2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
6 <refentry id=
"systemd.resource-control" xmlns:
xi=
"http://www.w3.org/2001/XInclude">
8 <title>systemd.resource-control
</title>
9 <productname>systemd
</productname>
13 <refentrytitle>systemd.resource-control
</refentrytitle>
14 <manvolnum>5</manvolnum>
18 <refname>systemd.resource-control
</refname>
19 <refpurpose>Resource control unit settings
</refpurpose>
24 <filename><replaceable>slice
</replaceable>.slice
</filename>,
25 <filename><replaceable>scope
</replaceable>.scope
</filename>,
26 <filename><replaceable>service
</replaceable>.service
</filename>,
27 <filename><replaceable>socket
</replaceable>.socket
</filename>,
28 <filename><replaceable>mount
</replaceable>.mount
</filename>,
29 <filename><replaceable>swap
</replaceable>.swap
</filename>
34 <title>Description
</title>
36 <para>Unit configuration files for services, slices, scopes, sockets, mount points, and swap devices share a subset
37 of configuration options for resource control of spawned processes. Internally, this relies on the Linux Control
38 Groups (cgroups) kernel concept for organizing processes in a hierarchical tree of named groups for the purpose of
39 resource management.
</para>
41 <para>This man page lists the configuration options shared by
42 those six unit types. See
43 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
44 for the common options of all unit configuration files, and
45 <citerefentry><refentrytitle>systemd.slice
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
46 <citerefentry><refentrytitle>systemd.scope
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
47 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
48 <citerefentry><refentrytitle>systemd.socket
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
49 <citerefentry><refentrytitle>systemd.mount
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
51 <citerefentry><refentrytitle>systemd.swap
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
52 for more information on the specific unit configuration files. The
53 resource control configuration options are configured in the
54 [Slice], [Scope], [Service], [Socket], [Mount], or [Swap]
55 sections, depending on the unit type.
</para>
57 <para>In addition, options which control resources available to programs
58 <emphasis>executed
</emphasis> by systemd are listed in
59 <citerefentry><refentrytitle>systemd.exec
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
60 Those options complement options listed here.
</para>
63 url=
"https://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface">New
64 Control Group Interfaces
</ulink> for an introduction on how to make
65 use of resource control APIs from programs.
</para>
68 <title>Setting resource controls for a group of related units
</title>
71 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>, the
72 settings listed here may be set through the main file of a unit and drop-in snippets in
73 <filename index=
"false">*.d/
</filename> directories. The list of directories searched for drop-ins
74 includes names formed by repeatedly truncating the unit name after all dashes. This is particularly
75 convenient to set resource limits for a group of units with similar names.
</para>
77 <para>For example, every user gets their own slice
78 <filename>user-
<replaceable>nnn
</replaceable>.slice
</filename>. Drop-ins with local configuration that
79 affect user
1000 may be placed in
80 <filename index=
"false">/etc/systemd/system/user-
1000.slice
</filename>,
81 <filename index=
"false">/etc/systemd/system/user-
1000.slice.d/*.conf
</filename>, but also
82 <filename index=
"false">/etc/systemd/system/user-.slice.d/*.conf
</filename>. This last directory
83 applies to all user slices.
</para>
88 <title>Implicit Dependencies
</title>
90 <para>The following dependencies are implicitly added:
</para>
93 <listitem><para>Units with the
<varname>Slice=
</varname> setting set automatically acquire
94 <varname>Requires=
</varname> and
<varname>After=
</varname> dependencies on the specified
95 slice unit.
</para></listitem>
99 <!-- We don't have any default dependency here. -->
102 <title>Unified and Legacy Control Group Hierarchies
</title>
104 <para>The unified control group hierarchy is the new version of kernel control group interface, see
105 <ulink url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html">Control Groups v2
</ulink>.
106 Depending on the resource type, there are differences in resource control capabilities. Also, because of
107 interface changes, some resource types have separate set of options on the unified hierarchy.
</para>
115 <para><varname>CPUWeight=
</varname> and
<varname>StartupCPUWeight=
</varname> replace
116 <varname>CPUShares=
</varname> and
<varname>StartupCPUShares=
</varname>, respectively.
</para>
118 <para>The
<literal>cpuacct
</literal> controller does not exist separately on the unified hierarchy.
</para>
125 <para><varname>MemoryMax=
</varname> replaces
<varname>MemoryLimit=
</varname>.
<varname>MemoryLow=
</varname>
126 and
<varname>MemoryHigh=
</varname> are effective only on unified hierarchy.
</para>
133 <para><literal>IO
</literal>-prefixed settings are a superset of and replace
134 <literal>BlockIO
</literal>-prefixed ones. On unified hierarchy, IO resource control also applies
135 to buffered writes.
</para>
142 <para>To ease the transition, there is best-effort translation between the two versions of settings. For each
143 controller, if any of the settings for the unified hierarchy are present, all settings for the legacy hierarchy are
144 ignored. If the resulting settings are for the other type of hierarchy, the configurations are translated before
147 <para>Legacy control group hierarchy (see
<ulink
148 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/">Control Groups version
1</ulink>),
149 also called cgroup-v1, doesn't allow safe delegation of controllers to unprivileged processes. If the
150 system uses the legacy control group hierarchy, resource control is disabled for the systemd user
152 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
</para>
156 <title>Options
</title>
158 <para>Units of the types listed above can have settings
159 for resource control configuration:
</para>
161 <variablelist class='unit-directives'
>
164 <term><varname>CPUAccounting=
</varname></term>
167 <para>Turn on CPU usage accounting for this unit. Takes a
168 boolean argument. Note that turning on CPU accounting for
169 one unit will also implicitly turn it on for all units
170 contained in the same slice and for all its parent slices
171 and the units contained therein. The system default for this
172 setting may be controlled with
173 <varname>DefaultCPUAccounting=
</varname> in
174 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
179 <term><varname>CPUWeight=
<replaceable>weight
</replaceable></varname></term>
180 <term><varname>StartupCPUWeight=
<replaceable>weight
</replaceable></varname></term>
183 <para>Assign the specified CPU time weight to the processes executed, if the unified control group
184 hierarchy is used on the system. These options take an integer value and control the
185 <literal>cpu.weight
</literal> control group attribute. The allowed range is
1 to
10000. Defaults to
186 100. For details about this control group attribute, see
<ulink
187 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html">Control Groups v2
</ulink>
188 and
<ulink url=
"https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html">CFS
189 Scheduler
</ulink>. The available CPU time is split up among all units within one slice relative to
190 their CPU time weight. A higher weight means more CPU time, a lower weight means less.
</para>
192 <para>While
<varname>StartupCPUWeight=
</varname> applies to the startup and shutdown phases 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 and shutdown phases. Using
<varname>StartupCPUWeight=
</varname> allows prioritizing specific services at
195 boot-up and shutdown differently than during normal runtime.
</para>
197 <para>These settings replace
<varname>CPUShares=
</varname> and
<varname>StartupCPUShares=
</varname>.
</para>
202 <term><varname>CPUQuota=
</varname></term>
205 <para>Assign the specified CPU time quota to the processes executed. Takes a percentage value, suffixed with
206 "%". The percentage specifies how much CPU time the unit shall get at maximum, relative to the total CPU time
207 available on one CPU. Use values
> 100% for allotting CPU time on more than one CPU. This controls the
208 <literal>cpu.max
</literal> attribute on the unified control group hierarchy and
209 <literal>cpu.cfs_quota_us
</literal> on legacy. For details about these control group attributes, see
<ulink
210 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html">Control Groups v2
</ulink> and
<ulink
211 url=
"https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt">sched-bwc.txt
</ulink>.
