Macbook Pro 16 Failed to boot after Big Sur update now I'm unable to mount the disk even in recovery mode On reboot it showed the cannot boot from hard drive ? screen.
I rebooted into recovery mode but it fails to mount the drive. I can see the drive there with the correct details. It says the following:
Could not mount &quot;disk0s2&quot; (com.apple.Diskmanagement.dis enter error -119930868.)
I googled the error but get lots of posts relating to external drives etc. Nothing in any posts I've come across has helped.
When i run FistAid on the drive it get the following:
Repairing Storage System
Performing fsck_apfs -y -x /dev/disk02s2
warning: nx_block_count is 488475719, while device block count
error: object (oid 0x1): o_cksum (0xbd26e8008dccb575) is invalid for object
Checking the container superblock.
Storage system exit code is 8.
Storage system verify or repair failed. :(-69716)

Operation failed.


If i do &quot;disk util apfs list&quot; in terminal i get the following:
Container ERROR -69808
APFS Container reference: disk1
Size (Capacity Ceiling): ERROR -69620
Capacity in use by volumes: ERROR -69620
Capacity not allocated: ERROR -69620
+-&lt; Physical Store disk0s2
  APFS Physical Store Disk: disk0s2
  Size: 1894999998464 B (1.9 TB)

I need some photos and files off the drive so if anyone can help it would be very much appreicated!
The 16 MacBook Pro is Intel based and has the T2 chip. This means all the data is well encrypted and the keys are stored on the T2 and the system will unlock all of the system data in target mode and other pass phrases may also be able to decrypt the data with FileVault enabled.
I would revive the firmware if you can’t use your known passwords to try and transfer (but not run first aid) to a second Mac.

https://support.apple.com/en-om/guide/apple-configurator-2/apdebea5be51/mac

Do not restore - the steps are very similar and the words sound too close for comfort. Restore intentionally deletes and destroys all data.
Revive leaves your data intact. Now, if your data is already gone, you won’t know until after the revive  is done. It’s unlikely revive will make it harder or more expensive to do data recovery, but I would stop immediately with any fsck since that deletes files and restores the system to a previous state to make the filesystem correct. It’s the opposite of what you want to get files backed up.
For that you want these:

https://drivesaversdatarecovery.com/
https://www.prosofteng.com/mac-data-recovery and two external drives, one about 16 GB or larger to install a rescue OS from recovery and a second the same size or bigger than your SSD to copy off files. (If you have or can borrow a second Mac, install this there and boot yours in target disk mode.)

Then once you have the files backed up, use Internet Recovery to try reinstalling macOS on top of your existing data (this also doesn’t intentionally erase the data, just layers a working system on top of whatever system was there). With luck, you’ll get a backup and a working system without having to do an erase install or the full restore operation.