Your Mac has many secret abilities when you first turn your computer on, and you may have already discovered one or two of these, especially if you’ve ever had to troubleshoot startup problems. This article is a simple list of the startup commands I’ve used over the years. Hopefully it will serve as a quick guide for you. To perform a startup key combination, you simply hold down the keyboard key(s) corresponding to the appropriate purpose when you turn on your Mac. In an ideal world, you hold the keys down while pressing the power button, but some tricky combinations likely require you to press the power button and then very quickly hold down the keys on the keyboard (before the startup sound finishes playing). As you already know, the normal boot sequence is: black screen –> gray screen –> gray screen with Apple logo –> gray screen with Apple logo and spinning gear –> desktop. You should continue holding down these keys until either the gray screen switches to something other than the Apple logo, or if your command needs to boot the computer, hold them down until the Apple logo appears with the spinning gear. Lastly, remember that resetting PRAM/NVRAM will restart your computer, so once your computer reboots while you hold down the Command-Option-P-R keys, you can let go. Hope this helps!
Key Combinations for Booting from Various Disks
| Key Combination | Purpose |
| C | Start up from a bootable CD/DVD (in the drive) |
| N | Boot from a NetBoot server |
| Command-R | Boot from Recovery Petition (Lion only) |
| Option | Start the Startup Manager, which lets you choose to boot from any bootable source |
| Delete-Option-Command-Shift (DOCS) | Skip booting from the default boot disk and instead look for any other available boot disk |
Key Combinations for Troubleshooting Hardware Problems
| Key Combination | Purpose |
| D | Intel Macs: Boot from the Apple Hardware Test partition on the appropriate DVD (PowerPC users must hold down “Option” and boot to the Startup Manager to run the Apple Hardware Test) |
| Command-Option-P-R | Resets the NVRAM/PRAM |
| Command-Option-O-F | PowerPC Macs: Boot to Open Firmware (command line) |
Key Combinations for Troubleshooting Operating System Problems
| Key Combination | Purpose |
| Shift | Mac OS X starts in “safe” mode |
| Command-S | Mac OS X starts in “single-user” mode |
| Command-V | Mac OS X starts in “verbose” mode |
Miscellaneous Key Combinations
| Key Combination | Purpose |
| T | Put the Mac into “target disk mode,” which allows other Macs to access your internal hard drives via FireWire or Thunderbolt |
| 6-4 | Allows compatible Macs to boot with the 64-bit kernel if they normally boot from the 32-bit kernel (Snow Leopard only) |
| Eject/F12/mouse or trackpad button held down | Eject a CD/DVD currently in the drive |
Are there any key commands missing from this list? What tricks do you have at startup? Let others know in the comments.
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