Information
Prompting the user to enter both their username and password makes it twice as hard for unauthorized users to gain access to the system since they must discover two attributes.
Solution
Perform the following to implement the prescribed state:
1. Open System Preferences
2. Select Users and Groups
3. Select Login Options
4. Select Name and Password
Alternatively:
1. Run the following command in Terminal
sudo defaults write /Library/Preferences/com.apple.loginwindow SHOWFULLNAME -bool yes