systemd.resource-control

SYSTEMD.RESOURCE-CONTROL(5) systemd.resource-control SYSTEMD.RESOURCE-CONTROL(5)



NAME
       systemd.resource-control - Resource control unit settings

SYNOPSIS
       slice.slice, scope.scope, service.service, socket.socket, mount.mount,
       swap.swap

DESCRIPTION
       Unit configuration files for services, slices, scopes, sockets, mount
       points, and swap devices share a subset of configuration options for
       resource control of spawned processes. Internally, this relies on the
       Linux Control Groups (cgroups) kernel concept for organizing processes in
       a hierarchical tree of named groups for the purpose of resource
       management.

       This man page lists the configuration options shared by those six unit
       types. See systemd.unit(5) for the common options of all unit
       configuration files, and systemd.slice(5), systemd.scope(5),
       systemd.service(5), systemd.socket(5), systemd.mount(5), and
       systemd.swap(5) for more information on the specific unit configuration
       files. The resource control configuration options are configured in the
       [Slice], [Scope], [Service], [Socket], [Mount], or [Swap] sections,
       depending on the unit type.

       In addition, options which control resources available to programs
       executed by systemd are listed in systemd.exec(5). Those options
       complement options listed here.

       See the New Control Group Interfaces[1] for an introduction on how to
       make use of resource control APIs from programs.

IMPLICIT DEPENDENCIES
       The following dependencies are implicitly added:

       •   Units with the Slice= setting set automatically acquire Requires= and
           After= dependencies on the specified slice unit.

UNIFIED AND LEGACY CONTROL GROUP HIERARCHIES
       The unified control group hierarchy is the new version of kernel control
       group interface, see Control Groups v2[2]. Depending on the resource
       type, there are differences in resource control capabilities. Also,
       because of interface changes, some resource types have separate set of
       options on the unified hierarchy.

       CPU
           CPUWeight= and StartupCPUWeight= replace CPUShares= and
           StartupCPUShares=, respectively.

           The "cpuacct" controller does not exist separately on the unified
           hierarchy.

       Memory
           MemoryMax= replaces MemoryLimit=.  MemoryLow= and MemoryHigh= are
           effective only on unified hierarchy.

       IO
           "IO"-prefixed settings are a superset of and replace
           "BlockIO"-prefixed ones. On unified hierarchy, IO resource control
           also applies to buffered writes.

       To ease the transition, there is best-effort translation between the two
       versions of settings. For each controller, if any of the settings for the
       unified hierarchy are present, all settings for the legacy hierarchy are
       ignored. If the resulting settings are for the other type of hierarchy,
       the configurations are translated before application.

       Legacy control group hierarchy (see Control Groups version 1[3]), also
       called cgroup-v1, doesn't allow safe delegation of controllers to
       unprivileged processes. If the system uses the legacy control group
       hierarchy, resource control is disabled for the systemd user instance,
       see systemd(1).

OPTIONS
       Units of the types listed above can have settings for resource control
       configuration:

       CPUAccounting=
           Turn on CPU usage accounting for this unit. Takes a boolean argument.
           Note that turning on CPU accounting for one unit will also implicitly
           turn it on for all units contained in the same slice and for all its
           parent slices and the units contained therein. The system default for
           this setting may be controlled with DefaultCPUAccounting= in systemd-
           system.conf(5).

       CPUWeight=weight, StartupCPUWeight=weight
           Assign the specified CPU time weight to the processes executed, if
           the unified control group hierarchy is used on the system. These
           options take an integer value and control the "cpu.weight" control
           group attribute. The allowed range is 1 to 10000. Defaults to 100.
           For details about this control group attribute, see Control Groups
           v2[2] and CFS Scheduler[4]. The available CPU time is split up among
           all units within one slice relative to their CPU time weight.

           While StartupCPUWeight= only applies to the startup phase of the
           system, CPUWeight= applies to normal runtime of the system, and if
           the former is not set also to the startup phase. Using
           StartupCPUWeight= allows prioritizing specific services at boot-up
           differently than during normal runtime.

           These settings replace CPUShares= and StartupCPUShares=.

