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

[Garrett Cooper]

On Sat, Sep 15, 2012 at 11:49 AM, Benjamin Kaduk <kaduk at mit.edu> wrote:
> 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.

    Correct. Either fdisk should be fixed or updated to point out that
gpart should be used. There is some useful utility for fdisk still,
but it's waning.
Thanks,
-Garrett