title: How to set root_url
body: <p>In my Ruby on Rails 3.1 app I have a link like this: </p>
  
  <pre><code>&lt;%= link_to 'Home', root_url %&gt;
  </code></pre>
  
  <p>On My dev. machine it renders a link with "localhost:3000". On production it renders a link with an IP Address like this "83.112.12.27:8080". I would like to force rails to render the domain address instead of the IP Address. How can I set root_url?</p>