kern.geom.debugflags=16 does NOT allow me to write to device

[Ivan Voras]

On 04/23/10 14:44, John Baldwin wrote:
> On Friday 23 April 2010 8:25:51 am Andriy Gapon wrote:
>> on 23/04/2010 13:34 Peter Schuller said the following:
>>>> It's easy.
>>>
>>> Thank you for posting the example. I never really understood that
>>> gpart was to be the generic tool; I thought it was gpt specific.
>>> Obviously I should have read up better.
>>>
>>> Is gpart to be considered "tested", "stable", "production quality"
>>> and/or "default" now then, or is it still cutting edge/experimental?
>>
>> Yes, it's "tested", "stable", "production quality" and/or "default".
>> All other tools are slowly rotting now, but can be fixed to correctly works via
>> GEOM interface the same way gpart does now.
>> E.g. see Andrey's work on sade(8).
>
> Actually, the other tools were already fixed to work properly with GEOM, but
> they used the older set of GEOM classes (GEOM_BSD, GEOM_MBR, etc.) instead
> of the GEOM_PART classes.

It also depends on the meaning of "fixed" :) They mostly wrote to disk 
drives directly from userland and relied on GEOM to pick up the changes 
via the "spoil" mechanism - which is why they couldn't write to 
partition tables if a file system on one of the partition was mounted, 
etc., requiring hacks like kern.geom.debugflags=16 to drop the 
permission (actually reference counting) checks.

Gpart has a kernel-userland interface so that the userland part(s) tell 
the kernel what they need and the kernel does the writing (if applicable).