Re: dd and mbr

On Tue, Jan 11, 2022 at 11:05 AM Roderick wrote:
> The command:
> dd if=/dev/zero of=/dev/da0
> does not delete the mbr, I still see the partition table with
> fdisk. My questions:
> (1) What does this command do?
> (2) How to delete the mbr with dd? How to address the whole disk with dd?
> In OpenBSD is simply
> dd if=/dev/zero of=/dev/rsd0c
> with perhaps a count argument.
> Rod.

There seems to be a tricky sysctl introduced some time ago that
prevents some operations on mbr.. I got into that issuse some time ago
but don't remember details sorry..

I also do not like that FreeBSD system hides something from me like
Linux then requires searching for a magic solution.. I would prefer to
stay OpenBSD way you presented :-(

Check for mbr related warnings in dmesg.

Try:
sysctl kern.geom.debugflags=16
sysctl kern.geom.part.check_integrity=0

Hope that helps / hints the direction :-)

-- 
CeDeROM, SQ7MHZ, http://www.tomek.cedro.info