title: 'Hash Sum mismatch'. How to edit /etc/apt/sources.list specifically?
body: <p>When I try to update my <em>apt-get</em>:</p>
  
  <p><code>$ sudo apt-get update</code></p>
  
  <p>The Warning will appear every time like beblow: </p>
  
  <pre><code>W: Failed to fetch http://cn.archive.ubuntu.com/ubuntu/dists/trusty-updates/main/binary-amd64/Packages Hash Sum mismatch
  </code></pre>
  
  <p>After searching the solution for this problem, I met one as below:</p>
  
  <blockquote>
    <p>For now, I edited /etc/apt/sources.list and updated it with a new
    mirror which solved the primary issue of not being able to find a
    candidate package.</p>
  </blockquote>
  
  <p>However, I don't know how to edit  <em>/etc/apt/sources.list</em>  specifically. Could you tell me how to edit in detail? Thanks in advance.</p>