127.0.0.1       localhost
127.0.0.1       foobar

or (or the same entries swapped:

127.0.0.1       localhost
127.0.0.1       foobar.bar.net     foobar

or (or the same entries swapped:

127.0.0.1       localhost localdomain.localhost
127.0.0.1       foobar.bar.net     foobar