I was upgrading on command line from 18.04 to 18.10 and was shown that grub differences interactive prompt and hit D to show differences (which I typically never do). After the differences were shown, I wanted to return back or just to continue. Screen did not show how to so I hit Esc. Nothing happened then, so I hit CtrlC and it broke out of upgrade and was shown terminal prompt.
I ran the reboot command in the terminal, but it did nothing which was very strange. I tried to reboot using desktop top right system menu UI and was shown in tiny font something about a file needed setuid permission which I ignored thinking system would handle fixing that itself. Evidently it did not. I rebooted by long-pressing the power button.
Now boot up fails to complete, only shows black screen and I cannot reach grub menu, by tapping Shift on boot, with the desire to see recovery grub menu where I could fix this myself from root prompt.
staring at blank black screen
I have no problem reformatting and reinstalling from scratch however this is yet another edge case which would scare off newbees from sticking with linux. As an organization Ubuntu needs to shift priorities to make such meltdowns more self healing.
Any suggestions? This is not a dual-boot, there's only one OS on box.
I tried booting from LiveUSB and running boot-repair to reinstall grub2. No, boot-repair errors showing internal system error occurred and when I hit show details it hung forever. I rebooted then ran liveUSB boot-repair a few times, same. I'm throwing in the towel on boot-repair as it just hangs 20 mins each time. reformatting and starting over from scratch