Swapping is costly for disk I/O and not every Linux server needs to have a swap partition and to start swapping. For instance, MySQL servers have more than enough RAM available to do their work. Yet, when a swap partition is enabled Linux starts swapping, and that degrades 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
# swapoff -a to disable swapping
# sed to comment the swap partition in /etc/fstab
sed -i.bak -r 's/(.+ swap .+)/#\1/' /etc/fstab
Save this as
turn_swap_off.sh and execute as root:
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=10
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
Hi, my name is Jan. I am not a hacker, coder, developer or guru. I am merely an application manager / systems administrator, doing my daily thing at Embrace – The Human Cloud. In the past I worked at CLDIN (CLouDINfra) and Vevida. With over 20 years of experience, my specialties include Windows Server, IIS, Linux (CentOS, Debian), security, PHP, websites & optimization. I blog at https://www.saotn.org.