[CentOS] 8.2.2004 Latest yum update renders machine unbootable

Sat Aug 1 15:20:31 UTC 2020
Lamar Owen <lowen at pari.edu>

On 7/31/20 6:35 AM, Alan McRae via CentOS wrote:
> I am running an Intel x64 machine using UEFI to boot an SSD.
> Installing the latest yum update which includes grub2 and kernel 
> 4.18.0-193.14.2.el8_2.x86_64 renders the machine unbootable, blank 
> screen where grub should be, no error messages, just hangs.
> ...
> The main point of this message is to make people aware of the problem 
> and suggest admins don't run 'yum update' until they understand the 
> problem and have a fix at hand. 

I posted, on 7/30, to CentOS-devel the following after my similar 
experience (booting an mSATA SSD on my M6700, with two 2.5 SATA drives 
(a 1TB and a 2TB), and the mSATA is not /dev/sda on this hardware, FWIW):

"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....."

I was able to recover with the install DVD on a USB stick and using 
rescue mode on a laptop with only WiFi (nmtui does a great job for this 
sort of thing, booted into rescue mode and chrooted onto /mnt/sysimage).