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

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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

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Answer 1

Loner T

Level 9

59,471 points

Aug 20, 2015 5:58 PM in response to M Compas

Do you want to install Windows using EFI Boot (better) or the typical BIOS mode (slower)? Your Mac supports both.

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Answer 2

M Compas Author

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Aug 20, 2015 6:55 PM in response to Loner T

I suppose I'd want to use EFI Boot, if that's the future-forward solution.

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Answer 3

Loner T

Level 9

59,471 points

Aug 20, 2015 7:01 PM in response to M Compas

EFI Boot requires the disk space to be made into a Free Space partition. It will be split into MSR and MSD parts by the Windows installer on pure GPT disk. You already seem to have Windows installed partially. Do you want to delete it?

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Answer 4

M Compas Author

Level 2

215 points

Aug 20, 2015 7:08 PM in response to Loner T

Sure, I don't mind testing this out. My boot options at this point are a Windows 10 installer via USB key, Yosemite installer via USB key, and the OS X Recovery partition.

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Answer 5

Loner T

Level 9

59,471 points

Aug 20, 2015 7:56 PM in response to M Compas

You can use diskutil eraseDisk and make the current Bootcamp partition into freespace with the following Terminal command.

diskutil eraseVolume free BOOTCAMP disk0s4

A. Direct Boot from W10 USB, or,

B. Run BCA and click on Create USB... and Download Software... and build a USB installer and boot from it and install W10.

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Answer 6

M Compas Author

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215 points

Aug 20, 2015 9:29 PM in response to Loner T

So, Windows 10 successfully installed, but I still cannot select Macintosh HD as a bootable drive after holding Option during startup. OS X is still not visible as an option in the Boot Camp Control Panel in Windows either.

However, I have noticed some changes in Windows. The drive designation for Macintosh HD has changed from E: (as seen in one of the pictures in my original post) back to D:. Also, Windows has installed itself in partition 5 (disk0s5 I assume) while disk0s4 has become a 16MB partition. I guess this is the MSR and MSD you mentioned earlier.

Now when I boot into Windows, I'm presented with a drive selection screen, asking me which Windows drive I want to boot from. It's not an issue, just a minor inconvenience; my main concern is still getting OS X bootable again.

FYI, when I ran the Terminal command, after the BOOTCAMP partition was unmounted (as mentioned by diskutil's output), the next line of output mentioned something like – and this isn't verbatim – 'POSIX error, file or folder not found'. I double checked Disk Utility and the BOOTCAMP partition wasn't listed. That partition, however, was visible in the Windows installer with no need to format to NTFS (the Format button was greyed out anyway), and was even visible as a boot option during startup when I had to select the Windows USB key. This is probably irrelevant in the grand scheme of things, but I thought I'd just mention this.

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Answer 7

M Compas Author

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215 points

Aug 20, 2015 10:05 PM in response to Loner T

Just to see what would happen, I selected the drive labeled 'EFI Boot' during startup. The Apple logo appeared and after the progress bar reached 30%, the computer just shuts off. This has happened before, the boot issue with OS X after installing Windows 10. I just wanted to confirm if 'EFI Boot' happened to be the OS X drive.

Normally, the progress bar would reach about 10% before properly booting into OS X. It's usually fairly quick.

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Answer 8

Loner T

Level 9

59,471 points

Aug 21, 2015 1:13 PM in response to M Compas

Either using Local Recovery (or Internet Recovery as necessary), or installing OSX on an external disk - OS X: Installing OS X on an external volume - Apple Support - can you post the output of

sudo gpt -vv -r show /dev/disk0

sudo fdisk /dev/disk0

"sudo" is not required before the commands if you are in Recovery console.

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Answer 9

M Compas Author

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Aug 21, 2015 4:19 PM in response to Loner T

Here's the Terminal output from the recovery partition:

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Answer 10

Loner T

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Aug 21, 2015 4:42 PM in response to M Compas

FYI, when I ran the Terminal command, after the BOOTCAMP partition was unmounted (as mentioned by diskutil's output), the next line of output mentioned something like – and this isn't verbatim – 'POSIX error, file or folder not found'. I double checked Disk Utility and the BOOTCAMP partition wasn't listed. That partition, however, was visible in the Windows installer with no need to format to NTFS (the Format button was greyed out anyway), and was even visible as a boot option during startup when I had to select the Windows USB key. This is probably irrelevant in the grand scheme of things, but I thought I'd just mention this.

