Linux Password Administration

[Judge Stone]

Just a quick question for the experts out there.

Presently in a Windows 2000 AD domain we have approximately 200 users
with Win 2k Machines and about 10-20 linux box users.

In this enviroment we are told to have the Win2k Users change their
passwords every 90 days and this is controlled through the AD by
manually setting each user or using Ideal Administrator and having all
users change their passwords at the same time.

The question has been asked of me is how do we ensure that the Linux
Users are changing their passwords every 90 days since they are
presently only authenicating against a "local" account on the Linux
Box?

I am reseaching PAM along with LDAP and we do have LDAP for the AD
Users since AD uses LDAP and also a LDAP for Mail Server addressess.

Can someone point me in the right direction as to how to approach
ensuring that we can have the Linux users change their passwords every
90 days along with the AD users.

A link to a good How-To, CookBook, or just plain out suggestions are
extremely welcome.

Im sure there is an easy answer to this but a somewhat complicated
procedure. Im willing for the challenge, If I can just get started in
the right direction.

Please post and reply.

Thanks,

Judgestone