Backing up VDI files

As I've been working with VirtualBox more and more, it only seemed natural to want to copy VDI files either for back up or transport to other systems. The usual VDI size, 4.2GB, is just about enough for a DVD-RW, so it should be no problem to burn it, right? Well, not exactly.

I've been bumping my head against this problem. All attempts to burn a VDI have failed, with the CD writing software reporting an error. I tried it with the default Gnome CD Burner, then with Brasero: nothing. Media error, maybe? Tried writing it to an ISO file, and it still failed.

Ultimate solution?

tar czvf VDIimage.tar.gz VDIimage.vdi

D'oh.