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PAM(8) NetBSD System Manager's Manual PAM(8)
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pam -- Pluggable Authentication Modules framework
The Pluggable Authentication Modules (PAM) framework is a system of
libraries that perform authentication tasks for services and applica-
tions. Applications that use the PAM API may have their authentication
behavior configured by the system administrator through the use of the
service's PAM configuration file.
PAM modules provide four classes of functionality:
account Account verification services such as password expiration and
auth Authentication services. This usually takes the form of a
challenge-response conversation. However, PAM can also sup-
port, with appropriate hardware support, biometric devices,
smart-cards, and so forth.
password Password (or, more generally, authentication token) change and
session Session management services. These are tasks that are per-
formed before access to a service is granted and after access
to a service is withdrawn. These may include updating activity
logs or setting up and tearing down credential forwarding
A primary feature of PAM is the notion of ``stacking'' different modules
together to form a processing chain for the task. This allows fairly
precise control over how a particular authentication task is performed,
and under what conditions. PAM module configurations may also inherit
stacks from other module configurations, providing some degree of cen-
login(1), passwd(1), su(1), pam(3), pam.conf(5), pam_chroot(8),
pam_deny(8), pam_echo(8), pam_exec(8), pam_ftpusers(8), pam_group(8),
pam_guest(8), pam_krb5(8), pam_ksu(8), pam_lastlog(8),
pam_login_access(8), pam_nologin(8), pam_permit(8), pam_radius(8),
pam_rhosts(8), pam_rootok(8), pam_securetty(8), pam_self(8), pam_skey(8),
The Pluggable Authentication Module framework was originally developed by
SunSoft, described in DCE/OSF-RFC 86.0, and first deployed in Solaris
2.6. It was later incorporated into the X/Open Single Sign-On Service
(XSSO) Pluggable Authentication Modules specification.
The Pluggable Authentication Module framework first appeared in
NetBSD 9.99 February 28, 2005 NetBSD 9.99