212 Setting
<varname>CPUQuota=
</varname> to an empty value unsets the quota.
</para>
214 <para>Example:
<varname>CPUQuota=
20%
</varname> ensures that the executed processes will never get more than
215 20% CPU time on one CPU.
</para>
221 <term><varname>CPUQuotaPeriodSec=
</varname></term>
224 <para>Assign the duration over which the CPU time quota specified by
<varname>CPUQuota=
</varname> is measured.
225 Takes a time duration value in seconds, with an optional suffix such as
"ms" for milliseconds (or
"s" for seconds.)
226 The default setting is
100ms. The period is clamped to the range supported by the kernel, which is [
1ms,
1000ms].
227 Additionally, the period is adjusted up so that the quota interval is also at least
1ms.
228 Setting
<varname>CPUQuotaPeriodSec=
</varname> to an empty value resets it to the default.
</para>
230 <para>This controls the second field of
<literal>cpu.max
</literal> attribute on the unified control group hierarchy
231 and
<literal>cpu.cfs_period_us
</literal> on legacy. For details about these control group attributes, see
232 <ulink url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html">Control Groups v2
</ulink> and
233 <ulink url=
"https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html">CFS Scheduler
</ulink>.
</para>
235 <para>Example:
<varname>CPUQuotaPeriodSec=
10ms
</varname> to request that the CPU quota is measured in periods of
10ms.
</para>
240 <term><varname>AllowedCPUs=
</varname></term>
241 <term><varname>StartupAllowedCPUs=
</varname></term>
244 <para>Restrict processes to be executed on specific CPUs. Takes a list of CPU indices or ranges separated by either
245 whitespace or commas. CPU ranges are specified by the lower and upper CPU indices separated by a dash.
</para>
247 <para>Setting
<varname>AllowedCPUs=
</varname> or
<varname>StartupAllowedCPUs=
</varname> doesn't guarantee that all
248 of the CPUs will be used by the processes as it may be limited by parent units. The effective configuration is
249 reported as
<varname>EffectiveCPUs=
</varname>.
</para>
251 <para>While
<varname>StartupAllowedCPUs=
</varname> applies to the startup and shutdown phases of the system,
252 <varname>AllowedCPUs=
</varname> applies to normal runtime of the system, and if the former is not set also to
253 the startup and shutdown phases. Using
<varname>StartupAllowedCPUs=
</varname> allows prioritizing specific services at
254 boot-up and shutdown differently than during normal runtime.
</para>
256 <para>This setting is supported only with the unified control group hierarchy.
</para>
261 <term><varname>AllowedMemoryNodes=
</varname></term>
262 <term><varname>StartupAllowedMemoryNodes=
</varname></term>
265 <para>Restrict processes to be executed on specific memory NUMA nodes. Takes a list of memory NUMA nodes indices
266 or ranges separated by either whitespace or commas. Memory NUMA nodes ranges are specified by the lower and upper
267 NUMA nodes indices separated by a dash.
</para>
269 <para>Setting
<varname>AllowedMemoryNodes=
</varname> or
<varname>StartupAllowedMemoryNodes=
</varname> doesn't
270 guarantee that all of the memory NUMA nodes will be used by the processes as it may be limited by parent units.
271 The effective configuration is reported as
<varname>EffectiveMemoryNodes=
</varname>.
</para>
273 <para>While
<varname>StartupAllowedMemoryNodes=
</varname> applies to the startup and shutdown phases of the system,
274 <varname>AllowedMemoryNodes=
</varname> applies to normal runtime of the system, and if the former is not set also to
275 the startup and shutdown phases. Using
<varname>StartupAllowedMemoryNodes=
</varname> allows prioritizing specific services at
276 boot-up and shutdown differently than during normal runtime.
</para>
278 <para>This setting is supported only with the unified control group hierarchy.
</para>
283 <term><varname>MemoryAccounting=
</varname></term>
286 <para>Turn on process and kernel memory accounting for this
287 unit. Takes a boolean argument. Note that turning on memory
288 accounting for one unit will also implicitly turn it on for
289 all units contained in the same slice and for all its parent
290 slices and the units contained therein. The system default
291 for this setting may be controlled with
292 <varname>DefaultMemoryAccounting=
</varname> in
293 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
298 <term><varname>MemoryMin=
<replaceable>bytes
</replaceable></varname>,
<varname>MemoryLow=
<replaceable>bytes
</replaceable></varname></term>
301 <para>Specify the memory usage protection of the executed processes in this unit.
302 When reclaiming memory, the unit is treated as if it was using less memory resulting in memory
303 to be preferentially reclaimed from unprotected units.
304 Using
<varname>MemoryLow=
</varname> results in a weaker protection where memory may still
305 be reclaimed to avoid invoking the OOM killer in case there is no other reclaimable memory.
</para>
307 For a protection to be effective, it is generally required to set a corresponding
308 allocation on all ancestors, which is then distributed between children
309 (with the exception of the root slice).
310 Any
<varname>MemoryMin=
</varname> or
<varname>MemoryLow=
</varname> allocation that is not
311 explicitly distributed to specific children is used to create a shared protection for all children.
312 As this is a shared protection, the children will freely compete for the memory.
</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
317 system. If assigned the special value
<literal>infinity
</literal>, all available memory is protected, which may be
318 useful in order to always inherit all of the protection afforded by ancestors.
319 This controls the
<literal>memory.min
</literal> or
<literal>memory.low
</literal> control group attribute.
320 For details about this control group attribute, see
<ulink
321 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-files">Memory Interface Files
</ulink>.
</para>
323 <para>This setting is supported only if the unified control group hierarchy is used and disables
324 <varname>MemoryLimit=
</varname>.
</para>
326 <para>Units may have their children use a default
<literal>memory.min
</literal> or
327 <literal>memory.low
</literal> value by specifying
<varname>DefaultMemoryMin=
</varname> or
328 <varname>DefaultMemoryLow=
</varname>, which has the same semantics as
329 <varname>MemoryMin=
</varname> and
<varname>MemoryLow=
</varname>.
330 This setting does not affect
<literal>memory.min
</literal> or
<literal>memory.low
</literal>
332 Using it to set a default child allocation is only useful on kernels older than
5.7,
333 which do not support the
<literal>memory_recursiveprot
</literal> cgroup2 mount option.
</para>
338 <term><varname>MemoryHigh=
<replaceable>bytes
</replaceable></varname></term>
341 <para>Specify the throttling limit on memory usage of the executed processes in this unit. Memory usage may go
342 above the limit if unavoidable, but the processes are heavily slowed down and memory is taken away
343 aggressively in such cases. This is the main mechanism to control memory usage of a unit.
</para>
345 <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
346 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base
1024), respectively. Alternatively, a
347 percentage value may be specified, which is taken relative to the installed physical memory on the
348 system. If assigned the
349 special value
<literal>infinity
</literal>, no memory throttling is applied. This controls the
350 <literal>memory.high
</literal> control group attribute. For details about this control group attribute, see
351 <ulink url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-files">Memory Interface Files
</ulink>.
</para>
353 <para>This setting is supported only if the unified control group hierarchy is used and disables
354 <varname>MemoryLimit=
</varname>.
</para>
359 <term><varname>MemoryMax=
<replaceable>bytes
</replaceable></varname></term>
362 <para>Specify the absolute limit on memory usage of the executed processes in this unit. If memory usage
363 cannot be contained under the limit, out-of-memory killer is invoked inside the unit. It is recommended to
364 use
<varname>MemoryHigh=
</varname> as the main control mechanism and use
<varname>MemoryMax=
</varname> as the
365 last line of defense.
