system-auth man page
system-auth — Common configuration file for PAMified services
/etc/pam.d/system-auth /etc/pam.d/password-auth /etc/pam.d/fingerprint-auth /etc/pam.d/smartcard-auth
The purpose of these configuration files are to provide a common interface for all applications and service daemons calling into the PAM library.
The system-auth configuration file is included from nearly all individual service configuration files with the help of the substack directive.
The password-auth fingerprint-auth smartcard-auth configuration files are for applications which handle authentication from different types of devices via simultaneously running individual conversations instead of one aggregate conversation.
Previously these common configuration files were included with the help of the include directive. This limited the use of the different action types of modules. With the use of substack directive to include these common configuration files this limitation no longer applies.
pam(8), config-util(5), postlogin(5)
The three Linux-PAM Guides, for system administrators, module developers, and application developers.