Disabling User List in GDM (Gnome 3)
In a multi-user environment you really do not want a full list of usernames being displayed in the GDM login screen for security reasons. In order to disable this feature on my Gentoo lab systems running Gnome 3 and GDM I performed the following actions.
First delete the following file:
/etc/dconf/db/gdm
Then create the directory
/etc/dconf/db/gdm.d
Create a new file in that directory called:
01-mysettings
With the following content:
[org/gnome/login-screen] banner-message-enable=false banner-message-text='' disable-restart-buttons=false disable-user-list=true
Then create a new file:
/etc/dconf/profile/gdm
With the following content:
user-db:user system-db:gdm
Run the following command:
dconf update
Then change over to TTY1 (Ctrl+F1) and restart GDM with:
systemctl restart gdm
Use (Ctrl+F7) to change back to the GDM login screen and you will notice that the user list is now gone. Each user will now be required to type their username before they are prompted for a password.
Reference:
How do I disable user list in GDM
