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

       This page is part of the btrfs-progs (btrfs filesystem tools)
       project.  Information about the project can be found at 
       If you have a bug report for this manual page, see 
       This page was obtained from the project's upstream Git repository 
       on 2017-09-15.  If you discover any rendering problems in this HTML
       version of the page, or you believe there is a better or more up-to-
       date source for the page, or you have corrections or improvements to
       the information in this COLOPHON (which is not part of the original
       manual page), send a mail to

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