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BTRFS-SELECT-SUPER(8)            Btrfs Manual            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, eg. 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,
       or the obsolete command btrfs-show-super.
       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:
       o   primary: 64KiB (65536)
       o   1st copy: 64MiB (67108864)
       o   2nd copy: 256GiB (274877906944)
       A superblock size is 4KiB (4096).
OPTIONS
       -s|--super <superblock>
           use 'superblock'th superblock copy, valid values are 0 1 or 2 if
           the respective superblock offset is within the device size
SEE ALSO
       btrfs-inspect-internal(8), btrfsck check(8)

Btrfs v4.9.1                      08/06/2017             BTRFS-SELECT-SUPER(8)