1BTRFS-SELECT-SUPER(8)                BTRFS               BTRFS-SELECT-SUPER(8)
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NAME

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

9       btrfs-select-super -s number <device>
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DESCRIPTION

12       Destructively  overwrite  all copies of the superblock with a specified
13       copy.  This helps in certain cases, for  example  when  write  barriers
14       were disabled during a power failure and not all superblocks were writ‐
15       ten, or if the primary superblock is damaged,  eg.  accidentally  over‐
16       written.
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18       The filesystem specified by device must not be mounted.
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20       NOTE:
21          Prior  to  overwriting the primary superblock, please make sure that
22          the backup copies are valid!
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24       To dump a superblock use the btrfs inspect-internal dump-super command.
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26       Then run the check (in the non-repair mode)  using  the  command  btrfs
27       check -s where -s specifies the superblock copy to use.
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29       Superblock copies exist in the following offsets on the device:
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31       • primary: 64KiB (65536)
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33       • 1st copy: 64MiB (67108864)
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35       • 2nd copy: 256GiB (274877906944)
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37       A superblock size is 4KiB (4096).
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OPTIONS

40       -s|--super <N>
41              use  Nth  superblock  copy, valid values are 0 1 or 2 if the re‐
42              spective superblock offset is within the device size
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SEE ALSO

45       btrfs(8)
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48       2022
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535.18                             May 25, 2022            BTRFS-SELECT-SUPER(8)
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