Hi list, After a recent upgrade I noticed that my system could not reboot into the new 4.19 kernel. So I rebooted into the kernel before that (4.18.0-3), which did not work either. Booting into the version before that (4.18.-02) did work just fine.
It seems I hadn't rebooted after the previous upgrade, causing me to have 2 versions that do not work for my system without noticing. (I do not regularly reboot.) After rebooting the failing kernels show a lot of errors about not being able to find processor IDs and after that they stop with the message that they can't find the encrypted device containing / (actually everything apart from /boot). Sorry, I haven't captured the exact error messages, so I can't show the full text of them. So how do I make sure that 4.18.0-2 does not get removed from the boot menu after the next kernel upgrade? I'd like to keep it until I have verified that an upgrade does work. However, as far as I can tell only the last 3 kernels are kept. Thus now I run the risk of having the only working version removed before I am sure that a new version will work. A perusal of the Grub2 documentation did not give me a pointer on how to do this. Nor did I find a setting for this in /etc/default/grub or /etc/grub.d/. As a matter of fact I am not even sure grub is the proper place for this. Grub only builds a boot menu, but it does not remove kernels (as far as I am aware). Any pointers in the right direction will be appreciated! Grx HdV