Is multi-GRUB2 setup possible? (S O)

[Tom Davies]

Hi :)
I think people are over-complicating this.  


Chain-loading is not really necessary to achieve the objective.  It means 2 
things have to work well instead of just 1.  Also i think the idea of all the 
different fail-safes using the same .cfg and that one being on the main 
hard-drive means that if the primary grub fails due to hard-drive failure then 
all the rest will too.  

As i understand it the objective is to set-up a machine with multiple physical 
hard-drives such that

1.  if one hard-drive fails the machine automatically boots into the Windows(?) 
on the next hard-drive and 

2.  so that each hard-drive could be moved into a different machine and still 
boot (this part has a few potential problems especially if it's Windows that is 
going to be used (all the "Found new hardware" and hardware detection and 
driver issues) so hopefully we can ignore this and just deal with 1&3) and 

3.  that after set-up the machine can be operated by a complete moron (as far 
as IT goes) that can't follow simple instructions and gets confused very easily 
and who can't give any useful feedback  (ie like at least 80% of normal users)  


Grub2 is easy to repair or reinstall plus it's very unlikely to break in the 
first place.  The Windows boot-loaders have always been notoriously flaky (ime) 
and many sys-admins have used Gnu&Linux boot-loaders to replace at least part 
of the Windows ones on machines that only have Windows and no Gnu&Linux beyond 
the boot-loader.  Plus it is usually on a robust journalised partition rather 
than a flaky Windows Ntfs one.  Again much more likely to recover smoothly.  


People that are used to Windows systems and exploring something else for the 
first time typically feel a bit scared and take exaggerated precautions.  I 
did.  


I installed Grub to all the various hard-drives on 2 machines and when i found 
i could install it onto Usb-sticks i made sure i had at least 1 with grub on it 
for each of the main systems i used.  Just a straight normal install of grub on 
each hard-drive does the trick.  


Test by unplugging your primary hard-drive and note that the machine does still 
boot.  If it doesn't then reinstall Grub to that 2nd hard-drive.  Then plug the 
primary hard-drive in and notice that it boots just fine too.  


If the test hadn't worked and you had been forced into reinstalling Grub2 then 
chances are that the problem was where you installed the MBR.  Each physical 
hard-drive has just 1 MBR.  Same with Usb-sticks and all other bootable media.  
For Cds and Dvds their MBR is on the Cd or Dvd.  Each MBR can only point to  
one single grub-menu or to a Windows boot-loader.  In the case of Grub it 
allows that the grub-menu the MBR points to could be on a completely different 
drive.  The mistake that often gets made is that people install Grub onto the 
2nd drive but put it's MBR part onto the primary hard-drive and then 
wipe&replace that MBR when they install Grub to another drive.  That leaves the 
2nd drive with no MBR pointing to a useful grub-menu.  It's really easy to fix 
but it's a bit difficult to wrap one's head around the concept.  

Something that really doesn't help is that Windows doesn't have a different 
name for lots of partitions on a single hard-drive compared to having lots of 
physical hard-drives.  It calls them all hard-drives.  So, according to Windows 
you could have a lot of hard-drives on a single hard-drive.  Somewhat confusing 
huh?!  Unfortunately those so-called hard-drives don't each have their own MBR. 
 It's the physical hard-drive that has the MBR.  MS tries to dumb things down 
to avoid confusing their users but the result is that people are more clueless 
as a result and get more confused by simple things.  It's only when i took the 
side of my machine's tower-case and started identifying what each box was for 
that i realised i only had 1 physical hard-drive.  What Windows calls 
'hard-drives' are called  "Partitions" by Gnu&Linux.  Each physical hard-drive 
can have many partitions or just 1.  That's another confusion that many Windows 
can't get past
 because they have been taught wrongly.  Even if Windows reports there only 
being 1 'hard-drive' that is still a partition on a hard-drive and not really a 
hard-drive.  With just 1 partition it seems like a pointless abstraction and 
remains difficult to get your head around if you are only familiar with 
Windows.  However even Windows has started using a separate partition as a 
recovery tool although they try to hide it from their visible systems.  So, 
they make it even more confusing but hopefully you can overcome that confusion. 
 

Good luck and regards from
Tom :)