In a staging or production environment this involves modifying the DNS and adding a wildcard entry that points all hosts to the primary domain specified. To develop and test the subdomain aspect of a web application like this, most of the time developers just edit their hosts file locally and add an entry that piggybacks on the localhost entry. This post shows you how to do it dynamically using the DNS server BIND locally on OS X so you never have to mess with your pesky hosts file again!