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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?

Fahim
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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 01 '21 at 23:08
  • Do you remember if the High Sierra partition was a apfs or hfs structure? –  Jul 02 '21 at 05:45
  • @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 02 '21 at 08:01
  • @Jean_JD: High Sierra partition was APFS structure – Fahim Jul 02 '21 at 08:02

2 Answers2

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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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enter image description here

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

Fahim
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