Prior to nsd 4.0.1-1ubuntu0.1, we had to create the nsd user before installing the nsd package.

This was our issue #25 (see 4e6037c0, c7e1e29d) and I reported it upstream at https://bugs.launchpad.net/ubuntu/+source/nsd/+bug/1311886. The new package was published by Ubuntu on 2015-01-15 so this work-around is no longer needed.