The history of PAM goes back to 1995 when developers from Sun Microsystems implemented a generic framework for Solaris. When Solaris 2.6 was released in August 1997, PAM was an integrated component of the operating system. Ever since then, Solaris has been using PAM for authentication. In February 1997, the Linux-PAM project began, and most GNU/Linux distributions today are using PAM.

The official website of Linux PAM is http://www.kernel.org/pub/linux/libs/pam/, while SUN Microsystems documents the Solaris PAM at http://www.sun.com/software/solaris/pam/, and OpenPAM used by FreeBSD can be found at http://trac.des.no/openpam/. PAM implementations are based on an open standard from the Open Group named XSSO, which can be found at http://www.opengroup.org/pubs/catalog/p702.htm.

The primary operating system of this book is GNU/Linux, but PAM does exist for many operating systems. Configuration files are almost identical across Linux and UNIX operating systems—module names might differ slightly and some modules are not supported on every contemporary UNIX. This means that the examples in this book can be carried from one UNIX environment to another with minor adjustment.

The examples in the book have been tested under Ubuntu Linux 6.06 LTS or SuSE Linux Enterprise Server 9 SP2 (as VMware guests).