PAM: Pluggable Authentication Modules

http://en.wikipedia.org/wiki/Linux_PAM
http://www.kernel.org/pub/linux/libs/pam/
http://mouse.oit.edu.tw/htdocs/PAM.htm
http://meandubuntu.wordpress.com/2008/09/06/xfce-slim-pam-and-jack/
http://www.chinaunix.net/jh/4/390136.html
http://www.ibm.com/developerworks/linux/library/l-pam/index.html
http://www.linuxuser.com.tw/skill_detail.php?cid=434
http://kezeodsnx.pixnet.net/blog/post/25830961

service type control module-path module-arguments

Module type:
account
auth
password
session

Control value:
required : Check each one, need all required item pass
requisite : If not pass on this one, just return fail, bypass the others
sufficient: If pass, just return success, bypass the others
optional :

PAM API
pam_start()
pam_authenticate()
pam_acct_mgmt()
pam_end()