If you have lots of users on your Linux system, or are looking for added local security, you might want to remove the user list from the GDM login screen.
GDM has, for a while now, has defaulted to showing usernames at the login screen. Instead of actually typing your username you just click it then enter the password – very similar to some Windows login screens.
However not everybody wants their usernames shown. To access a computer you typically need a username and password. If someone is physically at your machine they’re already half way to gaining access if they know your username. A lot of Linux systems typically have multiple separate users for FTP, HTTP, MySQL etc so the login screen can also get very cluttered.
Disable usernames from login screen via the terminal
Reverting to the old login screen is easy. One method is to fire up the terminal and use:
sudo -u gdm gconftool-2 --set --type boolean /apps/gdm/simple-greeter/disable_user_list true
Enable usernames from login screen
It can be enabled again by setting it false:
sudo -u gdm gconftool-2 --set --type boolean /apps/gdm/simple-greeter/disable_user_list false
Alternatively (for Ubuntu 10.04+) you can go to System > Preferences > Login Screen and uncheck Show list of users. You will need to unlock it first to make changes.
That’s it. The next time you login you should have to enter your username manually as well as your password.