Password prompt before OS is boot
To re-enable an EFI password:


Boot into Recovery holding Command+R at the startup chime
From the menu bar, select Utilities > Firmware Password Utility
Enter a Firmware password and quit the Utility pane. 


Note that you’ll only be prompted for this EFI password if you attempt to boot the machine differently than you would normally. Otherwise, you’ll boot directly into OS X at startup without being prompted for the EFI password. 

To re-enable a login password:

Open System Preferences. 


Select Users &amp; Groups > Login Options > Automatic Login: OFF