0

Screenshot of GPT

I wanted to create a dualboot setup on my Macbook Pro so that I could run Big Sur along with High Sierra. Hence, I created another partition of size 37 GB (disk0s3) to install Big Sur on that partition. However, after installing Big Sur, I can no longer access the content of the partition that used to have High Sierra (disk0s2). The drive doesn’t show up on the boot menu. When I ran diskutil from Terminal, it shows unknown partition. How can I recover my data from that partition? I had FileVault enabled on that partition.

As suggested by Jean_JD, I ran the following commands using terminal and found the following outcome from diskutil as presented in the screenshot below: enter image description here

Do I need to run additional commands to verify the disk or the partition is accessible right away?

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  • I suggest erasing the whole disk, reinstall High Sierra and recover data from backup. Also a 128GB disk is too small to go messing about with multiple operating systems - so if you want Big Sur install it on an external disk. And there are other questions and answers about FFFF... partitions.
    – Gilby
    Jul 1 '21 at 23:08
  • Do you remember if the High Sierra partition was a apfs or hfs structure?
    – user415185
    Jul 2 '21 at 5:45
  • @Gilby: Unfortunately, I don’t have backup of the files inside the partition containing High Sierra which is why I need to go through these tedious process. Is there a way to rescue the data from that partition?
    – Fahim
    Jul 2 '21 at 8:01
  • @Jean_JD: High Sierra partition was APFS structure
    – Fahim
    Jul 2 '21 at 8:02
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You can try from the terminal in Recovery Mode, modify the ffff partition by apfs structure. The command are :

diskutil umountDisk disk0

then

gpt remove -i 2 disk0

then

diskutil umountDisk disk0

then

gpt add -i 2 -b 409640 -s 164063192 -t 7C3457EF-0000-11AA-AA11-00306543ECAC disk0

then you give the result of

diskutil list

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  • I ran all the commands and found the following outcome from diskutil list
    – Fahim
    Jul 3 '21 at 9:20
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enter image description here

@Jean_JD I ran all the commands and found this outcome from diskutil list.

3
  • Perfect. Can you try boot on High Sierra? You reboot the system pushing the alt key and "Macintosh HD" should be proposed.
    – user415185
    Jul 3 '21 at 9:37
  • @Jean_JD : Yes. Now I can boot into High Sierra. Thanks you so much.
    – Fahim
    Jul 3 '21 at 10:21
  • That's right. :)
    – user415185
    Jul 3 '21 at 10:40

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