[SOLVED] Kubuntu 20.04 on laptop no longer boots - UEFI problem?

[RichardR]

Hello,
Some months ago, I installed Kubuntu 20.04 on a 4-year old Acer Aspire 5 laptop (A515-51-50XU), and things worked OK - until yesterday that is.
The machine's battery was empty, and it powered off while in use.
So the owner hooked up the charger, but now it won't boot any more. After the GRUB start screen, I briefly see Kubuntu's HD check message, and then things are stuck with this screen:

[   0.110148] x86/cpu: SGX disabled by BIOS
[   0.362219] ACPI Error (bug): Could not resolve symbol [\_PR.PR00._CPC],
AE_NOT_FOUND (20210730/psargs-330)
[   0.362243] ACPI Error: Aborting method \_PRPR01._CPC due to previous error
AE_NOT_FOUND (20210730/psargs-529)
[   0.362332] ACPI Error (bug): Could not resolve symbol [\_PR.PR00._CPC],
AE_NOT_FOUND (20210730/psargs-330)
[   0.362350] ACPI Error: Aborting method \_PRPR02._CPC due to previous error
AE_NOT_FOUND (20210730/psargs-529)
​[   0.362528] ACPI Error (bug): Could not resolve symbol [\_PR.PR00._CPC],
AE_NOT_FOUND (20210730/psargs-330)
[   0.362545] ACPI Error: Aborting method \_PRPR03._CPC due to previous error
AE_NOT_FOUND (20210730/psargs-529)​
[   0.619866] integrity: Problem loading X.509 certificate -65
[   0.619888] integrity: Problem loading X.509 certificate -65
You are in emergency mode. After logging in, type "journalctl -xb" to view
system logs, "systemctl reboot" to reboot, "systemctl default" or "exit"
to boot into default mode.
Press Enter for maintenance
(or press Ctrl+D to continue):

The ACPI errors were present already (no idea what causes these), but they didn't cause the machine to hang.
This X.509 problem is new; it seems to be related to UEFI secure boot, but I don't understand why this fails all of a sudden.

Is there any way to fix this problem without a complete reinstall? I tried the above commands, and I also tried loading the BIOS defaults, but to no avail.

Thanks for any hints.

[claydoh]

It could be something related to the battery drain, possibly. I have seen stranger things happen on laptops when the battery is drained completely.
Have you tried disabling Secure boot in the bios settings?
One possible thing that is a quick thing to try, is making sure the Bios date and time are set manually to the correct date. This may have been lost, especially if the CMOS battery is also bad. That might make the security certs for secure boot
invalid due to the mismatched dates.

[RichardR]

I tried the following:

• Change BIOS boot mode from UEFI to Legacy -> can't boot at all, "No bootable device"
• Check BIOS time and date: these are correct
• Load BIOS defaults -> no change
• Boot Linux from USB thumb drive and check integrity of HD Linux partitions with badblocks / fsck -> zero errors

So I'm pretty much stuck, and I'm thinking about a complete reinstall. The problem is that I don't know what caused this, so I can't guarantee that this won't happen again - and the owner is a bit miffed already as it is ...

Anyway, thanks for your suggestion.

[claydoh]

But have you tried disabling secure boot, as I suggested? At least to see if Linux boots? Windows 10 if present does not require it.

[RichardR]

But have you tried disabling secure boot

Secure boot can't be disabled. The BIOS option 'Secure Boot' is greyed out, and set to 'Enabled'. No passwords (Supervisor, User, HDD) are set, so that can't be the problem.
There are in fact several BIOS settings that can't be accessed, most of which have to do with Secure Boot mode and TPM (which is also installed and enabled).

Maybe relevant: it is a dual-boot machine with Windows installed as well (don't know which version, maybe W10), and that boots OK.

Update: I managed to disable secure boot (needed to set Supervisor password first).
Result: no change, still won't boot past the X.509 certificate error. Disabling TPM does not help either.

[claydoh]

You may need to refer to device specific documentation.
I would guess that having TPM enabled (not a requirement) would enforce Secure boot, and may be a BIOS default setting (which I have seen differ from what actually ships, though that was only once)
You could try turning off TPM, and then seeing if that allows you to turn off Secure Boot

You are in emergency mode. After logging in, type "journalctl -xb" to view
system logs,​

Did you happen to do this step, and look for the actual full error messaging? it is entirely possible that the cert errors you see on the screen could be unrelated to your problem altogether, so it may be worth a peek, and some photos if possible. ( you probably need to scroll down with the arrow key to get to the end, where things went kaboom)

[RichardR]

Did you happen to do this step, and look for the actual full error messaging?

Ah, that's a good one ... checking ... yes, Kubuntu's file system check did throw an error message somewhere near the end - but not for the Linux system and home partitions (the ones checked previously), but for a separate partition I created for back-ups. Fixed the errors, made a new, full backup, and we're up and running again!

Too bad that Kubuntu did not actually show the relevant error message - and I still see the X.509 errors, so those weren't the cause of the boot problem.

Anyway, thanks for the heads-up!