Ubuntu Manpage: systemd.resource-control - Resource control unit settings

Provided by: systemd_252.5-2ubuntu3_amd64

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:

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

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
These options accept an integer value or a the special string "idle":

• If set to an integer value, assign the specified CPU time weight to the processes
executed, if the unified control group hierarchy is used on the system. These
options 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[3]. 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.

• If set to the special string "idle", mark the cgroup for "idle scheduling", which
means that it will get CPU resources only when there are no processes not marked
in this way to execute in this cgroup or its siblings. This setting corresponds to
the "cpu.idle" cgroup attribute.

Note that this value only has an effect on cgroup-v2, for cgroup-v1 it is
equivalent to the minimum weight.

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

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 CFS Bandwidth
Control[4]. 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[3].

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

AllowedCPUs=, StartupAllowedCPUs=
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= or StartupAllowedCPUs= 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=.

While StartupAllowedCPUs= applies to the startup and shutdown phases of the system,
AllowedCPUs= applies to normal runtime of the system, and if the former is not set
also to the startup and shutdown phases. Using StartupAllowedCPUs= allows prioritizing
specific services at boot-up and shutdown differently than during normal runtime.

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

AllowedMemoryNodes=, StartupAllowedMemoryNodes=
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= or StartupAllowedMemoryNodes= 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=.

While StartupAllowedMemoryNodes= applies to the startup and shutdown phases of the
system, AllowedMemoryNodes= applies to normal runtime of the system, and if the former
is not set also to the startup and shutdown phases. Using StartupAllowedMemoryNodes=
allows prioritizing specific services at boot-up and shutdown differently than during
normal runtime.

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[5].

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[5].

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[5].

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[5].

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, the pids
controller[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).

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[7]. 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= applies to the startup and shutdown phases of the system,
IOWeight= applies to the later runtime of the system, and if the former is not set
also to the startup and shutdown phases. This allows prioritizing specific services at
boot-up and shutdown differently than during runtime.

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[7].

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[7].

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[7].

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[7].

Implies "IOAccounting=yes".

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

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

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

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

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

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

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

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

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

• Otherwise, access is granted.

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

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

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

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

Table 1. Special address/network names
┌──────────────┬──────────────────────────┬──────────────────────┐
│Symbolic Name │ Definition │ Meaning │
├──────────────┼──────────────────────────┼──────────────────────┤
│any │ 0.0.0.0/0 ::/0 │ Any host │
├──────────────┼──────────────────────────┼──────────────────────┤
│localhost │ 127.0.0.0/8 ::1/128 │ All addresses on the │
│ │ │ local loopback │
├──────────────┼──────────────────────────┼──────────────────────┤
│link-local │ 169.254.0.0/16 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://docs.kernel.org/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.

• Binding to a socket is allowed when a socket address matches an entry in the
SocketBindAllow= list.

• Otherwise, binding is denied when the socket address matches an entry in the
SocketBindDeny= list.

• 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
...

RestrictNetworkInterfaces=
Takes a list of space-separated network interface names. This option restricts the
network interfaces that processes of this unit can use. By default processes can only
use the network interfaces listed (allow-list). If the first character of the rule is
"~", the effect is inverted: the processes can only use network interfaces not listed
(deny-list).

This option can appear multiple times, in which case the network interface names are
merged. If the empty string is assigned the set is reset, all prior assignments will
have not effect.

If you specify both types of this option (i.e. allow-listing and deny-listing), the
first encountered will take precedence and will dictate the default action (allow vs
deny). Then the next occurrences of this option will add or delete the listed network
interface names from the set, depending of its type and the default action.

The loopback interface ("lo") is not treated in any special way, you have to configure
it explicitly in the unit file.

Example 1: allow-list

RestrictNetworkInterfaces=eth1
RestrictNetworkInterfaces=eth2

Programs in the unit will be only able to use the eth1 and eth2 network interfaces.

Example 2: deny-list

RestrictNetworkInterfaces=~eth1 eth2

Programs in the unit will be able to use any network interface but eth1 and eth2.

Example 3: mixed

RestrictNetworkInterfaces=eth1 eth2
RestrictNetworkInterfaces=~eth1

Programs in the unit will be only able to use the eth2 network interface.

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 nodes by the unit
(mknod), respectively. This functionality is implemented using eBPF filtering.

When access to all physical devices should be disallowed, PrivateDevices= may be used
instead. See systemd.exec(5).

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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, the unit becomes a candidate for monitoring by systemd-oomd. If the
cgroup passes the limits set by oomd.conf(5) or the unit configuration, systemd-oomd
will select a descendant cgroup and send SIGKILL to all of the processes under it. 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 result in 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 a candidate for systemd-oomd to terminate.

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.

When calculating candidates to relieve swap usage, systemd-oomd will only respect
these extended attributes if the unit's cgroup is owned by root.

When calculating candidates to relieve memory pressure, systemd-oomd will only respect
these extended attributes if the unit's cgroup owner, and the owner of the monitored
ancestor cgroup are the same. For example, if systemd-oomd is calculating candidates
for -.slice, then extended attributes set on descendants of
/user.slice/user-1000.slice/user@1000.service/ will be ignored because the descendants
are owned by UID 1000, and -.slice is owned by UID 0. But, if calculating candidates
for /user.slice/user-1000.slice/user@1000.service/, then extended attributes set on
the descendants would be respected.

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).

HISTORY

       systemd 252
           Options for controlling the Legacy Control Group Hierarchy (Control Groups version
           1[9] are now fully deprecated: CPUShares=weight, StartupCPUShares=weight,
           MemoryLimit=bytes, BlockIOAccounting=, BlockIOWeight=weight,
           StartupBlockIOWeight=weight, BlockIODeviceWeight=device weight,
           BlockIOReadBandwidth=device bytes, BlockIOWriteBandwidth=device bytes. Please switch
           to the unified cgroup hierarchy.

NOTES

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

        2. Control Groups v2
           https://docs.kernel.org/admin-guide/cgroup-v2.html

        3. CFS Scheduler
           https://docs.kernel.org/scheduler/sched-design-CFS.html

        4. CFS Bandwidth Control
           https://docs.kernel.org/scheduler/sched-bwc.html

        5. Memory Interface Files
           https://docs.kernel.org/admin-guide/cgroup-v2.html#memory-interface-files

        6. pids controller
           https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#pid

        7. IO Interface Files
           https://docs.kernel.org/admin-guide/cgroup-v2.html#io-interface-files

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

        9. Control Groups version 1
           https://docs.kernel.org/admin-guide/cgroup-v1/index.html

NAME

SYNOPSIS

DESCRIPTION

IMPLICIT DEPENDENCIES

OPTIONS

HISTORY

SEE ALSO

NOTES