Verbose mode is a diagnostic function built into all Macs. What this allows you to do is witness the behind the scenes processes that run while your machine starts up. One way to enable this for a single boot session if you just want to see it is hold “command” and “v” keys during boot.
It can be fun to look at occasionally or for diagnostics, and the next time you start up, your machine will boot normally. During extended diagnostics we sometimes set machines to start up in verbose mode by default, and of course you can do this to for fun if you’d like.
First thing you need to do is open the application Terminal. Terminal is located in the Utilities folder on your Mac. Once running terminal enter the following command:
sudo nvram boot-args= “-v”
Now if you want to see the effects of this, close Terminal and restart your machine. This is a tool that most people will not need to use, but comes in handy if you are having issues during boot, and want to see what errors are presented.
If you do this, and you want to revert to the normal graphic boot, open Terminal again, and enter this command:
sudo nvram boot-args=
This will disable this, and bring your computer back to normal Mac OS X boot.