RFC: Multiboot Guide

[Tim]

On Mon, 2015-06-01 at 12:32 +0100, Timothy Murphy wrote:
> Is it possible to boot into a system using the old grub
> by employing a chainloader as for Windows?
> If so, is this documented somewhere?

It certainly used to be, you'd just chainload the partition with the
other GRUB's bootcode in it.  And just like booting Windows passes
control over to what GRUB chainloads, you could chainload something
else.

e.g. You'd installed one OS on a drive in /dev/sda and another OS was
installed in /dev/sdb.  Each drive had the usual partitions on it
(boot, /, home, etc.).  Each drive had the bootloader in the beginning
of the drive.  Each drive's own /boot/grub/grub.cfg could have an entry
pointing to the other drive, setting it as GRUB's root.

Remember you're setting the root for GRUB, not the system root (/).

My guesses would be that you might not be:
(a) Setting the right partition for GRUB to try and chainload.
(b) Linux's kernel line in the GRUB config isn't pointing to /boot (use
the UUID, instead of /dev/sda, as drives can get renumbered when booting
up in a different sequence).

-- 
tim at localhost ~]$ uname -rsvp

Linux 3.19.8-100.fc20.i686 #1 SMP Tue May 12 17:42:35 UTC 2015 i686

All mail to my mailbox is automatically deleted, there is no point trying
to privately email me, I will only read messages posted to the public lists.

George Orwell's '1984' was supposed to be a warning against tyranny, not
a set of instructions for supposedly democratic governments.