# PODNAME: Config::Model::models::Systemd::Section::Service
# ABSTRACT:  Configuration class Systemd::Section::Service

=encoding utf8

=head1 NAME

Config::Model::models::Systemd::Section::Service - Configuration class Systemd::Section::Service

=head1 DESCRIPTION

Configuration classes used by L<Config::Model>

A unit configuration file whose name ends in
C<.service> encodes information about a process
controlled and supervised by systemd.

This man page lists the configuration options specific to
this unit type. See
L<systemd.unit(5)>
for the common options of all unit configuration files. The common
configuration items are configured in the generic
C<[Unit]> and C<[Install]>
sections. The service specific configuration options are
configured in the C<[Service]> section.

Additional options are listed in
L<systemd.exec(5)>,
which define the execution environment the commands are executed
in, and in
L<systemd.kill(5)>,
which define the way the processes of the service are terminated,
and in
L<systemd.resource-control(5)>,
which configure resource control settings for the processes of the
service.

If a service is requested under a certain name but no unit
configuration file is found, systemd looks for a SysV init script
by the same name (with the .service suffix
removed) and dynamically creates a service unit from that script.
This is useful for compatibility with SysV. Note that this
compatibility is quite comprehensive but not 100%. For details
about the incompatibilities, see the Incompatibilities
with SysV document.
This configuration class was generated from systemd documentation.
by L<parse-man.pl|https://github.com/dod38fr/config-model-systemd/contrib/parse-man.pl>


=head1 Elements

=head2 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
C<DefaultCPUAccounting> in
L<systemd-system.conf(5)>. I< Optional. Type boolean.  > 

=head2 CPUWeight

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 C<cpu.weight>
control group attribute. The allowed range is 1 to 10000. Defaults to 100. For details about this control
group attribute, see cgroup-v2.txt and sched-design-CFS.txt.
The available CPU time is split up among all units within one slice relative to their CPU time weight.

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

These settings replace C<CPUShares> and C<StartupCPUShares>. I< Optional. Type integer.  > 

=over 4

=item upstream_default value :

100

=back



=head2 StartupCPUWeight

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 C<cpu.weight>
control group attribute. The allowed range is 1 to 10000. Defaults to 100. For details about this control
group attribute, see cgroup-v2.txt and sched-design-CFS.txt.
The available CPU time is split up among all units within one slice relative to their CPU time weight.

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

These settings replace C<CPUShares> and C<StartupCPUShares>. I< Optional. Type integer.  > 

=over 4

=item upstream_default value :

100

=back



=head2 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
C<cpu.max> attribute on the unified control group hierarchy and
C<cpu.cfs_quota_us> on legacy. For details about these control group attributes, see cgroup-v2.txt and sched-bwc.txt.

Example: C<CPUQuota=20%> ensures that the executed processes will never get more than
20% CPU time on one CPU. I< Optional. Type uniline.  > 

=head2 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
C<DefaultMemoryAccounting> in
L<systemd-system.conf(5)>. I< Optional. Type boolean.  > 

=head2 MemoryMin

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

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

This setting is supported only if the unified control group hierarchy is used and disables
C<MemoryLimit>. I< Optional. Type uniline.  > 

=head2 MemoryLow

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

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

This setting is supported only if the unified control group hierarchy is used and disables
C<MemoryLimit>. I< Optional. Type uniline.  > 

=head2 MemoryHigh

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

Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is
parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a
percentage value may be specified, which is taken relative to the installed physical memory on the
system. If assigned the
special value C<infinity>, no memory limit is applied. This controls the
C<memory.high> control group attribute. For details about this control group attribute, see
cgroup-v2.txt.

This setting is supported only if the unified control group hierarchy is used and disables
C<MemoryLimit>. I< Optional. Type uniline.  > 

=head2 MemoryMax

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 C<MemoryHigh> as the main control mechanism and use C<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 C<infinity>, no memory limit is applied. This controls the
C<memory.max> control group attribute. For details about this control group attribute, see
cgroup-v2.txt.

This setting replaces C<MemoryLimit>. I< Optional. Type uniline.  > 

=head2 MemorySwapMax

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 C<infinity>, no swap limit is applied. This controls the
C<memory.swap.max> control group attribute. For details about this control group attribute,
see cgroup-v2.txt.

This setting is supported only if the unified control group hierarchy is used and disables
C<MemoryLimit>. I< Optional. Type uniline.  > 

=head2 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
C<DefaultTasksAccounting> in
L<systemd-system.conf(5)>. I< Optional. Type boolean.  > 

=head2 TasksMax

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 C<infinity>, no tasks limit is applied. This controls
the C<pids.max> control group attribute. For details about this control group attribute, see
pids.txt.

The
system default for this setting may be controlled with
C<DefaultTasksMax> in
L<systemd-system.conf(5)>. I< Optional. Type uniline.  > 

=head2 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 C<DefaultIOAccounting>
in
L<systemd-system.conf(5)>.

This setting replaces C<BlockIOAccounting> and disables settings prefixed with
C<BlockIO> or C<StartupBlockIO>. I< Optional. Type boolean.  > 

=head2 IOWeight

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 C<io.weight> control group attribute, which defaults to
100. For details about this control group attribute, see cgroup-v2.txt.  The available I/O
bandwidth is split up among all units within one slice relative to their block I/O weight.

While C<StartupIOWeight> only applies
to the startup phase of the system,
C<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 C<BlockIOWeight> and C<StartupBlockIOWeight>
and disable settings prefixed with C<BlockIO> or C<StartupBlockIO>. I< Optional. Type uniline.  > 

=head2 StartupIOWeight

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 C<io.weight> control group attribute, which defaults to
100. For details about this control group attribute, see cgroup-v2.txt.  The available I/O
bandwidth is split up among all units within one slice relative to their block I/O weight.

While C<StartupIOWeight> only applies
to the startup phase of the system,
C<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 C<BlockIOWeight> and C<StartupBlockIOWeight>
and disable settings prefixed with C<BlockIO> or C<StartupBlockIO>. I< Optional. Type uniline.  > 

=head2 IODeviceWeight

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: C</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 C<io.weight> control
group attribute, which defaults to 100. Use this option multiple times to set weights for multiple devices.
For details about this control group attribute, see cgroup-v2.txt.

This setting replaces C<BlockIODeviceWeight> and disables settings prefixed with
C<BlockIO> or C<StartupBlockIO>. I< Optional. Type uniline.  > 

=head2 IOReadBandwidthMax

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 C<io.max> control
group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For details
about this control group attribute, see cgroup-v2.txt.

These settings replace C<BlockIOReadBandwidth> and
C<BlockIOWriteBandwidth> and disable settings prefixed with C<BlockIO> or
C<StartupBlockIO>. I< Optional. Type uniline.  > 

=head2 IOWriteBandwidthMax

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 C<io.max> control
group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For details
about this control group attribute, see cgroup-v2.txt.

These settings replace C<BlockIOReadBandwidth> and
C<BlockIOWriteBandwidth> and disable settings prefixed with C<BlockIO> or
C<StartupBlockIO>. I< Optional. Type uniline.  > 

=head2 IOReadIOPSMax

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 C<io.max> control
group attributes. Use this option multiple times to set IOPS limits for multiple devices. For details about
this control group attribute, see cgroup-v2.txt.

These settings are supported only if the unified control group hierarchy is used and disable settings
prefixed with C<BlockIO> or C<StartupBlockIO>. I< Optional. Type uniline.  > 

=head2 IOWriteIOPSMax

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 C<io.max> control
group attributes. Use this option multiple times to set IOPS limits for multiple devices. For details about
this control group attribute, see cgroup-v2.txt.

These settings are supported only if the unified control group hierarchy is used and disable settings
prefixed with C<BlockIO> or C<StartupBlockIO>. I< Optional. Type uniline.  > 

=head2 IODeviceLatencyTargetSec

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 C<io.latency> control group
attribute. Use this option multiple times to set latency target for multiple devices. For details about this
control group attribute, see cgroup-v2.txt.

Implies C<IOAccounting=yes>.

These settings are supported only if the unified control group hierarchy is used. I< Optional. Type uniline.  > 

=head2 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 C<DefaultIPAccounting> in
L<systemd-system.conf(5)>. I< Optional. Type boolean.  > 

=head2 IPAddressAllow

Turn on address range network traffic filtering for packets sent and received over AF_INET and AF_INET6
sockets.  Both directives take a space separated list of IPv4 or IPv6 addresses, each optionally suffixed
with an address prefix length (separated by a C</> character). If the latter is omitted, the
address is considered a host address, i.e. the prefix covers the whole address (32 for IPv4, 128 for IPv6).

The access lists configured with this option are applied to all sockets created by processes of this
unit (or in the case of socket units, associated with it). The lists are implicitly combined with any lists
configured for any of the parent slice units this unit might be a member of. By default all access lists are
empty. When configured the lists are enforced as follows:

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

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

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

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

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. I< Optional. Type uniline.  > 

=head2 IPAddressDeny

Turn on address range network traffic filtering for packets sent and received over AF_INET and AF_INET6
sockets.  Both directives take a space separated list of IPv4 or IPv6 addresses, each optionally suffixed
with an address prefix length (separated by a C</> character). If the latter is omitted, the
address is considered a host address, i.e. the prefix covers the whole address (32 for IPv4, 128 for IPv6).

The access lists configured with this option are applied to all sockets created by processes of this
unit (or in the case of socket units, associated with it). The lists are implicitly combined with any lists
configured for any of the parent slice units this unit might be a member of. By default all access lists are
empty. When configured the lists are enforced as follows:

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

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

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

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

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. I< Optional. Type uniline.  > 

=head2 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
C<r>, C<w>,
C<m> to control
reading, writing,
or creation of the specific device node(s) by the unit
(mknod), respectively. This controls
the C<devices.allow> and
C<devices.deny> control group
attributes. For details about these control group
attributes, see devices.txt.

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
C<char-> or C<block->
followed by a device group name, as listed in
/proc/devices. The latter is useful to
whitelist all current and future devices belonging to a
specific device group at once. The device group is matched
according to filename globbing rules, you may hence use the
C<*> and C<?>
wildcards. Examples: /dev/sda5 is a
path to a device node, referring to an ATA or SCSI block
device. C<char-pts> and
C<char-alsa> are specifiers for all pseudo
TTYs and all ALSA sound devices,
respectively. C<char-cpu/*> is a specifier
matching all CPU related device groups. I< Optional. Type list of uniline.  > 

=head2 DevicePolicy


Control the policy for allowing device access:
I< Optional. Type enum. choice: 'auto', 'closed', 'strict'.  > 

=head2 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 C<DefaultDependencies=no> set, see
L<systemd.service(5)>, section
"Default Dependencies" for details. I< Optional. Type uniline.  > 

=head2 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 C<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: C<cpu>, C<cpuacct>,
C<io>, C<blkio>, C<memory>, C<devices>,
C<pids>. Not all of these controllers are available on all kernels however, and some are
specific to the unified hierarchy while others are specific to the legacy hierarchy. Also note that the
kernel might support further controllers, which aren't covered here yet as delegation is either not supported
at all for them or not defined cleanly.

For further details on the delegation model consult Control Group APIs and Delegation. I< Optional. Type uniline.  > 

=head2 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
C<DisableControllers> multiple times, in which case each new instance adds another controller
to disable. Passing C<DisableControllers> by itself with no controller name present resets
the disabled controller list.

Valid controllers are C<cpu>, C<cpuacct>, C<io>,
C<blkio>, C<memory>, C<devices>, and C<pids>. I< Optional. Type uniline.  > 

=head2 CPUShares

Assign the specified CPU time share weight to the processes executed. These options take an integer
value and control the C<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.
The available CPU time is split up among all units within one slice relative to their CPU time share
weight.

While C<StartupCPUShares> only applies to the startup phase of the system,
C<CPUShares> applies to normal runtime of the system, and if the former is not set also to
the startup phase. Using C<StartupCPUShares> allows prioritizing specific services at
boot-up differently than during normal runtime.

Implies C<CPUAccounting=yes>.

These settings are deprecated. Use C<CPUWeight> and
C<StartupCPUWeight> instead. I< Optional. Type integer.  > 

=over 4

=item upstream_default value :

1024

=back



=head2 StartupCPUShares

Assign the specified CPU time share weight to the processes executed. These options take an integer
value and control the C<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.
The available CPU time is split up among all units within one slice relative to their CPU time share
weight.

While C<StartupCPUShares> only applies to the startup phase of the system,
C<CPUShares> applies to normal runtime of the system, and if the former is not set also to
the startup phase. Using C<StartupCPUShares> allows prioritizing specific services at
boot-up differently than during normal runtime.

Implies C<CPUAccounting=yes>.

These settings are deprecated. Use C<CPUWeight> and
C<StartupCPUWeight> instead. I< Optional. Type integer.  > 

=over 4

=item upstream_default value :

1024

=back



=head2 MemoryLimit

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
C<infinity>, no memory limit is applied. This controls the
C<memory.limit_in_bytes> control group attribute. For details about this control group
attribute, see memory.txt.

Implies C<MemoryAccounting=yes>.

This setting is deprecated. Use C<MemoryMax> instead. I< Optional. Type uniline.  > 

=head2 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
C<DefaultBlockIOAccounting> in
L<systemd-system.conf(5)>.

This setting is deprecated. Use C<IOAccounting> instead. I< Optional. Type boolean.  > 

=head2 BlockIOWeight

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 C<blkio.weight> control group attribute, which defaults to
500. For details about this control group attribute, see blkio-controller.txt.
The available I/O bandwidth is split up among all units within one slice relative to their block I/O
weight.

While C<StartupBlockIOWeight> only
applies to the startup phase of the system,
C<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
C<BlockIOAccounting=yes>.

These settings are deprecated. Use C<IOWeight> and C<StartupIOWeight>
instead. I< Optional. Type uniline.  > 

=head2 StartupBlockIOWeight

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 C<blkio.weight> control group attribute, which defaults to
500. For details about this control group attribute, see blkio-controller.txt.
The available I/O bandwidth is split up among all units within one slice relative to their block I/O
weight.

While C<StartupBlockIOWeight> only
applies to the startup phase of the system,
C<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
C<BlockIOAccounting=yes>.

These settings are deprecated. Use C<IOWeight> and C<StartupIOWeight>
instead. I< Optional. Type uniline.  > 

=head2 BlockIODeviceWeight

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 C<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.

Implies
C<BlockIOAccounting=yes>.

This setting is deprecated. Use C<IODeviceWeight> instead. I< Optional. Type uniline.  > 

=head2 BlockIOReadBandwidth

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
C<blkio.throttle.read_bps_device> and C<blkio.throttle.write_bps_device>
control group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For
details about these control group attributes, see blkio-controller.txt.

Implies
C<BlockIOAccounting=yes>.

These settings are deprecated. Use C<IOReadBandwidthMax> and
C<IOWriteBandwidthMax> instead. I< Optional. Type uniline.  > 

=head2 BlockIOWriteBandwidth

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
C<blkio.throttle.read_bps_device> and C<blkio.throttle.write_bps_device>
control group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For
details about these control group attributes, see blkio-controller.txt.

Implies
C<BlockIOAccounting=yes>.

These settings are deprecated. Use C<IOReadBandwidthMax> and
C<IOWriteBandwidthMax> instead. I< Optional. Type uniline.  > 

=head2 WorkingDirectory

Takes a directory path relative to the service's root directory specified by
C<RootDirectory>, or the special value C<~>. Sets the working directory for
executed processes. If set to C<~>, the home directory of the user specified in
C<User> is used. If not set, defaults to the root directory when systemd is running as a
system instance and the respective user's home directory if run as user. If the setting is prefixed with the
C<-> character, a missing working directory is not considered fatal. If
C<RootDirectory>/C<RootImage> is not set, then
C<WorkingDirectory> is relative to the root of the system running the service manager.  Note
that setting this parameter might result in additional dependencies to be added to the unit (see
above). I< Optional. Type uniline.  > 

=head2 RootDirectory

Takes a directory path relative to the host's root directory (i.e. the root of the system
running the service manager). Sets the root directory for executed processes, with the L<chroot(2)> system
call. If this is used, it must be ensured that the process binary and all its auxiliary files are available in
the chroot() jail. Note that setting this parameter might result in additional
dependencies to be added to the unit (see above).

The C<MountAPIVFS> and C<PrivateUsers> settings are particularly useful
in conjunction with C<RootDirectory>. For details, see below. I< Optional. Type uniline.  > 

=head2 RootImage

Takes a path to a block device node or regular file as argument. This call is similar to
C<RootDirectory> however mounts a file system hierarchy from a block device node or loopback
file instead of a directory. The device node or file system image file needs to contain a file system without a
partition table, or a file system within an MBR/MS-DOS or GPT partition table with only a single
Linux-compatible partition, or a set of file systems within a GPT partition table that follows the Discoverable Partitions
Specification.

When C<DevicePolicy> is set to C<closed> or C<strict>,
or set to C<auto> and C<DeviceAllow> is set, then this setting adds
/dev/loop-control with C<rw> mode, C<block-loop> and
C<block-blkext> with C<rwm> mode to C<DeviceAllow>. See
L<systemd.resource-control(5)>
for the details about C<DevicePolicy> or C<DeviceAllow>. Also, see
C<PrivateDevices> below, as it may change the setting of C<DevicePolicy>.
I< Optional. Type uniline.  > 

=head2 MountAPIVFS

Takes a boolean argument. If on, a private mount namespace for the unit's processes is created
and the API file systems /proc, /sys, and /dev
are mounted inside of it, unless they are already mounted. Note that this option has no effect unless used in
conjunction with C<RootDirectory>/C<RootImage> as these three mounts are
generally mounted in the host anyway, and unless the root directory is changed, the private mount namespace
will be a 1:1 copy of the host's, and include these three mounts. Note that the /dev file
system of the host is bind mounted if this option is used without C<PrivateDevices>. To run
the service with a private, minimal version of /dev/, combine this option with
C<PrivateDevices>. I< Optional. Type boolean.  > 

=head2 BindPaths

Configures unit-specific bind mounts. A bind mount makes a particular file or directory
available at an additional place in the unit's view of the file system. Any bind mounts created with this
option are specific to the unit, and are not visible in the host's mount table. This option expects a
whitespace separated list of bind mount definitions. Each definition consists of a colon-separated triple of
source path, destination path and option string, where the latter two are optional. If only a source path is
specified the source and destination is taken to be the same. The option string may be either
C<rbind> or C<norbind> for configuring a recursive or non-recursive bind
mount. If the destination path is omitted, the option string must be omitted too.
Each bind mount definition may be prefixed with C<->, in which case it will be ignored
when its source path does not exist.

