The Unix shell can help you keep a close eye on the performance of your Mac—in ways that no graphical Mac OS X program can. For example, did you know you can pause an application that’s running in the background so that it won’t take any of your processor cycles while you’re not using it? After reading this section, you’ll know how to do that and much more.
During the normal boot-up sequence for Mac OS X, you see a gray logo in the middle of the screen with a spinning progress wheel just below it. Hey, that’s all well and good from a cute icon standpoint. But if you ever want to see what really happens when your machine boots up, hold down
-V just after you press the power button or the reset switch. This key combo, known in Geekville as verbose mode booting, reveals all the underlying Unix processes at work.
Some ugly white text on the black background shows you exactly what Unix is doing to boot your machine. The messages flicker by very quickly while the computer starts up, but you can still read them once it’s finished. (Unfortunately, the messages aren’t likely to make any more sense when you can actually read them.) If you’re curious to see what happened when your computer started up, launch Terminal and type dmesg | less. (The less command makes the long dmesg results scroll one page at a time.)
Enough of ...