Ubuntu Manpage: Config::Model::models::Systemd::Section::Service

Provided by: libconfig-model-systemd-perl_0.251.1-1_all

NAME

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

DESCRIPTION

       Configuration classes used by Config::Model

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

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

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

       If SysV init compat is enabled, systemd automatically creates service units that wrap SysV
       init scripts (the service name is the same as the name of the script, with a ".service"
       suffix added); see systemd-sysv-generator(8).

       The systemd-run(1) command allows creating ".service" and ".scope" units dynamically and
       transiently from the command line.  This configuration class was generated from systemd
       documentation.  by parse-man.pl <https://github.com/dod38fr/config-model-
       systemd/contrib/parse-man.pl>

Elements

CPUAccounting
Turn on CPU usage accounting for this unit. Takes a boolean argument. Note that turning on
CPU accounting for one unit will also implicitly turn it on for all units contained in the
same slice and for all its parent slices and the units contained therein. The system
default for this setting may be controlled with "DefaultCPUAccounting" in
systemd-system.conf(5). Optional. Type boolean.

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
"cpu.weight" control group attribute. The allowed range is 1 to 10000. Defaults to 100.
For details about this control group attribute, see Control Groups v2
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html> and CFS Scheduler
<https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html>. The available
CPU time is split up among all units within one slice relative to their CPU time weight. A
higher weight means more CPU time, a lower weight means less.

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

These settings replace "CPUShares" and "StartupCPUShares". Optional. Type integer.

upstream_default value :
100

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
"cpu.weight" control group attribute. The allowed range is 1 to 10000. Defaults to 100.
For details about this control group attribute, see Control Groups v2
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html> and CFS Scheduler
<https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html>. The available
CPU time is split up among all units within one slice relative to their CPU time weight. A
higher weight means more CPU time, a lower weight means less.

These settings replace "CPUShares" and "StartupCPUShares". Optional. Type integer.

upstream_default value :
100

CPUQuota
Assign the specified CPU time quota to the processes executed. Takes a percentage value,
suffixed with "%". The percentage specifies how much CPU time the unit shall get at
maximum, relative to the total CPU time available on one CPU. Use values > 100% for
allotting CPU time on more than one CPU. This controls the "cpu.max" attribute on the
unified control group hierarchy and "cpu.cfs_quota_us" on legacy. For details about these
control group attributes, see Control Groups v2
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html> and sched-bwc.txt
<https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt>. Setting "CPUQuota" to
an empty value unsets the quota.

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

CPUQuotaPeriodSec
Assign the duration over which the CPU time quota specified by "CPUQuota" is measured.
Takes a time duration value in seconds, with an optional suffix such as "ms" for
milliseconds (or "s" for seconds.) The default setting is 100ms. The period is clamped to
the range supported by the kernel, which is [1ms, 1000ms]. Additionally, the period is
adjusted up so that the quota interval is also at least 1ms. Setting "CPUQuotaPeriodSec"
to an empty value resets it to the default.

This controls the second field of "cpu.max" attribute on the unified control group
hierarchy and "cpu.cfs_period_us" on legacy. For details about these control group
attributes, see Control Groups v2 <https://www.kernel.org/doc/html/latest/admin-
guide/cgroup-v2.html> and CFS Scheduler
<https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html>.

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

AllowedCPUs
Restrict processes to be executed on specific CPUs. Takes a list of CPU indices or ranges
separated by either whitespace or commas. CPU ranges are specified by the lower and upper
CPU indices separated by a dash.

Setting "AllowedCPUs" or "StartupAllowedCPUs" doesn't guarantee that all of the CPUs will
be used by the processes as it may be limited by parent units. The effective configuration
is reported as "EffectiveCPUs".

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

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

StartupAllowedCPUs
Restrict processes to be executed on specific CPUs. Takes a list of CPU indices or ranges
separated by either whitespace or commas. CPU ranges are specified by the lower and upper
CPU indices separated by a dash.

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

AllowedMemoryNodes
Restrict processes to be executed on specific memory NUMA nodes. Takes a list of memory
NUMA nodes indices or ranges separated by either whitespace or commas. Memory NUMA nodes
ranges are specified by the lower and upper NUMA nodes indices separated by a dash.

Setting "AllowedMemoryNodes" or "StartupAllowedMemoryNodes" doesn't guarantee that all of
the memory NUMA nodes will be used by the processes as it may be limited by parent units.
The effective configuration is reported as "EffectiveMemoryNodes".

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

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

StartupAllowedMemoryNodes
Restrict processes to be executed on specific memory NUMA nodes. Takes a list of memory
NUMA nodes indices or ranges separated by either whitespace or commas. Memory NUMA nodes
ranges are specified by the lower and upper NUMA nodes indices separated by a dash.

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

MemoryAccounting
Turn on process and kernel memory accounting for this unit. Takes a boolean argument. Note
that turning on memory accounting for one unit will also implicitly turn it on for all
units contained in the same slice and for all its parent slices and the units contained
therein. The system default for this setting may be controlled with
"DefaultMemoryAccounting" in systemd-system.conf(5). Optional. Type boolean.

MemoryMin
Specify the memory usage protection of the executed processes in this unit. When
reclaiming memory, the unit is treated as if it was using less memory resulting in memory
to be preferentially reclaimed from unprotected units. Using "MemoryLow" results in a
weaker protection where memory may still be reclaimed to avoid invoking the OOM killer in
case there is no other reclaimable memory.

For a protection to be effective, it is generally required to set a corresponding
allocation on all ancestors, which is then distributed between children (with the
exception of the root slice). Any "MemoryMin" or "MemoryLow" allocation that is not
explicitly distributed to specific children is used to create a shared protection for all
children. As this is a shared protection, the children will freely compete for the
memory.

Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified
memory size is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base
1024), respectively. Alternatively, a percentage value may be specified, which is taken
relative to the installed physical memory on the system. If assigned the special value
"infinity", all available memory is protected, which may be useful in order to always
inherit all of the protection afforded by ancestors. This controls the "memory.min" or
"memory.low" control group attribute. For details about this control group attribute, see
Memory Interface Files <https://www.kernel.org/doc/html/latest/admin-guide/cgroup-
v2.html#memory-interface-files>.

This setting is supported only if the unified control group hierarchy is used and disables
"MemoryLimit".

Units may have their children use a default "memory.min" or "memory.low" value by
specifying "DefaultMemoryMin" or "DefaultMemoryLow", which has the same semantics as
"MemoryMin" and "MemoryLow". This setting does not affect "memory.min" or "memory.low" in
the unit itself. Using it to set a default child allocation is only useful on kernels
older than 5.7, which do not support the "memory_recursiveprot" cgroup2 mount option.
Optional. Type uniline.

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

Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified
memory size is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base
1024), respectively. Alternatively, a percentage value may be specified, which is taken
relative to the installed physical memory on the system. If assigned the special value
"infinity", no memory throttling is applied. This controls the "memory.high" control group
attribute. For details about this control group attribute, see Memory Interface Files
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-
files>.

This setting is supported only if the unified control group hierarchy is used and disables
"MemoryLimit". Optional. Type uniline.

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 "MemoryHigh" as the main control mechanism and use
"MemoryMax" as the last line of defense.

Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified
memory size is parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base
1024), respectively. Alternatively, a percentage value may be specified, which is taken
relative to the installed physical memory on the system. If assigned the special value
"infinity", no memory limit is applied. This controls the "memory.max" control group
attribute. For details about this control group attribute, see Memory Interface Files
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-
files>.

This setting replaces "MemoryLimit". Optional. Type uniline.

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 "infinity", no swap limit is applied. This
controls the "memory.swap.max" control group attribute. For details about this control
group attribute, see Memory Interface Files <https://www.kernel.org/doc/html/latest/admin-
guide/cgroup-v2.html#memory-interface-files>.

This setting is supported only if the unified control group hierarchy is used and disables
"MemoryLimit". Optional. Type uniline.

TasksAccounting
Turn on task accounting for this unit. Takes a boolean argument. If enabled, the system
manager will keep track of the number of tasks in the unit. The number of tasks accounted
this way includes both kernel threads and userspace processes, with each thread counting
individually. Note that turning on tasks accounting for one unit will also implicitly turn
it on for all units contained in the same slice and for all its parent slices and the
units contained therein. The system default for this setting may be controlled with
"DefaultTasksAccounting" in systemd-system.conf(5). Optional. Type boolean.

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
"infinity", no tasks limit is applied. This controls the "pids.max" control group
attribute. For details about this control group attribute, see Process Number Controller
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/pids.html>.

The system default for this setting may be controlled with "DefaultTasksMax" in
systemd-system.conf(5). Optional. Type uniline.

IOAccounting
Turn on Block I/O accounting for this unit, if the unified control group hierarchy is used
on the system. Takes a boolean argument. Note that turning on block I/O accounting for one
unit will also implicitly turn it on for all units contained in the same slice and all for
its parent slices and the units contained therein. The system default for this setting may
be controlled with "DefaultIOAccounting" in systemd-system.conf(5).

This setting replaces "BlockIOAccounting" and disables settings prefixed with "BlockIO" or
"StartupBlockIO". Optional. Type boolean.

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 "io.weight" control group
attribute, which defaults to 100. For details about this control group attribute, see IO
Interface Files <https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-
interface-files>. The available I/O bandwidth is split up among all units within one
slice relative to their block I/O weight. A higher weight means more I/O bandwidth, a
lower weight means less.

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

These settings replace "BlockIOWeight" and "StartupBlockIOWeight" and disable settings
prefixed with "BlockIO" or "StartupBlockIO". Optional. Type uniline.

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 "io.weight" control group
attribute, which defaults to 100. For details about this control group attribute, see IO
Interface Files <https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-
interface-files>. The available I/O bandwidth is split up among all units within one
slice relative to their block I/O weight. A higher weight means more I/O bandwidth, a
lower weight means less.

These settings replace "BlockIOWeight" and "StartupBlockIOWeight" and disable settings
prefixed with "BlockIO" or "StartupBlockIO". Optional. Type uniline.

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: "/dev/sda 1000"). The file path may be specified as path to a block device node
or as any other file, in which case the backing block device of the file system of the
file is determined. This controls the "io.weight" control group attribute, which defaults
to 100. Use this option multiple times to set weights for multiple devices. For details
about this control group attribute, see IO Interface Files
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files>.

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

The specified device node should reference a block device that has an I/O scheduler
associated, i.e. should not refer to partition or loopback block devices, but to the
originating, physical device. When a path to a regular file or directory is specified it
is attempted to discover the correct originating device backing the file system of the
specified path. This works correctly only for simpler cases, where the file system is
directly placed on a partition or physical block device, or where simple 1:1 encryption
using dm-crypt/LUKS is used. This discovery does not cover complex storage and in
particular RAID and volume management storage devices. Optional. Type uniline.

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 "io.max" control
group attributes. Use this option multiple times to set bandwidth limits for multiple
devices. For details about this control group attribute, see IO Interface Files
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files>.

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

Similar restrictions on block device discovery as for "IODeviceWeight" apply, see above.
Optional. Type uniline.

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 "io.max" control
group attributes. Use this option multiple times to set bandwidth limits for multiple
devices. For details about this control group attribute, see IO Interface Files
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files>.

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

Similar restrictions on block device discovery as for "IODeviceWeight" apply, see above.
Optional. Type uniline.

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 "io.max" control
group attributes. Use this option multiple times to set IOPS limits for multiple devices.
For details about this control group attribute, see IO Interface Files
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files>.

These settings are supported only if the unified control group hierarchy is used and
disable settings prefixed with "BlockIO" or "StartupBlockIO".

Similar restrictions on block device discovery as for "IODeviceWeight" apply, see above.
Optional. Type uniline.

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 "io.max" control
group attributes. Use this option multiple times to set IOPS limits for multiple devices.
For details about this control group attribute, see IO Interface Files
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files>.

These settings are supported only if the unified control group hierarchy is used and
disable settings prefixed with "BlockIO" or "StartupBlockIO".

Similar restrictions on block device discovery as for "IODeviceWeight" apply, see above.
Optional. Type uniline.

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 "io.latency" control group attribute. Use this option multiple times to set latency
target for multiple devices. For details about this control group attribute, see IO
Interface Files <https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-
interface-files>.

Implies "IOAccounting=yes".

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

Similar restrictions on block device discovery as for "IODeviceWeight" apply, see above.
Optional. Type uniline.

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 X and never to the service unit it might have activated, even if the
socket is used by it.

The system default for this setting may be controlled with "DefaultIPAccounting" in
systemd-system.conf(5). Optional. Type boolean.

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

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

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

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

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

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

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. Optional. Type
uniline.

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

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:

IPIngressFilterPath
Add custom network traffic filters implemented as BPF programs, applying to all IP packets
sent and received over "AF_INET" and "AF_INET6" sockets. Takes an absolute path to a
pinned BPF program in the BPF virtual filesystem ("/sys/fs/bpf/").

The filters configured with this option are applied to all sockets created by processes of
this unit (or in the case of socket units, associated with it). The filters are loaded in
addition to filters any of the parent slice units this unit might be a member of as well
as any "IPAddressAllow" and "IPAddressDeny" filters in any of these units. By default
there are no filters specified.

If these settings are used multiple times in the same unit all the specified programs are
attached. If an empty string is assigned to these settings the program list is reset and
all previous specified programs ignored.

If the path BPF_FS_PROGRAM_PATH in "IPIngressFilterPath" assignment is already being
handled by "BPFProgram" ingress hook, e.g. "BPFProgram""ingress":BPF_FS_PROGRAM_PATH, the
assignment will be still considered valid and the program will be attached to a cgroup.
Same for "IPEgressFilterPath" path and "egress" hook.

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

Note that these settings might not be supported on some systems (for example if eBPF
control group support is not enabled in the underlying kernel or container manager). These
settings will fail the service in that case. If compatibility with such systems is desired
it is hence recommended to attach your filter manually (requires "Delegate""yes") instead
of using this setting. Optional. Type uniline.

IPEgressFilterPath
Add custom network traffic filters implemented as BPF programs, applying to all IP packets
sent and received over "AF_INET" and "AF_INET6" sockets. Takes an absolute path to a
pinned BPF program in the BPF virtual filesystem ("/sys/fs/bpf/").

Note that these settings might not be supported on some systems (for example if eBPF
control group support is not enabled in the underlying kernel or container manager). These
settings will fail the service in that case. If compatibility with such systems is desired
it is hence recommended to attach your filter manually (requires "Delegate""yes") instead
of using this setting. Optional. Type uniline.

BPFProgram
Add a custom cgroup BPF program.

"BPFProgram" allows attaching BPF hooks to the cgroup of a systemd unit. (This
generalizes the functionality exposed via "IPEgressFilterPath" for egress and
"IPIngressFilterPath" for ingress.) Cgroup-bpf hooks in the form of BPF programs loaded
to the BPF filesystem are attached with cgroup-bpf attach flags determined by the unit.
For details about attachment types and flags see
<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/include/uapi/linux/bpf.h>.
For general BPF documentation please refer to
<https://www.kernel.org/doc/html/latest/bpf/index.html>.

