To boot directly from a Puppy linux Live CD using these instructions
Put this in /etc/grub.d/40_custom
and run update-grub2
.
menuentry "Puppy linux ISO" {
set isofile="/boot/april.iso"
loopback loop (hd0,1)$isofile
linux (loop)/vmlinuz iso-scan/filename=${isofile} quiet splash
initrd (loop)/initrd.q
}