I'm using VirtualBox 2.1.0 so some of the following commands may not work with older versions. I learned the hard way that they have changed a number of tools for VirtualBox and some of the older tools where probably easier to use and documented better. I installed the package I was using from an ISO image and then started trying to extract the part that I needed from the VDI that was created.

My first attempt at extracting the partition required me to convert my dynamic VDI into a static image. To dump a dynamic VDI into a static image you run this command:

I thought I could find the image by hand in the VDI after I had it in a raw format. There were a number of hints that I found that made me think I could just pull the partition out without much of a problem: VirtualBox and forensics tools and a forum post. However I found that just looking around wasn't easy enough to find where the partition started so I moved on to trying to find something else that could scan the disk and find it.

I rand into TestDisk and gave it a try. When it would scan the disk it found the /boot partition but for some reason it wasn't finding the root partition so I moved on.

I then took a look at the format for VDI disks to see if it was possible to pull it out given the header information with a simple program but that looked like it would be a lot of work so it was back to square one.

Along the way I happened to came across information about an undocumented command to export raw disk image. This turned out to be the break I needed because running the following command will result in only the disk image itself without any VirtualBox residue:

At this point things became a lot easier. There were multiple partitions on the resulting disk image but I only needed the / partition. To extract the root partition I first listed the partitions with this command:

This output the following for my image:

To figure out where the root partition starts I just multiplied the start sector by the number of bytes per sector: 208845 * 512 = 106928640

I then did a quick test to make sure I had the correct partition:

This looked good so I extracted the partition from the disk and did a filesystem check on it:

Extracting the partition you want is about 80% of the battle. Getting it to run under Xen after extraction is just a matter of fixing anything that was left out because the install was done under a "real" machine.

I add a nosegneg ld.so.conf directive and move /lib/tls directory out of the way first:

Next the base device entries needed to be created:

I then removed the disk label from the partition using e2label:

Because I was sending this image to EC2 I recreated the fstab with the following entries that are specific to the way EC2 allocates disks to a node:

The finally, again because I was going to EC2 I added a few scripts and created rc.local to let me in when the instance was started.

This seems to be a fairly easy process now that I have done it from start to finish once.