The specification of BPF program consists of a type followed by a program-path with ":" as
the separator: type":"program-path.

type is the string name of BPF attach type also used in bpftool. type can be one of
"egress", "ingress", "sock_create", "sock_ops", "device", "bind4", "bind6", "connect4",
"connect6", "post_bind4", "post_bind6", "sendmsg4", "sendmsg6", "sysctl", "recvmsg4",
"recvmsg6", "getsockopt", "setsockopt".

Setting "BPFProgram" to an empty value makes previous assignments ineffective.

Multiple assignments of the same type:program-path value have the same effect as a single
assignment: the program with the path program-path will be attached to cgroup hook type
just once.

If BPF "egress" pinned to program-path path is already being handled by
"IPEgressFilterPath", "BPFProgram" assignment will be considered valid and "BPFProgram"
will be attached to a cgroup. Similarly for "ingress" hook and "IPIngressFilterPath"
assignment.

BPF programs passed with "BPFProgram" are attached to the cgroup of a unit with BPF attach
flag "multi", that allows further attachments of the same type within cgroup hierarchy
topped by the unit cgroup.

Examples:

BPFProgram=egress:/sys/fs/bpf/egress-hook
BPFProgram=bind6:/sys/fs/bpf/sock-addr-hook

Optional. Type uniline.

SocketBindAllow
Allow or deny binding a socket address to a socket by matching it with the bind-rule and
applying a corresponding action if there is a match.

bind-rule describes socket properties such as address-family, transport-protocol and ip-
ports.

bind-rule := { [address-family":"][transport-protocol":"][ip-ports] | "any" }

address-family := { "ipv4" | "ipv6" }

transport-protocol := { "tcp" | "udp" }

ip-ports := { ip-port | ip-port-range }

An optional address-family expects "ipv4" or "ipv6" values. If not specified, a rule will
be matched for both IPv4 and IPv6 addresses and applied depending on other socket fields,
e.g. transport-protocol, ip-port.

An optional transport-protocol expects "tcp" or "udp" transport protocol names. If not
specified, a rule will be matched for any transport protocol.

An optional ip-port value must lie within 1X65535 interval inclusively, i.e. dynamic port
0 is not allowed. A range of sequential ports is described by ip-port-range := ip-port-
low"-"ip-port-high, where ip-port-low is smaller than or equal to ip-port-high and both
are within 1X65535 inclusively.

A special value "any" can be used to apply a rule to any address family, transport
protocol and any port with a positive value.

To allow multiple rules assign "SocketBindAllow" or "SocketBindDeny" multiple times. To
clear the existing assignments pass an empty "SocketBindAllow" or "SocketBindDeny"
assignment.

For each of "SocketBindAllow" and "SocketBindDeny", maximum allowed number of assignments
is 128.

The feature is implemented with "cgroup/bind4" and "cgroup/bind6" cgroup-bpf hooks.

Examples:
X
# Allow binding IPv6 socket addresses with a port greater than or equal to 10000.
[Service]
SocketBindAllow=ipv6:10000-65535
SocketBindDeny=any
X
# Allow binding IPv4 and IPv6 socket addresses with 1234 and 4321 ports.
[Service]
SocketBindAllow=1234
SocketBindAllow=4321
SocketBindDeny=any
X
# Deny binding IPv6 socket addresses.
[Service]
SocketBindDeny=ipv6
X
# Deny binding IPv4 and IPv6 socket addresses.
[Service]
SocketBindDeny=any
X
# Allow binding only over TCP
[Service]
SocketBindAllow=tcp
SocketBindDeny=any
X
# Allow binding only over IPv6/TCP
[Service]
SocketBindAllow=ipv6:tcp
SocketBindDeny=any
X
# Allow binding ports within 10000-65535 range over IPv4/UDP.
[Service]
SocketBindAllow=ipv4:udp:10000-65535
SocketBindDeny=any
X Optional. Type uniline.

SocketBindDeny
Allow or deny binding a socket address to a socket by matching it with the bind-rule and
applying a corresponding action if there is a match.

bind-rule describes socket properties such as address-family, transport-protocol and ip-
ports.

bind-rule := { [address-family":"][transport-protocol":"][ip-ports] | "any" }

address-family := { "ipv4" | "ipv6" }

transport-protocol := { "tcp" | "udp" }

ip-ports := { ip-port | ip-port-range }

An optional transport-protocol expects "tcp" or "udp" transport protocol names. If not
specified, a rule will be matched for any transport protocol.

A special value "any" can be used to apply a rule to any address family, transport
protocol and any port with a positive value.

To allow multiple rules assign "SocketBindAllow" or "SocketBindDeny" multiple times. To
clear the existing assignments pass an empty "SocketBindAllow" or "SocketBindDeny"
assignment.

For each of "SocketBindAllow" and "SocketBindDeny", maximum allowed number of assignments
is 128.

The feature is implemented with "cgroup/bind4" and "cgroup/bind6" cgroup-bpf hooks.

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

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

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

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

Example 1: allow-list

RestrictNetworkInterfaces=eth1
RestrictNetworkInterfaces=eth2

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

Example 2: deny-list

RestrictNetworkInterfaces=~eth1 eth2

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

Example 3: mixed

RestrictNetworkInterfaces=eth1 eth2
RestrictNetworkInterfaces=~eth1

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

DeviceAllow
Control access to specific device nodes by the executed processes. Takes two space-
separated strings: a device node specifier followed by a combination of "r", "w", "m" to
control reading, writing, or creation of the specific device node(s) by the unit (mknod),
respectively. On cgroup-v1 this controls the "devices.allow" control group attribute. For
details about this control group attribute, see Device Whitelist Controller
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/devices.html>. In the
unified cgroup hierarchy this functionality is implemented using eBPF filtering.

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

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

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

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

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

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

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

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

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

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

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

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
<https://systemd.io/CGROUP_DELEGATION>. Optional. Type uniline.

DisableControllers
Disables controllers from being enabled for a unit's children. If a controller listed is
already in use in its subtree, the controller will be removed from the subtree. This can
be used to avoid child units being able to implicitly or explicitly enable a controller.
Defaults to not disabling any controllers.

It may not be possible to successfully disable a controller if the unit or any child of
the unit in question delegates controllers to its children, as any delegated subtree of
the cgroup hierarchy is unmanaged by systemd.

Multiple controllers may be specified, separated by spaces. You may also pass
"DisableControllers" multiple times, in which case each new instance adds another
controller to disable. Passing "DisableControllers" by itself with no controller name
present resets the disabled controller list. Optional. Type uniline.

ManagedOOMSwap
Specifies how systemd-oomd.service(8) will act on this unit's cgroups. Defaults to "auto".

When set to "kill", the unit becomes a candidate for monitoring by systemd-oomd. If the
cgroup passes the limits set by oomd.conf(5) or the unit configuration, systemd-oomd will
select a descendant cgroup and send "SIGKILL" to all of the processes under it. You can
find more details on candidates and kill behavior at systemd-oomd.service(8) and
oomd.conf(5).

Setting either of these properties to "kill" will also result in "After" and "Wants"
dependencies on "systemd-oomd.service" unless "DefaultDependencies=no".

When set to "auto", systemd-oomd will not actively use this cgroup's data for monitoring
and detection. However, if an ancestor cgroup has one of these properties set to "kill", a
unit with "auto" can still be a candidate for systemd-oomd to terminate. Optional. Type
enum. choice: 'auto', 'kill'.

ManagedOOMMemoryPressure
Specifies how systemd-oomd.service(8) will act on this unit's cgroups. Defaults to "auto".

Setting either of these properties to "kill" will also result in "After" and "Wants"
dependencies on "systemd-oomd.service" unless "DefaultDependencies=no".

ManagedOOMMemoryPressureLimit
Overrides the default memory pressure limit set by oomd.conf(5) for this unit (cgroup).
Takes a percentage value between 0% and 100%, inclusive. This property is ignored unless
"ManagedOOMMemoryPressure""kill". Defaults to 0%, which means to use the default set by
oomd.conf(5). Optional. Type uniline.

ManagedOOMPreference
Allows deprioritizing or omitting this unit's cgroup as a candidate when systemd-oomd
needs to act. Requires support for extended attributes (see xattr(7)) in order to use
"avoid" or "omit". Additionally, systemd-oomd will ignore these extended attributes if the
unit's cgroup is not owned by the root user.

If this property is set to "avoid", the service manager will convey this to systemd-oomd,
which will only select this cgroup if there are no other viable candidates.

If this property is set to "omit", the service manager will convey this to systemd-oomd,
which will ignore this cgroup as a candidate and will not perform any actions on it.

It is recommended to use "avoid" and "omit" sparingly, as it can adversely affect systemd-
oomd's kill behavior. Also note that these extended attributes are not applied recursively
to cgroups under this unit's cgroup.

Defaults to "none" which means systemd-oomd will rank this unit's cgroup as defined in
systemd-oomd.service(8) and oomd.conf(5). Optional. Type enum. choice: 'none', 'avoid',
'omit'.

CPUShares
Assign the specified CPU time share weight to the processes executed. These options take
an integer value and control the "cpu.shares" control group attribute. The allowed range
is 2 to 262144. Defaults to 1024. For details about this control group attribute, see CFS
Scheduler <https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html>. The
available CPU time is split up among all units within one slice relative to their CPU time
share weight.

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

Implies "CPUAccounting=yes".

These settings are deprecated. Use "CPUWeight" and "StartupCPUWeight" instead. Optional.
Type integer.

upstream_default value :
1024

StartupCPUShares
Assign the specified CPU time share weight to the processes executed. These options take
an integer value and control the "cpu.shares" control group attribute. The allowed range
is 2 to 262144. Defaults to 1024. For details about this control group attribute, see CFS
Scheduler <https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html>. The
available CPU time is split up among all units within one slice relative to their CPU time
share weight.

Implies "CPUAccounting=yes".

These settings are deprecated. Use "CPUWeight" and "StartupCPUWeight" instead. Optional.
Type integer.

upstream_default value :
1024

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 "infinity", no
memory limit is applied. This controls the "memory.limit_in_bytes" control group
attribute. For details about this control group attribute, see Memory Resource Controller
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/memory.html>.

Implies "MemoryAccounting=yes".

This setting is deprecated. Use "MemoryMax" instead. Optional. Type uniline.

BlockIOAccounting
Turn on Block I/O accounting for this unit, if the legacy control group hierarchy is used
on the system. Takes a boolean argument. Note that turning on block I/O accounting for one
unit will also implicitly turn it on for all units contained in the same slice and all for
its parent slices and the units contained therein. The system default for this setting may
be controlled with "DefaultBlockIOAccounting" in systemd-system.conf(5).

This setting is deprecated. Use "IOAccounting" instead. Optional. Type boolean.

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 "blkio.weight" control group
attribute, which defaults to 500. For details about this control group attribute, see
Block IO Controller <https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-
controller.html>. The available I/O bandwidth is split up among all units within one
slice relative to their block I/O weight.

While "StartupBlockIOWeight" only applies to the startup and shutdown phases of the
system, "BlockIOWeight" applies to the later runtime of the system, and if the former is
not set also to the startup and shutdown phases. This allows prioritizing specific
services at boot-up and shutdown differently than during runtime.

Implies "BlockIOAccounting=yes".

These settings are deprecated. Use "IOWeight" and "StartupIOWeight" instead. Optional.
Type uniline.

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 "blkio.weight" control group
attribute, which defaults to 500. For details about this control group attribute, see
Block IO Controller <https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-
controller.html>. The available I/O bandwidth is split up among all units within one
slice relative to their block I/O weight.

Implies "BlockIOAccounting=yes".

These settings are deprecated. Use "IOWeight" and "StartupIOWeight" instead. Optional.
Type uniline.

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 "blkio.weight_device" control group attribute, which
defaults to 1000. Use this option multiple times to set weights for multiple devices. For
details about this control group attribute, see Block IO Controller
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html>.

Implies "BlockIOAccounting=yes".

This setting is deprecated. Use "IODeviceWeight" instead. Optional. Type uniline.

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
"blkio.throttle.read_bps_device" and "blkio.throttle.write_bps_device" control group
attributes. Use this option multiple times to set bandwidth limits for multiple devices.
For details about these control group attributes, see Block IO Controller
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html>.

Implies "BlockIOAccounting=yes".

These settings are deprecated. Use "IOReadBandwidthMax" and "IOWriteBandwidthMax" instead.
Optional. Type uniline.

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
"blkio.throttle.read_bps_device" and "blkio.throttle.write_bps_device" control group
attributes. Use this option multiple times to set bandwidth limits for multiple devices.
For details about these control group attributes, see Block IO Controller
<https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html>.

Implies "BlockIOAccounting=yes".

These settings are deprecated. Use "IOReadBandwidthMax" and "IOWriteBandwidthMax" instead.
Optional. Type uniline.

ExecSearchPath
Takes a colon separated list of absolute paths relative to which the executable used by
the "Exec*=" (e.g. "ExecStart", "ExecStop", etc.) properties can be found.
"ExecSearchPath" overrides $PATH if $PATH is not supplied by the user through
"Environment", "EnvironmentFile" or "PassEnvironment". Assigning an empty string removes
previous assignments and setting "ExecSearchPath" to a value multiple times will append to
the previous setting. Optional. Type list of uniline.

WorkingDirectory
Takes a directory path relative to the service's root directory specified by
"RootDirectory", or the special value "~". Sets the working directory for executed
processes. If set to "~", the home directory of the user specified in "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
"-" character, a missing working directory is not considered fatal. If
"RootDirectory"/"RootImage" is not set, then "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). Optional. Type uniline.

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
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 "MountAPIVFS" and "PrivateUsers" settings are particularly useful in conjunction with
"RootDirectory". For details, see below.

If "RootDirectory"/"RootImage" are used together with "NotifyAccess" the notification
socket is automatically mounted from the host into the root environment, to ensure the
notification interface can work correctly.

Note that services using "RootDirectory"/"RootImage" will not be able to log via the
syslog or journal protocols to the host logging infrastructure, unless the relevant
sockets are mounted from the host, specifically: Optional. Type uniline.

RootImage
Takes a path to a block device node or regular file as argument. This call is similar to
"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 <https://systemd.io/DISCOVERABLE_PARTITIONS>.

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

Units making use of "RootImage" automatically gain an "After" dependency on
"systemd-udevd.service". Optional. Type uniline.

RootImageOptions
Takes a comma-separated list of mount options that will be used on disk images specified
by "RootImage". Optionally a partition name can be prefixed, followed by colon, in case
the image has multiple partitions, otherwise partition name "root" is implied. Options
for multiple partitions can be specified in a single line with space separators. Assigning
an empty string removes previous assignments. Duplicated options are ignored. For a list
of valid mount options, please refer to mount(8).

Valid partition names follow the Discoverable Partitions Specification
<https://systemd.io/DISCOVERABLE_PARTITIONS>: "root", "usr", "home", "srv", "esp",
"xbootldr", "tmp", "var". Optional. Type uniline.

