|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | PARAMETERS | FILES | NOTES | EXAMPLES | SEE ALSO | REPORTING BUGS | COLOPHON |
|
|
|
SYSCTL(8) System Manager's Manual SYSCTL(8)
sysctl - configure kernel parameters at runtime
sysctl [option ...] variable[=value] ...
sysctl -p file-or-regexp ...
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.
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 except deprecated
and verboten parameters.
--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.
/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
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
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).
The file /etc/sysctl.conf is read last which means it can
replace/override any parameters previously set in files in the
listed directories.
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
Verboten parameters
Certain kernel parameters should not be read due to side-effects
and will be skipped by sysctl using the --all option.
stat_refresh
This parameter returns no value but flushes per-cpu vm
statistics.
/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
proc(5), sysctl.conf(5), regex(7)
Please send bug reports to ⟨[email protected]⟩.
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
[email protected]
procps-ng 2024-07-19 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)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|