Mail Archives: opendos/1997/02/15/11:07:25
On 10 Feb 97, Weiqi Gao <weiqigao AT crl DOT com> wrote
> While we are on the topic of MBRs and dual boots, I would like to make
> things clearer. It is my impression that:
> 1. The A:\> sys a:\ c: command run from a MS DOS 6.22 or OpenDOS 7.01 boot
> floppy will do the following:
> Copy the three system files to C:\
> Write the MBR.
> 2. The FDISK /MBR command will write the MBR to C:\.
> If the above impressions are true, then I think I've got the answer to
> multi booting MS DOS, OpenDOS and Linux with grub 0.4. The trick is to
> write the MS DOS and OpenDOS MBRs to DOS files with the DEBUG command, and
> have grub boot off the files:
>
> C:\> DEBUG
> -l 100 2 0 1
> -rcx
> CX 0000
> :200
> -n MSDOS.MBR
> -w 100
> Writing 00200 bytes
> -q
>
> This will write the MBR on the C drive to the file MSDOS.MBR. You can then
> write the OpenDOS MBR to OPEMDOS.MBR after running SYS from the OpenDOS
> boot floppy.
>
> To boot from a file instead of the MBR, you only need to change the
> chainloader=+1
> line to something like
> chainloader=(hd0, 1)/msdos.mbr
> for the MS DOS boot stanza. Similarly for OpenDOS and Linux.
>
> Since grub have knowledge of the FAT and ext2fs file systems, it will find
> the MBRs and the Linux kernel file, and boot from there.
>
> I haven't tried this yet, but I believe this will work.
(sorry for the long quote, I didn't know where to snip :-)
Has anyone else tried it? I've read several postings about the Grub
bootmanager - and the above method spells ingenuity to me!
But, is it safe (the debug script)? If not, does anyone know if there
is any software (free/sharew) available which will perform this saving
of MBR to file? If the above method is safe, how does one reverse the
process, if ever needed? I guess I can't use Grub when I use disk
compression? Still, I would appreciate any information and pointers
about this, since among other things I would like to be able to copy
the MBR to a file and then use a file comparison utility at boot time -
to check the boot sector for changes - kind of a integrity check
against boot virus. Also, I guess I will be using Grub later, so,
anyway - suggestions appreciated. Anyone?
Thanks,
Bjorn
-learning
mailto:Bjorn DOT Simonsen AT aorg DOT uib DOT no
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