Hi, i managed to build a live-build ISO. Its /boot/grub/efi.img contains /efi/boot/bootia32.efi /efi/boot/bootx64.efi which both show by "strings" the embedded configuration with search --file --set=root /.disk/info The ISO 9660 filesystem contains a file /.disk/info
So the riddle is why this does not get into effect with that particular EFI implementation, and why a grub.cfg in the EFI System Partition solves the problem. Does a debian-cd ISO boot properly on that EFI ? E.g. https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-9.4.0-amd64-netinst.iso I meanwhile found out that the efi.img of debian-cd stems from debian-cd_info.tar.gz created by https://anonscm.debian.org/git/d-i/debian-installer.git/tree/build/util/efi-image and that its grub-mkimage run needs no -c option because it has an -m option with a grub.cfg file in the "memdisk" tarball. It's quite the same tarball as created by live-build in https://salsa.debian.org/bluca/live-build/blob/master/scripts/build/efi-image So it might be that debian-cd is affected as well. If not, then differences between both ISOs might give hints about the cause. Have a nice day :) Thomas