Provided by: systemd_249.11-0ubuntu3.12_amd64 
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"). 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 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.
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=, 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.
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".
• 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 increases RLIMIT_MEMLOCK for itself, however the limit
is reverted to the original value for child processes forked off.
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.
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 image │ The operating system image │
│ │ version │ 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 │ The operating system image │
│ │ identifier │ 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 │ This is either /tmp or the │
│ │ files │ path "$TMPDIR", "$TEMP" or │
│ │ │ "$TMP" are set to. (Note │
│ │ │ that the directory may be │
│ │ │ specified without a trailing │
│ │ │ slash.) │
├──────────┼─────────────────────────────┼──────────────────────────────┤
│"%V" │ Directory for larger and │ This is either /var/tmp or │
│ │ persistent temporary files │ the path "$TMPDIR", "$TEMP" │
│ │ │ or "$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. │
└──────────┴─────────────────────────────┴──────────────────────────────┘
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