RootHash
Takes a data integrity (dm-verity) root hash specified in hexadecimal, or the path to a
file containing a root hash in ASCII hexadecimal format. This option enables data
integrity checks using dm-verity, if the used image contains the appropriate integrity
data (see above) or if "RootVerity" is used. The specified hash must match the root hash
of integrity data, and is usually at least 256 bits (and hence 64 formatted hexadecimal
characters) long (in case of SHA256 for example). If this option is not specified, but the
image file carries the "user.verity.roothash" extended file attribute (see xattr(7)), then
the root hash is read from it, also as formatted hexadecimal characters. If the extended
file attribute is not found (or is not supported by the underlying file system), but a
file with the ".roothash" suffix is found next to the image file, bearing otherwise the
same name (except if the image has the ".raw" suffix, in which case the root hash file
must not have it in its name), the root hash is read from it and automatically used, also
as formatted hexadecimal characters.

If the disk image contains a separate "/usr/" partition it may also be Verity protected,
in which case the root hash may configured via an extended attribute "user.verity.usrhash"
or a ".usrhash" file adjacent to the disk image. There's currently no option to configure
the root hash for the "/usr/" file system via the unit file directly. Optional. Type
uniline.

RootHashSignature
Takes a PKCS7 signature of the "RootHash" option as a path to a DER-encoded signature
file, or as an ASCII base64 string encoding of a DER-encoded signature prefixed by
"base64:". The dm-verity volume will only be opened if the signature of the root hash is
valid and signed by a public key present in the kernel keyring. If this option is not
specified, but a file with the ".roothash.p7s" suffix is found next to the image file,
bearing otherwise the same name (except if the image has the ".raw" suffix, in which case
the signature file must not have it in its name), the signature is read from it and
automatically used.

If the disk image contains a separate "/usr/" partition it may also be Verity protected,
in which case the signature for the root hash may configured via a ".usrhash.p7s" file
adjacent to the disk image. There's currently no option to configure the root hash
signature for the "/usr/" via the unit file directly. Optional. Type uniline.

RootVerity
Takes the path to a data integrity (dm-verity) file. This option enables data integrity
checks using dm-verity, if "RootImage" is used and a root-hash is passed and if the used
image itself does not contains the integrity data. The integrity data must be matched by
the root hash. If this option is not specified, but a file with the ".verity" suffix is
found next to the image file, bearing otherwise the same name (except if the image has the
".raw" suffix, in which case the verity data file must not have it in its name), the
verity data is read from it and automatically used.

This option is supported only for disk images that contain a single file system, without
an enveloping partition table. Images that contain a GPT partition table should instead
include both root file system and matching Verity data in the same image, implementing the
Discoverable Partitions Specification <https://systemd.io/DISCOVERABLE_PARTITIONS>.
Optional. Type uniline.

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/", "/dev/" and "/run/" (as an empty
"tmpfs") are mounted inside of it, unless they are already mounted. Note that this option
has no effect unless used in conjunction with "RootDirectory"/"RootImage" as these four
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 four
mounts. Note that the "/dev/" file system of the host is bind mounted if this option is
used without "PrivateDevices". To run the service with a private, minimal version of
"/dev/", combine this option with "PrivateDevices".

In order to allow propagating mounts at runtime in a safe manner, "/run/systemd/propagate"
on the host will be used to set up new mounts, and "/run/host/incoming/" in the private
namespace will be used as an intermediate step to store them before being moved to the
final mount point. Optional. Type boolean.

ProtectProc
Takes one of "noaccess", "invisible", "ptraceable" or "default" (which it defaults to).
When set, this controls the "hidepid=" mount option of the "procfs" instance for the unit
that controls which directories with process metainformation ("/proc/PID") are visible and
accessible: when set to "noaccess" the ability to access most of other users' process
metadata in "/proc/" is taken away for processes of the service. When set to "invisible"
processes owned by other users are hidden from "/proc/". If "ptraceable" all processes
that cannot be ptrace()'ed by a process are hidden to it. If "default" no restrictions on
"/proc/" access or visibility are made. For further details see The /proc Filesystem
<https://www.kernel.org/doc/html/latest/filesystems/proc.html#mount-options>. It is
generally recommended to run most system services with this option set to "invisible".
This option is implemented via file system namespacing, and thus cannot be used with
services that shall be able to install mount points in the host file system hierarchy.
Note that the root user is unaffected by this option, so to be effective it has to be used
together with "User" or "DynamicUser=yes", and also without the "CAP_SYS_PTRACE"
capability, which also allows a process to bypass this feature. It cannot be used for
services that need to access metainformation about other users' processes. This option
implies "MountAPIVFS".

If the kernel doesn't support per-mount point "hidepid=" mount options this setting
remains without effect, and the unit's processes will be able to access and see other
process as if the option was not used. Optional. Type enum. choice: 'noaccess',
'invisible', 'ptraceable', 'default'.

ProcSubset
Takes one of "all" (the default) and "pid". If "pid", all files and directories not
directly associated with process management and introspection are made invisible in the
"/proc/" file system configured for the unit's processes. This controls the "subset="
mount option of the "procfs" instance for the unit. For further details see The /proc
Filesystem <https://www.kernel.org/doc/html/latest/filesystems/proc.html#mount-options>.
Note that Linux exposes various kernel APIs via "/proc/", which are made unavailable with
this setting. Since these APIs are used frequently this option is useful only in a few,
specific cases, and is not suitable for most non-trivial programs.

Much like "ProtectProc" above, this is implemented via file system mount namespacing, and
hence the same restrictions apply: it is only available to system services, it disables
mount propagation to the host mount table, and it implies "MountAPIVFS". Also, like
"ProtectProc" this setting is gracefully disabled if the used kernel does not support the
"subset=" mount option of "procfs". Optional. Type enum. choice: 'all', 'pid'.

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 "rbind" or
"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 "-", in which case it will be ignored when its source path does not exist.

"BindPaths" creates regular writable bind mounts (unless the source file system mount is
already marked read-only), while "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 "RootDirectory"/"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.

Note that the destination directory must exist or systemd must be able to create it.
Thus, it is not possible to use those options for mount points nested underneath paths
specified in "InaccessiblePaths", or under "/home/" and other protected directories if
"ProtectHome=yes" is specified. "TemporaryFileSystem" with ":ro" or "ProtectHome=tmpfs"
should be used instead. Optional. Type list of uniline.

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 "rbind" or
"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 "-", in which case it will be ignored when its source path does not exist.

MountImages
This setting is similar to "RootImage" in that it mounts a file system hierarchy from a
block device node or loopback file, but the destination directory can be specified as well
as mount options. This option expects a whitespace separated list of mount definitions.
Each definition consists of a colon-separated tuple of source path and destination
definitions, optionally followed by another colon and a list of mount options.

Mount options may be defined as a single comma-separated list of options, in which case
they will be implicitly applied to the root partition on the image, or a series of colon-
separated tuples of partition name and mount options. Valid partition names and mount
options are the same as for "RootImageOptions" setting described above.

Each mount definition may be prefixed with "-", in which case it will be ignored when its
source path does not exist. The source argument is a path to a block device node or
regular file. If source or destination contain a ":", it needs to be escaped as "\:". The
device node or file system image file needs to follow the same rules as specified for
"RootImage". Any mounts created with this option are specific to the unit, and are not
visible in the host's mount table.

These settings may be used more than once, each usage appends to the unit's list of mount
paths. If the empty string is assigned, the entire list of mount paths defined prior to
this is reset.

ExtensionImages
This setting is similar to "MountImages" in that it mounts a file system hierarchy from a
block device node or loopback file, but instead of providing a destination path, an
overlay will be set up. This option expects a whitespace separated list of mount
definitions. Each definition consists of a source path, optionally followed by a colon and
a list of mount options.

A read-only OverlayFS will be set up on top of "/usr/" and "/opt/" hierarchies. The order
in which the images are listed will determine the order in which the overlay is laid down:
images specified first to last will result in overlayfs layers bottom to top.

Each mount definition may be prefixed with "-", in which case it will be ignored when its
source path does not exist. The source argument is a path to a block device node or
regular file. If the source path contains a ":", it needs to be escaped as "\:". The
device node or file system image file needs to follow the same rules as specified for
"RootImage". Any mounts created with this option are specific to the unit, and are not
visible in the host's mount table.

These settings may be used more than once, each usage appends to the unit's list of image
paths. If the empty string is assigned, the entire list of mount paths defined prior to
this is reset.

Each image must carry a "/usr/lib/extension-release.d/extension-release.IMAGE" file, with
the appropriate metadata which matches "RootImage"/"RootDirectory" or the host. See:
os-release(5).

ExtensionDirectories
This setting is similar to "BindReadOnlyPaths" in that it mounts a file system hierarchy
from a directory, but instead of providing a destination path, an overlay will be set up.
This option expects a whitespace separated list of source directories.

A read-only OverlayFS will be set up on top of "/usr/" and "/opt/" hierarchies. The order
in which the directories are listed will determine the order in which the overlay is laid
down: directories specified first to last will result in overlayfs layers bottom to top.

Each directory listed in "ExtensionDirectories" may be prefixed with "-", in which case it
will be ignored when its source path does not exist. Any mounts created with this option
are specific to the unit, and are not visible in the host's mount table.

These settings may be used more than once, each usage appends to the unit's list of
directories paths. If the empty string is assigned, the entire list of mount paths defined
prior to this is reset.

Each directory must contain a "/usr/lib/extension-release.d/extension-release.IMAGE" file,
with the appropriate metadata which matches "RootImage"/"RootDirectory" or the host. See:
os-release(5).

Note that usage from user units requires overlayfs support in unprivileged user
namespaces, which was first introduced in kernel v5.11. Optional. Type list of uniline.

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 "root", but
"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
"+".

Note that this enforces only weak restrictions on the user/group name syntax, but will
generate warnings in many cases where user/group names do not adhere to the following
rules: the specified name should consist only of the characters a-z, A-Z, 0-9, "_" and
"-", except for the first character which must be one of a-z, A-Z and "_" (i.e. digits and
"-" are not permitted as first character). The user/group name must have at least one
character, and at most 31. These restrictions are made in order to avoid ambiguities and
to ensure user/group names and unit files remain portable among Linux systems. For further
details on the names accepted and the names warned about see User/Group Name Syntax
<https://systemd.io/USER_NAMES>.

When used in conjunction with "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 X unless it is already allocated statically (see below). If "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 sysusers.d(5)
facility, which is applied at boot or package install time. If the user does not exist by
then program invocation will fail.

If the "User" setting is used the supplementary group list is initialized from the
specified user's default group list, as defined in the system's user and group database.
Additional groups may be configured through the "SupplementaryGroups" setting (see below).
Optional. Type uniline.

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 "root", but
"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
"+".

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 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 "User" and "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 "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 "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 61184X65519. 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
"DynamicUser" is enabled, "RemoveIPC" and "PrivateTmp" are implied (and cannot be turned
off). 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. Furthermore "NoNewPrivileges"
and "RestrictSUIDSGID" are implicitly enabled (and cannot be disabled), to ensure that
processes invoked cannot take benefit or create SUID/SGID files or directories. Moreover
"ProtectSystem=strict" and "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 allow-listed using "ReadWritePaths", but
care must be taken so that UID/GID recycling doesn't create security issues involving
files created by the service. Use "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 "StateDirectory", "CacheDirectory" and
"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). If this option is enabled, care should be taken that the unit's processes do not
get access to directories outside of these explicitly configured and managed ones.
Specifically, do not use "BindPaths" and be careful with "AF_UNIX" file descriptor passing
for directory file descriptors, as this would permit processes to create files or
directories owned by the dynamic user/group that are not subject to the lifecycle and
access guarantees of the service. Defaults to off. Optional. Type boolean.

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 "+". Optional. Type list of uniline.

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 "User" setting, and is otherwise ignored. If not set, no PAM session
will be opened for the executed processes. See 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 "(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 "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
"NotifyAccess""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
"PAMName" in combination with "NotifyAccess""all". Optional. Type uniline.

CapabilityBoundingSet
Controls which capabilities to include in the capability bounding set for the executed
process. See capabilities(7) for details. Takes a whitespace-separated list of capability
names, e.g. "CAP_SYS_ADMIN", "CAP_DAC_OVERRIDE", "CAP_SYS_PTRACE". Capabilities listed
will be included in the bounding set, all others are removed. If the list of capabilities
is prefixed with "~", 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 "OR", or by "AND" if the lines are prefixed with "~"
(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 "~" (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 "+".

Use systemd-analyze(1)'s capability command to retrieve a list of capabilities defined on
the local system.

Example: if a unit has the following,

CapabilityBoundingSet=CAP_A CAP_B
CapabilityBoundingSet=CAP_B CAP_C

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

CapabilityBoundingSet=CAP_A CAP_B
CapabilityBoundingSet=~CAP_B CAP_C

then, only "CAP_A" is set. Optional. Type uniline.

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. "CAP_SYS_ADMIN",
"CAP_DAC_OVERRIDE", "CAP_SYS_PTRACE". This option may appear more than once in which case
the ambient capability sets are merged (see the above examples in
"CapabilityBoundingSet"). If the list of capabilities is prefixed with "~", 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 "~" (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
"keep-caps" is automatically added to "SecureBits" to retain the capabilities over the
user change. "AmbientCapabilities" does not affect commands prefixed with "+". Optional.
Type uniline.

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 "DynamicUser", "LockPersonality", "MemoryDenyWriteExecute", "PrivateDevices",
"ProtectClock", "ProtectHostname", "ProtectKernelLogs", "ProtectKernelModules",
"ProtectKernelTunables", "RestrictAddressFamilies", "RestrictNamespaces",
"RestrictRealtime", "RestrictSUIDSGID", "SystemCallArchitectures", "SystemCallFilter", or
"SystemCallLog" are specified. Note that even if this setting is overridden by them,
systemctl show shows the original value of this setting. In case the service will be run
in a new mount namespace anyway and SELinux is disabled, all file systems are mounted with
"MS_NOSUID" flag. Also see No New Privileges Flag
<https://www.kernel.org/doc/html/latest/userspace-api/no_new_privs.html>. Optional. Type
boolean.

SecureBits
Controls the secure bits set for the executed process. Takes a space-separated combination
of options from the following list: "keep-caps", "keep-caps-locked", "no-setuid-fixup",
"no-setuid-fixup-locked", "noroot", and "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 "+". See
capabilities(7) for details. Optional. Type uniline.

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 "-", failing to set the
SELinux security context will be ignored, but it's still possible that the subsequent
execve() may fail if the policy doesn't allow the transition for the non-overridden
context. This does not affect commands prefixed with "+". See setexeccon(3) for details.
Optional. Type uniline.

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. If prefixed by "-", all errors will be ignored. This setting has no effect if
AppArmor is not enabled. This setting does not affect commands prefixed with "+".
Optional. Type uniline.

SmackProcessLabel
Takes a "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 "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 "-", 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 "+". Optional. Type uniline.

LimitCPU
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (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
"LimitRSS" is not implemented on Linux, and setting it has no effect. Often it is
advisable to prefer the resource controls listed in 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, "MemoryMax" is a more powerful
(and working) replacement for "LimitRSS".

