====== Kerberos ======
<code bash>
env KRB5_TRACE=/dev/stdout
</code>

Blogs: 
  * https://www.centurion.link/w/programming/java/spnego
  * https://steveloughran.gitbooks.io/kerberos_and_hadoop/content/sections/keytabs.html
  * http://www.microhowto.info/howto/configure_apache_to_use_kerberos_authentication.html