SYSCTL(8) - phpMan

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. This
requires the -w parameter to use.

-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 you want to change a sysctl setting.

-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 spec-
ified. 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.
/run/sysctl.d/*.conf
/etc/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 expres-
sion 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.conf