因為要把 VDI 檔匯出成 RAW Image 所以筆記一下步驟：

Compact:
VBoxManage modifyvdi /full/path/to/test.vdi compact
Convert:
VBoxManage internalcommands converttoraw file.vdi file.raw

@see: http://en.wikibooks.org/wiki/QEMU/Images#Exchanging_images_with_VirtualBox