The Gnome login screen normally shows a list of available users to log in as. For those who want to disable showing the user list, and manually type a username to login with, below I will show you how.
Open terminal by pressing Ctrl+Alt+T on keyboard, when it opens, run following commands one by one:
1. Run command to get access to root:
Type in your password (no visual feedback while typing) when it prompts and hit Enter.
2. Then switch to user
gdm, which is required to run gsettings to configure gdm settings.
su gdm -s /bin/bash
3. Finally hide user list from login screen using Gsettings:
gsettings set org.gnome.login-screen disable-user-list true
After that, restart your computer and enjoy!
How to Restore
To restore the change, open terminal and re-do previous steps, except running the last command with:
gsettings set org.gnome.login-screen disable-user-list false