Public bug reported: I recently swapped out my WUXGA monitor for a much bigger 4K monitor. Most unexpectedly, I found that this prevented my workstation from booting.
When I start up, I see the power-on splash screen from the workstation motherboard. I should next see the Grub menu, but instead I get a blank screen, and the boot-up hangs indefinitely. If I unplug my monitor for the first few seconds of a power-up, until the Grub menu has come and gone, I can re-plug the monitor and watch the rest of the boot-up into the initramfs and my system. If I use my old, small monitor, boot-up works. I solved the problem by using efibootmgr to change the boot loader from /EFI/ubuntu/shimx64.efi to /EFI/ubuntu/grubx64.efi. With this change, the system boots properly with the new monitor: I see power-on splash screen, Grub menu, initramfs messages, etc. For all the above, Secure Boot is enabled by my firmware. Another way I can fix the boot hang is to turn off Secure Boot. Then my workstation boots normally with shimx64.efi. (It is counter-intuitive to me that Shim is the boot loader blocked by Secure Boot, but that's what I observe.) To summarize: of the 3 variables I explored, the only combination that fails is Secure Boot, a 4K monitor, and shimx64.efi. It seems someone else had the same problem with a new monitor in 2016: https://ubuntuforums.org/showthread.php?t=2301071&page=37 I am running Ubuntu 18.04.4 ("Bionic"). My motherboard is an ASUS P10S WS, firmware version 3801. grubx64.efi is from grub-efi-amd64-signed version 1.93.16+2.02-2ubuntu8.15 shimx64.efi is from shim-signed version 1.37~18.04.3+15+1533136590.3beb971-0ubuntu1 I also have shim version 15+1533136590.3beb971-0ubuntu1 installed. I am happy to run experiments on my hardware for you. ** Affects: shim-signed (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1869120 Title: Shim bootloader hangs before Grub menu with 4K monitor To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/shim-signed/+bug/1869120/+subscriptions -- ubuntu-bugs mailing list email@example.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs