Re: Boot problems afther reinstall windows

• Previous message: Ted Mittelstaedt: "RE: Mucking with other drive"
• In reply to: Jerry McAllister: "Re: Boot problems afther reinstall windows"
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Date: Fri, 18 Mar 2005 08:09:56 +0100
To: Jerry McAllister <jerrymc@clunix.cl.msu.edu>

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/
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• Previous message: Ted Mittelstaedt: "RE: Mucking with other drive"
• In reply to: Jerry McAllister: "Re: Boot problems afther reinstall windows"
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