Step 1: Determine if a swapfile already exists
Open a Terminal and enter the command
free -m
If the result shows the swap has 0 total MB, 0 used MB, and 0 free MB then there is no swapfile.
Step 2: Check the Amount of Available Free Space
In Terminal, enter
df -h
Step 3: Create a New Swapfile
In this example the swapfile will be placed on the root directory and will be 10 gigabytes in size.
In Terminal, enter
sudo fallocate -l 10G /swapfile
Step 4: Enable the Swapfile
In Terminal, enter
sudo mkswap /swapfile
Then,
sudo swapon /swapfile
Verify this was created by entering,
sudo swapon -s
Step 5: Make the Swapfile Persistent
In Terminal, enter
sudo gedit /etc/fstab
Any file editor will do, here we are using gedit.
When the file opens, add a new line at the bottom and enter
/swapfile none swap sw 0 0
Save and close the file.