SSD in new device: will not boot, boot repair fails

[jamespetts]

The BIOS/Legacy/CSM mode does not have the UEFI tools.
Did you turn on legacy boot in UEFI. Or some setting on USB ports and how they boot?

When I do not turn legacy boot on, it refuses to boot with the USB drive.

When I do turn legacy boot on, it will boot into Ubuntu from the USB drive, but the UEFI tools will not work.

This behaviour is different from what it was earlier in the day yesterday, when I could boot from the USB drive with legacy boot disabled, and I do not understand why: the change in behaviour appears to have occurred without any intervention or discernible change in settings.

[oldfred]

What boot options do you have with legacy off.
Is UEFI Secure boot on?

[jamespetts]

No, secure boot is off.

Apologies for the multiple postings above, incidentally: I was having trouble posting for some reason and the new posts were not showing up.

[oldfred]

Forum has ghosts, they sometimes interfere and other times are asleep & forum works fine.

Not sure what else to suggest.
Some have had issues and just created new flash drive.

Do you still have UEFI boot menu for internal drive, even if none of entries work?

[jamespetts]

Do you mean in the BIOS? The SSD does indeed show in the BIOS as having a bootloader: it just does not work when I try to use it.

Edit: Testing this again, the behaviour now of the USB drive when I have UEFI enabled is identical to that of the SSD: both the BIOS menu and the F10 boot menu recognise both devices as having bootloaders, yet attempting to boot from them fails with the "no bootable device detected" error message.

[oldfred]

That is typical of Secure boot on, or UEFI entries not being valid.
Perhaps your system only works with the "Windows Boot Manager" entry? Which most do not require, but some do. But those are mostly systems sold with Windows pre-installed.

[jamespetts]

Secure boot is definitely not on. What might cause the UEFI entries not to be valid; might it have happened that the USB drive's UEFI entry was corrupted by having run the commands above; would it be worthwhile re-flashing the USB drive? What might have caused the SSD's UEFI entry to be invalid, do you think?

[oldfred]

Not that familar with NUC, but it still should always boot flash drive, as long as you have UEFI set to allow UEFI boot.

It may be worth while to create new flash flash drive. Not sure how it could have gotten corrupted.

Have you tried a cold boot?
Sometimes that resets UEFI.
If fast boot is on in UEFI, it assumes you have no hardware nor configuration changes and default boots to old configuration.
Best to have fast boot off in UEFI.

My desktop allows on/off & and delay setting on UEFI boot, so when installing I have it off as a lot of settings & configurations change.
But once mostly configured I change to allow a 3 sec delay, but not full fast boot, as I may want to get into UEFI.
I also have a setting that allows standard boot from power off, so could also use that. But if that was fast boot, I might not ever be able to get into a misconfigured system, without opening case & jumpering pins to reset.

[jamespetts]

Thank you for your reply. I do not have fast boot enabled in the BIOS. I have tried many attempts at cold boots, without any differences in behaviour from that described above. I will try again with a newly flashed USB drive and see whether I can boot into the USB drive using UEFI so that I can have another go at using the suggested tools.

[jamespetts]

I have just re-flashed the USB drive, and it now works in UEFI mode again - something must have corrupted the UEFI bootloader on the USB drive somehow. Very odd.

Edit: I have tried again to go through the steps set out in your original post (although I am not as clear as I might be about precisely what is required), but I am afraid that it does not help: on booting without the USB drive inserted, I still get a "no bootable drives detected" error message. Using the F10 boot menu, it claims to have a UEFI bootloader from the SSD, but selecting it has no effect: the screen flickers for a fraction of a second and then returns to the menu.