Does Bootcamp still result in a hybrid MBR/GPT situation

bootcampdual-boot

I am running Mojave still (if that matters, but could update to Catalina), and want to dual-boot Windows 10 for the odd occasion when i need to run a program that is windows only.. or debug something.. but crucially don't want to virtualise.

Not being a massively experienced macOS user (only switch this past year), i've read that bootcamp does some funky things with the partition table, resulting in a MBR/GPT hybrid? Is this still the case? Even though Windows 10 has been UEFI for ages now?

I was planning to simply do a UEFI boot from a USB drive with Windows 10 it, and go from there… will i struggle with drivers without Bootcamp, and is that partition still going to be available in something like parallels though?

Thanks in advance!

Best Answer

Based on the information in your question, Windows 10 UEFI boots on your model Mac. Most users use the Boot Camp Assistant to install Windows 10. You do not have to use the Boot Camp Assistant, however the easiest way to download the Windows Support Software (the drivers) is to use the Boot Camp Assistant. Once you have the Windows Support Software, you can install using a flash drive if you wish.

You can use the Boot Camp Assistant to download the Windows Support Software without actually creating a partition and installing Windows.

You will not need hybrid partitioning to run Windows 10 on your Mac. This is true whether or not you use the Boot Camp Assistant to install.

Related Solutions

Windows – Fixing a Windows partition boot using OS X tools

I'll post this as an answer, even though it didn't fix my problem – this was a lost case in the end. Aftermath: I dd'ed a backup of the Windows partition to my OS X partition:

sudo dd bs=512 if=/dev/disk0 of=windows_backup skip=732993496 count=173955112

Now I had a 80 gig hex dump which I could examine safely. I used a hex editor to search for all kinds of metadata:

"NTFS" (encoded in ASCII) which starts a NTFS volume.
"FILE" (encoded in ASCII) which starts a file entry record in the $MFT or master file table in NTFS.
NTFS system file names (like "MFT", tried with little-endian UTF-16 and ASCII)

... and so on. But without success. I was able to find all kinds of data from the dump, but all the metadata, including the boot record (the first sector of the volume), the $Boot file (the first 15 sectors after the boot record), the $MFT file which keeps record of all the files on the file system, were gone.

The thing that baffles me that I couldn't even find $MFTMirr file, which is the backup file of the metadata files and stored halfway of the volume.

I was able to find a backup of the boot sector from its standard location, the last sector of the volume. However, the data was old, from the era before resizing the volume. The boot sector has stored the offset of the $MFT file metadata file, but inspecting the references was moot, there was nothing of value there.

In the end, I concluded that the volume was totally borked. The moral of the story? Hybrid Master Boot Record is evil. Also, it seems that the program that resized the volume did a subpar job, failing to update some of the metadata.

MacOS – Partition sharing – messed up with GPT/MBR

FIX WITH ACCESS TO SHARED PARTITION

To get Windows to boot, you can try entering the following in gdisk from OS X. Before entering the command, you will have to disable System Integrity Protection (SIP). If Windows boots, you will be able to access the new shared partition from Windows. If Windows does not boot, follow the instructions in the section titled "FIX WITHOUT ACCESS TO SHARED PARTITION".

Steelhead:~ davidanderson$ gdisk /dev/disk0
GPT fdisk (gdisk) version 1.0.1

Warning: Devices opened with shared lock will not have their
partition table automatically reloaded!
Partition table scan:
  MBR: hybrid
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with hybrid MBR; using GPT.

Command (? for help): r

Recovery/transformation command (? for help): h

WARNING! Hybrid MBRs are flaky and dangerous! If you decide not to use one,
just hit the Enter key at the below prompt and your MBR partition table will
be untouched.

Type from one to three GPT partition numbers, separated by spaces, to be
added to the hybrid MBR, in sequence: 2 4 5
Place EFI GPT (0xEE) partition first in MBR (good for GRUB)? (Y/N): y

Creating entry for GPT partition #2 (MBR partition #2)
Enter an MBR hex code (default AF): af
Set the bootable flag? (Y/N): n

Creating entry for GPT partition #4 (MBR partition #3)
Enter an MBR hex code (default 07): 0b
Set the bootable flag? (Y/N): n

Creating entry for GPT partition #5 (MBR partition #4)
Enter an MBR hex code (default 07): 07
Set the bootable flag? (Y/N): y

Recovery/transformation command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): y
OK; writing new GUID partition table (GPT) to /dev/disk1.
Warning: Devices opened with shared lock will not have their
partition table automatically reloaded!
Warning: The kernel may continue to use old or deleted partitions.
You should reboot or remove the drive.
The operation has completed successfully.
Steelhead:~ davidanderson$

FIX WITHOUT ACCESS TO SHARED PARTITION

Steelhead:~ davidanderson$ gdisk /dev/disk0
GPT fdisk (gdisk) version 1.0.1

Warning: Devices opened with shared lock will not have their
partition table automatically reloaded!
Partition table scan:
  MBR: hybrid
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with hybrid MBR; using GPT.

Command (? for help): r

Recovery/transformation command (? for help): h

WARNING! Hybrid MBRs are flaky and dangerous! If you decide not to use one,
just hit the Enter key at the below prompt and your MBR partition table will
be untouched.

Type from one to three GPT partition numbers, separated by spaces, to be
added to the hybrid MBR, in sequence: 2 3 5
Place EFI GPT (0xEE) partition first in MBR (good for GRUB)? (Y/N): y

Creating entry for GPT partition #2 (MBR partition #2)
Enter an MBR hex code (default AF): af
Set the bootable flag? (Y/N): n

Creating entry for GPT partition #3 (MBR partition #3)
Enter an MBR hex code (default AB): ab
Set the bootable flag? (Y/N): n

Creating entry for GPT partition #5 (MBR partition #4)
Enter an MBR hex code (default 07): 07
Set the bootable flag? (Y/N): y

Recovery/transformation command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): y
OK; writing new GUID partition table (GPT) to /dev/disk1.
Warning: Devices opened with shared lock will not have their
partition table automatically reloaded!
Warning: The kernel may continue to use old or deleted partitions.
You should reboot or remove the drive.
The operation has completed successfully.
Steelhead:~ davidanderson$