Note that according to the documentation,

In other words, the changes made by each virtual machine are persistent between VM restarts and this means that the 'differencing' image of a VM is going to grow as the VM makes updates on the 'multi-attach'ed disk. Each machine creates its own write history of the multi-attach image and the original disk image is never updated.Ī multi-attach type disk is like an immutable disk image, except that the 'differencing' image is not reset every time the machine starts.

As a result, any data that is written to such a virtual disk by one machine is not seen by the other machines to which the image is also attached. For each virtual machine to which such an image is attached, a 'differencing' image is created (under the Snapshots directory of the VM's VirtualBox definition directory). Multi-attach mode disk images can be attached to more than one virtual machines at the same time, even if these machines are running simultaneously. One option would be to clone your VirtualBox instance.īut, if you want to do this by using the same disk image for multiple virtual machines then you can change the Type of this disk image to Multi-attach.Īccording to VirtualBox documentation (section 5.4) the disk format (VMDK, VDI, etc.) is irrelevant to this. I understand that you have a single disk image that contains, say the root filesystem of a run-able Ubuntu instance and you want to create more than one virtual machine that will run this Ubuntu disk image.

Vmdk to vbox