Sorry I don't understand what you mean. The pre-existing GRUB is on /dev/sda4 and was working perfectly prior to MX KDE install. I install OSs regularly and just boot to Buster on sda4 and run update-grub to include a new one in the boot menu. If I deselect "Install GRUB", the installer should not touch the ESP or NVRAM table. It obviously did as reboot brought up a GRUB prompt, not its usual boot screen.fehlix wrote: Tue Jul 07, 2020 8:48 amOn UEFI, GRUB comes within different players. Taking out for now secureboot's shim. The first would be the grubx64.efi GRUB loader, which is placed with a subdir on the ESP. This grubx64.efi would be register with the UEFI firmware's NVRAM-table as a valid or the first to choosen bootloader.sunrat wrote: Tue Jul 07, 2020 8:39 amThanks for looking. Almost at the end of the installation routine I recall text displaying "Installing GRUB" even though I unchecked the install GRUB box. It wasn't installed, but wiped out the existing GRUB.
The grubx64-efi will load the remaining "grub-stuff" and the menu from the /boot folder on the /root (or boot partition,
What could have happed, is this: You'r default grubx64.efi was loading from /dev/sda7 and displays a nice grub menu.
When you now wipe out and reinstall on /dev/sda7 , the existing grubx64.efi loaded at boot, cannot find any grub-stuff on the new install on /dev/sda7.
You propaby just need to choose another valid grub-efi loader with the NVRAM table to get loaded.
Either by using efibootmgr or select at start up (by pressing e.g F12) another loader.
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I did fix it by booting into Buster from a REFInd flash key and reinstalling GRUB from there, but it shouldn't have been broken in the first place.