Cannot Boot After Doing system-upgrade

[Garry T. Williams]

I recently did this on an up-to-date F28 system:

    $ sudo dnf system-upgrade download --refresh \
	--releasever=29 --allowerasing --best
    $ sudo dnf system-upgrade reboot

Now system will not boot.

I had to boot from a live usb stick and do:

    $ sudo su -
    # vgdisplay
    # vgchange -ay fedora
    # mount /dev/fedora/root /mnt
    # mount /dev/sdb2 /mnt/boot
    # mount /dev/sdb1 /mnt/boot/efi
    # mount --bind /proc /mnt/proc
    # mount --bind /tmp /mnt/tmp
    # chroot /mnt
    # dnf --disablerepo=updates-testing upgrade grub2-efi shim

None of this was obvious to me at first.  I got here only after a lot
of searching the Web for answers.  It seems that grub2-install won't
work on my setup, even after disabling secure boot on this machine.

What am I doing wrong here that I cannot boot after a system-upgrade?

    $ df -h
    Filesystem               Size  Used Avail Use% Mounted on
    devtmpfs                 7.8G     0  7.8G   0% /dev
    tmpfs                    7.8G   91M  7.7G   2% /dev/shm
    tmpfs                    7.8G  1.2M  7.8G   1% /run
    tmpfs                    7.8G     0  7.8G   0% /sys/fs/cgroup
    /dev/mapper/fedora-root   50G   11G   36G  24% /
    tmpfs                    7.8G   64K  7.8G   1% /tmp
    /dev/sdb2                976M  287M  623M  32% /boot
    /dev/sdb1                200M  7.9M  192M   4% /boot/efi
    /dev/mapper/fedora-home  412G   12G  379G   3% /home
    tmpfs                    1.6G   44K  1.6G   1% /run/user/1000

-- 
Garry T. Williams