| SYSTEMD-SYSTEM.CONF(5) | systemd-system.conf | SYSTEMD-SYSTEM.CONF(5) |
.SH "NAME" systemd-system.conf, system.conf.d, systemd-user.conf,
user.conf.d - System and session service manager configuration files
.SH "SYNOPSIS"
.PP /etc/systemd/system.conf, /run/systemd/system.conf,
/usr/lib/systemd/system.conf, /etc/systemd/system.conf.d/*.conf,
/run/systemd/system.conf.d/*.conf, /usr/lib/systemd/system.conf.d/*.conf
.PP ~/.config/systemd/user.conf, /etc/systemd/user.conf,
/run/systemd/user.conf, /usr/lib/systemd/user.conf,
/etc/systemd/user.conf.d/*.conf, /run/systemd/user.conf.d/*.conf,
/usr/lib/systemd/user.conf.d/*.conf
.SH "DESCRIPTION"
.PP When run as a system instance, systemd interprets the
configuration file system.conf and the files in system.conf.d directories;
when run as a user instance, it interprets the configuration file user.conf
(in order of priority, in the home directory of the user and under
/etc/systemd/, /run/systemd/, and /usr/lib/systemd/) and the files in
user.conf.d directories. These configuration files contain a few settings
controlling basic manager operations.
.PP See systemd.syntax(7) for a general description of the syntax.
.SH "CONFIGURATION DIRECTORIES AND PRECEDENCE"
.PP The default configuration is set during compilation, so configuration is
only needed when it is necessary to deviate from those defaults. The main
configuration file is loaded from one of the listed directories in order of
priority, only the first file found is used: /etc/systemd/, /run/systemd/,
/usr/local/lib/systemd/ [1], /usr/lib/systemd/. The vendor version of the
file contains commented out entries showing the defaults as a guide to the
administrator. Local overrides can also be created by creating drop-ins, as
described below. The main configuration file can also be edited for this
purpose (or a copy in /etc/ if it is shipped under /usr/), however using
drop-ins for local configuration is recommended over modifications to the
main configuration file.
.PP In addition to the main configuration file, drop-in configuration
snippets are read from /usr/lib/systemd/*.conf.d/,
/usr/local/lib/systemd/*.conf.d/, and /etc/systemd/*.conf.d/. Those drop-ins
have higher precedence and override the main configuration file. Files in
the *.conf.d/ configuration subdirectories are sorted by their filename in
lexicographic order, regardless of in which of the subdirectories they
reside. When multiple files specify the same option, for options which
accept just a single value, the entry in the file sorted last takes
precedence, and for options which accept a list of values, entries are
collected as they occur in the sorted files.
.PP When packages need to customize the configuration, they can install
drop-ins under /usr/. Files in /etc/ are reserved for the local
administrator, who may use this logic to override the configuration files
installed by vendor packages. Drop-ins have to be used to override package
drop-ins, since the main configuration file has lower precedence. It is
recommended to prefix all filenames in those subdirectories with a two-digit
number and a dash, to simplify the ordering. This also defines a concept of
drop-in priorities to allow OS vendors to ship drop-ins within a specific
range lower than the range used by users. This should lower the risk of
package drop-ins overriding accidentally drop-ins defined by users. It is
recommended to use the range 10-40 for drop-ins in /usr/ and the range 60-90
for drop-ins in /etc/ and /run/, to make sure that local and transient
drop-ins take priority over drop-ins shipped by the OS vendor.
.PP To disable a configuration file supplied by the vendor, the recommended
way is to place a symlink to /dev/null in the configuration directory in
/etc/, with the same filename as the vendor configuration file.
.SH "OPTIONS"
.PP All options are configured in the [Manager] section:
.PP LogColor=, LogLevel=, LogLocation=,
LogTarget=, LogTime=, DumpCore=yes,
CrashChangeVT=no, CrashShell=no, CrashAction=freeze,
ShowStatus=yes, DefaultStandardOutput=journal,
DefaultStandardError=inherit
Configures various parameters of basic manager operation. These options may
be overridden by the respective process and kernel command line arguments.
See systemd(1) for details.
Added in version 198.
