SYSCTL(8) System Administration SYSCTL(8)
NAME
sysctl - configure kernel parameters at runtime
SYNOPSIS
sysctl [options] [variable[=value]] [...]
sysctl -p [file or regexp] [...]
DESCRIPTION
sysctl is used to modify kernel parameters at runtime. The parameters
available are those listed under /proc/sys/. Procfs is required for
sysctl support in Linux. You can use sysctl to both read and write
sysctl data.
PARAMETERS
variable
The name of a key to read from. An example is kernel.ostype.
The '/' separator is also accepted in place of a '.'.
variable=value
To set a key, use the form variable=value where variable is the
key and value is the value to set it to. If the value contains
quotes or characters which are parsed by the shell, you may need
to enclose the value in double quotes.
-n, --values
Use this option to disable printing of the key name when printing
values.
-e, --ignore
Use this option to ignore errors about unknown keys.
-N, --names
Use this option to only print the names. It may be useful with
shells that have programmable completion.
-q, --quiet
Use this option to not display the values set to stdout.
-w, --write
Force all arguments to be write arguments and print an error if
they cannot be parsed this way.
-p[FILE], --load[=FILE]
Load in sysctl settings from the file specified or
/etc/sysctl.conf if none given. Specifying - as filename means
reading data from standard input. Using this option will mean ar-
guments to sysctl are files, which are read in the order they are
specified. The file argument may be specified as regular expres-
sion.
-a, --all
Display all values currently available except deprecated and ver-
boten parameters.
--deprecated
Include deprecated parameters to --all values listing.
-b, --binary
Print value without new line.
--system
Load settings from all system configuration files. See the System
file precedence sub-section below.
-r, --pattern pattern
Only apply settings that match pattern. The pattern uses ex-
tended regular expression syntax.
-A Alias of -a
-d Alias of -h
-f Alias of -p
-X Alias of -a
-o Does nothing, exists for BSD compatibility.
-x Does nothing, exists for BSD compatibility.
-h, --help
Display help text and exit.
-V, --version
Display version information and exit.
FILES
/proc/sys
/etc/sysctl.d/*.conf
/run/sysctl.d/*.conf
/usr/local/lib/sysctl.d/*.conf
/usr/lib/sysctl.d/*.conf
/lib/sysctl.d/*.conf
/etc/sysctl.conf
NOTES
System file precedence
When using the --system option, sysctl will read files from directories
in the following list in given order from top to bottom. Once a file of
a given filename is loaded, any file of the same name in subsequent di-
rectories is ignored.
/etc/sysctl.d/*.conf
/run/sysctl.d/*.conf
/usr/local/lib/sysctl.d/*.conf
/usr/lib/sysctl.d/*.conf
/lib/sysctl.d/*.conf
/etc/sysctl.conf
All configuration files are sorted in lexicographic order, regardless of
the directory they reside in. Configuration files can either be com-
pletely replaced (by having a new configuration file with the same name
in a directory of higher priority) or partially replaced (by having a
configuration file that is ordered later).
Deprecated parameters
The base_reachable_time and retrans_time are deprecated. The sysctl
command does not allow changing values of these parameters. Users who
insist to use deprecated kernel interfaces should push values to /proc
file system by other means. For example:
echo 256 > /proc/sys/net/ipv6/neigh/eth0/base_reachable_time
Verboten parameters
Certain kernel parameters should not be read due to side-effects and
will be skipped by sysctl using the --all option.
stat_refresh
This parameter returns no value but flushes per-cpu vm statis-
tics.
EXAMPLES
/sbin/sysctl -a
/sbin/sysctl -n kernel.hostname
/sbin/sysctl -w kernel.domainname="example.com"
/sbin/sysctl -p/etc/sysctl.conf
/sbin/sysctl -a --pattern forward
/sbin/sysctl -a --pattern forward$
/sbin/sysctl -a --pattern 'net.ipv4.conf.(eth|wlan)0.arp'
/sbin/sysctl --pattern '^net.ipv6' --system
SEE ALSO
proc(5), sysctl.conf(5), regex(7)
REPORTING BUGS
Please send bug reports to ]8;;procps@freelists.org\procps@freelists.org]8;;\
procps-ng 2024-07-19 SYSCTL(8)
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