The computer is a MacBook Air. I have OSX Yosemite and Linux Ubuntu 14.04 dual boot. I messed up and damaged my Mac EFI and hence OSX ceased to work. Recovery disk was destoyed too. FileVault is on and I just changed my login password (which I remember but can not use) before the problems appear.

Please help..

  • You might not be ably to fix it without starting from scratch. Do you have a Time Machine backup? – user3439894 May 15 '15 at 21:20
  • Which model Air? Some support internet recovery, others will need a to be serviced by someone that has a netboot server set up. – bmike May 15 '15 at 21:33
  • I do have a Time Machine backup on an external drive..but I do not think it works.. – Y Z May 15 '15 at 23:58
  • Also I get a prohibitory sign when I try to log in.. – Y Z May 16 '15 at 0:48

If you have access to another mac, you can make a yosemite bootable install usb. http://liondiskmaker.com/ has a applescript program that will creae one, you just need a usb stick with 8gb and the installer downloaded. Boot the messed up computer from the USB stick by holding shift during the boot sequence and selecting the USB stick.

There you can restore from time machine if your time machine works. Otherwise just reinstall over your old install. It shouldn't delete data but messing with the EFI is always dangerous and might need to be repartioned.

If that is the case you could try booting from an external mac, either with a harddrive that has mac, or time machine etc, and with that you should hopefully be able to mount the messed up disk partition that has the data and get your data off it.


If you have a Time Machine backup connected, you should be able to boot your mac while pressing the ALT-key and select the Time Machine backup. Most likely you will have to delete your internal harddrive and reinstall from the backup.

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