How to add swap space on Ubuntu 20.04

This article was first published in: https://www.itcoder.tech/posts/how-to-add-swap-space-on-ubuntu-20-04/

Swap space is a space on the hard disk that is urgently requisitioned when the physical RAM memory is used up. When the RAM memory of a Linux system is exhausted, inactive memory pages will be moved to swap space.

The swap space can be an independent swap partition or a swap file. Typically, when running an Ubuntu on a virtual machine, there is no swap partition, and the only option is to create a swap file.

This tutorial explains how to add a swap file on Ubuntu 20.04.

1. Before you start##

The swap partition should not be used as a substitute for physical memory. Because the swap partition is a part of the hard drive, it has a slower access time than physical memory. If your system runs out of memory frequently, you should add more memory.

Generally, the swap file size depends on how much RAM your system has:

Systems with less than 2 GB RAM memory-2 times the size of RAM memory
2 Up to 8 GB RAM memory system-same RAM memory size
Systems with more than 8 GB RAM memory-at least 4 GB swap file

Only root or other users with sudo privileges can activate the swap file.

Second, create a swap file##

In this example, we create a 2 GB swap file. If you want to add more swap files, replace 2G with the size of the swap space you need to set.

Complete the following steps to add swap space on Ubuntu 20.04:

First, create a file to be used as a swap file:

sudo fallocate -l 2G /swapfile

If the fallocate tool is not available on your system, or you get a message: 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 file permissions to 600 to prevent regular users from reading and writing this file:

sudo chmod 600/swapfile

Create a Linux swap area on this file:

sudo mkswap /swapfile

The output is as follows:

Setting up swapspace version 1, size =2GiB(2147479552 bytes)
no label, UUID=fde7d2c8-06ea-400a-9027-fd731d8ab4c8

Activate the swap area by running the following command:

sudo swapon /swapfile

To persist, open the /etc/fstab file:

sudo nano /etc/fstab

And paste the following line:

/swapfile swap swap defaults 00

Use the swapon or free command to verify whether the swap area is activated, like the following:

sudo swapon --show

NAME      TYPE      SIZE  USED PRIO
/swapfile file        2G    0B   -1

sudo free -h

    total        used        free      shared  buff/cache   available
Mem:          981Mi        97Mi        68Mi       0.0Ki       814Mi       735Mi
Swap:2.0Gi        10Mi       1.9Gi

Third, adjust the swappiness value##

Swappiness is a Linux kernel attribute used to define how frequently the system will use the swap partition. It ranges from 0 to 100. A lower value can avoid swap when possible, and a higher value will make the kernel use the swap partition more frequently.

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

cat /proc/sys/vm/swappiness

The output is as follows:

Swappiness of 60 is suitable for most Linux operating systems. For production servers, you need to set this value to a lower value.

For example, to change the Swappiness value to 10, run:

sudo sysctl vm.swappiness=10

To make this parameter persistent and still work when restarting, append the following to the /etc/sysctl.conf file:

vm.swappiness=10

The optimal swappiness depends on your system and how the memory is used. You need to adjust this value in small steps to find the most suitable value.

Fourth, remove a swap file##

To deactivate and delete the swap file, follow the steps below:

First, deactivate the swap space:

sudo swapoff -v /swapfile

Next, remove the swap file entry /swapfile swap swap defaults 0 0 from the /etc/fstab file.
Finally, use the rm command to delete the actual swap file:

sudo rm /swapfile

Five, summary##

We have shown you how to create a swap file, activate, and configure swap space on your Ubuntu 20.04 system.

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