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: server, a success code is returned.
  
  
  ==== pam_unix.so configuration ====
  
  Append _try_first_pass_ parameter to the _pam_unix.so_ module to authenticate
  the user with password passed from the preceding auth module. 
  
negative.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:
  
  