SYSCTL.CONF(5)

NAME
sysctl.conf - Linux kernel configuration parameters

DESCRIPTION
sysctl.conf is a set of configuration files that contain Linux kernel configuration parameters to be read and set by sysctl(8).

This man page describes the configuration files for procps sysctl. If you are using systemd-sysctl(8), refer to sysctl.d(5) and note that it won't use the file /etc/sysctl.conf.

  Configuration Format
Each line of a file read by procps sysctl describes a kernel parameter in the following format.

        token = value

There is no need to use quotation marks for value, even if the value is a list of items.

Blank lines and lines that start with “#” or “;” are ignored.

If a line begins with a single “-”, a failing attempt to set the value is ignored.

FILES
procps sysctl, when run with the --system option, reads files from directories in the order shown below.

    /etc/sysctl.d/*.conf
    /run/sysctl.d/*.conf
    /usr/local/lib/sysctl.d/*.conf
    /usr/lib/sysctl.d/*.conf
    /lib/sysctl.d/*.conf

Finally, procps sysctl reads /etc/sysctl.conf. This file is not used by systemd-sysctl, which means that some kernel parameters are not set depending on the implementation of sysctl that is installed.

BUGS
The maximum supported length of value is 4096 characters due to a limitation on /proc entry length in the Linux kernel.

EXAMPLES
    #
    #
    kernel.domainname = example.com
    ; A value containing a space is written to the sysctl.
    kernel.modprobe = /sbin/mod probe
    # A list of items for the value
    net.ipv4.ip_local_reserved_ports=8080,9148

SEE ALSO
sysctl.d(5), sysctl(8), systemd-sysctl(8)