cvs commit: src/sys/amd64/conf GENERIC src/sys/arm/conf EP80219 src/sys/conf NOTES files files.powerpc options src/sys/geom geom_apple.c geom_gpt.c src/sys/geom/part g_part.c g_part.h g_part_apm.c g_part_gpt.c g_part_if.m src/sys/i386/conf GENERIC ...

John Baldwin jhb at
Wed Feb 7 23:44:46 UTC 2007

On Wednesday 07 February 2007 18:29, Nate Lawson wrote:
> Robert Watson wrote:
> > 
> > On Wed, 7 Feb 2007, Poul-Henning Kamp wrote:
> > 
> >> In message <20070207200130.J23167 at>, Robert Watson 
> >> writes:
> >>
> >>>>  The ctlreq interface supports verbs to create and destroy
> >>>>  partitioning schemes on a disk; to add, delete and modify
> >>>>  partitions; and to commit or undo changes made.
> >>>
> >>> Does this mean we can expect to see the disabling of GEOM 
> >>> exclusive-use protections disappear from normal administrative 
> >>> activities soon, as there will now be approved channels to 
> >>> incrementally change the layout of in-use partition tables?
> >>
> >> There is already a mechanism for that.  How do you think bsdlabel(8) 
> >> and fdisk(8) works ?
> > 
> > I understand that.  This was a pragmatic question rather than a 
> > philosophical question: I know it can be done, but is it now being 
> > done.  The answer appears to be yes.
> I assume phk@ is referring to the geom debug flags sysctl.  The problem 
> with that approach is that it disabled (and potentially left disabled if 
> the flag wasn't cleared as the tool exits) all protection for the 
> devnode behind the mounted drive.  If something else was running at the 
> same time, it could overwrite any data on the devnode.  Or the fdisk 
> tool could write anywhere in the device, not just the boot sector.

No, fdisk and bsdlabel don't frob the sysctl, they talk directly to GEOM to 
update the stuff as well using MBR-specific or BSD label-specific requests.
John Baldwin

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