btrfs-progs/Documentation/btrfs-select-super.rst

btrfs-select-super(8)
=====================

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, 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.

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

SEE ALSO
--------

btrfs(8)
btrfs-progs: docs: add sample RSTified manual page The asciidoc format needs to be tweaked but otherwise is basically the same. Changes: - bold text is - italics is * * - NOTE is directive .. note - definition list is simple indented block after the term - section NAME in the manual page is generated from date in conf.py:man_pages - new page has to be added to the index To do: - references to other manual pages, will be RST native linking once all the pages are converted The output is in Documentation/_build/man and the format is visually not much different from what is generated by asciidoc. Signed-off-by: David Sterba <dsterba@suse.com> 2021-10-27 05:06:50 +08:00			`btrfs-select-super(8)`
			`=====================`

			`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, 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.`

			`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`

			`SEE ALSO`
			`--------`

			`btrfs(8)`