types listed above can have settings
    for resource control configuration:</para>

    <variablelist class='unit-directives'>

      <varlistentry>
        <term><varname>CPUAccounting=</varname></term>

        <listitem>
          <para>Turn on CPU usage accounting for this unit. Takes a
          boolean argument. Note that turning on CPU accounting for
          one unit will also implicitly turn it on for all units
          contained in the same slice and for all its parent slices
          and the units contained therein. The system default for this
          setting may be controlled with
          <varname>DefaultCPUAccounting=</varname> in
          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>CPUShares=<replaceable>weight</replaceable></varname></term>
        <term><varname>StartupCPUShares=<replaceable>weight</replaceable></varname></term>

        <listitem>
          <para>Assign the specified CPU time share weight to the
          processes executed. These options take an integer value and
          control the <literal>cpu.shares</literal> control group
          attribute. The allowed range is 2 to 262144. Defaults to
          1024. For details about this control group attribute, see
          <ulink
          url="https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt</ulink>.
          The available CPU time is split up among all units within
          one slice relative to their CPU time share weight.</para>

          <para>While <varname>StartupCPUShares=</varname> only
          applies to the startup phase of the system,
          <varname>CPUShares=</varname> applies to normal runtime of
          the system, and if the former is not set also to the startup
          phase. Using <varname>StartupCPUShares=</varname> allows
          prioritizing specific services at boot-up differently than
          during normal runtime.</para>

          <para>These options imply
          <literal>CPUAccounting=true</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>CPUQuota=</varname></term>

        <listitem>
          <para>Assign the specified CPU time quota to the processes
          executed. Takes a percentage value, suffixed with "%". The
          percentage specifies how much CPU time the unit shall get at
          maximum, relative to the total CPU time available on one
          CPU. Use values &gt; 100% for allotting CPU time on more than
          one CPU. This controls the
          <literal>cpu.cfs_quota_us</literal> control group
          attribute. For details about this control group attribute,
          see <ulink
          url="https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt</ulink>.</para>

          <para>Example: <varname>CPUQuota=20%</varname> ensures that
          the executed processes will never get more than 20% CPU time
          on one CPU.</para>

          <para>Implies <literal>CPUAccounting=true</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MemoryAccounting=</varname></term>

        <listitem>
          <para>Turn on process and kernel memory accounting for this
          unit. Takes a boolean argument. Note that turning on memory
          accounting for one unit will also implicitly turn it on for
          all units contained in the same slice and for all its parent
          slices and the units contained therein. The system default
          for this setting may be controlled with
          <varname>DefaultMemoryAccounting=</varname> in
          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MemoryLow=<replaceable>bytes</replaceable></varname></term>

        <listitem>
          <para>Specify the best-effort memory usage protection of the executed processes in this unit. If the memory
          usages of this unit and all its ancestors are below their low boundaries, this unit's memory won't be
          reclaimed as long as memory can be reclaimed from unprotected units.</para>

          <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
          parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a
          percentage value may be specified, which is taken relative to the installed physical memory on the
          system. This controls the <literal>memory.low</literal> control group attribute. For details about this
          control group attribute, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.</para>

          <para>Implies <literal>MemoryAccounting=true</literal>.</para>

          <para>This setting is supported only if the unified control group hierarchy is used.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MemoryHigh=<replaceable>bytes</replaceable></varname></term>

        <listitem>
          <para>Specify the high limit on memory usage of the executed processes in this unit. Memory usage may go
          above the limit if unavoidable, but the processes are heavily slowed down and memory is taken away
          aggressively in such cases. This is the main mechanism to control memory usage of a unit.</para>

          <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
          parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a
          percentage value may be specified, which is taken relative to the installed physical memory on the
          system. If assigned the
          special value <literal>infinity</literal>, no memory limit is applied. This controls the
          <literal>memory.high</literal> control group attribute. For details about this control group attribute, see
          <ulink url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.</para>

