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

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

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

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

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

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).

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 cgroup-v2.txt[2] and sched-design-CFS.txt[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=.

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 cgroup-v2.txt[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.

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).

Specify the memory usage protection of the executed processes in this unit. If the memory usages of this unit and all its ancestors are below their minimum boundaries, this unit's memory won't be reclaimed.

Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is taken relative to the installed physical memory on the system. This controls the "memory.min" control group attribute. For details about this control group attribute, see cgroup-v2.txt[2].

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

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

Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is taken relative to the installed physical memory on the system. This controls the "memory.low" control group attribute. For details about this control group attribute, see cgroup-v2.txt[2].

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

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

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.high" control group attribute. For details about this control group attribute, see cgroup-v2.txt[2].

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

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 cgroup-v2.txt[2].

This setting replaces MemoryLimit=.

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 cgroup-v2.txt[2].

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

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).

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 pids.txt[6].

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

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.

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 cgroup-v2.txt[2]. 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.

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 cgroup-v2.txt[2].

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

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 cgroup-v2.txt[2].

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

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 cgroup-v2.txt[2].

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

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 cgroup-v2.txt[2].

Implies "IOAccounting=yes".

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

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).

Turn on address range network traffic filtering for 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 (separated by a "/" character). If the latter is omitted, the address is considered a host address, i.e. the prefix covers the whole address (32 for IPv4, 128 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 all access lists are empty. When configured the lists are enforced as follows:

In order to implement a whitelisting 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, however it often makes 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 fe80::/64	All link-local IP 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.

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. This controls the "devices.allow" and "devices.deny" control group attributes. For details about these control group attributes, see devices.txt[7].

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 whitelist 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. 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.

Control the policy for allowing device access:

strict

closed

auto

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.

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, io, blkio, memory, devices, pids. 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[8].

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.

Valid controllers are cpu, cpuacct, io, blkio, memory, devices, and pids.

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 sched-design-CFS.txt[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.

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.txt[9].

Implies "MemoryAccounting=yes".

This setting is deprecated. Use MemoryMax= instead.

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.

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 blkio-controller.txt[10]. 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.

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 blkio-controller.txt[10].

Implies "BlockIOAccounting=yes".

This setting is deprecated. Use IODeviceWeight= instead.

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 blkio-controller.txt[10].

Implies "BlockIOAccounting=yes".

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