It seems like the people who truly know how their Mac works inside and out can do odd things with it by holding down a key, or a combination of keys, as the machine boots. Table A-1 lists the known boot keys that can be used when Mac OS X is starting up.
Table A-1. Keyboard shortcuts used for starting, restarting, logging out, and shutting down
Key command | Description |
|---|
C | Holding down the C key at startup boots from a CD or DVD (useful when installing or upgrading the system software). |
N | Attempts to start up from a NetBoot server. |
R | Resets the display for a PowerBook. |
T | Holding down the T key at startup places your Mac into Target mode as a mountable FireWire drive. After starting up, your screen will have a blue background with a floating yellow FireWire symbol. Target mode makes the hard drive(s) of your Mac appear as mounted FireWire drives when connected to another system. To exit Target mode, press the Power-On button to turn off your Mac. After your Mac has shut down completely, press the Power-On button again to restart your Mac. |
X | Holding down the X key at startup forces your Mac to boot into Mac OS X, even if Mac OS 9 is specified as the default startup disk. |
 -S
| Boots into single-user mode (something you'll only need to do when troubleshooting your system, or if you're a system administrator). |
-V | Boots into verbose mode , displaying all the startup messages on screen. (Linux users will be familiar with this.) |
Shift | Holding down the Shift key at startup invokes Safe Boot mode , turning off any unnecessary kernel extensions (kexts) and ignoring anything you've set in the Accounts preferences panel. |
Option | Holding down the Option key at startup opens the Startup Manager , which allows you to select which OS to boot into. |
Mouse button | Holding down the mouse button at startup ejects any disk (CD, DVD, or other removable media) that might still be in the drive. |
Shift-Option--Q | Logs you off without first prompting you. |
Option +  Log Out | Option-Power-On | |
Option + Shut Down | Shuts down your system without first prompting you. |
Option + Restart | Restarts your machine without first prompting you. |
Control--Power-On button | Forces an automatic shutdown of your system; this should be used only as a last resort, because it could mess up your filesystem. |
Control-Eject (F12) | Opens a dialog box that contains options for Restart, Sleep, and Shutdown. |
Control-Option--Eject (F12) | Quits all applications and shuts down the system. If there are any application windows open with unsaved changes, you will be prompted to save the changes before the application is forced to quit. |
