sysctl.conf(5) — Linux manual page

SYSCTL.CONF(5)             File Formats Manual             SYSCTL.CONF(5)

NAME         top

       sysctl.conf - Linux kernel configuration parameters

DESCRIPTION         top

       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         top

       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         top

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

EXAMPLES         top

       #
       #
       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         top

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

COLOPHON         top

       This page is part of the procps-ng (/proc filesystem utilities)
       project.  Information about the project can be found at 
       ⟨https://gitlab.com/procps-ng/procps⟩.  If you have a bug report
       for this manual page, see
       ⟨https://gitlab.com/procps-ng/procps/blob/master/Documentation/bugs.md⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://gitlab.com/procps-ng/procps.git⟩ on 2025-08-11.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2025-07-30.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there is
       a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

procps-ng                       2025-05-29                 SYSCTL.CONF(5)

Pages that refer to this page: sysctl.d(5),  sysctl(8)

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