1 <?xml version='
1.0'
?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
6 This file is part of systemd.
8 Copyright 2013 Zbigniew Jędrzejewski-Szmek
10 systemd is free software; you can redistribute it and/or modify it
11 under the terms of the GNU Lesser General Public License as published by
12 the Free Software Foundation; either version 2.1 of the License, or
13 (at your option) any later version.
15 systemd is distributed in the hope that it will be useful, but
16 WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 Lesser General Public License for more details.
20 You should have received a copy of the GNU Lesser General Public License
21 along with systemd; If not, see <http://www.gnu.org/licenses/>.
24 <refentry id=
"systemd.resource-control">
26 <title>systemd.resource-control
</title>
27 <productname>systemd
</productname>
31 <contrib>Developer
</contrib>
32 <firstname>Lennart
</firstname>
33 <surname>Poettering
</surname>
34 <email>lennart@poettering.net
</email>
40 <refentrytitle>systemd.resource-control
</refentrytitle>
41 <manvolnum>5</manvolnum>
45 <refname>systemd.resource-control
</refname>
46 <refpurpose>Resource control unit settings
</refpurpose>
51 <filename><replaceable>slice
</replaceable>.slice
</filename>,
52 <filename><replaceable>scope
</replaceable>.scope
</filename>,
53 <filename><replaceable>service
</replaceable>.service
</filename>,
54 <filename><replaceable>socket
</replaceable>.socket
</filename>,
55 <filename><replaceable>mount
</replaceable>.mount
</filename>,
56 <filename><replaceable>swap
</replaceable>.swap
</filename>
61 <title>Description
</title>
63 <para>Unit configuration files for services, slices, scopes,
64 sockets, mount points, and swap devices share a subset of
65 configuration options for resource control of spawned
66 processes. Internally, this relies on the Control Groups
67 kernel concept for organizing processes in a hierarchical tree of
68 named groups for the purpose of resource management.
</para>
70 <para>This man page lists the configuration options shared by
71 those six unit types. See
72 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
73 for the common options of all unit configuration files, and
74 <citerefentry><refentrytitle>systemd.slice
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
75 <citerefentry><refentrytitle>systemd.scope
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
76 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
77 <citerefentry><refentrytitle>systemd.socket
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
78 <citerefentry><refentrytitle>systemd.mount
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
80 <citerefentry><refentrytitle>systemd.swap
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
81 for more information on the specific unit configuration files. The
82 resource control configuration options are configured in the
83 [Slice], [Scope], [Service], [Socket], [Mount], or [Swap]
84 sections, depending on the unit type.
</para>
87 url=
"http://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/">New
88 Control Group Interfaces
</ulink> for an introduction on how to make
89 use of resource control APIs from programs.
</para>
93 <title>Automatic Dependencies
</title>
95 <para>Units with the
<varname>Slice=
</varname> setting set automatically acquire
<varname>Requires=
</varname> and
96 <varname>After=
</varname> dependencies on the specified slice unit.
</para>
100 <title>Unified and Legacy Control Group Hierarchies
</title>
102 <para>The unified control group hierarchy is the new version of kernel control group interface, see
<ulink
103 url=
"https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt
</ulink>. Depending on the resource type,
104 there are differences in resource control capabilities. Also, because of interface changes, some resource types
105 have separate set of options on the unified hierarchy.
</para>
111 <term><option>CPU
</option></term>
113 <para>Due to the lack of consensus in the kernel community, the CPU controller support on the unified
114 cgroup hierarchy requires out-of-tree kernel patches. See
<ulink
115 url=
"https://git.kernel.org/cgit/linux/kernel/git/tj/cgroup.git/tree/Documentation/cgroup-v2-cpu.txt?h=cgroup-v2-cpu">cgroup-v2-cpu.txt
</ulink>.
</para>
117 <para><varname>CPUWeight=
</varname> and
<varname>StartupCPUWeight=
</varname> replace
118 <varname>CPUShares=
</varname> and
<varname>StartupCPUShares=
</varname>, respectively.
</para>
120 <para>The
<literal>cpuacct
</literal> controller does not exist separately on the unified hierarchy.
