fdisk incompatibility between major versions

[Dimitry Andric]

On 2009-05-25 19:36, Freddie Cash wrote:
>>   So ... I'm guessing the problem in the boot code is corrupted, and if I do
>>
>>    fdisk -B -b <path to -CURRENT boot blocks> da0
>>
>>    it should put things back to normal.
>>    However: when I do the second commit I get
>>
>>    fdisk: Geom not found "da0"
>>    fdsk: failed to write sector 0
> 
> In order to alter a drive with a mounted filesystem (ie an active
> drive), you need to first set the drive to writable:
> 
> sysctl -w kern.geom.debugflags=16

If the original poster is running from a Fixit CD, he could also simply
unmount the filesystem before zapping its boot blocks from under it. :)

Normally you only need to enable the footshooting^Wdebugflags stuff
when you are doing this from the booted system itself, instead of a
Fixit or LiveFS disc.