Turn off swap

Not every Linux server I maintain needs to have a swap partition and to start swapping. For instance, the MySQL servers all have more than enough RAM on board to do their work. Yet, when a swap partition is enabled Linux starts swapping, which may degrade MySQL database performance…

Bash script to turn off Linux swap partition

An unwanted Linux swap partition can be the result of an automated and unattended Linux installation. Of course you can fiddle with the Linux kernel swapiness settings, located in /proc/sys/vm/swapiness and configurable in /etc/sysctl.conf, but one can turn off the swap completely too.

Here’s a tiny bash script to disable Linux’ swap – for which we use the swapoff command – and to comment out the swap partition in /etc/fstab

#!/bin/bash
# swapoff -a to disable swapping
swapoff -a
# sed to comment the swap partition in /etc/fstab
sed -i.bak -r 's/(.+ swap .+)/#\1/' /etc/fstabCode language: Bash (bash)

Save this as turn_swap_off.sh and execute as root:

sh /root/turn_swap_off.shCode language: Bash (bash)

A backup of the /etc/fstab file is made just to be sure and to stay on the safe side.

Disable swappiness kernel parameter

Swappiness is a property for the Linux kernel that changes the balance between swapping out runtime memory, as opposed to dropping pages from the system page cache. Swappiness can be set to values between 0 and 100, inclusive. A low value means the kernel will try to avoid swapping as much as possible where a higher value instead will make the kernel aggressively try to use swap space.

You manage swappiness with sysctl, either to get its current value or to set a new swappiness value. For example:

# get current swappiness value
sudo sysctl vm.swappiness

# set a new swappiness value - for example 10
sudo sysctl vm.swappiness=10Code language: Bash (bash)

You can also edit the /etc/sysctl.conf configuration file. Open the file /etc/sysctl.conf with your text editor and change the value of the following entry vm.swappiness to your suitable value (add the entry if it does not exist).

~$ sudo vi /etc/sysctl.conf
~$ grep swappiness /etc/sysctl.conf
vm.swappiness=10Code language: Bash (bash)