I would like to monitor the messages generated when I boot my Mac, similar to what you on a *nix box. Is there key-combo to press/hold that will let me do this?
You have to press cmd + v upon startup to see the boot output. Press this right after the chime.
If you want to make that permanent, you should probably do something along the lines of:
To undo the above:
in the Terminal. (/Applications/Utilities/Terminal.app)
note: I haven’t tested the above commands, but I’m sure a google query will help you there if you want to make it permanent.
If you want to see the boot messages after the boot occurred, log in and run