.RE
.PP CtrlAltDelBurstAction=
Defines what action will be performed if user presses Ctrl-Alt-Delete more
than 7 times in 2s. Can be set to reboot-force, poweroff-force,
reboot-immediate, poweroff-immediate or disabled with none. Defaults to
reboot-force.
Added in version 232.
.RE
.PP StatusUnitFormat=
Takes name, description or combined as the value. If
name, the system manager will use unit names in status messages (e.g.
systemd-journald.service), instead of the longer and more informative
descriptions set with Description= (e.g. Journal Logging Service). If
combined, the system manager will use both unit names and
descriptions in status messages (e.g. systemd-journald.service - Journal
Logging Service).
See systemd.unit(5) for details about unit names and
Description=.
Added in version 243.
.RE
.PP DefaultTimerAccuracySec=
Sets the default accuracy of timer units. This controls the global default
for the AccuracySec= setting of timer units, see
systemd.timer(5) for details. AccuracySec= set in individual
units override the global default for the specific unit. Defaults to 1min.
Note that the accuracy of timer units is also affected by the configured
timer slack for PID 1, see TimerSlackNSec= above.
Added in version 212.
.RE
.SH "RESOURCE MANAGEMENT"
.PP TimerSlackNSec=
Sets the timer slack in nanoseconds for PID 1, which is inherited by all
executed processes, unless overridden individually, for example with the
TimerSlackNSec= setting in service units (for details see
systemd.exec(5)). The timer slack controls the accuracy of wake-ups
triggered by system 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.
Added in version 198.
.RE
.PP CPUAffinity=
Configures the CPU affinity for the service manager as well as the default
CPU affinity for all forked off processes. Takes a list of CPU indices or
ranges separated by either whitespace or commas. CPU ranges are specified by
the lower and upper CPU indices separated by a dash. This option may be
specified more than once, in which case the specified CPU affinity masks are
merged. If the empty string is assigned, the mask is reset, all assignments
prior to this will have no effect. Individual services may override the CPU
affinity for their processes with the CPUAffinity= setting in unit
files, see systemd.exec(5).
Added in version 198.
.RE
.PP NUMAPolicy=
Configures the NUMA memory policy for the service manager and the default
NUMA memory policy for all forked off processes. Individual services may
override the default policy with the NUMAPolicy= setting in unit
files, see systemd.exec(5).
Added in version 243.
.RE
.PP NUMAMask=
Configures the NUMA node mask that will be associated with the selected NUMA
policy. Note that default and local NUMA policies do not
require explicit NUMA node mask and value of the option can be empty.
Similarly to NUMAPolicy=, value can be overridden by individual
services in unit files, see systemd.exec(5).
Added in version 243.
.RE
.PP DefaultMemoryAccounting=, DefaultTasksAccounting=,
DefaultIOAccounting=, DefaultIPAccounting=
Configure the default resource accounting settings, as configured per-unit by
MemoryAccounting=, TasksAccounting=, IOAccounting=, and
IPAccounting=. See systemd.resource-control(5) for details on
the per-unit settings.
DefaultMemoryAccounting= defaults to yes.
DefaultTasksAccounting= defaults to yes. The other settings default
to no.
Added in version 211.
.RE
.PP DefaultTasksMax=
Configure the default value for the per-unit TasksMax= setting. See
systemd.resource-control(5) for details. This setting applies to all
unit types that support resource control settings, with the exception of
slice units. Defaults to 15% of the minimum of kernel.pid_max=,
kernel.threads-max= and root cgroup pids.max. Kernel has a
default value for kernel.pid_max= and an algorithm of counting in
case of more than 32 cores. For example, with the default
kernel.pid_max=, DefaultTasksMax= defaults to 4915, but might
be greater in other systems or smaller in OS containers.
Added in version 228.
