On 23/05/2023 05:18, David Christensen wrote:
1. No UEFI boot variables/entries to create; BIOS/MBR detects devices connected to interfaces and I use Setup to set the boot order. (I also set "Boot USB Devices First", so I can boot a live USB stick without having to touch Setup.)
There is no problem to boot usual live images that have single FAT partition. Removable disk layout is used in this case EFI/BOOT/BOOTX64.efi (on amd64). It should be possible to enable USB boot and increase its priority from firmware setup. It might be implemented as modifying NVRAM to add a boot entry and to modify UEFI boot order.
I have never tried to make a portable installation. Even if specific UEFI implementation ignores removable path on EFI System Partition, I would try to make a first FAT partition that is not ESP with signed shim as EFI/BOOT/BOOTX64.efi
With GPT, there is a secondary/ backup partition table located at the end of the device. This forces you into to less flexible imaging choices:
I expect that --backup, --restore-backup, and --move-second-header options of sgdisk may help.