       CPUQuota=
           Assign the specified CPU time quota to the processes executed. Takes
           a percentage value, suffixed with "%". The percentage specifies how
           much CPU time the unit shall get at maximum, relative to the total
           CPU time available on one CPU. Use values > 100% for allotting CPU
           time on more than one CPU. This controls the "cpu.max" attribute on
           the unified control group hierarchy and "cpu.cfs_quota_us" on legacy.
           For details about these control group attributes, see Control Groups
           v2[2] and sched-bwc.txt[5].

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

       CPUQuotaPeriodSec=
           Assign the duration over which the CPU time quota specified by
           CPUQuota= is measured. Takes a time duration value in seconds, with
           an optional suffix such as "ms" for milliseconds (or "s" for
           seconds.) The default setting is 100ms. The period is clamped to the
           range supported by the kernel, which is [1ms, 1000ms]. Additionally,
           the period is adjusted up so that the quota interval is also at least
           1ms. Setting CPUQuotaPeriodSec= to an empty value resets it to the
           default.

           This controls the second field of "cpu.max" attribute on the unified
           control group hierarchy and "cpu.cfs_period_us" on legacy. For
           details about these control group attributes, see Control Groups
           v2[2] and CFS Scheduler[4].

           Example: CPUQuotaPeriodSec=10ms to request that the CPU quota is
           measured in periods of 10ms.

       AllowedCPUs=
           Restrict processes to be executed on specific CPUs. Takes a list of
           CPU indices or ranges separated by either whitespace or commas. CPU
           ranges are specified by the lower and upper CPU indices separated by
           a dash.

           Setting AllowedCPUs= doesn't guarantee that all of the CPUs will be
           used by the processes as it may be limited by parent units. The
           effective configuration is reported as EffectiveCPUs=.

           This setting is supported only with the unified control group
           hierarchy.

       AllowedMemoryNodes=
           Restrict processes to be executed on specific memory NUMA nodes.
           Takes a list of memory NUMA nodes indices or ranges separated by
           either whitespace or commas. Memory NUMA nodes ranges are specified
           by the lower and upper CPU indices separated by a dash.

           Setting AllowedMemoryNodes= doesn't guarantee that all of the memory
           NUMA nodes will be used by the processes as it may be limited by
           parent units. The effective configuration is reported as
           EffectiveMemoryNodes=.

           This setting is supported only with the unified control group
           hierarchy.

       MemoryAccounting=
           Turn on process and kernel memory accounting for this unit. Takes a
           boolean argument. Note that turning on memory accounting for one unit
           will also implicitly turn it on for all units contained in the same
           slice and for all its parent slices and the units contained therein.
           The system default for this setting may be controlled with
           DefaultMemoryAccounting= in systemd-system.conf(5).

       MemoryMin=bytes, MemoryLow=bytes
           Specify the memory usage protection of the executed processes in this
           unit. When reclaiming memory, the unit is treated as if it was using
           less memory resulting in memory to be preferentially reclaimed from
           unprotected units. Using MemoryLow= results in a weaker protection
           where memory may still be reclaimed to avoid invoking the OOM killer
           in case there is no other reclaimable memory.

           For a protection to be effective, it is generally required to set a
           corresponding allocation on all ancestors, which is then distributed
           between children (with the exception of the root slice). Any
           MemoryMin= or MemoryLow= allocation that is not explicitly
           distributed to specific children is used to create a shared
           protection for all children. As this is a shared protection, the
           children will freely compete for the memory.

           Takes a memory size in bytes. If the value is suffixed with K, M, G
           or T, the specified memory size is parsed as Kilobytes, Megabytes,
           Gigabytes, or Terabytes (with the base 1024), respectively.
           Alternatively, a percentage value may be specified, which is taken
           relative to the installed physical memory on the system. If assigned
           the special value "infinity", all available memory is protected,
           which may be useful in order to always inherit all of the protection
           afforded by ancestors. This controls the "memory.min" or "memory.low"
           control group attribute. For details about this control group
           attribute, see Memory Interface Files[6].

           This setting is supported only if the unified control group hierarchy
           is used and disables MemoryLimit=.