C<BindPaths> creates regular writable bind mounts (unless the source file system mount
is already marked read-only), while C<BindReadOnlyPaths> creates read-only bind mounts. These
settings may be used more than once, each usage appends to the unit's list of bind mounts. If the empty string
is assigned to either of these two options the entire list of bind mounts defined prior to this is reset. Note
that in this case both read-only and regular bind mounts are reset, regardless which of the two settings is
used.

This option is particularly useful when C<RootDirectory>/C<RootImage>
is used. In this case the source path refers to a path on the host file system, while the destination path
refers to a path below the root directory of the unit. I< Optional. Type list of uniline.  > 

=head2 BindReadOnlyPaths

Configures unit-specific bind mounts. A bind mount makes a particular file or directory
available at an additional place in the unit's view of the file system. Any bind mounts created with this
option are specific to the unit, and are not visible in the host's mount table. This option expects a
whitespace separated list of bind mount definitions. Each definition consists of a colon-separated triple of
source path, destination path and option string, where the latter two are optional. If only a source path is
specified the source and destination is taken to be the same. The option string may be either
C<rbind> or C<norbind> for configuring a recursive or non-recursive bind
mount. If the destination path is omitted, the option string must be omitted too.
Each bind mount definition may be prefixed with C<->, in which case it will be ignored
when its source path does not exist.

C<BindPaths> creates regular writable bind mounts (unless the source file system mount
is already marked read-only), while C<BindReadOnlyPaths> creates read-only bind mounts. These
settings may be used more than once, each usage appends to the unit's list of bind mounts. If the empty string
is assigned to either of these two options the entire list of bind mounts defined prior to this is reset. Note
that in this case both read-only and regular bind mounts are reset, regardless which of the two settings is
used.

This option is particularly useful when C<RootDirectory>/C<RootImage>
is used. In this case the source path refers to a path on the host file system, while the destination path
refers to a path below the root directory of the unit. I< Optional. Type list of uniline.  > 

=head2 User

Set the UNIX user or group that the processes are executed as, respectively. Takes a single
user or group name, or a numeric ID as argument. For system services (services run by the system service
manager, i.e. managed by PID 1) and for user services of the root user (services managed by root's instance of
systemd --user), the default is C<root>, but C<User> may be
used to specify a different user. For user services of any other user, switching user identity is not
permitted, hence the only valid setting is the same user the user's service manager is running as. If no group
is set, the default group of the user is used. This setting does not affect commands whose command line is
prefixed with C<+>.

Note that restrictions on the user/group name syntax are enforced: the specified name must consist only
of the characters a-z, A-Z, 0-9, C<_> and C<->, except for the first character
which must be one of a-z, A-Z or C<_> (i.e. numbers and C<-> are not permitted
as first character). The user/group name must have at least one character, and at most 31. These restrictions
are enforced in order to avoid ambiguities and to ensure user/group names and unit files remain portable among
Linux systems.

When used in conjunction with C<DynamicUser> the user/group name specified is
dynamically allocated at the time the service is started, and released at the time the service is stopped —
unless it is already allocated statically (see below). If C<DynamicUser> is not used the
specified user and group must have been created statically in the user database no later than the moment the
service is started, for example using the
L<sysusers.d(5)> facility, which
is applied at boot or package install time. I< Optional. Type uniline.  > 

=head2 Group

Set the UNIX user or group that the processes are executed as, respectively. Takes a single
user or group name, or a numeric ID as argument. For system services (services run by the system service
manager, i.e. managed by PID 1) and for user services of the root user (services managed by root's instance of
systemd --user), the default is C<root>, but C<User> may be
used to specify a different user. For user services of any other user, switching user identity is not
permitted, hence the only valid setting is the same user the user's service manager is running as. If no group
is set, the default group of the user is used. This setting does not affect commands whose command line is
prefixed with C<+>.

Note that restrictions on the user/group name syntax are enforced: the specified name must consist only
of the characters a-z, A-Z, 0-9, C<_> and C<->, except for the first character
which must be one of a-z, A-Z or C<_> (i.e. numbers and C<-> are not permitted
as first character). The user/group name must have at least one character, and at most 31. These restrictions
are enforced in order to avoid ambiguities and to ensure user/group names and unit files remain portable among
Linux systems.

When used in conjunction with C<DynamicUser> the user/group name specified is
dynamically allocated at the time the service is started, and released at the time the service is stopped —
unless it is already allocated statically (see below). If C<DynamicUser> is not used the
specified user and group must have been created statically in the user database no later than the moment the
service is started, for example using the
L<sysusers.d(5)> facility, which
is applied at boot or package install time. I< Optional. Type uniline.  > 

=head2 DynamicUser

Takes a boolean parameter. If set, a UNIX user and group pair is allocated dynamically when the
unit is started, and released as soon as it is stopped. The user and group will not be added to
/etc/passwd or /etc/group, but are managed transiently during
runtime. The L<nss-systemd(8)>
glibc NSS module provides integration of these dynamic users/groups into the system's user and group
databases. The user and group name to use may be configured via C<User> and
C<Group> (see above). If these options are not used and dynamic user/group allocation is
enabled for a unit, the name of the dynamic user/group is implicitly derived from the unit name. If the unit
name without the type suffix qualifies as valid user name it is used directly, otherwise a name incorporating a
hash of it is used. If a statically allocated user or group of the configured name already exists, it is used
and no dynamic user/group is allocated. Note that if C<User> is specified and the static group
with the name exists, then it is required that the static user with the name already exists. Similarly, if
C<Group> is specified and the static user with the name exists, then it is required that the
static group with the name already exists. Dynamic users/groups are allocated from the UID/GID range
61184…65519. It is recommended to avoid this range for regular system or login users.  At any point in time
each UID/GID from this range is only assigned to zero or one dynamically allocated users/groups in
use. However, UID/GIDs are recycled after a unit is terminated. Care should be taken that any processes running
as part of a unit for which dynamic users/groups are enabled do not leave files or directories owned by these
users/groups around, as a different unit might get the same UID/GID assigned later on, and thus gain access to
these files or directories. If C<DynamicUser> is enabled, C<RemoveIPC>,
C<PrivateTmp> are implied. This ensures that the lifetime of IPC objects and temporary files
created by the executed processes is bound to the runtime of the service, and hence the lifetime of the dynamic
user/group. Since /tmp and /var/tmp are usually the only
world-writable directories on a system this ensures that a unit making use of dynamic user/group allocation
cannot leave files around after unit termination. Moreover C<ProtectSystem=strict> and
C<ProtectHome=read-only> are implied, thus prohibiting the service to write to arbitrary file
system locations. In order to allow the service to write to certain directories, they have to be whitelisted
using C<ReadWritePaths>, but care must be taken so that UID/GID recycling doesn't create
security issues involving files created by the service. Use C<RuntimeDirectory> (see below) in
order to assign a writable runtime directory to a service, owned by the dynamic user/group and removed
automatically when the unit is terminated. Use C<StateDirectory>,
C<CacheDirectory> and C<LogsDirectory> in order to assign a set of writable
directories for specific purposes to the service in a way that they are protected from vulnerabilities due to
UID reuse (see below). Defaults to off. I< Optional. Type boolean.  > 

=head2 SupplementaryGroups

Sets the supplementary Unix groups the processes are executed as. This takes a space-separated
list of group names or IDs. This option may be specified more than once, in which case all listed groups are
set as supplementary groups. When the empty string is assigned, the list of supplementary groups is reset, and
all assignments prior to this one will have no effect. In any way, this option does not override, but extends
the list of supplementary groups configured in the system group database for the user. This does not affect
commands prefixed with C<+>. I< Optional. Type list of uniline.  > 

=head2 PAMName

Sets the PAM service name to set up a session as. If set, the executed process will be
registered as a PAM session under the specified service name. This is only useful in conjunction with the
C<User> setting, and is otherwise ignored. If not set, no PAM session will be opened for the
executed processes. See L<pam(8)> for
details.

Note that for each unit making use of this option a PAM session handler process will be maintained as
part of the unit and stays around as long as the unit is active, to ensure that appropriate actions can be
taken when the unit and hence the PAM session terminates. This process is named C<(sd-pam)> and
is an immediate child process of the unit's main process.

Note that when this option is used for a unit it is very likely (depending on PAM configuration) that the
main unit process will be migrated to its own session scope unit when it is activated. This process will hence
be associated with two units: the unit it was originally started from (and for which
C<PAMName> was configured), and the session scope unit. Any child processes of that process
will however be associated with the session scope unit only. This has implications when used in combination
with C<NotifyAccess>C<all>, as these child processes will not be able to affect
changes in the original unit through notification messages. These messages will be considered belonging to the
session scope unit and not the original unit. It is hence not recommended to use C<PAMName> in
combination with C<NotifyAccess>C<all>. I< Optional. Type uniline.  > 

=head2 CapabilityBoundingSet

Controls which capabilities to include in the capability bounding set for the executed
process. See L<capabilities(7)> for
details. Takes a whitespace-separated list of capability names, e.g. C<CAP_SYS_ADMIN>,
C<CAP_DAC_OVERRIDE>, C<CAP_SYS_PTRACE>. Capabilities listed will be
included in the bounding set, all others are removed. If the list of capabilities is prefixed with
C<~>, all but the listed capabilities will be included, the effect of the assignment
inverted. Note that this option also affects the respective capabilities in the effective, permitted and
inheritable capability sets. If this option is not used, the capability bounding set is not modified on process
execution, hence no limits on the capabilities of the process are enforced. This option may appear more than
once, in which case the bounding sets are merged by C<OR>, or by C<AND> if
the lines are prefixed with C<~> (see below). If the empty string is assigned to this option,
the bounding set is reset to the empty capability set, and all prior settings have no effect.  If set to
C<~> (without any further argument), the bounding set is reset to the full set of available
capabilities, also undoing any previous settings. This does not affect commands prefixed with
C<+>.

Example: if a unit has the following,

    CapabilityBoundingSet=CAP_A CAP_B
    CapabilityBoundingSet=CAP_B CAP_C

then C<CAP_A>, C<CAP_B>, and C<CAP_C> are set.
If the second line is prefixed with C<~>, e.g.,

    CapabilityBoundingSet=CAP_A CAP_B
    CapabilityBoundingSet=~CAP_B CAP_C

then, only C<CAP_A> is set. I< Optional. Type uniline.  > 

=head2 AmbientCapabilities

Controls which capabilities to include in the ambient capability set for the executed
process. Takes a whitespace-separated list of capability names, e.g. C<CAP_SYS_ADMIN>,
C<CAP_DAC_OVERRIDE>, C<CAP_SYS_PTRACE>. This option may appear more than
once in which case the ambient capability sets are merged (see the above examples in
C<CapabilityBoundingSet>). If the list of capabilities is prefixed with C<~>,
all but the listed capabilities will be included, the effect of the assignment inverted. If the empty string is
assigned to this option, the ambient capability set is reset to the empty capability set, and all prior
settings have no effect.  If set to C<~> (without any further argument), the ambient capability
set is reset to the full set of available capabilities, also undoing any previous settings. Note that adding
capabilities to ambient capability set adds them to the process's inherited capability set.  

Ambient capability sets are useful if you want to execute a process as a non-privileged user but still want to
give it some capabilities.  Note that in this case option C<keep-caps> is automatically added
to C<SecureBits> to retain the capabilities over the user
change. C<AmbientCapabilities> does not affect commands prefixed with
C<+>. I< Optional. Type uniline.  > 

=head2 NoNewPrivileges

Takes a boolean argument. If true, ensures that the service process and all its children can
never gain new privileges through execve() (e.g. via setuid or setgid bits, or filesystem
capabilities). This is the simplest and most effective way to ensure that a process and its children can never
elevate privileges again. Defaults to false, but certain settings override this and ignore the value of this
setting.  This is the case when C<SystemCallFilter>,
C<SystemCallArchitectures>, C<RestrictAddressFamilies>,
C<RestrictNamespaces>, C<PrivateDevices>,
C<ProtectKernelTunables>, C<ProtectKernelModules>,
C<MemoryDenyWriteExecute>, C<RestrictRealtime>, or
C<LockPersonality> are specified. Note that even if this setting is overridden by them,
systemctl show shows the original value of this setting. Also see
No New Privileges
Flag.  I< Optional. Type boolean.  > 

=head2 SecureBits

Controls the secure bits set for the executed process. Takes a space-separated combination of
options from the following list: C<keep-caps>, C<keep-caps-locked>,
C<no-setuid-fixup>, C<no-setuid-fixup-locked>, C<noroot>, and
C<noroot-locked>.  This option may appear more than once, in which case the secure bits are
ORed. If the empty string is assigned to this option, the bits are reset to 0. This does not affect commands
prefixed with C<+>.  See L<capabilities(7)> for
details. I< Optional. Type uniline.  > 

=head2 SELinuxContext

Set the SELinux security context of the executed process. If set, this will override the
automated domain transition. However, the policy still needs to authorize the transition. This directive is
ignored if SELinux is disabled. If prefixed by C<->, all errors will be ignored. This does not
affect commands prefixed with C<+>.  See L<setexeccon(3)> for
details. I< Optional. Type uniline.  > 

=head2 AppArmorProfile

Takes a profile name as argument. The process executed by the unit will switch to this profile
when started.  Profiles must already be loaded in the kernel, or the unit will fail. This result in a non
operation if AppArmor is not enabled. If prefixed by C<->, all errors will be ignored. This
does not affect commands prefixed with C<+>. I< Optional. Type uniline.  > 

=head2 SmackProcessLabel

Takes a C<SMACK64> security label as argument. The process executed by the unit
will be started under this label and SMACK will decide whether the process is allowed to run or not, based on
it. The process will continue to run under the label specified here unless the executable has its own
C<SMACK64EXEC> label, in which case the process will transition to run under that label. When not
specified, the label that systemd is running under is used. This directive is ignored if SMACK is
disabled.

The value may be prefixed by C<->, in which case all errors will be ignored. An empty
value may be specified to unset previous assignments. This does not affect commands prefixed with
C<+>. I< Optional. Type uniline.  > 

=head2 LimitCPU

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitFSIZE

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitDATA

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitSTACK

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitCORE

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitRSS

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitNOFILE

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitAS

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitNPROC

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitMEMLOCK

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitLOCKS

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitSIGPENDING

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitMSGQUEUE

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitNICE

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitRTPRIO

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 LimitRTTIME

Set soft and hard limits on various resources for executed processes. See
L<setrlimit(2)> for details on
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
specific soft and hard limit to the same value, or as colon-separated pair C<soft:hard> to set
both limits individually (e.g. C<LimitAS=4G:16G>).  Use the string C<infinity> to
configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
the usual time units ms, s, min, h and so on may be used (see
L<systemd.time(7)> for
details). Note that if no time unit is specified for C<LimitCPU> the default unit of seconds
is implied, while for C<LimitRTTIME> the default unit of microseconds is implied. Also, note
that the effective granularity of the limits might influence their enforcement. For example, time limits
specified for C<LimitCPU> will be rounded up implicitly to multiples of 1s. For
C<LimitNICE> the value may be specified in two syntaxes: if prefixed with C<+>
or C<->, the value is understood as regular Linux nice value in the range -20..19. If not
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
equivalent to 1).

Note that most process resource limits configured with these options are per-process, and processes may
fork in order to acquire a new set of resources that are accounted independently of the original process, and
may thus escape limits set. Also note that C<LimitRSS> is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource controls listed in
L<systemd.resource-control(5)>
over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
are generally more expressive. For example, C<MemoryLimit> is a more powerful (and working)
replacement for C<LimitRSS>.

For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
per-user instance of
L<systemd(1)>), these limits are
bound by (possibly more restrictive) per-user limits enforced by the OS.

