I have an Acer Aspire E5-511 laptop. I am trying to install Ubuntu or Kubuntu, but after I do the updates it won't boot. It boots to a black screen with this message and the fan make noise:

[    2.448950] Problem loading UEFI: db X.509 certificate (-65)  
[    2.449012] Problem loading UEFI: db X.509 certificate (-65)  
[    2.449111] Couldn't get size: 0x8000000000000000e

I had the same issue when trying to install Ubuntu 20.04, and it seems to have happened because Secure Boot was enabled during installation.

So the newly created .efi file had to be added as trusted in BIOS.

Got the solution from here on it's FOSS.


Problem is with your secure boot.Restart your system and enter BIOS mode and then disable secure boot.

To do so you can follow How to disable Secure Boot in BIOS?

  • 2
    secure boot is disabled Dec 30 '18 at 12:27
  • Disabling secure boot didn't resolve the issue. Any other suggestions ?
    – Mayank
    Oct 22 '19 at 5:36

In legacy BIOS compatibility mode the UEFI firmware functions as a standard BIOS instead of UEFI firmware, which improves compatibility with operating systems that weren't designed with UEFI in mind.

Enter the BIOS/UEFI setup utility when the computer is starting, disable Secure Boot, and enable Legacy/CSM boot mode.

enter image description here
disable Secure Boot

enter image description here
enable Legacy/CSM boot mode


  • 3
    There is only "UEFI" option in Aspire ES1-533
    – Ikrom
    May 9 '19 at 5:09

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