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Mac Startup Options – Keyboard Shortcuts

written by: Joli Ballew•edited by: J. F. Amprimoz•updated: 2/5/2009

Have a startup emergency? Check out these keyboard shortcuts that will help you bypass a primary startup volume, force a specific OS version to start, or start in single-user mode, to name a few.

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    There are quite a few keyboard shortcuts you can apply during startup:

    • X--Holding down the Command + X key during startup will force OS X to start. This is useful if you have another version of the operating system set as the default.
    • Option + Command + Shift + Delete--Holding down this key combination during startup will force your Mac to bypass the primary startup volume and look for a startup volume on a CD or external disk.
    • C--Holding down this key during startup will force your Mac to start from a CD (if the CD has a System folder).
    • T--Holding down this key during startup will force your Mac to start in FireWire Target Disk mode. (This lets you turn your Mac into an external hard drive for another Mac. It’s great for exchanging information between laptops, iPods, and similar devices. For more information, refer to Chapter 13.)
    • Shift--Holding down this key during startup will force your Mac to start in Safe mode. This disables unnecessary kernel extensions and login items.
    • Command + S--Holding down this key combination during startup will force your Mac to start in Single-User mode. This is the command line.
    • Command + Option + P + R, hold until you hear the startup sound a second time--Holding down this key combination during startup will force your Mac to reset its PRAM. PRAM, or parameter RAM, is a small amount of RAM that stores settings of several control panels and system software. This includes the date and time, the choice of startup disk, and similar information. If suspect your PRAM is corrupt because these settings are not retained after a reboot, use this key combination to “zap the PRAM.”
    • Command + S, then type /sbin/fsck –and typing y at the prompt--This key combination will force your Mac to run some basic file system checks at startup. This is a good tool to use when the computer is “acting funny” and when first starting troubleshooting tasks.
    • Command + Options + O + F, then type eject cd at the prompt--This key combination will force your Mac to eject the CD.