          <para>Implies <literal>MemoryAccounting=true</literal>.</para>

          <para>This setting is supported only if the unified control group hierarchy is used.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MemoryMax=<replaceable>bytes</replaceable></varname></term>

        <listitem>
          <para>Specify the absolute limit on memory usage of the executed processes in this unit. If memory usage
          cannot be contained under the limit, out-of-memory killer is invoked inside the unit. It is recommended to
          use <varname>MemoryHigh=</varname> as the main control mechanism and use <varname>MemoryMax=</varname> as the
          last line of defense.</para>

          <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
          parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a
          percentage value may be specified, which is taken relative to the installed physical memory on the system. If
          assigned the special value <literal>infinity</literal>, no memory limit is applied. This controls the
          <literal>memory.max</literal> control group attribute. For details about this control group attribute, see
          <ulink url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.</para>

          <para>Implies <literal>MemoryAccounting=true</literal>.</para>

          <para>This setting is supported only if the unified control group hierarchy is used. Use
          <varname>MemoryLimit=</varname> on systems using the legacy control group hierarchy.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>MemoryLimit=<replaceable>bytes</replaceable></varname></term>

        <listitem>
          <para>Specify the limit on maximum memory usage of the executed processes. The limit specifies how much
          process and kernel memory can be used by tasks in this unit. Takes a memory size in bytes. If the value is
          suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or
          Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is
          taken relative to the installed physical memory on the system. If assigned the special value
          <literal>infinity</literal>, no memory limit is applied. This controls the
          <literal>memory.limit_in_bytes</literal> control group attribute. For details about this control group
          attribute, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt">memory.txt</ulink>.</para>

          <para>Implies <literal>MemoryAccounting=true</literal>.</para>

          <para>This setting is supported only if the legacy control group hierarchy is used. Use
          <varname>MemoryMax=</varname> on systems using the unified control group hierarchy.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>TasksAccounting=</varname></term>

        <listitem>
          <para>Turn on task accounting for this unit. Takes a
          boolean argument. If enabled, the system manager will keep
          track of the number of tasks in the unit. The number of
          tasks accounted this way includes both kernel threads and
          userspace processes, with each thread counting
          individually. Note that turning on tasks accounting for one
          unit will also implicitly turn it on for all units contained
          in the same slice and for all its parent slices and the
          units contained therein. The system default for this setting
          may be controlled with
          <varname>DefaultTasksAccounting=</varname> in
          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>TasksMax=<replaceable>N</replaceable></varname></term>

        <listitem>
          <para>Specify the maximum number of tasks that may be
          created in the unit. This ensures that the number of tasks
          accounted for the unit (see above) stays below a specific
          limit. If assigned the special value
          <literal>infinity</literal>, no tasks limit is applied. This
          controls the <literal>pids.max</literal> control group
          attribute. For details about this control group attribute,
          see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroup-v1/pids.txt">pids.txt</ulink>.</para>

          <para>Implies <literal>TasksAccounting=true</literal>. The
          system default for this setting may be controlled with
          <varname>DefaultTasksMax=</varname> in
          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>IOAccounting=</varname></term>

        <listitem>
          <para>Turn on Block I/O accounting for this unit, if the unified control group hierarchy is used on the
          system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly
          turn it on for all units contained in the same slice and all for its parent slices and the units contained
          therein. The system default for this setting may be controlled with <varname>DefaultIOAccounting=</varname>
          in
          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>

          <para>This setting is supported only if the unified control group hierarchy is used. Use
          <varname>BlockIOAccounting=</varname> on systems using the legacy control group hierarchy.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>IOWeight=<replaceable>weight</replaceable></varname></term>
        <term><varname>StartupIOWeight=<replaceable>weight</replaceable></varname></term>

