Re: grub-install

[Yoshinori K. Okuji]

On Monday 25 July 2005 18:35, Marco Gerards wrote:
> So an example of a boot process is:
>
> - The BIOS loads the GRUB2 (boot.img) as it is stored in the MBR
>
> - GRUB2 in the MBR loads that 31KB into memory and jumps to it
>
> - That 31KB consists of the kernel (kernel.img) and some raw modules

In details, the core image consists of diskboot.img, kernel.img then zero or 
more modules. boot.img loads only the first sector (diskboot.img) from a 
disk, and diskboot.img loads the rest of the core image.

In the case of PXE, pxeboot.img is prepended to the core image, and simply 
jumps to the start address in kernel.img, because PXE ROM loads the whole 
core image from a network.

> - The kernel (rescue mode) starts and loads every module

The kernel initializes the system briefly, and decompresses the compressed 
part of the core image. After this, the kernel loads all pre-loaded modules 
from the memory.

> I hope this e-mail made clear how GRUB 2 basically works on the PC.
> I am not a PC expert and my English is not that good.  Hopefully
> someone can and will correct me if I was wrong so I will understand
> things better.  Hopefully Hollis' question is answered.

Your description is really good.

Well, the bootstrap on i386-pc is complicated, because PC BIOS sucks. On other 
architectures, this can be simplified very much.

Okuji