Startup key combinations for Intel-based Macs

Learn about the startup key combinations you can use with Intel-based Macs.
Products Affected

MacBook Pro, MacBook Air, MacBook, iMac, Mac mini, Mac Pro
Keystroke Description
Press C during startup Start up from a bootable CD or DVD, such as the Mac OS X Install disc that came with the computer.
Press D during startup Start up in Apple Hardware Test (AHT).
Press Option-Command-P-R until you hear two beeps. Reset NVRAM
Press Option during startup Starts into Startup Manager, where you can select a Mac OS X volume to start from. Note: Press N to make the the first bootable Network volume appear as well.
Press Eject, F12, or hold the mouse or trackpad button Ejects any removable media, such as an optical disc.
Press N during startup Attempt to start up from a compatible network server (NetBoot).
Press T during startup Start up in Target Disk Mode.
Press Shift during startup Start up in Safe Boot mode and temporarily disable login items.
Press Command-V during startup Start up in Verbose mode.
Press Command-S during startup Start up in Single-User mode.
Press Option-N during startup Start from a NetBoot server using the default boot image.

Restarting your Mac
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Restarting your Mac is easy, though very seldom necessary since the introduction of OS X, which prevents application problems or crashes from affecting other applications or the operating system. To fix problems, quitting and restarting the problem application usually works. If the problem affects more than one application, simply logging out of your account and back in will fix it. Generally speaking, the only time a restart is really necessary is after installing software that touches system files, and the installer will inform you that a restart is necessary.

There are a number of ways you can restart a Mac. You can:

* If you need to restart your computer after installling a piece of software, the installer may provide a "Restart" button. In such circumstances, simply click the button
* Go to the Apple menu and choose "Restart…"
* Press control-eject and choose "Restart" from the window that appears, or press command-control-option-eject
* You can press the power button and choose "Restart" from the window that appears
o Note that on PowerBooks, iBooks, and MacBook Pros the eject key does not respond immediately as do desktop keyboards. You must hold down the eject key for a few seconds, just as if you would be ejecting a disk.

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Force Restarting

If you particularly wish to, you can force your Mac to restart. You need to do this after a Kernel panic.

To force restart your Mac:

* On some Macs, press control-command and the power button or control-command-eject at the same time.
* On most Macs, hold the power button for five seconds to force shutdown, and then push the power button again to restart.

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System Startup Key commands

In some cases you may want to make some modifications to the system, boot to an other OS, or even just clear the Parameter RAM during a system restart. The following Keyboard commands will help you enable, disable, or select some of the boot options. All key combinations need to be pressed (and held) directly after you hear the startup chime. The key " Command" signifies the Apple button on your keyboard.

* T= Target disk mode - your Mac is an external hard drive for other Macs
* C= Boot from CD or DVD
* R = Forces some powerbooks to reset the screen
* X = Boot to OS X on systems with dual boot
* Command+V = Starts your system in Verbose mode. (lists what is loading during startup, as opposed to the spinning icon with grey screen)
* Command+S = Single user mode (used for troubleshooting in most cases)
* Command+Option+P+R Zaps Parameter RAM (Note: Make sure to push this key combination directly after the startup chime, and hold the keys until you hear the startup chime again.)