filesystem show still has stale filesystem

filesystem show still has stale filesystem

[Florian Lindner]

Hello,

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

Btrfs Btrfs v0.19

Label home is the actual partition in use but how can I get rid of
label test which was the accidental formatting? Is this just some
cached value or still persistent on the disk?

Thanks,

Florian

Re: filesystem show still has stale filesystem

[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

Re: filesystem show still has stale filesystem

[Martin Steigerwald]

Am Sonntag, 5. August 2012 schrieb Florian Lindner:
> Hello,

Hi Florian,

> 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

wipefs shows and removes filesystem signatures. No need to dd.

Ciao,
-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7

Re: filesystem show still has stale filesystem

[Martin Steigerwald]

Am Sonntag, 5. August 2012 schrieb Florian Lindner:
> Hello,

Hi Florian,

> 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

wipefs shows and removes filesystem signatures. No need to dd.

Ciao,
-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7