sysctl

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.

Documentation

• man 8 'sysctl' [EN]

Syntax

sysctl [PARAMETER ...] [VARIABLE[=VALUE]]

Parameters

-a

Display all values currently available.

-A

Display all values currently available in table form.

-n

Use this option to disable printing of the key name when printing values.

-p FILE

Load in sysctl settings from the FILE specified or /etc/sysctl.conf if none given. Specifying - as FILE means reading data from standard input.

-w

Use this option when you want to change a sysctl setting.

Examples

Set IP forwarding in the kernel

sysctl -w 'net.ipv4.ip_forward=1'

Test if a kernel parameter is set

if [[ $(${SYSCTL} -n 'net.ipv4.ip_forward') -eq 0 ]]; then
  echo "Kernel parameter 'net.ipv4.ip_forward' is set!"
fi