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enter image description hereOn Mac Book Pro retina ( 2014 ) Mavericks running Boot Camp, one hard drive partitioned to dual boot OS X and Windows 8.

While messing on Windows 8 I mistakenly deleted a partition which is now showing unallocated 621 MB, using Disk Management. ( it was showing a weird phantom SD drive which i thought was some improperly mounted ).

OS X won't boot and won't show in Boot Camp. Cmnd + R goes into internet recovery. My main data HD Mac partition is fine and accessible ( can copy data at least to backup my files).

I never attempted any formatting and stopped a Windows partition recovery utility as i googled further and turned out it is(maybe) a bad idea.

How can I recover this partition/get back into OS X without losing data, having to reinstall both OS X and Windows?

Edit: Just run diskutil list and this is what I get.

  • Seasoned advice: don’t delete partitions if you don’t know what they’re for 🙌 – brandonscript Feb 14 '18 at 8:32
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Presumably you deleted the recovery partition, which is about that size. Boot into Internet Recovery, start the terminal and type diskutil list. If the OS X partition is still there, you should see it as formatted with CoreStorage (OS X doesn't require the recovery partition for a normal HFS+ formatted partition). If it exists, then the solution is to do a reinstall of the OS. This will not erase anything, but it will recreate the recovery partition. Note that you'll have to unlock your disk first if it's locked by FileVault 2.

Lesson for the future: Windows doesn't know anything about CoreStorage volumes, even with all the BootCamp drivers installed. Do not trust anything you see regarding your disks from within Windows, unless it identifies the disk as a format it knows.

  • Than you for the answer. – catpanda May 12 '15 at 20:54
  • Today i tried to reinstall OSX via internet recovery and run itno 2 problems: 1. I had no option to start terminal at all, no "utility", just disk utility to erase disks 2. No disk to select when I picked the install OS X does it mean I have to do a complete erase and re-install, any options? – catpanda May 16 '15 at 9:30
  • After a 5010F error from the Apple server which was probably something on their side - i run diskutil list but I don't know enough to decipher what I am seeing. I edited my original comment and added the diskutil screenshot there. – catpanda May 16 '15 at 12:28
  • Is there any hope of getting my OS X back? 1. with above result of diskutil list 2. with the fact that on trying to re-install OS X - internet recovery couldn't find a disk to reinstall the os X on, just drew blank. Windows 8 install continues to be alive and well, now that i have almost completely migrated to using osx and loving it, which is problematic as i never had to troubleshoot anything or learn anything, until now. – catpanda May 16 '15 at 13:10
  • @DavidAnderson I use bootcamp and there i can pick which OS to boot. 1. OS X has disappeared from Bootcamp Assistant altogether.2. No combination of keys could get me into OS X - it either goes into Internet Recovery or boots Windows – catpanda May 16 '15 at 13:14
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I am writing this so anyone else in my situation can learn from the experience in case they google it. I am not knowledgeable and have no clue about Os X, I was unable to resolve my situation in a timely manner and what I ended up doing is reinstalling both OSX and Win, it took less than 24 hrs. Don't do it if you know what you are doing but I had no other way of getting a hold of my machine again. Important lessons:

  1. NEVER MESS with your WINDOWS DISK MANAGER on Dual Boot Mac Book Pro.
  2. BACKUP BOTH MAC and WIN side before attampting any fix, copy and paste important files, settings, preferences, etc
  3. Used Internet Recovery to Re-Install Mc OS X, Installer couldn't find a working OS X drive and had to erase and format my mac partition as Mac OS Extended (Journaled).
  4. During Internet Recovery I got stuck and looked up the log window and had an error "Recovery Chunk Validation Failed". Resetting NVRAM helped - Command (⌘), Option, P, and R.
  5. Re-Installing OSX caused my Windows partition to DISAPPEAR. GONE.
  6. Re-installed Win so MAKE SURE TO HAVE WIN ISO, HARDDRIVE that can be formatted ready.
  7. Had another windows machine nearby to troubleshoot issues while going through this.

Which was fine because I was prepared. My solution was not smart and I lost both my OSX and Win installations, BACKUP YOUR STUFF!, but I have a working MAC today. Also - I had too much space dedicated to the Win install with a lot of apps crashing so this was a chance to get rid of the old Win install. That's it - thank you everyone.

Important: I am also abroad.. and the nearest Apple store is in another country. Otherwise I would have gone the Apple store route.

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