           Units may have their children use a default "memory.min" or
           "memory.low" value by specifying DefaultMemoryMin= or
           DefaultMemoryLow=, which has the same semantics as MemoryMin= and
           MemoryLow=. This setting does not affect "memory.min" or "memory.low"
           in the unit itself. Using it to set a default child allocation is
           only useful on kernels older than 5.7, which do not support the
           "memory_recursiveprot" cgroup2 mount option.

       MemoryHigh=bytes
           Specify the throttling limit on memory usage of the executed
           processes in this unit. Memory usage may go above the limit if
           unavoidable, but the processes are heavily slowed down and memory is
           taken away aggressively in such cases. This is the main mechanism to
           control memory usage of a unit.

           Takes a memory size in bytes. If the value is suffixed with K, M, G
           or T, the specified memory size is parsed as Kilobytes, Megabytes,
           Gigabytes, or Terabytes (with the base 1024), respectively.
           Alternatively, a percentage value may be specified, which is taken
           relative to the installed physical memory on the system. If assigned
           the special value "infinity", no memory throttling is applied. This
           controls the "memory.high" control group attribute. For details about
           this control group attribute, see Memory Interface Files[6].

           This setting is supported only if the unified control group hierarchy
           is used and disables MemoryLimit=.

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

           Takes a memory size in bytes. If the value is suffixed with K, M, G
           or T, the specified memory size is parsed as Kilobytes, Megabytes,
           Gigabytes, or Terabytes (with the base 1024), respectively.
           Alternatively, a percentage value may be specified, which is taken
           relative to the installed physical memory on the system. If assigned
           the special value "infinity", no memory limit is applied. This
           controls the "memory.max" control group attribute. For details about
           this control group attribute, see Memory Interface Files[6].

           This setting replaces MemoryLimit=.

       MemorySwapMax=bytes
           Specify the absolute limit on swap usage of the executed processes in
           this unit.

           Takes a swap size in bytes. If the value is suffixed with K, M, G or
           T, the specified swap size is parsed as Kilobytes, Megabytes,
           Gigabytes, or Terabytes (with the base 1024), respectively. If
           assigned the special value "infinity", no swap limit is applied. This
           controls the "memory.swap.max" control group attribute. For details
           about this control group attribute, see Memory Interface Files[6].

           This setting is supported only if the unified control group hierarchy
           is used and disables MemoryLimit=.

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

       TasksMax=N
           Specify the maximum number of tasks that may be created in the unit.
           This ensures that the number of tasks accounted for the unit (see
           above) stays below a specific limit. This either takes an absolute
           number of tasks or a percentage value that is taken relative to the
           configured maximum number of tasks on the system. If assigned the
           special value "infinity", no tasks limit is applied. This controls
           the "pids.max" control group attribute. For details about this
           control group attribute, see Process Number Controller[7].

           The system default for this setting may be controlled with
           DefaultTasksMax= in systemd-system.conf(5).

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

           This setting replaces BlockIOAccounting= and disables settings
           prefixed with BlockIO or StartupBlockIO.

       IOWeight=weight, StartupIOWeight=weight
           Set the default overall block I/O weight for the executed processes,
           if the unified control group hierarchy is used on the system. Takes a
           single weight value (between 1 and 10000) to set the default block
           I/O weight. This controls the "io.weight" control group attribute,
           which defaults to 100. For details about this control group
           attribute, see IO Interface Files[8]. The available I/O bandwidth is
           split up among all units within one slice relative to their block I/O
           weight.

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

           These settings replace BlockIOWeight= and StartupBlockIOWeight= and
           disable settings prefixed with BlockIO or StartupBlockIO.

       IODeviceWeight=device weight
           Set the per-device overall block I/O weight for the executed
           processes, if the unified control group hierarchy is used on the
           system. Takes a space-separated pair of a file path and a weight
           value to specify the device specific weight value, between 1 and
           10000. (Example: "/dev/sda 1000"). The file path may be specified as
           path to a block device node or as any other file, in which case the
           backing block device of the file system of the file is determined.
           This controls the "io.weight" control group attribute, which defaults
           to 100. Use this option multiple times to set weights for multiple
           devices. For details about this control group attribute, see IO
           Interface Files[8].

           This setting replaces BlockIODeviceWeight= and disables settings
           prefixed with BlockIO or StartupBlockIO.

