# man > sysctl(8)

[_SYSCTL_(8)](https://www.chedong.com/phpMan.php/man/SYSCTL/8/markdown)                               System Administration                              [_SYSCTL_(8)](https://www.chedong.com/phpMan.php/man/SYSCTL/8/markdown)

## NAME
       sysctl - configure kernel parameters at runtime

## SYNOPSIS
       **sysctl **[_options_] [_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 pro‐
              grammable 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 --load
              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 speci‐
              fied.  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 **sec‐
              tion below.

### -r --pattern _
              Only apply settings that match _pattern_.  The _pattern_ uses extended regular  expression
              syntax.

### -A      -a

### -d      -h

### -f      -p

### -X      -a

### -o     

### -x     

### -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  configura‐
       tion  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)](https://www.chedong.com/phpMan.php/man/proc/5/markdown), [**sysctl.conf**(5)](https://www.chedong.com/phpMan.php/man/sysctl.conf/5/markdown), [**regex**(7)](https://www.chedong.com/phpMan.php/man/regex/7/markdown)

## AUTHOR
       ]8;;<staikos@0wned.org>\George Staikos]8;;\

## REPORTING BUGS
       Please send bug reports to ]8;;<procps@freelists.org>\<procps@freelists.org>]8;;\

procps-ng                                    2023-08-19                                    [_SYSCTL_(8)](https://www.chedong.com/phpMan.php/man/SYSCTL/8/markdown)