Simple way to clear arbitrary drive metadata?

[Xin Li]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

On 09/28/12 15:21, Warren Block wrote:
> Last night, I found that the remnants of a GPT backup table on an
> MBR drive prevented it from booting.  When reusing drives from old
> mirrors, old mirror metadata can be a problem also.  And there may
> be old hardware RAID metadata at the end of the drive.
> 
> It would be great if dd understood negative seek values.  This
> would get most of that old metadata:
> 
> dd if=/dev/zero of=/dev/ada8 seek=-34
> 
> ...but dd does not understand negative seek values.  (Been on my
> list for a while to look at that.)
> 
> Which leaves things like
> 
> diskinfo ada8 | cut -f4 (subtract 34) dd if=/dev/zero of=/dev/ada8
> seek=(calculated value)
> 
> That can be done in one command line with bc and backticks, but
> it's not clear or elegant.  gpart can clear secondary GPT tables,
> but I'm pretty sure it won't wipe out that space unless it actually
> is a GPT table. Likewise with glabel and gmirror, they're safe
> because they only touch data they understand.
> 
> Is there something simpler and more blunt?

I think you can do:

gpart destroy -F ada8
gpart create -s gpt ada8
gpart destroy -F ada8

The second 'create' will write an empty partition table to the
secondary table.

Cheers,
- -- 
Xin LI <delphij at delphij.net>    https://www.delphij.net/
FreeBSD - The Power to Serve!           Live free or die
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.19 (FreeBSD)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iQEcBAEBCAAGBQJQZjhmAAoJEG80Jeu8UPuzp/wIAJ9TQdwRIvfMn5zP3yMqYKIV
OvVNSUaecPaav9G7CEwApl1bQnmCSYepv6FASH65CoNyr14kioS0e8BET4s/GzQD
LhliFucVnd6X6POdyL5VEdJ78UYuox8h9elykJBSlwdgeWGCpoRwI9sG8+oWtl+Z
zpYKgUBU+eCTsXWjIBbLGphhgXgDT+j1uEks8qxbVsUNZH054tKWEQ6iK2+bKGYa
6dp3M+Lrt6qJLcKWtFvxMVP2rzCzYmRmSFkKVUiIHgSOp2yH4uFvzRo9CY74azuL
QS4/+h5iuMtnMiXKr5sWoGOi4WCTLVSnmo07ac9aP4H0jlTuVmJ/Qq/hoqOuMZg=
=ae1M
-----END PGP SIGNATURE-----