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Level 2

215 points

OS X won't boot after installing Windows 10 - Late 2013 Mac Pro

(Per Loner T's request, I've created this thread with my post from another topic: OS X doesnt boot, however it only boots to windows)

Note the following:

I used Disk Utility to create the Boot Camp partition. The option to install Windows in Boot Camp Assistant was greyed out.
I used 'gdisk' to convert the MBR from hybrid to protective to bypass the MBR/GPT error in the Windows installer when trying to format the Boot Camp partition to NTFS, as detailed here.

I had no problems rebooting between OS X and Windows shortly after the install, but I believe it's after I had shutdown from OS X, I wasn't able to boot back in. I'm not sure if a shutdown in general caused this issue to arise, but I was last in Yosemite when I had turned off the Mac. Thankfully, I can boot into the OS X recovery partition and manage things there, which is where I restored the Mac partition from a Time Machine backup the first time this happened.

I was able to input the Terminal commands you suggested to Naveedw from there. My SDD doesn't use CoreStorage (No CoreStorage logical volume groups found), so I got no significant output there. Here's what I got otherwise:

Also, when holding down Option after the startup chime, I no longer see "Macintosh HD" as a drive option to boot into. However, in Windows, it appears alongside the C: drive and is even browse-able, but not a startup option in the Boot Camp Control Panel.

Extra information:

I found an old thread from 2010 – Restoring "Macintosh HD" GUID – where the user couldn't boot into OS X, perhaps under different circumstances. The solution there involved DISKPART and 'gdisk' for Windows, both of which I looked into. The first part involved using DISKPART to confirm the type/ID of the Mac partition. The second part is using 'gdisk' to change the Mac partition's GUID back to the proper code as noted in this support article: Changing letter designation of Mac OS X partition via Windows can lead to data loss.

Where I'm confused is that DISKPART shows the Mac partition type as ebd0a0a2-b9e5-4433-87c0-68b6b72699c7, which is not correct (I assume), but 'gdisk' shows the proper GUID code 48465300-0000-11AA-AA11-00306543ECAC (Apple HFS/HFS+). I hope this extra information helps, and thank you for your time.

Mac Pro (Late 2013), OS X Yosemite (10.10.4)

Posted on Aug 20, 2015 5:33 PM

28 replies

Loner T

Level 9

59,471 points

Aug 21, 2015 7:48 PM in response to M Compas

(I'm under the assumption that an erased disk holds no data, UNLESS that disk was formatted with a GUID partition table to which maybe an EFI directory would be created. I don't know much about partition tables or boot loaders; this is just a hunch.)

Your hunch is correct. When a disk is erased, DU creates a default EFI directory specific to that Mac on that disk, because this could be used in the future to boot from. As a test, get a USB that you can erase, format it as Mac OS X Extended Journaled. It will get a disk0s1 which has the EFI directory.

If the Stock SSD was built on this Mac, you can mount the EFI of that disk and check what it has.

The filename is generated and is the same as what you see in System Report -> Hardware -> Boot ROM Version.

On my Mac...

Boot ROM Version: MBP91.00D3.B0B

and the filename is

EFI/APPLE/FIRMWARE:

total 16514

-rwxrwxrwx 1 MyName staff 8454768 Jun 17 09:15 MBP91_00D3_B0B_LOCKED.scap

and my MBP is MacBookPro 9,2 (same generation).

Verify this on your Mac. You want to add the EFI/Apple tree, but not remove anything. The Microsoft part is for the M$ EFI as needed.

M Compas Author

Level 2

215 points

Aug 21, 2015 9:10 PM in response to Loner T

Interesting... Ok.

I copied the stock SSD's EFI/APPLE folder to the installed EFI's folder via cp -R <stock SSD EFI mount>/EFI/APPLE <installed SSD EFI mount>/EFI/APPLE to no avail. I'm not sure if there's any special way to copy the APPLE directory to get OS X to boot properly. I did notice that, unlike you, I have no CACHES directory inside of EFI/APPLE, just EXTENSIONS and FIRMWARE.

The firmware file is MP61_0116_B15_LOCKED.scap. I know the Late 2013 Mac Pro is 6,1, so no surprises there.

I formatted a 32GB USB key in Disk Utility with a GUID Partition table selected for 1 partition. Back in Terminal, there is an EFI partition with just over 200MB of space allocated to it, but when I try to list its contents at the mount point, the directory is blank, even with ls -laR <mountPoint>. No subdirectories, nothing.

Fun fact: I deleted a 2GB USB key and Disk Utility didn't create an EFI partition. I suppose this is why Apple recommend you use at least 16GB for boot disks.

Loner T

Level 9

59,471 points

Aug 21, 2015 9:13 PM in response to M Compas

Yes, that is correct. If you install OS X on the USB now, the Boot ROM is copied to EFI as backup. When a Firmware Update is applied, the EFI partition is also a backing store for the Boot ROM.

CAFEBEEF is a hilarious choice and currently empty.

M Compas Author

Level 2

215 points

Aug 21, 2015 9:29 PM in response to Loner T

I wouldn't mind some CAFEBEEF right now, actually...

I'm going to boot from an Install Yosemite USB key and install OS X on that 32GB USB key. Otherwise, it looked like the installer wanted me to download OS X for install from the internal SSD's recovery partition.

