Ubuntu 17.10: Disable user list in GDM

This feature is currently bugged, see: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1724944 and mark yourself affected

You need to install the dconf-editor tool if you not have already:

sudo apt install dconf-editor

Then when you opened it navigate to:

/org/gnome/login-screen

and set the 'disable-user-list' button to 'on':

Since the above is still bugged, the only solution is right now via terminal edit the following lines in /etc/gdm3/greeter.dconf-defaults:

#[org/gnome/login-screen]
# disable-user-list=true

to:

[org/gnome/login-screen]
disable-user-list=true

Be sure to edit both lines otherwise you might crash your login completely.

One option:

Edit /usr/share/gdm/greeter.dconf-defaults and remove "#" to uncomment the line:

disable-user-list=true

Another option:

Use gconftool-2 or gconf-editor. Change this value to true:

/apps/gdm/simple-greeter/disable_user_list

Reference

https://help.gnome.org/admin/gdm/stable/configuration.html.en
https://mike632t.wordpress.com/2016/05/28/gnome-3-customizing-the-login-screen/#userlist