.RE
.PP DefaultLimitCPU=, DefaultLimitFSIZE=,
DefaultLimitDATA=, DefaultLimitSTACK=,
DefaultLimitCORE=, DefaultLimitRSS=,
DefaultLimitNOFILE=, DefaultLimitAS=,
DefaultLimitNPROC=, DefaultLimitMEMLOCK=,
DefaultLimitLOCKS=, DefaultLimitSIGPENDING=,
DefaultLimitMSGQUEUE=, DefaultLimitNICE=,
DefaultLimitRTPRIO=, DefaultLimitRTTIME=
These settings control various default resource limits for processes executed
by units. See setrlimit(2) for details. These settings may be
overridden in individual units using the corresponding LimitXXX=
directives and they accept the same parameter syntax, see
systemd.exec(5) for details. Note that these resource limits are only
defaults for units, they are not applied to the service manager process
(i.e. PID 1) itself.
Most of these settings are unset, which means the resource limits are
inherited from the kernel or, if invoked in a container, from the container
manager. However, the following have defaults:
.sp
Note that the service manager internally in PID 1 bumps RLIMIT_NOFILE
and RLIMIT_MEMLOCK to higher values, however the limit is reverted to
the mentioned defaults for all child processes forked off.
Added in version 198.
.RE
.PP DefaultOOMPolicy=
Configure the default policy for reacting to processes being killed by the
Linux Out-Of-Memory (OOM) killer or systemd-oomd. This may be used to
pick a global default for the per-unit OOMPolicy= setting. See
systemd.service(5) for details. Note that this default is not used
for services that have Delegate= turned on.
Added in version 243.
.RE
.PP DefaultOOMScoreAdjust=
Configures the default OOM score adjustments of processes run by the service
manager. This defaults to unset (meaning the forked off processes inherit
the service manager's OOM score adjustment value), except if the service
manager is run for an unprivileged user, in which case this defaults to the
service manager's OOM adjustment value plus 100 (this makes service
processes slightly more likely to be killed under memory pressure than the
manager itself). This may be used to pick a global default for the per-unit
OOMScoreAdjust= setting. See systemd.exec(5) for details. Note
that this setting has no effect on the OOM score adjustment value of the
service manager process itself, it retains the original value set during its
invocation.
Added in version 250.
.RE
.PP DefaultMemoryPressureWatch=,
DefaultMemoryPressureThresholdSec=
Configures the default settings for the per-unit MemoryPressureWatch=
and MemoryPressureThresholdSec= settings. See
systemd.resource-control(5) for details. Defaults to auto and 200ms,
respectively. This also sets the memory pressure monitoring threshold for
the service manager itself.
Added in version 254.
.RE
.PP DefaultCPUPressureWatch=,
DefaultCPUPressureThresholdSec=
Configures the default settings for the per-unit CPUPressureWatch= and
CPUPressureThresholdSec= settings. See
systemd.resource-control(5) for details. Defaults to auto and 200ms,
respectively. This also sets the CPU pressure monitoring threshold for the
service manager itself.
Added in version 261.
.RE
.PP DefaultIOPressureWatch=, DefaultIOPressureThresholdSec=
Configures the default settings for the per-unit IOPressureWatch= and
IOPressureThresholdSec= settings. See
systemd.resource-control(5) for details. Defaults to auto and 200ms,
respectively. This also sets the IO pressure monitoring threshold for the
service manager itself.
Added in version 261.
.RE
.SH "HARDWARE WATCHDOG"
.PP RuntimeWatchdogSec=, RebootWatchdogSec=,
KExecWatchdogSec=
Configure the hardware watchdog at runtime and at reboot. Takes a timeout
value in seconds (or in other time units if suffixed with ms, min, h, d, w),
or the special strings off or default. If set to off (alternatively: 0) the
watchdog logic is disabled: no watchdog device is opened, configured, or
pinged. If set to the special string default the watchdog is opened and
pinged in regular intervals, but the timeout is not changed from the
default. If set to any other time value the watchdog timeout is configured
to the specified value (or a value close to it, depending on hardware
capabilities).
If RuntimeWatchdogSec= is set to a non-zero value, the watchdog
hardware (/dev/watchdog0 or the path specified with WatchdogDevice=
or the kernel option systemd.watchdog_device=) will be programmed to
automatically reboot the system if it is not contacted within the specified
timeout interval. The system manager will ensure to contact it at least once
in half the specified timeout interval. This feature requires a hardware
watchdog device to be present, as it is commonly the case in embedded and
server systems. Not all hardware watchdogs allow configuration of all
possible reboot timeout values, in which case the closest available timeout
is picked.
