sysctl(8) — Linux manual page

SYSCTL(8)                 System Administration                SYSCTL(8)

NAME

       sysctl - configure kernel parameters at runtime

SYNOPSIS

       sysctl [option ...] 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.

       -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
              Force all arguments to be write arguments and print an
              error if they cannot be parsed this way.

       -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 specified.  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. See the
              SYSTEM FILE PRECEDENCE section below.

       -r, --pattern pattern
              Only apply settings that match pattern.  The pattern uses
              extended regular expression 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.

SYSTEM FILE PRECEDENCE

       When using the --system option, sysctl will read files 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.

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

       All configuration files are sorted in lexicographic order,
       regardless of the directory they reside in. Configuration files
       can either be completely replaced (by having a new configuration
       file with the same name in a directory of higher priority) or
       partially replaced (by having a configuration file that is
       ordered later).

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 --pattern '^net.ipv6' --system

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

SEE ALSO

       proc(5), sysctl.conf(5), regex(7)

AUTHOR

       George Staikos ⟨staikos@0wned.org⟩

REPORTING BUGS

       Please send bug reports to ⟨procps@freelists.org⟩.

COLOPHON

       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 2024-06-14.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2024-06-04.)  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                      2023-08-19                      SYSCTL(8)

Pages that refer to this page: perfalloc(1), pmdaperfevent(1), coredump.conf(5), lxc.container.conf(5), proc(5), sysctl.conf(5), sysctl.d(5), flowtop(8), systemd-coredump(8), systemd-sysctl.service(8)

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