In order to properly implement the passwd command and password aging on your network, the passwd entry of the nsswitch.conf file on every machine must be correct. This entry determines where the passwd command will go for password information and where it will update password information.
Only five passwd configurations are permitted:
passwd: files nis
passwd: files nisplus
passwd: compat passwd_compat: nisplus
All of the nsswitch.conf files on all of your network's machines must use one of the passwd configurations shown above. If you configure the passwd entry in any other way, users may not be able to log in.