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

Jeremy Henty onepoint at starurchin.org
Mon Feb 27 12:59:02 PST 2012


Bruce Dubbs wrote:

> Try:
> 
> grub> linux (hd0,1)/grub/core.img
> grub> boot

OK, I now have two grub.cfg entries that differ only in the path
argument to the linux command:

    menuentry "Chainload GRUB on (hd0,2)" {
            insmod ext2
            set root='(hd0,2)'
            search --no-floppy --fs-uuid --set 867d9de5-5308-445e-872c-134f5071a7fc
            linux /boot/grub/core.img
    }
    menuentry "GNU/Linux, with Linux 2.6.35.4-lfs-6.7" {
            insmod ext2
            set root='(hd0,2)'
            search --no-floppy --fs-uuid --set 867d9de5-5308-445e-872c-134f5071a7fc
            linux   /boot/vmlinux-2.6.35.4-lfs-6.7 root=/dev/sda2 ro
    }

The second one works (of course it completely bypasses the other GRUB2
installation and goes straight for  the kernel).  The first fails with
"invalid  magic number".   I am  guessing  that "linux"  is the  wrong
command to use  here but the only  thing I can think of  that might be
the right command  is "chainloader" - and I already  tried that and it
didn't work either.

It's frustrating - I can  only find explicit instructions for the case
where  you chainload  from one  GRUB2 to  a second  GRUB2 on  the boot
sector of  a partition (ie.  *not*  on the MBR of  another disk).  The
one time I saw someone else explicitly asking how to do what I want to
do the first  response they got was "why would you  want to do that?".
It  seems that  despite GRUB2's  famous flexibility  it just  does not
support what I want to do and no-one expects that it should.

Thanks again for your help.

Regards,

Jeremy Henty



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