When you convert a disk to free space, the POSIX error is expected. You started with a disk0s4, but free space does not have a disk slice anymore. The diskutil command expects to find a new diskslice which will not appear. It is just a cosmetic bug in diskutil when using free space.

The GPT looks clean. The W10 update/install has overwritten part of your Apple firmware in the EFI partition. In Recovery console, can you mount the EFI partition? It may give you an error. If you do not see it, it may have to be done via command line, but let us try DU first.

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Answer 11

M Compas Author

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215 points

Aug 21, 2015 4:56 PM in response to Loner T

I don't see the EFI partition in the left sidebar in Disk Utility, so I guess Terminal it is. It looks like the EFI partition is disk0s1.

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Answer 12

Loner T

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Aug 21, 2015 5:13 PM in response to M Compas

By default, Disk Utility hides EFI and Recovery HD.

You will need to make a mount point directory. It may be tricky in Recovery console. Once you have created one, try the following command.

mount -t msdos /dev/disk0s1 <MountPointDirectory>

You may have to mount root as read-write to create a mount point.

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Answer 13

M Compas Author

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215 points

Aug 21, 2015 5:34 PM in response to Loner T

So, I think I've managed to mount EFI at /Volumes without issue. Permissions for /Volumes are drwxrwxrwt.

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Answer 14

Loner T

Level 9

59,471 points

Aug 21, 2015 6:03 PM in response to M Compas

You have some stuff missing. If you have an external disk which you can erase, please erase it, which will give you a new EFI directory. You will need the EFI and EFI/Apple tree to be put on your internal disk. Do not use EFI from another Mac.

This is from my MBP.

$ mkdir /Volumes/EFI

$ sudo mount -t msdos /dev/disk0s1 /Volumes/EFI

$ df -h

Filesystem Size Used Avail Capacity iused ifree %iused Mounted on

/dev/disk1 118Gi 77Gi 40Gi 66% 20265818 10599392 66% /

devfs 333Ki 333Ki 0Bi 100% 1155 0 100% /dev

/dev/disk0s4 118Gi 48Gi 70Gi 42% 120064 73175528 0% /Volumes/BOOTCAMP

map -hosts 0Bi 0Bi 0Bi 100% 0 0 100% /net

map auto_home 0Bi 0Bi 0Bi 100% 0 0 100% /home

/dev/disk0s1 197Mi 24Mi 173Mi 13% 0 0 100% /Volumes/EFI

$ cd /Volumes/EFI/

MBP13EFI MyName$ ls -l

total 67

-rwxrwxrwx 1 MyName staff 33598 Oct 16 2014 BOOTLOG

drwxrwxrwx 1 MyName staff 512 Aug 19 2014 EFI

MBP13EFI MyName$ ls EFI/

APPLE

MBP13EFI MyName$ ls EFI/APPLE/

CACHES EXTENSIONS FIRMWARE

MBP13EFI MyName$ ls EFI/APPLE/*

EFI/APPLE/CACHES:

CAFEBEEF

EFI/APPLE/EXTENSIONS:

Firmware.scap

EFI/APPLE/FIRMWARE:

MBP91_00D3_B0B_LOCKED.scap

MBP13EFI MyName$ ls -l EFI/APPLE/*

EFI/APPLE/CACHES:

total 1

drwxrwxrwx 1 MyName staff 512 Oct 16 2014 CAFEBEEF

EFI/APPLE/EXTENSIONS:

total 30722

-rwxrwxrwx 1 MyName staff 15729264 Jul 11 09:08 Firmware.scap

EFI/APPLE/FIRMWARE:

total 16514

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

MBP13EFI MyName$ pwd

/Volumes/EFI

MBP13EFI MyName$

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Answer 15

M Compas Author

Level 2

215 points

Aug 21, 2015 7:31 PM in response to Loner T

Whoa... Ok.

So the current drive installed in my Mac Pro is an upgrade SSD and I still have the stock SSD in an external housing on which OS X is installed – EFI, Recovery HD, and Macintosh HD. What you're saying is that I should not copy the EFI directory, or elements from it, from the stock drive ("another Mac" so to speak) to the installed SSD? I'm wondering how I can grab the EFI directory from an erased disk.

(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.)

If I can copy from the stock SSD, my guess would be to create a second mount point, mount the stock SSD EFI from there, and copy onto the installed SSD. If it's relevant, the stock SSD is at /dev/disk8. Ultimately, will I be overwriting my current EFI directory that contains the 'Boot' and 'Windows' folders, or would I be copying the EFI/APPLE folder alongside them?

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