Before installing the Linux PAM client on Ubuntu 16, you must complete the preinstallation process to configure lightdm to accomplish the following:
Allow manual login
Hide the user list
Disable guest login
For more information about lightdm, see LightDM.
To configure lightdm on Ubuntu 16, perform the following steps:
Navigate to /usr/share/lightdm/lightdm.conf.d.
Double click the 50-ubuntu.conf file and add the following parameters:
[SeatDefaults]
greeter-show-manual-login=true
greeter-hide-users=true
allow-guest=false
Click Save.