Add swap space to Linux

Swap space is that region on the hard disk that is used by the operating system to store information when the RAM has been fully utilized or exhausted. If you are running a system with less than 8GB, it is highly recommended that you create some swap space. Once the RAM is fully used, Linux starts to kill some processes which would interrupt the functioning of some of your processes. In this guide, we focus on how you can add swap space to your  Linux system.

Let’s dive in and see how you can create swap on your system

Step 1:  Checking if you have swap already enabled

Before anything else its prudent that you first verify if you have swap space added on your system. To achieve this , run

$ free -h


add swap space

As you can see from the output above, swap is not configured. Now we shall probe the system to see if we have sufficient space on the hard disk to create swap space

$ df -Th


df command check disk pace

From the output above, we can see that we have some free space of about 6.8G. We now have the green light to proceed


2.  Create Swap File

We are going to create a swap file using the fallocate command as shown below

$ sudo fallocate -l 1G /swapfile

You can verify the creation of swap  by running

$ swapon -show


swapon command

Great! As you can see from the output, we have successfully created a swap file of 1024M  with the label /swapfile

In the next step, we are going to convert the newly created swap file into swap space


Step 3. Convert Swap file into Swap space

Let’s begin by adjusting file permissions of the swap file to restrict access to other regular / non-root users

$ sudo chmod 600 /swap-partition


You can verify the set permissions using the ls command as shown

$ ls -lh /swapfile


ls -lh command
As we can see above, only the root user has read and write access. To convert the swap file into swap space, execute the command

To convert the swap file into swap space run


$ sudo mkswap /swapfile

swapon command

Again, to verify that you have created the swap run

$ free -h


free -h

This time around, you can see that swap has been allocated a space of  1.0G which hasn’t yet been used.


Step 4. Make Swap persistent after reboot

The swap we have just created does not survive a reboot, therefore we need to make it permanent. To do this, you need to append the following line to /etc/fstab
/swapfile swap swap deafults 0 0

Run the command below

$ echo "/swapfile      swap      swap    deafults    0   0" >> /etc/fstab

To verify, run

vim /etc/fstab


etc fstab

Awesome! At this point, we have successfully created swap and enabled it permanently on our system!

Give it a try and see how it goes. Your feedback is most welcome.

About James

Hey there! This is James, a Linux administrator and a tech enthusiast. I love experimenting with various distributions of Linux and keeping tabs on what's new in the Linux world.
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