[Comm-en] Recover missing boot option in GRUB after upgrade

[Michael Shigorin]

On Sun, Jan 28, 2024 at 11:11:35PM -0600, TheGrove wrote:
> Although my main objective was to upgrade to p10, I would still like to
> experiment with Sisyphus from time to time.  Is there an easy way for me
> to recover the option in GRUB to boot into Sisyphus on /dev/sda5?

I'm not a GRUB expert (having not maintained it for many years
and never having really loved it), but:

1) is os-prober package installed on "stable" system"?
   (it *might* be related to non-Linux OS detection in dual-boot,
   in which case I'd dig for some discussions on "grub multiboot"
   or "grub dual-root" maybe)

2) there's a Russian ALT wiki page on the topic:
   http://altlinux.org/Grub#Как_установить/восстановить_загрузочную_запись_grub?
   
   "mount-system" is ALT Rescue specific script that
   basically finds a probable rootfs, mounts it as
   /mnt/system1 and bind-mounts the virtual FSes there:

   for i in proc sys dev; do mount --bind $i /mnt/system1/$i; done
   
   -- this can perfectly be done by hand from an already running
   system, of course :-) -- but the recipe results in *that* copy
   of grub installing its boot record/files/configs, potentially
   ignoring the other systems like what you observe currently.

If these don't help, well, let's think on.

PS: do backup *both* of your /boot directories just in case,
even if it's a simple "cp -a /boot /root".

-- 
Michael Shigorin
http://altlinux.org/elbrus