           The specified device node should reference a block device that has an
           I/O scheduler associated, i.e. should not refer to partition or
           loopback block devices, but to the originating, physical device. When
           a path to a regular file or directory is specified it is attempted to
           discover the correct originating device backing the file system of
           the specified path. This works correctly only for simpler cases,
           where the file system is directly placed on a partition or physical
           block device, or where simple 1:1 encryption using dm-crypt/LUKS is
           used. This discovery does not cover complex storage and in particular
           RAID and volume management storage devices.

       IOReadBandwidthMax=device bytes, IOWriteBandwidthMax=device bytes
           Set the per-device overall block I/O bandwidth maximum limit for the
           executed processes, if the unified control group hierarchy is used on
           the system. This limit is not work-conserving and the executed
           processes are not allowed to use more even if the device has idle
           capacity. Takes a space-separated pair of a file path and a bandwidth
           value (in bytes per second) to specify the device specific bandwidth.
           The file path may be a path to a block device node, or as any other
           file in which case the backing block device of the file system of the
           file is used. If the bandwidth is suffixed with K, M, G, or T, the
           specified bandwidth is parsed as Kilobytes, Megabytes, Gigabytes, or
           Terabytes, respectively, to the base of 1000. (Example:
           "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls
           the "io.max" control group attributes. Use this option multiple times
           to set bandwidth limits for multiple devices. For details about this
           control group attribute, see IO Interface Files[8].

           These settings replace BlockIOReadBandwidth= and
           BlockIOWriteBandwidth= and disable settings prefixed with BlockIO or
           StartupBlockIO.

           Similar restrictions on block device discovery as for IODeviceWeight=
           apply, see above.

       IOReadIOPSMax=device IOPS, IOWriteIOPSMax=device IOPS
           Set the per-device overall block I/O IOs-Per-Second maximum limit for
           the executed processes, if the unified control group hierarchy is
           used on the system. This limit is not work-conserving and the
           executed processes are not allowed to use more even if the device has
           idle capacity. Takes a space-separated pair of a file path and an
           IOPS value to specify the device specific IOPS. The file path may be
           a path to a block device node, or as any other file in which case the
           backing block device of the file system of the file is used. If the
           IOPS is suffixed with K, M, G, or T, the specified IOPS is parsed as
           KiloIOPS, MegaIOPS, GigaIOPS, or TeraIOPS, respectively, to the base
           of 1000. (Example: "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0
           1K"). This controls the "io.max" control group attributes. Use this
           option multiple times to set IOPS limits for multiple devices. For
           details about this control group attribute, see IO Interface
           Files[8].

           These settings are supported only if the unified control group
           hierarchy is used and disable settings prefixed with BlockIO or
           StartupBlockIO.

           Similar restrictions on block device discovery as for IODeviceWeight=
           apply, see above.

       IODeviceLatencyTargetSec=device target
           Set the per-device average target I/O latency for the executed
           processes, if the unified control group hierarchy is used on the
           system. Takes a file path and a timespan separated by a space to
           specify the device specific latency target. (Example: "/dev/sda
           25ms"). The file path may be specified as path to a block device node
           or as any other file, in which case the backing block device of the
           file system of the file is determined. This controls the "io.latency"
           control group attribute. Use this option multiple times to set
           latency target for multiple devices. For details about this control
           group attribute, see IO Interface Files[8].

           Implies "IOAccounting=yes".

           These settings are supported only if the unified control group
           hierarchy is used.

           Similar restrictions on block device discovery as for IODeviceWeight=
           apply, see above.

       IPAccounting=
           Takes a boolean argument. If true, turns on IPv4 and IPv6 network
           traffic accounting for packets sent or received by the unit. When
           this option is turned on, all IPv4 and IPv6 sockets created by any
           process of the unit are accounted for.

           When this option is used in socket units, it applies to all IPv4 and
           IPv6 sockets associated with it (including both listening and
           connection sockets where this applies). Note that for
           socket-activated services, this configuration setting and the
           accounting data of the service unit and the socket unit are kept
           separate, and displayed separately. No propagation of the setting and
           the collected statistics is done, in either direction. Moreover, any
           traffic sent or received on any of the socket unit's sockets is
           accounted to the socket unit — and never to the service unit it might
           have activated, even if the socket is used by it.