</para>
367 <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
368 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base
1024), respectively. Alternatively, a
369 percentage value may be specified, which is taken relative to the installed physical memory on the system. If
370 assigned the special value
<literal>infinity
</literal>, no memory limit is applied. This controls the
371 <literal>memory.max
</literal> control group attribute. For details about this control group attribute, see
372 <ulink url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-files">Memory Interface Files
</ulink>.
</para>
374 <para>This setting replaces
<varname>MemoryLimit=
</varname>.
</para>
379 <term><varname>MemorySwapMax=
<replaceable>bytes
</replaceable></varname></term>
382 <para>Specify the absolute limit on swap usage of the executed processes in this unit.
</para>
384 <para>Takes a swap size in bytes. If the value is suffixed with K, M, G or T, the specified swap size is
385 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base
1024), respectively. If assigned the
386 special value
<literal>infinity
</literal>, no swap limit is applied. This controls the
387 <literal>memory.swap.max
</literal> control group attribute. For details about this control group attribute,
388 see
<ulink url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-files">Memory Interface Files
</ulink>.
</para>
390 <para>This setting is supported only if the unified control group hierarchy is used and disables
391 <varname>MemoryLimit=
</varname>.
</para>
396 <term><varname>TasksAccounting=
</varname></term>
399 <para>Turn on task accounting for this unit. Takes a
400 boolean argument. If enabled, the system manager will keep
401 track of the number of tasks in the unit. The number of
402 tasks accounted this way includes both kernel threads and
403 userspace processes, with each thread counting
404 individually. Note that turning on tasks accounting for one
405 unit will also implicitly turn it on for all units contained
406 in the same slice and for all its parent slices and the
407 units contained therein. The system default for this setting
408 may be controlled with
409 <varname>DefaultTasksAccounting=
</varname> in
410 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
415 <term><varname>TasksMax=
<replaceable>N
</replaceable></varname></term>
418 <para>Specify the maximum number of tasks that may be created in the unit. This ensures that the number of
419 tasks accounted for the unit (see above) stays below a specific limit. This either takes an absolute number
420 of tasks or a percentage value that is taken relative to the configured maximum number of tasks on the
421 system. If assigned the special value
<literal>infinity
</literal>, no tasks limit is applied. This controls
422 the
<literal>pids.max
</literal> control group attribute. For details about this control group attribute, see
423 <ulink url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/pids.html">Process Number Controller
</ulink>.
426 <para>The system default for this setting may be controlled with
427 <varname>DefaultTasksMax=
</varname> in
428 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
433 <term><varname>IOAccounting=
</varname></term>
436 <para>Turn on Block I/O accounting for this unit, if the unified control group hierarchy is used on the
437 system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly
438 turn it on for all units contained in the same slice and all for its parent slices and the units contained
439 therein. The system default for this setting may be controlled with
<varname>DefaultIOAccounting=
</varname>
441 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
443 <para>This setting replaces
<varname>BlockIOAccounting=
</varname> and disables settings prefixed with
444 <varname>BlockIO
</varname> or
<varname>StartupBlockIO
</varname>.
</para>
449 <term><varname>IOWeight=
<replaceable>weight
</replaceable></varname></term>
450 <term><varname>StartupIOWeight=
<replaceable>weight
</replaceable></varname></term>
453 <para>Set the default overall block I/O weight for the executed processes, if the unified control
454 group hierarchy is used on the system. Takes a single weight value (between
1 and
10000) to set the
455 default block I/O weight. This controls the
<literal>io.weight
</literal> control group attribute,
456 which defaults to
100. For details about this control group attribute, see
<ulink
457 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files">IO
458 Interface Files
</ulink>. The available I/O bandwidth is split up among all units within one slice
459 relative to their block I/O weight. A higher weight means more I/O bandwidth, a lower weight means
462 <para>While
<varname>StartupIOWeight=
</varname> applies
463 to the startup and shutdown phases of the system,
464 <varname>IOWeight=
</varname> applies to the later runtime of
465 the system, and if the former is not set also to the startup
466 and shutdown phases. This allows prioritizing specific services at boot-up
467 and shutdown differently than during runtime.
</para>
469 <para>These settings replace
<varname>BlockIOWeight=
</varname> and
<varname>StartupBlockIOWeight=
</varname>
470 and disable settings prefixed with
<varname>BlockIO
</varname> or
<varname>StartupBlockIO
</varname>.
</para>
475 <term><varname>IODeviceWeight=
<replaceable>device
</replaceable> <replaceable>weight
</replaceable></varname></term>
478 <para>Set the per-device overall block I/O weight for the executed processes, if the unified control group
479 hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify
480 the device specific weight value, between
1 and
10000. (Example:
<literal>/dev/sda
1000</literal>). The file
481 path may be specified as path to a block device node or as any other file, in which case the backing block
482 device of the file system of the file is determined. This controls the
<literal>io.weight
</literal> control
483 group attribute, which defaults to
100. Use this option multiple times to set weights for multiple devices.
484 For details about this control group attribute, see
<ulink
485 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files">IO Interface Files
</ulink>.
</para>
487 <para>This setting replaces
<varname>BlockIODeviceWeight=
</varname> and disables settings prefixed with
488 <varname>BlockIO
</varname> or
<varname>StartupBlockIO
</varname>.
</para>
490 <para>The specified device node should reference a block device that has an I/O scheduler
491 associated, i.e. should not refer to partition or loopback block devices, but to the originating,
492 physical device. When a path to a regular file or directory is specified it is attempted to
493 discover the correct originating device backing the file system of the specified path. This works
494 correctly only for simpler cases, where the file system is directly placed on a partition or
495 physical block device, or where simple
1:
1 encryption using dm-crypt/LUKS is used. This discovery
496 does not cover complex storage and in particular RAID and volume management storage devices.
</para>
501 <term><varname>IOReadBandwidthMax=
<replaceable>device
</replaceable> <replaceable>bytes
</replaceable></varname></term>
502 <term><varname>IOWriteBandwidthMax=
<replaceable>device
</replaceable> <replaceable>bytes
</replaceable></varname></term>
505 <para>Set the per-device overall block I/O bandwidth maximum limit for the executed processes, if the unified
506 control group hierarchy is used on the system. This limit is not work-conserving and the executed processes
507 are not allowed to use more even if the device has idle capacity. Takes a space-separated pair of a file
508 path and a bandwidth value (in bytes per second) to specify the device specific bandwidth. The file path may
509 be a path to a block device node, or as any other file in which case the backing block device of the file
510 system of the file is used. If the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is
511 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes, respectively, to the base of
1000. (Example:
512 "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the
<literal>io.max
</literal> control
513 group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For details
514 about this control group attribute, see
<ulink
515 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files">IO Interface Files
</ulink>.
518 <para>These settings replace
<varname>BlockIOReadBandwidth=
</varname> and
519 <varname>BlockIOWriteBandwidth=
</varname> and disable settings prefixed with
<varname>BlockIO
</varname> or
520 <varname>StartupBlockIO
</varname>.
</para>
522 <para>Similar restrictions on block device discovery as for
<varname>IODeviceWeight=
</varname> apply, see above.
