While using Virtualbox, one thing that I have found is that the size of the VM (a file with .VDI extension) expands over time. If you have selected the “Dynamically Expanding Storage” option when first creating the VM, you will find that the file size expands whenever you install new applications in the VM. That is perfectly normal. However, when you uninstall or delete applications in the VM, the file size does not shrink or return to its previous size. That is to say, if you are constantly installing and uninstalling applications in your VM, the VDI file could be taking up more space than it is actually using.

If you have a great deal of hard disk space to spare, you can simply ignore this. However, if you find yourself always running short of hard disk space, you might want to consider shrinking the VM and free up unused disk space.

This tutorial will go through the steps to shrink your Virtualbox VM.