Provided by: systemd_240-6ubuntu5_amd64 bug

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 cgroup-v2.txt[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 cgroups.txt[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 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 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=.

       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 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.

       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
           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=.

       MemoryLow=bytes
           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=.

       MemoryHigh=bytes
           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=.

       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 cgroup-v2.txt[2].

           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 cgroup-v2.txt[2].

           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
           pids.txt[6].

           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 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.

       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
           cgroup-v2.txt[2].

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

       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
           cgroup-v2.txt[2].

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

       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
           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.

       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 cgroup-v2.txt[2].

           Implies "IOAccounting=yes".

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

       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 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:

           ·   Access will be granted in case its destination/source address matches any entry in
               the IPAddressAllow= setting.

           ·   Otherwise, access will be denied in case its destination/source address matches
               any entry in the IPAddressDeny= setting.

           ·   Otherwise, access will be granted.

           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 NameDefinitionMeaning              │
           ├──────────────┼──────────────────────────┼──────────────────────┤
           │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.

       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. 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.

       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, 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].

       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.

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

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 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.

       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.txt[9].

           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 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.

       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
           blkio-controller.txt[10].

           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
           blkio-controller.txt[10].

           Implies "BlockIOAccounting=yes".

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

SEE ALSO

       systemd(1), 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), The documentation for control groups and
       specific controllers in the Linux kernel: cgroups.txt[3], cpuacct.txt[11], memory.txt[9],
       blkio-controller.txt[10].  sched-bwc.txt[5].

NOTES

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

        2. cgroup-v2.txt
           https://www.kernel.org/doc/Documentation/cgroup-v2.txt

        3. cgroups.txt
           https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt

        4. sched-design-CFS.txt
           https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt

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

        6. pids.txt
           https://www.kernel.org/doc/Documentation/cgroup-v1/pids.txt

        7. devices.txt
           https://www.kernel.org/doc/Documentation/cgroup-v1/devices.txt

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

        9. memory.txt
           https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt

       10. blkio-controller.txt
           https://www.kernel.org/doc/Documentation/cgroup-v1/blkio-controller.txt

       11. cpuacct.txt
           https://www.kernel.org/doc/Documentation/cgroup-v1/cpuacct.txt