Re: Misleading device mapping when installing Grub on second disk.

[tlaronde]

En réponse à Stefano Giorgi <address@hidden>:

Hello,

> I have first hard disk /dev/hda with WinXP and the second disk /dev/hdb
> 
> with linux. I booted the system with floppy, and now I am trying to 
> install grub ont the MBR of disk /dev/hdb.
> Looking at /boot/grub/device.map I first I tried with a grub.conf like
> this:
> ------------------------------------------
> title Red Hat Linux (2.4.18-14)
>         root (hd1,0)
>         kernel /boot/vmlinuz-2.4.18-14 ro root=/dev/hdb1 hdd=ide-scsi
>         initrd /boot/initrd-2.4.18-14.img
> title XP
>         rootnoverify (hd0,0)
>         chainloader +1
>         makeactive
> -------------------------
> and installed grub with grub-install /dev/hdb but it didn' work.
> It seems that if I install grub on disk /dev/hdb this disk will be 
> recognized by grub as the first disk, and reference it as disk hd0, not
> 
> hd1. To make it work I had to change it to:

If you install GRUB on the second disk's MBR, this means that you have to change
your BIOS settings to boot from second hard disk which becomes, for the BIOS, 
the first one (nothing to do with the BUS). Since GRUB relies on the BIOS, for
GRUB this disk is presented like the first one.

To achieve exactly what you want, you will have to install GRUB's MBR on the 
first disk configuring it to load stage2 from second disk. The problem being: is
the MBR installed by Windows XP a classical one (in this case, this will work). 
Are there any caveats about another undocumented feature of M$?

At least, this works the way you have done, but I hope you have an explanation 
now.