group handling

[Duke]

Hi,

I want to set up a database login system using pam.  I'm actually going
to try writing a module for pgsql (despite the existance of pgsql
plugins.)

Anywho, I'm just curious how pam handles groups.  I wanted to store
group information in a pgsql database as well.  For example, if I login
as a user whose login info is all stored in a database (including group
info), when I type "ls" in a shell, how is the information retrieved
that associates user ID and group ID with their names?  Is all that info
retrieved by pam_login?

But then what about a user whose login info is not stored in a db?  Like
root - if I'm logged in as root and am listing files whose uid/gid are
stored in a database, how are their names retrieved?

What I'm going to eventually have is a system using a combination of
unix login (/etc/[passwd,group]) and a postgresql database.  Anyone else
using combined login storage systems?

Thanks!