I use KVM daily for testing purposes of Ubuntu One on Windows. Recetly I created a Vista VM with 20Gb thinking that it was going to be big enough, turns out that after installation I had a single Gb left (WTF!). Not wanting to have to go through the painful installation process again I decided to find out how to re-size a KVM disk image. Here are the steps if you have to do the same:

  1. Create a new image with the extra size

    sudo qemu-img create -f raw addon.raw 30G
  2. Add the new data, my old vm image is called caranage_old.img. Do remember the order is important, otherwise the image won’t boot.

    cat carnage_old.img addon.raw >> carnage.img
  3. Create a new vm that uses the new image and resize the hardrive accordingly. For example, on Windows Vista I had to go to Mamangement Tools and resize the C: partition to use the new 30Gb.
  4. I hope it helps!

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