Resource limits not configured explicitly for a unit default to the value configured in the various
C<DefaultLimitCPU>, C<DefaultLimitFSIZE>, … options available in
L<systemd-system.conf(5)>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
services, see above). I< Optional. Type uniline.  > 

=head2 UMask

Controls the file mode creation mask. Takes an access mode in octal notation. See
L<umask(2)> for details. Defaults
to 0022. I< Optional. Type uniline.  > 

=head2 KeyringMode

Controls how the kernel session keyring is set up for the service (see L<session-keyring(7)> for
details on the session keyring). Takes one of C<inherit>, C<private>,
C<shared>. If set to C<inherit> no special keyring setup is done, and the kernel's
default behaviour is applied. If C<private> is used a new session keyring is allocated when a
service process is invoked, and it is not linked up with any user keyring. This is the recommended setting for
system services, as this ensures that multiple services running under the same system user ID (in particular
the root user) do not share their key material among each other. If C<shared> is used a new
session keyring is allocated as for C<private>, but the user keyring of the user configured with
C<User> is linked into it, so that keys assigned to the user may be requested by the unit's
processes. In this modes multiple units running processes under the same user ID may share key material. Unless
C<inherit> is selected the unique invocation ID for the unit (see below) is added as a protected
key by the name C<invocation_id> to the newly created session keyring. Defaults to
C<private> for services of the system service manager and to C<inherit> for
non-service units and for services of the user service manager. I< Optional. Type enum. choice: 'inherit', 'private', 'shared'.  > 

=head2 OOMScoreAdjust

Sets the adjustment level for the Out-Of-Memory killer for executed processes. Takes an integer
between -1000 (to disable OOM killing for this process) and 1000 (to make killing of this process under memory
pressure very likely). See proc.txt for
details. I< Optional. Type integer.  > 

=head2 TimerSlackNSec

Sets the timer slack in nanoseconds for the executed processes. The timer slack controls the
accuracy of wake-ups triggered by timers. See
L<prctl(2)> for more
information. Note that in contrast to most other time span definitions this parameter takes an integer value in
nano-seconds if no unit is specified. The usual time units are understood too. I< Optional. Type uniline.  > 

=head2 Personality

Controls which kernel architecture L<uname(2)> shall report,
when invoked by unit processes. Takes one of the architecture identifiers C<x86>,
C<x86-64>, C<ppc>, C<ppc-le>, C<ppc64>,
C<ppc64-le>, C<s390> or C<s390x>. Which personality
architectures are supported depends on the system architecture. Usually the 64bit versions of the various
system architectures support their immediate 32bit personality architecture counterpart, but no others. For
example, C<x86-64> systems support the C<x86-64> and
C<x86> personalities but no others. The personality feature is useful when running 32-bit
services on a 64-bit host system. If not specified, the personality is left unmodified and thus reflects the
personality of the host system's kernel. I< Optional. Type enum. choice: 'x86', 'x86-64', 'ppc', 'ppc-le', 'ppc64', 'ppc64-le', 's390', 's390x'.  > 

=head2 IgnoreSIGPIPE

Takes a boolean argument. If true, causes C<SIGPIPE> to be ignored in the
executed process. Defaults to true because C<SIGPIPE> generally is useful only in shell
pipelines. I< Optional. Type boolean.  > 

=head2 Nice

Sets the default nice level (scheduling priority) for executed processes. Takes an integer
between -20 (highest priority) and 19 (lowest priority). See
L<setpriority(2)> for
details. I< Optional. Type integer.  > 

=head2 CPUSchedulingPolicy

Sets the CPU scheduling policy for executed processes. Takes one of C<other>,
C<batch>, C<idle>, C<fifo> or C<rr>. See
L<sched_setscheduler(2)> for
details. I< Optional. Type enum. choice: 'other', 'batch', 'idle', 'fifo', 'rr'.  > 

=head2 CPUSchedulingPriority

Sets the CPU scheduling priority for executed processes. The available priority range depends
on the selected CPU scheduling policy (see above). For real-time scheduling policies an integer between 1
(lowest priority) and 99 (highest priority) can be used. See
L<sched_setscheduler(2)> for
details. I< Optional. Type uniline.  > 

=head2 CPUSchedulingResetOnFork

Takes a boolean argument. If true, elevated CPU scheduling priorities and policies will be
reset when the executed processes fork, and can hence not leak into child processes. See
L<sched_setscheduler(2)> for
details. Defaults to false. I< Optional. Type boolean.  > 

=head2 CPUAffinity

Controls the CPU affinity of the executed processes. 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.  This option may be specified more than once, in which case the specified CPU affinity masks are
merged. If the empty string is assigned, the mask is reset, all assignments prior to this will have no
effect. See
L<sched_setaffinity(2)> for
details. I< Optional. Type list of uniline.  > 

=head2 IOSchedulingClass

Sets the I/O scheduling class for executed processes. Takes an integer between 0 and 3 or one
of the strings C<none>, C<realtime>, C<best-effort> or
C<idle>. If the empty string is assigned to this option, all prior assignments to both
C<IOSchedulingClass> and C<IOSchedulingPriority> have no effect. See
L<ioprio_set(2)> for
details. I< Optional. Type enum. choice: '0', '1', '2', '3', 'none', 'realtime', 'best-effort', 'idle'.  > 

=head2 IOSchedulingPriority

Sets the I/O scheduling priority for executed processes. Takes an integer between 0 (highest
priority) and 7 (lowest priority). The available priorities depend on the selected I/O scheduling class (see
above). If the empty string is assigned to this option, all prior assignments to both
C<IOSchedulingClass> and C<IOSchedulingPriority> have no effect.
See L<ioprio_set(2)> for
details. I< Optional. Type integer.  > 

=head2 ProtectSystem

Takes a boolean argument or the special values C<full> or
C<strict>. If true, mounts the /usr and /boot
directories read-only for processes invoked by this unit. If set to C<full>, the
/etc directory is mounted read-only, too. If set to C<strict> the entire
file system hierarchy is mounted read-only, except for the API file system subtrees /dev,
/proc and /sys (protect these directories using
C<PrivateDevices>, C<ProtectKernelTunables>,
C<ProtectControlGroups>). This setting ensures that any modification of the vendor-supplied
operating system (and optionally its configuration, and local mounts) is prohibited for the service.  It is
recommended to enable this setting for all long-running services, unless they are involved with system updates
or need to modify the operating system in other ways. If this option is used,
C<ReadWritePaths> may be used to exclude specific directories from being made read-only. This
setting is implied if C<DynamicUser> is set. This setting cannot ensure protection in all
cases. In general it has the same limitations as C<ReadOnlyPaths>, see below. Defaults to
off. I< Optional. Type enum. choice: 'no', 'yes', 'full', 'strict'.  > 

=head2 ProtectHome

Takes a boolean argument or the special values C<read-only> or
C<tmpfs>. If true, the directories /home, /root and
/run/user are made inaccessible and empty for processes invoked by this unit. If set to
C<read-only>, the three directories are made read-only instead. If set to C<tmpfs>,
temporary file systems are mounted on the three directories in read-only mode. The value C<tmpfs>
is useful to hide home directories not relevant to the processes invoked by the unit, while necessary directories
are still visible by combining with C<BindPaths> or C<BindReadOnlyPaths>.

Setting this to C<yes> is mostly equivalent to set the three directories in
C<InaccessiblePaths>. Similarly, C<read-only> is mostly equivalent to
C<ReadOnlyPaths>, and C<tmpfs> is mostly equivalent to
C<TemporaryFileSystem>.

 It is recommended to enable this setting for all long-running services (in particular network-facing
ones), to ensure they cannot get access to private user data, unless the services actually require access to
the user's private data. This setting is implied if C<DynamicUser> is set. This setting cannot
ensure protection in all cases. In general it has the same limitations as C<ReadOnlyPaths>,
see below. I< Optional. Type enum. choice: 'no', 'yes', 'read-only', 'tmpfs'.  > 

=head2 RuntimeDirectory

These options take a whitespace-separated list of directory names. The specified directory
names must be relative, and may not include C<..>. If set, one or more
directories by the specified names will be created (including their parents) below the locations
defined in the following table, when the unit is started. Also, the corresponding environment variable
is defined with the full path of directories. If multiple directories are set, then int the environment variable
the paths are concatenated with colon (C<:>).

In case of C<RuntimeDirectory> the lowest subdirectories are removed when the unit is
stopped. It is possible to preserve the specified directories in this case if
C<RuntimeDirectoryPreserve> is configured to C<restart> or C<yes>
(see below). The directories specified with C<StateDirectory>,
C<CacheDirectory>, C<LogsDirectory>,
C<ConfigurationDirectory> are not removed when the unit is stopped.

Except in case of C<ConfigurationDirectory>, the innermost specified directories will be
owned by the user and group specified in C<User> and C<Group>. If the
specified directories already exist and their owning user or group do not match the configured ones, all files
and directories below the specified directories as well as the directories themselves will have their file
ownership recursively changed to match what is configured. As an optimization, if the specified directories are
already owned by the right user and group, files and directories below of them are left as-is, even if they do
not match what is requested. The innermost specified directories will have their access mode adjusted to the
what is specified in C<RuntimeDirectoryMode>, C<StateDirectoryMode>,
C<CacheDirectoryMode>, C<LogsDirectoryMode> and
C<ConfigurationDirectoryMode>.

These options imply C<BindPaths> for the specified paths. When combined with
C<RootDirectory> or C<RootImage> these paths always reside on the host and
are mounted from there into the unit's file system namespace.

If C<DynamicUser> is used in conjunction with C<StateDirectory>,
C<CacheDirectory> and C<LogsDirectory> is slightly altered: the directories
are created below /var/lib/private, /var/cache/private and
/var/log/private, respectively, which are host directories made inaccessible to
unprivileged users, which ensures that access to these directories cannot be gained through dynamic user ID
recycling. Symbolic links are created to hide this difference in behaviour. Both from perspective of the host
and from inside the unit, the relevant directories hence always appear directly below
/var/lib, /var/cache and /var/log.

Use C<RuntimeDirectory> to manage one or more runtime directories for the unit and bind
their lifetime to the daemon runtime. This is particularly useful for unprivileged daemons that cannot create
runtime directories in /run due to lack of privileges, and to make sure the runtime
directory is cleaned up automatically after use. For runtime directories that require more complex or different
configuration or lifetime guarantees, please consider using
L<tmpfiles.d(5)>.

Example: if a system service unit has the following,

    RuntimeDirectory=foo/bar baz

the service manager creates /run/foo (if it does not exist),
/run/foo/bar, and /run/baz. The directories
/run/foo/bar and /run/baz except /run/foo are
owned by the user and group specified in C<User> and C<Group>, and removed
when the service is stopped.

Example: if a system service unit has the following,

    RuntimeDirectory=foo/bar
    StateDirectory=aaa/bbb ccc

then the environment variable C<RUNTIME_DIRECTORY> is set with C</run/foo/bar>, and
C<STATE_DIRECTORY> is set with C</var/lib/aaa/bbb:/var/lib/ccc>. I< Optional. Type uniline.  > 

=head2 StateDirectory

These options take a whitespace-separated list of directory names. The specified directory
names must be relative, and may not include C<..>. If set, one or more
directories by the specified names will be created (including their parents) below the locations
defined in the following table, when the unit is started. Also, the corresponding environment variable
is defined with the full path of directories. If multiple directories are set, then int the environment variable
the paths are concatenated with colon (C<:>).

In case of C<RuntimeDirectory> the lowest subdirectories are removed when the unit is
stopped. It is possible to preserve the specified directories in this case if
C<RuntimeDirectoryPreserve> is configured to C<restart> or C<yes>
(see below). The directories specified with C<StateDirectory>,
C<CacheDirectory>, C<LogsDirectory>,
C<ConfigurationDirectory> are not removed when the unit is stopped.

Except in case of C<ConfigurationDirectory>, the innermost specified directories will be
owned by the user and group specified in C<User> and C<Group>. If the
specified directories already exist and their owning user or group do not match the configured ones, all files
and directories below the specified directories as well as the directories themselves will have their file
ownership recursively changed to match what is configured. As an optimization, if the specified directories are
already owned by the right user and group, files and directories below of them are left as-is, even if they do
not match what is requested. The innermost specified directories will have their access mode adjusted to the
what is specified in C<RuntimeDirectoryMode>, C<StateDirectoryMode>,
C<CacheDirectoryMode>, C<LogsDirectoryMode> and
C<ConfigurationDirectoryMode>.

These options imply C<BindPaths> for the specified paths. When combined with
C<RootDirectory> or C<RootImage> these paths always reside on the host and
are mounted from there into the unit's file system namespace.

If C<DynamicUser> is used in conjunction with C<StateDirectory>,
C<CacheDirectory> and C<LogsDirectory> is slightly altered: the directories
are created below /var/lib/private, /var/cache/private and
/var/log/private, respectively, which are host directories made inaccessible to
unprivileged users, which ensures that access to these directories cannot be gained through dynamic user ID
recycling. Symbolic links are created to hide this difference in behaviour. Both from perspective of the host
and from inside the unit, the relevant directories hence always appear directly below
/var/lib, /var/cache and /var/log.

Use C<RuntimeDirectory> to manage one or more runtime directories for the unit and bind
their lifetime to the daemon runtime. This is particularly useful for unprivileged daemons that cannot create
runtime directories in /run due to lack of privileges, and to make sure the runtime
directory is cleaned up automatically after use. For runtime directories that require more complex or different
configuration or lifetime guarantees, please consider using
L<tmpfiles.d(5)>.

Example: if a system service unit has the following,

    RuntimeDirectory=foo/bar baz

the service manager creates /run/foo (if it does not exist),
/run/foo/bar, and /run/baz. The directories
/run/foo/bar and /run/baz except /run/foo are
owned by the user and group specified in C<User> and C<Group>, and removed
when the service is stopped.

Example: if a system service unit has the following,

    RuntimeDirectory=foo/bar
    StateDirectory=aaa/bbb ccc

then the environment variable C<RUNTIME_DIRECTORY> is set with C</run/foo/bar>, and
C<STATE_DIRECTORY> is set with C</var/lib/aaa/bbb:/var/lib/ccc>. I< Optional. Type uniline.  > 

=head2 CacheDirectory

These options take a whitespace-separated list of directory names. The specified directory
names must be relative, and may not include C<..>. If set, one or more
directories by the specified names will be created (including their parents) below the locations
defined in the following table, when the unit is started. Also, the corresponding environment variable
is defined with the full path of directories. If multiple directories are set, then int the environment variable
the paths are concatenated with colon (C<:>).

In case of C<RuntimeDirectory> the lowest subdirectories are removed when the unit is
stopped. It is possible to preserve the specified directories in this case if
C<RuntimeDirectoryPreserve> is configured to C<restart> or C<yes>
(see below). The directories specified with C<StateDirectory>,
C<CacheDirectory>, C<LogsDirectory>,
C<ConfigurationDirectory> are not removed when the unit is stopped.

Except in case of C<ConfigurationDirectory>, the innermost specified directories will be
owned by the user and group specified in C<User> and C<Group>. If the
specified directories already exist and their owning user or group do not match the configured ones, all files
and directories below the specified directories as well as the directories themselves will have their file
ownership recursively changed to match what is configured. As an optimization, if the specified directories are
already owned by the right user and group, files and directories below of them are left as-is, even if they do
not match what is requested. The innermost specified directories will have their access mode adjusted to the
what is specified in C<RuntimeDirectoryMode>, C<StateDirectoryMode>,
C<CacheDirectoryMode>, C<LogsDirectoryMode> and
C<ConfigurationDirectoryMode>.

These options imply C<BindPaths> for the specified paths. When combined with
C<RootDirectory> or C<RootImage> these paths always reside on the host and
are mounted from there into the unit's file system namespace.

If C<DynamicUser> is used in conjunction with C<StateDirectory>,
C<CacheDirectory> and C<LogsDirectory> is slightly altered: the directories
are created below /var/lib/private, /var/cache/private and
/var/log/private, respectively, which are host directories made inaccessible to
unprivileged users, which ensures that access to these directories cannot be gained through dynamic user ID
recycling. Symbolic links are created to hide this difference in behaviour. Both from perspective of the host
and from inside the unit, the relevant directories hence always appear directly below
/var/lib, /var/cache and /var/log.

Use C<RuntimeDirectory> to manage one or more runtime directories for the unit and bind
their lifetime to the daemon runtime. This is particularly useful for unprivileged daemons that cannot create
runtime directories in /run due to lack of privileges, and to make sure the runtime
directory is cleaned up automatically after use. For runtime directories that require more complex or different
configuration or lifetime guarantees, please consider using
L<tmpfiles.d(5)>.

Example: if a system service unit has the following,

    RuntimeDirectory=foo/bar baz

the service manager creates /run/foo (if it does not exist),
/run/foo/bar, and /run/baz. The directories
/run/foo/bar and /run/baz except /run/foo are
owned by the user and group specified in C<User> and C<Group>, and removed
when the service is stopped.

Example: if a system service unit has the following,

    RuntimeDirectory=foo/bar
    StateDirectory=aaa/bbb ccc

then the environment variable C<RUNTIME_DIRECTORY> is set with C</run/foo/bar>, and
C<STATE_DIRECTORY> is set with C</var/lib/aaa/bbb:/var/lib/ccc>. I< Optional. Type uniline.  > 

=head2 LogsDirectory

These options take a whitespace-separated list of directory names. The specified directory
names must be relative, and may not include C<..>. If set, one or more
directories by the specified names will be created (including their parents) below the locations
defined in the following table, when the unit is started. Also, the corresponding environment variable
is defined with the full path of directories. If multiple directories are set, then int the environment variable
the paths are concatenated with colon (C<:>).

In case of C<RuntimeDirectory> the lowest subdirectories are removed when the unit is
stopped. It is possible to preserve the specified directories in this case if
C<RuntimeDirectoryPreserve> is configured to C<restart> or C<yes>
(see below). The directories specified with C<StateDirectory>,
C<CacheDirectory>, C<LogsDirectory>,
C<ConfigurationDirectory> are not removed when the unit is stopped.

Except in case of C<ConfigurationDirectory>, the innermost specified directories will be
owned by the user and group specified in C<User> and C<Group>. If the
specified directories already exist and their owning user or group do not match the configured ones, all files
and directories below the specified directories as well as the directories themselves will have their file
ownership recursively changed to match what is configured. As an optimization, if the specified directories are
already owned by the right user and group, files and directories below of them are left as-is, even if they do
not match what is requested. The innermost specified directories will have their access mode adjusted to the
what is specified in C<RuntimeDirectoryMode>, C<StateDirectoryMode>,
C<CacheDirectoryMode>, C<LogsDirectoryMode> and
C<ConfigurationDirectoryMode>.

These options imply C<BindPaths> for the specified paths. When combined with
C<RootDirectory> or C<RootImage> these paths always reside on the host and
are mounted from there into the unit's file system namespace.

If C<DynamicUser> is used in conjunction with C<StateDirectory>,
C<CacheDirectory> and C<LogsDirectory> is slightly altered: the directories
are created below /var/lib/private, /var/cache/private and
/var/log/private, respectively, which are host directories made inaccessible to
unprivileged users, which ensures that access to these directories cannot be gained through dynamic user ID
recycling. Symbolic links are created to hide this difference in behaviour. Both from perspective of the host
and from inside the unit, the relevant directories hence always appear directly below
/var/lib, /var/cache and /var/log.

Use C<RuntimeDirectory> to manage one or more runtime directories for the unit and bind
their lifetime to the daemon runtime. This is particularly useful for unprivileged daemons that cannot create
runtime directories in /run due to lack of privileges, and to make sure the runtime
directory is cleaned up automatically after use. For runtime directories that require more complex or different
configuration or lifetime guarantees, please consider using
L<tmpfiles.d(5)>.

Example: if a system service unit has the following,

    RuntimeDirectory=foo/bar baz

the service manager creates /run/foo (if it does not exist),
/run/foo/bar, and /run/baz. The directories
/run/foo/bar and /run/baz except /run/foo are
owned by the user and group specified in C<User> and C<Group>, and removed
when the service is stopped.

Example: if a system service unit has the following,

    RuntimeDirectory=foo/bar
    StateDirectory=aaa/bbb ccc

then the environment variable C<RUNTIME_DIRECTORY> is set with C</run/foo/bar>, and
C<STATE_DIRECTORY> is set with C</var/lib/aaa/bbb:/var/lib/ccc>. I< Optional. Type uniline.  > 

=head2 ConfigurationDirectory

These options take a whitespace-separated list of directory names. The specified directory
names must be relative, and may not include C<..>. If set, one or more
directories by the specified names will be created (including their parents) below the locations
defined in the following table, when the unit is started. Also, the corresponding environment variable
is defined with the full path of directories. If multiple directories are set, then int the environment variable
the paths are concatenated with colon (C<:>).

