title: NameError (uninitialized constant Mime::XLS):
body: <p>I am getting the problem on my Ubuntu server, but it works on my local machine completely without any error.</p>
  
  <pre><code>ruby version 1.9.3
  
  rails version 3.2.13
  </code></pre>
  
  <p>I have done the following configurations:</p>
  
  <p><strong>application.rb</strong></p>
  
  <pre><code>require File.expand_path('../boot', __FILE__)
  require 'csv'
  require 'rails/all'
  </code></pre>
  
  <p><strong>/initializers/mime_types.rb</strong></p>
  
  <pre><code>Mime::Type.register "application/xls", :xls
  #Mime::Type.register "application/vnd.ms-excel", :xls
  </code></pre>
  
  <p>I have got the reference from <a href="http://railscasts.com/episodes/362-exporting-csv-and-excel?view=asciicast">here</a></p>