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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.
Setting resource controls for a group of related units
As described in systemd.unit(5), the settings listed here may be set through the main file
of a unit and drop-in snippets in *.d/ directories. The list of directories searched for
drop-ins includes names formed by repeatedly truncating the unit name after all dashes.
This is particularly convenient to set resource limits for a group of units with similar
names.
For example, every user gets their own slice user-nnn.slice. Drop-ins with local
configuration that affect user 1000 may be placed in /etc/systemd/system/user-1000.slice,
/etc/systemd/system/user-1000.slice.d/*.conf, but also
/etc/systemd/system/user-.slice.d/*.conf. This last directory applies to all user slices.
IMPLICIT DEPENDENCIES
The following dependencies are implicitly added:
o 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. A higher weight means more CPU time, a lower weight
means less.
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].
Setting CPUQuota= to an empty value unsets the quota.
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 NUMA nodes 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. A higher weight means
more I/O bandwidth, a lower weight means less.
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:
o Access is granted when the checked IP address matches an entry in the
IPAddressAllow= list.
o Otherwise, access is denied when the checked IP address matches an entry in the
IPAddressDeny= list.
o 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 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.
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.
If the path BPF_FS_PROGRAM_PATH in IPIngressFilterPath= assignment is already being
handled by BPFProgram= ingress hook, e.g. BPFProgram=ingress:BPF_FS_PROGRAM_PATH, the
assignment will be still considered valid and the program will be attached to a
cgroup. Same for IPEgressFilterPath= path and egress hook.
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.
BPFProgram=type:program-path
Add a custom cgroup BPF program.
BPFProgram= allows attaching BPF hooks to the cgroup of a systemd unit. (This
generalizes the functionality exposed via IPEgressFilterPath= for egress and
IPIngressFilterPath= for ingress.) Cgroup-bpf hooks in the form of BPF programs loaded
to the BPF filesystem are attached with cgroup-bpf attach flags determined by the
unit. For details about attachment types and flags see
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/include/uapi/linux/bpf.h.
For general BPF documentation please refer to
https://www.kernel.org/doc/html/latest/bpf/index.html.
The specification of BPF program consists of a type followed by a program-path with
":" as the separator: type:program-path.
type is the string name of BPF attach type also used in bpftool. type can be one of
egress, ingress, sock_create, sock_ops, device, bind4, bind6, connect4, connect6,
post_bind4, post_bind6, sendmsg4, sendmsg6, sysctl, recvmsg4, recvmsg6, getsockopt,
setsockopt.
Setting BPFProgram= to an empty value makes previous assignments ineffective.
Multiple assignments of the same type:program-path value have the same effect as a
single assignment: the program with the path program-path will be attached to cgroup
hook type just once.
If BPF egress pinned to program-path path is already being handled by
IPEgressFilterPath=, BPFProgram= assignment will be considered valid and BPFProgram=
will be attached to a cgroup. Similarly for ingress hook and IPIngressFilterPath=
assignment.
BPF programs passed with BPFProgram= are attached to the cgroup of a unit with BPF
attach flag multi, that allows further attachments of the same type within cgroup
hierarchy topped by the unit cgroup.
Examples:
BPFProgram=egress:/sys/fs/bpf/egress-hook
BPFProgram=bind6:/sys/fs/bpf/sock-addr-hook
SocketBindAllow=bind-rule, SocketBindDeny=bind-rule
Allow or deny binding a socket address to a socket by matching it with the bind-rule
and applying a corresponding action if there is a match.
bind-rule describes socket properties such as address-family, transport-protocol and
ip-ports.
bind-rule := { [address-family:][transport-protocol:][ip-ports] | any }
address-family := { ipv4 | ipv6 }
transport-protocol := { tcp | udp }
ip-ports := { ip-port | ip-port-range }
An optional address-family expects ipv4 or ipv6 values. If not specified, a rule will
be matched for both IPv4 and IPv6 addresses and applied depending on other socket
fields, e.g. transport-protocol, ip-port.
An optional transport-protocol expects tcp or udp transport protocol names. If not
specified, a rule will be matched for any transport protocol.
An optional ip-port value must lie within 1...65535 interval inclusively, i.e. dynamic
port 0 is not allowed. A range of sequential ports is described by ip-port-range :=
ip-port-low-ip-port-high, where ip-port-low is smaller than or equal to ip-port-high
and both are within 1...65535 inclusively.
A special value any can be used to apply a rule to any address family, transport
protocol and any port with a positive value.
To allow multiple rules assign SocketBindAllow= or SocketBindDeny= multiple times. To
clear the existing assignments pass an empty SocketBindAllow= or SocketBindDeny=
assignment.
For each of SocketBindAllow= and SocketBindDeny=, maximum allowed number of
assignments is 128.
o Binding to a socket is allowed when a socket address matches an entry in the
SocketBindAllow= list.
o Otherwise, binding is denied when the socket address matches an entry in the
SocketBindDeny= list.
o Otherwise, binding is allowed.
The feature is implemented with cgroup/bind4 and cgroup/bind6 cgroup-bpf hooks.
Examples:
...
# Allow binding IPv6 socket addresses with a port greater than or equal to 10000.
[Service]
SocketBindAllow=ipv6:10000-65535
SocketBindDeny=any
...
# Allow binding IPv4 and IPv6 socket addresses with 1234 and 4321 ports.
[Service]
SocketBindAllow=1234
SocketBindAllow=4321
SocketBindDeny=any
...
# Deny binding IPv6 socket addresses.
[Service]
SocketBindDeny=ipv6
...
# Deny binding IPv4 and IPv6 socket addresses.
[Service]
SocketBindDeny=any
...
# Allow binding only over TCP
[Service]
SocketBindAllow=tcp
SocketBindDeny=any
...
# Allow binding only over IPv6/TCP
[Service]
SocketBindAllow=ipv6:tcp
SocketBindDeny=any
...
# Allow binding ports within 10000-65535 range over IPv4/UDP.
[Service]
SocketBindAllow=ipv4:udp:10000-65535
SocketBindDeny=any
...
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 AT xyz.service and
Wants=modprobe AT xyz.service lines that load the necessary kernel module implementing
the device group if missing. Example:
...
[Unit]
Wants=modprobe AT loop.service
After=modprobe AT 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.
ManagedOOMMemoryPressureLimit=
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 to use the
default set by oomd.conf(5).
ManagedOOMPreference=none|avoid|omit
Allows deprioritizing or omitting this unit's cgroup as a candidate when systemd-oomd
needs to act. Requires support for extended attributes (see xattr(7)) in order to use
avoid or omit. Additionally, systemd-oomd will ignore these extended attributes if the
unit's cgroup is not owned by the root user.
If this property is set to avoid, the service manager will convey this to
systemd-oomd, which will only select this cgroup if there are no other viable
candidates.
If this property is set to omit, the service manager will convey this to systemd-oomd,
which will ignore this cgroup as a candidate and will not perform any actions on it.
It is recommended to use avoid and omit sparingly, as it can adversely affect
systemd-oomd's kill behavior. Also note that these extended attributes are not applied
recursively to cgroups under this unit's cgroup.
Defaults to none which means systemd-oomd will rank this unit's cgroup as defined in
systemd-oomd.service(8) and 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 249 SYSTEMD.RESOURCE-CONTROL(5)
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