Re: Grub and my second hard disk

[Thierry Laronde]

On Sat, Dec 07, 2002 at 11:35:36PM +0100, Csaba Henk wrote:
>  Hi!
> 
>  I use grub-0.91.
>  Eariler I had only one hard disk attached as IDE Primary Master. I used
> Grub with it with no problem.
>  Then I bought another HD. Then I attached this new HD as IDE Primary
> Master (/dev/hda) and put the old one on IDE Secondary Slave (/dev/hdd). I
> reintstalled Grub on /dev/hdd [with 
> root (hd1,7)  
> setup (hd1) ], 
> but when I wanted to boot from it, there was displayed only "GRUB" at the
> bottom of my screen (no error message), and then the system got frozen. I
> tried it several times, and I always got this result.
>  Then I set IDE Primary Master to "None" in the BIOS, and I tried again to
> install Grub on /dev/hdd, according to the changes, with 
> root (hd0,7)
> setup (hd0) ,
> and I succeeded! Everything worked fine also when I switched back IDE
> Primary Master to "Auto" in BIOS. 
>  So finally I solved my problem but this phenomenon is strange to me, I
> think it can be called a bug.

No.
If you boot _from_ this very disk (the second one i.e. slave on secondary
IDE bus) this disk is for the BIOS the first one (booting disk is 0x80). 
The BIOS loads the MBR of the slave on secondary IDE (GRUB's stage1) whom
you instructed to load the remaining stuff from the "other" disk (hd1). 
Hence GRUB tries to seek for its files on the "other" disk i.e. master on
primary IDE (which has became 0x81).

So, indeed correct solution is to tell GRUB to load the files from this very
disk, not mentionning explicitely what it is (new version of GRUB does that 
by default now ; previous version, 0.91 included, enforced a specification 
of the drive), or to tell it to load from "hd0", taking this as identical 
to "booting disk" (that's why the second solution succeeded but this has 
nothing to do with setting primary IDE master to none or auto, except that 
disabling the first disk it was more simple to install GRUB on second disk 
by telling it the root for its files where on "hd0" --- to achieve this 
while leaving first disk, you would have to swap virtually for GRUB's sake 
the two disks).

This is not a bug, this is a BIOS feature.

Cheers,
-- 
Thierry Laronde (Alceste) <address@hidden>
Key fingerprint = 0FF7 E906 FBAF FE95 FD89  250D 52B1 AE95 6006 F40C