Note that "LimitNPROC" will limit the number of processes from one (real) UID and not the
number of processes started (forked) by the service. Therefore the limit is cumulative for
all processes running under the same UID. Please also note that the "LimitNPROC" will not
be enforced if the service is running as root (and not dropping privileges). Due to these
limitations, "TasksMax" (see systemd.resource-control(5)) is typically a better choice
than "LimitNPROC".

Resource limits not configured explicitly for a unit default to the value configured in
the various "DefaultLimitCPU", "DefaultLimitFSIZE", X options available in
systemd-system.conf(5), and X if not configured there X the kernel or per-user defaults,
as defined by the OS (the latter only for user services, see below).

For system units these resource limits may be chosen freely. When these settings are
configured in a user service (i.e. a service run by the per-user instance of the service
manager) they cannot be used to raise the limits above those set for the user manager
itself when it was first invoked, as the user's service manager generally lacks the
privileges to do so. In user context these configuration options are hence only useful to
lower the limits passed in or to raise the soft limit to the maximum of the hard limit as
configured for the user. To raise the user's limits further, the available configuration
mechanisms differ between operating systems, but typically require privileges. In most
cases it is possible to configure higher per-user resource limits via PAM or by setting
limits on the system service encapsulating the user's service manager, i.e. the user's
instance of "user@.service". After making such changes, make sure to restart the user's
service manager. Optional. Type uniline.

LimitFSIZE
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitDATA
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitSTACK
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitCORE
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitRSS
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitNOFILE
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitAS
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitNPROC
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitMEMLOCK
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitLOCKS
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitSIGPENDING
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitMSGQUEUE
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitNICE
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitRTPRIO
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

LimitRTTIME
Set soft and hard limits on various resources for executed processes. See 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 "soft:hard" to set both limits individually (e.g. "LimitAS=4G:16G").
Use the string "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 systemd.time(7) for details). Note that if
no time unit is specified for "LimitCPU" the default unit of seconds is implied, while for
"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 "LimitCPU" will be rounded up implicitly to multiples of 1s. For "LimitNICE"
the value may be specified in two syntaxes: if prefixed with "+" or "-", the value is
understood as regular Linux nice value in the range -20X19. If not prefixed like this the
value is understood as raw resource limit parameter in the range 0X40 (with 0 being
equivalent to 1).

UMask
Controls the file mode creation mask. Takes an access mode in octal notation. See umask(2)
for details. Defaults to 0022 for system units. For user units the default value is
inherited from the per-user service manager (whose default is in turn inherited from the
system service manager, and thus typically also is 0022 X unless overridden by a PAM
module). In order to change the per-user mask for all user services, consider setting the
"UMask" setting of the user's "user@.service" system service instance. The per-user umask
may also be set via the "umask" field of a user's JSON User Record
<https://systemd.io/USER_RECORD> (for users managed by systemd-homed.service(8) this field
may be controlled via homectl --umask=). It may also be set via a PAM module, such as
pam_umask(8). Optional. Type uniline.

CoredumpFilter
Controls which types of memory mappings will be saved if the process dumps core (using the
"/proc/pid/coredump_filter" file). Takes a whitespace-separated combination of mapping
type names or numbers (with the default base 16). Mapping type names are
"private-anonymous", "shared-anonymous", "private-file-backed", "shared-file-backed",
"elf-headers", "private-huge", "shared-huge", "private-dax", "shared-dax", and the special
values "all" (all types) and "default" (the kernel default of
""private-anonymous""shared-anonymous" "elf-headers""private-huge""). See core(5) for the
meaning of the mapping types. When specified multiple times, all specified masks are ORed.
When not set, or if the empty value is assigned, the inherited value is not changed.
Optional. Type uniline.

KeyringMode
Controls how the kernel session keyring is set up for the service (see session-keyring(7)
for details on the session keyring). Takes one of "inherit", "private", "shared". If set
to "inherit" no special keyring setup is done, and the kernel's default behaviour is
applied. If "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
"shared" is used a new session keyring is allocated as for "private", but the user keyring
of the user configured with "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 "inherit" is selected the unique
invocation ID for the unit (see below) is added as a protected key by the name
"invocation_id" to the newly created session keyring. Defaults to "private" for services
of the system service manager and to "inherit" for non-service units and for services of
the user service manager. Optional. Type enum. choice: 'inherit', 'private', 'shared'.

OOMScoreAdjust
Sets the adjustment value for the Linux kernel's Out-Of-Memory (OOM) killer score for
executed processes. Takes an integer between -1000 (to disable OOM killing of processes of
this unit) and 1000 (to make killing of processes of this unit under memory pressure very
likely). See proc.txt <https://www.kernel.org/doc/Documentation/filesystems/proc.txt> for
details. If not specified defaults to the OOM score adjustment level of the service
manager itself, which is normally at 0.

Use the "OOMPolicy" setting of service units to configure how the service manager shall
react to the kernel OOM killer or systemd-oomd terminating a process of the service. See
systemd.service(5) for details. Optional. Type integer.

TimerSlackNSec
Sets the timer slack in nanoseconds for the executed processes. The timer slack controls
the accuracy of wake-ups triggered by timers. See 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. Optional.
Type uniline.

Personality
Controls which kernel architecture uname(2) shall report, when invoked by unit processes.
Takes one of the architecture identifiers "x86", "x86-64", "ppc", "ppc-le", "ppc64",
"ppc64-le", "s390" or "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, "x86-64" systems support the "x86-64" and "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. Optional. Type enum. choice: 'x86', 'x86-64', 'ppc', 'ppc-le',
'ppc64', 'ppc64-le', 's390', 's390x'.

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

Nice
Sets the default nice level (scheduling priority) for executed processes. Takes an integer
between -20 (highest priority) and 19 (lowest priority). In case of resource contention,
smaller values mean more resources will be made available to the unit's processes, larger
values mean less resources will be made available. See setpriority(2) for details.
Optional. Type integer.

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

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. In
case of CPU resource contention, smaller values mean less CPU time is made available to
the service, larger values mean more. See sched_setscheduler(2) for details. Optional.
Type uniline.

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

CPUAffinity
Controls the CPU affinity of the executed processes. Takes a list of CPU indices or ranges
separated by either whitespace or commas. Alternatively, takes a special "numa" value in
which case systemd automatically derives allowed CPU range based on the value of
"NUMAMask" option. 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 sched_setaffinity(2) for details.
Optional. Type list of uniline.

NUMAPolicy
Controls the NUMA memory policy of the executed processes. Takes a policy type, one of:
"default", "preferred", "bind", "interleave" and "local". A list of NUMA nodes that should
be associated with the policy must be specified in "NUMAMask". For more details on each
policy please see, set_mempolicy(2). For overall overview of NUMA support in Linux see,
numa(7). Optional. Type uniline.

NUMAMask
Controls the NUMA node list which will be applied alongside with selected NUMA policy.
Takes a list of NUMA nodes and has the same syntax as a list of CPUs for "CPUAffinity"
option or special "all" value which will include all available NUMA nodes in the mask.
Note that the list of NUMA nodes is not required for "default" and "local" policies and
for "preferred" policy we expect a single NUMA node. Optional. Type uniline.

IOSchedulingClass
Sets the I/O scheduling class for executed processes. Takes one of the strings "realtime",
"best-effort" or "idle". The kernel's default scheduling class is "best-effort" at a
priority of 4. If the empty string is assigned to this option, all prior assignments to
both "IOSchedulingClass" and "IOSchedulingPriority" have no effect. See ioprio_set(2) for
details. Optional. Type enum. choice: '0', '1', '2', '3', 'none', 'realtime',
'best-effort', 'idle'.

IOSchedulingPriority
Sets the I/O scheduling priority for executed processes. Takes an integer between 0
(highest priority) and 7 (lowest priority). In case of I/O contention, smaller values mean
more I/O bandwidth is made available to the unit's processes, larger values mean less
bandwidth. 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
"IOSchedulingClass" and "IOSchedulingPriority" have no effect. For the kernel's default
scheduling class ("best-effort") this defaults to 4. See ioprio_set(2) for details.
Optional. Type integer.

upstream_default value :
4

ProtectSystem
Takes a boolean argument or the special values "full" or "strict". If true, mounts the
"/usr/" and the boot loader directories ("/boot" and "/efi") read-only for processes
invoked by this unit. If set to "full", the "/etc/" directory is mounted read-only, too.
If set to "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
"PrivateDevices", "ProtectKernelTunables", "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,
"ReadWritePaths" may be used to exclude specific directories from being made read-only.
This setting is implied if "DynamicUser" is set. This setting cannot ensure protection in
all cases. In general it has the same limitations as "ReadOnlyPaths", see below. Defaults
to off. Optional. Type enum. choice: 'no', 'yes', 'full', 'strict'.

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

Setting this to "yes" is mostly equivalent to set the three directories in
"InaccessiblePaths". Similarly, "read-only" is mostly equivalent to "ReadOnlyPaths", and
"tmpfs" is mostly equivalent to "TemporaryFileSystem" with ":ro".

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
"DynamicUser" is set. This setting cannot ensure protection in all cases. In general it
has the same limitations as "ReadOnlyPaths", see below. Optional. Type enum. choice:
'no', 'yes', 'read-only', 'tmpfs'.

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

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

Except in case of "ConfigurationDirectory", the innermost specified directories will be
owned by the user and group specified in "User" and "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 "RuntimeDirectoryMode", "StateDirectoryMode", "CacheDirectoryMode",
"LogsDirectoryMode" and "ConfigurationDirectoryMode".

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

If "DynamicUser" is used, the logic for "CacheDirectory", "LogsDirectory" and
"StateDirectory" is slightly altered: the directories are created below
"/var/cache/private", "/var/log/private" and "/var/lib/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/cache",
"/var/log" and "/var/lib".

Use "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 tmpfiles.d(5).

"RuntimeDirectory", "StateDirectory", "CacheDirectory" and "LogsDirectory" optionally
support a second parameter, separated by ":". The second parameter will be interpreted as
a destination path that will be created as a symlink to the directory. The symlinks will
be created after any "BindPaths" or "TemporaryFileSystem" options have been set up, to
make ephemeral symlinking possible. The same source can have multiple symlinks, by using
the same first parameter, but a different second parameter. Optional. Type uniline.

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

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

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

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

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

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

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

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

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

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

TimeoutCleanSec
Configures a timeout on the clean-up operation requested through systemctl clean X, see
systemctl(1) for details. Takes the usual time values and defaults to "infinity", i.e. by
default no timeout is applied. If a timeout is configured the clean operation will be
aborted forcibly when the timeout is reached, potentially leaving resources on disk.
Optional. Type uniline.

ReadWritePaths
Sets up a new file system namespace for executed processes. These options may be used to
limit access a process has to the file system. 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 "RootDirectory"/"RootImage".

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

Paths listed in "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 "ReadWritePaths",
"ReadOnlyPaths", "BindPaths", or "BindReadOnlyPaths" inside it. For a more flexible
option, see "TemporaryFileSystem".

Content in paths listed in "NoExecPaths" are not executable even if the usual file access
controls would permit this. Nest "ExecPaths" inside of "NoExecPaths" in order to provide
executable content within non-executable directories.

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 "ReadWritePaths", "ReadOnlyPaths", "InaccessiblePaths", "ExecPaths" and
"NoExecPaths" may be prefixed with "-", in which case they will be ignored when they do
not exist. If prefixed with "+" the paths are taken relative to the root directory of the
unit, as configured with "RootDirectory"/"RootImage", instead of relative to the root
directory of the host (see above). When combining "-" and "+" on the same path make sure
to specify "-" first, and "+" 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 "ReadWritePaths" and
"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 "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 "CapabilityBoundingSet=~CAP_SYS_ADMIN" or
"SystemCallFilter=~@mount".

Simple allow-list example using these directives:

[Service]
ReadOnlyPaths=/
ReadWritePaths=/var /run
InaccessiblePaths=-/lost+found
NoExecPaths=/
ExecPaths=/usr/sbin/my_daemon /usr/lib /usr/lib64

Optional. Type list of uniline.

ReadOnlyPaths
Sets up a new file system namespace for executed processes. These options may be used to
limit access a process has to the file system. 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 "RootDirectory"/"RootImage".

Simple allow-list example using these directives:

[Service]
ReadOnlyPaths=/
ReadWritePaths=/var /run
InaccessiblePaths=-/lost+found
NoExecPaths=/
ExecPaths=/usr/sbin/my_daemon /usr/lib /usr/lib64

Optional. Type list of uniline.

InaccessiblePaths
Sets up a new file system namespace for executed processes. These options may be used to
limit access a process has to the file system. 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 "RootDirectory"/"RootImage".

Simple allow-list example using these directives:

[Service]
ReadOnlyPaths=/
ReadWritePaths=/var /run
InaccessiblePaths=-/lost+found
NoExecPaths=/
ExecPaths=/usr/sbin/my_daemon /usr/lib /usr/lib64

Optional. Type list of uniline.

ExecPaths
Sets up a new file system namespace for executed processes. These options may be used to
limit access a process has to the file system. 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 "RootDirectory"/"RootImage".

Simple allow-list example using these directives:

[Service]
ReadOnlyPaths=/
ReadWritePaths=/var /run
InaccessiblePaths=-/lost+found
NoExecPaths=/
ExecPaths=/usr/sbin/my_daemon /usr/lib /usr/lib64

Optional. Type list of uniline.

NoExecPaths
Sets up a new file system namespace for executed processes. These options may be used to
limit access a process has to the file system. 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 "RootDirectory"/"RootImage".

Simple allow-list example using these directives:

[Service]
ReadOnlyPaths=/
ReadWritePaths=/var /run
InaccessiblePaths=-/lost+found
NoExecPaths=/
ExecPaths=/usr/sbin/my_daemon /usr/lib /usr/lib64

Optional. Type list of uniline.

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 (":") and mount options such as
"size=10%" or "ro". By default, each temporary file system is mounted with
"nodev,strictatime,mode=0755". These can be disabled by explicitly specifying the
corresponding mount options, e.g., "dev" or "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
"BindPaths" or "BindReadOnlyPaths":

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. Optional. Type list of uniline.

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 are 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 true, 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
"JoinsNamespaceOf" directive, see systemd.unit(5) for details. This setting is implied if
"DynamicUser" is set. For this setting the same restrictions regarding mount propagation
and privileges apply as for "ReadOnlyPaths" and related calls, see above. Enabling this
setting has the side effect of adding "Requires" and "After" dependencies on all mount
units necessary to access "/tmp/" and "/var/tmp/". Moreover an implicitly "After" ordering
on 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. Optional. Type boolean.

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 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 "@raw-io" set, remove "CAP_MKNOD" and "CAP_SYS_RAWIO" from the
capability bounding set for the unit, and set "DevicePolicy=closed" (see
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 mmap(2) of "/dev/zero" instead of using "MAP_ANON". For this
setting the same restrictions regarding mount propagation and privileges apply as for
"ReadOnlyPaths" and related calls, see above. If turned on and if running in user mode, or
in system mode, but without the "CAP_SYS_ADMIN" capability (e.g. setting "User"),
"NoNewPrivileges=yes" is implied.

When access to some but not all devices must be possible, the "DeviceAllow" setting might
be used instead. See systemd.resource-control(5). Optional. Type boolean.

