While in general day-to-day use, turning on and booting your Mac is simply a matter of pressing the Power button and waiting for OS X to load, there are occasions when you need to perform certain actions during the OS X startup process. These can range from choosing to boot from a selection of drives or discs to viewing the full UNIX text as the operating system loads to enable you to troubleshoot issues with your Mac.

In this guide, we’ll take you through he complete list of Mac OS X startup keyboard shortcuts for use as a future reference. With each of these keyboard combinations, the respective keys should be held down from the moment you hear your Mac’s “Chime” system sound till the desired result appears.

Startup Keyboard Shortcuts

Option (Alt) – This button launches the Startup Manager application. This will present you with a horizontal list of icons displaying all available volumes you can boot from, such as hard drives, partitions and discs. Navigate to the desired volume with the Arrow keys and select by pressing Return.

C – Related to the above command, holding this key will start your Mac from a bootable DVD or CD disc in its drive.

X – Again, another key command related to the Startup Manager. This key will force your Mac to boot into OS X even if other bootable volumes or operating systems are present.

T – This command will start your Mac as a Firewire Target disk, allowing another Mac to connect to it via a firewire cable as if it was an external hard drive.

N – This will boot your Mac from a networked drive.

Shift – This is a vital startup keyboard shortcut if you are experiencing issues with your Mac. Holding down this key will boot your Mac into Safe Mode. Safe Mode will perform an automatic check of your startup volume and only load essential system extensions – it will disable all other startup items that may be preventing your Mac from booting.

UNIX Startup Commands

Mac OS X is built upon a foundation of UNIX, a venerable operating system renowned for its safety and stability. Sometimes experienced users may require the ability to issue commands or observe the UNIX underpinnings during the OS X boot procedure for troubleshooting purposes. There are a number of keyboard shortcuts for use in this situation.

Command (⌘)-S – This key combination will boot your Mac into Single User Mode. In this mode, OS X will load without a Graphical User Interface and will essentially boot directly into a Terminal Console.

Command (⌘)-V – This starts up OS X in Verbose Mode. Your Mac’s screen will display text showing all the underlying processes occurring during the boot. An example of how this appears is below:

For the experienced OS X/UNIX user, Verbose Mode provides a plentiful supply of information about exactly what is occurring as OS X boots, allowing them to troubleshoot any issues preventing the correct functioning of the operating system.

With this collection of OS X startup keyboard shortcuts, Mac users are able to exert control over the booting process with just a few key presses, and they are invaluable if you should ever run into any issues with your Mac hardware.