Trying to create UEFI & Bios bootable .iso using xorriso

[larry]

I'm using xorriso to create an iso that boots on both Bios and EFI. The 
iso boots fine on a bios machine but isn't even recognized on an EFI 
machine.

Here's the result of the command fdisk -l:

larry@larry-Satellite-C55-A:~/foxclone$ fdisk -l foxclone025-02.iso
Disk foxclone025-02.iso: 660 MiB, 692060160 bytes, 1351680 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x45d15306

Device              Boot Start     End Sectors  Size Id Type
foxclone025-02.iso1 *        0 1351679 1351680  660M  0 Empty
foxclone025-02.iso2        276    5203    4928  2.4M ef EFI (FAT-12/16/32)


The method to create the EFI partition was:

#! /bin/sh

BOOT_IMG_DATA=$($HOME/foxclone/newiso -d)
BOOT_IMG=efi.img

mkdir -p $(dirname $BOOT_IMG)

truncate -s 4M $BOOT_IMG
mkfs.vfat $BOOT_IMG
mkdir -p $BOOT_IMG_DATA/efi/boot

grub-mkimage \
    -C xz \
    -O x86_64-efi \
    -p /boot/grub \
    -o $BOOT_IMG_DATA/efi/boot/bootx64.efi \
    boot linux search normal configfile \
    part_gpt btrfs fat iso9660 loopback \
    test keystatus gfxmenu regexp probe \
    efi_gop efi_uga all_video gfxterm font \
    echo read ls cat png jpeg halt reboot

mcopy -i $BOOT_IMG -s $BOOT_IMG_DATA/efi ::


The build script follows:

orig_iso="$HOME"/foxclone/foxclone025-01.iso
new_iso="$HOME"/foxclone/foxclone025-02.iso
new_files=$HOME/foxclone/newiso
mbr_template=isohdpfx.bin

xorriso -as mkisofs \
    -r -V 'Foxclone' \
    -o "$new_iso" \
    -J -J -joliet-long  \
    -isohybrid-mbr /usr/lib/ISOLINUX/isohdpfx.bin \
    -b isolinux/isolinux.bin \
    -c isolinux/boot.cat \
    -boot-load-size 4 -boot-info-table -no-emul-boot \
    -eltorito-alt-boot \
    -e --interval:appended_partition_2:all:: \
    -append_partition 2 0xef efi.img \
    -no-emul-boot -isohybrid-gpt-basdat \
    "$new_files"


Results of dumpet

larry@larry-Satellite-C55-A:~/foxclone$ dumpet -i foxclone025-02.iso
Validation Entry:
    Header Indicator: 0x01 (Validation Entry)
    PlatformId: 0x00 (80x86)
    ID: ""
    Checksum: 0x55aa
    Key bytes: 0x55aa
Boot Catalog Default Entry:
    Entry is bootable
    Boot Media emulation type: no emulation
    Media load segment: 0x0 (0000:7c00)
    System type: 0 (0x00)
    Load Sectors: 4 (0x0004)
    Load LBA: 38 (0x00000026)
Section Header Entry:
    Header Indicator: 0x91 (Final Section Header Entry)
    PlatformId: 0xef (EFI)
    Section Entries: 1
    ID: ""
Boot Catalog Section Entry:
    Entry is bootable
    Boot Media emulation type: no emulation
    Media load address: 0 (0x0000)
    System type: 0 (0x00)
    Load Sectors: 8192 (0x2000)
    Load LBA: 275968 (0x00043600)


I'd appreciate some help on this,
Larry