Pluggable authentication modules are the core of user authentication in any
modern Linux distribution.

Modules pam_passwdqc and pam_ecryptfs were removed between Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7, thus making some PAM configuration files no longer valid.

The Preupgrade Assistant comments out these modules in your PAM configuration
files after the in-place upgrade automatically, but you should review and
regain the authentication functionality in another way, if these modules were
required for your authentication policy.
