Basic key combinations tested on OS X 10.6 to allow more Mac boot options. These are mostly used for diagnostics.
Hold these keys down until you see a different startup screen than normal:
|Option (a.k.a. Alt)||Boot Menu (use this to boot CDs)|
|d||Boot into hardware diagnostics (F2 also works)|
|Shift||Boot into Safe Mode (similar to Windows safe mode – basic OS X functionality – no kernel extensions)|
|Command-S||Boot into Single User mode|
|Command-Option-P-R||Reset PRAM & NVRAM (RAM that stores hardware settings). Hold this combination down until you hear the second OS X startup chime. This is useful if you have a gray screen on boot.|
Note: if any of these key combinations fail and you are using a wireless keyboard, use a wired keyboard. If you are using a Macbook, just use your built-in keyboard.
- Command – ⌘
- Option – ⌥
- Shift – ⇧
- Control – ⌃
- Power – ⎋
- Eject – ⏏
Additional Mac Startup Key Combinations
This mac startup key combo article from Apple support shows a couple more options in case you're interested. If your Mac is using a firmware password, all of these key combinations are disabled, except as noted in the article.
That's all for now with this Mac boot options article. Is there a startup option you can't live without? What about one that wasn't featured in this article?