homelab/stories/data_recovery.md

Data Recovery

Lost btrfs filesystem

1. BTRFS expects its header (_BHRfS_M) to be 64KiB offset from the start of the disk

# Find the byte position of _BHRfS_M
# Convert this to dec before using the number
hexdump -C borg.raw | less

# Create a loop device starting at that position
# Device will be created at /dev/loopX
# -f finds the first available number to use
# -P scans the partition table
# -b is sector size
# --offset 8388672 sets the offset if there are partitions ahead of the one you're after
# use the byte offset above
losetup -fP -b 4096 borg.raw

# List loop devices
losetup -l

# Mount the partition
mount /dev/loop0p1 /mnt/restore

# Delete the loop device when done
losetup -d /dev/loopX