If you get a bit bored booting up your Mac and waiting for the Apple logo, here’s a trick that will let you see what’s going on behind the scenes. It’s called verbose mode and it simply echoes to your screen everything that the computer is doing while it boots up. It doesn’t change anything about the way the computer operates, it doesn’t speed it up or slow it down, it just displays it on the screen.
To enable “Verbose mode” go into the terminal (Applications/Utilities/Terminal) and type in the following line:
sudo nvram boot-args="-v"