boot0 and fdisk / disklabel misbehaviour

Bruce Evans bde at
Tue Nov 11 08:32:40 PST 2003

On Tue, 11 Nov 2003, Dag-Erling [iso-8859-1] Sm=F8rgrav wrote:

> I've been busy installing various OSes on a spare disk in order to try
> to reproduce some of fefe's benchmarks.  In the process, I've noticed
> a couple of bogons in boot0 and disklabel:
>  - disklabel -B trashes the partition table:
>    # dd if=3D/dev/zero of=3D/dev/ad0 count=3D20
>    # fdisk -i ad0
>    (create a FreeBSD partition)
>    # disklabel -rw ad0s1 auto
>    # newfs -U /dev/ad0s1a
>    # disklabel -B ad0s1a
>    (this trashes the partition table)

I think you mean bsdlabel.  disklabel is just a link to bsdlabel in

This was fixed in rev.1.8 of disklabel.c, but the change was lost in

>    This probably happens because fdisk silently allows the user to
>    create a partition that overlaps the partition table.  Arguably
>    pilot error, but very confusing at the time, and fdisk should warn
>    about it.

Yes.  This is the dangerously undedicated case.  Some consider this to
be an error.  I only ever used it for one drive.


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