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
Control Groups 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.
See the New Control Group Interfaces[1] for an introduction
on how to make use of resource control APIs from programs.
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).
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[2]. 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.
These options imply "CPUAccounting=true".
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.cfs_quota_us"
control group attribute. For details about this control group attribute, see
sched-design-CFS.txt[2].
Example: CPUQuota=20% ensures that the executed processes
will never get more than 20% CPU time on one CPU.
Implies "CPUAccounting=true".
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).
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. 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[3].
Implies "MemoryAccounting=true".
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[4].
Implies "TasksAccounting=true". The system default for
this setting may be controlled with DefaultTasksMax= in
systemd-system.conf(5).
BlockIOAccounting=
Turn on Block IO accounting for this unit. Takes a
boolean argument. Note that turning on block IO 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).
BlockIOWeight=weight,
StartupBlockIOWeight=weight
Set the default overall block IO weight for the executed
processes. Takes a single weight value (between 10 and 1000) to set the
default block IO weight. This controls the "blkio.weight" control
group attribute, which defaults to 500. For details about this control group
attribute, see
blkio-controller.txt[5]. The available IO bandwidth is
split up among all units within one slice relative to their block IO 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=true".
BlockIODeviceWeight=device
weight
Set the per-device overall block IO weight for the
executed processes. 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[5].
Implies "BlockIOAccounting=true".
BlockIOReadBandwidth=device
bytes,
BlockIOWriteBandwidth=device
bytes
Set the per-device overall block IO bandwidth limit for
the executed processes. 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.read_bps_device" and "blkio.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[5].
Implies "BlockIOAccounting=true".
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[6].
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 file name 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.
Delegate=
Turns on delegation of further resource control
partitioning to processes of the unit. For unprivileged services (i.e. those
using the User= setting) this allows processes to create a subhierarchy
beneath its control group path. For privileged services and scopes this
ensures the processes will have all control group controllers enabled.