btrfs-select-super − overwrite primary superblock with a backup copy
btrfs−select−super −s number <device>
Destructively overwrite all copies of the superblock with a specified copy. This helps in certain cases, for example when write barriers were disabled during a power failure and not all superblocks were written, or if the primary superblock is damaged, e.g. accidentally overwritten.
The filesystem specified by device must not be mounted.
NOTE:
Prior to overwriting the primary superblock, please make sure that the backup copies are valid!
To dump a superblock use the btrfs inspect−internal dump−super command.
Then run the check (in the non−repair mode) using the command btrfs check −s where −s specifies the superblock copy to use.
Superblock copies exist in the following offsets on the device:
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primary: 64KiB (65536) |
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1st copy: 64MiB (67108864) |
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2nd copy: 256GiB (274877906944) |
A superblock size is 4KiB (4096).
−s|−−super <N>
use Nth superblock copy, valid values are 0 1 or 2 if the respective superblock offset is within the device size
btrfs(8)