title: Use of /etc/passwd-, /etc/shadow-, /etc/group-
body: <p>In addition to the files : <code>/etc/group</code>, <code>/etc/passwd</code> and <code>/etc/shadow</code>, I could see three files in my linux machine. </p>
  
  <ol>
  <li><code>/etc/group-</code></li>
  <li><code>/etc/passwd-</code></li>
  <li><code>/etc/shadow-</code></li>
  </ol>
  
  <p>I cannot see these files in my <code>root filesystem</code>. But when I try to add one user using <code>useradd</code> command, these files seem to get generated. </p>
  
  <p>So i would like to know when exactly is these files created and what is the use of these files?</p>