Hide Users List from Login Screen Ubuntu

To hide the user list from the login screen perform following steps (as root user or with sudo)

1) First of all Please take backup of original file, execute following command :-

cp -p /etc/lightdm/lightdm.conf /etc/lightdm/lightdm.conf.orig

2) Open /etc/lightdm/lightdm.conf, Execute Following command :-

vi /etc/lightdm/lightdm.conf

3) Add following line to [SeatDefaults] Selection:-

greeter-hide-users=true

For Example your /etc/lightdm/lightdm.conf should look like below :-
[SeatDefaults]
greeter-session=unity-greeter
user-session=ubuntu
greeter-hide-users=true

Now Save and Exit from file. ( ESC and :wq! )

4) Finally reboot Ubuntu , You will not able to see any user on Login screen/Window

I hope this will helps you all.