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
       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, 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 
       ⟨https://btrfs.wiki.kernel.org/index.php/Btrfs_source_repositories⟩.
       If you have a bug report for this manual page, see
       ⟨https://btrfs.wiki.kernel.org/index.php/Problem_FAQ#How_do_I_report_bugs_and_issues.3F⟩.
       This page was obtained from the project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git⟩
       on 2018-02-02.  (At that time, the date of the most recent commit
       that was found in the repository was 2018-01-05.)  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 man-pages@man7.org

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

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