Why fdisk can't open root disk with MBR for writing?

[Benjamin Kaduk]

On Sat, 15 Sep 2012, Julian H. Stacey wrote:

> I have been applying this diff to my man fdisk:
>
> http://berklix.com/~jhs/src/bsd/fixes/FreeBSD/src/gen/sbin/fdisk/
>
> *** 8.0-RELEASE/src/sbin/fdisk/fdisk.8	Sat Mar 14 22:32:16 2009
> --- new-generic/src/sbin/fdisk/fdisk.8	Sat Mar 14 22:35:10 2009
> ***************
> *** 462,464 ****
> --- 462,468 ----
>  The
>  .Xr bsdlabel 8
>  command must be used for this.
> + .Pp
> + When running multi user, you cannot write unless you first run this:
> + .br
> + sysctl kern.geom.debugflags=16
>
> I never submitted it as a send-pr,
> anyone think I should submit it to help save people ?

We have had a long discussion about kern.geom.debugflags starting here:
http://lists.freebsd.org/pipermail/freebsd-current/2011-October/028090.html
My understanding from that discussion is that your patch should not be 
accepted.

-Ben Kaduk