Comment 4 for bug 1186228

To diagnose this what you have to do:

(1) Run libguestfs-test-tool

It will (presumably) fail. It will also print out an febootstrap-supermin-helper command line (or in newer versions, a supermin-helper command line). In the comment above, it printed out:

febootstrap-supermin-helper --verbose -f ext2 /usr/lib/guestfs/supermin.d i686 /var/tmp/guestfs.t3yS8p/kernel /var/tmp/guestfs.t3yS8p/initrd /var/tmp/guestfs.t3yS8p/root

(But note that your command line will be different).

(2) Modify the command line slightly. The 'kernel', 'initrd', and 'root' options are *output* files. You want those to be on /var/tmp. Also add -v -v -v. So you'd end up with something like:

febootstrap-supermin-helper --verbose -v -v -v -f ext2 /usr/lib/guestfs/supermin.d i686 /var/tmp/kernel /var/tmp/initrd /var/tmp/root

Run that command and it will print out lots of very detailed debugging information about what supermin-helper is trying to do.

Most likely (assuming you've not run out of disk space) it's because there's some symlink or parent directory missing, which you can fix by adding the right missing directory to /usr/lib/guestfs/supermin.d/00-missing-dir (see the supermin-helper man page).