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

NAME         top

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

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

       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
       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:

       ·   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 v4.6.1                     07/16/2016            BTRFS-SELECT-SUPER(8)