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I have searched a bit and have, so far, been unable to find an exact answer for this situation. I have 20.04 installed alongside windows 10, each on their own 1TB NVMe SSD cards, installed directly to their respective NVMe motherboard slots. The Ubuntu installation is using full disk encryption, mounted automatically by grub, which asks for a password during boot.

However, try as I might, I cannot access the normal GRUB 2 menu to either boot into the windows system or run a memtest, which i desperately need to do. When tapping ESC during boot, the system boot directly into the grub 2 command line. Holding or tapping shift does nothing during boot, only ESC works to bring up grub. From here, I can manually boot either system, but this really sucks, obviously.

I have tried entering normal at the prompt and hitting ENTER, but it just stays on the command line. Typing exit just brings up a black screen with the word GRUB and a blinking cursor which requires a reboot to escape from. I have run sudo update-grub from inside Ubuntu to no change at all. Commented out the GRUB_HIDDEN_TIMEOUT=0 line in /etc/default/grub, no change. Current Grub version is 2.x.x.

I am really pulling my hair out here, and would really appreciate any help that anyone can provide.

EDIT: For posterity, I have partially solved this issue, it was my own misunderstanding. here's how:

Follow the steps outlined in this answer. What I failed to understand is that you must run sudo update-grub after editing the file to submit the changes. After this, I was able to enter the grub menu every time without hitting anything during the BIOS screen. However, hitting ESC still spawns the command line only as outlined in my original question. SHIFT does nothing.

Now I say "partially" solved because GRUB does not list the windows OS at all, and I am also missing memtest options. Still working on fixing that.

  • Escape is for UEFI boot. You press it (timing an issue) after vendor's UEFI screen & before grub menu. May not work if UEFI fast boot is on, if rebooting (warm reboot). Shift is for BIOS boot. You hold shift from BIOS screen until grub menu appears. – oldfred Apr 05 '21 at 21:13
  • I know this is a few months old but... for the memtest stuff, my understanding is that you only get the memtest86+ option when booting in legacy BIOS mode (e.g. it does not appear in UEFI mode). If oldfred's comment above is saying that ESC only works in UEFI, then that's probably why its missing. If you need to boot to memtest86+, a workaround might be to enter your BIOS settings / boot menu, and boot off a liveusb/live-disc in non-UEFI mode, then you should get the option to use it in the livedisc's menu. alterately, there is the proprietary memtest86 (no plus) that works w UEFI. – zpangwin Sep 04 '21 at 17:13

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