</para>
125 <term><option>Memory
</option></term>
127 <para><varname>MemoryMax=
</varname> replaces
<varname>MemoryLimit=
</varname>.
<varname>MemoryLow=
</varname>
128 and
<varname>MemoryHigh=
</varname> are effective only on unified hierarchy.
</para>
133 <term><option>IO
</option></term>
135 <para><varname>IO
</varname> prefixed settings are superset of and replace
<varname>BlockIO
</varname>
136 prefixed ones. On unified hierarchy, IO resource control also applies to buffered writes.
</para>
143 <para>To ease the transition, there is best-effort translation between the two versions of settings. If all
144 settings of a unit for a given resource type are for the other hierarchy type, the settings are translated and
145 applied. If there are any valid settings for the hierarchy in use, all translations are disabled for the resource
146 type. Mixing the two types of settings on a unit can lead to confusing results.
</para>
148 <para>Legacy control group hierarchy (see
<ulink
149 url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt">cgroups.txt
</ulink>), also called cgroup-v1,
150 doesn't allow safe delegation of controllers to unprivileged processes. If the system uses the legacy control group
151 hierarchy, resource control is disabled for systemd user instance, see
152 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
157 <title>Options
</title>
159 <para>Units of the types listed above can have settings
160 for resource control configuration:
</para>
162 <variablelist class='unit-directives'
>
165 <term><varname>CPUAccounting=
</varname></term>
168 <para>Turn on CPU usage accounting for this unit. Takes a
169 boolean argument. Note that turning on CPU accounting for
170 one unit will also implicitly turn it on for all units
171 contained in the same slice and for all its parent slices
172 and the units contained therein. The system default for this
173 setting may be controlled with
174 <varname>DefaultCPUAccounting=
</varname> in
175 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
180 <term><varname>CPUWeight=
<replaceable>weight
</replaceable></varname></term>
181 <term><varname>StartupCPUWeight=
<replaceable>weight
</replaceable></varname></term>
184 <para>Assign the specified CPU time weight to the processes executed, if the unified control group hierarchy
185 is used on the system. These options take an integer value and control the
<literal>cpu.weight
</literal>
186 control group attribute. The allowed range is
1 to
10000. Defaults to
100. For details about this control
187 group attribute, see
<ulink
188 url=
"https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt
</ulink> and
<ulink
189 url=
"https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt
</ulink>.
190 The available CPU time is split up among all units within one slice relative to their CPU time weight.
</para>
192 <para>While
<varname>StartupCPUWeight=
</varname> only applies to the startup phase of the system,
193 <varname>CPUWeight=
</varname> applies to normal runtime of the system, and if the former is not set also to
194 the startup phase. Using
<varname>StartupCPUWeight=
</varname> allows prioritizing specific services at
195 boot-up differently than during normal runtime.
</para>
197 <para>Implies
<literal>CPUAccounting=true
</literal>.
</para>
199 <para>These settings are supported only if the unified control group hierarchy is used.
</para>
204 <term><varname>CPUShares=
<replaceable>weight
</replaceable></varname></term>
205 <term><varname>StartupCPUShares=
<replaceable>weight
</replaceable></varname></term>
208 <para>Assign the specified CPU time share weight to the processes executed. These options take an integer
209 value and control the
<literal>cpu.shares
</literal> control group attribute. The allowed range is
2 to
210 262144. Defaults to
1024. For details about this control group attribute, see
<ulink
211 url=
"https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt
</ulink>.
212 The available CPU time is split up among all units within one slice relative to their CPU time share
215 <para>While
<varname>StartupCPUShares=
</varname> only applies to the startup phase of the system,
216 <varname>CPUShares=
</varname> applies to normal runtime of the system, and if the former is not set also to
217 the startup phase. Using
<varname>StartupCPUShares=
</varname> allows prioritizing specific services at
218 boot-up differently than during normal runtime.
</para>
220 <para>Implies
<literal>CPUAccounting=true
</literal>.
</para>
222 <para>These settings are supported only if the legacy control group hierarchy is used.
