btrfs-select-super(8) — Linux manual page


BTRFS-SELECT-SUPER(8)         Btrfs Manual         BTRFS-SELECT-SUPER(8)

NAME         top

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

SYNOPSIS         top

       btrfs-select-super -s number <device>

DESCRIPTION         top

       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.


           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

       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:

       •   primary: 64KiB (65536)

       •   1st copy: 64MiB (67108864)

       •   2nd copy: 256GiB (274877906944)

       A superblock size is 4KiB (4096).

OPTIONS         top

       -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         top

       btrfs-inspect-internal(8), btrfsck check(8)

COLOPHON         top

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Btrfs v5.16.1                  02/06/2022          BTRFS-SELECT-SUPER(8)