Question

Which directory system uses the concept of user file directory and master file directory?

Answer 1

In some configurations Linux users are stored in a network directory like LDAP or NIS.

With the right settings for LDAP and Kerberos, Linux can even get users from a Microsoft Active Directory server.

LDAP or NIS  bypass the regular /etc/passwd by using glibc’s NSS in /etc/nsswitch.conf and the PAM configuration in /etc/pam.d