grb -> MBR question

Beowulf · External Since: Jan 15, 2006 Posts: 258

If I understand grub correctly (I may not, just learning it now), grub
bootloader can be installed to an MBR on either hda or hdb, even if
MS-Windows is on hda and Linux is on hdb. Is this correct? And if grub
puts bootloader on hdb, (1)would I need to tell the BIOS to use hdb then
as the first drive to check for booting? (2)if Windows is reinstalled to
hda and of course writes it chainloader/bootloader/whatever to hda, would
that then have no effect on the grub bootloader on hdb, meaning that
Windows would NOT overwrite the grub bootloader on hdb, meaning that the
grub bootloader would still be intact after a Windows reinstall? (this
seems like a good strategy if it would work).

imotgm · External Since: Nov 04, 2006 Posts: 275

On Mon, 01 Jan 2007 19:18:29 +0100, J.O. Aho wrote:

> Then you need to modify your /boot/grub/grub.conf, so that you have
> a boot line
>
> --- grub.conf ---
> title=Windows
> root (hd1,0)
> chainloader +1
> map (hd1) (hd0)
> map (hd0) (hd1)
> --- eof ---

Better;

--- menu.lst --- # OP did not say what distro Smile

title=Windows
rootnoverify (hd1,0)
map (hd1) (hd0)
map (hd0) (hd1)
makeactive
chainloader +1

For the most part, your way works, but some machines need the
"rootnoverify", and "makeactive" assures that the partition is seen as the
active partition that Windows needs. My Award BIOS has a nasty habit of
changing the active partition to various different partitions, at random.
I have no Windows on this machine, so it makes no difference to me, but it
could on the OP's machine. It may help, it can't hurt, it only needs
to be written once, so why not? Smile

--
imotgm
"Lost? Lost? I've never been lost... Been a tad confused for a
month or two, but never lost."

J.O. Aho · External Since: Mar 26, 2004 Posts: 2216

Dean Browning wrote:
> I have Linux on Drive 1 and XP Media Center on drive 2, how do I tell grub
> where to find windows and load it. Right now, when I try to load XP, grub
> executes the default lines, but stops.

You need to see to that your /boot/grub/device.map has both hard drives

--- device.map ---
(fd0) /dev/floppy/0
(hd0) /dev/hda
(hd1) /dev/hdb
--- eof ---

Then you need to modify your /boot/grub/grub.conf, so that you have a boot line

--- grub.conf ---
title=Windows
root (hd1,0)
chainloader +1
map (hd1) (hd0)
map (hd0) (hd1)
--- eof ---

I think this should fix it for you, not sure, as I don't want to infect my
computers. For more information you can check Gentoo wiki on this matter, as
it works the same way in all distros that uses Grub.
http://gentoo-wiki.com/HOWTO_Dual_Boot_from_Windows_Bootloader_(NTLDR)_and_why

--

//Aho

Dean Browning · External Since: Jan 01, 2007 Posts: 3

It worked! Thank you very much.

Dean

J.O. Aho wrote:
> Dean Browning wrote:
>> I have Linux on Drive 1 and XP Media Center on drive 2, how do I tell
>> grub where to find windows and load it. Right now, when I try to load
>> XP, grub executes the default lines, but stops.
>
> You need to see to that your /boot/grub/device.map has both hard drives
>
> --- device.map ---
> (fd0) /dev/floppy/0
> (hd0) /dev/hda
> (hd1) /dev/hdb
> --- eof ---
>
> Then you need to modify your /boot/grub/grub.conf, so that you have a
> boot line
>
> --- grub.conf ---
> title=Windows
> root (hd1,0)
> chainloader +1
> map (hd1) (hd0)
> map (hd0) (hd1)
> --- eof ---
>
> I think this should fix it for you, not sure, as I don't want to infect
> my computers. For more information you can check Gentoo wiki on this
> matter, as it works the same way in all distros that uses Grub.
> http://gentoo-wiki.com/HOWTO_Dual_Boot_from_Windows_Bootloader_(NTLDR)_and_why
>
>