Upgrade Centos 7 host to Centos 8, now wont boot

hi all,
upgraded a centos 7.5 host to 7.7, which worked well. After that, then did the Centos migration from the OS level from 7.7 to Centos 8.
Unfortunately now getting a GRUB boot error, in Glish console:
"error: variable 'prefix' isn't set. "

I can boot via the linode rescue disk.
Have looked at https://www.linode.com/community/questions/19397/i-just-upgraded-my-centos-8-linode-and-now-it-wont-boot-how-do-i-fix-this-proble, and set the rescue.conf as describe.

No luck, still can not boot to Centos 8. Worked great in Centos 7.7.

Any suggestions or ideas?

thanks -b.

1 Reply

With the error you're getting, error: variable 'prefix' isn't set., there are a couple of things you can try that I've seen work before.

One of the first things I'd recommend doing is upgrading your kernel:

Update your Distribution-Supplied Kernel

You could also try switching to Linode's kernel, for which we also have a guide:

How to Change Your Linode's Kernel

I also found this article online that might be of assistance as well:

GRUB only offers a rescue shell

These are all just suggestions, because I don't have access to your Linode's internal configurations. That said, I had another thought - when you did the upgrade to CentOS 8, was it an inline upgrade? This is when you install a new version of an OS without removing the old one first.

The reason I bring it up is because I've seen inline upgrades cause issues before. If that's the case here, you might want to create a new Linode with a CentOS 8 distro and move your data over using a utility like scp or rsync.

To access that data, I would recommend you restore it from a Backup (if you have one) and move it over from that restore.

Restore from a Backup


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