Re: loading grub from disk using qemu

[Glenn Washburn]

On Tue, 26 Nov 2024 22:41:40 +0000
Shaun <shaun@unix-scripts.com> wrote:

> I'm revisiting a old mailing list question I posted that I really never 
> got to work the way I wanted it too and I ended up abandoning what I was 
> doing as my time was needed elsewhere.  here's the original post link
> 
> https://lists.gnu.org/archive/html/help-grub/2017-02/msg00001.html
> 
> I do have a better understanding of building a grub kernel image and I 
> am able to get grub to load from the qemu instances disk.  The scenario 
> is the same, I'm looking to load grub from a disk with no partitioning, 
> so hd0. I'm still confused if I can load grub from the disk image.  Not

Why is having no partitioning a requirement? If this is going to work
on bare-metal at some point, your bios may not boot from a disk with no
partitioning. If you're only ever using QEMU, then it still might
depend on which firmware you use. Unless you're building GRUB as a QEMU
rom, in which case you're not loading GRUB from the disk.

> just the config file but actually load grub and it's modules from that 
> disk.  The main module I need these days is the blscfg module. I am able 
> to build an image, use it and run configfile /boot/grub/grub.cfg and 
> then if I drop into a shell do insmod blscfg and load that module 
> however what I feel is probably happening is that my grub image is just 
> loading that module from the disk which seams to work but my concern 
> here is that the modules on that disk may of been built for a different 
> version of grub depending on the distro.  For example redhat based 

This is confusing. You're talking about loading GRUB from a disk with
no partitioning, and then also saying that the disk might have modules
from a different version of GRUB from a distro. Please be real specific
about what your situation looks like. Its not clear to me precisely
what you're trying to do.

> Quick final question, do you plan to bring add blscfg into the grub 
> source?  Is there an official patch someplace? The random patches I keep 
> finding look to just be ripped from a few different variations of RHEL 
> based packages.

There was an attempt to get blscfg upstreamed into GRUB, but as far as
I can tell it got dropped[1] (but probably should not have been).

Glenn

[1] 
https://lore.kernel.org/grub-devel/CACF7NTiCzhRf5SwDs_KKD+Aix0LULEhsmzC1Tox4s7Dk0c2POQ@mail.gmail.com/