Re: Btrfs: wipe all the superblock [redhat bugzilla 889888]

[Goffredo Baroncelli <kreijack@tiscalinet.it>]

Hi Karel,

On 01/08/2013 07:01 PM, Karel Zak wrote:
> On Sun, Jan 06, 2013 at 07:28:55PM +0100, Goffredo Baroncelli wrote:
>> If the first superblock is valid except that the "magic field" is zeroed,
>> btrfs skips the check of the other superblocks.
>> If the first superblock is fully invalid, btrfs checks for the other
>> superblock.
> 
>  Hmm... why inconsistent (or missing) superblock is not reported as a
>  problem? If I good understand the filesystem is still mountable,
>  right?

It should, however my tests were unsuccessful :-(... Chris ?


> 
>> So zeroing the first superblock "magic field" at the beginning seems
>> that the filesystem is wiped.
> 
>  Well, this is exactly the idea behind wipefs(8), just wipe minimal
>  number of bytes from the device to make the filesystem invisible for
>  libblkid (udev, ...). This concept is relatively safe, if you make a
>  mistake than you can restore the magic string, your data should not
>  be affected by wipefs(8).

I fully agree. However wipefs should zero all three superblock

> 
>     Karel
> 


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