I guessing that I'm supposed to copy the EFI/APPLE directory from the new install onto the internal SSD afterwards.

Loner T

Level 9

59,471 points

Aug 21, 2015 9:33 PM in response to M Compas

M Compas wrote:

I wouldn't mind some CAFEBEEF right now, actually...

I will take the CAFE part. 😉

I'm going to boot from an Install Yosemite USB key and install OS X on that 32GB USB key. Otherwise, it looked like the installer wanted me to download OS X for install from the internal SSD's recovery partition.

If you boot from Local Recovery (Command+R) it will install the OS X version you currently have. If you use Internet Recovery (Command+Opt+R) it will install the version you Mac was shipped with. Please see https://support.apple.com/en-us/HT201314 .

I guessing that I'm supposed to copy the EFI/APPLE directory from the new install onto the internal SSD afterwards.

Yes, but please verify the nomenclature to ensure that Software Update does not change it. There are some recent EFI updates.

M Compas Author

Level 2

215 points

Aug 21, 2015 10:04 PM in response to Loner T

By nomenclature, you mean the name of the firmware file? My unbootable OS X is 10.10.4, and I don't remember – or know – what version of Yosemite the installer will put on this USB key.

Perhaps the changes you speak of are detailed here: About the security content of OS X Yosemite v10.10.4 and Security Update 2015-005 - Apple Support. If so, then maybe I'm safe...

I'd like to say again, thank you very much for your time. It IS getting late, and although I'd like to see this as far as I can tonight, I'm not sure how far you can. Unfortunately, this USB install is c r a w l i n g, and I'll be away from my Mac until Sunday mid-day.

Have a good weekend!

M Compas Author

Level 2

215 points

Aug 23, 2015 4:08 PM in response to Loner T

I've managed to install and boot from OS X on an external drive; the USB key installation was horrendously slow. Unfortunately, after mounting the EFI partition on that drive, it does not contain an EFI directory.

I still have the EFI/APPLE directory copied from my stock SSD onto my internal SSD, but the internal OS X still won't boot. That partition is still labeled "EFI Boot" during startup. My next guess would be that I'd have to use 'bless' to tell the system to use what's in the EFI/APPLE directory to boot from.

Loner T

Level 9

59,471 points

Aug 23, 2015 4:21 PM in response to M Compas

You can also try re-installing OS X on the current installation, which should leave your personal files alone, and only freshen up OS X files.

M Compas Author

Level 2

215 points

Aug 23, 2015 8:48 PM in response to Loner T

I've reinstalled OS X via Time Machine backup, and it's been fine for the past few hours. I've even booted into Windows, shut down, started up in Windows, sleep, wake, restarted into OS X, and here I am. I've also checked the EFI partition and it remains intact from what I've last mentioned.

The first time OS X was rendered unbootable, I ultimately restored a backup and was in OS X again. However, by some means unbeknownst to myself, I couldn't get back in, which led to this thread. Your suggestion of formatting the Windows partition as Free Space was something I didn't do before, so that could be a key factor. I'm still lost on the seemingly empty EFI partition on a fresh install of OS X, the presence of EFI/APPLE on my stock SSD, and how a copy of that directory had no effect on the unbootable OS X. I think I'll draw the line at having to flash firmware and the risk of bricking a $4000 machine.

If push comes to shove, I'll forfeit a Boot Camp install to a Parallels VM. Should the boot issue arise again in the following days/weeks, I'll post again in this thread, but for informational purposes only.

Thanks again, Loner T!

M Compas Author

Level 2

215 points

Sep 5, 2015 9:18 AM in response to Loner T

Hi, Loner T,

I'm just adding this as a follow-up. Yesterday, my OS X was yet again rendered unbootable. Although I can't explain why, the single recurring event throughout my ordeal was that Windows 10 had rebooted itself after a period of inactivity, even though I had the power settings set to not allow the machine to sleep. I was able to boot into OS X once after that, but after waking the machine from sleep on the OS X side, a reboot failed (machine should shut down during boot up, no Apple logo). I double checked the EFI volume from the recovery partition and it remained intact from our previous discussions.

I can't sacrifice my system's stability for Bootcamp anymore, so I'll stick with Parallels.

Loner T

Level 9

59,471 points

Sep 5, 2015 11:01 AM in response to M Compas

For contingency purposes can you install OS X using How to install OS X on an external drive connected to your Mac - Apple Support and use it as backup?

M Compas Author

Level 2

215 points

Sep 5, 2015 11:13 AM in response to Loner T

I believe I was able to do that 2 weeks ago. I tried reinstalling OS X onto a USB key, but that proved to be horrendously slow, so I successfully installed on an old notebook HDD. Last night, however, I reinstalled OS X on a single partition, wiping my dual boot Bootcamp setup, and I've got Win 10 in a Parallels VM as of a couple hours ago.

I'm not a fan of Parallels' upgrade scheme or their subscription pricing (or any app subscription pricing...Adobe...), but it's headache-free, and in the words of the late Mr. Jobs, "It just works."

Loner T

Level 9

59,471 points

Sep 5, 2015 1:22 PM in response to M Compas

Perhaps some of these issues with W10 can be addressed in later BC6 driver packages.

OS X won't boot after installing Windows 10 - Late 2013 Mac Pro