iMac Boot Options

Written by john bland
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An Apple iMac computer can be rebooted to utilise several helpful features. If you've been experiencing trouble with your iMac, try a special reboot to automatically fix some problems, test for possible issues or to reinstall your operating software. You can also connect to other computers and networks using certain codes. To use these boot options, simply start or restart your computer and press and hold the particular buttons when you hear the start-up chimes.

Basic Troubleshooting Options

Press "C" when rebooting to start up from a disc, usually your most current Mac OS Install disc. This function can reinstall your iMac's basic software without deleting your files. For the Apple Hardware Test, press "D" when booting. When the iMac finishes starting up it will automatically begin a test to detect any hardware problems that may be causing issues. To eject a CD or DVD from the optical drive, restart holding either the Eject button or "F12". Press "Shift" to use your iMac's Safe Boot mode. This disables your login items. You can then remove problematic login items under System Preferences. Press the space bar when starting to load the Extension Manager. Similar to the Safe Boot mode, this option lets you change and remove extensions that may be causing trouble.

Advanced Troubleshooting Modes

Press and hold "T" to access Target Disk Mode with your iMac connected to another Macintosh by a FireWire cable. Your hard drive will appear as a folder on the other computer's desktop, and that machine can perform Disk Utility functions for your iMac. Use V for "verbose" mode, which displays a log of functions occurring at start-up, shutdown and when logging in or out. Verbose mode can be informative if your iMac is slow during these times. Use S for "single-user" mode. Here you can view and adjust elements of your operating system and software using advanced UNIX commands.

Other Startup Modes

The Option key will load your computer into the Startup Manager which lets you choose a volume to start from, if you have extra drives installed or connected. Press N during start-up to use Apple's NetBoot feature, which lets your iMac load from the operating system of a network server. This is handy if you transport your iMac between home and work and want to move on and off a server. To reset your paramater and non-volatile random accessory memory, press Command-Option-P-R. These forms of RAM retain their data even when a computer is shut off, and this function resets them completely.


With a frozen iMac that won't respond to commands, a safer alternative to unplugging it completely is to locate a pinhole on the back of the machine where you can insert a pin (or flattened paper clip) to restart the computer. If you use a wireless keyboard with your iMac, try holding the appropriate buttons down before the start-up process even begins rather than after the chiming sound. Your iMac may not register a wireless keyboard's commands as it would with a wired keyboard.

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