@samuel on DFRI machines we mostly use virt-install. You can either (easiest to start with) make it start a debian installer that you manually go through, or (better) do something more automated by first running virt-builder and virt-sysprep and then supplying the resulting file as input to virt-install so that you donät need to manually go through the debian installer. It's really good if you can make it all automated, have a VM creation script that you can run without anything interactive.