svn commit: r237294 - user/ae/bootcode/sys/boot/i386/pmbr

[John Baldwin]

On Wednesday, June 20, 2012 8:55:14 am Andrey V. Elsukov wrote:
> On 20.06.2012 15:44, John Baldwin wrote:
> >>   Add one partition record to the PMBR image. It covers all space after
> >>   the LBA 0. It is better to have one partially correct record, than
> >>   have nothing.
> > 
> > This latter part is not true. :(
> > 
> > boot1 has a hardcoded partition in it (for use in dangerously dedicated mode).
> > This has a mixed history.  At one point the table entry it used caused certain
> > SCSI BIOSes to crash due to a divide by zero (the SCSI BIOS read the MBR to 
> > try to guess what C/H/S geometry the rest of the system was expecting).  I 
> > think having a hardcoded entry here can only really result in problems.  I 
> > would rather you add some sort of 'restore' functionality to gpart that 
> > allowed it to build a PMBR 'from scratch' with a proper partition entry than 
> > to resort to this hack.
> 
> AFAIK, DD mode is not supported now.

Correct, because it was a disasater.  Let's not create a new disaster.

> As another solution we can remove checking for PMBR partition type existence
> when detecting GPT (like the kernel does).

I think adding a suitable command to gpart to let it recover a disk is the
way to go.

-- 
John Baldwin