1PAM(8)                         Linux-PAM Manual                         PAM(8)
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NAME

6       PAM, pam - Pluggable Authentication Modules for Linux
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DESCRIPTION

9       This manual is intended to offer a quick introduction to Linux-PAM. For
10       more information the reader is directed to the Linux-PAM system
11       administrators' guide.
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13       Linux-PAM is a system of libraries that handle the authentication tasks
14       of applications (services) on the system. The library provides a stable
15       general interface (Application Programming Interface - API) that
16       privilege granting programs (such as login(1) and su(1)) defer to to
17       perform standard authentication tasks.
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19       The principal feature of the PAM approach is that the nature of the
20       authentication is dynamically configurable. In other words, the system
21       administrator is free to choose how individual service-providing
22       applications will authenticate users. This dynamic configuration is set
23       by the contents of the single Linux-PAM configuration file
24       /etc/pam.conf. Alternatively, the configuration can be set by
25       individual configuration files located in the /etc/pam.d/ directory.
26       The presence of this directory will cause Linux-PAM to ignore
27       /etc/pam.conf.
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29       From the point of view of the system administrator, for whom this
30       manual is provided, it is not of primary importance to understand the
31       internal behavior of the Linux-PAM library. The important point to
32       recognize is that the configuration file(s) define the connection
33       between applications (services) and the pluggable authentication
34       modules (PAMs) that perform the actual authentication tasks.
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36       Linux-PAM separates the tasks of authentication into four independent
37       management groups: account management; authentication management;
38       password management; and session management. (We highlight the
39       abbreviations used for these groups in the configuration file.)
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41       Simply put, these groups take care of different aspects of a typical
42       user's request for a restricted service:
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44       account - provide account verification types of service: has the user's
45       password expired?; is this user permitted access to the requested
46       service?
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48       authentication - authenticate a user and set up user credentials.
49       Typically this is via some challenge-response request that the user
50       must satisfy: if you are who you claim to be please enter your
51       password. Not all authentications are of this type, there exist
52       hardware based authentication schemes (such as the use of smart-cards
53       and biometric devices), with suitable modules, these may be substituted
54       seamlessly for more standard approaches to authentication - such is the
55       flexibility of Linux-PAM.
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57       password - this group's responsibility is the task of updating
58       authentication mechanisms. Typically, such services are strongly
59       coupled to those of the auth group. Some authentication mechanisms lend
60       themselves well to being updated with such a function. Standard UN*X
61       password-based access is the obvious example: please enter a
62       replacement password.
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64       session - this group of tasks cover things that should be done prior to
65       a service being given and after it is withdrawn. Such tasks include the
66       maintenance of audit trails and the mounting of the user's home
67       directory. The session management group is important as it provides
68       both an opening and closing hook for modules to affect the services
69       available to a user.
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FILES

72       /etc/pam.conf
73          the configuration file
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75       /etc/pam.d
76          the Linux-PAM configuration directory. Generally, if this directory
77          is present, the /etc/pam.conf file is ignored.
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ERRORS

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

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

88       pam(3), pam_authenticate(3), pam_sm_setcred(3), pam_strerror(3), PAM(8)
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92Linux-PAM Manual                  06/27/2006                            PAM(8)
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