</para>
227 <term><varname>CPUQuota=
</varname></term>
230 <para>Assign the specified CPU time quota to the processes executed. Takes a percentage value, suffixed with
231 "%". The percentage specifies how much CPU time the unit shall get at maximum, relative to the total CPU time
232 available on one CPU. Use values
> 100% for allotting CPU time on more than one CPU. This controls the
233 <literal>cpu.max
</literal> attribute on the unified control group hierarchy and
234 <literal>cpu.cfs_quota_us
</literal> on legacy. For details about these control group attributes, see
<ulink
235 url=
"https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt
</ulink> and
<ulink
236 url=
"https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt
</ulink>.
</para>
238 <para>Example:
<varname>CPUQuota=
20%
</varname> ensures that the executed processes will never get more than
239 20% CPU time on one CPU.
</para>
241 <para>Implies
<literal>CPUAccounting=true
</literal>.
</para>
243 <para>This setting is supported on both unified and legacy control group hierarchies.
</para>
248 <term><varname>MemoryAccounting=
</varname></term>
251 <para>Turn on process and kernel memory accounting for this
252 unit. Takes a boolean argument. Note that turning on memory
253 accounting for one unit will also implicitly turn it on for
254 all units contained in the same slice and for all its parent
255 slices and the units contained therein. The system default
256 for this setting may be controlled with
257 <varname>DefaultMemoryAccounting=
</varname> in
258 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
263 <term><varname>MemoryLow=
<replaceable>bytes
</replaceable></varname></term>
266 <para>Specify the best-effort memory usage protection of the executed processes in this unit. If the memory
267 usages of this unit and all its ancestors are below their low boundaries, this unit's memory won't be
268 reclaimed as long as memory can be reclaimed from unprotected units.
</para>
270 <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
271 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base
1024), respectively. Alternatively, a
272 percentage value may be specified, which is taken relative to the installed physical memory on the
273 system. This controls the
<literal>memory.low
</literal> control group attribute. For details about this
274 control group attribute, see
<ulink
275 url=
"https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt
</ulink>.
</para>
277 <para>Implies
<literal>MemoryAccounting=true
</literal>.
</para>
279 <para>This setting is supported only if the unified control group hierarchy is used.
</para>
284 <term><varname>MemoryHigh=
<replaceable>bytes
</replaceable></varname></term>
287 <para>Specify the high limit on memory usage of the executed processes in this unit. Memory usage may go
288 above the limit if unavoidable, but the processes are heavily slowed down and memory is taken away
289 aggressively in such cases. This is the main mechanism to control memory usage of a unit.
</para>
291 <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
292 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base
1024), respectively. Alternatively, a
293 percentage value may be specified, which is taken relative to the installed physical memory on the
294 system. If assigned the
295 special value
<literal>infinity
</literal>, no memory limit is applied. This controls the
296 <literal>memory.high
</literal> control group attribute. For details about this control group attribute, see
297 <ulink url=
"https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt
</ulink>.
</para>
299 <para>Implies
<literal>MemoryAccounting=true
</literal>.
</para>
301 <para>This setting is supported only if the unified control group hierarchy is used.
</para>
306 <term><varname>MemoryMax=
<replaceable>bytes
</replaceable></varname></term>
309 <para>Specify the absolute limit on memory usage of the executed processes in this unit. If memory usage
310 cannot be contained under the limit, out-of-memory killer is invoked inside the unit. It is recommended to
311 use
<varname>MemoryHigh=
</varname> as the main control mechanism and use
<varname>MemoryMax=
</varname> as the
312 last line of defense.
</para>
314 <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
315 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base
1024), respectively. Alternatively, a
316 percentage value may be specified, which is taken relative to the installed physical memory on the system. If
317 assigned the special value
<literal>infinity
</literal>, no memory limit is applied. This controls the
318 <literal>memory.max
</literal> control group attribute. For details about this control group attribute, see
319 <ulink url=
"https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt
</ulink>.
</para>
321 <para>Implies
<literal>MemoryAccounting=true
</literal>.
</para>
323 <para>This setting is supported only if the unified control group hierarchy is used. Use
324 <varname>MemoryLimit=
</varname> on systems using the legacy control group hierarchy.
