Since under Xen debian etch the is no rpm-strap for fedora > 4 I proceed in this way.
Note: This is only a brief explanation, not an Howto nor a step-by-step guide.
I've installed fedora 8 somewhere with less stuff as possible, manually editing packages and remove any package you can during installation. This reduce fed8 into (only!) 800M filesystem. For simplicity I've used qemu with -no-acpi option as a target system.
From 'init 1' rsync the whole filesystem excluding /proc and /sys into the xen filesystem created for fedora, either File, Lvm partition or something like that.
rsync -av --delete --whole-file --numeric-ids --exclude /proc --exclude /sys / root@xenserverip:/mnt/fed8.img
Copy the /lib/modules from xen Dom0 to the fed8 DomU. Since we'll use Xen Dom0's kernel (2.6.18-5) intead of 2.6.23 we need those modules.
Start the fed8 DomU, reconfigure the network from concole, remove with yum the kernel which is not needed in DomU and, eventually, any other software which deal with hardware like acpid, ntp etc.
