title: vagrant error:Vagrantfile already exists in this directory
body: <p>When I input <code>$ vagrant box list</code>,<br>
  Terminal outputs: <code>centos64 (virtualbox)</code></p>
  
  <p>Now I input <code>$ vagrant init centos64</code>,<br>
  Terminal outputs an error message:</p>
  
  <pre><code>"Vagrantfile" already exists in this directory. Remove it before running "vagrant init".
  </code></pre>
  
  <p>How do I remove it?<br></p>