SYSCTL
Section: System Administration (8)
Updated: 2020-02-27
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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
-
Use this option when all arguments prescribe a key to be set.
- -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 arguments to
sysctl
are files, which are read in the order they are specified.
The file argument may be specified as regular expression.
- -a, --all
-
Display all values currently available.
- --deprecated
-
Include deprecated parameters to
--all
values listing.
- -b, --binary
-
Print value without new line.
- --system
-
Load settings from all system configuration files. Files are read 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 directories 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
- -r, --pattern pattern
-
Only apply settings that match
pattern.
The
pattern
uses extended 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.
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 --system --pattern '^net.ipv6'
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
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
SEE ALSO
sysctl.conf(5)
regex(7)
AUTHOR
George Staikos
REPORTING BUGS
Please send bug reports to