In case of C<RuntimeDirectory> the lowest subdirectories are removed when the unit is
stopped. It is possible to preserve the specified directories in this case if
C<RuntimeDirectoryPreserve> is configured to C<restart> or C<yes>
(see below). The directories specified with C<StateDirectory>,
C<CacheDirectory>, C<LogsDirectory>,
C<ConfigurationDirectory> are not removed when the unit is stopped.

Except in case of C<ConfigurationDirectory>, the innermost specified directories will be
owned by the user and group specified in C<User> and C<Group>. If the
specified directories already exist and their owning user or group do not match the configured ones, all files
and directories below the specified directories as well as the directories themselves will have their file
ownership recursively changed to match what is configured. As an optimization, if the specified directories are
already owned by the right user and group, files and directories below of them are left as-is, even if they do
not match what is requested. The innermost specified directories will have their access mode adjusted to the
what is specified in C<RuntimeDirectoryMode>, C<StateDirectoryMode>,
C<CacheDirectoryMode>, C<LogsDirectoryMode> and
C<ConfigurationDirectoryMode>.

These options imply C<BindPaths> for the specified paths. When combined with
C<RootDirectory> or C<RootImage> these paths always reside on the host and
are mounted from there into the unit's file system namespace.

If C<DynamicUser> is used in conjunction with C<StateDirectory>,
C<CacheDirectory> and C<LogsDirectory> is slightly altered: the directories
are created below /var/lib/private, /var/cache/private and
/var/log/private, respectively, which are host directories made inaccessible to
unprivileged users, which ensures that access to these directories cannot be gained through dynamic user ID
recycling. Symbolic links are created to hide this difference in behaviour. Both from perspective of the host
and from inside the unit, the relevant directories hence always appear directly below
/var/lib, /var/cache and /var/log.

Use C<RuntimeDirectory> to manage one or more runtime directories for the unit and bind
their lifetime to the daemon runtime. This is particularly useful for unprivileged daemons that cannot create
runtime directories in /run due to lack of privileges, and to make sure the runtime
directory is cleaned up automatically after use. For runtime directories that require more complex or different
configuration or lifetime guarantees, please consider using
L<tmpfiles.d(5)>.

Example: if a system service unit has the following,

    RuntimeDirectory=foo/bar baz

the service manager creates /run/foo (if it does not exist),
/run/foo/bar, and /run/baz. The directories
/run/foo/bar and /run/baz except /run/foo are
owned by the user and group specified in C<User> and C<Group>, and removed
when the service is stopped.

Example: if a system service unit has the following,

    RuntimeDirectory=foo/bar
    StateDirectory=aaa/bbb ccc

then the environment variable C<RUNTIME_DIRECTORY> is set with C</run/foo/bar>, and
C<STATE_DIRECTORY> is set with C</var/lib/aaa/bbb:/var/lib/ccc>. I< Optional. Type uniline.  > 

=head2 RuntimeDirectoryMode

Specifies the access mode of the directories specified in C<RuntimeDirectory>,
C<StateDirectory>, C<CacheDirectory>, C<LogsDirectory>, or
C<ConfigurationDirectory>, respectively, as an octal number.  Defaults to
C<0755>. See "Permissions" in L<path_resolution(7)> for a
discussion of the meaning of permission bits. I< Optional. Type uniline.  > 

=head2 StateDirectoryMode

Specifies the access mode of the directories specified in C<RuntimeDirectory>,
C<StateDirectory>, C<CacheDirectory>, C<LogsDirectory>, or
C<ConfigurationDirectory>, respectively, as an octal number.  Defaults to
C<0755>. See "Permissions" in L<path_resolution(7)> for a
discussion of the meaning of permission bits. I< Optional. Type uniline.  > 

=head2 CacheDirectoryMode

Specifies the access mode of the directories specified in C<RuntimeDirectory>,
C<StateDirectory>, C<CacheDirectory>, C<LogsDirectory>, or
C<ConfigurationDirectory>, respectively, as an octal number.  Defaults to
C<0755>. See "Permissions" in L<path_resolution(7)> for a
discussion of the meaning of permission bits. I< Optional. Type uniline.  > 

=head2 LogsDirectoryMode

Specifies the access mode of the directories specified in C<RuntimeDirectory>,
C<StateDirectory>, C<CacheDirectory>, C<LogsDirectory>, or
C<ConfigurationDirectory>, respectively, as an octal number.  Defaults to
C<0755>. See "Permissions" in L<path_resolution(7)> for a
discussion of the meaning of permission bits. I< Optional. Type uniline.  > 

=head2 ConfigurationDirectoryMode

Specifies the access mode of the directories specified in C<RuntimeDirectory>,
C<StateDirectory>, C<CacheDirectory>, C<LogsDirectory>, or
C<ConfigurationDirectory>, respectively, as an octal number.  Defaults to
C<0755>. See "Permissions" in L<path_resolution(7)> for a
discussion of the meaning of permission bits. I< Optional. Type uniline.  > 

=head2 RuntimeDirectoryPreserve

Takes a boolean argument or C<restart>.  If set to C<no> (the
default), the directories specified in C<RuntimeDirectory> are always removed when the service
stops. If set to C<restart> the directories are preserved when the service is both automatically
and manually restarted. Here, the automatic restart means the operation specified in
C<Restart>, and manual restart means the one triggered by systemctl restart
foo.service. If set to C<yes>, then the directories are not removed when the service is
stopped. Note that since the runtime directory /run is a mount point of
C<tmpfs>, then for system services the directories specified in
C<RuntimeDirectory> are removed when the system is rebooted. I< Optional. Type enum. choice: 'no', 'yes', 'restart'.  > 

=head2 ReadWritePaths

Sets up a new file system namespace for executed processes. These options may be used to limit
access a process might have to the file system hierarchy. Each setting takes a space-separated list of paths
relative to the host's root directory (i.e. the system running the service manager).  Note that if paths
contain symlinks, they are resolved relative to the root directory set with
C<RootDirectory>/C<RootImage>.

Paths listed in C<ReadWritePaths> are accessible from within the namespace with the same
access modes as from outside of it. Paths listed in C<ReadOnlyPaths> are accessible for
reading only, writing will be refused even if the usual file access controls would permit this. Nest
C<ReadWritePaths> inside of C<ReadOnlyPaths> in order to provide writable
subdirectories within read-only directories. Use C<ReadWritePaths> in order to whitelist
specific paths for write access if C<ProtectSystem=strict> is used.

Paths listed in C<InaccessiblePaths> will be made inaccessible for processes inside
the namespace along with everything below them in the file system hierarchy. This may be more restrictive than
desired, because it is not possible to nest C<ReadWritePaths>, C<ReadOnlyPaths>,
C<BindPaths>, or C<BindReadOnlyPaths> inside it. For a more flexible option,
see C<TemporaryFileSystem>.

Non-directory paths may be specified as well. These options may be specified more than once,
in which case all paths listed will have limited access from within the namespace. If the empty string is
assigned to this option, the specific list is reset, and all prior assignments have no effect.

Paths in C<ReadWritePaths>, C<ReadOnlyPaths> and
C<InaccessiblePaths> may be prefixed with C<->, in which case they will be
ignored when they do not exist. If prefixed with C<+> the paths are taken relative to the root
directory of the unit, as configured with C<RootDirectory>/C<RootImage>,
instead of relative to the root directory of the host (see above). When combining C<-> and
C<+> on the same path make sure to specify C<-> first, and C<+>
second.

Note that these settings will disconnect propagation of mounts from the unit's processes to the
host. This means that this setting may not be used for services which shall be able to install mount points in
the main mount namespace. For C<ReadWritePaths> and C<ReadOnlyPaths>
propagation in the other direction is not affected, i.e. mounts created on the host generally appear in the
unit processes' namespace, and mounts removed on the host also disappear there too. In particular, note that
mount propagation from host to unit will result in unmodified mounts to be created in the unit's namespace,
i.e. writable mounts appearing on the host will be writable in the unit's namespace too, even when propagated
below a path marked with C<ReadOnlyPaths>! Restricting access with these options hence does
not extend to submounts of a directory that are created later on. This means the lock-down offered by that
setting is not complete, and does not offer full protection. 

Note that the effect of these settings may be undone by privileged processes. In order to set up an
effective sandboxed environment for a unit it is thus recommended to combine these settings with either
C<CapabilityBoundingSet=~CAP_SYS_ADMIN> or
C<SystemCallFilter=~@mount>. I< Optional. Type list of uniline.  > 

=head2 ReadOnlyPaths

Sets up a new file system namespace for executed processes. These options may be used to limit
access a process might have to the file system hierarchy. Each setting takes a space-separated list of paths
relative to the host's root directory (i.e. the system running the service manager).  Note that if paths
contain symlinks, they are resolved relative to the root directory set with
C<RootDirectory>/C<RootImage>.

Paths listed in C<ReadWritePaths> are accessible from within the namespace with the same
access modes as from outside of it. Paths listed in C<ReadOnlyPaths> are accessible for
reading only, writing will be refused even if the usual file access controls would permit this. Nest
C<ReadWritePaths> inside of C<ReadOnlyPaths> in order to provide writable
subdirectories within read-only directories. Use C<ReadWritePaths> in order to whitelist
specific paths for write access if C<ProtectSystem=strict> is used.

Paths listed in C<InaccessiblePaths> will be made inaccessible for processes inside
the namespace along with everything below them in the file system hierarchy. This may be more restrictive than
desired, because it is not possible to nest C<ReadWritePaths>, C<ReadOnlyPaths>,
C<BindPaths>, or C<BindReadOnlyPaths> inside it. For a more flexible option,
see C<TemporaryFileSystem>.

Non-directory paths may be specified as well. These options may be specified more than once,
in which case all paths listed will have limited access from within the namespace. If the empty string is
assigned to this option, the specific list is reset, and all prior assignments have no effect.

Paths in C<ReadWritePaths>, C<ReadOnlyPaths> and
C<InaccessiblePaths> may be prefixed with C<->, in which case they will be
ignored when they do not exist. If prefixed with C<+> the paths are taken relative to the root
directory of the unit, as configured with C<RootDirectory>/C<RootImage>,
instead of relative to the root directory of the host (see above). When combining C<-> and
C<+> on the same path make sure to specify C<-> first, and C<+>
second.

Note that these settings will disconnect propagation of mounts from the unit's processes to the
host. This means that this setting may not be used for services which shall be able to install mount points in
the main mount namespace. For C<ReadWritePaths> and C<ReadOnlyPaths>
propagation in the other direction is not affected, i.e. mounts created on the host generally appear in the
unit processes' namespace, and mounts removed on the host also disappear there too. In particular, note that
mount propagation from host to unit will result in unmodified mounts to be created in the unit's namespace,
i.e. writable mounts appearing on the host will be writable in the unit's namespace too, even when propagated
below a path marked with C<ReadOnlyPaths>! Restricting access with these options hence does
not extend to submounts of a directory that are created later on. This means the lock-down offered by that
setting is not complete, and does not offer full protection. 

Note that the effect of these settings may be undone by privileged processes. In order to set up an
effective sandboxed environment for a unit it is thus recommended to combine these settings with either
C<CapabilityBoundingSet=~CAP_SYS_ADMIN> or
C<SystemCallFilter=~@mount>. I< Optional. Type list of uniline.  > 

=head2 InaccessiblePaths

Sets up a new file system namespace for executed processes. These options may be used to limit
access a process might have to the file system hierarchy. Each setting takes a space-separated list of paths
relative to the host's root directory (i.e. the system running the service manager).  Note that if paths
contain symlinks, they are resolved relative to the root directory set with
C<RootDirectory>/C<RootImage>.

Paths listed in C<ReadWritePaths> are accessible from within the namespace with the same
access modes as from outside of it. Paths listed in C<ReadOnlyPaths> are accessible for
reading only, writing will be refused even if the usual file access controls would permit this. Nest
C<ReadWritePaths> inside of C<ReadOnlyPaths> in order to provide writable
subdirectories within read-only directories. Use C<ReadWritePaths> in order to whitelist
specific paths for write access if C<ProtectSystem=strict> is used.

Paths listed in C<InaccessiblePaths> will be made inaccessible for processes inside
the namespace along with everything below them in the file system hierarchy. This may be more restrictive than
desired, because it is not possible to nest C<ReadWritePaths>, C<ReadOnlyPaths>,
C<BindPaths>, or C<BindReadOnlyPaths> inside it. For a more flexible option,
see C<TemporaryFileSystem>.

Non-directory paths may be specified as well. These options may be specified more than once,
in which case all paths listed will have limited access from within the namespace. If the empty string is
assigned to this option, the specific list is reset, and all prior assignments have no effect.

Paths in C<ReadWritePaths>, C<ReadOnlyPaths> and
C<InaccessiblePaths> may be prefixed with C<->, in which case they will be
ignored when they do not exist. If prefixed with C<+> the paths are taken relative to the root
directory of the unit, as configured with C<RootDirectory>/C<RootImage>,
instead of relative to the root directory of the host (see above). When combining C<-> and
C<+> on the same path make sure to specify C<-> first, and C<+>
second.

Note that these settings will disconnect propagation of mounts from the unit's processes to the
host. This means that this setting may not be used for services which shall be able to install mount points in
the main mount namespace. For C<ReadWritePaths> and C<ReadOnlyPaths>
propagation in the other direction is not affected, i.e. mounts created on the host generally appear in the
unit processes' namespace, and mounts removed on the host also disappear there too. In particular, note that
mount propagation from host to unit will result in unmodified mounts to be created in the unit's namespace,
i.e. writable mounts appearing on the host will be writable in the unit's namespace too, even when propagated
below a path marked with C<ReadOnlyPaths>! Restricting access with these options hence does
not extend to submounts of a directory that are created later on. This means the lock-down offered by that
setting is not complete, and does not offer full protection. 

Note that the effect of these settings may be undone by privileged processes. In order to set up an
effective sandboxed environment for a unit it is thus recommended to combine these settings with either
C<CapabilityBoundingSet=~CAP_SYS_ADMIN> or
C<SystemCallFilter=~@mount>. I< Optional. Type list of uniline.  > 

=head2 TemporaryFileSystem

Takes a space-separated list of mount points for temporary file systems (tmpfs). If set, a new file
system namespace is set up for executed processes, and a temporary file system is mounted on each mount point.
This option may be specified more than once, in which case temporary file systems are mounted on all listed mount
points. If the empty string is assigned to this option, the list is reset, and all prior assignments have no effect.
Each mount point may optionally be suffixed with a colon (C<:>) and mount options such as
C<size=10%> or C<ro>. By default, each temporary file system is mounted
with C<nodev,strictatime,mode=0755>. These can be disabled by explicitly specifying the corresponding
mount options, e.g., C<dev> or C<nostrictatime>.

This is useful to hide files or directories not relevant to the processes invoked by the unit, while necessary
files or directories can be still accessed by combining with C<BindPaths> or
C<BindReadOnlyPaths>. See the example below.

Example: if a unit has the following,

    TemporaryFileSystem=/var:ro
    BindReadOnlyPaths=/var/lib/systemd

then the invoked processes by the unit cannot see any files or directories under /var except for
/var/lib/systemd or its contents. I< Optional. Type list of uniline.  > 

=head2 PrivateTmp

Takes a boolean argument. If true, sets up a new file system namespace for the executed
processes and mounts private /tmp and /var/tmp directories inside it
that is not shared by processes outside of the namespace. This is useful to secure access to temporary files of
the process, but makes sharing between processes via /tmp or /var/tmp
impossible. If this is enabled, all temporary files created by a service in these directories will be removed
after the service is stopped.  Defaults to false. It is possible to run two or more units within the same
private /tmp and /var/tmp namespace by using the
C<JoinsNamespaceOf> directive, see
L<systemd.unit(5)> for
details. This setting is implied if C<DynamicUser> is set. For this setting the same
restrictions regarding mount propagation and privileges apply as for C<ReadOnlyPaths> and
related calls, see above. Enabling this setting has the side effect of adding C<Requires> and
C<After> dependencies on all mount units necessary to access /tmp and
/var/tmp. Moreover an implicitly C<After> ordering on
L<systemd-tmpfiles-setup.service(8)>
is added.

Note that the implementation of this setting might be impossible (for example if mount namespaces are not
available), and the unit should be written in a way that does not solely rely on this setting for
security. I< Optional. Type boolean.  > 

=head2 PrivateDevices

Takes a boolean argument. If true, sets up a new /dev mount for the
executed processes and only adds API pseudo devices such as /dev/null,
/dev/zero or /dev/random (as well as the pseudo TTY subsystem) to it,
but no physical devices such as /dev/sda, system memory /dev/mem,
system ports /dev/port and others. This is useful to securely turn off physical device
access by the executed process. Defaults to false. Enabling this option will install a system call filter to
block low-level I/O system calls that are grouped in the C<@raw-io> set, will also remove
C<CAP_MKNOD> and C<CAP_SYS_RAWIO> from the capability bounding set for the
unit (see above), and set C<DevicePolicy=closed> (see
L<systemd.resource-control(5)>
for details). Note that using this setting will disconnect propagation of mounts from the service to the host
(propagation in the opposite direction continues to work).  This means that this setting may not be used for
services which shall be able to install mount points in the main mount namespace. The new
/dev will be mounted read-only and 'noexec'. The latter may break old programs which try
to set up executable memory by using
L<mmap(2)> of
/dev/zero instead of using C<MAP_ANON>. For this setting the same
restrictions regarding mount propagation and privileges apply as for C<ReadOnlyPaths> and
related calls, see above.  If turned on and if running in user mode, or in system mode, but without the
C<CAP_SYS_ADMIN> capability (e.g. setting C<User>),
C<NoNewPrivileges=yes> is implied.

