Add a message to the login screen

The login screen of OS X by default only shows the computer name. It is however possible to add a message or warning to the login screen. Use following command to do this.

sudo defaults write /Library/Preferences/ LoginwindowText "Your Message"

Replace “My message” with the text that you would like to be displayed.

Revert to defaults setting:

sudo defaults delete /Library/Preferences/ LoginwindowText