           The system default for this setting may be controlled with
           DefaultIPAccounting= in systemd-system.conf(5).

       IPAddressAllow=ADDRESS[/PREFIXLENGTH]...,
       IPAddressDeny=ADDRESS[/PREFIXLENGTH]...
           Turn on network traffic filtering for IP packets sent and received
           over AF_INET and AF_INET6 sockets. Both directives take a space
           separated list of IPv4 or IPv6 addresses, each optionally suffixed
           with an address prefix length in bits after a "/" character. If the
           suffix is omitted, the address is considered a host address, i.e. the
           filter covers the whole address (32 bits for IPv4, 128 bits for
           IPv6).

           The access lists configured with this option are applied to all
           sockets created by processes of this unit (or in the case of socket
           units, associated with it). The lists are implicitly combined with
           any lists configured for any of the parent slice units this unit
           might be a member of. By default both access lists are empty. Both
           ingress and egress traffic is filtered by these settings. In case of
           ingress traffic the source IP address is checked against these access
           lists, in case of egress traffic the destination IP address is
           checked. The following rules are applied in turn:

           •   Access is granted when the checked IP address matches an entry in
               the IPAddressAllow= list.

           •   Otherwise, access is denied when the checked IP address matches
               an entry in the IPAddressDeny= list.

           •   Otherwise, access is granted.

           In order to implement an allow-listing IP firewall, it is recommended
           to use a IPAddressDeny=any setting on an upper-level slice unit (such
           as the root slice -.slice or the slice containing all system services
           system.slice – see systemd.special(7) for details on these slice
           units), plus individual per-service IPAddressAllow= lines permitting
           network access to relevant services, and only them.

           Note that for socket-activated services, the IP access list
           configured on the socket unit applies to all sockets associated with
           it directly, but not to any sockets created by the ultimately
           activated services for it. Conversely, the IP access list configured
           for the service is not applied to any sockets passed into the service
           via socket activation. Thus, it is usually a good idea to replicate
           the IP access lists on both the socket and the service unit.
           Nevertheless, it may make sense to maintain one list more open and
           the other one more restricted, depending on the usecase.

           If these settings are used multiple times in the same unit the
           specified lists are combined. If an empty string is assigned to these
           settings the specific access list is reset and all previous settings
           undone.

           In place of explicit IPv4 or IPv6 address and prefix length
           specifications a small set of symbolic names may be used. The
           following names are defined:

           Table 1. Special address/network names
           ┌──────────────┬──────────────────────┬──────────────────────┐
           │Symbolic Name Definition           Meaning              │
           ├──────────────┼──────────────────────┼──────────────────────┤
           │any           │ 0.0.0.0/0 ::/0       │ Any host             │
           ├──────────────┼──────────────────────┼──────────────────────┤
           │localhost     │ 127.0.0.0/8 ::1/128  │ All addresses on the │
           │              │                      │ local loopback       │
           ├──────────────┼──────────────────────┼──────────────────────┤
           │link-local    │ 169.254.0.0/16       │ All link-local IP    │
           │              │ fe80::/64            │ addresses            │
           ├──────────────┼──────────────────────┼──────────────────────┤
           │multicast     │ 224.0.0.0/4 ff00::/8 │ All IP multicasting  │
           │              │                      │ addresses            │
           └──────────────┴──────────────────────┴──────────────────────┘
           Note that these settings might not be supported on some systems (for
           example if eBPF control group support is not enabled in the
           underlying kernel or container manager). These settings will have no
           effect in that case. If compatibility with such systems is desired it
           is hence recommended to not exclusively rely on them for IP security.

       IPIngressFilterPath=BPF_FS_PROGRAM_PATH,
       IPEgressFilterPath=BPF_FS_PROGRAM_PATH
           Add custom network traffic filters implemented as BPF programs,
           applying to all IP packets sent and received over AF_INET and
           AF_INET6 sockets. Takes an absolute path to a pinned BPF program in
           the BPF virtual filesystem (/sys/fs/bpf/).

           The filters configured with this option are applied to all sockets
           created by processes of this unit (or in the case of socket units,
           associated with it). The filters are loaded in addition to filters
           any of the parent slice units this unit might be a member of as well
           as any IPAddressAllow= and IPAddressDeny= filters in any of these
           units. By default there are no filters specified.