Note that the implementation of this setting might be impossible (for example if mount namespaces are not
available), and the unit should be written in a way that does not solely rely on this setting for
security. I< Optional. Type boolean.  > 

=head2 PrivateNetwork

Takes a boolean argument. If true, sets up a new network namespace for the executed processes
and configures only the loopback network device C<lo> inside it. No other network devices will
be available to the executed process. This is useful to turn off network access by the executed process.
Defaults to false. It is possible to run two or more units within the same private network namespace by using
the C<JoinsNamespaceOf> directive, see
L<systemd.unit(5)> for
details. Note that this option will disconnect all socket families from the host, including
C<AF_NETLINK> and C<AF_UNIX>. Effectively, for
C<AF_NETLINK> this means that device configuration events received from
L<systemd-udevd.service(8)> are
not delivered to the unit's processes. And for C<AF_UNIX> this has the effect that
C<AF_UNIX> sockets in the abstract socket namespace of the host will become unavailable to
the unit's processes (however, those located in the file system will continue to be accessible).

Note that the implementation of this setting might be impossible (for example if network namespaces are
not available), and the unit should be written in a way that does not solely rely on this setting for
security. I< Optional. Type boolean.  > 

=head2 PrivateUsers

Takes a boolean argument. If true, sets up a new user namespace for the executed processes and
configures a minimal user and group mapping, that maps the C<root> user and group as well as
the unit's own user and group to themselves and everything else to the C<nobody> user and
group. This is useful to securely detach the user and group databases used by the unit from the rest of the
system, and thus to create an effective sandbox environment. All files, directories, processes, IPC objects and
other resources owned by users/groups not equaling C<root> or the unit's own will stay visible
from within the unit but appear owned by the C<nobody> user and group. If this mode is enabled,
all unit processes are run without privileges in the host user namespace (regardless if the unit's own
user/group is C<root> or not). Specifically this means that the process will have zero process
capabilities on the host's user namespace, but full capabilities within the service's user namespace. Settings
such as C<CapabilityBoundingSet> will affect only the latter, and there's no way to acquire
additional capabilities in the host's user namespace. Defaults to off.

This setting is particularly useful in conjunction with
C<RootDirectory>/C<RootImage>, as the need to synchronize the user and group
databases in the root directory and on the host is reduced, as the only users and groups who need to be matched
are C<root>, C<nobody> and the unit's own user and group.

Note that the implementation of this setting might be impossible (for example if user namespaces are not
available), and the unit should be written in a way that does not solely rely on this setting for
security. I< Optional. Type boolean.  > 

=head2 ProtectKernelTunables

Takes a boolean argument. If true, kernel variables accessible through
/proc/sys, /sys, /proc/sysrq-trigger,
/proc/latency_stats, /proc/acpi,
/proc/timer_stats, /proc/fs and /proc/irq will
be made read-only to all processes of the unit. Usually, tunable kernel variables should be initialized only at
boot-time, for example with the
L<sysctl.d(5)> mechanism. Few
services need to write to these at runtime; it is hence recommended to turn this on for most services. For this
setting the same restrictions regarding mount propagation and privileges apply as for
C<ReadOnlyPaths> and related calls, see above. Defaults to off.  If turned on and if running
in user mode, or in system mode, but without the C<CAP_SYS_ADMIN> capability (e.g.  services
for which C<User> is set), C<NoNewPrivileges=yes> is implied. Note that this
option does not prevent indirect changes to kernel tunables effected by IPC calls to other processes. However,
C<InaccessiblePaths> may be used to make relevant IPC file system objects inaccessible. If
C<ProtectKernelTunables> is set, C<MountAPIVFS=yes> is
implied. I< Optional. Type boolean.  > 

=head2 ProtectKernelModules

Takes a boolean argument. If true, explicit module loading will be denied. This allows
module load and unload operations to be turned off on modular kernels. It is recommended to turn this on for most services
that do not need special file systems or extra kernel modules to work. Defaults to off. Enabling this option
removes C<CAP_SYS_MODULE> from the capability bounding set for the unit, and installs a
system call filter to block module system calls, also /usr/lib/modules is made
inaccessible. For this setting the same restrictions regarding mount propagation and privileges apply as for
C<ReadOnlyPaths> and related calls, see above.  Note that limited automatic module loading due
to user configuration or kernel mapping tables might still happen as side effect of requested user operations,
both privileged and unprivileged. To disable module auto-load feature please see
L<sysctl.d(5)>C<kernel.modules_disabled> mechanism and
/proc/sys/kernel/modules_disabled documentation.  If turned on and if running in user
mode, or in system mode, but without the C<CAP_SYS_ADMIN> capability (e.g. setting
C<User>), C<NoNewPrivileges=yes> is implied. I< Optional. Type boolean.  > 

=head2 ProtectControlGroups

Takes a boolean argument. If true, the Linux Control Groups (L<cgroups(7)>) hierarchies
accessible through /sys/fs/cgroup will be made read-only to all processes of the
unit. Except for container managers no services should require write access to the control groups hierarchies;
it is hence recommended to turn this on for most services. For this setting the same restrictions regarding
mount propagation and privileges apply as for C<ReadOnlyPaths> and related calls, see
above. Defaults to off. If C<ProtectControlGroups> is set, C<MountAPIVFS=yes>
is implied. I< Optional. Type boolean.  > 

=head2 RestrictAddressFamilies

Restricts the set of socket address families accessible to the processes of this unit. Takes a
space-separated list of address family names to whitelist, such as C<AF_UNIX>,
C<AF_INET> or C<AF_INET6>. When prefixed with C<~> the
listed address families will be applied as blacklist, otherwise as whitelist.  Note that this restricts access
to the L<socket(2)> system call
only. Sockets passed into the process by other means (for example, by using socket activation with socket
units, see L<systemd.socket(5)>)
are unaffected. Also, sockets created with socketpair() (which creates connected AF_UNIX
sockets only) are unaffected. Note that this option has no effect on 32-bit x86, s390, s390x, mips, mips-le,
ppc, ppc-le, pcc64, ppc64-le and is ignored (but works correctly on other ABIs, including x86-64). Note that on
systems supporting multiple ABIs (such as x86/x86-64) it is recommended to turn off alternative ABIs for
services, so that they cannot be used to circumvent the restrictions of this option. Specifically, it is
recommended to combine this option with C<SystemCallArchitectures=native> or similar. If
running in user mode, or in system mode, but without the C<CAP_SYS_ADMIN> capability
(e.g. setting C<User=nobody>), C<NoNewPrivileges=yes> is implied. By default,
no restrictions apply, all address families are accessible to processes. If assigned the empty string, any
previous address familiy restriction changes are undone. This setting does not affect commands prefixed with
C<+>.

Use this option to limit exposure of processes to remote access, in particular via exotic and sensitive
network protocols, such as C<AF_PACKET>. Note that in most cases, the local
C<AF_UNIX> address family should be included in the configured whitelist as it is frequently
used for local communication, including for
L<syslog(2)>
logging. I< Optional. Type uniline.  > 

=head2 RestrictNamespaces

Restricts access to Linux namespace functionality for the processes of this unit. For details
about Linux namespaces, see L<namespaces(7)>. Either
takes a boolean argument, or a space-separated list of namespace type identifiers. If false (the default), no
restrictions on namespace creation and switching are made. If true, access to any kind of namespacing is
prohibited. Otherwise, a space-separated list of namespace type identifiers must be specified, consisting of
any combination of: C<cgroup>, C<ipc>, C<net>,
C<mnt>, C<pid>, C<user> and C<uts>. Any
namespace type listed is made accessible to the unit's processes, access to namespace types not listed is
prohibited (whitelisting). By prepending the list with a single tilde character (C<~>) the
effect may be inverted: only the listed namespace types will be made inaccessible, all unlisted ones are
permitted (blacklisting). If the empty string is assigned, the default namespace restrictions are applied,
which is equivalent to false. This option may appear more than once, in which case the namespace types are
merged by C<OR>, or by C<AND> if the lines are prefixed with
C<~> (see examples below). Internally, this setting limits access to the
L<unshare(2)>,
L<clone(2)> and
L<setns(2)> system calls, taking
the specified flags parameters into account. Note that — if this option is used — in addition to restricting
creation and switching of the specified types of namespaces (or all of them, if true) access to the
setns() system call with a zero flags parameter is prohibited.  This setting is only
supported on x86, x86-64, mips, mips-le, mips64, mips64-le, mips64-n32, mips64-le-n32, ppc64, ppc64-le, s390
and s390x, and enforces no restrictions on other architectures. If running in user mode, or in system mode, but
without the C<CAP_SYS_ADMIN> capability (e.g. setting C<User>),
C<NoNewPrivileges=yes> is implied.

Example: if a unit has the following,

    RestrictNamespaces=cgroup ipc
    RestrictNamespaces=cgroup net

then C<cgroup>, C<ipc>, and C<net> are set.
If the second line is prefixed with C<~>, e.g.,

    RestrictNamespaces=cgroup ipc
    RestrictNamespaces=~cgroup net

then, only C<ipc> is set. I< Optional. Type uniline.  > 

=head2 LockPersonality

Takes a boolean argument. If set, locks down the L<personality(2)> system
call so that the kernel execution domain may not be changed from the default or the personality selected with
C<Personality> directive. This may be useful to improve security, because odd personality
emulations may be poorly tested and source of vulnerabilities. If running in user mode, or in system mode, but
without the C<CAP_SYS_ADMIN> capability (e.g. setting C<User>),
C<NoNewPrivileges=yes> is implied. I< Optional. Type boolean.  > 

=head2 MemoryDenyWriteExecute

Takes a boolean argument. If set, attempts to create memory mappings that are writable and
executable at the same time, or to change existing memory mappings to become executable, or mapping shared
memory segments as executable are prohibited.  Specifically, a system call filter is added that rejects
L<mmap(2)> system calls with both
C<PROT_EXEC> and C<PROT_WRITE> set,
L<mprotect(2)> or
L<pkey_mprotect(2)> system calls
with C<PROT_EXEC> set and
L<shmat(2)> system calls with
C<SHM_EXEC> set. Note that this option is incompatible with programs and libraries that
generate program code dynamically at runtime, including JIT execution engines, executable stacks, and code
"trampoline" feature of various C compilers. This option improves service security, as it makes harder for
software exploits to change running code dynamically. Note that this feature is fully available on x86-64, and
partially on x86. Specifically, the shmat() protection is not available on x86. Note that
on systems supporting multiple ABIs (such as x86/x86-64) it is recommended to turn off alternative ABIs for
services, so that they cannot be used to circumvent the restrictions of this option. Specifically, it is
recommended to combine this option with C<SystemCallArchitectures=native> or similar. If
running in user mode, or in system mode, but without the C<CAP_SYS_ADMIN> capability
(e.g. setting C<User>), C<NoNewPrivileges=yes> is implied. I< Optional. Type boolean.  > 

=head2 RestrictRealtime

Takes a boolean argument. If set, any attempts to enable realtime scheduling in a process of
the unit are refused. This restricts access to realtime task scheduling policies such as
C<SCHED_FIFO>, C<SCHED_RR> or C<SCHED_DEADLINE>. See
L<sched(7)>
for details about these scheduling policies. If running in user mode, or in system mode, but without the
C<CAP_SYS_ADMIN> capability (e.g. setting C<User>),
C<NoNewPrivileges=yes> is implied. Realtime scheduling policies may be used to monopolize CPU
time for longer periods of time, and may hence be used to lock up or otherwise trigger Denial-of-Service
situations on the system. It is hence recommended to restrict access to realtime scheduling to the few programs
that actually require them. Defaults to off. I< Optional. Type boolean.  > 

=head2 RemoveIPC

Takes a boolean parameter. If set, all System V and POSIX IPC objects owned by the user and
group the processes of this unit are run as are removed when the unit is stopped. This setting only has an
effect if at least one of C<User>, C<Group> and
C<DynamicUser> are used. It has no effect on IPC objects owned by the root user. Specifically,
this removes System V semaphores, as well as System V and POSIX shared memory segments and message queues. If
multiple units use the same user or group the IPC objects are removed when the last of these units is
stopped. This setting is implied if C<DynamicUser> is set. I< Optional. Type boolean.  > 

=head2 PrivateMounts

Takes a boolean parameter. If set, the processes of this unit will be run in their own private
file system (mount) namespace with all mount propagation from the processes towards the host's main file system
namespace turned off. This means any file system mount points established or removed by the unit's processes
will be private to them and not be visible to the host. However, file system mount points established or
removed on the host will be propagated to the unit's processes. See L<mount_namespaces(7)> for
details on file system namespaces. Defaults to off.

When turned on, this executes three operations for each invoked process: a new
C<CLONE_NEWNS> namespace is created, after which all existing mounts are remounted to
C<MS_SLAVE> to disable propagation from the unit's processes to the host (but leaving
propagation in the opposite direction in effect). Finally, the mounts are remounted again to the propagation
mode configured with C<MountFlags>, see below.

File system namespaces are set up individually for each process forked off by the service manager. Mounts
established in the namespace of the process created by C<ExecStartPre> will hence be cleaned
up automatically as soon as that process exits and will not be available to subsequent processes forked off for
C<ExecStart> (and similar applies to the various other commands configured for
units). Similarly, C<JoinsNamespaceOf> does not permit sharing kernel mount namespaces between
units, it only enables sharing of the /tmp/ and /var/tmp/
directories.

Other file system namespace unit settings — C<PrivateMounts>,
C<PrivateTmp>, C<PrivateDevices>, C<ProtectSystem>,
C<ProtectHome>, C<ReadOnlyPaths>, C<InaccessiblePaths>,
C<ReadWritePaths>, … — also enable file system namespacing in a fashion equivalent to this
option. Hence it is primarily useful to explicitly request this behaviour if none of the other settings are
used. I< Optional. Type boolean.  > 

=head2 MountFlags

Takes a mount propagation setting: C<shared>, C<slave> or
C<private>, which controls whether file system mount points in the file system namespaces set up
for this unit's processes will receive or propagate mounts and unmounts from other file system namespaces. See
L<mount(2)>
for details on mount propagation, and the three propagation flags in particular.

This setting only controls the final propagation setting in effect on all mount
points of the file system namespace created for each process of this unit. Other file system namespacing unit
settings (see the discussion in C<PrivateMounts> above) will implicitly disable mount and
unmount propagation from the unit's processes towards the host by changing the propagation setting of all mount
points in the unit's file system namepace to C<slave> first. Setting this option to
C<shared> does not reestablish propagation in that case.

If not set – but file system namespaces are enabled through another file system namespace unit setting –
C<shared> mount propagation is used, but — as mentioned — as C<slave> is applied
first, propagation from the unit's processes to the host is still turned off.

It is not recommended to to use C<private> mount propagation for units, as this means
temporary mounts (such as removable media) of the host will stay mounted and thus indefinitely busy in forked
off processes, as unmount propagation events won't be received by the file system namespace of the unit.

Usually, it is best to leave this setting unmodified, and use higher level file system namespacing
options instead, in particular C<PrivateMounts>, see above. I< Optional. Type uniline.  > 

=head2 SystemCallFilter

Takes a space-separated list of system call names. If this setting is used, all system calls
executed by the unit processes except for the listed ones will result in immediate process termination with the
C<SIGSYS> signal (whitelisting). If the first character of the list is C<~>,
the effect is inverted: only the listed system calls will result in immediate process termination
(blacklisting). Blacklisted system calls and system call groups may optionally be suffixed with a colon
(C<:>) and C<errno> error number (between 0 and 4095) or errno name such as
C<EPERM>, C<EACCES> or C<EUCLEAN>. This value will be
returned when a blacklisted system call is triggered, instead of terminating the processes immediately.  This
value takes precedence over the one given in C<SystemCallErrorNumber>.  If running in user
mode, or in system mode, but without the C<CAP_SYS_ADMIN> capability (e.g. setting
C<User=nobody>), C<NoNewPrivileges=yes> is implied. This feature makes use of
the Secure Computing Mode 2 interfaces of the kernel ('seccomp filtering') and is useful for enforcing a
minimal sandboxing environment. Note that the execve, exit,
exit_group, getrlimit, rt_sigreturn,
sigreturn system calls and the system calls for querying time and sleeping are implicitly
whitelisted and do not need to be listed explicitly. This option may be specified more than once, in which case
the filter masks are merged. If the empty string is assigned, the filter is reset, all prior assignments will
have no effect. This does not affect commands prefixed with C<+>.

Note that on systems supporting multiple ABIs (such as x86/x86-64) it is recommended to turn off
alternative ABIs for services, so that they cannot be used to circumvent the restrictions of this
option. Specifically, it is recommended to combine this option with
C<SystemCallArchitectures=native> or similar.

Note that strict system call filters may impact execution and error handling code paths of the service
invocation. Specifically, access to the execve system call is required for the execution
of the service binary — if it is blocked service invocation will necessarily fail. Also, if execution of the
service binary fails for some reason (for example: missing service executable), the error handling logic might
require access to an additional set of system calls in order to process and log this failure correctly. It
might be necessary to temporarily disable system call filters in order to simplify debugging of such
failures.

If you specify both types of this option (i.e.  whitelisting and blacklisting), the first encountered
will take precedence and will dictate the default action (termination or approval of a system call). Then the
next occurrences of this option will add or delete the listed system calls from the set of the filtered system
calls, depending of its type and the default action. (For example, if you have started with a whitelisting of
read and write, and right after it add a blacklisting of
write, then write will be removed from the set.)

