md_create: mdadm: boot: mdadm: boot is not a block device. at /home/rjones/d/libguestfs/images/guest-aux/make-fedora-img.pl line 95. Looking into this, it appears the old version of mdadm shipped in Ubuntu (mdadm 2.6.7) doesn't support the notion of giving arbitrary names to devices. Thus you have to do: mdadm --create /dev/md0 [devices] We do: mdadm --create boot [devices] which it doesn't know how to handle. I wonder if we are assuming so many features of mdadm >= 3 that we should simply test for this in the optional group "mdadm" test, and disable if mdadm < 3. (We would also have to change the test so it is skipped if mdadm is not present, but that's a real bug in the test suite anyway). Alternately we could look into this more deeply for RHEL 5 / Ubuntu 10.04. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://et.redhat.com/~rjones/virt-top