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 /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, systemd interprets the configuration file user.conf and the files in user.conf.d directories. These configuration files contain a few settings controlling basic manager operations.
CONFIGURATION DIRECTORIES AND PRECEDENCE
The default configuration is defined during compilation, so a configuration file is only needed when it is necessary to deviate from those defaults. By default, the configuration file in /etc/systemd/ contains commented out entries showing the defaults as a guide to the administrator. This file can be edited to create local overrides. When packages need to customize the configuration, they can install configuration snippets in /usr/lib/systemd/*.conf.d/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. The main configuration file is read before any of the configuration directories, and has the lowest precedence; entries in a file in any configuration directory override entries in the single configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of which of the subdirectories they reside in. If multiple files specify the same option, the entry in the file with the lexicographically latest name takes 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:
LogLevel=, LogTarget=, LogColor=, LogLocation=, 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 command line arguments.
See systemd(1) for details about these command line arguments.
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 initial CPU affinity for the init process. 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.
JoinControllers=cpu,cpuacct net_cls,netprio
Configures controllers that shall be mounted in a single hierarchy.
By default, systemd will mount all controllers which are enabled in
the kernel in individual hierarchies, with the exception of those
listed in this setting. Takes a space-separated list of
comma-separated controller names, in order to allow multiple joined
hierarchies. Defaults to 'cpu,cpuacct'. Pass an empty string to
ensure that systemd mounts all controllers in separate hierarchies.
Note that this option is only applied once, at very early boot. If
you use an initial RAM disk (initrd) that uses systemd, it might
hence be necessary to rebuild the initrd if this option is changed,
and make sure the new configuration file is included in it.
Otherwise, the initrd might mount the controller hierarchies in a
different configuration than intended, and the main system cannot
remount them anymore.
RuntimeWatchdogSec=, ShutdownWatchdogSec=
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) 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 the
reboot timeout, in which case the closest available timeout is
picked. ShutdownWatchdogSec= 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. By default RuntimeWatchdogSec= defaults to 0
(off), and ShutdownWatchdogSec= to 10min. These settings have 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.
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.
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=, DefaultRestartSec=
Configures the default timeouts for starting and stopping of units,
as well as the default time to sleep between automatic restarts of
units, as configured per-unit in TimeoutStartSec=, TimeoutStopSec=
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 90s.
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=
Sets manager 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".
DefaultCPUAccounting=, DefaultBlockIOAccounting=,
DefaultMemoryAccounting=, DefaultTasksAccounting=
Configure the default resource accounting settings, as configured
per-unit by CPUAccounting=, BlockIOAccounting=, MemoryAccounting=
and TasksAccounting=. See systemd.resource-control(5) for details
on the per-unit settings. DefaultTasksAccounting= defaults to on,
the other three settings to off.
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.
DefaultLimitCPU=, DefaultLimitFSIZE=, DefaultLimitDATA=,
DefaultLimitSTACK=, DefaultLimitCORE=, DefaultLimitRSS=,
DefaultLimitNOFILE=, DefaultLimitAS=, DefaultLimitNPROC=,
DefaultLimitMEMLOCK=, DefaultLimitLOCKS=, DefaultLimitSIGPENDING=,
DefaultLimitMSGQUEUE=, DefaultLimitNICE=, DefaultLimitRTPRIO=,
DefaultLimitRTTIME=
These settings control various default resource limits for units.
See setrlimit(2) for details. The resource limit is possible to
specify in two formats, value to set soft and hard limits to the
same value, or soft:hard to set both limits individually (e.g.
DefaultLimitAS=4G:16G). Use the string infinity to configure no
limit on a specific resource. The multiplicative suffixes K
(=1024), M (=1024*1024) and so on for G, T, P and E may be used for
resource limits measured in bytes (e.g. DefaultLimitAS=16G). For
the limits referring to time values, the usual time units ms, s,
min, h and so on may be used (see systemd.time(7) for details).
Note that if no time unit is specified for DefaultLimitCPU= the
default unit of seconds is implied, while for DefaultLimitRTTIME=
the default unit of microseconds is implied. Also, note that the
effective granularity of the limits might influence their
enforcement. For example, time limits specified for
DefaultLimitCPU= will be rounded up implicitly to multiples of 1s.
These settings may be overridden in individual units using the
corresponding LimitXXX= directives. Note that these resource limits
are only defaults for units, they are not applied to PID 1 itself.
SEE ALSO
systemd(1), systemd.directives(7), systemd.exec(5), systemd.service(5), environ(7), capabilities(7)
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
