I thought this would be worth sharing.
I’ve got an old box under my desk that can run xen, but doesn’t have the virtualization extensions. This makes it somewhat difficult to do things like install certain linux distributions coughcentoscough that don’t provide a simple network installation mechanism, or their net install stuff requires being fully virtualized.
I found instructions on building your own chroot within a centos box to run chrooted services, which isn’t what I wanted, but I can extrapolate from a chroot into a xen vm. Just need to make a simple grub menu.lst and make sure that it has a real init system to actually boot from.
Following those instructions, I was able to construct a chroot on my fedora desktop. Unfortunately, after chrooting into the box itself, I wasn’t actually able to yum install anything, since the database formats were from the yum on my fedora 17 desktop, which is significantly newer than old CentOS 6.
Solution was to simply build a chroot within the chroot. Creating database files that are the appropriate format
for centos 6. Then I pulled that chroot out and did away with the intermediary chroot. A bit of
yum groupinstall Base and I had a working system that I could boot in a paravirtualized way. Fantastic.