</para>
329 <term><varname>MemoryLimit=
<replaceable>bytes
</replaceable></varname></term>
332 <para>Specify the limit on maximum memory usage of the executed processes. The limit specifies how much
333 process and kernel memory can be used by tasks in this unit. Takes a memory size in bytes. If the value is
334 suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or
335 Terabytes (with the base
1024), respectively. Alternatively, a percentage value may be specified, which is
336 taken relative to the installed physical memory on the system. If assigned the special value
337 <literal>infinity
</literal>, no memory limit is applied. This controls the
338 <literal>memory.limit_in_bytes
</literal> control group attribute. For details about this control group
339 attribute, see
<ulink
340 url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt">memory.txt
</ulink>.
</para>
342 <para>Implies
<literal>MemoryAccounting=true
</literal>.
</para>
344 <para>This setting is supported only if the legacy control group hierarchy is used. Use
345 <varname>MemoryMax=
</varname> on systems using the unified control group hierarchy.
</para>
350 <term><varname>TasksAccounting=
</varname></term>
353 <para>Turn on task accounting for this unit. Takes a
354 boolean argument. If enabled, the system manager will keep
355 track of the number of tasks in the unit. The number of
356 tasks accounted this way includes both kernel threads and
357 userspace processes, with each thread counting
358 individually. Note that turning on tasks accounting for one
359 unit will also implicitly turn it on for all units contained
360 in the same slice and for all its parent slices and the
361 units contained therein. The system default for this setting
362 may be controlled with
363 <varname>DefaultTasksAccounting=
</varname> in
364 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
369 <term><varname>TasksMax=
<replaceable>N
</replaceable></varname></term>
372 <para>Specify the maximum number of tasks that may be created in the unit. This ensures that the number of
373 tasks accounted for the unit (see above) stays below a specific limit. This either takes an absolute number
374 of tasks or a percentage value that is taken relative to the configured maximum number of tasks on the
375 system. If assigned the special value
<literal>infinity
</literal>, no tasks limit is applied. This controls
376 the
<literal>pids.max
</literal> control group attribute. For details about this control group attribute, see
377 <ulink url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/pids.txt">pids.txt
</ulink>.
</para>
379 <para>Implies
<literal>TasksAccounting=true
</literal>. The
380 system default for this setting may be controlled with
381 <varname>DefaultTasksMax=
</varname> in
382 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
387 <term><varname>IOAccounting=
</varname></term>
390 <para>Turn on Block I/O accounting for this unit, if the unified control group hierarchy is used on the
391 system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly
392 turn it on for all units contained in the same slice and all for its parent slices and the units contained
393 therein. The system default for this setting may be controlled with
<varname>DefaultIOAccounting=
</varname>
395 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
397 <para>This setting is supported only if the unified control group hierarchy is used. Use
398 <varname>BlockIOAccounting=
</varname> on systems using the legacy control group hierarchy.
</para>
403 <term><varname>IOWeight=
<replaceable>weight
</replaceable></varname></term>
404 <term><varname>StartupIOWeight=
<replaceable>weight
</replaceable></varname></term>
407 <para>Set the default overall block I/O weight for the executed processes, if the unified control group
408 hierarchy is used on the system. Takes a single weight value (between
1 and
10000) to set the default block
409 I/O weight. This controls the
<literal>io.weight
</literal> control group attribute, which defaults to
410 100. For details about this control group attribute, see
<ulink
411 url=
"https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt
</ulink>. The available I/O
412 bandwidth is split up among all units within one slice relative to their block I/O weight.
</para>
414 <para>While
<varname>StartupIOWeight=
</varname> only applies
415 to the startup phase of the system,
416 <varname>IOWeight=
</varname> applies to the later runtime of
417 the system, and if the former is not set also to the startup
418 phase. This allows prioritizing specific services at boot-up
419 differently than during runtime.
</para>
421 <para>Implies
<literal>IOAccounting=true
</literal>.
</para>
423 <para>This setting is supported only if the unified control group hierarchy is used. Use
424 <varname>BlockIOWeight=
</varname> and
<varname>StartupBlockIOWeight=
</varname> on systems using the legacy
425 control group hierarchy.
