---
name: "sysctl.conf"
section: "5"
platform: "linux"
package: "procps-ng"
version: "4.0.7-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "openbsd", "macos"]
url: "https://new.carta.tech/sysctl.conf"
---

# sysctl.conf(5)

Linux kernel configuration parameters

## NAME

sysctl.conf - Linux kernel configuration parameters

## DESCRIPTION

**sysctl.conf** is a set of configuration files that contain Linux kernel configuration parameters to be read and set by [**sysctl**(8)](/sysctl/8.md).

This man page describes the configuration files for *procps* **sysctl**. If you are using [**systemd-sysctl**(8)](/systemd-sysctl/8.md), refer to [**sysctl.d**(5)](/sysctl.d/5.md) 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.

## FILES

*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.

## BUGS

The maximum supported length of *value* is 4096 characters due to a limitation on */proc* entry length in the Linux kernel.

## EXAMPLES

```
#
#
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
```

## SEE ALSO

[**sysctl.d**(5)](/sysctl.d/5.md), [**sysctl**(8)](/sysctl/8.md), [**systemd-sysctl**(8)](/systemd-sysctl/8.md)