As the number of possible system calls is large, predefined sets of system calls are provided.  A set
starts with C<@> character, followed by name of the set.
Currently predefined system call setsSetDescription@aioAsynchronous I/O (L<io_setup(2)>, L<io_submit(2)>, and related calls)@basic-ioSystem calls for basic I/O: reading, writing, seeking, file descriptor duplication and closing (L<read(2)>, L<write(2)>, and related calls)@chownChanging file ownership (L<chown(2)>, L<fchownat(2)>, and related calls)@clockSystem calls for changing the system clock (L<adjtimex(2)>, L<settimeofday(2)>, and related calls)@cpu-emulationSystem calls for CPU emulation functionality (L<vm86(2)> and related calls)@debugDebugging, performance monitoring and tracing functionality (L<ptrace(2)>, L<perf_event_open(2)> and related calls)@file-systemFile system operations: opening, creating files and directories for read and write, renaming and removing them, reading file properties, or creating hard and symbolic links.@io-eventEvent loop system calls (L<poll(2)>, L<select(2)>, L<epoll(7)>, L<eventfd(2)> and related calls)@ipcPipes, SysV IPC, POSIX Message Queues and other IPC (L<mq_overview(7)>, L<svipc(7)>)@keyringKernel keyring access (L<keyctl(2)> and related calls)@memlockLocking of memory into RAM (L<mlock(2)>, L<mlockall(2)> and related calls)@moduleLoading and unloading of kernel modules (L<init_module(2)>, L<delete_module(2)> and related calls)@mountMounting and unmounting of file systems (L<mount(2)>, L<chroot(2)>, and related calls)@network-ioSocket I/O (including local AF_UNIX): L<socket(7)>, L<unix(7)>@obsoleteUnusual, obsolete or unimplemented (L<create_module(2)>, L<gtty(2)>, …)@privilegedAll system calls which need super-user capabilities (L<capabilities(7)>)@processProcess control, execution, namespaceing operations (L<clone(2)>, L<kill(2)>, L<namespaces(7)>, …@raw-ioRaw I/O port access (L<ioperm(2)>, L<iopl(2)>, pciconfig_read(), …)@rebootSystem calls for rebooting and reboot preparation (L<reboot(2)>, kexec(), …)@resourcesSystem calls for changing resource limits, memory and scheduling parameters (L<setrlimit(2)>, L<setpriority(2)>, …)@setuidSystem calls for changing user ID and group ID credentials, (L<setuid(2)>, L<setgid(2)>, L<setresuid(2)>, …)@signalSystem calls for manipulating and handling process signals (L<signal(2)>, L<sigprocmask(2)>, …)@swapSystem calls for enabling/disabling swap devices (L<swapon(2)>, L<swapoff(2)>)@syncSynchronizing files and memory to disk: (L<fsync(2)>, L<msync(2)>, and related calls)@system-serviceA reasonable set of system calls used by common system services, excluding any special purpose calls. This is the recommended starting point for whitelisting system calls for system services, as it contains what is typically needed by system services, but excludes overly specific interfaces. For example, the following APIs are excluded: C<@clock>, C<@mount>, C<@swap>, C<@reboot>.@timerSystem calls for scheduling operations by time (L<alarm(2)>, L<timer_create(2)>, …)
Note, that as new system calls are added to the kernel, additional system calls might be added to the groups
above. Contents of the sets may also change between systemd versions. In addition, the list of system calls
depends on the kernel version and architecture for which systemd was compiled. Use
systemd-analyze syscall-filter to list the actual list of system calls in each
filter.

Generally, whitelisting system calls (rather than blacklisting) is the safer mode of operation. It is
recommended to enforce system call whitelists for all long-running system services. Specifically, the
following lines are a relatively safe basic choice for the majority of system services:

It is recommended to combine the file system namespacing related options with
C<SystemCallFilter=~@mount>, in order to prohibit the unit's processes to undo the
mappings. Specifically these are the options C<PrivateTmp>,
C<PrivateDevices>, C<ProtectSystem>, C<ProtectHome>,
C<ProtectKernelTunables>, C<ProtectControlGroups>,
C<ReadOnlyPaths>, C<InaccessiblePaths> and
C<ReadWritePaths>. I< Optional. Type list of uniline.  > 

=head2 SystemCallErrorNumber

Takes an C<errno> error number (between 1 and 4095) or errno name such as
C<EPERM>, C<EACCES> or C<EUCLEAN>, to return when the
system call filter configured with C<SystemCallFilter> is triggered, instead of terminating
the process immediately. When this setting is not used, or when the empty string is assigned, the process will
be terminated immediately when the filter is triggered. I< Optional. Type uniline.  > 

=head2 SystemCallArchitectures

Takes a space-separated list of architecture identifiers to include in the system call
filter. The known architecture identifiers are the same as for C<ConditionArchitecture>
described in L<systemd.unit(5)>,
as well as C<x32>, C<mips64-n32>, C<mips64-le-n32>, and
the special identifier C<native>.  The special identifier C<native>
implicitly maps to the native architecture of the system (or more precisely: to the architecture the system
manager is compiled for). If running in user mode, or in system mode, but without the
C<CAP_SYS_ADMIN> capability (e.g. setting C<User=nobody>),
C<NoNewPrivileges=yes> is implied. By default, this option is set to the empty list, i.e. no
system call architecture filtering is applied.

If this setting is used, processes of this unit will only be permitted to call native system calls, and
system calls of the specified architectures. For the purposes of this option, the x32 architecture is treated
as including x86-64 system calls. However, this setting still fulfills its purpose, as explained below, on
x32.

System call filtering is not equally effective on all architectures. For example, on x86
filtering of network socket-related calls is not possible, due to ABI limitations — a limitation that x86-64
does not have, however. On systems supporting multiple ABIs at the same time — such as x86/x86-64 — it is hence
recommended to limit the set of permitted system call architectures so that secondary ABIs may not be used to
circumvent the restrictions applied to the native ABI of the system. In particular, setting
C<SystemCallArchitectures=native> is a good choice for disabling non-native ABIs.

System call architectures may also be restricted system-wide via the
C<SystemCallArchitectures> option in the global configuration. See
L<systemd-system.conf(5)> for
details. I< Optional. Type uniline.  > 

=head2 Environment

Sets environment variables for executed processes. Takes a space-separated list of variable
assignments. This option may be specified more than once, in which case all listed variables will be set. If
the same variable is set twice, the later setting will override the earlier setting. If the empty string is
assigned to this option, the list of environment variables is reset, all prior assignments have no
effect. Variable expansion is not performed inside the strings, however, specifier expansion is possible. The $
character has no special meaning. If you need to assign a value containing spaces or the equals sign to a
variable, use double quotes (") for the assignment.

Example:

    Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"

gives three variables C<VAR1>,
C<VAR2>, C<VAR3>
with the values C<word1 word2>,
C<word3>, C<$word 5 6>.

See L<environ(7)> for details
about environment variables.

Note that environment variables are not suitable for passing secrets (such as passwords, key material, …)
to service processes. Environment variables set for a unit are exposed to unprivileged clients via D-Bus IPC,
and generally not understood as being data that requires protection. Moreover, environment variables are
propagated down the process tree, including across security boundaries (such as setuid/setgid executables), and
hence might leak to processes that should not have access to the secret data. I< Optional. Type list of uniline.  > 

=head2 EnvironmentFile

Similar to C<Environment> but reads the environment variables from a text
file. The text file should contain new-line-separated variable assignments.  Empty lines, lines without an
C<=> separator, or lines starting with ; or # will be ignored, which may be used for
commenting. A line ending with a backslash will be concatenated with the following one, allowing multiline
variable definitions. The parser strips leading and trailing whitespace from the values of assignments, unless
you use double quotes (").

The argument passed should be an absolute filename or wildcard expression, optionally prefixed with
C<->, which indicates that if the file does not exist, it will not be read and no error or
warning message is logged. This option may be specified more than once in which case all specified files are
read. If the empty string is assigned to this option, the list of file to read is reset, all prior assignments
have no effect.

The files listed with this directive will be read shortly before the process is executed (more
specifically, after all processes from a previous unit state terminated.  This means you can generate these
files in one unit state, and read it with this option in the next).

Settings from these files override settings made with C<Environment>. If the same
variable is set twice from these files, the files will be read in the order they are specified and the later
setting will override the earlier setting. I< Optional. Type list of uniline.  > 

=head2 PassEnvironment

Pass environment variables set for the system service manager to executed processes. Takes a
space-separated list of variable names. This option may be specified more than once, in which case all listed
variables will be passed. If the empty string is assigned to this option, the list of environment variables to
pass is reset, all prior assignments have no effect. Variables specified that are not set for the system
manager will not be passed and will be silently ignored. Note that this option is only relevant for the system
service manager, as system services by default do not automatically inherit any environment variables set for
the service manager itself. However, in case of the user service manager all environment variables are passed
to the executed processes anyway, hence this option is without effect for the user service manager.

Variables set for invoked processes due to this setting are subject to being overridden by those
configured with C<Environment> or C<EnvironmentFile>.

Example:

    PassEnvironment=VAR1 VAR2 VAR3

passes three variables C<VAR1>,
C<VAR2>, C<VAR3>
with the values set for those variables in PID1.

See L<environ(7)> for details
about environment variables. I< Optional. Type list of uniline.  > 

=head2 UnsetEnvironment

Explicitly unset environment variable assignments that would normally be passed from the
service manager to invoked processes of this unit. Takes a space-separated list of variable names or variable
assignments. This option may be specified more than once, in which case all listed variables/assignments will
be unset. If the empty string is assigned to this option, the list of environment variables/assignments to
unset is reset. If a variable assignment is specified (that is: a variable name, followed by
C<=>, followed by its value), then any environment variable matching this precise assignment is
removed. If a variable name is specified (that is a variable name without any following C<=> or
value), then any assignment matching the variable name, regardless of its value is removed. Note that the
effect of C<UnsetEnvironment> is applied as final step when the environment list passed to
executed processes is compiled. That means it may undo assignments from any configuration source, including
assignments made through C<Environment> or C<EnvironmentFile>, inherited from
the system manager's global set of environment variables, inherited via C<PassEnvironment>,
set by the service manager itself (such as C<$NOTIFY_SOCKET> and such), or set by a PAM module
(in case C<PAMName> is used).

See L<environ(7)> for details
about environment variables. I< Optional. Type list of uniline.  > 

=head2 StandardInput

Controls where file descriptor 0 (STDIN) of the executed processes is connected to. Takes one
of C<null>, C<tty>, C<tty-force>, C<tty-fail>,
C<data>, C<file:path>, C<socket> or
C<fd:name>.

If C<null> is selected, standard input will be connected to /dev/null,
i.e. all read attempts by the process will result in immediate EOF.

If C<tty> is selected, standard input is connected to a TTY (as configured by
C<TTYPath>, see below) and the executed process becomes the controlling process of the
terminal. If the terminal is already being controlled by another process, the executed process waits until the
current controlling process releases the terminal.

C<tty-force> is similar to C<tty>, but the executed process is forcefully and
immediately made the controlling process of the terminal, potentially removing previous controlling processes
from the terminal.

C<tty-fail> is similar to C<tty>, but if the terminal already has a
controlling process start-up of the executed process fails.

The C<data> option may be used to configure arbitrary textual or binary data to pass via
standard input to the executed process. The data to pass is configured via
C<StandardInputText>/C<StandardInputData> (see below). Note that the actual
file descriptor type passed (memory file, regular file, UNIX pipe, …) might depend on the kernel and available
privileges. In any case, the file descriptor is read-only, and when read returns the specified data followed by
EOF.

The C<file:path> option may be used to connect a specific file
system object to standard input. An absolute path following the C<:> character is expected,
which may refer to a regular file, a FIFO or special file. If an C<AF_UNIX> socket in the
file system is specified, a stream socket is connected to it. The latter is useful for connecting standard
input of processes to arbitrary system services.

The C<socket> option is valid in socket-activated services only, and requires the relevant
socket unit file (see
L<systemd.socket(5)> for details)
to have C<Accept=yes> set, or to specify a single socket only. If this option is set, standard
input will be connected to the socket the service was activated from, which is primarily useful for
compatibility with daemons designed for use with the traditional L<inetd(8)> socket activation
daemon.

The C<fd:name> option connects standard input to a specific,
named file descriptor provided by a socket unit.  The name may be specified as part of this option, following a
C<:> character (e.g. C<fd:foobar>).  If no name is specified, the name
C<stdin> is implied (i.e. C<fd> is equivalent to C<fd:stdin>).
At least one socket unit defining the specified name must be provided via the C<Sockets>
option, and the file descriptor name may differ from the name of its containing socket unit.  If multiple
matches are found, the first one will be used.  See C<FileDescriptorName> in
L<systemd.socket(5)> for more
details about named file descriptors and their ordering.

This setting defaults to C<null>.

Note that services which specify C<DefaultDependencies=no> and use
C<StandardInput> or C<StandardOutput> with
C<tty>/C<tty-force>/C<tty-fail>, should specify
C<After=systemd-vconsole-setup.service>, to make sure that the tty intialization is
finished before they start. I< Optional. Type enum. choice: 'null', 'tty', 'tty-force', 'tty-fail', 'data', 'socket'.  > 

=head2 StandardOutput

Controls where file descriptor 1 (STDOUT) of the executed processes is connected to. Takes one
of C<inherit>, C<null>, C<tty>, C<journal>,
C<syslog>, C<kmsg>, C<journal+console>,
C<syslog+console>, C<kmsg+console>,
C<file:path>, C<append:path>,
C<socket> orC<fd:name>.

C<inherit> duplicates the file descriptor of standard input for standard output.

C<null> connects standard output to /dev/null, i.e. everything written
to it will be lost.

C<tty> connects standard output to a tty (as configured via C<TTYPath>,
see below). If the TTY is used for output only, the executed process will not become the controlling process of
the terminal, and will not fail or wait for other processes to release the terminal.

C<journal> connects standard output with the journal which is accessible via
L<journalctl(1)>.  Note that
everything that is written to syslog or kmsg (see below) is implicitly stored in the journal as well, the
specific two options listed below are hence supersets of this one.

C<syslog> connects standard output to the L<syslog(3)> system syslog
service, in addition to the journal. Note that the journal daemon is usually configured to forward everything
it receives to syslog anyway, in which case this option is no different from C<journal>.

C<kmsg> connects standard output with the kernel log buffer which is accessible via
L<dmesg(1)>,
in addition to the journal. The journal daemon might be configured to send all logs to kmsg anyway, in which
case this option is no different from C<journal>.

C<journal+console>, C<syslog+console> and C<kmsg+console> work
in a similar way as the three options above but copy the output to the system console as well.

The C<file:path> option may be used to connect a specific file
system object to standard output. The semantics are similar to the same option of
C<StandardInput>, see above. If path refers to a regular file
on the filesystem, it is opened (created if it doesn't exist yet) for writing at the beginning of the file,
but without truncating it.
If standard input and output are directed to the same file path, it is opened only once, for reading as well
as writing and duplicated. This is particularly useful when the specified path refers to an
C<AF_UNIX> socket in the file system, as in that case only a
single stream connection is created for both input and output.

C<append:path> is similar to C<file:path
> above, but it opens the file in append mode.

C<socket> connects standard output to a socket acquired via socket activation. The
semantics are similar to the same option of C<StandardInput>, see above.

The C<fd:name> option connects standard output to a specific,
named file descriptor provided by a socket unit.  A name may be specified as part of this option, following a
C<:> character (e.g. C<fd:foobar>).  If no name is specified, the name
C<stdout> is implied (i.e. C<fd> is equivalent to
C<fd:stdout>).  At least one socket unit defining the specified name must be provided via the
C<Sockets> option, and the file descriptor name may differ from the name of its containing
socket unit.  If multiple matches are found, the first one will be used.  See
C<FileDescriptorName> in
L<systemd.socket(5)> for more
details about named descriptors and their ordering.

If the standard output (or error output, see below) of a unit is connected to the journal, syslog or the
kernel log buffer, the unit will implicitly gain a dependency of type C<After> on
systemd-journald.socket (also see the "Implicit Dependencies" section above). Also note
that in this case stdout (or stderr, see below) will be an C<AF_UNIX> stream socket, and not
a pipe or FIFO that can be re-opened. This means when executing shell scripts the construct echo
"hello" > /dev/stderr for writing text to stderr will not work. To mitigate this use the construct
echo "hello" >&2 instead, which is mostly equivalent and avoids this pitfall.

This setting defaults to the value set with C<DefaultStandardOutput> in
L<systemd-system.conf(5)>, which
defaults to C<journal>. Note that setting this parameter might result in additional dependencies
to be added to the unit (see above). I< Optional. Type enum. choice: 'inherit', 'null', 'tty', 'journal', 'syslog', 'kmsg', 'journal+console', 'syslog+console', 'kmsg+console', 'socket'.  > 

=head2 StandardError

Controls where file descriptor 2 (STDERR) of the executed processes is connected to. The
available options are identical to those of C<StandardOutput>, with some exceptions: if set to
C<inherit> the file descriptor used for standard output is duplicated for standard error, while
C<fd:name> will use a default file descriptor name of
C<stderr>.

This setting defaults to the value set with C<DefaultStandardError> in
L<systemd-system.conf(5)>, which
defaults to C<inherit>. Note that setting this parameter might result in additional dependencies
to be added to the unit (see above). I< Optional. Type uniline.  > 

=head2 StandardInputText

Configures arbitrary textual or binary data to pass via file descriptor 0 (STDIN) to the
executed processes. These settings have no effect unless C<StandardInput> is set to
C<data>. Use this option to embed process input data directly in the unit file.

C<StandardInputText> accepts arbitrary textual data. C-style escapes for special
characters as well as the usual C<%>-specifiers are resolved. Each time this setting is used
the specified text is appended to the per-unit data buffer, followed by a newline character (thus every use
appends a new line to the end of the buffer). Note that leading and trailing whitespace of lines configured
with this option is removed. If an empty line is specified the buffer is cleared (hence, in order to insert an
empty line, add an additional C<\n> to the end or beginning of a line).

C<StandardInputData> accepts arbitrary binary data, encoded in Base64. No escape sequences or specifiers are
resolved. Any whitespace in the encoded version is ignored during decoding.

Note that C<StandardInputText> and C<StandardInputData> operate on the
same data buffer, and may be mixed in order to configure both binary and textual data for the same input
stream. The textual or binary data is joined strictly in the order the settings appear in the unit
file. Assigning an empty string to either will reset the data buffer.

Please keep in mind that in order to maintain readability long unit file settings may be split into
multiple lines, by suffixing each line (except for the last) with a C<\> character (see
L<systemd.unit(5)> for
details). This is particularly useful for large data configured with these two options. Example: I< Optional. Type uniline.  > 

=head2 StandardInputData

Configures arbitrary textual or binary data to pass via file descriptor 0 (STDIN) to the
executed processes. These settings have no effect unless C<StandardInput> is set to
C<data>. Use this option to embed process input data directly in the unit file.

C<StandardInputText> accepts arbitrary textual data. C-style escapes for special
characters as well as the usual C<%>-specifiers are resolved. Each time this setting is used
the specified text is appended to the per-unit data buffer, followed by a newline character (thus every use
appends a new line to the end of the buffer). Note that leading and trailing whitespace of lines configured
with this option is removed. If an empty line is specified the buffer is cleared (hence, in order to insert an
empty line, add an additional C<\n> to the end or beginning of a line).

C<StandardInputData> accepts arbitrary binary data, encoded in Base64. No escape sequences or specifiers are
resolved. Any whitespace in the encoded version is ignored during decoding.

