anchor.diff:  system administration, particularly for how PAM authentication mechanism is
   configured on a Linux platform.
   
  -=== Prerequisites ===
  +== Prerequisites ==
   
   Successful configuration of the Yubico PAM module to support two factor
   authentication requires following prerequisites:
  
positive.code: `/etc/pam.d/system-auth` for RedHat based Linux system and into
  `/etc/pam.d/common-auth` for Debian based Linux systems.
  
  ==== SSH configuration ====
  
  Edit the sshd configuration file `/etc/ssh/sshd_config`_ to disable challenge-
  response passwords. Change `challenge-response passwords yes` to
  `challenge-response passwords no`.
  
  
  === Test Setup ===
  
  ==== Fedora 8 ====
  
  Test setup for fedora 8 environment is as follows:
  
  
negative.code: Yubico PAM Version:: pam_yubico-1.7
  
  
  === PAM configuration ===
  
  PAM configuration files in our testing environment are as follows:
  
  
  ==== /etc/pam.d/sshd ====
  -------
  auth           required  	 pam_yubico.so authfile=/etc/yubikeyid id=16 debug
  auth           include   	 system-auth
  