this post was submitted on 19 Apr 2024
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systemdeez nuts (sh.itjust.works)
submitted 7 months ago by [email protected] to c/[email protected]
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[–] [email protected] 3 points 7 months ago (1 children)

btrfs data rescue after I deleted a parent snapshot of my rollback

Can you expand a bit on that? I thought it didn't matter if you deleted parent snapshots because the extents required by the child would still be there.

[–] [email protected] 1 points 7 months ago* (last edited 7 months ago) (1 children)

Honestly, I have no idea why it went wrong or why it let me do that. Also my memory is a bit fuzzy since it's been a while, but as best I can remember what I did step by step:

  1. fuck around with power management configs
  2. using btrfs-assistant gui app, rolled back to before that
  3. btrfs-assistant created an additional snapshot, called backup something, I didn't really pay attention
  4. reboot, all seemed good
  5. used btrfs-list to take a look, the subvolume that was the current root / was a child of the aformentioned backup subvolume
  6. started btrfs-assistant and deleted the backup subvolume
  7. system suddenly read only
  8. reboot, still read only
  9. btrfs check said broken refs and some other errors,
  10. i tried to let btrfs check fix the errors, which made it worse, now I couldn't even mount the drive anymore because btrfs was completely borked
  11. used btrfs rescue, which got all files out onto an external drive successfully
  12. installed arch again and rsync the rescued files over the new install, everything works as before, all files are there
[–] [email protected] 2 points 7 months ago

btrfs check said broken refs and some other errors,

Gotcha. That must have been a kernel bug (or hardware error), none of the userspace utilities could cause it unless they were trying to manipulate the block device directly, which would be really dumb. It's possible it wasn't even related to the subvolume manipulation.