partitioning disk error

Rebuild MBR to match the new GPT information thus resetting the Hybrid MBR. Use defaults for other questions (like partition codes). The only values that need modifications are the Boot flags and step 10. Accept all other defaults that Gdisk offers. Please see thesample Q&A as an example. These steps can be repeated if you make a mistake before you get to Step 12, otherwise start from Step 1 for these steps. Step 6 has numbers which are typed with a space between the numbers. Please see the sample Q&A before you execute these steps.

1. Sudo gdisk /dev/rdisk0
2. P (Print list of parts)
3. R (Recover)
4. O (print current Hybrid MBR)
5. H (chooses Hybrid)
6. Partitions numbers to be hybridized: 2 3
7. Y (Good for GRUB question)
8. N (part 2 boot flag)
9. Y (part 3 boot flag make NTFS bootable partition)
10. O (print current Hybrid MBR)
11. W (Write the new MBR)
12. Y (Yes! write the new MBR)
13. Reboot

Here is sample Q&A for this section. Please notice the Press Enter/Return.

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): Press Enter/Return

Set the bootable flag? (Y/N): N

Creating entry for GPT partition #3 (MBR partition #3)

Enter an MBR hex code (default 07): Press Enter/Return

Set the bootable flag? (Y/N): Y

Post the output of

sudo gpt -vv -r show /dev/disk0

sudo fdisk /dev/disk0

for validation.

You have 8 local snapshots. These need to be trimmed. Run

sudo tmutil thinlocalsnapshots / 999999999999

Notice the spaces between each word, including the "/".

Run

sudo tmutil deletelocalsnapshots 2020-03-20-172114

and repeat for the remaining entries. Verify that you do not have any using

sudo tmutil listlocalsnapshots /

and retry BC Assistant.

Disconnect all external peripherals, run SMC and NVRAM Reset, connect only the USB Installer, reboot and hold Alt/Option and check available selections.

• Do you see a Windows icon from the USB? If yes, can you select it?
• Does the Windows installer start and show you available partitions? If yes, can you select the partition you created?
• Can you format and start the Windows installation?

Please re-enable SIP using csrutil Local Recovery.

What is the exact version of macOS? Also, as a test, can you create a FAT (or exFAT) partition of the size you want Windows to be?

• Good to see the Test partition.
• You should not have disk3/disk4.
• You will need a larger USB flash drive, preferably 16+GB. This will accommodate the larger Windows ISOs.

This is a correctable error. Select macOS and let the Mac boot normally. We can then correct the GPT vs MBR issue.

You will need to temporarily disable SIP using csrutil when booted in Local Recovery.

Can you post the output of

sudo fsck_apfs -n -l /dev/rdisk1

Can you post the output of

diskutil list

This command may hang.

Assuming you are booted in Local Recovery, run

csrutil status

csrutil disable

csrutil status

and post the output.

Since you have a 2012 Mac, you should have three options in BC Assistant - Create, Download and Install.

Using Create+Download will let you build an installer. Install will partition the disk and install Windows. Are you able to build a USB Installer using Create+Download?

Are you able to start a Terminal window?

Can you post the output of

diskutil list