Is it possible to migrate some Xen DomU guests on an Debian Etch Dom0 running Xen 3.2.1?
The guests are various versions of Ubuntu 8.04+ or Debian.
The new machine is Ubuntu 10.04 running kvm.
At the moment it is only possible for Red Hat, as they are developing the virt-v2v tool, if an automated method is what you are looking for. See this video, where they demonstrate how easy it is.
Another option is to do everything by hand. This (2) blog post describes how to do it step-by-step for RHEL guests. I would guess it is fairly similar for Ubuntu guests.
If you don't care about network and IO performance, you can just make a domain.xml, the guest config file that contains network card info, partitions, and so on, as if the Xen guest was a KVM guest.
As long as you have enabled a kernel that supports KVM in the guest, KVM will run it in QEMU mode. Meaning without the optimized network and disk drivers.
To see how you create a domain.xml file see here (3) and here(4).