           If these settings are used multiple times in the same unit all the
           specified programs are attached. If an empty string is assigned to
           these settings the program list is reset and all previous specified
           programs ignored.

           Note that for socket-activated services, the IP filter programs
           configured on the socket unit apply to all sockets associated with it
           directly, but not to any sockets created by the ultimately activated
           services for it. Conversely, the IP filter programs configured for
           the service are not applied to any sockets passed into the service
           via socket activation. Thus, it is usually a good idea, to replicate
           the IP filter programs on both the socket and the service unit,
           however it often makes sense to maintain one configuration more open
           and the other one more restricted, depending on the usecase.

           Note that these settings might not be supported on some systems (for
           example if eBPF control group support is not enabled in the
           underlying kernel or container manager). These settings will fail the
           service in that case. If compatibility with such systems is desired
           it is hence recommended to attach your filter manually (requires
           Delegate=yes) instead of using this setting.

       DeviceAllow=
           Control access to specific device nodes by the executed processes.
           Takes two space-separated strings: a device node specifier followed
           by a combination of r, w, m to control reading, writing, or creation
           of the specific device node(s) by the unit (mknod), respectively. On
           cgroup-v1 this controls the "devices.allow" control group attribute.
           For details about this control group attribute, see Device Whitelist
           Controller[9]. In the unified cgroup hierarchy this functionality is
           implemented using eBPF filtering.

           The device node specifier is either a path to a device node in the
           file system, starting with /dev/, or a string starting with either
           "char-" or "block-" followed by a device group name, as listed in
           /proc/devices. The latter is useful to allow-list all current and
           future devices belonging to a specific device group at once. The
           device group is matched according to filename globbing rules, you may
           hence use the "*" and "?"  wildcards. (Note that such globbing
           wildcards are not available for device node path specifications!) In
           order to match device nodes by numeric major/minor, use device node
           paths in the /dev/char/ and /dev/block/ directories. However,
           matching devices by major/minor is generally not recommended as
           assignments are neither stable nor portable between systems or
           different kernel versions.

           Examples: /dev/sda5 is a path to a device node, referring to an ATA
           or SCSI block device.  "char-pts" and "char-alsa" are specifiers for
           all pseudo TTYs and all ALSA sound devices, respectively.
           "char-cpu/*" is a specifier matching all CPU related device groups.

           Note that allow lists defined this way should only reference device
           groups which are resolvable at the time the unit is started. Any
           device groups not resolvable then are not added to the device allow
           list. In order to work around this limitation, consider extending
           service units with a pair of After=modprobe@xyz.service and
           Wants=modprobe@xyz.service lines that load the necessary kernel
           module implementing the device group if missing. Example:

               ...
               [Unit]
               Wants=modprobe@loop.service
               After=modprobe@loop.service

               [Service]
               DeviceAllow=block-loop
               DeviceAllow=/dev/loop-control
               ...

       DevicePolicy=auto|closed|strict
           Control the policy for allowing device access:

           strict
               means to only allow types of access that are explicitly
               specified.

           closed
               in addition, allows access to standard pseudo devices including
               /dev/null, /dev/zero, /dev/full, /dev/random, and /dev/urandom.

           auto
               in addition, allows access to all devices if no explicit
               DeviceAllow= is present. This is the default.

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

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

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

           Special care should be taken when relying on the default slice
           assignment in templated service units that have
           DefaultDependencies=no set, see systemd.service(5), section "Default
           Dependencies" for details.

       Delegate=
           Turns on delegation of further resource control partitioning to
           processes of the unit. Units where this is enabled may create and
           manage their own private subhierarchy of control groups below the
           control group of the unit itself. For unprivileged services (i.e.
           those using the User= setting) the unit's control group will be made
           accessible to the relevant user. When enabled the service manager
           will refrain from manipulating control groups or moving processes
           below the unit's control group, so that a clear concept of ownership
           is established: the control group tree above the unit's control group
           (i.e. towards the root control group) is owned and managed by the
           service manager of the host, while the control group tree below the
           unit's control group is owned and managed by the unit itself. Takes
           either a boolean argument or a list of control group controller
           names. If true, delegation is turned on, and all supported
           controllers are enabled for the unit, making them available to the
           unit's processes for management. If false, delegation is turned off
           entirely (and no additional controllers are enabled). If set to a
           list of controllers, delegation is turned on, and the specified
           controllers are enabled for the unit. Note that additional
           controllers than the ones specified might be made available as well,
           depending on configuration of the containing slice unit or other
           units contained in it. Note that assigning the empty string will
           enable delegation, but reset the list of controllers, all assignments
           prior to this will have no effect. Defaults to false.