        <listitem>
          <para>Set the default overall block I/O weight for the executed processes, if the unified control group
          hierarchy is used on the system. Takes a single weight value (between 1 and 10000) to set the default block
          I/O weight. This controls the <literal>io.weight</literal> control group attribute, which defaults to
          100. For details about this control group attribute, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.  The available I/O
          bandwidth is split up among all units within one slice relative to their block I/O weight.</para>

          <para>While <varname>StartupIOWeight=</varname> only applies
          to the startup phase of the system,
          <varname>IOWeight=</varname> applies to the later runtime of
          the system, and if the former is not set also to the startup
          phase. This allows prioritizing specific services at boot-up
          differently than during runtime.</para>

          <para>Implies <literal>IOAccounting=true</literal>.</para>

          <para>This setting is supported only if the unified control group hierarchy is used. Use
          <varname>BlockIOWeight=</varname> and <varname>StartupBlockIOWeight=</varname> on systems using the legacy
          control group hierarchy.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>IODeviceWeight=<replaceable>device</replaceable> <replaceable>weight</replaceable></varname></term>

        <listitem>
          <para>Set the per-device overall block I/O weight for the executed processes, if the unified control group
          hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify
          the device specific weight value, between 1 and 10000. (Example: "/dev/sda 1000"). The file path may be
          specified as path to a block device node or as any other file, in which case the backing block device of the
          file system of the file is determined. This controls the <literal>io.weight</literal> control group
          attribute, which defaults to 100. Use this option multiple times to set weights for multiple devices. For
          details about this control group attribute, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.</para>

          <para>Implies <literal>IOAccounting=true</literal>.</para>

          <para>This setting is supported only if the unified control group hierarchy is used. Use
          <varname>BlockIODeviceWeight=</varname> on systems using the legacy control group hierarchy.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>IOReadBandwidthMax=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term>
        <term><varname>IOWriteBandwidthMax=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term>

        <listitem>
          <para>Set the per-device overall block I/O bandwidth maximum limit for the executed processes, if the unified
          control group hierarchy is used on the system. This limit is not work-conserving and the executed processes
          are not allowed to use more even if the device has idle capacity.  Takes a space-separated pair of a file
          path and a bandwidth value (in bytes per second) to specify the device specific bandwidth. The file path may
          be a path to a block device node, or as any other file in which case the backing block device of the file
          system of the file is used. If the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is
          parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes, respectively, to the base of 1000. (Example:
          "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the <literal>io.max</literal> control
          group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For details
          about this control group attribute, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.
          </para>

          <para>Implies <literal>IOAccounting=true</literal>.</para>

          <para>This setting is supported only if the unified control group hierarchy is used. Use
          <varname>BlockIOAccounting=</varname> on systems using the legacy control group hierarchy.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>IOReadIOPSMax=<replaceable>device</replaceable> <replaceable>IOPS</replaceable></varname></term>
        <term><varname>IOWriteIOPSMax=<replaceable>device</replaceable> <replaceable>IOPS</replaceable></varname></term>

        <listitem>
          <para>Set the per-device overall block I/O IOs-Per-Second maximum limit for the executed processes, if the
          unified control group hierarchy is used on the system. This limit is not work-conserving and the executed
          processes are not allowed to use more even if the device has idle capacity.  Takes a space-separated pair of
          a file path and an IOPS value to specify the device specific IOPS. The file path may be a path to a block
          device node, or as any other file in which case the backing block device of the file system of the file is
          used. If the IOPS is suffixed with K, M, G, or T, the specified IOPS is parsed as KiloIOPS, MegaIOPS,
          GigaIOPS, or TeraIOPS, respectively, to the base of 1000. (Example:
          "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 1K"). This controls the <literal>io.max</literal> control
          group attributes. Use this option multiple times to set IOPS limits for multiple devices. For details about
          this control group attribute, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt</ulink>.
          </para>

          <para>Implies <literal>IOAccounting=true</literal>.</para>

          <para>This setting is supported only if the unified control group hierarchy is used.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>BlockIOAccounting=</varname></term>

