svn commit: r292058 - head/sbin/geom/class/part

[Alexey Dokuchaev]

On Thu, Dec 10, 2015 at 08:42:01PM +0300, Andrey V. Elsukov wrote:
> On 10.12.15 20:05, Ian Lepore wrote:
> > On Thu, 2015-12-10 at 10:37 +0000, Andrey V. Elsukov wrote:
> >> Author: ae
> >> Date: Thu Dec 10 10:37:12 2015
> >> New Revision: 292058
> >> URL: https://svnweb.freebsd.org/changeset/base/292058
> >>
> >> Log:
> >>   Remove a note about damaged PMBR. Now GPT will be detected
> >> automatically
> >>   with such corruption.
> >>   
> >>   MFC after:	1 month
> > 
> > Will all of these changes add up to it being impossible to make a
> > device NOT be recognized as gpt once it has had gpt on it?
> > It's typical to dd some zeroes to the start of a volume to clean out
> > old info, but if geom is going to aggressively ressurect a purposely
> > -nuked GPT based on the backup info (which is hard to find and dd over
> > by hand) this is going to add up to a lot of frustration for those of
> > us who have to frequently work with regenerating sdcard and CF images.

+1, I'm also used to "dd'ing zeros" trick.
 
> If you want to make device to not be recognized as GPT, you should use
> 'gpart destroy -F <device>' this will destroy first two sectors where
> PMBR and primary GPT header are located, also it will destroy the last
> sector with backup GPT.

While this' technically more accurate, "geom destroy" never worked for me
without googling or reading the manpage because of missing -F switch, I
think.  Filling first few sectors with zeros worked for so many years and
people got used to that.  Would it perhaps make sense to add debug message
when backup GPT is being used?

./danfe