BOIS Blues again

[Rick Stevens]

On Sat, 2007-08-25 at 16:02 -0600, Karl Larsen wrote:
> Aaron Konstam wrote:
> > On Sat, 2007-08-25 at 11:28 -0600, Karl Larsen wrote:
> >   
> >> Here is what worked for years: The Grub was on disk hd0 and Linux 
> >> was on hd0,0 thru 6 and hd1,0 thru 7. The BIOS could find all the Linux 
> >> /boot/grub/ without fail.
> >>
> >>     Now I have just one hard drive all set in the BIOS setup and I went 
> >> up in the F7 Rescue cd and told grub the following:
> >>
> >> Grub> root (hd0,5)
> >> Grub> setup (hd0)
> >> Grub> quit
> >>
> >> This worked according to the written info from grub. But It would not 
> >> work. I would get a bios error.
> >>
> >>     So I installed FC6 basic in the (hd0,0) partition and it worked 
> >> fine. Then I added the directions to this F7 and of course Grub found 
> >> it. Here I am again on the old computer.
> >>     
> > This would work only if the grub boot block was partition 5 and you had
> > another boot loader that would know to go to partition 5 to look for the
> > grub boot block. I can't believe you read instructions that told you to
> > do this.
> >   
> 
>     Well as it works out I found out how to have the root 10,000 
> cylinders away from the MBR and it works just fine with my old bios. 
> Right now I'm using grub in partition /dev/sda6/ to boot and it works 
> fine because while in /dev/sda6/ I typed grub-install and it did it right!
> 
>     This is why I fear an error on my part or a bug for grub.

This is not a bug in grub.  Your BIOS can only boot from a bootblock
that's within the first 1024 CYLINDERS, regardless of which block it is.
This is one of the reasons that the HDA mode of your hard drive was
invented.  In HDA mode, the drive can mask its true geometry and make
every block of the entire disk appear as though its in the first 1024
cylinders.

If grub is your only boot loader, it should be placed in the master boot
record (MBR) of your first hard drive (or whichever drive you tell your
BIOS it should boot from).  The MBR is the first usable block of the
drive.  Once the first-level grub loader is in the memory, it can boot
any second-level loader from anywhere on the disk (or any disk).  Grub
doesn't have the 1024 cylinder or number-of-drives limit that BIOS does.

----------------------------------------------------------------------
- Rick Stevens, Principal Engineer             rstevens at internap.com -
- CDN Systems, Internap, Inc.                http://www.internap.com -
-                                                                    -
-      Batteries not included.  Offer not valid in some states.      -
-           Your mileage may vary.  Void where prohibited.           -
----------------------------------------------------------------------