Dual booting problems

Jerry McAllister jerrymc at msu.edu
Fri Mar 2 18:13:59 UTC 2007

On Fri, Mar 02, 2007 at 05:52:52PM +0000, RW wrote:

> On Fri, 2 Mar 2007 11:37:26 -0500
> Jerry McAllister <jerrymc at msu.edu> wrote:
> > On Fri, Mar 02, 2007 at 12:34:10AM +0000, RW wrote:
> > 
> > > On Thu, 1 Mar 2007 13:30:26 -0900
> > > Beech Rintoul <beech at alaskaparadise.com> wrote:
> > > 
> > > > I should also mention that you need the FreeBSD boot manager on
> > > > both disks, or an alternative boot manager such as grub or gag.
> > > > Read the handbook.
> > > 
> > > I recall reading that too, but I've never understood what it's
> > > supposed to achieve. I imagine it must be a quirk of the FreeBSD
> > > boot manager, I've certainly never needed to install more than one
> > > copy of GAG or LILO. 
> > 
> > If you select F5 (maybe F6 or more,  I should try that some time) it
> > will instead cause the MBR from that second (maybe third, etc) disk
> > to be loaded and passes control to it.   Then that MBR looks at its
> > own slice table and makes up a menu if there are more than one
> > bootable slices on that drive.   
> In other words it *is* a quirk of the FreeBSD boot manager, in that it
> doesn't allow you to chainload a partition on another drive directly.
> You have to chainload the intermediate MBR which needs a second copy of
> the bootmanager. Most bootmanagers can do this directly, using the
> partition table on the other drive.

I wouldn't call it a quirk of FreeBSD.   FreeBSD does it the 'canonical'
way.  The others use additional space on the rest of the track, that
is technically not available, to make a bigger program and tables that can 
do additional things.   That's nice, but not officially supported.

So, it is really a _quirk_ of Grub/Gag/others and not guaranteed to work.
What would be really nice is if the world just decided to create an
official standard that makes that whole track available since it
really most often is - actually, I don't know any modern system where
it is not, but I haven't made a survey.


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