RebootWatchdogSec= may be used to configure the hardware watchdog when
the system is asked to reboot. It works as a safety net to ensure that the
reboot takes place even if a clean reboot attempt times out. Note that the
RebootWatchdogSec= timeout applies only to the second phase of the
reboot, i.e. after all regular services are already terminated, and after
the system and service manager process (PID 1) got replaced by the
systemd-shutdown binary, see system bootup(7) for details. During the
first phase of the shutdown operation the system and service manager remains
running and hence RuntimeWatchdogSec= is still honoured. In order to
define a timeout on this first phase of system shutdown, configure
JobTimeoutSec= and JobTimeoutAction= in the [Unit] section of
the shutdown.target unit. By default, RuntimeWatchdogSec= defaults to
0 (off), and RebootWatchdogSec= to 10min.
KExecWatchdogSec= may be used to additionally enable the watchdog when
kexec is being executed rather than when rebooting. Note that if the kernel
does not reset the watchdog on kexec (depending on the specific hardware
and/or driver), in this case the watchdog might not get disabled after kexec
succeeds and thus the system might get rebooted, unless
RuntimeWatchdogSec= is also enabled at the same time. For this reason
it is recommended to enable KExecWatchdogSec= only if
RuntimeWatchdogSec= is also enabled.
These settings have no effect if a hardware watchdog is not available.
Added in version 198.
.RE
.PP RuntimeWatchdogPreSec=
Configure the hardware watchdog device pre-timeout value. Takes a timeout
value in seconds (or in other time units similar to
RuntimeWatchdogSec=). A watchdog pre-timeout is a notification
generated by the watchdog before the watchdog reset might occur in the event
the watchdog has not been serviced. This notification is handled by the
kernel and can be configured to take an action (i.e. generate a kernel
panic) using RuntimeWatchdogPreGovernor=. Not all watchdog hardware
or drivers support generating a pre-timeout and depending on the state of
the system, the kernel may be unable to take the configured action before
the watchdog reboot. The watchdog will be configured to generate the
pre-timeout event at the amount of time specified by
RuntimeWatchdogPreSec= before the runtime watchdog timeout (set by
RuntimeWatchdogSec=). For example, if the we have
RuntimeWatchdogSec=30 and RuntimeWatchdogPreSec=10, then the
pre-timeout event will occur if the watchdog has not pinged for 20s (10s
before the watchdog would fire). By default, RuntimeWatchdogPreSec=
defaults to 0 (off). The value set for RuntimeWatchdogPreSec= must be
smaller than the timeout value for RuntimeWatchdogSec=. This setting
has no effect if a hardware watchdog is not available or the hardware
watchdog does not support a pre-timeout and will be ignored by the kernel if
the setting is greater than the actual watchdog timeout.
Added in version 251.
.RE
.PP RuntimeWatchdogPreGovernor=
Configure the action taken by the hardware watchdog device when the
pre-timeout expires. The default action for the pre-timeout event depends on
the kernel configuration, but it is usually to log a kernel message. For a
list of valid actions available for a given watchdog device, check the
content of the
/sys/class/watchdog/watchdogX/pretimeout_available_governors file.
Typically, available governor types are noop and panic.
Availability, names and functionality might vary depending on the specific
device driver in use. If the pretimeout_available_governors sysfs file is
empty, the governor might be built as a kernel module and might need to be
manually loaded (e.g. pretimeout_noop.ko), or the watchdog device
might not support pre-timeouts.
Added in version 251.
.RE
.PP WatchdogDevice=
Configure the hardware watchdog device that the runtime and shutdown watchdog
timers will open and use. Defaults to /dev/watchdog0. This setting has no
effect if a hardware watchdog is not available.
Added in version 236.
.RE
.SH "SECURITY"
.PP CapabilityBoundingSet=
Controls which capabilities to include in the capability bounding set for PID
1 and its children. See capabilities(7) for details. Takes a
whitespace-separated list of capability names as read by
cap_from_name(3). 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. The capability bounding set may also be individually
configured for units using the CapabilityBoundingSet= directive for
units, but note that capabilities dropped for PID 1 cannot be regained in
individual units, they are lost for good.
