[SOLVED] Grub2 chainloader

nze · 09-19-2010, 05:14 PM

Hi,
I have a dedicated grub2 partition from where I can chainload into my arch linux grub2 with

Code:

menuentry "Arch Linux" {
        insmod ext2
        set root='(hd0,6)'
        search --no-floppy --fs-uuid --set d2c1d2c1-6b8e-4e9d-827b-1239bc470395
        chainloader +1
}

now i'd also like to go back to the grub partition, so I added this to the arch grub2:

Code:

menuentry 'OS Selector' {
        insmod ext2
        set root='(hd0,3)'   #this is sda3
        chainloader +1
}

but just get 'invalid signature' errors.

what am i doing wrong?

Okay, after another 87 reboots I got it figured out now.
Apparently grub 1.98 still uses 'chainloader' for stuff like Windows, while grub itself works more like starting a linux kernel, using the 'multiboot' keyword instead of 'linux' though, and then pointing to the right file (grub-kernel-image: core.img). The result looks like this:

Code:

menuentry 'OS Selector' {
        search --fs-uuid --set f5d9c7fc-23eb-4473-abb6-5f11fc6c3c1b
        multiboot /boot/grub/core.img
}

the 'search...' line can be replaced with a conventional 'root (hdX,Y)', but I like it better this way, as moving around partitions won't affect it. Maybe it's even valid to use both; grub2 documentation is rather sparse though..
One thing I still don't get straight, is why 'chainloader +1' still works in the first instance of grub (which might be v1.96 , maybe that's why..).

MensaWater · 09-21-2010, 03:43 PM

Thanks for posting your solution.

JZL240I-U · 09-22-2010, 06:27 AM

You might also want to correct some typos(?):

You use """ and ''' after menuentry. Which one is correct or do both work?

set root='(hd0,3)' #this is sda3 <--- it is not. hd0,3 stands for /dev/sda4

HTH.

nze · 09-23-2010, 04:17 AM

Quote:

Originally Posted by JZL240I-U

You might also want to correct some typos(?):

You use """ and ''' after menuentry. Which one is correct or do both work?

set root='(hd0,3)' #this is sda3 <--- it is not. hd0,3 stands for /dev/sda4

HTH.

as far as i can tell both ' and " work, as grub2 does some variable expansion, i'd guess it works bash-like regarding variables. i don't think there's a big difference.

with grub2, partition numbering changed, now starting with 1 instead of 0 (as in grub legacy). device numbering still starts at 0 though. so sda3 is now referred to as (hd0,3), thus the comment

Quote:

Originally Posted by MensaWater

Thanks for posting your solution.

welcome

JZL240I-U · 09-24-2010, 12:58 AM

Quote:

Originally Posted by nze

...with grub2, partition numbering changed...

Uargh. Those are changes of a type I hate

. Thanks for pointing this out.