Note that C<StandardInputText> and C<StandardInputData> operate on the
same data buffer, and may be mixed in order to configure both binary and textual data for the same input
stream. The textual or binary data is joined strictly in the order the settings appear in the unit
file. Assigning an empty string to either will reset the data buffer.

Please keep in mind that in order to maintain readability long unit file settings may be split into
multiple lines, by suffixing each line (except for the last) with a C<\> character (see
L<systemd.unit(5)> for
details). This is particularly useful for large data configured with these two options. Example: I< Optional. Type uniline.  > 

=head2 LogLevelMax

Configures filtering by log level of log messages generated by this unit. Takes a
syslog log level, one of C<emerg> (lowest log level, only highest priority
messages), C<alert>, C<crit>, C<err>, C<warning>,
C<notice>, C<info>, C<debug> (highest log level, also lowest priority
messages). See L<syslog(3)> for
details. By default no filtering is applied (i.e. the default maximum log level is C<debug>). Use
this option to configure the logging system to drop log messages of a specific service above the specified
level. For example, set C<LogLevelMax>C<info> in order to turn off debug logging
of a particularly chatty unit. Note that the configured level is applied to any log messages written by any
of the processes belonging to this unit, sent via any supported logging protocol. The filtering is applied
early in the logging pipeline, before any kind of further processing is done. Moreover, messages which pass
through this filter successfully might still be dropped by filters applied at a later stage in the logging
subsystem. For example, C<MaxLevelStore> configured in
L<journald.conf(5)> might
prohibit messages of higher log levels to be stored on disk, even though the per-unit
C<LogLevelMax> permitted it to be processed. I< Optional. Type uniline.  > 

=head2 LogExtraFields

Configures additional log metadata fields to include in all log records generated by processes
associated with this unit. This setting takes one or more journal field assignments in the format
C<FIELD=VALUE> separated by whitespace. See
L<systemd.journal-fields(7)> for
details on the journal field concept. Even though the underlying journal implementation permits binary field
values, this setting accepts only valid UTF-8 values. To include space characters in a journal field value,
enclose the assignment in double quotes ("). The usual specifiers are expanded in all assignments (see
below). Note that this setting is not only useful for attaching additional metadata to log records of a unit,
but given that all fields and values are indexed may also be used to implement cross-unit log record
matching. Assign an empty string to reset the list. I< Optional. Type uniline.  > 

=head2 LogRateLimitIntervalSec

Configures the rate limiting that is applied to messages generated by this unit. If, in the
time interval defined by C<LogRateLimitIntervalSec>, more messages than specified in
C<LogRateLimitBurst> are logged by a service, all further messages within the interval are
dropped until the interval is over. A message about the number of dropped messages is generated. The time
specification for C<LogRateLimitIntervalSec> may be specified in the following units: "s",
"min", "h", "ms", "us" (see
L<systemd.time(7)> for details).
The default settings are set by C<RateLimitIntervalSec> and C<RateLimitBurst>
configured in L<journald.conf(5)>.
I< Optional. Type uniline.  > 

=head2 LogRateLimitBurst

Configures the rate limiting that is applied to messages generated by this unit. If, in the
time interval defined by C<LogRateLimitIntervalSec>, more messages than specified in
C<LogRateLimitBurst> are logged by a service, all further messages within the interval are
dropped until the interval is over. A message about the number of dropped messages is generated. The time
specification for C<LogRateLimitIntervalSec> may be specified in the following units: "s",
"min", "h", "ms", "us" (see
L<systemd.time(7)> for details).
The default settings are set by C<RateLimitIntervalSec> and C<RateLimitBurst>
configured in L<journald.conf(5)>.
I< Optional. Type uniline.  > 

=head2 SyslogIdentifier

Sets the process name ("syslog tag") to prefix log lines sent to the logging
system or the kernel log buffer with. If not set, defaults to the process name of the executed process.  This
option is only useful when C<StandardOutput> or C<StandardError> are set to
C<journal>, C<syslog> or C<kmsg> (or to the same settings in
combination with C<+console>) and only applies to log messages written to stdout or
stderr. I< Optional. Type uniline.  > 

=head2 SyslogFacility

Sets the syslog facility identifier to use when logging. One of
C<kern>, C<user>, C<mail>, C<daemon>,
C<auth>, C<syslog>, C<lpr>, C<news>,
C<uucp>, C<cron>, C<authpriv>, C<ftp>,
C<local0>, C<local1>, C<local2>, C<local3>,
C<local4>, C<local5>, C<local6> or C<local7>. See
L<syslog(3)>
for details. This option is only useful when C<StandardOutput> or
C<StandardError> are set to C<journal>, C<syslog> or
C<kmsg> (or to the same settings in combination with C<+console>), and only applies
to log messages written to stdout or stderr. Defaults to C<daemon>. I< Optional. Type uniline.  > 

=head2 SyslogLevel

The default syslog log level to use when logging to the logging system or
the kernel log buffer. One of C<emerg>, C<alert>, C<crit>,
C<err>, C<warning>, C<notice>, C<info>,
C<debug>. See L<syslog(3)> for
details. This option is only useful when C<StandardOutput> or
C<StandardError> are set to C<journal>, C<syslog> or
C<kmsg> (or to the same settings in combination with C<+console>), and only applies
to log messages written to stdout or stderr. Note that individual lines output by executed processes may be
prefixed with a different log level which can be used to override the default log level specified here. The
interpretation of these prefixes may be disabled with C<SyslogLevelPrefix>, see below. For
details, see L<sd-daemon(3)>.
Defaults to C<info>. I< Optional. Type uniline.  > 

=head2 SyslogLevelPrefix

Takes a boolean argument. If true and C<StandardOutput> or
C<StandardError> are set to C<journal>, C<syslog> or
C<kmsg> (or to the same settings in combination with C<+console>), log lines
written by the executed process that are prefixed with a log level will be processed with this log level set
but the prefix removed. If set to false, the interpretation of these prefixes is disabled and the logged lines
are passed on as-is. This only applies to log messages written to stdout or stderr. For details about this
prefixing see L<sd-daemon(3)>.
Defaults to true. I< Optional. Type boolean.  > 

=head2 TTYPath

Sets the terminal device node to use if standard input, output, or error are connected to a TTY
(see above). Defaults to /dev/console. I< Optional. Type uniline.  > 

=head2 TTYReset

Reset the terminal device specified with C<TTYPath> before and after
execution.  Defaults to C<no>. I< Optional. Type uniline.  > 

=head2 TTYVHangup

Disconnect all clients which have opened the terminal device specified with
C<TTYPath> before and after execution. Defaults to C<no>. I< Optional. Type uniline.  > 

=head2 TTYVTDisallocate

If the terminal device specified with C<TTYPath> is a virtual console
terminal, try to deallocate the TTY before and after execution. This ensures that the screen and scrollback
buffer is cleared. Defaults to C<no>. I< Optional. Type uniline.  > 

=head2 UtmpIdentifier

Takes a four character identifier string for an L<utmp(5)> and wtmp entry
for this service. This should only be set for services such as getty implementations (such
as L<agetty(8)>) where utmp/wtmp
entries must be created and cleared before and after execution, or for services that shall be executed as if
they were run by a getty process (see below). If the configured string is longer than four
characters, it is truncated and the terminal four characters are used. This setting interprets %I style string
replacements. This setting is unset by default, i.e. no utmp/wtmp entries are created or cleaned up for this
service. I< Optional. Type uniline.  > 

=head2 UtmpMode

Takes one of C<init>, C<login> or C<user>. If
C<UtmpIdentifier> is set, controls which type of L<utmp(5)>/wtmp entries
for this service are generated. This setting has no effect unless C<UtmpIdentifier> is set
too. If C<init> is set, only an C<INIT_PROCESS> entry is generated and the
invoked process must implement a getty-compatible utmp/wtmp logic. If
C<login> is set, first an C<INIT_PROCESS> entry, followed by a
C<LOGIN_PROCESS> entry is generated. In this case, the invoked process must implement a
L<login(1)>-compatible
utmp/wtmp logic. If C<user> is set, first an C<INIT_PROCESS> entry, then a
C<LOGIN_PROCESS> entry and finally a C<USER_PROCESS> entry is
generated. In this case, the invoked process may be any process that is suitable to be run as session
leader. Defaults to C<init>. I< Optional. Type enum. choice: 'init', 'login', 'user'.  > 

=head2 KillMode

Specifies how processes of this unit shall be
killed. One of
C<control-group>,
C<process>,
C<mixed>,
C<none>.

If set to C<control-group>, all remaining
processes in the control group of this unit will be killed on
unit stop (for services: after the stop command is executed,
as configured with C<ExecStop>). If set to
C<process>, only the main process itself is
killed. If set to C<mixed>, the
C<SIGTERM> signal (see below) is sent to the
main process while the subsequent C<SIGKILL>
signal (see below) is sent to all remaining processes of the
unit's control group. If set to C<none>, no
process is killed. In this case, only the stop command will be
executed on unit stop, but no process be killed otherwise.
Processes remaining alive after stop are left in their control
group and the control group continues to exist after stop
unless it is empty.

Processes will first be terminated via
C<SIGTERM> (unless the signal to send is
changed via C<KillSignal>). Optionally, this
is immediately followed by a C<SIGHUP> (if
enabled with C<SendSIGHUP>). If then, after a
delay (configured via the C<TimeoutStopSec>
option), processes still remain, the termination request is
repeated with the C<SIGKILL> signal or the
signal specified via C<FinalKillSignal> (unless
this is disabled via the C<SendSIGKILL>
option). See
L<kill(2)>
for more information.

Defaults to
C<control-group>. I< Optional. Type uniline.  > 

=head2 KillSignal

Specifies which signal to use when killing a
service. This controls the signal that is sent as first step
of shutting down a unit (see above), and is usually followed
by C<SIGKILL> (see above and below). For a
list of valid signals, see
L<signal(7)>.
Defaults to C<SIGTERM>. 

Note that, right after sending the signal specified in
this setting, systemd will always send
C<SIGCONT>, to ensure that even suspended
tasks can be terminated cleanly. I< Optional. Type uniline.  > 

=head2 SendSIGHUP

Specifies whether to send
C<SIGHUP> to remaining processes immediately
after sending the signal configured with
C<KillSignal>. This is useful to indicate to
shells and shell-like programs that their connection has been
severed. Takes a boolean value. Defaults to "no".
I< Optional. Type boolean.  > 

=head2 SendSIGKILL

Specifies whether to send
C<SIGKILL> (or the signal specified by
C<FinalKillSignal>) to remaining processes
after a timeout, if the normal shutdown procedure left
processes of the service around. Takes a boolean value.
Defaults to "yes".
I< Optional. Type boolean.  > 

=head2 FinalKillSignal

Specifies which signal to send to remaining
processes after a timeout if C<SendSIGKILL>
is enabled. The signal configured here should be one that is
not typically caught and processed by services (C<SIGTERM>
is not suitable). Developers can find it useful to use this to
generate a coredump to troubleshoot why a service did not
terminate upon receiving the initial C<SIGTERM>
signal. This can be achieved by configuring C<LimitCORE>
and setting C<FinalKillSignal> to either
C<SIGQUIT> or C<SIGABRT>
Defaults to C<SIGKILL>.
I< Optional. Type uniline.  > 

=head2 WatchdogSignal

Specifies which signal to use to terminate the
service when the watchdog timeout expires (enabled through
C<WatchdogSec>). Defaults to C<SIGABRT>.
I< Optional. Type uniline.  > 

=head2 Type

Configures the process start-up type for this service unit. One of C<simple>,
C<exec>, C<forking>, C<oneshot>, C<dbus>,
C<notify> or C<idle>:

It is generally recommended to use C<Type>C<simple> for long-running
services whenever possible, as it is the simplest and fastest option. However, as this service type won't
propagate service start-up failures and doesn't allow ordering of other units against completion of
initialization of the service (which for example is useful if clients need to connect to the service through
some form of IPC, and the IPC channel is only established by the service itself — in contrast to doing this
ahead of time through socket or bus activation or similar), it might not be sufficient for many cases. If so,
C<notify> or C<dbus> (the latter only in case the service provides a D-Bus
interface) are the preferred options as they allow service program code to precisely schedule when to
consider the service started up successfully and when to proceed with follow-up units. The
C<notify> service type requires explicit support in the service codebase (as
sd_notify() or an equivalent API needs to be invoked by the service at the appropriate
time) — if it's not supported, then C<forking> is an alternative: it supports the traditional
UNIX service start-up protocol. Finally, C<exec> might be an option for cases where it is
enough to ensure the service binary is invoked, and where the service binary itself executes no or little
initialization on its own (and its initialization is unlikely to fail). Note that using any type other than
C<simple> possibly delays the boot process, as the service manager needs to wait for service
initialization to complete. It is hence recommended not to needlessly use any types other than
C<simple>. (Also note it is generally not recommended to use C<idle> or
C<oneshot> for long-running services.) I< Optional. Type uniline.  > 

=head2 RemainAfterExit

Takes a boolean value that specifies whether
the service shall be considered active even when all its
processes exited. Defaults to C<no>. I< Optional. Type boolean.  > 

=head2 GuessMainPID

Takes a boolean value that specifies whether
systemd should try to guess the main PID of a service if it
cannot be determined reliably. This option is ignored unless
C<Type=forking> is set and
C<PIDFile> is unset because for the other types
or with an explicitly configured PID file, the main PID is
always known. The guessing algorithm might come to incorrect
conclusions if a daemon consists of more than one process. If
the main PID cannot be determined, failure detection and
automatic restarting of a service will not work reliably.
Defaults to C<yes>. I< Optional. Type boolean.  > 

=head2 PIDFile

Takes a path referring to the PID file of the service. Usage of this option is recommended for
services where C<Type> is set to C<forking>. The path specified typically points
to a file below /run/. If a relative path is specified it is hence prefixed with
/run/. The service manager will read the PID of the main process of the service from this
file after start-up of the service. The service manager will not write to the file configured here, although it
will remove the file after the service has shut down if it still exists. The PID file does not need to be owned
by a privileged user, but if it is owned by an unprivileged user additional safety restrictions are enforced:
the file may not be a symlink to a file owned by a different user (neither directly nor indirectly), and the
PID file must refer to a process already belonging to the service. I< Optional. Type uniline.  > 

=head2 BusName

Takes a D-Bus bus name that this service is
reachable as. This option is mandatory for services where
C<Type> is set to
C<dbus>. I< Optional. Type uniline.  > 

=head2 ExecStart

Commands with their arguments that are
executed when this service is started. The value is split into
zero or more command lines according to the rules described
below (see section "Command Lines" below).

Unless C<Type> is C<oneshot>, exactly one command must be given. When
C<Type=oneshot> is used, zero or more commands may be specified. Commands may be specified by
providing multiple command lines in the same directive, or alternatively, this directive may be specified more
than once with the same effect. If the empty string is assigned to this option, the list of commands to start
is reset, prior assignments of this option will have no effect. If no C<ExecStart> is
specified, then the service must have C<RemainAfterExit=yes> and at least one
C<ExecStop> line set. (Services lacking both C<ExecStart> and
C<ExecStop> are not valid.)

For each of the specified commands, the first argument must be either an absolute path to an executable
or a simple file name without any slashes. Optionally, this filename may be prefixed with a number of special
characters:

C<@>, C<->, and one of
C<+>/C<!>/C<!!> may be used together and they can appear in any
order. However, only one of C<+>, C<!>, C<!!> may be used at a
time. Note that these prefixes are also supported for the other command line settings,
i.e. C<ExecStartPre>, C<ExecStartPost>, C<ExecReload>,
C<ExecStop> and C<ExecStopPost>.

If more than one command is specified, the commands are
invoked sequentially in the order they appear in the unit
file. If one of the commands fails (and is not prefixed with
C<->), other lines are not executed, and the
unit is considered failed.

Unless C<Type=forking> is set, the
process started via this command line will be considered the
main process of the daemon. I< Optional. Type list of uniline.  > 

=head2 ExecStartPre

Additional commands that are executed before
or after the command in C<ExecStart>,
respectively. Syntax is the same as for
C<ExecStart>, except that multiple command
lines are allowed and the commands are executed one after the
other, serially.

If any of those commands (not prefixed with
C<->) fail, the rest are not executed and the
unit is considered failed.

C<ExecStart> commands are only run after
all C<ExecStartPre> commands that were not prefixed
with a C<-> exit successfully.

C<ExecStartPost> commands are only run after the commands specified in
C<ExecStart> have been invoked successfully, as determined by C<Type>
(i.e. the process has been started for C<Type=simple> or C<Type=idle>, the last
C<ExecStart> process exited successfully for C<Type=oneshot>, the initial
process exited successfully for C<Type=forking>, C<READY=1> is sent for
C<Type=notify>, or the C<BusName> has been taken for
C<Type=dbus>).

Note that C<ExecStartPre> may not be
used to start long-running processes. All processes forked
off by processes invoked via C<ExecStartPre> will
be killed before the next service process is run.

Note that if any of the commands specified in C<ExecStartPre>,
C<ExecStart>, or C<ExecStartPost> fail (and are not prefixed with
C<->, see above) or time out before the service is fully up, execution continues with commands
specified in C<ExecStopPost>, the commands in C<ExecStop> are skipped. I< Optional. Type list of uniline.  > 

=head2 ExecStartPost

Additional commands that are executed before
or after the command in C<ExecStart>,
respectively. Syntax is the same as for
C<ExecStart>, except that multiple command
lines are allowed and the commands are executed one after the
other, serially.

If any of those commands (not prefixed with
C<->) fail, the rest are not executed and the
unit is considered failed.

C<ExecStart> commands are only run after
all C<ExecStartPre> commands that were not prefixed
with a C<-> exit successfully.

C<ExecStartPost> commands are only run after the commands specified in
C<ExecStart> have been invoked successfully, as determined by C<Type>
(i.e. the process has been started for C<Type=simple> or C<Type=idle>, the last
C<ExecStart> process exited successfully for C<Type=oneshot>, the initial
process exited successfully for C<Type=forking>, C<READY=1> is sent for
C<Type=notify>, or the C<BusName> has been taken for
C<Type=dbus>).

Note that C<ExecStartPre> may not be
used to start long-running processes. All processes forked
off by processes invoked via C<ExecStartPre> will
be killed before the next service process is run.

