anchor.diff:  
   We assume that OpenVPN server is already installed on the server.
   
  -a) Configuration of OpenVPN server to support PAM authentication:
  ------------------------------------------------------------------
  +==== Configuration of OpenVPN server to support PAM authentication:
   
   * Edit the OpenVPN server configuration file `/etc/openvpn/server.conf`
     to add the following three lines to enable PAM modules for username
  
positive.code: Introduction
  ------------
  
  The purpose of this document is to guide readers through the configuration steps to use two factor authentication for OpenVPN using YubiKey. This document assumes that the reader has advanced knowledge and experience in Linux system administration, particularly for how PAM authentication mechanism is configured on a Linux platform.
  
  
  Prerequisites
  -------------
  
  Successful configuration of the Yubico PAM module to support two factor authentication for OpenVPN has the following prerequisites:
  
  
negative.code: session    	 include     	system-auth
  ------
  
  ==== Testing the configuration
  
  We have tested the pam_yubico configuration on following Linux sever platforms:
  
  