Added in version 198.
.RE
.PP NoNewPrivileges=
Takes a boolean argument. If true, ensures that PID 1 and all its children
can never gain new privileges through execve(2) (e.g. via setuid or
setgid bits, or filesystem capabilities). Defaults to false. General purpose
distributions commonly rely on executables with setuid or setgid bits and
will thus not function properly with this option enabled. Individual units
cannot disable this option. Also see No New Privileges Flag[2].
Added in version 239.
.RE
.PP ProtectSystem=
Takes a boolean argument or the string auto. If set to true this will remount
/usr/ read-only. If set to auto (the default) and running in an initrd
equivalent to true, otherwise false. This implements a restricted subset of
the per-unit setting of the same name, see systemd.exec(5) for
details: currently, the full or strict values are not supported.
Added in version 256.
.RE
.PP RestrictFileSystemAccess=
Takes a boolean argument or the special value exec. Defaults to no. When
enabled, PID 1 loads a BPF LSM program that enforces a deny-default
execution policy: only binaries residing on signed dm-verity block devices
(and the initramfs during early boot) are permitted to execute. Execution
from tmpfs, procfs, sysfs, unsigned dm-verity devices, and anonymous
executable memory mappings is denied.
This setting is intended as one component of an image-based, fully verified
system, where the whole boot chain (firmware, kernel image, kernel command
line, initramfs) is measured and attested. On a general-purpose system
without such guarantees it does not provide a meaningful security boundary
on its own: an attacker with sufficient privilege to edit system.conf,
modify the kernel command line, or kexec into an unsigned initrd can disable
or bypass the policy.
The enforcement hooks block execve() of untrusted binaries
(bprm_check_security), PROT_EXEC memory mappings including shared
libraries (mmap_file), and write-to-execute transitions such as JIT
compilation (file_mprotect).
The policy also enforces W^X system-wide: no mapping may be writable and
executable at the same time, and a private file mapping that has been
modified through copy-on-write may not be made executable afterwards.
Since v262, files on overlayfs mounts are resolved to the layer that hosts
their data, so execution from an overlay whose data resides on a signed
dm-verity device is permitted, while files in a writable upper layer are
denied. This requires kernel v7.2 or newer; on older kernels execution from
overlayfs mounts is denied entirely. Note that only the file data is
checked, so an untrusted upper layer may still control a binary's ownership
and setuid bits. Multi-device filesystems such as btrfs are unsupported.
Note that, without further measures to secure the system, kexec can be used
to circumvent this.
This requires the kernel to be booted with dm_verity.require_signatures=1 and
proc_mem.force_override=never on the kernel command line, and with BPF LSM
enabled (lsm=...,bpf).
The value yes is equivalent to exec. Additional modes may be added in the
future.
This option may also be set via the
systemd.restrict_filesystem_access= kernel command line option, see
kernel-command-line(7).
Added in version 261.
.RE
.PP SystemCallArchitectures=
Takes a space-separated list of architecture identifiers. Selects from which
architectures system calls may be invoked on this system. This may be used
as an effective way to disable invocation of non-native binaries
system-wide, for example to prohibit execution of 32-bit x86 binaries on
64-bit x86-64 systems. This option operates system-wide, and acts similar to
the SystemCallArchitectures= setting of unit files, see
systemd.exec(5) for details. This setting defaults to the empty list,
in which case no filtering of system calls based on architecture is applied.
Known architecture identifiers are x86, x86-64, x32, arm and the special
identifier native. The latter implicitly maps to the native architecture of
the system (or more specifically, the architecture the system manager was
compiled for). Set this setting to native to prohibit execution of any
non-native binaries. When a binary executes a system call of an architecture
that is not listed in this setting, it will be immediately terminated with
the SIGSYS signal.
Added in version 209.
.RE
.PP DefaultSmackProcessLabel=
Takes a SMACK64 security label as the argument. The process executed
by a unit will be started under this label if SmackProcessLabel= is
not set in the unit. See systemd.exec(5) for the details.
If the value is /, only labels specified with SmackProcessLabel= are
assigned and the compile-time default is ignored.
Added in version 252.
