Roger Heflin writes:
What you are saying does not exactly match what I have previously
seen, but there is a known feature with using a journaling filesystem
(ext4-journal, or xfs) for /boot, if only the journal is updated and
if it is not yet replayed into the non-journal then grub will not be
able to find the new files/updated files (grub filesystem code is
simple and does not process the journal so if critical updates are
still in the journal then those updates(changed file, new files)
cannot be seen). To get this one generally has to do the update and
almost immediately reboot (within a few minutes though in some cases,
note syncing the does not replay the journal).
I have used ext4 for /boot for 20+ years on Fedora, and can't say that I
ever had this happen. And I always reboot after installing updates.
Long term the solution is to move boot to a non-journaled fs (ext
without a journal) or after each update umount/mount /boot(before
reboot)..
I would be very much surprised if a regular reboot does not unmount /boot,
prior to rebooting. I would think that all mounted filesystems except / will
get explicitly unmounted just before a halt or a reboot.