How to Add Swap Space on Ubuntu 20.04

Linux / November 25, 2021 / ashishpsk / 0

• Systems with less than 2 GB RAM – 2 times the amount of RAM.
• Systems with 2 to 8 GB RAM – the same size as the amount of RAM.
• Systems with more than 8 GB RAM – at least 4 GB of Swap

First, create a file that will be used as swap:

sudo fallocate -l 2G /swapfile

If the fallocate the utility is not present on your system, or you get an error message saying fallocate failed: Operation not supported, use the following command to create the swap file:

sudo dd if=/dev/zero of=/swapfile bs=1024 count=2097152

Set the file permissions to 600 to prevent regular users to write and read the file:

sudo chmod 600 /swapfile

Create a Linux swap area on the file:

sudo mkswap /swapfile

Activate the swap file by running the following command:

sudo swapon /swapfile

To make the change permanent open the /etc/fstab file:

sudo nano /etc/fstab

and paste the following line:

/swapfile swap swap defaults 0 0

Verify that the swap is active

sudo swapon --show

Swappiness is a Linux kernel property that defines how often the system will use the swap space. It can have a value between 0 and 100. A low value will make the kernel to try to avoid swapping whenever possible, while a higher value will make the kernel to use the swap space more aggressively.

On Ubuntu, the default swappiness value is set to 60. You can check the current value by typing the following command:

cat /proc/sys/vm/swappiness

While the swappiness value of 60 is OK for most Linux systems, for production servers, you may need to set a lower value.

For example, to set the swappiness value to 10, run:

sudo sysctl vm.swappiness=10

To make this parameter persistent across reboots, append the following line to the /etc/sysctl.conf file:

vm.swappiness=10

The optimal swappiness value depends on your system workload and how the memory is being used. You should adjust this parameter in small increments to find an optimal value.