Sometimes you end up having some trouble with ubuntu’s dns even if you actually edit properly /etc/resolv.conf.
That’s because resolvconf actually writes the file on /run/resolvconf/resolv.conf.
As a solution here’s what you can do:
$ sudo dpkg-reconfigure resolvconf
$ mv /etc/resolv.conf /run/resolvconf/resolv.conf
$ ln -s /run/resolvconf/resolv.conf /etc/resolv.conf