man > btrfs-select-super(8)

BTRFS-SELECT-SUPER(8)                           BTRFS                          BTRFS-SELECT-SUPER(8)

NAME
       btrfs-select-super - overwrite primary superblock with a backup copy

SYNOPSIS
       btrfs-select-super -s number <device>

DESCRIPTION
       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 speci‐
       fies the superblock copy to use.

       Superblock copies exist in the following offsets on the device:

       • primary: 64KiB (65536)

       • 1st copy: 64MiB (67108864)

       • 2nd copy: 256GiB (274877906944)

       A superblock size is 4KiB (4096).

OPTIONS
       -s|--super <N>
              use Nth superblock copy, valid values are 0 1 or 2 if the respective superblock offset
              is within the device size

SEE ALSO
       btrfs(8)


6.6.3                                       Mar 31, 2024                       BTRFS-SELECT-SUPER(8)