I’ve been meaning to write this up for some time.
Given a Macbook Air with a faulty display, how does one boot it from, say, the Snow Leopard DVD-ROM, in order to access, for instance, Disk Utility to repair the system hard drive?
The only way I’ve found to do this requires first getting Mac OS X running using an external monitor, mouse and keyboard. If you’re not sure how to do this, here’s how. You’ll need a USB hub to connect the mouse, keyboard and USB CD/DVD drive to the Air, and you’ll probably need a micro-DVI to VGA adapter or similar to connect your external monitor to the Air.
Boot the Air by pressing the power button, then close the lid. Press the shift key periodically on the external keyboard to ensure that the Air discovers its existence. After a minute or two (really, this can take a while), the OS X login screen should show up on the external monitor.
Now that you’ve got this out of the way, you’re ready to boot from the DVD.
Put the Mac OS X DVD into the CD/DVD drive, and then click the Restart icon on the login screen. When the external monitor goes blank, hold down the ‘C’ key on the external keyboard. Keep it held down until you see or hear the OS X DVD being read in its drive.
At this point, your Macbook Air should boot up from the OS X DVD. Hurrah!
NB. I haven’t managed, yet, to get this to work by booting from the DVD directly, i.e. without first booting from the HDD and using Restart en route to booting from the DVD. When I tried booting from the DVD directly, the external monitor simply stayed blank.