GRUB2 Behavior Question

[Jordon Hofer]

I have a situation where a system is running Debian 8 (GRUB2.02~beta2-22) on 
btrfs.  I then switch to a snapshot running Debian 10.3 (GRUB2.02+dfsg1-20) and 
run grub-install and update-grub before rebooting - it boots 10.3 just fine.  
When I switch back to the Deb8 snapshot, grub cannot find the kernel because it 
is still looking for the Deb10 kernel (4.19.0-8) instead of the Deb8 one 
(3.16.0-6).  But, when switching back to Deb8, if I run the 
grub-install/upgrade-grub commands before rebooting (after properly 
mount--binding and chrooting), it boots Deb8 just fine.



I was under the impression that the Stage 2 loader read /boot/grub/grub.cfg to 
see what kernel to load.  Each snapshot has /boot/grub/grub.cfg in a properly 
symlinked location, so it should 'just work'.  Does the Stage 2 loader have 
some sort of caching that is causing it to not read the grub.cfg when I switch 
snapshots and reboot?


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