Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 11-05-2007, Руководство по установке

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27.1 Structure of a PAM
Configuration File
Each line in a PAM configuration file contains a maximum of four columns:
<Type of module> <Control flag> <Module path> <Options>
PAM modules are processed as stacks. Different types of modules have different pur-
poses, for example, one module checks the password, another one verifies the location
from which the system is accessed, and yet another one reads user-specific settings.
PAM knows about four different types of modules:
auth
The purpose of this type of module is to check the user's authenticity. This is tradi-
tionally done by querying a password, but it can also be achieved with the help of
a chip card or through biometrics (fingerprints or iris scan).
account
Modules of this type check whether the user has general permission to use the re-
quested service. As an example, such a check should be performed to ensure that
no one can log in under the username of an expired account.
password
The purpose of this type of module is to enable the change of an authentication
token. In most cases, this is a password.
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
496 Installation and Administration