Note that if any of the commands specified in C<ExecStartPre>,
C<ExecStart>, or C<ExecStartPost> fail (and are not prefixed with
C<->, see above) or time out before the service is fully up, execution continues with commands
specified in C<ExecStopPost>, the commands in C<ExecStop> are skipped. I< Optional. Type list of uniline.  > 

=head2 ExecReload

Commands to execute to trigger a configuration
reload in the service. This argument takes multiple command
lines, following the same scheme as described for
C<ExecStart> above. Use of this setting is
optional. Specifier and environment variable substitution is
supported here following the same scheme as for
C<ExecStart>.

One additional, special environment variable is set: if
known, C<$MAINPID> is set to the main process
of the daemon, and may be used for command lines like the
following:

Note however that reloading a daemon by sending a signal
(as with the example line above) is usually not a good choice,
because this is an asynchronous operation and hence not
suitable to order reloads of multiple services against each
other. It is strongly recommended to set
C<ExecReload> to a command that not only
triggers a configuration reload of the daemon, but also
synchronously waits for it to complete. I< Optional. Type list of uniline.  > 

=head2 ExecStop

Commands to execute to stop the service
started via C<ExecStart>. This argument takes
multiple command lines, following the same scheme as described
for C<ExecStart> above. Use of this setting
is optional. After the commands configured in this option are
run, it is implied that the service is stopped, and any processes
remaining for it are terminated
according to the C<KillMode> setting (see
L<systemd.kill(5)>).
If this option is not specified, the process is terminated by
sending the signal specified in C<KillSignal>
when service stop is requested. Specifier and environment
variable substitution is supported (including
C<$MAINPID>, see above).

Note that it is usually not sufficient to specify a command for this setting that only asks the service
to terminate (for example, by queuing some form of termination signal for it), but does not wait for it to do
so. Since the remaining processes of the services are killed according to C<KillMode> and
C<KillSignal> as described above immediately after the command exited, this may not result in
a clean stop. The specified command should hence be a synchronous operation, not an asynchronous one.

Note that the commands specified in C<ExecStop> are only executed when the service
started successfully first. They are not invoked if the service was never started at all, or in case its
start-up failed, for example because any of the commands specified in C<ExecStart>,
C<ExecStartPre> or C<ExecStartPost> failed (and weren't prefixed with
C<->, see above) or timed out. Use C<ExecStopPost> to invoke commands when a
service failed to start up correctly and is shut down again. Also note that, service restart requests are
implemented as stop operations followed by start operations. This means that C<ExecStop> and
C<ExecStopPost> are executed during a service restart operation.

It is recommended to use this setting for commands that communicate with the service requesting clean
termination. When the commands specified with this option are executed it should be assumed that the service is
still fully up and is able to react correctly to all commands. For post-mortem clean-up steps use
C<ExecStopPost> instead. I< Optional. Type list of uniline.  > 

=head2 ExecStopPost

Additional commands that are executed after the service is stopped. This includes cases where
the commands configured in C<ExecStop> were used, where the service does not have any
C<ExecStop> defined, or where the service exited unexpectedly. This argument takes multiple
command lines, following the same scheme as described for C<ExecStart>. Use of these settings
is optional. Specifier and environment variable substitution is supported. Note that – unlike
C<ExecStop> – commands specified with this setting are invoked when a service failed to start
up correctly and is shut down again.

It is recommended to use this setting for clean-up operations that shall be executed even when the
service failed to start up correctly. Commands configured with this setting need to be able to operate even if
the service failed starting up half-way and left incompletely initialized data around. As the service's
processes have been terminated already when the commands specified with this setting are executed they should
not attempt to communicate with them.

Note that all commands that are configured with this setting are invoked with the result code of the
service, as well as the main process' exit code and status, set in the C<$SERVICE_RESULT>,
C<$EXIT_CODE> and C<$EXIT_STATUS> environment variables, see
L<systemd.exec(5)> for
details. I< Optional. Type list of uniline.  > 

=head2 RestartSec

Configures the time to sleep before restarting
a service (as configured with C<Restart>).
Takes a unit-less value in seconds, or a time span value such
as "5min 20s". Defaults to 100ms. I< Optional. Type uniline.  > 

=head2 TimeoutStartSec

Configures the time to wait for start-up. If a
daemon service does not signal start-up completion within the
configured time, the service will be considered failed and
will be shut down again. Takes a unit-less value in seconds,
or a time span value such as "5min 20s". Pass
C<infinity> to disable the timeout logic. Defaults to
C<DefaultTimeoutStartSec> from the manager
configuration file, except when
C<Type=oneshot> is used, in which case the
timeout is disabled by default (see
L<systemd-system.conf(5)>).

If a service of C<Type=notify> sends C<EXTEND_TIMEOUT_USEC=…>, this may cause
the start time to be extended beyond C<TimeoutStartSec>. The first receipt of this message
must occur before C<TimeoutStartSec> is exceeded, and once the start time has exended beyond
C<TimeoutStartSec>, the service manager will allow the service to continue to start, provided
the service repeats C<EXTEND_TIMEOUT_USEC=…> within the interval specified until the service
startup status is finished by C<READY=1>. (see
L<sd_notify(3)>).
I< Optional. Type uniline.  > 

=head2 TimeoutStopSec

This option serves two purposes. First, it configures the time to wait for each
C<ExecStop> command. If any of them times out, subsequent C<ExecStop> commands
are skipped and the service will be terminated by C<SIGTERM>. If no C<ExecStop>
commands are specified, the service gets the C<SIGTERM> immediately. Second, it configures the time
to wait for the service itself to stop. If it doesn't terminate in the specified time, it will be forcibly terminated
by C<SIGKILL> (see C<KillMode> in
L<systemd.kill(5)>).
Takes a unit-less value in seconds, or a time span value such
as "5min 20s". Pass C<infinity> to disable the
timeout logic. Defaults to
C<DefaultTimeoutStopSec> from the manager
configuration file (see
L<systemd-system.conf(5)>).

If a service of C<Type=notify> sends C<EXTEND_TIMEOUT_USEC=…>, this may cause
the stop time to be extended beyond C<TimeoutStopSec>. The first receipt of this message
must occur before C<TimeoutStopSec> is exceeded, and once the stop time has exended beyond
C<TimeoutStopSec>, the service manager will allow the service to continue to stop, provided
the service repeats C<EXTEND_TIMEOUT_USEC=…> within the interval specified, or terminates itself
(see L<sd_notify(3)>).
I< Optional. Type uniline.  > 

=head2 TimeoutSec

A shorthand for configuring both
C<TimeoutStartSec> and
C<TimeoutStopSec> to the specified value.
I< Optional. Type uniline.  > 

=head2 RuntimeMaxSec

Configures a maximum time for the service to run. If this is used and the service has been
active for longer than the specified time it is terminated and put into a failure state. Note that this setting
does not have any effect on C<Type=oneshot> services, as they terminate immediately after
activation completed. Pass C<infinity> (the default) to configure no runtime
limit.

If a service of C<Type=notify> sends C<EXTEND_TIMEOUT_USEC=…>, this may cause
the runtime to be extended beyond C<RuntimeMaxSec>. The first receipt of this message
must occur before C<RuntimeMaxSec> is exceeded, and once the runtime has exended beyond
C<RuntimeMaxSec>, the service manager will allow the service to continue to run, provided
the service repeats C<EXTEND_TIMEOUT_USEC=…> within the interval specified until the service
shutdown is achieved by C<STOPPING=1> (or termination). (see
L<sd_notify(3)>).
I< Optional. Type uniline.  > 

=head2 WatchdogSec

Configures the watchdog timeout for a service.
The watchdog is activated when the start-up is completed. The
service must call
L<sd_notify(3)>
regularly with C<WATCHDOG=1> (i.e. the
"keep-alive ping"). If the time between two such calls is
larger than the configured time, then the service is placed in
a failed state and it will be terminated with
C<SIGABRT> (or the signal specified by
C<WatchdogSignal>). By setting
C<Restart> to C<on-failure>,
C<on-watchdog>, C<on-abnormal> or
C<always>, the service will be automatically
restarted. The time configured here will be passed to the
executed service process in the
C<WATCHDOG_USEC> environment variable. This
allows daemons to automatically enable the keep-alive pinging
logic if watchdog support is enabled for the service. If this
option is used, C<NotifyAccess> (see below)
should be set to open access to the notification socket
provided by systemd. If C<NotifyAccess> is
not set, it will be implicitly set to C<main>.
Defaults to 0, which disables this feature. The service can
check whether the service manager expects watchdog keep-alive
notifications. See
L<sd_watchdog_enabled(3)>
for details.
L<sd_event_set_watchdog(3)>
may be used to enable automatic watchdog notification support.
I< Optional. Type uniline.  > 

=head2 Restart

Configures whether the service shall be
restarted when the service process exits, is killed, or a
timeout is reached. The service process may be the main
service process, but it may also be one of the processes
specified with C<ExecStartPre>,
C<ExecStartPost>,
C<ExecStop>,
C<ExecStopPost>, or
C<ExecReload>. When the death of the process
is a result of systemd operation (e.g. service stop or
restart), the service will not be restarted. Timeouts include
missing the watchdog "keep-alive ping" deadline and a service
start, reload, and stop operation timeouts.

Takes one of
C<no>,
C<on-success>,
C<on-failure>,
C<on-abnormal>,
C<on-watchdog>,
C<on-abort>, or
C<always>.
If set to C<no> (the default), the service will
not be restarted. If set to C<on-success>, it
will be restarted only when the service process exits cleanly.
In this context, a clean exit means an exit code of 0, or one
of the signals
C<SIGHUP>,
C<SIGINT>,
C<SIGTERM> or
C<SIGPIPE>, and
additionally, exit statuses and signals specified in
C<SuccessExitStatus>. If set to
C<on-failure>, the service will be restarted
when the process exits with a non-zero exit code, is
terminated by a signal (including on core dump, but excluding
the aforementioned four signals), when an operation (such as
service reload) times out, and when the configured watchdog
timeout is triggered. If set to C<on-abnormal>,
the service will be restarted when the process is terminated
by a signal (including on core dump, excluding the
aforementioned four signals), when an operation times out, or
when the watchdog timeout is triggered. If set to
C<on-abort>, the service will be restarted only
if the service process exits due to an uncaught signal not
specified as a clean exit status. If set to
C<on-watchdog>, the service will be restarted
only if the watchdog timeout for the service expires. If set
to C<always>, the service will be restarted
regardless of whether it exited cleanly or not, got terminated
abnormally by a signal, or hit a timeout.

As exceptions to the setting above, the service will not
be restarted if the exit code or signal is specified in
C<RestartPreventExitStatus> (see below) or
the service is stopped with systemctl stop
or an equivalent operation. Also, the services will always be
restarted if the exit code or signal is specified in
C<RestartForceExitStatus> (see below).

Note that service restart is subject to unit start rate
limiting configured with C<StartLimitIntervalSec>
and C<StartLimitBurst>, see
L<systemd.unit(5)>
for details.  A restarted service enters the failed state only
after the start limits are reached.

Setting this to C<on-failure> is the
recommended choice for long-running services, in order to
increase reliability by attempting automatic recovery from
errors. For services that shall be able to terminate on their
own choice (and avoid immediate restarting),
C<on-abnormal> is an alternative choice. I< Optional. Type enum. choice: 'no', 'on-success', 'on-failure', 'on-abnormal', 'on-watchdog', 'on-abort', 'always'.  > 

=head2 SuccessExitStatus

Takes a list of exit status definitions that,
when returned by the main service process, will be considered
successful termination, in addition to the normal successful
exit code 0 and the signals C<SIGHUP>,
C<SIGINT>, C<SIGTERM>, and
C<SIGPIPE>. Exit status definitions can
either be numeric exit codes or termination signal names,
separated by spaces. For example:

    SuccessExitStatus=1 2 8 SIGKILL

ensures that exit codes 1, 2, 8 and
the termination signal C<SIGKILL> are
considered clean service terminations.

This option may appear more than once, in which case the
list of successful exit statuses is merged. If the empty
string is assigned to this option, the list is reset, all
prior assignments of this option will have no
effect. I< Optional. Type uniline.  > 

=head2 RestartPreventExitStatus

Takes a list of exit status definitions that,
when returned by the main service process, will prevent
automatic service restarts, regardless of the restart setting
configured with C<Restart>. Exit status
definitions can either be numeric exit codes or termination
signal names, and are separated by spaces. Defaults to the
empty list, so that, by default, no exit status is excluded
from the configured restart logic. For example:

    RestartPreventExitStatus=1 6 SIGABRT

ensures that exit codes 1 and 6 and the termination signal
C<SIGABRT> will not result in automatic
service restarting. This option may appear more than once, in
which case the list of restart-preventing statuses is
merged. If the empty string is assigned to this option, the
list is reset and all prior assignments of this option will
have no effect. I< Optional. Type uniline.  > 

=head2 RestartForceExitStatus

Takes a list of exit status definitions that,
when returned by the main service process, will force automatic
service restarts, regardless of the restart setting configured
with C<Restart>. The argument format is
similar to
C<RestartPreventExitStatus>. I< Optional. Type uniline.  > 

=head2 RootDirectoryStartOnly

Takes a boolean argument. If true, the root
directory, as configured with the
C<RootDirectory> option (see
L<systemd.exec(5)>
for more information), is only applied to the process started
with C<ExecStart>, and not to the various
other C<ExecStartPre>,
C<ExecStartPost>,
C<ExecReload>, C<ExecStop>,
and C<ExecStopPost> commands. If false, the
setting is applied to all configured commands the same way.
Defaults to false. I< Optional. Type boolean.  > 

=head2 NonBlocking

Set the C<O_NONBLOCK> flag for all file descriptors passed via socket-based
activation. If true, all file descriptors >= 3 (i.e. all except stdin, stdout, stderr), excluding those passed
in via the file descriptor storage logic (see C<FileDescriptorStoreMax> for details), will
have the C<O_NONBLOCK> flag set and hence are in non-blocking mode. This option is only
useful in conjunction with a socket unit, as described in
L<systemd.socket(5)> and has no
effect on file descriptors which were previously saved in the file-descriptor store for example.  Defaults to
false. I< Optional. Type uniline.  > 

=head2 NotifyAccess

Controls access to the service status notification socket, as accessible via the
L<sd_notify(3)> call. Takes one
of C<none> (the default), C<main>, C<exec> or
C<all>. If C<none>, no daemon status updates are accepted from the service
processes, all status update messages are ignored. If C<main>, only service updates sent from the
main process of the service are accepted. If C<exec>, only service updates sent from any of the
main or control processes originating from one of the C<Exec*=> commands are accepted. If
C<all>, all services updates from all members of the service's control group are accepted. This
option should be set to open access to the notification socket when using C<Type=notify> or
C<WatchdogSec> (see above). If those options are used but C<NotifyAccess> is
not configured, it will be implicitly set to C<main>.

Note that sd_notify() notifications may be attributed to units correctly only if
either the sending process is still around at the time PID 1 processes the message, or if the sending process
is explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally
forked off the process, i.e. on all processes that match C<main> or
C<exec>. Conversely, if an auxiliary process of the unit sends an
sd_notify() message and immediately exits, the service manager might not be able to
properly attribute the message to the unit, and thus will ignore it, even if
C<NotifyAccess>C<all> is set for it. I< Optional. Type enum. choice: 'none', 'main', 'exec', 'all'.  > 

=head2 Sockets

Specifies the name of the socket units this
service shall inherit socket file descriptors from when the
service is started. Normally, it should not be necessary to use
this setting, as all socket file descriptors whose unit shares
the same name as the service (subject to the different unit
name suffix of course) are passed to the spawned
process.

Note that the same socket file descriptors may be passed
to multiple processes simultaneously. Also note that a
different service may be activated on incoming socket traffic
than the one which is ultimately configured to inherit the
socket file descriptors. Or, in other words: the
C<Service> setting of
.socket units does not have to match the
inverse of the C<Sockets> setting of the
.service it refers to.

This option may appear more than once, in which case the
list of socket units is merged. If the empty string is
assigned to this option, the list of sockets is reset, and all
prior uses of this setting will have no
effect. I< Optional. Type uniline.  > 

=head2 FileDescriptorStoreMax

Configure how many file descriptors may be stored in the service manager for the service using
L<sd_pid_notify_with_fds(3)>'s
C<FDSTORE=1> messages. This is useful for implementing services that can restart after an
explicit request or a crash without losing state. Any open sockets and other file descriptors which should not
be closed during the restart may be stored this way. Application state can either be serialized to a file in
/run, or better, stored in a
L<memfd_create(2)> memory file
descriptor. Defaults to 0, i.e. no file descriptors may be stored in the service manager. All file descriptors
passed to the service manager from a specific service are passed back to the service's main process on the next
service restart. Any file descriptors passed to the service manager are automatically closed when
C<POLLHUP> or C<POLLERR> is seen on them, or when the service is fully
stopped and no job is queued or being executed for it. If this option is used, C<NotifyAccess>
(see above) should be set to open access to the notification socket provided by systemd. If
C<NotifyAccess> is not set, it will be implicitly set to
C<main>. I< Optional. Type uniline.  > 

=head2 USBFunctionDescriptors

Configure the location of a file containing
USB
FunctionFS descriptors, for implementation of USB
gadget functions. This is used only in conjunction with a
socket unit with C<ListenUSBFunction>
configured. The contents of this file are written to the
ep0 file after it is
opened. I< Optional. Type uniline.  > 

=head2 USBFunctionStrings

Configure the location of a file containing
USB FunctionFS strings.  Behavior is similar to
C<USBFunctionDescriptors>
above. I< Optional. Type uniline.  > 

=head2 FailureAction

B<Deprecated> I< Optional. Type uniline.  > 

=head2 SuccessAction

B<Deprecated> I< Optional. Type uniline.  > 

=head2 StartLimitBurst

B<Deprecated> I< Optional. Type uniline.  > 

=head2 StartLimitInterval

B<Deprecated> I< Optional. Type uniline.  > 

=head2 RebootArgument

B<Deprecated> I< Optional. Type uniline.  > 

=head1 SEE ALSO

=over

=item *

L<cme>

=back

=head1 COPYRIGHT

=over

=item 2010-2016 Lennart Poettering and others

=item 2016 Dominique Dumont


=back

=head1 LICENSE

=over

=item LGPLv2.1+


=back

=cut