</para>
430 <term><varname>IODeviceWeight=
<replaceable>device
</replaceable> <replaceable>weight
</replaceable></varname></term>
433 <para>Set the per-device overall block I/O weight for the executed processes, if the unified control group
434 hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify
435 the device specific weight value, between
1 and
10000. (Example:
"/dev/sda 1000"). The file path may be
436 specified as path to a block device node or as any other file, in which case the backing block device of the
437 file system of the file is determined. This controls the
<literal>io.weight
</literal> control group
438 attribute, which defaults to
100. Use this option multiple times to set weights for multiple devices. For
439 details about this control group attribute, see
<ulink
440 url=
"https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt
</ulink>.
</para>
442 <para>Implies
<literal>IOAccounting=true
</literal>.
</para>
444 <para>This setting is supported only if the unified control group hierarchy is used. Use
445 <varname>BlockIODeviceWeight=
</varname> on systems using the legacy control group hierarchy.
</para>
450 <term><varname>IOReadBandwidthMax=
<replaceable>device
</replaceable> <replaceable>bytes
</replaceable></varname></term>
451 <term><varname>IOWriteBandwidthMax=
<replaceable>device
</replaceable> <replaceable>bytes
</replaceable></varname></term>
454 <para>Set the per-device overall block I/O bandwidth maximum limit for the executed processes, if the unified
455 control group hierarchy is used on the system. This limit is not work-conserving and the executed processes
456 are not allowed to use more even if the device has idle capacity. Takes a space-separated pair of a file
457 path and a bandwidth value (in bytes per second) to specify the device specific bandwidth. The file path may
458 be a path to a block device node, or as any other file in which case the backing block device of the file
459 system of the file is used. If the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is
460 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes, respectively, to the base of
1000. (Example:
461 "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the
<literal>io.max
</literal> control
462 group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For details
463 about this control group attribute, see
<ulink
464 url=
"https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt
</ulink>.
467 <para>Implies
<literal>IOAccounting=true
</literal>.
</para>
469 <para>This setting is supported only if the unified control group hierarchy is used. Use
470 <varname>BlockIOAccounting=
</varname> on systems using the legacy control group hierarchy.
</para>
475 <term><varname>IOReadIOPSMax=
<replaceable>device
</replaceable> <replaceable>IOPS
</replaceable></varname></term>
476 <term><varname>IOWriteIOPSMax=
<replaceable>device
</replaceable> <replaceable>IOPS
</replaceable></varname></term>
479 <para>Set the per-device overall block I/O IOs-Per-Second maximum limit for the executed processes, if the
480 unified control group hierarchy is used on the system. This limit is not work-conserving and the executed
481 processes are not allowed to use more even if the device has idle capacity. Takes a space-separated pair of
482 a file path and an IOPS value to specify the device specific IOPS. The file path may be a path to a block
483 device node, or as any other file in which case the backing block device of the file system of the file is
484 used. If the IOPS is suffixed with K, M, G, or T, the specified IOPS is parsed as KiloIOPS, MegaIOPS,
485 GigaIOPS, or TeraIOPS, respectively, to the base of
1000. (Example:
486 "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 1K"). This controls the
<literal>io.max
</literal> control
487 group attributes. Use this option multiple times to set IOPS limits for multiple devices. For details about
488 this control group attribute, see
<ulink
489 url=
"https://www.kernel.org/doc/Documentation/cgroup-v2.txt">cgroup-v2.txt
</ulink>.
492 <para>Implies
<literal>IOAccounting=true
</literal>.
</para>
494 <para>This setting is supported only if the unified control group hierarchy is used.
</para>
499 <term><varname>BlockIOAccounting=
</varname></term>
502 <para>Turn on Block I/O accounting for this unit, if the legacy control group hierarchy is used on the
503 system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly
504 turn it on for all units contained in the same slice and all for its parent slices and the units contained
505 therein. The system default for this setting may be controlled with
506 <varname>DefaultBlockIOAccounting=
</varname> in
507 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
509 <para>This setting is supported only if the legacy control group hierarchy is used. Use
510 <varname>IOAccounting=
</varname> on systems using the unified control group hierarchy.
