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I am running Windows 10, Ubuntu 20.04.2 dual boot on a Lenovo Thinkpad. The setup has been working fine for me for 6+ months.

The laptop was on with the lid closed and the charging cable got disconnected, and it died. Now when I turn it on it loads grub but if I try to boot Ubuntu it goes to a black screen showing a blinking cursor, exactly like in this question. I can still boot the Windows partition without a problem.

What I've tried:

Apparently a common cause for this is an update/install gone wrong. From grub I can boot Ubuntu in recovery mode where I ran the dpkg tool to repair any potentially broken packages but that turned up nothing, and with the lid closed long before it powered off there shouldn't have been any chance of something critical being interrupted.

A couple other common causes are lack of space (my Ubuntu partition has >80% free) and Nvidia graphics driver issues (I use intel integrated graphics).

I can access the virtual console with Ctrl+Alt+F3 where I tried the suggestions from the linked question (sudo dpkg-reconfigure gdm3, sudo service gdm3 restart, and editing /etc/gdm3/custom.conf and unmcommenting #WaylandEnable=false). None of these had any effect.

This question gives a lot of resources but none seem to apply to me. Grub seems to be working fine and I'm a bit nervous to touch it without knowing what I'm doing, since I don't want to mess up my Windows partition (but if others think it sounds grub related I will try updating/reinstalling grub).

I wanted to try fsck so I made a bootable USB with the latest Ubuntu image and discovered something else: my laptop won't boot from USB now (it did before, that's how I did the initial install). I can boot from the USB on another Lenovo laptop but this one hangs on the splash screen as if it detects the USB is bootable but is unable to boot from it. I disabled secure boot, played with UEFI/Legacy boot options and boot order but it won't work. As soon as I unplug the USB it continues to grub.

If I can't boot from USB I can't even reinstall (at least not without a lot of pain) but I'm not sure what else to try.

update:

the USB issue was fixed by changing the USB device. I was able to run fsck from a live cd which found no issues, even with the -f (force) option.

I also tried running the boot-repair tool which reinstalled grub as well but had no effect.

wyoumans
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  • Try booting in windows and then shutdown the machine. Not restart, and then press the power button and boot into Ubuntu. I had the same issue I can't exactly remember how I fixed it but I remember shutting down and restarting. – Mahir Nov 04 '21 at 22:02
  • That didn't have any effect @Mahir – wyoumans Nov 04 '21 at 22:13
  • Did you tried all of the answers from this post? https://askubuntu.com/questions/297080/ubuntu-open-to-black-screen-with-blinking-underscore-character-after-release-upg – Mahir Nov 04 '21 at 22:17
  • Yes, all of the suggestions not involving lightdm since that's outdated (it's gdm now). See the third paragraph of my question under "What I've tried" to see exactly what I did try. @Mahir – wyoumans Nov 04 '21 at 22:21
  • Okay, Your question is so much detailed but I had to ask if you can see the Ubuntu logo and the loading animation while booting into Ubuntu. In this case does the problem (blinking cursor) comes after the loading or the cursor comes straight up after the grub boot loader loads the Ubuntu. – Mahir Nov 04 '21 at 22:53
  • It does quickly show a purple screen with the Ubuntu logo and dots as if it's loading, then flashes a black screen that says "recovering journal". Then it goes to the blinking cursor. @Mahir – wyoumans Nov 04 '21 at 23:36
  • HELLO @wyoumans. Did you check if something changed on bios after that? I am thinking "secure boot went to enabled" as you mention you cannot boot from usb anymore. – jpbrain Nov 05 '21 at 03:18
  • Secure boot is definitely off, I checked multiple times while trying to boot from USB @jpbrain – wyoumans Nov 05 '21 at 04:09
  • Did you try the classic sudo apt install -f? – Pablo Bianchi Nov 06 '21 at 19:24
  • What do you mean? @PabloBianchi – wyoumans Nov 06 '21 at 20:50

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