sysctl - configure kernel parameters at runtime
sysctl [
options] [
variable[
=value]] [...]
sysctl -p [
file or
regexp] [...]
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.
- 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. See the
SYSTEM FILE PRECEDENCE section below.
-
-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.
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
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
All configuration files are sorted in lexicographic order, regardless of the
directory they reside in. Configuration files can either be completely
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).
/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
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
/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
sysctl.conf(5) regex(7)
George Staikos
Please send bug reports to
[email protected]