Re: How to reinstall the bootloader without guix system reconfigure?

[Felix Lechner via "Development of GNU Guix and the GNU System distribution." <guix-devel@gnu.org>]

Hi Akib,

On Fri, Jul 1, 2022 at 4:35 AM Akib Azmain Turja <akib@disroot.org> wrote:
>
> Fortunately, I have Ubuntu (yet another nonfree
> distribution) installed and it didn't broke, so used that to add that
> 100 GB to my Guix partition.  But I found that GRUB is still broken.
> Then I appended "/boot/grub/grub.cfg" of Guix to the same file of Ubuntu
> and managed to boot into Guix

Like Tobias, I cannot tell how Grub broke for you (although I do not
dispute that it did).

Grub needs to find a series of secondary files that, for EFI, are
stored on the ESP. [1] For a traditional MBR/BIOS install, people use
a small (1 MB or so) "BIOS Boot Partition" [2] although you probably
aren't using that because your Windoze would not be able to use GPT
without EFI. (Without GPT, Grub finds some place outside the partition
table.)

I think you are using EFI and an ESP.

You may be encountering the issue that both Ubuntu and Guix are trying
to manage the boot process. There is theoretically a way both Grub
installations could coexist on the ESP but I am not sure they do. I
personally would run Grub only in Ubuntu or Guix.

In your case. it may be hard to pick one over the other.

Ubuntu scans your hard drive for other operating systems, including
Winblows, but probably misses Guix. Guix on the other hand may
miss the other two but knows the exact paths needed to boot into your
most recent "Guix System" configuration.

> Is there any way to reinstall bootloader without the costly "guix system
> reconfigure"?

To reinstall in Guix, you may be able to run 'grub-install /dev/sdX'
but that does not stop the competition between Ubuntu and Guix. I may
also make it harder for you to boot into Ubuntu or Winnows.

> Another non-important question:  Why did Guix's GRUB broke while
> Ubuntu's GRUB survived?

I think they use the same folder on the ESP.

Maybe there is an expert who can chime in.

Thanks for using Guix!

Kind regards,
Felix Lechner

P.S. You can boot many systems manually from the Grub shell, but it
would be an extraordinary burden to type the full Guix paths for your
kernel and your initrd.

[1] https://en.wikipedia.org/wiki/EFI_system_partition
[2] https://en.wikipedia.org/wiki/BIOS_boot_partition