           Note that controller delegation to less privileged code is only safe
           on the unified control group hierarchy. Accordingly, access to the
           specified controllers will not be granted to unprivileged services on
           the legacy hierarchy, even when requested.

           The following controller names may be specified: cpu, cpuacct,
           cpuset, io, blkio, memory, devices, pids, bpf-firewall, and
           bpf-devices.

           Not all of these controllers are available on all kernels however,
           and some are specific to the unified hierarchy while others are
           specific to the legacy hierarchy. Also note that the kernel might
           support further controllers, which aren't covered here yet as
           delegation is either not supported at all for them or not defined
           cleanly.

           For further details on the delegation model consult Control Group
           APIs and Delegation[10].

       DisableControllers=
           Disables controllers from being enabled for a unit's children. If a
           controller listed is already in use in its subtree, the controller
           will be removed from the subtree. This can be used to avoid child
           units being able to implicitly or explicitly enable a controller.
           Defaults to not disabling any controllers.

           It may not be possible to successfully disable a controller if the
           unit or any child of the unit in question delegates controllers to
           its children, as any delegated subtree of the cgroup hierarchy is
           unmanaged by systemd.

           Multiple controllers may be specified, separated by spaces. You may
           also pass DisableControllers= multiple times, in which case each new
           instance adds another controller to disable. Passing
           DisableControllers= by itself with no controller name present resets
           the disabled controller list.

           The following controller names may be specified: cpu, cpuacct,
           cpuset, io, blkio, memory, devices, pids, bpf-firewall, and
           bpf-devices.

       ManagedOOMSwap=auto|kill, ManagedOOMMemoryPressure=auto|kill
           Specifies how systemd-oomd.service(8) will act on this unit's
           cgroups. Defaults to auto.

           When set to kill, systemd-oomd will actively monitor this unit's
           cgroup metrics to decide whether it needs to act. If the cgroup
           passes the limits set by oomd.conf(5) or its overrides, systemd-oomd
           will send a SIGKILL to all of the processes under the chosen
           candidate cgroup. Note that only descendant cgroups can be eligible
           candidates for killing; the unit that set its property to kill is not
           a candidate (unless one of its ancestors set their property to kill).
           You can find more details on candidates and kill behavior at systemd-
           oomd.service(8) and oomd.conf(5). Setting either of these properties
           to kill will also automatically acquire After= and Wants=
           dependencies on systemd-oomd.service unless DefaultDependencies=no.

           When set to auto, systemd-oomd will not actively use this cgroup's
           data for monitoring and detection. However, if an ancestor cgroup has
           one of these properties set to kill, a unit with auto can still be an
           eligible candidate for systemd-oomd to act on.

       ManagedOOMMemoryPressureLimitPercent=
           Overrides the default memory pressure limit set by oomd.conf(5) for
           this unit (cgroup). Takes a percentage value between 0% and 100%,
           inclusive. This property is ignored unless
           ManagedOOMMemoryPressure=kill. Defaults to 0%, which means use the
           default set by oomd.conf(5).

DEPRECATED OPTIONS
       The following options are deprecated. Use the indicated superseding
       options instead:

       CPUShares=weight, StartupCPUShares=weight
           Assign the specified CPU time share weight to the processes executed.
           These options take an integer value and control the "cpu.shares"
           control group attribute. The allowed range is 2 to 262144. Defaults
           to 1024. For details about this control group attribute, see CFS
           Scheduler[4]. The available CPU time is split up among all units
           within one slice relative to their CPU time share weight.

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

           Implies "CPUAccounting=yes".

           These settings are deprecated. Use CPUWeight= and StartupCPUWeight=
           instead.

