[VirtualBox] Resize virtual hard disk

Resizing a virtual HD on VirtualBox is a fairly simple process but may involve using a third party tool too.

Changing the virtual disk size can be achieved using the modifyhd command from command line:

VBoxManage modifyhd .vdi --resize NEW_SIZE

Note that this will just resize the HD, the guest OS will NOT automatically adapt to these changes, meaning that you'll have to manually shrink/expand the virtual HD partitions before starting the OS again.

You can do that with, for example, GParted, which comes with as a handy live cd (iso) too; just download the image and link it as virtual CD then start the machine and boot from CD drive.