PrivateNetwork
Takes a boolean argument. If true, sets up a new network namespace for the executed
processes and configures only the loopback network device "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 "JoinsNamespaceOf" directive,
see systemd.unit(5) for details. Note that this option will disconnect all socket families
from the host, including "AF_NETLINK" and "AF_UNIX". Effectively, for "AF_NETLINK" this
means that device configuration events received from systemd-udevd.service(8) are not
delivered to the unit's processes. And for "AF_UNIX" this has the effect that "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.

When this option is used on a socket unit any sockets bound on behalf of this unit will be
bound within a private network namespace. This may be combined with "JoinsNamespaceOf" to
listen on sockets inside of network namespaces of other services. Optional. Type boolean.

NetworkNamespacePath
Takes an absolute file system path refererring to a Linux network namespace pseudo-file
(i.e. a file like "/proc/$PID/ns/net" or a bind mount or symlink to one). When set the
invoked processes are added to the network namespace referenced by that path. The path has
to point to a valid namespace file at the moment the processes are forked off. If this
option is used "PrivateNetwork" has no effect. If this option is used together with
"JoinsNamespaceOf" then it only has an effect if this unit is started before any of the
listed units that have "PrivateNetwork" or "NetworkNamespacePath" configured, as otherwise
the network namespace of those units is reused.

When this option is used on a socket unit any sockets bound on behalf of this unit will be
bound within the specified network namespace. Optional. Type uniline.

PrivateIPC
Takes a boolean argument. If true, sets up a new IPC namespace for the executed processes.
Each IPC namespace has its own set of System V IPC identifiers and its own POSIX message
queue file system. This is useful to avoid name clash of IPC identifiers. Defaults to
false. It is possible to run two or more units within the same private IPC namespace by
using the "JoinsNamespaceOf" directive, see systemd.unit(5) for details.

Note that IPC namespacing does not have an effect on "AF_UNIX" sockets, which are the most
common form of IPC used on Linux. Instead, "AF_UNIX" sockets in the file system are
subject to mount namespacing, and those in the abstract namespace are subject to network
namespacing. IPC namespacing only has an effect on SysV IPC (which is mostly legacy) as
well as POSIX message queues (for which "AF_UNIX"/"SOCK_SEQPACKET" sockets are typically a
better replacement). IPC namespacing also has no effect on POSIX shared memory (which is
subject to mount namespacing) either. See ipc_namespaces(7) for the details.

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

IPCNamespacePath
Takes an absolute file system path refererring to a Linux IPC namespace pseudo-file (i.e.
a file like "/proc/$PID/ns/ipc" or a bind mount or symlink to one). When set the invoked
processes are added to the network namespace referenced by that path. The path has to
point to a valid namespace file at the moment the processes are forked off. If this option
is used "PrivateIPC" has no effect. If this option is used together with
"JoinsNamespaceOf" then it only has an effect if this unit is started before any of the
listed units that have "PrivateIPC" or "IPCNamespacePath" configured, as otherwise the
network namespace of those units is reused. Optional. Type uniline.

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 "root" user and group as
well as the unit's own user and group to themselves and everything else to the "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 "root" or the unit's own will stay visible from within the unit but appear owned
by the "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
"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 "CapabilityBoundingSet" will affect only the latter, and
there's no way to acquire additional capabilities in the host's user namespace. Defaults
to off.

When this setting is set up by a per-user instance of the service manager, the mapping of
the "root" user and group to itself is omitted (unless the user manager is root).
Additionally, in the per-user instance manager case, the user namespace will be set up
before most other namespaces. This means that combining "PrivateUsers""true" with other
namespaces will enable use of features not normally supported by the per-user instances of
the service manager.

This setting is particularly useful in conjunction with "RootDirectory"/"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 "root", "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. Optional. Type boolean.

ProtectHostname
Takes a boolean argument. When set, sets up a new UTS namespace for the executed
processes. In addition, changing hostname or domainname is prevented. Defaults to off.

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

Note that when this option is enabled for a service hostname changes no longer propagate
from the system into the service, it is hence not suitable for services that need to take
notice of system hostname changes dynamically.

If this setting is on, but the unit doesn't have the "CAP_SYS_ADMIN" capability (e.g.
services for which "User" is set), "NoNewPrivileges=yes" is implied. Optional. Type
boolean.

ProtectClock
Takes a boolean argument. If set, writes to the hardware clock or system clock will be
denied. It is recommended to turn this on for most services that do not need modify the
clock. Defaults to off. Enabling this option removes "CAP_SYS_TIME" and "CAP_WAKE_ALARM"
from the capability bounding set for this unit, installs a system call filter to block
calls that can set the clock, and "DeviceAllow=char-rtc r" is implied. This ensures
"/dev/rtc0", "/dev/rtc1", etc. are made read-only to the service. See
systemd.resource-control(5) for the details about "DeviceAllow". If this setting is on,
but the unit doesn't have the "CAP_SYS_ADMIN" capability (e.g. services for which "User"
is set), "NoNewPrivileges=yes" is implied. Optional. Type boolean.

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
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 "ReadOnlyPaths" and related calls,
see above. Defaults to off. If this setting is on, but the unit doesn't have the
"CAP_SYS_ADMIN" capability (e.g. services for which "User" is set), "NoNewPrivileges=yes"
is implied. Note that this option does not prevent indirect changes to kernel tunables
effected by IPC calls to other processes. However, "InaccessiblePaths" may be used to make
relevant IPC file system objects inaccessible. If "ProtectKernelTunables" is set,
"MountAPIVFS=yes" is implied. Optional. Type boolean.

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 "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 "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 sysctl.d(5)"kernel.modules_disabled" mechanism and "/proc/sys/kernel/modules_disabled"
documentation. If this setting is on, but the unit doesn't have the "CAP_SYS_ADMIN"
capability (e.g. services for which "User" is set), "NoNewPrivileges=yes" is implied.
Optional. Type boolean.

ProtectKernelLogs
Takes a boolean argument. If true, access to the kernel log ring buffer will be denied. It
is recommended to turn this on for most services that do not need to read from or write to
the kernel log ring buffer. Enabling this option removes "CAP_SYSLOG" from the capability
bounding set for this unit, and installs a system call filter to block the syslog(2)
system call (not to be confused with the libc API syslog(3) for userspace logging). The
kernel exposes its log buffer to userspace via "/dev/kmsg" and "/proc/kmsg". If enabled,
these are made inaccessible to all the processes in the unit. If this setting is on, but
the unit doesn't have the "CAP_SYS_ADMIN" capability (e.g. services for which "User" is
set), "NoNewPrivileges=yes" is implied. Optional. Type boolean.

ProtectControlGroups
Takes a boolean argument. If true, the Linux Control Groups (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
"ReadOnlyPaths" and related calls, see above. Defaults to off. If "ProtectControlGroups"
is set, "MountAPIVFS=yes" is implied. Optional. Type boolean.

RestrictAddressFamilies
Restricts the set of socket address families accessible to the processes of this unit.
Takes "none", or a space-separated list of address family names to allow-list, such as
"AF_UNIX", "AF_INET" or "AF_INET6". When "none" is specified, then all address families
will be denied. When prefixed with "~" the listed address families will be applied as deny
list, otherwise as allow list. Note that this restricts access to the socket(2) system
call only. Sockets passed into the process by other means (for example, by using socket
activation with socket units, see 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, ppc64,
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
"SystemCallArchitectures=native" or similar. If running in user mode, or in system mode,
but without the "CAP_SYS_ADMIN" capability (e.g. setting "User"), "NoNewPrivileges=yes" is
implied. By default, no restrictions apply, all address families are accessible to
processes. If assigned the empty string, any previous address family restriction changes
are undone. This setting does not affect commands prefixed with "+".

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

RestrictFileSystems
Restricts the set of filesystems processes of this unit can open files on. Takes a space-
separated list of filesystem names. Any filesystem listed is made accessible to the unit's
processes, access to filesystem types not listed is prohibited (allow-listing). If the
first character of the list is "~", the effect is inverted: access to the filesystems
listed is prohibited (deny-listing). If the empty string is assigned, access to
filesystems is not restricted.

If you specify both types of this option (i.e. allow-listing and deny-listing), the first
encountered will take precedence and will dictate the default action (allow access to the
filesystem or deny it). Then the next occurrences of this option will add or delete the
listed filesystems from the set of the restricted filesystems, depending on its type and
the default action.

Example: if a unit has the following,

RestrictFileSystems=ext4 tmpfs
RestrictFileSystems=ext2 ext4

then access to "ext4", "tmpfs", and "ext2" is allowed and access to other filesystems is
denied.

Example: if a unit has the following,

RestrictFileSystems=ext4 tmpfs
RestrictFileSystems=~ext4

then only access "tmpfs" is allowed.

Example: if a unit has the following,

RestrictFileSystems=~ext4 tmpfs
RestrictFileSystems=ext4

then only access to "tmpfs" is denied.

As the number of possible filesystems is large, predefined sets of filesystems are
provided. A set starts with "@" character, followed by name of the set.

Use systemd-analyze(1)'s filesystems command to retrieve a list of filesystems defined on
the local system.

Note that this setting might not be supported on some systems (for example if the LSM eBPF
hook is not enabled in the underlying kernel or if not using the unified control group
hierarchy). In that case this setting has no effect. Optional. Type uniline.

RestrictNamespaces
Restricts access to Linux namespace functionality for the processes of this unit. For
details about Linux namespaces, see 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: "cgroup", "ipc", "net", "mnt", "pid",
"user" and "uts". Any namespace type listed is made accessible to the unit's processes,
access to namespace types not listed is prohibited (allow-listing). By prepending the list
with a single tilde character ("~") the effect may be inverted: only the listed namespace
types will be made inaccessible, all unlisted ones are permitted (deny-listing). 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 "OR", or by "AND" if the lines are prefixed with "~" (see examples
below). Internally, this setting limits access to the unshare(2), clone(2) and setns(2)
system calls, taking the specified flags parameters into account. Note that X if this
option is used X 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 "CAP_SYS_ADMIN" capability (e.g. setting "User"),
"NoNewPrivileges=yes" is implied.

Example: if a unit has the following,

RestrictNamespaces=cgroup ipc
RestrictNamespaces=cgroup net

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

RestrictNamespaces=cgroup ipc
RestrictNamespaces=~cgroup net

then, only "ipc" is set. Optional. Type uniline.

LockPersonality
Takes a boolean argument. If set, locks down the personality(2) system call so that the
kernel execution domain may not be changed from the default or the personality selected
with "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 "CAP_SYS_ADMIN" capability (e.g. setting
"User"), "NoNewPrivileges=yes" is implied. Optional. Type boolean.

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 mmap(2) system calls with both "PROT_EXEC" and
"PROT_WRITE" set, mprotect(2) or pkey_mprotect(2) system calls with "PROT_EXEC" set and
shmat(2) system calls with "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. However, the protection can be circumvented, if the
service can write to a filesystem, which is not mounted with "noexec" (such as
"/dev/shm"), or it can use memfd_create(). This can be prevented by making such file
systems inaccessible to the service (e.g. "InaccessiblePaths=/dev/shm") and installing
further system call filters ("SystemCallFilter=~memfd_create"). 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 "SystemCallArchitectures=native" or similar. If running in user mode, or
in system mode, but without the "CAP_SYS_ADMIN" capability (e.g. setting "User"),
"NoNewPrivileges=yes" is implied. Optional. Type boolean.

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 "SCHED_FIFO", "SCHED_RR" or "SCHED_DEADLINE". See sched(7) for details about these
scheduling policies. If running in user mode, or in system mode, but without the
"CAP_SYS_ADMIN" capability (e.g. setting "User"), "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. Optional. Type boolean.

RestrictSUIDSGID
Takes a boolean argument. If set, any attempts to set the set-user-ID (SUID) or set-group-
ID (SGID) bits on files or directories will be denied (for details on these bits see
inode(7)). If running in user mode, or in system mode, but without the "CAP_SYS_ADMIN"
capability (e.g. setting "User"), "NoNewPrivileges=yes" is implied. As the SUID/SGID bits
are mechanisms to elevate privileges, and allows users to acquire the identity of other
users, it is recommended to restrict creation of SUID/SGID files to the few programs that
actually require them. Note that this restricts marking of any type of file system object
with these bits, including both regular files and directories (where the SGID is a
different meaning than for files, see documentation). This option is implied if
"DynamicUser" is enabled. Defaults to off. Optional. Type boolean.

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 "User", "Group" and "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 "DynamicUser" is set. Optional. Type
boolean.

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 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
"CLONE_NEWNS" namespace is created, after which all existing mounts are remounted to
"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 "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 "ExecStartPre" will
hence be cleaned up automatically as soon as that process exits and will not be available
to subsequent processes forked off for "ExecStart" (and similar applies to the various
other commands configured for units). Similarly, "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 X "PrivateMounts", "PrivateTmp",
"PrivateDevices", "ProtectSystem", "ProtectHome", "ReadOnlyPaths", "InaccessiblePaths",
"ReadWritePaths", X X 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. Optional. Type boolean.

MountFlags
Takes a mount propagation setting: "shared", "slave" or "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
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 "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 namespace
to "slave" first. Setting this option to "shared" does not reestablish propagation in that
case.

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

It is not recommended to use "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 "PrivateMounts", see above. Optional. Type
uniline.

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 "SIGSYS" signal (allow-listing). (See "SystemCallErrorNumber"
below for changing the default action). If the first character of the list is "~", the
effect is inverted: only the listed system calls will result in immediate process
termination (deny-listing). Deny-listed system calls and system call groups may optionally
be suffixed with a colon (":") and "errno" error number (between 0 and 4095) or errno name
such as "EPERM", "EACCES" or "EUCLEAN" (see errno(3) for a full list). This value will be
returned when a deny-listed system call is triggered, instead of terminating the processes
immediately. Special setting "kill" can be used to explicitly specify killing. This value
takes precedence over the one given in "SystemCallErrorNumber", see below. If running in
user mode, or in system mode, but without the "CAP_SYS_ADMIN" capability (e.g. setting
"User"), "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 allow-listed 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 "+".