</para>
527 <term><varname>IOReadIOPSMax=
<replaceable>device
</replaceable> <replaceable>IOPS
</replaceable></varname></term>
528 <term><varname>IOWriteIOPSMax=
<replaceable>device
</replaceable> <replaceable>IOPS
</replaceable></varname></term>
531 <para>Set the per-device overall block I/O IOs-Per-Second maximum limit for the executed processes, if the
532 unified control group hierarchy is used on the system. This limit is not work-conserving and the executed
533 processes are not allowed to use more even if the device has idle capacity. Takes a space-separated pair of
534 a file path and an IOPS value to specify the device specific IOPS. The file path may be a path to a block
535 device node, or as any other file in which case the backing block device of the file system of the file is
536 used. If the IOPS is suffixed with K, M, G, or T, the specified IOPS is parsed as KiloIOPS, MegaIOPS,
537 GigaIOPS, or TeraIOPS, respectively, to the base of
1000. (Example:
538 "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 1K"). This controls the
<literal>io.max
</literal> control
539 group attributes. Use this option multiple times to set IOPS limits for multiple devices. For details about
540 this control group attribute, see
<ulink
541 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files">IO Interface Files
</ulink>.
544 <para>These settings are supported only if the unified control group hierarchy is used and disable settings
545 prefixed with
<varname>BlockIO
</varname> or
<varname>StartupBlockIO
</varname>.
</para>
547 <para>Similar restrictions on block device discovery as for
<varname>IODeviceWeight=
</varname> apply, see above.
</para>
552 <term><varname>IODeviceLatencyTargetSec=
<replaceable>device
</replaceable> <replaceable>target
</replaceable></varname></term>
555 <para>Set the per-device average target I/O latency for the executed processes, if the unified control group
556 hierarchy is used on the system. Takes a file path and a timespan separated by a space to specify
557 the device specific latency target. (Example:
"/dev/sda 25ms"). The file path may be specified
558 as path to a block device node or as any other file, in which case the backing block device of the file
559 system of the file is determined. This controls the
<literal>io.latency
</literal> control group
560 attribute. Use this option multiple times to set latency target for multiple devices. For details about this
561 control group attribute, see
<ulink
562 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files">IO Interface Files
</ulink>.
</para>
564 <para>Implies
<literal>IOAccounting=yes
</literal>.
</para>
566 <para>These settings are supported only if the unified control group hierarchy is used.
</para>
568 <para>Similar restrictions on block device discovery as for
<varname>IODeviceWeight=
</varname> apply, see above.
</para>
573 <term><varname>IPAccounting=
</varname></term>
576 <para>Takes a boolean argument. If true, turns on IPv4 and IPv6 network traffic accounting for packets sent
577 or received by the unit. When this option is turned on, all IPv4 and IPv6 sockets created by any process of
578 the unit are accounted for.
</para>
580 <para>When this option is used in socket units, it applies to all IPv4 and IPv6 sockets
581 associated with it (including both listening and connection sockets where this applies). Note that for
582 socket-activated services, this configuration setting and the accounting data of the service unit and the
583 socket unit are kept separate, and displayed separately. No propagation of the setting and the collected
584 statistics is done, in either direction. Moreover, any traffic sent or received on any of the socket unit's
585 sockets is accounted to the socket unit — and never to the service unit it might have activated, even if the
586 socket is used by it.
</para>
588 <para>The system default for this setting may be controlled with
<varname>DefaultIPAccounting=
</varname> in
589 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
594 <term><varname>IPAddressAllow=
<replaceable>ADDRESS[/PREFIXLENGTH]…
</replaceable></varname></term>
595 <term><varname>IPAddressDeny=
<replaceable>ADDRESS[/PREFIXLENGTH]…
</replaceable></varname></term>
598 <para>Turn on network traffic filtering for IP packets sent and received over
599 <constant>AF_INET
</constant> and
<constant>AF_INET6
</constant> sockets. Both directives take a
600 space separated list of IPv4 or IPv6 addresses, each optionally suffixed with an address prefix
601 length in bits after a
<literal>/
</literal> character. If the suffix is omitted, the address is
602 considered a host address, i.e. the filter covers the whole address (
32 bits for IPv4,
128 bits for
605 <para>The access lists configured with this option are applied to all sockets created by processes
606 of this unit (or in the case of socket units, associated with it). The lists are implicitly
607 combined with any lists configured for any of the parent slice units this unit might be a member
608 of. By default both access lists are empty. Both ingress and egress traffic is filtered by these
609 settings. In case of ingress traffic the source IP address is checked against these access lists,
610 in case of egress traffic the destination IP address is checked. The following rules are applied in
614 <listitem><para>Access is granted when the checked IP address matches an entry in the
615 <varname>IPAddressAllow=
</varname> list.
</para></listitem>
617 <listitem><para>Otherwise, access is denied when the checked IP address matches an entry in the
618 <varname>IPAddressDeny=
</varname> list.
</para></listitem>
620 <listitem><para>Otherwise, access is granted.
</para></listitem>
623 <para>In order to implement an allow-listing IP firewall, it is recommended to use a
624 <varname>IPAddressDeny=
</varname><constant>any
</constant> setting on an upper-level slice unit
625 (such as the root slice
<filename>-.slice
</filename> or the slice containing all system services
626 <filename>system.slice
</filename> – see
627 <citerefentry><refentrytitle>systemd.special
</refentrytitle><manvolnum>7</manvolnum></citerefentry>
628 for details on these slice units), plus individual per-service
<varname>IPAddressAllow=
</varname>
629 lines permitting network access to relevant services, and only them.
</para>
631 <para>Note that for socket-activated services, the IP access list configured on the socket unit
632 applies to all sockets associated with it directly, but not to any sockets created by the
633 ultimately activated services for it. Conversely, the IP access list configured for the service is
634 not applied to any sockets passed into the service via socket activation. Thus, it is usually a
635 good idea to replicate the IP access lists on both the socket and the service unit. Nevertheless,
636 it may make sense to maintain one list more open and the other one more restricted, depending on
639 <para>If these settings are used multiple times in the same unit the specified lists are combined. If an
640 empty string is assigned to these settings the specific access list is reset and all previous settings undone.
</para>
642 <para>In place of explicit IPv4 or IPv6 address and prefix length specifications a small set of symbolic
643 names may be used. The following names are defined:
</para>
646 <title>Special address/network names
</title>
649 <colspec colname='name'
/>
650 <colspec colname='definition'
/>
651 <colspec colname='meaning'
/>
655 <entry>Symbolic Name
</entry>
656 <entry>Definition
</entry>
657 <entry>Meaning
</entry>
663 <entry><constant>any
</constant></entry>
664 <entry>0.0.0.0/
0 ::/
0</entry>
665 <entry>Any host
</entry>
669 <entry><constant>localhost
</constant></entry>
670 <entry>127.0.0.0/
8 ::
1/
128</entry>
671 <entry>All addresses on the local loopback
</entry>
675 <entry><constant>link-local
</constant></entry>
676 <entry>169.254.0.0/
16 fe80::/
64</entry>
677 <entry>All link-local IP addresses
</entry>
681 <entry><constant>multicast
</constant></entry>
682 <entry>224.0.0.0/
4 ff00::/
8</entry>
683 <entry>All IP multicasting addresses
</entry>
689 <para>Note that these settings might not be supported on some systems (for example if eBPF control group
690 support is not enabled in the underlying kernel or container manager). These settings will have no effect in
691 that case. If compatibility with such systems is desired it is hence recommended to not exclusively rely on
692 them for IP security.
