Ubuntu 12.x / 13.x
allow-guest=false
Ubuntu Tip:How to disable guest account in ubuntu 12.04(Precise)
Disable guest account in Ubuntu 13.04
Ubuntu 14.x
$ sudo sh -c 'printf "[SeatDefaults]\nallow-guest=false\n" > /usr/share/lightdm/lightdm.conf.d/50-no-guest.conf' $ sudo sh -c 'printf "[SeatDefaults]\ngreeter-show-remote-login=false\n" >/usr/share/lightdm/lightdm.conf.d/50-no-remote-login.conf'