If you have used Oracle VirtualBox, you might have noticed that once virtual machines are deleted, the associated storage space allocated doesn’t get deleted automatically.
What happens due to this is after a while when many virtual machines are created and deleted, the physical disk space on the host OS (the system on which Oracle VirtualBox is installed) continues to shrink as the virtual hard drives from previous virtual machines are still present.
Here is how to remove the virtual drives once you delete the virtual machines from the host (Linux Mint is used here as the host OS) :
1. Go to System Tools > Oracle VM Virtual Box.
2. Select File > Virtual Media Manager
3. If virtual hard drives are present, they will show up in the list. Select drives that need to be deleted and hit Remove.