For the record, Matthew Booth tracked this down: The problem was running mkinitrd in the RHEL 3 guest. This uses the RHEL 3 /bin/mount command to mount an ext2 filesystem. This old command was unable to modprobe missing modules, so if the ext2 module wasn't loaded it would simply give up. Now, if you mount any ext2 filesystem first, then the module gets loaded. The reason is that this uses the appliance /bin/mount which modprobes the required modules. RHEL 3 used ext3 filesystems, so ext2.ko was never loaded. The mkinitrd only uses ext2 for some temporary loopback mount, but that was sufficient to cause the failure. The solution will be to expose a guestfs_modprobe command so that callers can ensure the correct kernel modules are loaded so that an external command can complete. Rich. -- Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones Read my programming blog: http://rwmj.wordpress.com Fedora now supports 75 OCaml packages (the OPEN alternative to F#) http://cocan.org/getting_started_with_ocaml_on_red_hat_and_fedora