I am trying to find a way of authenticating users on public computers through GDM, but I have a few things to be taken in account. The users do not have a login/password, they only thing they are given is a string. This string is unique and will allow us to identify them. You can see this string as a login without a password. The users must be present in a remote database The users must have the rights to login on the computer they are on at that time. A remote database would check if a booking on the computer had been set for that time by that user. Or if no booking had been made, allow to login. A default user id/home/gid has to be set to the user once logged in I have found ways to deal with most of those requirements, but not altogether. PAM looks nice to set up a custom way of checking if the user booked its computer. NSS MySQL looks nice to set up the environment. Would you know how to set up the environment by myself using a custom PAM module (using pam_python would be preferred)? Or any other method that could help me? Thanks in advance!