Search:

Have you tried do-release-upgrade in a terminal window?
I'm not running 18.10, my latest machines are 18.04 LTS
The message suggests that there should be a file or directory named /etc/default/rc5....

If grub shows alternate kernels try them and see if they boot, then run fsck from there.

I discovered recently that do-release-upgrade does not require a sudo . It will download the upgrade software then prompt for authorization. I'm not sure whether it's always been that way.

I discovered recently that do-release-upgrade does not require a sudo. It will download the upgrade software then prompt for authorization. I'm not sure whether it's always been that way.

Are you saying that grub does not give you a choice to boot into 18.10 or other options? Or does it offer that choice then drop you into a shell of some sort?

I have found doing release upgraded...

Just to agree I would not upgrade to 18.10 without some compelling reason. I'd wait for 20.04 at least.
I wouldn't even attempt an upgrade unless everything was working as expected.
I don't...