Grub and two distros

[Jim Cornette]

Anne Wilson wrote:
>
> I've read everything I can, including the thread mentioned above, and
> I'm still not happy.  I think it's a complete lack of understanding
> of the boot process.  I have always installed grub to the MBR, and
> thought that this simply called up menu.lst, read the stanzas there
> and proceeded to carry out the selected stanza.  Now it seems that
> things are not that simple, so I have to ask you to return to
> absolute basics.
> 
> It seems that I should install grub into the root partition for the
> particular distro - correct?

Yes, this needs done for each installation so the distro knows where to 
update its related grub.conf/menu.lst file when kernels are upgraded.

> 
> If the other distro is not automatically added I then will need to
> manually edit menu.lst to add a stanza for the other distro -
> correct?

Usually all you need is to edit the grub.conf in the install where Grub 
is installed into the MBR. The other installations if grub was installed 
in their root partition should do the rest once they are chainloaded 
from the grub installed in MBR. You should see the first selection menu. 
Once selected, you should see the grub menu for whatever distro was 
chainloaded.

> 
> I presume that I will also have to manually edit the menu.lst on the
> other distro?

No, just the one that initially starts the boot. The other installations 
only need their booting information.
Once you leave the MBR grub into a chainloaded distro the MBR installed 
one leaves the picture and whatever chainloaded OS takes over with their 
booting programs.
> 
> Exactly how does either of these get called?  IOW, what tells it
> which one to call?

The first grub installed in MBR uses grub commands to hand over 
operation to the other distro. Whatever the normal booting process for 
the other distros taks over past the chainload.
If you installed nothing in MBR, the active partition would boot first. 
Using MBR in my view for the first installation is easiest and less 
confusing in my view.
> 
> Then there's the matter of kernel updates.  Fedora has a default
> number for keeping kernels - how will it know to only handle its own
> kernels and kernel entries in menu.lst?  And if it doesn't, will I
> have to manually edit menu.lst every time there is a kernel update
> (having made a routine of backing up menu.lst)?

If done correctly the other distros will go by their kernel saving 
information and not interfere with the others.
On shared /boot partition setups as some have, kernels removed in the 
erasing of the program also delete their entry from grub when they are 
removed on the cleanup in rpm based distros. The system does not know 
about the other stanzas to my knowledge, just info as part of uninstall 
for other rpm packages kernels installed and removed.

> 
> The example I downloaded, which concerned a RHLinux install and a
> Mandrake one, only used chainloader for the floppy stanza.  I know it
> gets used for a Windows stanza.  Does that mean that it doesn't get
> used for two Linux distros?

Unclear to me what is asked. If you mean the handoff via chainloading, 
nothing of the the original grub is referenced from then on.

> 
> I think that most of my questions covered.  Maybe I'll feel more
> confident when I understand these issues better :-)
> 

I'm sure you'll be able to master the concept once you understand the 
portion of grub is to hand off control from BIOS to whatever OS you are 
to use. It is just a go between process and not a big powerful program.

Jim

-- 
He who has imagination without learning has wings but no feet.