I had my Macbook running in Boot Camp. I used the Boot Camp Assistant and selected to reboot into OS X. When it rebooted, it immediately started up into Recovery mode. I did a verify disk and it said that the EFI partition had a problem, so I clicked repair disk and restarted.

On the next restart, there were no startup disks available. "Internet Recovery" is my only option. When I boot into recovery, I see both partitions there, I can mount them and the data is intact. Also, the Startup Disk tool shows both the Boot Camp and OS X paritions as available startup disks, when I select one and hit reboot, it still just shows the flashing folder with a question mark icon.

  • Not sure you can fix (repair) EFI. Using Internet Recovery will fix it. – Ruskes Mar 29 '15 at 20:49
  • When I try to repair the EFI partition map is says "Invalid b-tree node size" and won't repair it. – Chris Thompson Mar 29 '15 at 21:14
  • I have seen something similar after booting to Boot Camp Windows at one point. I was uncomfortable with the ability of Windows to access my HFS+ partitions and used the Device Manager to remove the drive designations for them. Rebooting the system thereafter disabled Mac OS X only. The data seemed to be still there, but no boot option for it. Fixed it by restoring from Time Machine backup and then removed the responsible DLLs in Windows which allowed it to access HFS+ drives in the first place. However, it may not be the same cause for what you experience. – Phoenix Mar 30 '15 at 11:08

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