I finished upgrading my Desktop PC from 24.04.x to 26.94 with sudo do-release-upgrade
There were no errors during the upgrade. Upon rebooting and selecting the top entry in the Grub menu, I got the error message "error: prohibited by secure boot policy. Press any key to continue..."
Pressing any key (or just waiting for a few seconds) and the boot process proceeds and I am presented with the login greeter. Enter my pwd and I'm on the 26.04 Desktop. Everything works.
So I googled on:
after upgrade to Kubuntu 26.04 from 24.04, upon rebooting and selecting the first entry in Grub, I see error: prohibited by secure boot policy. Press any key to continue...
The AI answer:
AI Overview
This error occurs when your UEFI Secure Boot blocks an unsigned GRUB module or file from loading during the boot process. To fix it, temporarily disable Secure Boot in your BIOS/UEFI settings, boot into Kubuntu, update and reinstall the signed bootloader packages, and then re-enable Secure Boot.
Fixing the Secure Boot Policy Error
So I followed the steps shown above. With secure boot disabled, booting happens without this error. I then reinstalled the grub-efi-amd64-signed and shim-signed packages. Rebooted and entered the BIOS/UEFI settings and enabled secure boot, saved, and exited.
At the grub menu I selected the top entry in the Grub menu and was again presented with the error message.
This niggle didn't exist in 24.04. So how do I actually 'fix' it now that I'm running 26.04?
There were no errors during the upgrade. Upon rebooting and selecting the top entry in the Grub menu, I got the error message "error: prohibited by secure boot policy. Press any key to continue..."
Pressing any key (or just waiting for a few seconds) and the boot process proceeds and I am presented with the login greeter. Enter my pwd and I'm on the 26.04 Desktop. Everything works.
So I googled on:
after upgrade to Kubuntu 26.04 from 24.04, upon rebooting and selecting the first entry in Grub, I see error: prohibited by secure boot policy. Press any key to continue...
The AI answer:
AI Overview
This error occurs when your UEFI Secure Boot blocks an unsigned GRUB module or file from loading during the boot process. To fix it, temporarily disable Secure Boot in your BIOS/UEFI settings, boot into Kubuntu, update and reinstall the signed bootloader packages, and then re-enable Secure Boot.
Fixing the Secure Boot Policy Error
- Disable Secure Boot: Restart your computer, enter your BIOS/UEFI settings (by pressing F2, F12, or Del depending on your system), locate the Secure Boot option under the Security or Boot tab, and turn it Off. Save changes and reboot into Kubuntu.
- Update Package Files: Open your terminal and update your package lists and signed shim/grub components by running:
sudo apt update sudo apt install --reinstall grub-efi-amd64-signed shim-signed - Reinstall GRUB: Reinitialize the bootloader to match your system EFI partition:
sudo grub-install sudo update-grub - Re-enable Secure Boot: Reboot your computer back into your BIOS/UEFI settings, turn Secure Boot back On, save your changes, and start your system normally.
So I followed the steps shown above. With secure boot disabled, booting happens without this error. I then reinstalled the grub-efi-amd64-signed and shim-signed packages. Rebooted and entered the BIOS/UEFI settings and enabled secure boot, saved, and exited.
At the grub menu I selected the top entry in the Grub menu and was again presented with the error message.
This niggle didn't exist in 24.04. So how do I actually 'fix' it now that I'm running 26.04?