Disable MacBook from Booting Automatically
# Reenable the Mac startup chime sudo nvram BootAudio=%01 # And to disable it: sudo nvram BootAudio=%00 # To reset your Mac to its default behavior sudo nvram AutoBoot=%03
Disable MacBook from Booting Automatically
# for disable autoboot sudo nvram AutoBoot=%00 #/Applications/Utilities/, and then enter the following command syntax exactly: # for Return to Default Setting of Booting sudo nvram AutoBoot=%03