[CentOS-devel] recent updates cause grub not to load please advise

On 7/30/20 6:54 AM, Andy Hall wrote:
> seems the updated pushed recently to centos stream (I updated about an 
> hour ago) now cause my pc to hang after BIOS...it never gets to grub 
This affected me this morning on my regular, non-Stream, CentOS 8.2.2004 
install.  Boot up, see the update notice, think "hmm, I have plenty of 
time before that morning meeting, sure, why not do this update, must be 
the 'Boot Hole' update Johnny mentioned." After the update, on reboot 
the screen kept the Dell meatball in the middle but then had 'hash' 
marks all over the screen.  Neither a regular power button press nor 
CTRL-ALT-DEL did anything, had to hard power off by holding the power 
button down until it powered off.  Yay, fun, let's reschedule that 
morning meeting, guys, my computer is acting up right now..... In my 
case, the instructions for downgrading in the referenced Bugzilla did 
not work to restore normal booting.

The use of the install DVD iso's rescue mode was required; once booted 
into rescue mode (on my Dell Precision M6700 laptop, pressing F12 during 
boot to get the boot menu, then selecting the USB stick in UEFI mode, 
since my machine is a UEFI-booting machine, and after chrooting to 
/mnt/sysimage, I performed the downgrade, but on reboot the system still 
hung completely.  So, rebooting back into rescue mode, chroot 
/mnt/sysimage, nmtui (and activate the network interface I needed, since 
it's wifi), and then running the grub2-install I got an error; needed to 
install grub2-efi-x64-modules to run grub2-install.  But a bare 
grub2-install did not fix the problem for me; so, reboot into rescue 
mode again, chroot /mnt/sysimage again, and then run the recommended 
UEFI grub2 reinstall procedure (linked from 
https://bugzilla.redhat.com/show_bug.cgi?id=1101352 pointing to 
https://bugzilla.redhat.com/show_bug.cgi?id=1220066 ):

dnf reinstall grub2-efi shim grub2-tools

And I'm now rebooting correctly, after a complete system 
autorelabel......  This may or may not work for you, since I did several 
steps and reboots, so I don't know what actually 'fixed' the booting, 
nor do I have time today to try to reproduce.  I do now know to be extra 
careful on my other UEFI C8 systems, and I won't be doing any remote 
updates on those, only from the console, with bootable media at hand.... 
argh.

Moral of the story?  Have the install DVD on a USB stick and available 
to boot into rescue mode, know how to boot rescue mode (from the 
installer boot menu select 'troubleshooting....' then 'rescue....' and 
option 1 once the menu shows), know how to activate network interfaces 
in text mode (either nmcli or nmtui works fine for this), and know a few 
basic dnf commands.  And have an alternate means of doing basic web 
searches available; my android phone this morning was used for that.....

However, what is really odd to me is that after the dnf downgrade of 
grub2 and shim, which did get logged in /var/log/dnf.log, when issuing a 
dnf update I don't see the grub2 and shim updates listed anymore.  And, 
where the blue blazes is the log of updates done from the GUI updater?  
Went to look for it to back out whatever got updated, and in my cursory 
booted-into-the-chroot-via-rescue-mode-tiny-text-screen state quit 
looking for it; I may try to find it later today.