</para>
515 <term><varname>BlockIOWeight=
<replaceable>weight
</replaceable></varname></term>
516 <term><varname>StartupBlockIOWeight=
<replaceable>weight
</replaceable></varname></term>
518 <listitem><para>Set the default overall block I/O weight for the executed processes, if the legacy control
519 group hierarchy is used on the system. Takes a single weight value (between
10 and
1000) to set the default
520 block I/O weight. This controls the
<literal>blkio.weight
</literal> control group attribute, which defaults to
521 500. For details about this control group attribute, see
<ulink
522 url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt
</ulink>.
523 The available I/O bandwidth is split up among all units within one slice relative to their block I/O
526 <para>While
<varname>StartupBlockIOWeight=
</varname> only
527 applies to the startup phase of the system,
528 <varname>BlockIOWeight=
</varname> applies to the later runtime
529 of the system, and if the former is not set also to the
530 startup phase. This allows prioritizing specific services at
531 boot-up differently than during runtime.
</para>
534 <literal>BlockIOAccounting=true
</literal>.
</para>
536 <para>This setting is supported only if the legacy control group hierarchy is used. Use
537 <varname>IOWeight=
</varname> and
<varname>StartupIOWeight=
</varname> on systems using the unified control group
544 <term><varname>BlockIODeviceWeight=
<replaceable>device
</replaceable> <replaceable>weight
</replaceable></varname></term>
547 <para>Set the per-device overall block I/O weight for the executed processes, if the legacy control group
548 hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify
549 the device specific weight value, between
10 and
1000. (Example:
"/dev/sda 500"). The file path may be
550 specified as path to a block device node or as any other file, in which case the backing block device of the
551 file system of the file is determined. This controls the
<literal>blkio.weight_device
</literal> control group
552 attribute, which defaults to
1000. Use this option multiple times to set weights for multiple devices. For
553 details about this control group attribute, see
<ulink
554 url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt
</ulink>.
</para>
557 <literal>BlockIOAccounting=true
</literal>.
</para>
559 <para>This setting is supported only if the legacy control group hierarchy is used. Use
560 <varname>IODeviceWeight=
</varname> on systems using the unified control group hierarchy.
</para>
565 <term><varname>BlockIOReadBandwidth=
<replaceable>device
</replaceable> <replaceable>bytes
</replaceable></varname></term>
566 <term><varname>BlockIOWriteBandwidth=
<replaceable>device
</replaceable> <replaceable>bytes
</replaceable></varname></term>
569 <para>Set the per-device overall block I/O bandwidth limit for the executed processes, if the legacy control
570 group hierarchy is used on the system. Takes a space-separated pair of a file path and a bandwidth value (in
571 bytes per second) to specify the device specific bandwidth. The file path may be a path to a block device
572 node, or as any other file in which case the backing block device of the file system of the file is used. If
573 the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is parsed as Kilobytes, Megabytes,
574 Gigabytes, or Terabytes, respectively, to the base of
1000. (Example:
575 "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the
576 <literal>blkio.throttle.read_bps_device
</literal> and
<literal>blkio.throttle.write_bps_device
</literal>
577 control group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For
578 details about these control group attributes, see
<ulink
579 url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt
</ulink>.
583 <literal>BlockIOAccounting=true
</literal>.
</para>
585 <para>This setting is supported only if the legacy control group hierarchy is used. Use
586 <varname>IOReadBandwidthMax=
</varname> and
<varname>IOWriteBandwidthMax=
</varname> on systems using the
587 unified control group hierarchy.
</para>
592 <term><varname>DeviceAllow=
</varname></term>
595 <para>Control access to specific device nodes by the
596 executed processes. Takes two space-separated strings: a
597 device node specifier followed by a combination of
598 <constant>r
</constant>,
<constant>w
</constant>,
599 <constant>m
</constant> to control
600 <emphasis>r
</emphasis>eading,
<emphasis>w
</emphasis>riting,
601 or creation of the specific device node(s) by the unit
602 (
<emphasis>m
</emphasis>knod), respectively. This controls
603 the
<literal>devices.allow
</literal> and
604 <literal>devices.deny
</literal> control group
605 attributes. For details about these control group
606 attributes, see
<ulink
607 url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/devices.txt">devices.txt
</ulink>.