</para>
697 <term><varname>IPIngressFilterPath=
<replaceable>BPF_FS_PROGRAM_PATH
</replaceable></varname></term>
698 <term><varname>IPEgressFilterPath=
<replaceable>BPF_FS_PROGRAM_PATH
</replaceable></varname></term>
701 <para>Add custom network traffic filters implemented as BPF programs, applying to all IP packets
702 sent and received over
<constant>AF_INET
</constant> and
<constant>AF_INET6
</constant> sockets.
703 Takes an absolute path to a pinned BPF program in the BPF virtual filesystem (
<filename>/sys/fs/bpf/
</filename>).
706 <para>The filters configured with this option are applied to all sockets created by processes
707 of this unit (or in the case of socket units, associated with it). The filters are loaded in addition
708 to filters any of the parent slice units this unit might be a member of as well as any
709 <varname>IPAddressAllow=
</varname> and
<varname>IPAddressDeny=
</varname> filters in any of these units.
710 By default there are no filters specified.
</para>
712 <para>If these settings are used multiple times in the same unit all the specified programs are attached. If an
713 empty string is assigned to these settings the program list is reset and all previous specified programs ignored.
</para>
715 <para>If the path
<replaceable>BPF_FS_PROGRAM_PATH
</replaceable> in
<varname>IPIngressFilterPath=
</varname> assignment
716 is already being handled by
<varname>BPFProgram=
</varname> ingress hook, e.g.
717 <varname>BPFProgram=
</varname><constant>ingress
</constant>:
<replaceable>BPF_FS_PROGRAM_PATH
</replaceable>,
718 the assignment will be still considered valid and the program will be attached to a cgroup. Same for
719 <varname>IPEgressFilterPath=
</varname> path and
<constant>egress
</constant> hook.
</para>
721 <para>Note that for socket-activated services, the IP filter programs configured on the socket unit apply to
722 all sockets associated with it directly, but not to any sockets created by the ultimately activated services
723 for it. Conversely, the IP filter programs configured for the service are not applied to any sockets passed into
724 the service via socket activation. Thus, it is usually a good idea, to replicate the IP filter programs on both
725 the socket and the service unit, however it often makes sense to maintain one configuration more open and the other
726 one more restricted, depending on the usecase.
</para>
728 <para>Note that these settings might not be supported on some systems (for example if eBPF control group
729 support is not enabled in the underlying kernel or container manager). These settings will fail the service in
730 that case. If compatibility with such systems is desired it is hence recommended to attach your filter manually
731 (requires
<varname>Delegate=
</varname><constant>yes
</constant>) instead of using this setting.
</para>
736 <term><varname>BPFProgram=
<replaceable>type
</replaceable><constant>:
</constant><replaceable>program-path
</replaceable></varname></term>
738 <para>Add a custom cgroup BPF program.
</para>
740 <para><varname>BPFProgram=
</varname> allows attaching BPF hooks to the cgroup of a systemd unit.
741 (This generalizes the functionality exposed via
<varname>IPEgressFilterPath=
</varname> for egress and
742 <varname>IPIngressFilterPath=
</varname> for ingress.)
743 Cgroup-bpf hooks in the form of BPF programs loaded to the BPF filesystem are attached with cgroup-bpf attach
744 flags determined by the unit. For details about attachment types and flags see
<ulink
745 url=
"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/include/uapi/linux/bpf.h"/>.
746 For general BPF documentation please refer to
<ulink url=
"https://www.kernel.org/doc/html/latest/bpf/index.html"/>.
</para>
748 <para>The specification of BPF program consists of a
<replaceable>type
</replaceable> followed by a
749 <replaceable>program-path
</replaceable> with
<literal>:
</literal> as the separator:
750 <replaceable>type
</replaceable><constant>:
</constant><replaceable>program-path
</replaceable>.
</para>
752 <para><replaceable>type
</replaceable> is the string name of BPF attach type also used in
753 <command>bpftool
</command>.
<replaceable>type
</replaceable> can be one of
<constant>egress
</constant>,
754 <constant>ingress
</constant>,
<constant>sock_create
</constant>,
<constant>sock_ops
</constant>,
755 <constant>device
</constant>,
<constant>bind4
</constant>,
<constant>bind6
</constant>,
756 <constant>connect4
</constant>,
<constant>connect6
</constant>,
<constant>post_bind4
</constant>,
757 <constant>post_bind6
</constant>,
<constant>sendmsg4
</constant>,
<constant>sendmsg6
</constant>,
758 <constant>sysctl
</constant>,
<constant>recvmsg4
</constant>,
<constant>recvmsg6
</constant>,
759 <constant>getsockopt
</constant>,
<constant>setsockopt
</constant>.
</para>
761 <para>Setting
<varname>BPFProgram=
</varname> to an empty value makes previous assignments ineffective.
</para>
762 <para>Multiple assignments of the same
<replaceable>type
</replaceable>:
<replaceable>program-path
</replaceable>
763 value have the same effect as a single assignment: the program with the path
<replaceable>program-path
</replaceable>
764 will be attached to cgroup hook
<replaceable>type
</replaceable> just once.
</para>
765 <para>If BPF
<constant>egress
</constant> pinned to
<replaceable>program-path
</replaceable> path is already being
766 handled by
<varname>IPEgressFilterPath=
</varname>,
<varname>BPFProgram=
</varname>
767 assignment will be considered valid and
<varname>BPFProgram=
</varname> will be attached to a cgroup.
768 Similarly for
<constant>ingress
</constant> hook and
<varname>IPIngressFilterPath=
</varname> assignment.
</para>
770 <para>BPF programs passed with
<varname>BPFProgram=
</varname> are attached to the cgroup of a unit with BPF
771 attach flag
<constant>multi
</constant>, that allows further attachments of the same
772 <replaceable>type
</replaceable> within cgroup hierarchy topped by the unit cgroup.
</para>
774 <para>Examples:
<programlisting>
775 BPFProgram=egress:/sys/fs/bpf/egress-hook
776 BPFProgram=bind6:/sys/fs/bpf/sock-addr-hook
777 </programlisting></para>
782 <term><varname>SocketBindAllow=
<replaceable>bind-rule
</replaceable></varname></term>
783 <term><varname>SocketBindDeny=
<replaceable>bind-rule
</replaceable></varname></term>
786 <para>Allow or deny binding a socket address to a socket by matching it with the
<replaceable>bind-rule
</replaceable> and
787 applying a corresponding action if there is a match.
</para>
789 <para><replaceable>bind-rule
</replaceable> describes socket properties such as
<replaceable>address-family
</replaceable>,
790 <replaceable>transport-protocol
</replaceable> and
<replaceable>ip-ports
</replaceable>.
</para>
792 <para><replaceable>bind-rule
</replaceable> :=
793 { [
<replaceable>address-family
</replaceable><constant>:
</constant>][
<replaceable>transport-protocol
</replaceable><constant>:
</constant>][
<replaceable>ip-ports
</replaceable>] |
<constant>any
</constant> }
</para>
795 <para><replaceable>address-family
</replaceable> := {
<constant>ipv4
</constant> |
<constant>ipv6
</constant> }
</para>
797 <para><replaceable>transport-protocol
</replaceable> := {
<constant>tcp
</constant> |
<constant>udp
</constant> }
</para>
799 <para><replaceable>ip-ports
</replaceable> := {
<replaceable>ip-port
</replaceable> |
<replaceable>ip-port-range
</replaceable> }
</para>
801 <para>An optional
<replaceable>address-family
</replaceable> expects
<constant>ipv4
</constant> or
<constant>ipv6
</constant> values.
802 If not specified, a rule will be matched for both IPv4 and IPv6 addresses and applied depending on other socket fields, e.g.
