Grub Manual

Mikkel L. Ellertson mikkel at infinity-ltd.com
Fri Oct 19 19:30:46 UTC 2007


William Case wrote:
> Hi;
> 
> To do that Grub needs its own generic file system (rudimentary though it
> is) and it's own small kernel that allows it to operate on *any*
> machine.  The manuals (although I agree they could have some basic (less
> technical) explanations included) deal only with the GRUB file system
> and kernel making no assumptions about the partitions/files/kernel(s)
> that will eventually be loaded.
> 
Not exactly correct. Grub first stage is in the boot record - ether
the MBR or the partition boot record. This is a small boot loader
that uses the BIOS to ether load stage 2, or stage 1.5. If it loads
stage 1.5, it then can read the grub menu and stage 2 from the file
system that stage 1.5 understands. Part of the Grub install process
tells it where to find stage 1.5 and the file system for stage 2 and
the menu. This can be any of the file systems that have a stage 1.5
for them. If I am reading thing correctly, stage 1.5 must be in a
fixed location. So if you relocate it, you must update the pointers
in stage 1.

I am less clear about how it handles loading stage 2 directly,
without loading a stage 1.5. I have never used this feature, and I
am not even sure how to install Grub that way. I would expect that
stage 1 would have pointers to stage 2 instead of stage 1.5, and you
would have to update pointers when you make changes as you do when
using LILO. I would love to hear from someone that uses Grub this way.

Mikkel
-- 

  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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