</para>
609 <para>The device node specifier is either a path to a device
610 node in the file system, starting with
611 <filename>/dev/
</filename>, or a string starting with either
612 <literal>char-
</literal> or
<literal>block-
</literal>
613 followed by a device group name, as listed in
614 <filename>/proc/devices
</filename>. The latter is useful to
615 whitelist all current and future devices belonging to a
616 specific device group at once. The device group is matched
617 according to file name globbing rules, you may hence use the
618 <literal>*
</literal> and
<literal>?
</literal>
619 wildcards. Examples:
<filename>/dev/sda5
</filename> is a
620 path to a device node, referring to an ATA or SCSI block
621 device.
<literal>char-pts
</literal> and
622 <literal>char-alsa
</literal> are specifiers for all pseudo
623 TTYs and all ALSA sound devices,
624 respectively.
<literal>char-cpu/*
</literal> is a specifier
625 matching all CPU related device groups.
</para>
630 <term><varname>DevicePolicy=auto|closed|strict
</varname></term>
634 Control the policy for allowing device access:
638 <term><option>strict
</option></term>
640 <para>means to only allow types of access that are
641 explicitly specified.
</para>
646 <term><option>closed
</option></term>
648 <para>in addition, allows access to standard pseudo
650 <filename>/dev/null
</filename>,
651 <filename>/dev/zero
</filename>,
652 <filename>/dev/full
</filename>,
653 <filename>/dev/random
</filename>, and
654 <filename>/dev/urandom
</filename>.
660 <term><option>auto
</option></term>
663 in addition, allows access to all devices if no
664 explicit
<varname>DeviceAllow=
</varname> is present.
674 <term><varname>Slice=
</varname></term>
677 <para>The name of the slice unit to place the unit
678 in. Defaults to
<filename>system.slice
</filename> for all
679 non-instantiated units of all unit types (except for slice
680 units themselves see below). Instance units are by default
681 placed in a subslice of
<filename>system.slice
</filename>
682 that is named after the template name.
</para>
684 <para>This option may be used to arrange systemd units in a
685 hierarchy of slices each of which might have resource
686 settings applied.
</para>
688 <para>For units of type slice, the only accepted value for
689 this setting is the parent slice. Since the name of a slice
690 unit implies the parent slice, it is hence redundant to ever
691 set this parameter directly for slice units.
</para>
693 <para>Special care should be taken when relying on the default slice assignment in templated service units
694 that have
<varname>DefaultDependencies=no
</varname> set, see
695 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>, section
696 "Automatic Dependencies" for details.
</para>
702 <term><varname>Delegate=
</varname></term>
705 <para>Turns on delegation of further resource control
706 partitioning to processes of the unit. For unprivileged
707 services (i.e. those using the
<varname>User=
</varname>
708 setting), this allows processes to create a subhierarchy
709 beneath its control group path. For privileged services and
710 scopes, this ensures the processes will have all control
711 group controllers enabled.
</para>
719 <title>See Also
</title>
721 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
722 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
723 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
724 <citerefentry><refentrytitle>systemd.slice
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
725 <citerefentry><refentrytitle>systemd.scope
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
726 <citerefentry><refentrytitle>systemd.socket
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
727 <citerefentry><refentrytitle>systemd.mount
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
728 <citerefentry><refentrytitle>systemd.swap
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
729 <citerefentry><refentrytitle>systemd.directives
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
730 <citerefentry><refentrytitle>systemd.special
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
731 The documentation for control groups and specific controllers in the Linux kernel:
732 <ulink url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt">cgroups.txt
</ulink>,
733 <ulink url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/cpuacct.txt">cpuacct.txt
</ulink>,
734 <ulink url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt">memory.txt
</ulink>,
735 <ulink url=
"https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt">blkio-controller.txt
</ulink>.