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Re: How to make btrfs forget a disk?



David wrote:
> On Fri, 12 Mar 2021 at 20:17, Victor Sudakov <vas@sibptus.ru> wrote:
> > deloptes wrote:
> 
> > > > "wipefs -t btrfs -f -a /dev/nvme1n1" did the job.
> 
> > > > Still wondering where those labels are stored on disk in Linux.
> 
> > > FS Superblock?
> 
> > Well, the FS (btrfs in this case) was not there already, but the magic
> > label was still there somewhere.
> 
> My new knowledge after 5 seconds of searching, ...
> 
> https://en.wikipedia.org/wiki/Btrfs#Superblock
> says that there are multiple copies of the superblock.

Many filesystems have multiple copies of the superblock (e.g. UFS and ext*).

What surprised and worried me is the fact that they persisted after the
disk was converted to ZFS, and btrfs continued to recognize this
filesystem as its own (albeit unmounted).

> 
> And the on-disk format is here:
>   https://btrfs.wiki.kernel.org/index.php/On-disk_Format

> 
> And maybe if the drive was once part of a multiple
> device filesystem it might be referenced in superblocks
> on other devices.
> 

No, it was not.

-- 
Victor Sudakov VAS4-RIPE
http://vas.tomsk.ru/
2:5005/49@fidonet

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