Boot Keys for Mac OS X System Start

Every Mac has a variety of optional boot functions that can be used to intervene during the OS X system startup. These are typically in the form of a single keys held down, or a press of keystrokes and hotkeys, used to issue a command and thereby adjust the booting behavior of Mac OS X. The effects are varied, and can be desirable for a wide variety of applications.

The booting keys available to Macs upon OS X system start are listed below. To use these and to gain the desired effect on the system, start holding down the appropriate key or keystroke immediately after hearing the boot chime on a Mac – that can either be booting from a cold machine, or during a system restart, just be sure to hold down the appropriate key early enough in the loading process to gain the effect, otherwise you’ll need to reboot and try again.

Mac Boot Modifications Keystrokes & Effects on OS X System Start

These will be listed as the boot keystroke followed by the effect on OS X:

• Option – Boot directly to the Startup Disk manager
• Command+R – Boot into Recovery Mode of OS X (modern versions of OS X only)
• C – Boot from a CD/DVD
• T – Boot in Target Disk mode (FireWire or ThunderBolt only)
• N – Boot from an attached network server (NetBoot mode)
• X – Attempt to force Mac OS X to boot
• Shift - Boot up in ‘Safe Mode’ which has limited functionality but disables third party extensions
• Command+V – Boot into Verbose mode
• Command+S – Boot in Single user mode

I find myself using all of these tricks relatively frequently in Mac centric IT work, but even for home users they may be necessary from time to time in order to perform a variety of tasks, whether troubleshooting, repairing, or just learning about a Mac.