<replaceable>transport-protocol
</replaceable>,
803 <replaceable>ip-port
</replaceable>.
</para>
805 <para>An optional
<replaceable>transport-protocol
</replaceable> expects
<constant>tcp
</constant> or
<constant>udp
</constant> transport protocol names.
806 If not specified, a rule will be matched for any transport protocol.
</para>
808 <para>An optional
<replaceable>ip-port
</replaceable> value must lie within
1…
65535 interval inclusively, i.e.
809 dynamic port
<constant>0</constant> is not allowed. A range of sequential ports is described by
810 <replaceable>ip-port-range
</replaceable> :=
<replaceable>ip-port-low
</replaceable><constant>-
</constant><replaceable>ip-port-high
</replaceable>,
811 where
<replaceable>ip-port-low
</replaceable> is smaller than or equal to
<replaceable>ip-port-high
</replaceable>
812 and both are within
1…
65535 inclusively.
</para>
814 <para>A special value
<constant>any
</constant> can be used to apply a rule to any address family, transport protocol and any port with a positive value.
</para>
816 <para>To allow multiple rules assign
<varname>SocketBindAllow=
</varname> or
<varname>SocketBindDeny=
</varname> multiple times.
817 To clear the existing assignments pass an empty
<varname>SocketBindAllow=
</varname> or
<varname>SocketBindDeny=
</varname>
820 <para>For each of
<varname>SocketBindAllow=
</varname> and
<varname>SocketBindDeny=
</varname>, maximum allowed number of assignments is
821 <constant>128</constant>.
</para>
824 <listitem><para>Binding to a socket is allowed when a socket address matches an entry in the
825 <varname>SocketBindAllow=
</varname> list.
</para></listitem>
827 <listitem><para>Otherwise, binding is denied when the socket address matches an entry in the
828 <varname>SocketBindDeny=
</varname> list.
</para></listitem>
830 <listitem><para>Otherwise, binding is allowed.
</para></listitem>
833 <para>The feature is implemented with
<constant>cgroup/bind4
</constant> and
<constant>cgroup/bind6
</constant> cgroup-bpf hooks.
</para>
834 <para>Examples:
<programlisting>…
835 # Allow binding IPv6 socket addresses with a port greater than or equal to
10000.
837 SocketBindAllow=ipv6:
10000-
65535
840 # Allow binding IPv4 and IPv6 socket addresses with
1234 and
4321 ports.
846 # Deny binding IPv6 socket addresses.
850 # Deny binding IPv4 and IPv6 socket addresses.
854 # Allow binding only over TCP
859 # Allow binding only over IPv6/TCP
861 SocketBindAllow=ipv6:tcp
864 # Allow binding ports within
10000-
65535 range over IPv4/UDP.
866 SocketBindAllow=ipv4:udp:
10000-
65535
868 …
</programlisting></para>
873 <term><varname>RestrictNetworkInterfaces=
</varname></term>
876 <para>Takes a list of space-separated network interface names. This option restricts the network
877 interfaces that processes of this unit can use. By default processes can only use the network interfaces
878 listed (allow-list). If the first character of the rule is
<literal>~
</literal>, the effect is inverted:
879 the processes can only use network interfaces not listed (deny-list).
882 <para>This option can appear multiple times, in which case the network interface names are merged. If the
883 empty string is assigned the set is reset, all prior assignments will have not effect.
886 <para>If you specify both types of this option (i.e. allow-listing and deny-listing), the first encountered
887 will take precedence and will dictate the default action (allow vs deny). Then the next occurrences of this
888 option will add or delete the listed network interface names from the set, depending of its type and the
892 <para>The loopback interface (
"lo") is not treated in any special way, you have to configure it explicitly
895 <para>Example
1: allow-list
897 RestrictNetworkInterfaces=eth1
898 RestrictNetworkInterfaces=eth2
</programlisting>
899 Programs in the unit will be only able to use the eth1 and eth2 network
903 <para>Example
2: deny-list
905 RestrictNetworkInterfaces=~eth1 eth2
</programlisting>
906 Programs in the unit will be able to use any network interface but eth1 and eth2.
909 <para>Example
3: mixed
911 RestrictNetworkInterfaces=eth1 eth2
912 RestrictNetworkInterfaces=~eth1
</programlisting>
913 Programs in the unit will be only able to use the eth2 network interface.
919 <term><varname>DeviceAllow=
</varname></term>
922 <para>Control access to specific device nodes by the executed processes. Takes two space-separated
923 strings: a device node specifier followed by a combination of
<constant>r
</constant>,
924 <constant>w
</constant>,
<constant>m
</constant> to control
<emphasis>r
</emphasis>eading,
925 <emphasis>w
</emphasis>riting, or creation of the specific device node(s) by the unit
926 (
<emphasis>m
</emphasis>knod), respectively. On cgroup-v1 this controls the
927 <literal>devices.allow
</literal> control group attribute. For details about this control group
928 attribute, see
<ulink
929 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/devices.html">Device Whitelist Controller
</ulink>.
930 In the unified cgroup hierarchy this functionality is implemented using eBPF filtering.
</para>
932 <para>When access to
<emphasis>all
</emphasis> physical devices should be disallowed,
933 <varname>PrivateDevices=
</varname> may be used instead. See
934 <citerefentry><refentrytitle>systemd.exec
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
937 <para>The device node specifier is either a path to a device node in the file system, starting with
938 <filename>/dev/
</filename>, or a string starting with either
<literal>char-
</literal> or
939 <literal>block-
</literal> followed by a device group name, as listed in
940 <filename>/proc/devices
</filename>. The latter is useful to allow-list all current and future
941 devices belonging to a specific device group at once. The device group is matched according to
942 filename globbing rules, you may hence use the
<literal>*
</literal> and
<literal>?
</literal>
943 wildcards. (Note that such globbing wildcards are not available for device node path
944 specifications!) In order to match device nodes by numeric major/minor, use device node paths in
945 the
<filename>/dev/char/
</filename> and
<filename>/dev/block/
</filename> directories. However,
946 matching devices by major/minor is generally not recommended as assignments are neither stable nor
947 portable between systems or different kernel versions.
</para>
949 <para>Examples:
<filename>/dev/sda5
</filename> is a path to a device node, referring to an ATA or
950 SCSI block device.
<literal>char-pts
</literal> and
<literal>char-alsa
</literal> are specifiers for
951 all pseudo TTYs and all ALSA sound devices, respectively.
<literal>char-cpu/*
</literal> is a
952 specifier matching all CPU related device groups.
</para>
954 <para>Note that allow lists defined this way should only reference device groups which are
955 resolvable at the time the unit is started. Any device groups not resolvable then are not added to
956 the device allow list. In order to work around this limitation, consider extending service units
957 with a pair of
<command>After=modprobe@xyz.service
</command> and
958 <command>Wants=modprobe@xyz.service
</command> lines that load the necessary kernel module
959 implementing the device group if missing.
960 Example:
<programlisting>…
962 Wants=modprobe@loop.service
963 After=modprobe@loop.service
966 DeviceAllow=block-loop
967 DeviceAllow=/dev/loop-control
968 …
</programlisting></para>
974 <term><varname>DevicePolicy=auto|closed|strict
</varname></term>
978 Control the policy for allowing device access:
982 <term><option>strict
</option></term>
984 <para>means to only allow types of access that are
985 explicitly specified.
</para>
990 <term><option>closed
</option></term>
992 <para>in addition, allows access to standard pseudo
994 <filename>/dev/null
</filename>,
995 <filename>/dev/zero
</filename>,
996 <filename>/dev/full
</filename>,
997 <filename>/dev/random
</filename>, and
998 <filename>/dev/urandom
</filename>.
