SYSCTL(8)                   System Administration                  SYSCTL(8)

NAME         top

sysctl – configure kernel parameters at runtime

SYNOPSIS         top

sysctl [options] [variable[=value]] […]
sysctl -p [file or regexp] […]

DESCRIPTION         top

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         top

The name of a key to read from.  An example is kernel.ostype.
The ‘/’ separator is also accepted in place of a ‘.’.

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.  This
requires the -w parameter to use.

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

-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.

Include deprecated parameters to –all values listing.

-b, –binary
Print value without new line.

Load settings from all system configuration files.

-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.

EXAMPLES         top

/sbin/sysctl -a
/sbin/sysctl -n kernel.hostname
/sbin/sysctl -w kernel.domainname=””
/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 –system –pattern ‘^net.ipv6’


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         top


SEE ALSO         top

sysctl.conf(5) regex(7)

AUTHOR         top

George Staikos ⟨⟩

REPORTING BUGS         top

Please send bug reports to ⟨⟩

COLOPHON         top

This page is part of the procps-ng (/proc filesystem utilities)
project.  Information about the project can be found at
⟨⟩.  If you have a bug
report for this manual page, see
⟨⟩.  This page was obtained
from the project’s upstream Git repository
( on 2014-12-30.  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

procps-ng                         Jan 2012                         SYSCTL(8)


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