BOOTX64.CSV makes shimx64.edi my default bootloader

Asked by little noodles on 2018-10-11

My EFI dual-boot kubunutu 18.04 system was always able to boot either Kubuntu or Windows 7 - until a grub update on September 13, 2018. Sometime after that update, the grub boot menu could not launch Windows - and I had to redo my BIOS's EFI boot order in order to launch it. Ultimately, I noticed that EFI/ubuntu/BOOTX64.CSV pointed to shimx64.efi, and indeed EFI/Boot/bootx64.efi is a copy of EFI/ubuntu/shimx64.efi.

My system does not have secure boot (enabled or otherwise), so I have no need for a shim bootloader. I patched BOOTX64.CSV to point to grubx64.efi instead, and that got me back to being able to launch Windows from the grub menu. I don't remember whether I had to copy grubx64.efi to EFI/Boot - or whether the fallback loader just fixed things up for me.

In any case, I just got another grub update today (October 11, 2018), and once again BOOTX64.CSV pointed to shimx64.efi. I patched it again - and didn't copy grubx64.efi, but grub's working fine. So my question is, is BOOTX64.CSV *supposed* to always point to the shim bootloader - even on a system without secure boot? If so, then somewhere along the line, my system must've run the fallback boot loader, which then installed the shim. I didn't test booting today after receiving the grub update but before re-patching BOOTX64.CSV to point to the non-shim grub loader, so I don't know if the shim would've reinstalled itself if I didn't patch it (it's still in EFI/Boot). But I just want to make sure this is the normal way ubuntu installs EFI grub bootloaders (with the shim as the fallback, whether or not it's the normal bootloader) - or whether something has changed since my initial install?

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