1004 <term><option>auto
</option></term>
1007 in addition, allows access to all devices if no
1008 explicit
<varname>DeviceAllow=
</varname> is present.
1009 This is the default.
1018 <term><varname>Slice=
</varname></term>
1021 <para>The name of the slice unit to place the unit
1022 in. Defaults to
<filename>system.slice
</filename> for all
1023 non-instantiated units of all unit types (except for slice
1024 units themselves see below). Instance units are by default
1025 placed in a subslice of
<filename>system.slice
</filename>
1026 that is named after the template name.
</para>
1028 <para>This option may be used to arrange systemd units in a
1029 hierarchy of slices each of which might have resource
1030 settings applied.
</para>
1032 <para>For units of type slice, the only accepted value for
1033 this setting is the parent slice. Since the name of a slice
1034 unit implies the parent slice, it is hence redundant to ever
1035 set this parameter directly for slice units.
</para>
1037 <para>Special care should be taken when relying on the default slice assignment in templated service units
1038 that have
<varname>DefaultDependencies=no
</varname> set, see
1039 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>, section
1040 "Default Dependencies" for details.
</para>
1046 <term><varname>Delegate=
</varname></term>
1049 <para>Turns on delegation of further resource control partitioning to processes of the unit. Units where this
1050 is enabled may create and manage their own private subhierarchy of control groups below the control group of
1051 the unit itself. For unprivileged services (i.e. those using the
<varname>User=
</varname> setting) the unit's
1052 control group will be made accessible to the relevant user. When enabled the service manager will refrain
1053 from manipulating control groups or moving processes below the unit's control group, so that a clear concept
1054 of ownership is established: the control group tree above the unit's control group (i.e. towards the root
1055 control group) is owned and managed by the service manager of the host, while the control group tree below
1056 the unit's control group is owned and managed by the unit itself. Takes either a boolean argument or a list
1057 of control group controller names. If true, delegation is turned on, and all supported controllers are
1058 enabled for the unit, making them available to the unit's processes for management. If false, delegation is
1059 turned off entirely (and no additional controllers are enabled). If set to a list of controllers, delegation
1060 is turned on, and the specified controllers are enabled for the unit. Note that additional controllers than
1061 the ones specified might be made available as well, depending on configuration of the containing slice unit
1062 or other units contained in it. Note that assigning the empty string will enable delegation, but reset the
1063 list of controllers, all assignments prior to this will have no effect. Defaults to false.
</para>
1065 <para>Note that controller delegation to less privileged code is only safe on the unified control group
1066 hierarchy. Accordingly, access to the specified controllers will not be granted to unprivileged services on
1067 the legacy hierarchy, even when requested.
</para>
1069 <xi:include href=
"supported-controllers.xml" xpointer=
"controllers-text" />
1071 <para>Not all of these controllers are available on all kernels however, and some are
1072 specific to the unified hierarchy while others are specific to the legacy hierarchy. Also note that the
1073 kernel might support further controllers, which aren't covered here yet as delegation is either not supported
1074 at all for them or not defined cleanly.
</para>
1076 <para>For further details on the delegation model consult
<ulink
1077 url=
"https://systemd.io/CGROUP_DELEGATION">Control Group APIs and Delegation
</ulink>.
</para>
1082 <term><varname>DisableControllers=
</varname></term>
1085 <para>Disables controllers from being enabled for a unit's children. If a controller listed is already in use
1086 in its subtree, the controller will be removed from the subtree. This can be used to avoid child units being
1087 able to implicitly or explicitly enable a controller. Defaults to not disabling any controllers.
</para>
1089 <para>It may not be possible to successfully disable a controller if the unit or any child of the unit in
1090 question delegates controllers to its children, as any delegated subtree of the cgroup hierarchy is unmanaged
1093 <para>Multiple controllers may be specified, separated by spaces. You may also pass
1094 <varname>DisableControllers=
</varname> multiple times, in which case each new instance adds another controller
1095 to disable. Passing
<varname>DisableControllers=
</varname> by itself with no controller name present resets
1096 the disabled controller list.
</para>
1098 <xi:include href=
"supported-controllers.xml" xpointer=
"controllers-text" />
1103 <term><varname>ManagedOOMSwap=auto|kill
</varname></term>
1104 <term><varname>ManagedOOMMemoryPressure=auto|kill
</varname></term>
1108 <citerefentry><refentrytitle>systemd-oomd.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1109 will act on this unit's cgroups. Defaults to
<option>auto
</option>.
</para>
1111 <para>When set to
<option>kill
</option>, the unit becomes a candidate for monitoring by
1112 <command>systemd-oomd
</command>. If the cgroup passes the limits set by
1113 <citerefentry><refentrytitle>oomd.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry> or
1114 the unit configuration,
<command>systemd-oomd
</command> will select a descendant cgroup and send
1115 <constant>SIGKILL
</constant> to all of the processes under it. You can find more details on
1116 candidates and kill behavior at
1117 <citerefentry><refentrytitle>systemd-oomd.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1119 <citerefentry><refentrytitle>oomd.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
1121 <para>Setting either of these properties to
<option>kill
</option> will also result in
1122 <varname>After=
</varname> and
<varname>Wants=
</varname> dependencies on
1123 <filename>systemd-oomd.service
</filename> unless
<varname>DefaultDependencies=no
</varname>.
</para>
1125 <para>When set to
<option>auto
</option>,
<command>systemd-oomd
</command> will not actively use this
1126 cgroup's data for monitoring and detection. However, if an ancestor cgroup has one of these
1127 properties set to
<option>kill
</option>, a unit with
<option>auto
</option> can still be a candidate
1128 for
<command>systemd-oomd
</command> to terminate.
</para>
1133 <term><varname>ManagedOOMMemoryPressureLimit=
</varname></term>
1136 <para>Overrides the default memory pressure limit set by
1137 <citerefentry><refentrytitle>oomd.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
1138 this unit (cgroup). Takes a percentage value between
0% and
100%, inclusive. This property is
1139 ignored unless
<varname>ManagedOOMMemoryPressure=
</varname><option>kill
</option>. Defaults to
0%,
1140 which means to use the default set by
1141 <citerefentry><refentrytitle>oomd.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1147 <term><varname>ManagedOOMPreference=none|avoid|omit
</varname></term>
1150 <para>Allows deprioritizing or omitting this unit's cgroup as a candidate when
1151 <command>systemd-oomd
</command> needs to act. Requires support for extended attributes (see
1152 <citerefentry project='man-pages'
><refentrytitle>xattr
</refentrytitle><manvolnum>7</manvolnum></citerefentry>)
1153 in order to use
<option>avoid
</option> or
<option>omit
</option>. Additionally,
1154 <command>systemd-oomd
</command> will ignore these extended attributes if the unit's cgroup is not
1155 owned by the root user.
</para>
1157 <para>If this property is set to
<option>avoid
</option>, the service manager will convey this to
1158 <command>systemd-oomd
</command>, which will only select this cgroup if there are no other viable
1161 <para>If this property is set to
<option>omit
</option>, the service manager will convey this to
1162 <command>systemd-oomd
</command>, which will ignore this cgroup as a candidate and will not perform
1163 any actions on it.
</para>
1165 <para>It is recommended to use
<option>avoid
</option> and
<option>omit
</option> sparingly, as it
1166 can adversely affect
<command>systemd-oomd
</command>'s kill behavior. Also note that these extended
1167 attributes are not applied recursively to cgroups under this unit's cgroup.
