MBR not overwritable with dd?

[Emanuel Strobl]

Am Montag, 11. Oktober 2004 04:37 schrieb Jerry McAllister:
> > I tried to null out the MBR with the BETA7 fixit CD with the follwoing=20
> > command:
> > dd if=3D/dev/zero of=3D/dev/ad0 count=3D16
> >
> > After that fdsik still showed me a valid partition tabel!
> > How? Does GEOM map the beginning of the raw device?
>
> Was it getting it from the in-memory informatino?

After a lowlevel format fdisk still showed me a partition in slice 1 with id 
165. So fdisk is misbehaving here. A hexdump of the first 512 Bytes validated 
that fdisk is wrong.

Another question is why does sysinstall complain about wrong geometry? It 
claims the CHS values, but why? I heard that it's the fault of "other OSes" 
becaus they're writing wrong info onto the disk. But this disk has nothing 
but NULLs on it and sysinstall is presenting CHS values, also fdisk reads CHS 
Values "from in-core labels". Can anybody entlighten me what in-core labels 
are?

Then there's another error in sysinstall but I'll post that on current (when 
creating two slices, the partition table ends up in having two active 
entries)

Thanks,

-Harry

>
> ////jerry
>
> > Thank you in advance,
>
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