This chapter was contributed by Sun security administrators as a discussion on how to use Secure Remote Procedure Calls (RPCs) to authenticate a host and a user across a Network File System (NFS) mount. Additionally, this chapter covers the Pluggable Authentication Module (PAM) framework, which provides a method to "plug in" authentication services and provides support for multiple authentication services. For brevity, the material presented in this chapter was condensed to contain only topics you should know for the exam.