SYSTEMD\-SYSTEM\&.CONF
Section: systemd-system.conf (5)
Updated:
Page Index
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,
/usr/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"). If
RuntimeWatchdogSec=
is set to a non-zero value, the watchdog hardware (/dev/watchdog
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.
WatchdogDevice=
-
Configure the hardware watchdog device that the runtime and shutdown watchdog timers will open and use. Defaults to
/dev/watchdog. 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
m[blue]No New Privileges Flagm[][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 either
name
or
description
as the value. If
name, the system manager will use unit names in status messages, instead of the longer and more informative descriptions set with
Description=, see
systemd.unit(5).
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.
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.
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. These variables are not inherited by processes spawned by the service 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
m[blue]ENVIRONMENTm[][2]
for a descriptions of some variables understood by
systemd.
DefaultCPUAccounting=, DefaultBlockIOAccounting=, DefaultMemoryAccounting=, DefaultTasksAccounting=, DefaultIOAccounting=, DefaultIPAccounting=
-
Configure the default resource accounting settings, as configured per-unit by
CPUAccounting=,
BlockIOAccounting=,
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 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.
DefaultOOMPolicy=
-
Configure the default policy for reacting to processes being killed by the Linux Out-Of-Memory (OOM) killer. 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.
SEE ALSO
systemd(1),
systemd.directives(7),
systemd.exec(5),
systemd.service(5),
environ(7),
capabilities(7)
NOTES
- 1.
-
No New Privileges Flag
-
https://www.kernel.org/doc/html/latest/userspace-api/no_new_privs.html
- 2.
-
ENVIRONMENT
-
https://systemd.io/ENVIRONMENT