Learn the Linux sysctl Command

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The Linux sysctl command configures kernel parameters at runtime. The parameters available are those listed under /proc/sys/. Procfs is required for sysctl(8) support in Linux. Use sysctl(8) to both read and write sysctl data.  

Synopsis

sysctl [-n] [-e] variable ... sysctl [-n] [-e] -w variable=value ... sysctl [-n] [-e] -p <filename> (default /etc/sysctl.conf) sysctl [-n] [-e] -a sysctl [-n] [-e] -A

Parameters

A variable is the name of a key to read from—for example:

kernel.ostype

The slash separator is also accepted in place of a period delimiting the key/value pair. For example:

kernel/ostype

To set a key, use the form:

variable=value

Variable is the key and value is the value it's set to. If the value contains quotes or characters that are parsed by the shell, you may need to enclose the value in double quotes. This requires the -w parameter to use.

Other parameters

-n: Use this option to print only values of the given variable or variables.

-e: Use this option to ignore errors about unknown keys.

-p: Load sysctl settings from the file specified or /etc/sysctl.conf if none is given.

-a: Displays all variables.

-w: Enables writing of a value to a variable.

Examples of usage

/sbin/sysctl -a
/sbin/sysctl -n kernel.hostname
/sbin/sysctl -w kernel.domainname="example.com"
/sbin/sysctl -p /etc/sysctl.conf

Specific usage may vary by Linux distribution. Use the man command (% man) to see how a command is used on your particular computer.