[lfs-support] Q: HOWTO: chainload from GRUB2 on /dev/sdb to GRUB2 on /dev/sda ?

Bruce Dubbs bruce.dubbs at gmail.com
Sun Feb 26 13:33:54 PST 2012

Jeremy Henty wrote:
> My working system  is LFS 6.6 on  /dev/sdb and I have a  brand new LFS
> 6.7 on /dev/sda .  I would like to chainload from GRUB2 on /dev/sdb to
> GRUB2 on /dev/sda .
> My first attempt was this entry in /boot/grub/grub.cfg on /dev/sdb:
>     menuentry "LFS 6.7" {
>             set root=(hd0)
>             chainloader +1
>     }
> ... but  that fails immediately - I  see a message from  GRUB and then
> almost instantly return  to the main menu.  I  tried removing the "+1"
> but then I get "Error,  no file specified, press <Return>"[1], which I
> *think* means  that the chainloader  command is complaining  about not
> having an argument.
> I can boot from  /dev/sda by changing the boot order in  the BIOS so I
> know that  GRUB2 is there  and working.  Also,  /boot/grub/grub.cfg on
> /dev/sda specifies "root=(hd0)" so  the "root=" line is correct.  What
> is going wrong?  Surely there is a way to get GRUB2 to do this.

I don't know how to exactly do what you are trying to do, but try 
dropping to the grub command line and manually try some commands (ls, 
etc).  You might want to try something like:

grub> root (hd0,1)
grub> kernel /boot/grub/core.img
grub> boot

   -- Bruce

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