-The default PAM configuration on most Linux systems uses the local password database in @/etc/shadow@ for all logins. In this case, in order to log in to Arvados, users must have a shell account and password on the controller host itself. This can be convenient for a single-user or test cluster.
+The default PAM configuration on most Linux systems uses the local user/password database in @/etc/passwd@ and @/etc/shadow@ for all logins. In this case, in order to log in to Arvados, users must have a UNIX account and password on the controller host itself. This can be convenient for a single-user or test cluster. Configuring a user account with a shell of @/bin/false@ will enable the user to log into Arvados but not log into shell login on the controller host.