How to configure sudo for two-factor authentication using pam-radius on Ubuntu and CentOS

Attackers frequently use lost, stolen, weak or default credentials to escalate their privileges after they have infiltrated your network. While two-factor authentication can greatly reduce infiltration, there are other means of gaining entry such as malware. This tutorial shows how to add radius to sudo for Centos 7 and Ubuntu 14.04 for two-factor authentication with the WiKID Strong Authentication server.