Linux Pluggable Authentication Modules (PAM) is a suite of libraries that allow a Linux system administrator to configure methods to authenticate users. It provides a flexible and centralized way to switch authentication methods for secured applications by using configuration files instead of changing application code. There are Linux PAM libraries allowing authentication using methods such as local passwords, LDAP, or fingerprint readers. Linux PAM is evolved from the Unix Pluggable Authentication Modules architecture. Linux-PAM separates the tasks of authentication into four independent management groups: