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.
NotePrior to overwriting the primary superblock, please make surethat 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).
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project. Information about the project can be found at
If you have a bug report for this manual page, see
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Btrfs v4.6.1 05/16/2020 BTRFS-SELECT-SUPER(8)