aliasing (or renaming) kern.geom.debugflags

Benjamin Kaduk kaduk at MIT.EDU
Fri Oct 7 17:51:50 UTC 2011


On Fri, 7 Oct 2011, Garrett Cooper wrote:

> On Fri, Oct 7, 2011 at 10:42 AM, Benjamin Kaduk <kaduk at mit.edu> wrote:
>> Dear all,
>>
>> I feel like this has come up before, but a quick search didn't reveal
>> anything terribly recent, at least.
>>
>> The new installation chapter of the handbook for 9.0 (that Warren and Glen
>> and Garrett and Gavin and more people I am probably missing have sunk huge
>> amounts of time into) has instructions on (e.g.) preparing a USB stick
>> install image:
>> http://www.glenbarber.us/FreeBSD9/doc/en_US.ISO8859-1/books/handbook/install-pre.html
>> (scroll down most of the way).  But in order to do so, the instructions
>> include 'sysctl kern.geom.debugflags=16'!  Now, an ordinary user who is
>> doing this for the first time might ask, "why do I need to do something with
>> 'debugflags' in order to make a USB stick?  I'm not debugging anything, this
>> is a standard operation!".
>>
>> I can't really advocate for changing the geom logic at this point in the
>> release cycle (though it's not really clear why rank 1 geom providers need
>> to be so special), but I think it would be nice to have a user-visible
>> interface to it that does not have "debug" in the name, since the actual
>> flags are apparently here for the long haul.  I could certainly imagine
>> aliasing the debugflags to just "flags", which seems more
>> innocuous-sounding.
>>
>> Does this sound crazy?
>
> Yes. From geom(4):
>
> DIAGNOSTICS
>     Several flags are provided for tracing GEOM operations and unlocking pro-
>     tection mechanisms via the kern.geom.debugflags sysctl.  All of these
>     flags are off by default, and great care should be taken in turning them
>     on.
>
> geom(4) has more details about what they do.

I'm not sure I follow your point.  Yes, geom(4) describes what they do; my 
objection is to the use of "debug" to describe the one in particular that 
we tell new users to blindly set.  A hypothetical kern.geom.flags need not 
allow setting (e.g.) "0x01 (G_T_TOPOLOGY) Provide tracing of topology 
change events" if we don't want it to.

-Ben


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