# Sysctl

## Table of contents <!-- omit in toc -->

1. [TL;DR](#tldr)
1. [Further readings](#further-readings)

## TL;DR

Default configuration files locations:

1. `/run/sysctl.d/*.conf`
1. `/etc/sysctl.d/*.conf`
1. `/usr/local/lib/sysctl.d/*.conf`
1. `/usr/lib/sysctl.d/*.conf`
1. `/lib/sysctl.d/*.conf`
1. `/etc/sysctl.conf`

```sh
# Show the value of a single setting.
sysctl kernel.ostype
sysctl vm.swappiness

# Show the values of all settings.
sysctl -a

# Change the current value of a setting.
sudo sysctl vm.swappiness=10
sudo sysctl -w net.ipv4.ip_forward=1

# Reload settings from specific configuration files.
sudo sysctl -p
sudo sysctl -p /etc/sysctl.d/99-swappiness.conf

# Reload settings from the default configuration files locations.
sudo sysctl --system

# Set up persistent settings.
echo 'vm.swappiness=10'  | sudo tee -a /etc/sysctl.conf
echo 'vm.swappiness = 5' | sudo tee -a /etc/sysctl.d/99-swappiness.conf
```

## Further readings

- [How to reload sysctl.conf variables on Linux]
- [Documentation for /proc/sys]

<!--
  References
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<!-- Upstream -->
[documentation for /proc/sys]: https://docs.kernel.org/admin-guide/sysctl/

<!-- Others -->
[how to reload sysctl.conf variables on linux]: https://www.cyberciti.biz/faq/reload-sysctl-conf-on-linux-using-sysctl/