Clean up GRUB_MODULES_PRELOAD / grub_modules. Remove the modules already loaded in stock signed grub EFI binaries.

live-build/ubuntu-cpc/hooks/033-disk-image-uefi.binary

@@ -62,15 +62,20 @@ install_grub() {
     efi_boot_dir="/boot/efi/EFI/BOOT"
     chroot mountpoint mkdir -p "${efi_boot_dir}"
 
+    # The modules below only make sense on non-Secure Boot UEFI systems.
+    # Otherwise, with Secure Boot enabled GRUB will refuse to load them.
+    # Any modules already in debian/build-efi-images do not need to be listed.
+    # Furthermore, other modules such as terminal, video_* and efi_* are all
+    # already available.
     case $ARCH in
         arm64)
             chroot mountpoint apt-get -qqy install --no-install-recommends grub-efi-arm64 grub-efi-arm64-bin
-            grub_modules="part_gpt fat gzio ext2 normal chain boot configfile linux search_fs_uuid search_label terminal serial video video_fb efi_gop"
+            grub_modules="serial"
             efi_target=arm64-efi
             ;;
         amd64)
             chroot mountpoint apt-get install -qqy grub-efi-amd64-signed grub-efi-amd64 shim-signed
-            grub_modules="part_gpt fat ext2 normal chain boot configfile linux multiboot search_fs_uuid search_label terminal serial video video_fb video_bochs usb usb_keyboard efi_gop efi_uga"
+            grub_modules="multiboot serial usb usb_keyboard"
             efi_target=x86_64-efi
             ;;
     esac
@@ -78,8 +83,9 @@ install_grub() {
     cat << EOF >> mountpoint/etc/default/grub.d/50-cloudimg-settings.cfg
 ${IMAGE_STR}
 # For Cloud Image compatability
-GRUB_PRELOAD_MODULES="${grub_modules}"
+GRUB_PRELOAD_MODULES="${GRUB_PRELOAD_MODULES:-$grub_modules}"
 EOF
+
     chroot mountpoint grub-install "${loop_device}" \
         --boot-directory=/boot \
         --efi-directory=/boot/efi \