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
"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 X 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. allow-listing and deny-listing), 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 an allow list rule for
read() and write(), and right after it add a deny list rule for 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 "@" character, followed by name of the set. Currently
predefined system call setsSetDescription@aioAsynchronous I/O (io_setup(2), io_submit(2),
and related calls)@basic-ioSystem calls for basic I/O: reading, writing, seeking, file
descriptor duplication and closing (read(2), write(2), and related calls)@chownChanging
file ownership (chown(2), fchownat(2), and related calls)@clockSystem calls for changing
the system clock (adjtimex(2), settimeofday(2), and related calls)@cpu-emulationSystem
calls for CPU emulation functionality (vm86(2) and related calls)@debugDebugging,
performance monitoring and tracing functionality (ptrace(2), 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 (poll(2), select(2), epoll(7),
eventfd(2) and related calls)@ipcPipes, SysV IPC, POSIX Message Queues and other IPC
(mq_overview(7), svipc(7))@keyringKernel keyring access (keyctl(2) and related
calls)@memlockLocking of memory in RAM (mlock(2), mlockall(2) and related
calls)@moduleLoading and unloading of kernel modules (init_module(2), delete_module(2) and
related calls)@mountMounting and unmounting of file systems (mount(2), chroot(2), and
related calls)@network-ioSocket I/O (including local AF_UNIX): socket(7),
unix(7)@obsoleteUnusual, obsolete or unimplemented (create_module(2), gtty(2),
X)@privilegedAll system calls which need super-user capabilities
(capabilities(7))@processProcess control, execution, namespacing operations (clone(2),
kill(2), namespaces(7), X)@raw-ioRaw I/O port access (ioperm(2), iopl(2),
pciconfig_read(), X)@rebootSystem calls for rebooting and reboot preparation (reboot(2),
kexec(), X)@resourcesSystem calls for changing resource limits, memory and scheduling
parameters (setrlimit(2), setpriority(2), X)@setuidSystem calls for changing user ID and
group ID credentials, (setuid(2), setgid(2), setresuid(2), X)@signalSystem calls for
manipulating and handling process signals (signal(2), sigprocmask(2), X)@swapSystem calls
for enabling/disabling swap devices (swapon(2), swapoff(2))@syncSynchronizing files and
memory to disk (fsync(2), 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 allow-listing 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: @clock, @mount, @swap,
@reboot.@timerSystem calls for scheduling operations by time (alarm(2), timer_create(2),
X)@knownAll system calls defined by the kernel. This list is defined statically in systemd
based on a kernel version that was available when this systemd version was released. It
will become progressively more out-of-date as the kernel is updated. 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, allow-listing system calls (rather than deny-listing) is the safer mode of
operation. It is recommended to enforce system call allow lists for all long-running
system services. Specifically, the following lines are a relatively safe basic choice for
the majority of system services:

Note that various kernel system calls are defined redundantly: there are multiple system
calls for executing the same operation. For example, the pidfd_send_signal() system call
may be used to execute operations similar to what can be done with the older kill() system
call, hence blocking the latter without the former only provides weak protection. Since
new system calls are added regularly to the kernel as development progresses, keeping
system call deny lists comprehensive requires constant work. It is thus recommended to use
allow-listing instead, which offers the benefit that new system calls are by default
implicitly blocked until the allow list is updated.

Also note that a number of system calls are required to be accessible for the dynamic
linker to work. The dynamic linker is required for running most regular programs
(specifically: all dynamic ELF binaries, which is how most distributions build packaged
programs). This means that blocking these system calls (which include open(), openat() or
mmap()) will make most programs typically shipped with generic distributions unusable.

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

SystemCallErrorNumber
Takes an "errno" error number (between 1 and 4095) or errno name such as "EPERM", "EACCES"
or "EUCLEAN", to return when the system call filter configured with "SystemCallFilter" is
triggered, instead of terminating the process immediately. See errno(3) for a full list of
error codes. When this setting is not used, or when the empty string or the special
setting "kill" is assigned, the process will be terminated immediately when the filter is
triggered. Optional. Type uniline.

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 "ConditionArchitecture"
described in systemd.unit(5), as well as "x32", "mips64-n32", "mips64-le-n32", and the
special identifier "native". The special identifier "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
"CAP_SYS_ADMIN" capability (e.g. setting "User"), "NoNewPrivileges=yes" is implied. By
default, this option is set to the empty list, i.e. no 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 X a
limitation that x86-64 does not have, however. On systems supporting multiple ABIs at the
same time X such as x86/x86-64 X 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
"SystemCallArchitectures=native" is a good choice for disabling non-native ABIs.

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

SystemCallLog
Takes a space-separated list of system call names. If this setting is used, all system
calls executed by the unit processes for the listed ones will be logged. If the first
character of the list is "~", the effect is inverted: all system calls except the listed
system calls will be logged. If running in user mode, or in system mode, but without the
"CAP_SYS_ADMIN" capability (e.g. setting "User"), "NoNewPrivileges=yes" is implied. This
feature makes use of the Secure Computing Mode 2 interfaces of the kernel ('seccomp
filtering') and is useful for auditing or setting up a minimal sandboxing environment.
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 "+". Optional. Type list of uniline.

Environment
Sets environment variables for executed processes. Each line is unquoted using the rules
described in "Quoting" section in systemd.syntax(7) and becomes a list of variable
assignments. If you need to assign a value containing spaces or the equals sign to a
variable, put quotes around the whole assignment. Variable expansion is not performed
inside the strings and the "$" character has no special meaning. Specifier expansion is
performed, see the "Specifiers" section in systemd.unit(5).

This option may be specified more than once, in which case all listed variables will be
set. If the same variable is listed 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.

The names of the variables can contain ASCII letters, digits, and the underscore
character. Variable names cannot be empty or start with a digit. In variable values, most
characters are allowed, but non-printable characters are currently rejected.

Example:

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

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

See environ(7) for details about environment variables.

Note that environment variables are not suitable for passing secrets (such as passwords,
key material, X) 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. Use "LoadCredential",
"LoadCredentialEncrypted" or "SetCredentialEncrypted" (see below) to pass data to unit
processes securely. Optional. Type list of uniline.

EnvironmentFile
Similar to "Environment" but reads the environment variables from a text file. The text
file should contain newline-separated variable assignments. Empty lines, lines without an
"=" separator, or lines starting with ";" or "#" will be ignored, which may be used for
commenting. The file must be UTF-8 encoded. Valid characters are unicode scalar values
<https://www.unicode.org/glossary/#unicode_scalar_value> other than noncharacters
<https://www.unicode.org/glossary/#noncharacter>, U+0000 NUL, and U+FEFF byte order mark
<https://www.unicode.org/glossary/#byte_order_mark>. Control codes other than NUL are
allowed.

In the file, an unquoted value after the "=" is parsed with the same backslash-escape
rules as unquoted text
<https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_02_01>
in a POSIX shell, but unlike in a shell, interior whitespace is preserved and quotes after
the first non-whitespace character are preserved. Leading and trailing whitespace (space,
tab, carriage return) is discarded, but interior whitespace within the line is preserved
verbatim. A line ending with a backslash will be continued to the following one, with the
newline itself discarded. A backslash "\" followed by any character other than newline
will preserve the following character, so that "\\" will become the value "\".

In the file, a "'"-quoted value after the "=" can span multiple lines and contain any
character verbatim other than single quote, like single-quoted text
<https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_02_02>
in a POSIX shell. No backslash-escape sequences are recognized. Leading and trailing
whitespace outside of the single quotes is discarded.

In the file, a """-quoted value after the "=" can span multiple lines, and the same escape
sequences are recognized as in double-quoted text
<https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_02_03>
of a POSIX shell. Backslash ("\") followed by any of ""\`$" will preserve that character.
A backslash followed by newline is a line continuation, and the newline itself is
discarded. A backslash followed by any other character is ignored; both the backslash and
the following character are preserved verbatim. Leading and trailing whitespace outside of
the double quotes is discarded.

The argument passed should be an absolute filename or wildcard expression, optionally
prefixed with "-", 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.
The files are read from the file system of the service manager, before any file system
changes like bind mounts take place).

Settings from these files override settings made with "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. Optional. Type list of uniline.

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 "Environment" or "EnvironmentFile".

Example:

PassEnvironment=VAR1 VAR2 VAR3

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

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

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 "=", 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 "=" or value),
then any assignment matching the variable name, regardless of its value is removed. Note
that the effect of "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 "Environment" or
"EnvironmentFile", inherited from the system manager's global set of environment
variables, inherited via "PassEnvironment", set by the service manager itself (such as
$NOTIFY_SOCKET and such), or set by a PAM module (in case "PAMName" is used).

See "Environment Variables in Spawned Processes" below for a description of how those
settings combine to form the inherited environment. See environ(7) for general information
about environment variables. Optional. Type list of uniline.

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

If "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 "tty" is selected, standard input is connected to a TTY (as configured by "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.

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

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

The "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
"StandardInputText"/"StandardInputData" (see below). Note that the actual file descriptor
type passed (memory file, regular file, UNIX pipe, X) 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 "file:path" option may be used to connect a specific file system object to standard
input. An absolute path following the ":" character is expected, which may refer to a
regular file, a FIFO or special file. If an "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 "socket" option is valid in socket-activated services only, and requires the relevant
socket unit file (see systemd.socket(5) for details) to have "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 inetd(8) socket activation daemon.

The "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 ":"
character (e.g. "fd:foobar"). If no name is specified, the name "stdin" is implied (i.e.
"fd" is equivalent to "fd:stdin"). At least one socket unit defining the specified name
must be provided via the "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 "FileDescriptorName" in systemd.socket(5) for more details about named file
descriptors and their ordering.

This setting defaults to "null", unless "StandardInputText"/"StandardInputData" are set,
in which case it defaults to "data". Optional. Type enum. choice: 'null', 'tty',
'tty-force', 'tty-fail', 'data', 'socket'.

StandardOutput
Controls where file descriptor 1 (stdout) of the executed processes is connected to. Takes
one of "inherit", "null", "tty", "journal", "kmsg", "journal+console", "kmsg+console",
"file:path", "append:path", "truncate:path", "socket" or "fd:name".

"inherit" duplicates the file descriptor of standard input for standard output.

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

"tty" connects standard output to a tty (as configured via "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.

"journal" connects standard output with the journal, which is accessible via
journalctl(1). Note that everything that is written to kmsg (see below) is implicitly
stored in the journal as well, the specific option listed below is hence a superset of
this one. (Also note that any external, additional syslog daemons receive their log data
from the journal, too, hence this is the option to use when logging shall be processed
with such a daemon.)

"kmsg" connects standard output with the kernel log buffer which is accessible via
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 "journal".

"journal+console" and "kmsg+console" work in a similar way as the two options above but
copy the output to the system console as well.

The "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 "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 X for reading
as well as writing X and duplicated. This is particularly useful when the specified path
refers to an "AF_UNIX" socket in the file system, as in that case only a single stream
connection is created for both input and output.

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

"truncate:path" is similar to "file:path" above, but it truncates the file when opening
it. For units with multiple command lines, e.g. "Type=oneshot" services with multiple
"ExecStart", or services with "ExecCondition", "ExecStartPre" or "ExecStartPost", the
output file is reopened and therefore re-truncated for each command line. If the output
file is truncated while another process still has the file open, e.g. by an "ExecReload"
running concurrently with an "ExecStart", and the other process continues writing to the
file without adjusting its offset, then the space between the file pointers of the two
processes may be filled with "NUL" bytes, producing a sparse file. Thus, "truncate:path"
is typically only useful for units where only one process runs at a time, such as services
with a single "ExecStart" and no "ExecStartPost", "ExecReload", "ExecStop" or similar.

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

The "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
":" character (e.g. "fd:foobar"). If no name is specified, the name "stdout" is implied
(i.e. "fd" is equivalent to "fd:stdout"). At least one socket unit defining the specified
name must be provided via the "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 "FileDescriptorName" in 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
or the kernel log buffer, the unit will implicitly gain a dependency of type "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 "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 "DefaultStandardOutput" in
systemd-system.conf(5), which defaults to "journal". Note that setting this parameter
might result in additional dependencies to be added to the unit (see above). Optional.
Type enum. choice: 'inherit', 'null', 'tty', 'journal', 'kmsg', 'journal+console',
'kmsg+console', 'socket'.

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

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

StandardInputText
Configures arbitrary textual or binary data to pass via file descriptor 0 (STDIN) to the
executed processes. These settings have no effect unless "StandardInput" is set to "data"
(which is the default if "StandardInput" is not set otherwise, but
"StandardInputText"/"StandardInputData" is). Use this option to embed process input data
directly in the unit file.

"StandardInputText" accepts arbitrary textual data. C-style escapes for special characters
as well as the usual "%"-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 "\n" to the end or beginning of a line).

"StandardInputData" accepts arbitrary binary data, encoded in Base64
<https://tools.ietf.org/html/rfc2045#section-6.8>. No escape sequences or specifiers are
resolved. Any whitespace in the encoded version is ignored during decoding.

Note that "StandardInputText" and "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 "\"
character (see systemd.unit(5) for details). This is particularly useful for large data
configured with these two options. Example: Optional. Type uniline.

StandardInputData
Configures arbitrary textual or binary data to pass via file descriptor 0 (STDIN) to the
executed processes. These settings have no effect unless "StandardInput" is set to "data"
(which is the default if "StandardInput" is not set otherwise, but
"StandardInputText"/"StandardInputData" is). Use this option to embed process input data
directly in the unit file.

LogLevelMax
Configures filtering by log level of log messages generated by this unit. Takes a syslog
log level, one of "emerg" (lowest log level, only highest priority messages), "alert",
"crit", "err", "warning", "notice", "info", "debug" (highest log level, also lowest
priority messages). See syslog(3) for details. By default no filtering is applied (i.e.
the default maximum log level is "debug"). Use this option to configure the logging system
to drop log messages of a specific service above the specified level. For example, set
"LogLevelMax""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, as well as any log messages written by the system manager process
(PID 1) in reference 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, "MaxLevelStore"
configured in journald.conf(5) might prohibit messages of higher log levels to be stored
on disk, even though the per-unit "LogLevelMax" permitted it to be processed. Optional.
Type uniline.

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 "FIELD=VALUE" separated by whitespace. See
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. Optional. Type uniline.

LogRateLimitIntervalSec
Configures the rate limiting that is applied to messages generated by this unit. If, in
the time interval defined by "LogRateLimitIntervalSec", more messages than specified in
"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 "LogRateLimitIntervalSec" may be specified in the
following units: "s", "min", "h", "ms", "us" (see systemd.time(7) for details). The
default settings are set by "RateLimitIntervalSec" and "RateLimitBurst" configured in
journald.conf(5). Optional. Type uniline.

LogRateLimitBurst
Configures the rate limiting that is applied to messages generated by this unit. If, in
the time interval defined by "LogRateLimitIntervalSec", more messages than specified in
"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 "LogRateLimitIntervalSec" may be specified in the
following units: "s", "min", "h", "ms", "us" (see systemd.time(7) for details). The
default settings are set by "RateLimitIntervalSec" and "RateLimitBurst" configured in
journald.conf(5). Optional. Type uniline.

LogNamespace
Run the unit's processes in the specified journal namespace. Expects a short user-defined
string identifying the namespace. If not used the processes of the service are run in the
default journal namespace, i.e. their log stream is collected and processed by
"systemd-journald.service". If this option is used any log data generated by processes of
this unit (regardless if via the syslog(), journal native logging or stdout/stderr
logging) is collected and processed by an instance of the "systemd-journald@.service"
template unit, which manages the specified namespace. The log data is stored in a data
store independent from the default log namespace's data store. See
systemd-journald.service(8) for details about journal namespaces.

Internally, journal namespaces are implemented through Linux mount namespacing and over-
mounting the directory that contains the relevant "AF_UNIX" sockets used for logging in
the unit's mount namespace. Since mount namespaces are used this setting disconnects
propagation of mounts from the unit's processes to the host, similar to how
"ReadOnlyPaths" and similar settings (see above) work. Journal namespaces may hence not be
used for services that need to establish mount points on the host.

