bc828721ed
I ended up with a corrupted image with the debugfs contraption once, and given I couldn't reproduce the problem I suppose that happens if the filesystem of the builder runs out of space. At least in this instance fsck could detect it, so let's add it as a sanity check.
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at http://nixos.org/nixos and in the manual in doc/manual.