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When pressing the option during startup, MacOS isn’t shown as an option to boot into.

Using the tray in win10 to “Restart in MacOS” also doesn’t work. It just restarts back into Windows 10.

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It is an iMac 27" 5K 2017 model, running macOS 12.1. And in the windows side, it is running Windows 10 Pro Version 21H2.

Below is a screenshot showing how the disk is partitioned from within Windows.

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Below is output showing the internal drives after running diskutil list in macOS Internet Recovery.

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A more complete screenshot can be found here.

I followed the steps posted. It seems it was disk1 this time so I used disk1 in when executing the commands.

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Reinstalling also doesn’t show the mac drive (about 800gb), so I am currently unable to reinstall as well.

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This is the disk utility showing the drives. Below shows what I believe to be the macOS drive, which is currently unmounted so I am unable to boot into macOS or even select the drive for reinstalling macOS.

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And here below is the startup disk selection.

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  • Can you add a screenshot showing how the disk is partitioned (from within Windows)?
    – nohillside
    Mar 22 at 13:56
  • Do you know the model year of the Mac? Do you know which version of Windows and macOS is installed? Can you boot to macOS Internet Recovery and post the output from the command diskutil list? Mar 22 at 19:37
  • Hi @nohillside imgur.com/a/bhotMuq I'm sorry I wasn't sure how uploading a picture worked.
    – Ryan
    Mar 23 at 8:27
  • Hello @DavidAnderson! It's an iMac 27" 5K 2017 model, running macOS 12.1. And in the windows side, it is running Windows 10 Pro Version 21H2.
    – Ryan
    Mar 23 at 8:28
  • Here is the list from Internet Recovery imgur.com/a/i3FQUuY
    – Ryan
    Mar 23 at 9:10

1 Answer 1

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One possability is the ID for the first partition in the MBR table on disk2 was changed from EE to 06. Here, I assume disk2 is the SSD part of an internal Fusion drive arrangement.

You could make the following entries to change the ID to EE. You will need to boot to macOS Internet Recovery.

Note: Before making the entries given below, you should first enter the command diskutil list internal, then check to see if disk2 is still the identifier of the same drive shown in your posted images.

fdisk -e /dev/disk2
s 1
ee
w
q

Afterwards, post the output from the commands below.

fdisk /dev/disk2
gpt -r show /dev/disk2
diskutil list internal

You many need to make more entries after posting the output.

Update 1

Based on the output posted after changing the ID to ee, I can see you do not a valid GUID Partition Table (GPT) stored in internal SSD (disk2). Your model Mac is suppose to have a Fusion drive arrangement, where there would be an APFS container consisting of an APFS partition from the internal HDD and an APFS partition from the internal SSD. Since the firmware can only find an APFS partition on the internal HDD, none of the APFS volumes can be mounted and thus macOS can not boot. If you have a backup on needed files, you would probably be better off reinstalling macOS and Windows.

Update 2

Before attempting to reinstall macOS, you will need to rebuild a Fusion container. Below are the commands to enter.

Note: Before making the entries given below, you should first enter the command diskutil list internal, then check to see if disk0 and disk2 are still the identifiers of the same drives shown in your posted images. For instance, disk0 should be 1.0 TB in size and disk2 should be 28.0 GB in size.

diskutil apfs deleteContainer -force disk0s2 Temp1
diskutil erasedisk jhfs+ Temp2 gpt disk2
diskutil apfs create disk2s2 disk0s2 "Macintosh HD"

If you successfully reinstall macOS, then post a comment and I will add steps to remove the OSXRESERVED volume and add the free space to the APFS container.

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  • Hello @david thanks for the reply.
    – Ryan
    Apr 6 at 7:40
  • I was wondering if I will lose my data if I go forward with the steps mentioned in Update 2
    – Ryan
    Apr 6 at 7:41
  • You will lose any data in the macOS volume. The Boot Camp volume should remain unchanged. Still, to be safe, you should always have a backup of important data. Apr 6 at 9:11
  • Hello Is there any way to make a backup? Since the drive appears to be “unmounted”
    – Ryan
    Apr 15 at 14:38
  • I do not know of any way you could mount the APFS volumes where macOS was stored. Apr 15 at 15:54

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