Swap is a space on a disk that is used when the amount of physical RAM memory is full. When a Linux system runs out of RAM, inactive pages are moved from the RAM to the swap space. Swap space can take the form of either a dedicated swap partition or a swap file. In most cases when running Ubuntu on a virtual machine a swap partition is not present so the only option is to create a swap file. This tutorial covers the steps necessary to add a swap file on Ubuntu 18.04 systems.