.RE
.PP DefaultRestrictSUIDSGID=
Takes a boolean argument. This is used as a default for units which lack an
explicit definition for RestrictSUIDSGID=. See systemd.exec(5)
for the details.
Added in version 258.
.RE
.SH "TIMEOUTS AND RATE LIMITS"
.PP DefaultTimeoutStartSec=, DefaultTimeoutStopSec=,
DefaultTimeoutAbortSec=, DefaultRestartSec=
Configures the default timeouts for starting, stopping and aborting of units,
as well as the default time to sleep between automatic restarts of units, as
configured per-unit in TimeoutStartSec=, TimeoutStopSec=,
TimeoutAbortSec= and RestartSec= (for services, see
systemd.service(5) for details on the per-unit settings). For
non-service units, DefaultTimeoutStartSec= sets the default
TimeoutSec= value.
DefaultTimeoutStartSec= and DefaultTimeoutStopSec= default to
90 s in the system manager and 90 s in the user manager.
DefaultTimeoutAbortSec= is not set by default so that all units fall
back to TimeoutStopSec=. DefaultRestartSec= defaults to 100
ms.
Added in version 209.
.RE
.PP DefaultDeviceTimeoutSec=
Configures the default timeout for waiting for devices. It can be changed per
device via the x-systemd.device-timeout= option in /etc/fstab and
/etc/crypttab (see systemd.mount(5), crypttab(5)). Defaults to
90 s in the system manager and 90 s in the user manager.
Added in version 252.
.RE
.PP DefaultStartLimitIntervalSec=, DefaultStartLimitBurst=
Configure the default unit start rate limiting, as configured per-service by
StartLimitIntervalSec= and StartLimitBurst=. See
systemd.service(5) for details on the per-service settings.
DefaultStartLimitIntervalSec= defaults to 10s.
DefaultStartLimitBurst= defaults to 5.
Added in version 209.
.RE
.PP ReloadLimitIntervalSec=, ReloadLimitBurst=
Rate limiting for daemon-reload and (since v256) daemon-reexec requests. The
setting applies to both operations, but the rate limits are tracked
separately. Defaults to unset, and any number of operations can be requested
at any time. ReloadLimitIntervalSec= takes a value in seconds to
configure the rate limit window, and ReloadLimitBurst= takes a
positive integer to configure the maximum allowed number of operations
within the configured time window.
Added in version 253.
.RE
.PP EventLoopRateLimitIntervalSec=,
EventLoopRateLimitBurst=
Configures the rate limiting applied to the manager's main event loop. If the
event loop iterates more than EventLoopRateLimitBurst= times within
EventLoopRateLimitIntervalSec=, event processing is briefly paused to
prevent excessive CPU usage. EventLoopRateLimitIntervalSec= defaults
to 1s. EventLoopRateLimitBurst= defaults to 50000. These settings can
also be set on the kernel command line via
systemd.event_loop_ratelimit_interval_sec= and
systemd.event_loop_ratelimit_burst=.
Added in version 261.
.RE
.PP MinimumUptimeSec=
Specifies the minimum uptime for the system which has to be reached before a
shutdown is executed. Defaults to 15s. This mechanism is introduced to avoid
high frequency reboot loops, when technical failures trigger an automatic
shutdown during the boot process. Each reboot cycle is delayed to the
specified minimum time, giving the user a chance to review screen contents
or otherwise interact with the device before the shutdown proceeds. The
delay takes place during the very last phase of system shutdown, immediately
before the reboot() system call is executed. If the system is already
running for longer than the specified time, this setting has no effect. This
logic is also skipped in container environments. Set to zero in order to
disable this logic.
Added in version 261.
.RE
.SH "ENVIRONMENT"
.PP DefaultEnvironment=
Configures environment variables passed to all executed processes. Takes a
space-separated list of variable assignments. See environ(7) for
details about environment variables. This environment block is internal, and
changes are not reflected in the manager's /proc/PID/environ.
Simple %-specifier expansion is supported, see below for a list of supported
specifiers.
Example:
DefaultEnvironment="VAR1=word1 word2" VAR2=word3 "VAR3=word 5 6"
Sets three variables VAR1, VAR2, VAR3.
Added in version 205.
