I’m using VirtualBox since a couple of years to run Windows on top of my Linux boxes. After a while, the virtual disk size may increase to unreasonable sizes and I was searching for an option to “compact” it like in Parallels/VMWare.
Contrary to these other virtualization tools, there is nothing in VirtualBox’ GUI to do this. Fortunately, you can use 2 tools to achieve the same goal…
First, you need to download SDelete from Microsoft and run it in the VM:
sdelete -c
Now stop the VM and compact the disk:
VBoxManage modifyhd blah.vdi --compact
That’s it, your disk is now compacted and you have probably gained a couple of GB!