Boot problems afther reinstall windows

[Alex de Kruijff]

On Tue, Mar 15, 2005 at 07:05:58PM -0500, Jerry McAllister wrote:
> > > > timeout=10
> > > > default=c:\freebsd.bin
> > > > [operating systems]
> > > > multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP
> > > > Professional" /fastdetect /NoExecute=OptIn
> > > > c:\freebsd.bin="FreeBSD 5"
> > > > 
> > > > This works for me. I still wonder why the stuff below didn't work. In
> > > > the past I would do this with /stand/sysinstall. But I don't dare to do
> > > > this with FreeBSD 5 because of drive geometric warnings.
> > > > 
> > > 
> > > Remember there are two boot blocks, so to speak.
> > > There is the MBR that lets you choose which slice to boot.  There is 
> > > only one of those per disk and it lives in "sector 0" of the disk.
> > > The MBR generally has a standard calling sequence (that the Bios calls)
> > > and sets things up to a fairly standard condition and looks for
> > > standard appearing boot sectors in slices and makes a standard
> > > call to the selected slice's boot sector.   Almost any MBR that
> > > knows how to recognize a standard boot sector in a slice and lets
> > > you choose between them if there are more than one can be used
> > > interchangeably.
> > > 
> > > Then there is the boot block with the actual boot loader that starts 
> > > pulling the OS from the bootable partition.   On a multi boot disk 
> > > there are several - one per each bootable slice and they live in the 
> > > boot sector of each slice.    Those are specific to the OS they are 
> > > booting.  Though their calling sequence is standard, what they have 
> > > to do to load and start their own OS is not.
> > 
> > Is it posible to boot one OS if you only have the MBR?
> 
> No, you need the boot sector.   If you have only that in the first
> location, you can boot without an full MBR, I think, but not without
> the boot sector that the MBR loads and jumps to.

But its not posible to put the code of the boot sector in the MBR
place? (i.e. doesn't fit)

> > > I am guessing that you managed to overwrite or damage the MS slice'
> > > boot sector while you were doing things, or didn't get it written
> > > to the slice properly when you reloaded or something like that.
> > > Even though you put the MBR back with FreeBSD's fdisk, did you
> > > also make sure that the MS slice had its own boot loader?   Anyway
> > > you did when you put the MS boot loader back.   So it works now.

I think the anwser to you question should be no. It booted before I put
the MBR back.

> > The previous time I first installed windows and then FreeBSD 5. The
> > difference this time is that I didn't use /stand/sysinstall. This
> > because I would get into serious troubel. (I never found out how to
> > force the right geometry) So I was thinking maybe sysinstall does
> > something (like copy the MBR to the second boot location) that I didn't
> > do manualy.
> 
> I think you are using MBR for boot sector.  

I think you mean by word and not on disk.

> The MBR is what goes
> in sector 0 of the disk itself.   The boot sector/record/block
> goes in the first sector of the slice.   The MBR lets you pick the
> slice you want to boot and then loads its boot sector/block/record and 
> jumps to it in a standard location.

MBR = /boot/boot0 (a copy of it)
boot sector = /boot/boot1

What I was thinking is: 
Now windows overwrites the MBR. And I was thinking it would put the boot
sector in the place of MBR. If this is the case then windows looses the
capability to boot.

-- 
Alex

Please copy the original recipients, otherwise I may not read your reply.
WWW: http://www.kruijff.org/alex/FreeBSD/