        <listitem>
          <para>Turn on Block I/O accounting for this unit, if the legacy control group hierarchy is used on the
          system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly
          turn it on for all units contained in the same slice and all for its parent slices and the units contained
          therein. The system default for this setting may be controlled with
          <varname>DefaultBlockIOAccounting=</varname> in
          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>

          <para>This setting is supported only if the legacy control group hierarchy is used. Use
          <varname>IOAccounting=</varname> on systems using the unified control group hierarchy.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>BlockIOWeight=<replaceable>weight</replaceable></varname></term>
        <term><varname>StartupBlockIOWeight=<replaceable>weight</replaceable></varname></term>

        <listitem><para>Set the default overall block I/O weight for the executed processes, if the legacy control
        group hierarchy is used on the system. Takes a single weight value (between 10 and 1000) to set the default
        block I/O weight. This controls the <literal>blkio.weight</literal> control group attribute, which defaults to
        500. For details about this control group attribute, see <ulink
        url="https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt</ulink>.
        The available I/O bandwidth is split up among all units within one slice relative to their block I/O
        weight.</para>

        <para>While <varname>StartupBlockIOWeight=</varname> only
        applies to the startup phase of the system,
        <varname>BlockIOWeight=</varname> applies to the later runtime
        of the system, and if the former is not set also to the
        startup phase. This allows prioritizing specific services at
        boot-up differently than during runtime.</para>

        <para>Implies
        <literal>BlockIOAccounting=true</literal>.</para>

        <para>This setting is supported only if the legacy control group hierarchy is used. Use
        <varname>IOWeight=</varname> and <varname>StartupIOWeight=</varname> on systems using the unified control group
        hierarchy.</para>

      </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>BlockIODeviceWeight=<replaceable>device</replaceable> <replaceable>weight</replaceable></varname></term>

        <listitem>
          <para>Set the per-device overall block I/O weight for the executed processes, if the legacy control group
          hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify
          the device specific weight value, between 10 and 1000. (Example: "/dev/sda 500"). The file path may be
          specified as path to a block device node or as any other file, in which case the backing block device of the
          file system of the file is determined. This controls the <literal>blkio.weight_device</literal> control group
          attribute, which defaults to 1000. Use this option multiple times to set weights for multiple devices. For
          details about this control group attribute, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt</ulink>.</para>

          <para>Implies
          <literal>BlockIOAccounting=true</literal>.</para>

          <para>This setting is supported only if the legacy control group hierarchy is used. Use
          <varname>IODeviceWeight=</varname> on systems using the unified control group hierarchy.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>BlockIOReadBandwidth=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term>
        <term><varname>BlockIOWriteBandwidth=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term>

        <listitem>
          <para>Set the per-device overall block I/O bandwidth limit for the executed processes, if the legacy control
          group hierarchy is used on the system. Takes a space-separated pair of a file path and a bandwidth value (in
          bytes per second) to specify the device specific bandwidth. The file path may be a path to a block device
          node, or as any other file in which case the backing block device of the file system of the file is used. If
          the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is parsed as Kilobytes, Megabytes,
          Gigabytes, or Terabytes, respectively, to the base of 1000. (Example:
          "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the
          <literal>blkio.throttle.read_bps_device</literal> and <literal>blkio.throttle.write_bps_device</literal>
          control group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For
          details about these control group attributes, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt</ulink>.
          </para>

          <para>Implies
          <literal>BlockIOAccounting=true</literal>.</para>

          <para>This setting is supported only if the legacy control group hierarchy is used. Use
          <varname>IOReadBandwidthMax=</varname> and <varname>IOWriteBandwidthMax=</varname> on systems using the
          unified control group hierarchy.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>DeviceAllow=</varname></term>

