Novell LINUX ENTERPRISE DESKTOP 11 - SECURITY GUIDE 17-03-2009 Manual page 31

session
Modules of this type are responsible for managing and configuring user sessions.
They are started before and after authentication to register login attempts in system
logs and configure the user's specific environment (mail accounts, home directory,
system limits, etc.).
The second column contains control flags to influence the behavior of the modules
started:
required
A module with this flag must be successfully processed before the authentication
may proceed. After the failure of a module with the required flag, all other
modules with the same flag are processed before the user receives a message about
the failure of the authentication attempt.
requisite
Modules having this flag must also be processed successfully, in much the same
way as a module with the required flag. However, in case of failure a module
with this flag gives immediate feedback to the user and no further modules are
processed. In case of success, other modules are subsequently processed, just like
any modules with the required flag. The requisite flag can be used as a
basic filter checking for the existence of certain conditions that are essential for a
correct authentication.
sufficient
After a module with this flag has been successfully processed, the calling application
receives an immediate message about the success and no further modules are pro-
cessed, provided there was no preceding failure of a module with the required
flag. The failure of a module with the sufficient flag has no direct conse-
quences, in the sense that any subsequent modules are processed in their respective
order.
optional
The failure or success of a module with this flag does not have any direct conse-
quences. This can be useful for modules that are only intended to display a message
(for example, to tell the user that mail has arrived) without taking any further action.
include
If this flag is given, the file specified as argument is inserted at this place.
Authentication with PAM 19