.RE
.PP ManagerEnvironment=
Sets environment variables for the manager process itself. Takes a
space-separated list of variable assignment in the same format as
DefaultEnvironment=, see above. These variables are merged into the
existing environment block of the manager process. In particular, in case of
the system manager, this block includes variables set by the kernel based on
the kernel command line, and in case of the user manager, the variables
passed by the system manager. After those variables have been merged, they
will persist until overridden, even if the manager is reloaded or
reexecuted. In case of the user manager, these variables are also inherited
by processes spawned by the manager. As with DefaultEnvironment=,
this environment block is internal, and changes are not reflected in the
manager's /proc/PID/environ.
Setting environment variables for the manager process may be useful to modify
its behaviour. See Known Environment Variables[3] for a description
of some variables understood by systemd.
Simple %-specifier expansion is supported, see below for a list of supported
specifiers.
Added in version 248.
.RE
.PP DefaultMemoryZSwapWriteback=
Takes a boolean argument. Defaults to true if unspecified. This is used as a
default for units which lack an explicit definition for
MemoryZSwapWriteback=. See systemd.resource-control(5) for the
details.
Added in version 261.
.RE
.SH "SPECIFIERS"
.PP Specifiers may be used in the DefaultEnvironment= and
ManagerEnvironment= settings. The following expansions are
understood:
.sp
Table 1. Specifiers available
| Specifier | Meaning | Details |
| %a | Architecture | A short string identifying the architecture of the local system. A string such as x86, x86-64 or arm64. See the architectures defined for ConditionArchitecture= in systemd.unit(5) for a full list. |
| %A | Operating system image version | The operating system image version identifier of the running system, as read from the IMAGE_VERSION= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
| %b | Boot ID | The boot ID of the running system, formatted as string. See random(4) for more information. |
| %B | Operating system build ID | The operating system build identifier of the running system, as read from the BUILD_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
| %H | Host name | The hostname of the running system. |
| %l | Short host name | The hostname of the running system, truncated at the first dot to remove any domain component. |
| %m | Machine ID | The machine ID of the running system, formatted as string. See machine-id(5) for more information. |
| %M | Operating system image identifier | The operating system image identifier of the running system, as read from the IMAGE_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
| %o | Operating system ID | The operating system identifier of the running system, as read from the ID= field of /etc/os-release. See os-release(5) for more information. |
| %v | Kernel release | Identical to uname -r output. |
| %w | Operating system version ID | The operating system version identifier of the running system, as read from the VERSION_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
| %W | Operating system variant ID | The operating system variant identifier of the running system, as read from the VARIANT_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
| %T | Directory for temporary files | This is either /tmp or the path $TMPDIR, $TEMP or $TMP are set to. (Note that the directory may be specified without a trailing slash.) |
| %V | Directory for larger and persistent temporary files | This is either /var/tmp or the path $TMPDIR, $TEMP or $TMP are set to. (Note that the directory may be specified without a trailing slash.) |
| %h | User home directory | This is the home directory of the user running the service manager instance. |
| %u | Username | This is the username of the user running the service manager instance. |
| %U | User id | This is the user id of the user running the service manager instance. |
| %g | Primary group | This is the primary group of the user running the service manager instance. |
| %G | Primary group id | This is the primary group id of the user running the service manager instance. |
| %s | User shell | This is the shell of the user running the service manager instance. |
| %% | Single percent sign | Use %% in place of % to specify a single percent sign. |
.SH "HISTORY"
.PP systemd 252
Option DefaultBlockIOAccounting= was deprecated. Please switch to the
unified cgroup hierarchy.
.RE
.PP systemd 258
DefaultCPUAccounting= setting is deprecated, because CPU accounting is
always available on the unified cgroup hierarchy and such setting has no
effect.
.RE
.SH "SEE ALSO"
.PP systemd(1), systemd.directives(7), systemd.exec(5),
systemd.service(5), environ(7), capabilities(7)
NOTES
- 1.
-
💣💥🧨💥💥💣 Please note that those configuration files must be available at all times. If /usr/local/ is a separate partition, it may not be available during early boot, and must not be used for configuration. - 2.
- No New Privileges Flag
- 3.
- Known Environment Variables
| systemd 262.2 |