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NAME | DESCRIPTION | FILES | BUGS | EXAMPLES | SEE ALSO | COLOPHON |
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SYSCTL.CONF(5) File Formats Manual SYSCTL.CONF(5)
sysctl.conf - Linux kernel configuration parameters
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.
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.
The maximum supported length of value is 4096 characters due to a
limitation on /proc entry length in the Linux kernel.
#
#
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
sysctl.d(5), sysctl(8), systemd-sysctl(8)
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 2025-05-29 SYSCTL.CONF(5)
Pages that refer to this page: sysctl.d(5), sysctl(8)
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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. |
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