Every once in a while you might have a problem with your Mac that requires your action during startup. Those users with bootcamp installed may be familiar with the action for selecting an operating system during startup. If you install new hardware there is another key sequence required during startup to clear a special memory inside your Mac. Read below to find a list of startup sequences and learn about what they do.
First thing you need to know is when in the startup sequence are you required to press the keys and for how long. Answer is immediately after the power button is pressed before the grey screen shows - keep holding the keyboard sequence until either the apple logo shows, Mac restarts or boot options appear.
Option button (Show startup options) - When pressed during startup this will initiate your Mac to search for partitions and operating systems. You might not know, but your Mac is pretty clever and if we were to remove the hard drive and place it in an external dock via USB, Firewire or Thunderbolt, it could boot from this drive and load OS X as normal - well maybe a bit slower if over USB, but it will be fully functional. This process also allows us to install OS X using a USB key, or boot into the Windows partition installed using bootcamp.
C button (Load OS X DVD drive) - Will force your Mac to load OS X from the CD/DVD drive
D button (Diagnostics) - Will start the hardware diagnostic routine. You may require your original grey OS X installation DVD be in the DVD drive for this to work. Lion users will have a recovery partition on their hard drive where the diagnostic program is located. This can be useful for finding hardware problems including bad memory, hard drives, DVD drive, logic board, airport or bluetooth card etc.
N button (Network Boot) - Starts the network boot option for netboot installations
T button (Target Disk Mode) - essentially turns your Mac in an external hard drive enclosure. Just connect a USB, Firewire or Thunderbolt cable to another Mac and it will behave just like an external drive. Useful for repairing damaged file systems, system upgrades and migrations to a new computer. Also can be used to test certain display / graphics problems.
Eject or F12 or Mouse button or Trackpad button - starts the force eject of media in the CD/DVD drive. If it's really stuck, best to book an appointment with us to free the media from your delicate DVD drive.
Command + Option + P + R (clear NV-RAM) buttons simultaneously - Will clear the programmable and non volatile memory in your Mac. We use this when installing new hardware or to clear error codes during problem investigations. The Mac will restart and chime a second time to signify completion of this process. You only have to hold the combination until the Mac restarts the first time.
Command + Shift + V (Safe mode with verbose) buttons simultaneously - Starts your Mac in Safe mode with full verbose (a list of everything the Mac is doing in sequence is displayed on screen) to assist with error identification with software / hardware.
Shift (safe mode) button - Starts OS X in safe mode. All login items associated with your user profile and open at login applications are not loaded at startup to help troubleshoot system errors.
Command + V (Verbose) buttons simultaneously - Displays the full verbose mode on screen without going into safe mode. Another diagnostic tool used by IT people trying to identify issues during the startup sequence.
Command + R (Recovery) buttons simultaneously - Starts the Lion recovery utilities for when you don't have DVD installation DVD to use with the new Macs.
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