title: su - username command doesn't act as expected
body: <p>I am trying to switch to another user using <code>su</code> command, but it doesn't work as expected.</p>
  <p><strong>What I am expecting:</strong></p>
  <pre><code>[root@ubuntu ~]# su testuser
  [testuser@ubuntu root]#
  </code></pre>
  <p><strong>What actually happens:</strong></p>
  <pre><code>[root@ubuntu ~]# su testuser
  bash-4.2$
  </code></pre>
  <p><code>whoami</code> command:</p>
  <pre><code>bash-4.2$ whoami
  testuser
  </code></pre>