Booting FreeBSD-5.3 from NTLDR

Rakhesh Sasidharan rakhesh.s at
Tue Feb 1 07:32:10 PST 2005

On Tue, 1 Feb 2005 19:04:07 +0400, Rakhesh Sasidharan
<rakhesh.s at> wrote:
> On Tue, 1 Feb 2005 04:10:49 -0800, Loren M. Lang <lorenl at> wrote:
> > I think that you should be able to use boot0 and boot1 as a file once
> > the apropriate fields are filled in.  When boot0 and boot1 are written
> > to the disk in their special locations, several bytes of each file are
> > modified to reflex various paramaters like which disk or partition they
> > should use.  You should be able to extract them with dd and boot them
> > externally from my understanding of it.  boot1 is normally written to
> > the first sector of the partitionthat freebsd is installed on, if that's
> > the first partition on ur second hard drive then:
> >
> > dd if=/dev/ad1s1 of=boot1.img count=1
> >
> > will extract the file to boot1.img might NTLDR should be able to use.
> >
> > dd if=/dev/ad1 of=boot0.img count=1

I just tried these again. Same results as when I had used the "bs=512"
option. Extracting "boot0.img" gets me back to the NTLDR screen;
extracting "boot1.img" gives me a "Boot Error" message.

But what you said above gave me an idea. Possibly BootPart modifies
the extracted bootsectors specially, changing the special parameters
to enable booting of the second disk from the first? Its a thought ...
maybe the way these files are written to the disk (from where dd
extracts them), the special parameters are not such that they can be
booted from the first disk. But when BootPart extracts the sectors, it
modifies these parameters, enabling the booting. What say?

				-- Rakhesh
				   rax at

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