SYSTEMD-SYSTEM.CONF(5) systemd-system.conf SYSTEMD-SYSTEM.CONF(5)
NAME
systemd-system.conf, system.conf.d, systemd-user.conf, user.conf.d -
System and session service manager configuration files
SYNOPSIS
/etc/systemd/system.conf, /etc/systemd/system.conf.d/*.conf,
/run/systemd/system.conf.d/*.conf, /lib/systemd/system.conf.d/*.conf
~/.config/systemd/user.conf, /etc/systemd/user.conf,
/etc/systemd/user.conf.d/*.conf, /run/systemd/user.conf.d/*.conf,
/usr/lib/systemd/user.conf.d/*.conf
DESCRIPTION
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
(either in the home directory of the user, or if not found, under
/etc/systemd/) and the files in user.conf.d directories. These
configuration files contain a few settings controlling basic manager
operations.
See systemd.syntax(7) for a general description of the syntax.
CONFIGURATION DIRECTORIES AND PRECEDENCE
The default configuration is set during compilation, so configuration
is only needed when it is necessary to deviate from those defaults.
Initially, the main configuration file in /etc/systemd/ contains
commented out entries showing the defaults as a guide to the
administrator. Local overrides can be created by editing this file or
by creating drop-ins, as described below. Using drop-ins for local
configuration is recommended over modifications to the main
configuration file.
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.
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 of the files.
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.
OPTIONS
All options are configured in the [Manager] section:
LogColor=, LogLevel=, LogLocation=, LogTarget=, LogTime=, DumpCore=yes,
CrashChangeVT=no, CrashShell=no, CrashReboot=no, 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.
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".
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).
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).
NUMAMask=
Configures the NUMA node mask that will be associated with the
selected NUMA policy. Note that default and local NUMA policies
don't 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).
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.
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.
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.
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.
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.
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[1].
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.
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.
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=.
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.
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).
Disabled by default, when service with Type=oneshot is used. For
non-service units, DefaultTimeoutStartSec= sets the default
TimeoutSec= value. DefaultTimeoutStartSec= and
DefaultTimeoutStopSec= default to 90s. DefaultTimeoutAbortSec= is
not set by default so that all units fall back to TimeoutStopSec=.
DefaultRestartSec= defaults to 100ms.
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 90s.
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.
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.
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".
ManagerEnvironment=
Takes the same arguments as DefaultEnvironment=, see above. Sets
environment variables just for the manager process itself. In
contrast to user managers, these variables are not inherited by
processes spawned by the system manager, use DefaultEnvironment=
for that. Note that these variables are merged into the existing
environment block. In particular, in case of the system manager,
this includes variables set by the kernel based on the kernel
command line.
Setting environment variables for the manager process may be useful
to modify its behaviour. See ENVIRONMENT[2] for a descriptions of
some variables understood by systemd.
Simple "%"-specifier expansion is supported, see below for a list
of supported specifiers.
DefaultCPUAccounting=, DefaultMemoryAccounting=,
DefaultTasksAccounting=, DefaultIOAccounting=, DefaultIPAccounting=
Configure the default resource accounting settings, as configured
per-unit by CPUAccounting=, MemoryAccounting=, TasksAccounting=,
IOAccounting= and IPAccounting=. See systemd.resource-control(5)
for details on the per-unit settings. DefaultTasksAccounting=
defaults to yes, DefaultMemoryAccounting= to yes.
DefaultCPUAccounting= defaults to yes, but really has no effect if
enabling CPU accounting doesn't require the cpu controller to be
enabled (Linux 4.15+ using the unified hierarchy for resource
control), otherwise it defaults to no. The other three settings
default to no.
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.
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:
• DefaultLimitNOFILE= defaults to 1024:524288.
• DefaultLimitMEMLOCK= defaults to 8M.
• DefaultLimitCORE= does not have a default but it is worth
mentioning that RLIMIT_CORE is set to "infinity" by PID 1 which
is inherited by its children.
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.
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.
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.
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.
SPECIFIERS
Specifiers may be used in the DefaultEnvironment= and
ManagerEnvironment= settings. The following expansions are understood:
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 │ The operating system │
│ │ image version │ 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 │ The operating system │
│ │ build ID │ 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 │ The operating system │
│ │ image identifier │ 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 │ The operating system │
│ │ version ID │ 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 │ The operating system │
│ │ variant ID │ 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 │ This is either /tmp or │
│ │ temporary files │ the path "$TMPDIR", │
│ │ │ "$TEMP" or "$TMP" are │
│ │ │ set to. (Note that the │
│ │ │ directory may be │
│ │ │ specified without a │
│ │ │ trailing slash.) │
├──────────┼─────────────────────┼────────────────────────┤
│"%V" │ Directory for │ This is either │
│ │ larger and │ /var/tmp or the path │
│ │ persistent │ "$TMPDIR", "$TEMP" or │
│ │ temporary files │ "$TMP" are set to. │
│ │ │ (Note that the │
│ │ │ directory may be │
│ │ │ specified without a │
│ │ │ trailing slash.) │
├──────────┼─────────────────────┼────────────────────────┤
│"%%" │ Single percent sign │ Use "%%" in place of │
│ │ │ "%" to specify a │
│ │ │ single percent sign. │
└──────────┴─────────────────────┴────────────────────────┘
HISTORY
systemd 252
Option DefaultBlockIOAccounting= was deprecated. Please switch to
the unified cgroup hierarchy.
SEE ALSO
systemd(1), systemd.directives(7), systemd.exec(5), systemd.service(5),
environ(7), capabilities(7)
NOTES
1. No New Privileges Flag
https://docs.kernel.org/userspace-api/no_new_privs.html
2. ENVIRONMENT
https://systemd.io/ENVIRONMENT
systemd 252 SYSTEMD-SYSTEM.CONF(5)
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