Login Using Network Credentials

Problem

Lightdm only lets me log in as a locally defined user or a "guest" user. I need to log in as NIS or Kerberos or LDAP. (Presuming said authentication method is already set up -- ie I can ssh into the system with network credentials, but can't log into the GUI with them.)

Solution

Create /etc/lightdm/lightdm.conf as so:

[SeatDefaults]
greeter-show-manual-login=true
greeter-hide-users=true

Reboot, and you should be able to log in using network credentials.

(Source)