systemd-system.conf, system.conf.d, systemd-user.conf, user.conf.d - System and session service manager configuration files
/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
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.
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
RuntimeWatchdogSec=, RebootWatchdogSec=, KExecWatchdogSec=
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.
See systemd.unit(5) for details about unit names and Description=.
DefaultTimeoutStartSec=, DefaultTimeoutStopSec=, DefaultTimeoutAbortSec=, DefaultRestartSec=
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.
Simple "%"-specifier expansion is supported, see below for a list of supported specifiers.
DefaultEnvironment="VAR1=word1 word2" VAR2=word3 "VAR3=word 5 6"
Sets three variables "VAR1", "VAR2", "VAR3".
Setting environment variables for the manager process may be useful to modify its behaviour. See ENVIRONMENT 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=
DefaultLimitCPU=, DefaultLimitFSIZE=, DefaultLimitDATA=, DefaultLimitSTACK=, DefaultLimitCORE=, DefaultLimitRSS=, DefaultLimitNOFILE=, DefaultLimitAS=, DefaultLimitNPROC=, DefaultLimitMEMLOCK=, DefaultLimitLOCKS=, DefaultLimitSIGPENDING=, DefaultLimitMSGQUEUE=, DefaultLimitNICE=, DefaultLimitRTPRIO=, DefaultLimitRTTIME=
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:
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.
If the value is "/", only labels specified with SmackProcessLabel= are assigned and the compile-time default is ignored.
Specifiers may be used in the DefaultEnvironment= and ManagerEnvironment= settings. The following expansions are understood:
Table 1. Specifiers available
|"%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.)|
|"%%"||Single percent sign||Use "%%" in place of "%" to specify a single percent sign.|
systemd(1), systemd.directives(7), systemd.exec(5), systemd.service(5), environ(7), capabilities(7)
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