Here’s a quick way to expand a (VDI) Virtual Disk Image in VirtualBox 3.

  1. Create a new VDI with the new size of your choice. (File / Virtual Media Manager / New…)
  2. Run this command:

    $ VBoxManage clonehd --existing old.vdi new.vdi

    This may take a few minutes.

  3. Simply replace the attached old.vdi with the new.vdi in your virtual machine’s storage settings.

  4. You will need to extend your partition from your guest OS. This can be done under Windows 7 from the control panel (Create and format hard disk partitions) and with GParted in Ubuntu and compatible Linux distributions.