When this option is used the unit will automatically gain ordering and requirement
dependencies on the two socket units associated with the "systemd-journald@.service"
instance so that they are automatically established prior to the unit starting up. Note
that when this option is used log output of this service does not appear in the regular
journalctl(1) output, unless the "--namespace=" option is used. Optional. Type uniline.

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 "StandardOutput" or "StandardError" are set to "journal"
or "kmsg" (or to the same settings in combination with "+console") and only applies to log
messages written to stdout or stderr. Optional. Type uniline.

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

SyslogLevel
The default syslog log level to use when logging to the logging system or the kernel log
buffer. One of "emerg", "alert", "crit", "err", "warning", "notice", "info", "debug". See
syslog(3) for details. This option is only useful when "StandardOutput" or "StandardError"
are set to "journal" or "kmsg" (or to the same settings in combination with "+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 "SyslogLevelPrefix", see below. For details, see sd-daemon(3). Defaults
to "info". Optional. Type uniline.

SyslogLevelPrefix
Takes a boolean argument. If true and "StandardOutput" or "StandardError" are set to
"journal" or "kmsg" (or to the same settings in combination with "+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 sd-daemon(3).
Defaults to true. Optional. Type boolean.

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". Optional. Type uniline.

TTYReset
Reset the terminal device specified with "TTYPath" before and after execution. Defaults
to "no". Optional. Type uniline.

TTYVHangup
Disconnect all clients which have opened the terminal device specified with "TTYPath"
before and after execution. Defaults to "no". Optional. Type uniline.

TTYRows
Configure the size of the TTY specified with "TTYPath". If unset or set to the empty
string, the kernel default is used. Optional. Type uniline.

TTYColumns
Configure the size of the TTY specified with "TTYPath". If unset or set to the empty
string, the kernel default is used. Optional. Type uniline.

TTYVTDisallocate
If the terminal device specified with "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 "no". Optional. Type uniline.

LoadCredential
Pass a credential to the unit. Credentials are limited-size binary or textual objects that
may be passed to unit processes. They are primarily used for passing cryptographic keys
(both public and private) or certificates, user account information or identity
information from host to services. The data is accessible from the unit's processes via
the file system, at a read-only location that (if possible and permitted) is backed by
non-swappable memory. The data is only accessible to the user associated with the unit,
via the "User"/"DynamicUser" settings (as well as the superuser). When available, the
location of credentials is exported as the $CREDENTIALS_DIRECTORY environment variable to
the unit's processes.

The "LoadCredential" setting takes a textual ID to use as name for a credential plus a
file system path, separated by a colon. The ID must be a short ASCII string suitable as
filename in the filesystem, and may be chosen freely by the user. If the specified path is
absolute it is opened as regular file and the credential data is read from it. If the
absolute path refers to an "AF_UNIX" stream socket in the file system a connection is made
to it (only once at unit start-up) and the credential data read from the connection,
providing an easy IPC integration point for dynamically transferring credentials from
other services.

If the specified path is not absolute and itself qualifies as valid credential identifier
it is attempted to find a credential that the service manager itself received under the
specified name X which may be used to propagate credentials from an invoking environment
(e.g. a container manager that invoked the service manager) into a service. If no matching
system credential is found, the directories "/etc/credstore/", "/run/credstore/" and
"/usr/lib/credstore/" are searched for files under the credential's name X which hence are
recommended locations for credential data on disk. If "LoadCredentialEncrypted" is used
"/run/credstore.encrypted/", "/etc/credstore.encrypted/", and
"/usr/lib/credstore.encrypted/" are searched as well.

If the file system path is omitted it is chosen identical to the credential name, i.e.
this is a terse way to declare credentials to inherit from the service manager into a
service. This option may be used multiple times, each time defining an additional
credential to pass to the unit.

If an absolute path referring to a directory is specified, every file in that directory
(recursively) will be loaded as a separate credential. The ID for each credential will be
the provided ID suffixed with "_$FILENAME" (e.g., "Key_file1"). When loading from a
directory, symlinks will be ignored.

The contents of the file/socket may be arbitrary binary or textual data, including newline
characters and "NUL" bytes.

The "LoadCredentialEncrypted" setting is identical to "LoadCredential", except that the
credential data is decrypted and authenticated before being passed on to the executed
processes. Specifically, the referenced path should refer to a file or socket with an
encrypted credential, as implemented by systemd-creds(1). This credential is loaded,
decrypted, authenticated and then passed to the application in plaintext form, in the same
way a regular credential specified via "LoadCredential" would be. A credential configured
this way may be symmetrically encrypted/authenticated with a secret key derived from the
system's TPM2 security chip, or with a secret key stored in
"/var/lib/systemd/credentials.secret", or with both. Using encrypted and authenticated
credentials improves security as credentials are not stored in plaintext and only
authenticated and decrypted into plaintext the moment a service requiring them is started.
Moreover, credentials may be bound to the local hardware and installations, so that they
cannot easily be analyzed offline, or be generated externally.

The credential files/IPC sockets must be accessible to the service manager, but don't have
to be directly accessible to the unit's processes: the credential data is read and copied
into separate, read-only copies for the unit that are accessible to appropriately
privileged processes. This is particularly useful in combination with "DynamicUser" as
this way privileged data can be made available to processes running under a dynamic UID
(i.e. not a previously known one) without having to open up access to all users.

In order to reference the path a credential may be read from within a "ExecStart" command
line use "${CREDENTIALS_DIRECTORY}/mycred", e.g. "ExecStart=cat
${CREDENTIALS_DIRECTORY}/mycred". In order to reference the path a credential may be read
from within a "Environment" line use "%d/mycred", e.g. "Environment=MYCREDPATH=%d/mycred".

Currently, an accumulated credential size limit of 1 MB per unit is enforced.

The service manager itself may receive system credentials that can be propagated to
services from a hosting container manager or VM hypervisor. See the Container Interface
<https://systemd.io/CONTAINER_INTERFACE> documentation for details about the former. For
the latter, use the qemu "fw_cfg" node "opt/io.systemd.credentials/". Example qemu switch:
"-fw_cfg name=opt/io.systemd.credentials/mycred,string=supersecret". They may also be
specified on the kernel command line using the "systemd.set_credential=" switch (see
systemd(1)) and from the UEFI firmware environment via systemd-stub(7).

If referencing an "AF_UNIX" stream socket to connect to, the connection will originate
from an abstract namespace socket, that includes information about the unit and the
credential ID in its socket name. Use getpeername(2) to query this information. The
returned socket name is formatted as "NUL"RANDOM "/unit/" UNIT"/" ID, i.e. a "NUL" byte
(as required for abstract namespace socket names), followed by a random string (consisting
of alphadecimal characters), followed by the literal string "/unit/", followed by the
requesting unit name, followed by the literal character "/", followed by the textual
credential ID requested. Example: "\0adf9d86b6eda275e/unit/foobar.service/credx" in case
the credential "credx" is requested for a unit "foobar.service". This functionality is
useful for using a single listening socket to serve credentials to multiple consumers.

For further information see System and Service Credentials
<https://systemd.io/CREDENTIALS> documentation. Optional. Type uniline.

LoadCredentialEncrypted
Pass a credential to the unit. Credentials are limited-size binary or textual objects that
may be passed to unit processes. They are primarily used for passing cryptographic keys
(both public and private) or certificates, user account information or identity
information from host to services. The data is accessible from the unit's processes via
the file system, at a read-only location that (if possible and permitted) is backed by
non-swappable memory. The data is only accessible to the user associated with the unit,
via the "User"/"DynamicUser" settings (as well as the superuser). When available, the
location of credentials is exported as the $CREDENTIALS_DIRECTORY environment variable to
the unit's processes.

The contents of the file/socket may be arbitrary binary or textual data, including newline
characters and "NUL" bytes.

Currently, an accumulated credential size limit of 1 MB per unit is enforced.

For further information see System and Service Credentials
<https://systemd.io/CREDENTIALS> documentation. Optional. Type uniline.

SetCredential
The "SetCredential" setting is similar to "LoadCredential" but accepts a literal value to
use as data for the credential, instead of a file system path to read the data from. Do
not use this option for data that is supposed to be secret, as it is accessible to
unprivileged processes via IPC. It's only safe to use this for user IDs, public key
material and similar non-sensitive data. For everything else use "LoadCredential". In
order to embed binary data into the credential data use C-style escaping (i.e. "\n" to
embed a newline, or "\x00" to embed a "NUL" byte).

The "SetCredentialEncrypted" setting is identical to "SetCredential" but expects an
encrypted credential in literal form as value. This allows embedding confidential
credentials securely directly in unit files. Use systemd-creds(1)' "-p" switch to generate
suitable "SetCredentialEncrypted" lines directly from plaintext credentials. For further
details see "LoadCredentialEncrypted" above.

If a credential of the same ID is listed in both "LoadCredential" and "SetCredential", the
latter will act as default if the former cannot be retrieved. In this case not being able
to retrieve the credential from the path specified in "LoadCredential" is not considered
fatal. Optional. Type uniline.

SetCredentialEncrypted
The "SetCredential" setting is similar to "LoadCredential" but accepts a literal value to
use as data for the credential, instead of a file system path to read the data from. Do
not use this option for data that is supposed to be secret, as it is accessible to
unprivileged processes via IPC. It's only safe to use this for user IDs, public key
material and similar non-sensitive data. For everything else use "LoadCredential". In
order to embed binary data into the credential data use C-style escaping (i.e. "\n" to
embed a newline, or "\x00" to embed a "NUL" byte).

UtmpIdentifier
Takes a four character identifier string for an utmp(5) and wtmp entry for this service.
This should only be set for services such as getty implementations (such as 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.
Optional. Type uniline.

UtmpMode
Takes one of "init", "login" or "user". If "UtmpIdentifier" is set, controls which type of
utmp(5)/wtmp entries for this service are generated. This setting has no effect unless
"UtmpIdentifier" is set too. If "init" is set, only an "INIT_PROCESS" entry is generated
and the invoked process must implement a getty-compatible utmp/wtmp logic. If "login" is
set, first an "INIT_PROCESS" entry, followed by a "LOGIN_PROCESS" entry is generated. In
this case, the invoked process must implement a login(1)-compatible utmp/wtmp logic. If
"user" is set, first an "INIT_PROCESS" entry, then a "LOGIN_PROCESS" entry and finally a
"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 "init". Optional. Type enum.
choice: 'init', 'login', 'user'.

KillMode
Specifies how processes of this unit shall be killed. One of "control-group", "mixed",
"process", "none".

If set to "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 "ExecStop"). If set to "mixed", the "SIGTERM" signal (see below) is sent to the main
process while the subsequent "SIGKILL" signal (see below) is sent to all remaining
processes of the unit's control group. If set to "process", only the main process itself
is killed (not recommended!). If set to "none", no process is killed (strongly recommended
against!). In this case, only the stop command will be executed on unit stop, but no
process will be killed otherwise. Processes remaining alive after stop are left in their
control group and the control group continues to exist after stop unless empty.

Note that it is not recommended to set "KillMode" to "process" or even "none", as this
allows processes to escape the service manager's lifecycle and resource management, and to
remain running even while their service is considered stopped and is assumed to not
consume any resources.

Processes will first be terminated via "SIGTERM" (unless the signal to send is changed via
"KillSignal" or "RestartKillSignal"). Optionally, this is immediately followed by a
"SIGHUP" (if enabled with "SendSIGHUP"). If processes still remain after the main process
of a unit has exited or the delay configured via the "TimeoutStopSec" has passed, the
termination request is repeated with the "SIGKILL" signal or the signal specified via
"FinalKillSignal" (unless this is disabled via the "SendSIGKILL" option). See kill(2) for
more information.

Defaults to "control-group". Optional. Type uniline.

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

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

RestartKillSignal
Specifies which signal to use when restarting a service. The same as "KillSignal"
described above, with the exception that this setting is used in a restart job. Not set by
default, and the value of "KillSignal" is used. Optional. Type uniline.

SendSIGHUP
Specifies whether to send "SIGHUP" to remaining processes immediately after sending the
signal configured with "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".
Optional. Type boolean.

SendSIGKILL
Specifies whether to send "SIGKILL" (or the signal specified by "FinalKillSignal") to
remaining processes after a timeout, if the normal shutdown procedure left processes of
the service around. When disabled, a "KillMode" of "control-group" or "mixed" service will
not restart if processes from prior services exist within the control group. Takes a
boolean value. Defaults to "yes". Optional. Type boolean.

FinalKillSignal
Specifies which signal to send to remaining processes after a timeout if "SendSIGKILL" is
enabled. The signal configured here should be one that is not typically caught and
processed by services ("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 "SIGTERM" signal. This can be achieved by configuring "LimitCORE" and setting
"FinalKillSignal" to either "SIGQUIT" or "SIGABRT". Defaults to "SIGKILL". Optional.
Type uniline.

WatchdogSignal
Specifies which signal to use to terminate the service when the watchdog timeout expires
(enabled through "WatchdogSec"). Defaults to "SIGABRT". Optional. Type uniline.

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

It is generally recommended to use "Type""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 X 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, "notify"
or "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
"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) X if it's
not supported, then "forking" is an alternative: it supports the traditional UNIX service
start-up protocol. Finally, "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 "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 "simple". (Also note it is generally not
recommended to use "idle" or "oneshot" for long-running services.) Optional. Type
uniline.

ExitType
Specifies when the manager should consider the service to be finished. One of "main" or
"cgroup":

It is generally recommended to use "ExitType""main" when a service has a known forking
model and a main process can reliably be determined. "ExitType""cgroup" is meant for
applications whose forking model is not known ahead of time and which might not have a
specific main process. It is well suited for transient or automatically generated
services, such as graphical applications inside of a desktop environment. Optional. Type
uniline.

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

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 "Type=forking"
is set and "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 "yes". Optional. Type boolean.

PIDFile
Takes a path referring to the PID file of the service. Usage of this option is recommended
for services where "Type" is set to "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.

Note that PID files should be avoided in modern projects. Use "Type=notify" or
"Type=simple" where possible, which does not require use of PID files to determine the
main process of a service and avoids needless forking. Optional. Type uniline.

BusName
Takes a D-Bus destination name that this service shall use. This option is mandatory for
services where "Type" is set to "dbus". It is recommended to always set this property if
known to make it easy to map the service name to the D-Bus destination. In particular,
systemctl service-log-level/service-log-target verbs make use of this. Optional. Type
uniline.

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 "Type" is "oneshot", exactly one command must be given. When "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 "ExecStart" is specified, then the service must have
"RemainAfterExit=yes" and at least one "ExecStop" line set. (Services lacking both
"ExecStart" and "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:

"@", "-", ":", and one of "+"/"!"/"!!" may be used together and they can appear in any
order. However, only one of "+", "!", "!!" may be used at a time. Note that these prefixes
are also supported for the other command line settings, i.e. "ExecStartPre",
"ExecStartPost", "ExecReload", "ExecStop" and "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 "-"),
other lines are not executed, and the unit is considered failed.

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

ExecStartPre
Additional commands that are executed before or after the command in "ExecStart",
respectively. Syntax is the same as for "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 "-") fail, the rest are not executed and the
unit is considered failed.

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

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

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

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

Note that the execution of "ExecStartPost" is taken into account for the purpose of
"Before"/"After" ordering constraints. Optional. Type list of uniline.

