Grub4dos To Boot ISO Disk Image

Using grub4dos to boot Ubuntu Ubuntu 18.04 ISO disk image, here is the entry for the file MENU.LST:

title Ubuntu 18
  fallback 6
  find --set-root /iso/ubt1804.iso
  map --heads=0 --sectors-per-track=0 /iso/ubt1804.iso (0xff)
  map --hook
  root (0xff)
  kernel /casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper iso-scan/filename=/iso/ubt1804.iso splash
initrd /casper/initrd.lz

NB,

• For Ubuntu 64bit from 14.04 to 17.10 vmlinuz.efi was used, so kernel has to be /casper/vmlinuz.efi, but
• For older versions and 18.04+ use /casper/vmlinuz
• For Ubuntu 32bit, it has always been vmlinuz
• For smaller ISO disk images, or your RAM is extremely big, you can use --mem for the map command to put the whole disk into system memory, like this: map --mem /iso/smallcd.iso (0xff) || map --heads=0 --sectors-per-track=0 /iso/smallcd.iso (0xff)

Ref:

• https://ubuntuforums.org/showthread.php?t=2398574
• and some other two which I have lost.