Erm.... that is a completely different problem. Do the following: sudo -EHs su, then as root sudo -EH -u {username} firefox --new-window I'll leave to you the

Erm.... that is a completely different problem. Do the following: sudo -EHs su, then as root sudo -EH -u {username} firefox --new-window I'll leave to you the exercise of learning what the flags do, and implicitly why it fails in your case.