Authentication under modern Unix systems is handled by the Pluggable Authentication Module (PAM) system. In about a page and in your own words explain the PAM system as it is implemented on a Linux distri- bution and why it was introduced. Using the login service file found in the course virtual machine (see /etc/pam.d/login ) as an example, explain how a service is con- figured and discuss the implications of each configuration line. Your explanation should include discussions on the following: what is the module-type parameter, what is the control flag, what does it mean that the service file is a stack, what is a pam module. Notes: a. Be aware that there are subtle differences between different Unix distributionsthe question explicitly states discuss the Linux ver- sion only! b. The topics above are linked to each other and the question, they are not independent of each other. They are provided as a minimal guide only. Do not simply write an unconnected paragraph on each without linking the concepts together. c. List all resources used in answering this question. d. Please do not fall into the trap of answering the question by us- ing unexplained technical termsyou must explain all technical terms used especially if they have not been used anywhere else in the course. Assume you a writing for someone who knows nothing about PAM.