How to add Swap file on CentOS server

I need additional swap space to improve my Linux server performance,So here is a simple tutorial you can follow:

Before we proceed to swap file setup, we have to check if any swap files exist by looking at the summary of swap usage.

swapon -s

If the summary is empty, it means no swap file exists.

As we know that we do not have a swap file enabled, we can check how much space we have on the server with the following command.



The swap file will take 512MB and we are using only 26% so we can proceed.Now we can create the swap file using the dd command :

sudo dd if=/dev/zero of=/swapfile bs=1024 count=512k

It simply looks like this:


Next, create a swap file area using this command:

mkswap /swapfile


Setup correct file permissions:

chown root:root /swapfile
chmod 0600 /swapfile

Activate swap using this command:

swapon /swapfile

Check the summary again:

swapon -s


The last thing to do is to configure Swap to run and enabled each time your server reboots, edit the file nano /etc/fstab and add the following line at the end of file:

/swapfile none swap sw 0 0

Save changes and exit the editor.

You can verify swap is activated or not by simply using the below command: