Grub too long and 3 Linux

[Perry]

Le Monday 11 October 2010 19.27:27 Goh Lip, vous avez écrit (you wrote) :
> On Tuesday 12,October,2010 12:49 AM, Perry wrote:
> > OT : really the worst thing about this Grand Unified Bootloader is its
> > anagram, Grub, Grunt? Grab? Whereas Lilo was so sweet a name.
> 
> Celaka, Perry, nama saja.  :)  [what's in a name, a rose....]
> 
> But to elaborate......
> 
> Any kernel upgrade done at say, 10.10 will not be reflected in the
> grub.cfg of 10.04 unless 10.04 also do an update-grub.
This seems logical. (on Hardy I don't even seem to have a grub.cfg)
> 
> But, if you set *both* grub2 of 10.04 *and* 10.10 to mbr (sda),
Saya mengerty (I understand)
> so whenever update-grub is done at *either* OS, the most recent
that is the latest installed or updated version , not necessarily the newest.
(update-grub should be named reflect or enact or set-up grub because it does 
not perform an update, i.e. fetch the latest release)
> update-grub OS will be reset to mbr.
> 
> Regards - Goh Lip
> 


Le Monday 11 October 2010 22.21:00 Tom Bell, vous avez écrit (you wrote) :
>  On 10/11/2010 12:49 PM, Perry wrote:
>> Le Saturday 09 October 2010 17.36:02 Goh Lip, vous avez écrit (you wrote) :
>/* * * * * * * * Snip! * * * * * * * /
>
>
>>
>> Not sure I understand. I thought Grub had to be on the mbr, (taking the 
place
>> of M$ loader) unless the mbr contains another multiboot program that would
>> chainload through Grub. The BIOS always starts reading the mbr, no?
>> Also, as I understood it, the mbr is so small it can only contain enough 
code
>> to trigger the execution of more code stored elsewhere...then I'm not sure 
of
>> the details and where it is.
>>
>Actually, the MBR does not contain any code per se.  The purpose of the 
>MBR is to tell the BIOS
>how to handle booting the disk, if it is bootable.  Every bootable disk 
>must have an MBR!  
It was simply called a boot-block on old floppies.
>Non-
>bootable disks do not have MBRs.  The MBRs consist entirely of data and 
>instructions, not code.
Ha, Ha, interesting.
>Hope this clears up any misconceptions.
Yes, it helps, thanks a lot.
So I guess any Grub installation or update if set to the mbr (or the 
reinstallation of M$), will overwrite this mbr... and the Grub menu could well 
be on the mbr too. Then according to the OS selected the instructions and data 
in the mbr can redirect the booting process to the proper place in the proper 
partition.
It follows, if I understood correctly, that the mbr is really a "lowest common 
denominator", and any release or OS should be able to write it... but there is 
a catch: M$ pays no attention to other OS and Linux only copes "as well as it 
can", so if an old distro can not  (for example) read the formatting of a more 
recent partition it will fail to recognize it as a booting partition and 
include it in the menu. This is why one should do the update grub from the 
"most up-to-date" linux version.

Hope I've got it right this time.		Perry


-- 
BOFH excuse #4: static from nylon underwear