# btrfs-select-super - overwrite primary superblock with a backup copy - man(8) - [phpMan]

[_BTRFS-SELECT-SUPER_(8)](https://www.chedong.com/phpMan.php/man/BTRFS-SELECT-SUPER/8/markdown)                           BTRFS                          [_BTRFS-SELECT-SUPER_(8)](https://www.chedong.com/phpMan.php/man/BTRFS-SELECT-SUPER/8/markdown)

## 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)](https://www.chedong.com/phpMan.php/man/btrfs/8/markdown)_


6.6.3                                       Mar 31, 2024                       [_BTRFS-SELECT-SUPER_(8)](https://www.chedong.com/phpMan.php/man/BTRFS-SELECT-SUPER/8/markdown)