btrfs-select-super

BTRFS-SELECT-SUPER(8) BTRFS 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 dur‐
   ing 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 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

   -s|--super <N>
          use Nth superblock copy, valid values are 0 1 or 2 if the respective superblock offset is within the device size