PAM(8)								 Linux-PAM Manual							    PAM(8)

NAME

       PAM, pam - Pluggable Authentication Modules for Linux

DESCRIPTION

       This manual is intended to offer a quick introduction to Linux-PAM. For more information the reader is directed to the Linux-PAM system
       administrators' guide.

       Linux-PAM is a system of libraries that handle the authentication tasks of applications (services) on the system. The library provides a
       stable general interface (Application Programming Interface - API) that privilege granting programs (such as login(1) and su(1)) defer to
       to perform standard authentication tasks.

       The principal feature of the PAM approach is that the nature of the authentication is dynamically configurable. In other words, the system
       administrator is free to choose how individual service-providing applications will authenticate users. This dynamic configuration is set by
       the contents of the single Linux-PAM configuration file /etc/pam.conf. Alternatively, the configuration can be set by individual
       configuration files located in the /etc/pam.d/ directory. The presence of this directory will cause Linux-PAM to ignore /etc/pam.conf.

       From the point of view of the system administrator, for whom this manual is provided, it is not of primary importance to understand the
       internal behavior of the Linux-PAM library. The important point to recognize is that the configuration file(s) define the connection
       between applications (services) and the pluggable authentication modules (PAMs) that perform the actual authentication tasks.

       Linux-PAM separates the tasks of authentication into four independent management groups: account management; authentication management;
       password management; and session management. (We highlight the abbreviations used for these groups in the configuration file.)

       Simply put, these groups take care of different aspects of a typical user's request for a restricted service:

       account - provide account verification types of service: has the user's password expired?; is this user permitted access to the requested
       service?

       authentication - authenticate a user and set up user credentials. Typically this is via some challenge-response request that the user must
       satisfy: if you are who you claim to be please enter your password. Not all authentications are of this type, there exist hardware based
       authentication schemes (such as the use of smart-cards and biometric devices), with suitable modules, these may be substituted seamlessly
       for more standard approaches to authentication - such is the flexibility of Linux-PAM.

       password - this group's responsibility is the task of updating authentication mechanisms. Typically, such services are strongly coupled to
       those of the auth group. Some authentication mechanisms lend themselves well to being updated with such a function. Standard UN*X
       password-based access is the obvious example: please enter a replacement password.

       session - this group of tasks cover things that should be done prior to a service being given and after it is withdrawn. Such tasks include
       the maintenance of audit trails and the mounting of the user's home directory. The session management group is important as it provides
       both an opening and closing hook for modules to affect the services available to a user.

FILES

       /etc/pam.conf
	   the configuration file

       /etc/pam.d
	   the Linux-PAM configuration directory. Generally, if this directory is present, the /etc/pam.conf file is ignored.

ERRORS

       Typically errors generated by the Linux-PAM system of libraries, will be written to syslog(3).

CONFORMING TO

       DCE-RFC 86.0, October 1995. Contains additional features, but remains backwardly compatible with this RFC.

SEE ALSO

       pam(3), pam_authenticate(3), pam_sm_setcred(3), pam_strerror(3), PAM(8)

Linux-PAM Manual						    04/01/2010								    PAM(8)