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Re: GRUB discussion follow up ?



On 10/21/07, Robert P. J. Day <rpjday crashcourse ca> wrote:
> On Sun, 21 Oct 2007, Jacques B. wrote:
>
> > ... And as Robert indicated, the 512 bytes is broken down as MBR for
> > 446 bytes, 64 bytes for partition table (4 X 15), and 2 byte magic
>                                                ^^ 16 :-)
> > number \x55\xaa.  I spent a bit of time last Spring trying to figure
> > out where in the MBR code was the info telling it where to get stage
> > 1.5. I didn't spend any real significant time on it seeing it was
> > way beyond what I had to understand so dropped it due to lack of
> > time.  If you figure out that info I'd be interested.
>
> the GRUB code in the MBR doesn't jump to the stage 1.5 code
> immediately.  from memory (a long while back), more of GRUB is
> installed in the remaining 20K of the hard drive after the MBR.  i
> (vaguely) remember this when *i* was wondering how the hell GRUB
> worked, and i perused the source of the grub install command.  that's
> where i noticed more GRUB code being written to offset 1K -> 20K of
> the hard drive.
>
> in any event, /sbin/grub-install is a shell script on fedora, so it's
> readable.
>
> rday
> --
> ========================================================================
> Robert P. J. Day
> Linux Consulting, Training and Annoying Kernel Pedantry
> Waterloo, Ontario, CANADA

I'll have to check out beyond the 1K mark, as well as check out
grub-install.  Also I noticed my touch typing was off a bit.  I put 15
bytes instead of 16 bytes X 4 for the partition table.

Seeing grub has to do with booting, as a slight tangent any suggested
readings for the Linux boot process (actually not only Linux, but
including Grub & Lilo boot loaders).  I found some (it's back at the
office) when I was digging into the boot process a while back.  I was
also looking at the possibility of using bootchart from bootchart.org
as a tool to better understand the boot process.  Anybody play with
that?  If so your thoughts on using it to better understand the boot
process...  Sorry if I'm hijacking this thread.  Hopefully it falls
within the realm of grub discussion follow up.

Jacques B.

Jacques B.


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