I have upgraded from 32 bit Fedora 28 to 30 using dnf system-upgrade, exactly as found in the Fedora documents. All was OK, up to dnf system-upgrade reboot. The started system has upgraded the packages, with cleanup and verify. After numerous hours, the system has restarted but grub cannot boot and it enters the grub command mode.
Using CD rescue disk, I have verified the hard disk and every partition on it using fdisk an fsck. Not problem encountered. I have verified in /boot/ and I have found vmlinuz and initramfs having the expected endings and a size which looks OK.
But /boot/grub2/grub.cfg is strange and very different from the usual structure.
I have booted from the grub command line using configfile /grub2/grub.cfg.rpmsave and I was able to boot as under Fedora 28. I have tried to generate a tentative grub.cfg using grub2-mkconfig and I have put it in /tmp/ in order to compare it with /boot/grub2/grub.cfg. The result: It is exactly the same.
What can I do in order to make the system running well as Fedora 30 as expected ?
Is it a good idea to run dnf update while running this old kernel 28 ?