       MemoryLimit=bytes
           Specify the limit on maximum memory usage of the executed processes.
           The limit specifies how much process and kernel memory can be used by
           tasks in this unit. Takes a memory size in bytes. If the value is
           suffixed with K, M, G or T, the specified memory size is parsed as
           Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024),
           respectively. Alternatively, a percentage value may be specified,
           which is taken relative to the installed physical memory on the
           system. If assigned the special value "infinity", no memory limit is
           applied. This controls the "memory.limit_in_bytes" control group
           attribute. For details about this control group attribute, see Memory
           Resource Controller[11].

           Implies "MemoryAccounting=yes".

           This setting is deprecated. Use MemoryMax= instead.

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

           This setting is deprecated. Use IOAccounting= instead.

       BlockIOWeight=weight, StartupBlockIOWeight=weight
           Set the default overall block I/O weight for the executed processes,
           if the legacy control group hierarchy is used on the system. Takes a
           single weight value (between 10 and 1000) to set the default block
           I/O weight. This controls the "blkio.weight" control group attribute,
           which defaults to 500. For details about this control group
           attribute, see Block IO Controller[12]. The available I/O bandwidth
           is split up among all units within one slice relative to their block
           I/O weight.

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

           Implies "BlockIOAccounting=yes".

           These settings are deprecated. Use IOWeight= and StartupIOWeight=
           instead.

       BlockIODeviceWeight=device weight
           Set the per-device overall block I/O weight for the executed
           processes, if the legacy control group hierarchy is used on the
           system. Takes a space-separated pair of a file path and a weight
           value to specify the device specific weight value, between 10 and
           1000. (Example: "/dev/sda 500"). The file path may be specified as
           path to a block device node or as any other file, in which case the
           backing block device of the file system of the file is determined.
           This controls the "blkio.weight_device" control group attribute,
           which defaults to 1000. Use this option multiple times to set weights
           for multiple devices. For details about this control group attribute,
           see Block IO Controller[12].

           Implies "BlockIOAccounting=yes".

           This setting is deprecated. Use IODeviceWeight= instead.

       BlockIOReadBandwidth=device bytes, BlockIOWriteBandwidth=device bytes
           Set the per-device overall block I/O bandwidth limit for the executed
           processes, if the legacy control group hierarchy is used on the
           system. Takes a space-separated pair of a file path and a bandwidth
           value (in bytes per second) to specify the device specific bandwidth.
           The file path may be a path to a block device node, or as any other
           file in which case the backing block device of the file system of the
           file is used. If the bandwidth is suffixed with K, M, G, or T, the
           specified bandwidth is parsed as Kilobytes, Megabytes, Gigabytes, or
           Terabytes, respectively, to the base of 1000. (Example:
           "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls
           the "blkio.throttle.read_bps_device" and
           "blkio.throttle.write_bps_device" control group attributes. Use this
           option multiple times to set bandwidth limits for multiple devices.
           For details about these control group attributes, see Block IO
           Controller[12].

           Implies "BlockIOAccounting=yes".

           These settings are deprecated. Use IOReadBandwidthMax= and
           IOWriteBandwidthMax= instead.

SEE ALSO
       systemd(1), systemd-system.conf(5), systemd.unit(5), systemd.service(5),
       systemd.slice(5), systemd.scope(5), systemd.socket(5), systemd.mount(5),
       systemd.swap(5), systemd.exec(5), systemd.directives(7),
       systemd.special(7), systemd-oomd.service(8), The documentation for
       control groups and specific controllers in the Linux kernel: Control
       Groups v2[2].

NOTES
        1. New Control Group Interfaces
           https://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/

        2. Control Groups v2
           https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html

        3. Control Groups version 1
           https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/

        4. CFS Scheduler
           https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html

        5. sched-bwc.txt
           https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt

        6. Memory Interface Files
           https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-files

        7. Process Number Controller
           https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/pids.html

        8. IO Interface Files
           https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files

        9. Device Whitelist Controller
           https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/devices.html

       10. Control Group APIs and Delegation
           https://systemd.io/CGROUP_DELEGATION

       11. Memory Resource Controller
           https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/memory.html

       12. Block IO Controller
           https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html



systemd 247                                          SYSTEMD.RESOURCE-CONTROL(5)