</para>
1169 <para>Defaults to
<option>none
</option> which means
<command>systemd-oomd
</command> will rank this
1170 unit's cgroup as defined in
1171 <citerefentry><refentrytitle>systemd-oomd.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1172 and
<citerefentry><refentrytitle>oomd.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1180 <title>Deprecated Options
</title>
1182 <para>The following options are deprecated. Use the indicated superseding options instead:
</para>
1184 <variablelist class='unit-directives'
>
1187 <term><varname>CPUShares=
<replaceable>weight
</replaceable></varname></term>
1188 <term><varname>StartupCPUShares=
<replaceable>weight
</replaceable></varname></term>
1191 <para>Assign the specified CPU time share weight to the processes executed. These options take an integer
1192 value and control the
<literal>cpu.shares
</literal> control group attribute. The allowed range is
2 to
1193 262144. Defaults to
1024. For details about this control group attribute, see
<ulink
1194 url=
"https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html">CFS Scheduler
</ulink>.
1195 The available CPU time is split up among all units within one slice relative to their CPU time share
1198 <para>While
<varname>StartupCPUShares=
</varname> applies to the startup and shutdown phases of the system,
1199 <varname>CPUShares=
</varname> applies to normal runtime of the system, and if the former is not set also to
1200 the startup and shutdown phases. Using
<varname>StartupCPUShares=
</varname> allows prioritizing specific services at
1201 boot-up and shutdown differently than during normal runtime.
</para>
1203 <para>Implies
<literal>CPUAccounting=yes
</literal>.
</para>
1205 <para>These settings are deprecated. Use
<varname>CPUWeight=
</varname> and
1206 <varname>StartupCPUWeight=
</varname> instead.
</para>
1211 <term><varname>MemoryLimit=
<replaceable>bytes
</replaceable></varname></term>
1214 <para>Specify the limit on maximum memory usage of the executed processes. The limit specifies how much
1215 process and kernel memory can be used by tasks in this unit. Takes a memory size in bytes. If the value is
1216 suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or
1217 Terabytes (with the base
1024), respectively. Alternatively, a percentage value may be specified, which is
1218 taken relative to the installed physical memory on the system. If assigned the special value
1219 <literal>infinity
</literal>, no memory limit is applied. This controls the
1220 <literal>memory.limit_in_bytes
</literal> control group attribute. For details about this control group
1221 attribute, see
<ulink
1222 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/memory.html">Memory Resource Controller
</ulink>.
</para>
1224 <para>Implies
<literal>MemoryAccounting=yes
</literal>.
</para>
1226 <para>This setting is deprecated. Use
<varname>MemoryMax=
</varname> instead.
</para>
1231 <term><varname>BlockIOAccounting=
</varname></term>
1234 <para>Turn on Block I/O accounting for this unit, if the legacy control group hierarchy is used on the
1235 system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly
1236 turn it on for all units contained in the same slice and all for its parent slices and the units contained
1237 therein. The system default for this setting may be controlled with
1238 <varname>DefaultBlockIOAccounting=
</varname> in
1239 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
1241 <para>This setting is deprecated. Use
<varname>IOAccounting=
</varname> instead.
</para>
1246 <term><varname>BlockIOWeight=
<replaceable>weight
</replaceable></varname></term>
1247 <term><varname>StartupBlockIOWeight=
<replaceable>weight
</replaceable></varname></term>
1249 <listitem><para>Set the default overall block I/O weight for the executed processes, if the legacy control
1250 group hierarchy is used on the system. Takes a single weight value (between
10 and
1000) to set the default
1251 block I/O weight. This controls the
<literal>blkio.weight
</literal> control group attribute, which defaults to
1252 500. For details about this control group attribute, see
<ulink
1253 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html">Block IO Controller
</ulink>.
1254 The available I/O bandwidth is split up among all units within one slice relative to their block I/O
1257 <para>While
<varname>StartupBlockIOWeight=
</varname> only
1258 applies to the startup and shutdown phases of the system,
1259 <varname>BlockIOWeight=
</varname> applies to the later runtime
1260 of the system, and if the former is not set also to the
1261 startup and shutdown phases. This allows prioritizing specific services at
1262 boot-up and shutdown differently than during runtime.
</para>
1265 <literal>BlockIOAccounting=yes
</literal>.
</para>
1267 <para>These settings are deprecated. Use
<varname>IOWeight=
</varname> and
<varname>StartupIOWeight=
</varname>
1274 <term><varname>BlockIODeviceWeight=
<replaceable>device
</replaceable> <replaceable>weight
</replaceable></varname></term>
1277 <para>Set the per-device overall block I/O weight for the executed processes, if the legacy control group
1278 hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify
1279 the device specific weight value, between
10 and
1000. (Example:
"/dev/sda 500"). The file path may be
1280 specified as path to a block device node or as any other file, in which case the backing block device of the
1281 file system of the file is determined. This controls the
<literal>blkio.weight_device
</literal> control group
1282 attribute, which defaults to
1000. Use this option multiple times to set weights for multiple devices. For
1283 details about this control group attribute, see
<ulink
1284 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html">Block IO Controller
</ulink>.
</para>
1287 <literal>BlockIOAccounting=yes
</literal>.
</para>
1289 <para>This setting is deprecated. Use
<varname>IODeviceWeight=
</varname> instead.
</para>
1294 <term><varname>BlockIOReadBandwidth=
<replaceable>device
</replaceable> <replaceable>bytes
</replaceable></varname></term>
1295 <term><varname>BlockIOWriteBandwidth=
<replaceable>device
</replaceable> <replaceable>bytes
</replaceable></varname></term>
1298 <para>Set the per-device overall block I/O bandwidth limit for the executed processes, if the legacy control
1299 group hierarchy is used on the system. Takes a space-separated pair of a file path and a bandwidth value (in
1300 bytes per second) to specify the device specific bandwidth. The file path may be a path to a block device
1301 node, or as any other file in which case the backing block device of the file system of the file is used. If
1302 the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is parsed as Kilobytes, Megabytes,
1303 Gigabytes, or Terabytes, respectively, to the base of
1000. (Example:
1304 "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the
1305 <literal>blkio.throttle.read_bps_device
</literal> and
<literal>blkio.throttle.write_bps_device
</literal>
1306 control group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For
1307 details about these control group attributes, see
<ulink
1308 url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html">Block IO Controller
</ulink>.
1312 <literal>BlockIOAccounting=yes
</literal>.
</para>
1314 <para>These settings are deprecated. Use
<varname>IOReadBandwidthMax=
</varname> and
1315 <varname>IOWriteBandwidthMax=
</varname> instead.
</para>
1323 <title>See Also
</title>
1325 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1326 <citerefentry><refentrytitle>systemd-system.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1327 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1328 <citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1329 <citerefentry><refentrytitle>systemd.slice
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1330 <citerefentry><refentrytitle>systemd.scope
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1331 <citerefentry><refentrytitle>systemd.socket
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1332 <citerefentry><refentrytitle>systemd.mount
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1333 <citerefentry><refentrytitle>systemd.swap
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1334 <citerefentry><refentrytitle>systemd.exec
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1335 <citerefentry><refentrytitle>systemd.directives
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1336 <citerefentry><refentrytitle>systemd.special
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1337 <citerefentry><refentrytitle>systemd-oomd.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1338 The documentation for control groups and specific controllers in the Linux kernel:
1339 <ulink url=
"https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html">Control Groups v2
</ulink>.