Centos 8 elrepo Kernel-ML boot issue - grub error

[sandeep]

When using elrepo kernel-ml in centos 8 you might experience grub is failing and centos 8 is failed to boot. With below message :

error: file '/boot/grub/grubenv' not found.
error: file '/boot/grub/i386-pc/increment.mod' not found.
error: file '/boot/grub/grubenv' not found.

if grub is failing and centos 8 failed to boot do this steps:

boot into rescue mode mount centos disk :

then you need to change the line in /etc/default/grub by editing the file :
GRUB_ENABLE_BLSCFG=true to GRUB_ENABLE_BLSCFG=false

then rebuild grub :

grub2-mkconfig -o /boot/grub2/grub.cfg

example :
[root@test ~]# cat /etc/default/grub
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="crashkernel=auto biosdevname=0 net.ifnames=0 rhgb quiet"
GRUB_DISABLE_RECOVERY="true"
GRUB_ENABLE_BLSCFG=true
GRUB_DISABLE_UUID=true
GRUB_DISABLE_LINUX_UUID=true
/etc/default/grub

[root@test ~]# cat /etc/default/grub
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="crashkernel=auto biosdevname=0 net.ifnames=0 rhgb quiet"
GRUB_DISABLE_RECOVERY="true"
GRUB_ENABLE_BLSCFG=false
GRUB_DISABLE_UUID=true
GRUB_DISABLE_LINUX_UUID=true

Best to run after dnf update/yum update :

sed -i 's/GRUB_ENABLE_BLSCFG.*/GRUB_ENABLE_BLSCFG=false/' /etc/default/grub
grub2-mkconfig -o /boot/grub2/grub.cfg