Help please!

[Patrick Cole]

Mon, May 20, 2002 at 02:04:01PM +1000, Stephen Hodgman wrote:


> I have a system with an IDE drive with bootable Debian potato on it. (/dev/hda).
> this disk works fine and I can boot OK.
> I have a SCSI disk /dev/sda which has Potato on it also.  However when I make the 
> scsi disk the boot disk I get "LIL-" and nothing.  Doco suggests running lilo to fix it but 
> I am getting nowhere with that.  This is what I am doing:
[...]
> I then reboot, change the scsi disk to be the first boot device and get "LIL-"
> Now, I had this working last week (Grr...) 
> What stupid thing have I done please?  thanks.

This is because when you run lilo it discovers the bios geometry for the
given disks in boot= and root= and stores that in the bootsector to get
to where it needs to go. When you have your system with hda as the first
hard drive, this will map to bios disk 0x80, and your scsi disk will be
somewhere after that (0x81 if you have no more disks after hda apart
from your scsi drive).  It also depends on which sequence your
controller bioses initialise - more often than not though, on board
controllers initialise and assign bios disk numbers first unless your
motherboard bios has the option to init the scsi adapter first. The problem 
stems from the fact that when you're running lilo your first disk (hda) is 
0x80, and your scsi disk is something else, but when you tell the scsi bios 
to init first, the scsi disk becomes 0x80, and lilo gets very confused as
it's looking for a root partition on disk 0x81 which is now your IDE
disk, but you want it to be your scsi disk. 

So what you have to do is force lilo to use a specific bios disk number, 
like such:

disk=/dev/sda
	bios=0x80
disk=/dev/hda
	bios=0x81

And then lilo should be a happy camper when you swap the sda over to
0x80 to boot it.

Of course naturally 0x81 might not be the right one if you have more
than the two disks, but you get the picture.

-- 
Patrick Cole <Patrick.Cole at anu.edu.au>
Programmer, the John Curtin School of Medical Research, ANU 
PGP 1024R/60D74C7D C8E0BC7969BE7899AA0FEB16F84BFE5A