ExecStartPost
Additional commands that are executed before or after the command in "ExecStart",
respectively. Syntax is the same as for "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 "-") fail, the rest are not executed and the
unit is considered failed.

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

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

Note that the execution of "ExecStartPost" is taken into account for the purpose of
"Before"/"After" ordering constraints. Optional. Type list of uniline.

ExecCondition
Optional commands that are executed before the command(s) in "ExecStartPre". Syntax is
the same as for "ExecStart", except that multiple command lines are allowed and the
commands are executed one after the other, serially.

The behavior is like an "ExecStartPre" and condition check hybrid: when an "ExecCondition"
command exits with exit code 1 through 254 (inclusive), the remaining commands are skipped
and the unit is not marked as failed. However, if an "ExecCondition" command exits with
255 or abnormally (e.g. timeout, killed by a signal, etc.), the unit will be considered
failed (and remaining commands will be skipped). Exit code of 0 or those matching
"SuccessExitStatus" will continue execution to the next command(s).

The same recommendations about not running long-running processes in "ExecStartPre" also
applies to "ExecCondition". "ExecCondition" will also run the commands in "ExecStopPost",
as part of stopping the service, in the case of any non-zero or abnormal exits, like the
ones described above. Optional. Type list of uniline.

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 "ExecStart" above. Use
of this setting is optional. Specifier and environment variable substitution is supported
here following the same scheme as for "ExecStart".

One additional, special environment variable is set: if known, $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 "ExecReload" to a command that not only triggers a configuration reload
of the daemon, but also synchronously waits for it to complete. For example,
dbus-broker(1) uses the following: Optional. Type list of uniline.

ExecStop
Commands to execute to stop the service started via "ExecStart". This argument takes
multiple command lines, following the same scheme as described for "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 "KillMode" setting (see systemd.kill(5)). If this option is not
specified, the process is terminated by sending the signal specified in "KillSignal" or
"RestartKillSignal" when service stop is requested. Specifier and environment variable
substitution is supported (including $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 sending some form of termination signal to
it), but does not wait for it to do so. Since the remaining processes of the services are
killed according to "KillMode" and "KillSignal" or "RestartKillSignal" 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 "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
"ExecStart", "ExecStartPre" or "ExecStartPost" failed (and weren't prefixed with "-", see
above) or timed out. Use "ExecStopPost" to invoke commands when a service failed to start
up correctly and is shut down again. Also note that the stop operation is always performed
if the service started successfully, even if the processes in the service terminated on
their own or were killed. The stop commands must be prepared to deal with that case.
$MAINPID will be unset if systemd knows that the main process exited by the time the stop
commands are called.

Service restart requests are implemented as stop operations followed by start operations.
This means that "ExecStop" and "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. For post-mortem clean-up steps use "ExecStopPost" instead.
Optional. Type list of uniline.

ExecStopPost
Additional commands that are executed after the service is stopped. This includes cases
where the commands configured in "ExecStop" were used, where the service does not have any
"ExecStop" defined, or where the service exited unexpectedly. This argument takes multiple
command lines, following the same scheme as described for "ExecStart". Use of these
settings is optional. Specifier and environment variable substitution is supported. Note
that X unlike "ExecStop" X 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
$SERVICE_RESULT, $EXIT_CODE and $EXIT_STATUS environment variables, see systemd.exec(5)
for details.

Note that the execution of "ExecStopPost" is taken into account for the purpose of
"Before"/"After" ordering constraints. Optional. Type list of uniline.

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

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. The precise action depends on the "TimeoutStartFailureMode" option. Takes
a unit-less value in seconds, or a time span value such as "5min 20s". Pass "infinity" to
disable the timeout logic. Defaults to "DefaultTimeoutStartSec" from the manager
configuration file, except when "Type=oneshot" is used, in which case the timeout is
disabled by default (see systemd-system.conf(5)).

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

TimeoutStopSec
This option serves two purposes. First, it configures the time to wait for each "ExecStop"
command. If any of them times out, subsequent "ExecStop" commands are skipped and the
service will be terminated by "SIGTERM". If no "ExecStop" commands are specified, the
service gets the "SIGTERM" immediately. This default behavior can be changed by the
"TimeoutStopFailureMode" option. 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 "SIGKILL" (see "KillMode" in systemd.kill(5)). Takes a unit-less value in
seconds, or a time span value such as "5min 20s". Pass "infinity" to disable the timeout
logic. Defaults to "DefaultTimeoutStopSec" from the manager configuration file (see
systemd-system.conf(5)).

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

TimeoutAbortSec
This option configures the time to wait for the service to terminate when it was aborted
due to a watchdog timeout (see "WatchdogSec"). If the service has a short "TimeoutStopSec"
this option can be used to give the system more time to write a core dump of the service.
Upon expiration the service will be forcibly terminated by "SIGKILL" (see "KillMode" in
systemd.kill(5)). The core file will be truncated in this case. Use "TimeoutAbortSec" to
set a sensible timeout for the core dumping per service that is large enough to write all
expected data while also being short enough to handle the service failure in due time.

Takes a unit-less value in seconds, or a time span value such as "5min 20s". Pass an empty
value to skip the dedicated watchdog abort timeout handling and fall back
"TimeoutStopSec". Pass "infinity" to disable the timeout logic. Defaults to
"DefaultTimeoutAbortSec" from the manager configuration file (see systemd-system.conf(5)).

If a service of "Type=notify" handles "SIGABRT" itself (instead of relying on the kernel
to write a core dump) it can send "EXTEND_TIMEOUT_USEC=X" to extended the abort time
beyond "TimeoutAbortSec". The first receipt of this message must occur before
"TimeoutAbortSec" is exceeded, and once the abort time has extended beyond
"TimeoutAbortSec", the service manager will allow the service to continue to abort,
provided the service repeats "EXTEND_TIMEOUT_USEC=X" within the interval specified, or
terminates itself (see sd_notify(3)). Optional. Type uniline.

TimeoutSec
A shorthand for configuring both "TimeoutStartSec" and "TimeoutStopSec" to the specified
value. Optional. Type uniline.

TimeoutStartFailureMode
These options configure the action that is taken in case a daemon service does not signal
start-up within its configured "TimeoutStartSec", respectively if it does not stop within
"TimeoutStopSec". Takes one of "terminate", "abort" and "kill". Both options default to
"terminate".

If "terminate" is set the service will be gracefully terminated by sending the signal
specified in "KillSignal" (defaults to "SIGTERM", see systemd.kill(5)). If the service
does not terminate the "FinalKillSignal" is sent after "TimeoutStopSec". If "abort" is
set, "WatchdogSignal" is sent instead and "TimeoutAbortSec" applies before sending
"FinalKillSignal". This setting may be used to analyze services that fail to start-up or
shut-down intermittently. By using "kill" the service is immediately terminated by
sending "FinalKillSignal" without any further timeout. This setting can be used to
expedite the shutdown of failing services. Optional. Type enum. choice: 'terminate',
'abort', 'kill'.

TimeoutStopFailureMode
These options configure the action that is taken in case a daemon service does not signal
start-up within its configured "TimeoutStartSec", respectively if it does not stop within
"TimeoutStopSec". Takes one of "terminate", "abort" and "kill". Both options default to
"terminate".

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 "Type=oneshot" services, as they
terminate immediately after activation completed. Pass "infinity" (the default) to
configure no runtime limit.

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

RuntimeRandomizedExtraSec
This option modifies "RuntimeMaxSec" by increasing the maximum runtime by an evenly
distributed duration between 0 and the specified value (in seconds). If "RuntimeMaxSec" is
unspecified, then this feature will be disabled. Optional. Type uniline.

WatchdogSec
Configures the watchdog timeout for a service. The watchdog is activated when the start-
up is completed. The service must call sd_notify(3) regularly with "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 "SIGABRT" (or
the signal specified by "WatchdogSignal"). By setting "Restart" to "on-failure",
"on-watchdog", "on-abnormal" or "always", the service will be automatically restarted. The
time configured here will be passed to the executed service process in the "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,
"NotifyAccess" (see below) should be set to open access to the notification socket
provided by systemd. If "NotifyAccess" is not set, it will be implicitly set to "main".
Defaults to 0, which disables this feature. The service can check whether the service
manager expects watchdog keep-alive notifications. See sd_watchdog_enabled(3) for details.
sd_event_set_watchdog(3) may be used to enable automatic watchdog notification support.
Optional. Type uniline.

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 "ExecStartPre", "ExecStartPost",
"ExecStop", "ExecStopPost", or "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 "no", "on-success", "on-failure", "on-abnormal", "on-watchdog", "on-abort",
or "always". If set to "no" (the default), the service will not be restarted. If set to
"on-success", it will be restarted only when the service process exits cleanly. In this
context, a clean exit means any of the following: exit code of 0;for types other than
"Type=oneshot", one of the signals "SIGHUP", "SIGINT", "SIGTERM", or "SIGPIPE";exit
statuses and signals specified in "SuccessExitStatus". If set to "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 "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 "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 "on-watchdog", the service
will be restarted only if the watchdog timeout for the service expires. If set to
"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 "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 "RestartForceExitStatus" (see below).

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

Setting this to "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),
"on-abnormal" is an alternative choice. Optional. Type enum. choice: 'no', 'on-success',
'on-failure', 'on-abnormal', 'on-watchdog', 'on-abort', 'always'.

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
status 0 and, except for "Type=oneshot", the signals "SIGHUP", "SIGINT", "SIGTERM", and
"SIGPIPE". Exit status definitions can be numeric termination statuses, termination status
names, or termination signal names, separated by spaces. See the Process Exit Codes
section in systemd.exec(5) for a list of termination status names (for this setting only
the part without the "EXIT_" or "EX_" prefix should be used). See signal(7) for a list of
signal names.

Note that this setting does not change the mapping between numeric exit statuses and their
names, i.e. regardless how this setting is used 0 will still be mapped to "SUCCESS" (and
thus typically shown as "0/SUCCESS" in tool outputs) and 1 to "FAILURE" (and thus
typically shown as "1/FAILURE"), and so on. It only controls what happens as effect of
these exit statuses, and how it propagates to the state of the service as a whole.

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.

Note: systemd-analyze exit-status may be used to list exit statuses and translate between
numerical status values and names. Optional. Type uniline.

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
"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 "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.

Note that this setting has no effect on processes configured via "ExecStartPre",
"ExecStartPost", "ExecStop", "ExecStopPost" or "ExecReload", but only on the main service
process, i.e. either the one invoked by "ExecStart" or (depending on "Type", "PIDFile", X)
the otherwise configured main process. Optional. Type uniline.

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
"Restart". The argument format is similar to "RestartPreventExitStatus". Optional. Type
uniline.

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

NonBlocking
Set the "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 "FileDescriptorStoreMax" for
details), will have the "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 systemd.socket(5)
and has no effect on file descriptors which were previously saved in the file-descriptor
store for example. Defaults to false. Optional. Type uniline.

NotifyAccess
Controls access to the service status notification socket, as accessible via the
sd_notify(3) call. Takes one of "none" (the default), "main", "exec" or "all". If "none",
no daemon status updates are accepted from the service processes, all status update
messages are ignored. If "main", only service updates sent from the main process of the
service are accepted. If "exec", only service updates sent from any of the main or control
processes originating from one of the "Exec*=" commands are accepted. If "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 "Type=notify" or
"WatchdogSec" (see above). If those options are used but "NotifyAccess" is not configured,
it will be implicitly set to "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 "main" or "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
"NotifyAccess""all" is set for it.

Hence, to eliminate all race conditions involving lookup of the client's unit and
attribution of notifications to units correctly, sd_notify_barrier() may be used. This
call acts as a synchronization point and ensures all notifications sent before this call
have been picked up by the service manager when it returns successfully. Use of
sd_notify_barrier() is needed for clients which are not invoked by the service manager,
otherwise this synchronization mechanism is unnecessary for attribution of notifications
to the unit. Optional. Type enum. choice: 'none', 'main', 'exec', 'all'.

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 "Service" setting of ".socket" units does not have to
match the inverse of the "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.
Note that once set, clearing the list of sockets again (for example, by assigning the
empty string to this option) is not supported. Optional. Type uniline.

FileDescriptorStoreMax
Configure how many file descriptors may be stored in the service manager for the service
using sd_pid_notify_with_fds(3)'s "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 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 (see sd_listen_fds(3) for details about the precise protocol used
and the order in which the file descriptors are passed). Any file descriptors passed to
the service manager are automatically closed when "POLLHUP" or "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, "NotifyAccess" (see above) should be set to open access to the
notification socket provided by systemd. If "NotifyAccess" is not set, it will be
implicitly set to "main". Optional. Type uniline.

USBFunctionDescriptors
Configure the location of a file containing USB FunctionFS
<https://www.kernel.org/doc/Documentation/usb/functionfs.txt> descriptors, for
implementation of USB gadget functions. This is used only in conjunction with a socket
unit with "ListenUSBFunction" configured. The contents of this file are written to the
"ep0" file after it is opened. Optional. Type uniline.

USBFunctionStrings
Configure the location of a file containing USB FunctionFS strings. Behavior is similar
to "USBFunctionDescriptors" above. Optional. Type uniline.

OOMPolicy
Configure the out-of-memory (OOM) kernel killer policy. Note that the userspace OOM killer
systemd-oomd.service(8) is a more flexible solution that aims to prevent out-of-memory
situations for the userspace, not just the kernel.

On Linux, when memory becomes scarce to the point that the kernel has trouble allocating
memory for itself, it might decide to kill a running process in order to free up memory
and reduce memory pressure. This setting takes one of "continue", "stop" or "kill". If set
to "continue" and a process of the service is killed by the kernel's OOM killer this is
logged but the service continues running. If set to "stop" the event is logged but the
service is terminated cleanly by the service manager. If set to "kill" and one of the
service's processes is killed by the OOM killer the kernel is instructed to kill all
remaining processes of the service too, by setting the "memory.oom.group" attribute to 1;
also see kernel documentation <https://www.kernel.org/doc/html/latest/admin-guide/cgroup-
v2.html>.

Defaults to the setting "DefaultOOMPolicy" in systemd-system.conf(5) is set to, except for
services where "Delegate" is turned on, where it defaults to "continue".

Use the "OOMScoreAdjust" setting to configure whether processes of the unit shall be
considered preferred or less preferred candidates for process termination by the Linux OOM
killer logic. See systemd.exec(5) for details.

This setting also applies to systemd-oomd, similar to the kernel OOM kills this setting
determines the state of the service after systemd-oomd kills a cgroup associated with the
service. Optional. Type uniline.

FailureAction
Deprecated Optional. Type uniline.

SuccessAction
Deprecated Optional. Type uniline.

StartLimitBurst
Deprecated Optional. Type uniline.

StartLimitInterval
Deprecated Optional. Type uniline.

RebootArgument
Deprecated Optional. Type uniline.

COPYRIGHT

       2010-2016 Lennart Poettering and others
       2016 Dominique Dumont

LICENSE

       LGPLv2.1+

perl v5.34.0                                Config::Model::models::Systemd::Section::Service(3pm)

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