I wanted to install a Fedora 13 machine as a paravirtual domu guest on our CentOS 5.5, xen 3.4.2 host. I also wanted to provision it using koan/cobbler. I ran into a few problems along the way, but I got there in the end!
Firstly, createrepo in CentOS 5.5 does not work with either the Fedora 13 distribution image, or the Fedora 13 Updates repo. I got round that by rebuilding createrepo from Fedora 13 on CentOS 5.5 which was in itself a major undertaking as it also involved rebuilding several other packages which are dependencies of createrepo (yum, yum-utils, python-urlgrabber, python-pycurl, curl, libssh2).
Once I'd got the F13 distro imported into cobbler, and mirrored the F13 Updates repo, I created the cobbler system entry and ran koan to kick off the PXE install. All seemed to work fine and the installation completed. However, when I tried to start the domu it wouldn't start. In /var/log/xen/xend.log I found this was the last line:
[2010-09-01 16:43:05 9717] DEBUG (XendBootloader:113) Launching bootloader as ['/usr/bin/pygrub', '--output=/var/run/xend/boot/xenbl.11641', '/dev/mapper/vg_guests-mock--disk0']
On a hunch, I modified the kickstart to explicitly format the /boot partition as ext3 rather than the default ext4 and re-tried the install process. Bingo! pygrub in xen 3.4.2 on CentOS 5.5 doesn't work with ext4.