title: "can not fork user shell: Cannot allocate memory"
body: <p>When i'm login into my server using putty it log in perfectly but when i try to use : <code>su</code> it asks for password. But after a while without login as super user it shows </p>
  
  <pre><code>can not fork user shell: Cannot allocate memory
  </code></pre>
  
  <p>How to overcome this situation ?</p>