Comment 1 for bug 8585

This is a cosmetic issue; everything is working fine, and there is no cause for
concern. (adjusting severity appropriately) This is reproducible on all of my
Ubuntu systems.
My guess is that this has something to do with the way that the root device is
mounted from the initrd. checkroot.sh creates the mtab entry with:

mount -f -o $rootopts $fstabroot /

which seems to result in type "unknown".