If you've been experimenting with different operating systems for a while, or you have some need to run more than one OS on a particular desktop machine, chances are you've been playing around with Oracle Virtualbox due to its ease of use, popular set of features, flexibility, and cost. You've also probably run into the following syndrome (usually while trying to build a new virtual machine):

• You configure a new virtual machine.
  
• You associate a bootable optical disk image with the new VM (for the sake of argument, let's say you're experimenting with the 50 megabyte(!) distro Damn Small Linux …

VirtualBox is a (mostly) open source virtualization stack designed to run on desktop machines. While you can run it in a "serious" fashion (such as using VMs to implement your network infrastructure) it really shines if you use it as part of your development effort.

If you want to get under the hood the VBoxManage utility is the first place to start. It lets you do things like convert and manipulate disk images, something that I do from time to time at work these days. Until I ran into the following problem when trying to convert a VMDK virtual disk …