On Linux and Unix-like systems the Name Service Switch is used to gather entries for the systems name databases.
There are databases such as files, dns, nis and ldap. Is it possible to determine for a given user which service was used to add that entry?
Must further information be gathered from the respective tools for those services or is there a standard set of information NSS gathers besides just a name?
Further how does PAM get credentials from NSS? Is it just the username? Is NSS used when PAM is authenticating over ldap? Does PAM call back to NSS? Is PAM even used in LSAP or other networked logins?
Can NSS be bypassed for some other system or is it heavily baked into the kernel?