virtualbox.org

in sunvirtual box, when creating a VM, specifying the dynamically expanding storage virtual disk, e.g. 10G, the VM will have 10G maximum. how can we resize the virtual disk if found it not big enough later, without recreating another VM with larger virtual disk, say 50G? are there any safe ways to do this?

It's in the VirtualBox FAQ. If you have Windows as Host, or Wine on your Linux machine, then you can use Mpack's CloneVDI tool (see the corresponding Hosts forum for a link).