Re: filesystem show still has stale filesystem

[Hullen@t-online.de (Helmut Hullen)]

Hallo, Florian,

Du meintest am 05.08.12:

> I was playing with btrfs and accidentally formatted the disk directly
> (/dev/sdb instead of sdb1). Since then I rewrote the GPT partition
> table, recreated the partition and ran btrfs device scan. Still,
> btrfs filesystem show prints:

> root@horus /mnt # btrfs fi sh --all-devices
> failed to read /dev/sr0: No medium found
> Label: 'test'  uuid: ffab72f2-eff1-4ac8-a694-d56dd84fda24
>         Total devices 1 FS bytes used 28.00KB
>         devid    1 size 2.73TB used 2.04GB path /dev/sdb

> Label: 'home'  uuid: c465d715-098a-4d0d-bebc-6aa51f4cb349
>         Total devices 1 FS bytes used 28.00KB
>         devid    1 size 2.73TB used 2.04GB path /dev/sdb1

"formatting" leaves most bytes on the disk untouched. If you really want  
to use only /dev/sdb (or only /dev/sdb1) then you should first fill many  
bytes at the beginning of the disk with zeros.

Some months ago someone had told the minimum; I have forgotten this  
value. But something like

        dd if=/dev/zero of=/dev/sdb bs=1M count=10

should do the job.

And then "mkfs.btrfs" creates the (only) wanted partition(s).

Viele Gruesse!
Helmut