How to create or change the size of a swap file in Ubuntu

Check if the operating system already has a swap file

sudo swapon --show

The output shows the currently set up swap files. If there is no output, no swap file is in use.

To remove the swap file

# Disable the swap file usage
sudo swapoff </the swap file name>
# Delete the swap file
rm </the swap file name>

Allocate disk space for the new swap file in the root directory

cd /
sudo fallocate -l 8G /swapfile

Set up the permissions, so only the root user can access it

sudo chmod 600 /swapfile

Set up the swap file

sudo mkswap /swapfile

Enable the swap file

sudo swapon /swapfile

Make the swap file usage permanent, so it is used after every system boot. Add an entry into the /etc/fstab file. Open the file in the text editor

sudo nano /etc/fstab

Add the following line to the end of the /etc/fstab file, and save the file.

/swapfile none swap sw 0 0

Check the memory size including the swap file size

free -h

Check the disk size to make sure there is enough free disk space

df -h --total

Restart the computer and check the memory size again to make sure the swap file is in use again.

sudo reboot