        <listitem>
          <para>Control access to specific device nodes by the
          executed processes. Takes two space-separated strings: a
          device node specifier followed by a combination of
          <constant>r</constant>, <constant>w</constant>,
          <constant>m</constant> to control
          <emphasis>r</emphasis>eading, <emphasis>w</emphasis>riting,
          or creation of the specific device node(s) by the unit
          (<emphasis>m</emphasis>knod), respectively. This controls
          the <literal>devices.allow</literal> and
          <literal>devices.deny</literal> control group
          attributes. For details about these control group
          attributes, see <ulink
          url="https://www.kernel.org/doc/Documentation/cgroup-v1/devices.txt">devices.txt</ulink>.</para>

          <para>The device node specifier is either a path to a device
          node in the file system, starting with
          <filename>/dev/</filename>, or a string starting with either
          <literal>char-</literal> or <literal>block-</literal>
          followed by a device group name, as listed in
          <filename>/proc/devices</filename>. The latter is useful to
          whitelist all current and future devices belonging to a
          specific device group at once. The device group is matched
          according to file name globbing rules, you may hence use the
          <literal>*</literal> and <literal>?</literal>
          wildcards. Examples: <filename>/dev/sda5</filename> is a
          path to a device node, referring to an ATA or SCSI block
          device. <literal>char-pts</literal> and
          <literal>char-alsa</literal> are specifiers for all pseudo
          TTYs and all ALSA sound devices,
          respectively. <literal>char-cpu/*</literal> is a specifier
          matching all CPU related device groups.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>DevicePolicy=auto|closed|strict</varname></term>

        <listitem>
          <para>
            Control the policy for allowing device access:
          </para>
          <variablelist>
            <varlistentry>
              <term><option>strict</option></term>
              <listitem>
                <para>means to only allow types of access that are
                explicitly specified.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>closed</option></term>
              <listitem>
                <para>in addition, allows access to standard pseudo
                devices including
                <filename>/dev/null</filename>,
                <filename>/dev/zero</filename>,
                <filename>/dev/full</filename>,
                <filename>/dev/random</filename>, and
                <filename>/dev/urandom</filename>.
                </para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>auto</option></term>
              <listitem>
                <para>
                  in addition, allows access to all devices if no
                  explicit <varname>DeviceAllow=</varname> is present.
                  This is the default.
                </para>
              </listitem>
            </varlistentry>
          </variablelist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Slice=</varname></term>

        <listitem>
          <para>The name of the slice unit to place the unit
          in. Defaults to <filename>system.slice</filename> for all
          non-instantiated units of all unit types (except for slice
          units themselves see below). Instance units are by default
          placed in a subslice of <filename>system.slice</filename>
          that is named after the template name.</para>

          <para>This option may be used to arrange systemd units in a
          hierarchy of slices each of which might have resource
          settings applied.</para>

          <para>For units of type slice, the only accepted value for
          this setting is the parent slice. Since the name of a slice
          unit implies the parent slice, it is hence redundant to ever
          set this parameter directly for slice units.</para>

          <para>Special care should be taken when relying on the default slice assignment in templated service units
          that have <varname>DefaultDependencies=no</varname> set, see
          <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, section
          "Automatic Dependencies" for details.</para>

        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Delegate=</varname></term>

        <listitem>
          <para>Turns on delegation of further resource control
          partitioning to processes of the unit. For unprivileged
          services (i.e. those using the <varname>User=</varname>
          setting), this allows processes to create a subhierarchy
          beneath its control group path. For privileged services and
          scopes, this ensures the processes will have all control
          group controllers enabled.</para>
        </listitem>
      </varlistentry>

    </variablelist>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
      The documentation for control groups and specific controllers in the Linux kernel:
      <ulink url="https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt">cgroups.txt</ulink>,
      <ulink url="https://www.kernel.org/doc/Documentation/cgroup-v1/cpuacct.txt">cpuacct.txt</ulink>,
      <ulink url="https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt">memory.txt</ulink>,
      <ulink url="https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt</ulink>.
    </para>
  </refsect1>
</refentry>