Just in case this will help anyone else, as I always forget how to do this, even though its been explained to me more that once (thanks to those patient enough). I am putting it in my own words from my own system to try to hammer it into my thick skull. Too bad we don't have 8.3 or 8.5 assuming they are better. I looked at the site selling the magazine and it says its a PDF which makes no sense, and after all the effort I don't want to pay $15 for a DVD. I wish Mr Knopper would offer a $5 download of current code. That would be sensible. I like his choices of games a lot.

Anyway, This is my /etc/grub.d/40_custom file stored on my main OS which is antiX on /dev/sda1. After editing the file sudo update-grub needs to be run to generate the new grub.cfg. Then when you reboot it gets used.

On my system:
/dev/sda3 has directories where ISO files are stored to boot from loopback. It runs exactly as it would have from flashdrive or DVD, and no changes are saved.

/dev/sda7 was formatted to Ext4, then Knoppix 8.2 was loaded by booting Knoppix 8.2 from flashdrive with tohd=/dev/sda7. I then renamed the file /KNOPPIX/knoppix-data.inf to was-knoppix-data.inf so that the mkimage boot parameter would ask how big of a persistence file to build and then build it the next time I booted into it. Note the nocompiz does the same thing as no3d (which now crashes the machine) used to do for older versions.

Code:
menuentry "Knoppix 8.2 DVD ISO Loopback" {
    set isofile="/knoppix-8.2/KNOPPIX_V8.2-2018-05-10-EN.iso"
    loopback loop (hd0,3)$isofile
    echo "Loading Knoppix 8.2 linux"
    linux (loop)/boot/isolinux/linux bootfrom=/dev/sda3$isofile keyboard=us lang=en tz=America/Chicago nocompiz
    echo "Loading minirt"
    initrd (loop)/boot/isolinux/minirt.gz
}
menuentry "Knoppix 8.1 DVD ISO Loopback" {
    set isofile="/knoppix-8.1/KNOPPIX_V8.1-2017-09-05-EN.iso"
    loopback loop (hd0,3)$isofile
    echo "Loading Knoppix 8.1 linux"
    linux (loop)/boot/isolinux/linux bootfrom=/dev/sda3$isofile keyboard=us lang=en tz=America/Chicago no3d nomce hpsa.hpsa_allow_any=1 loglevel=1
    echo "Loading minirt"
    initrd (loop)/boot/isolinux/minirt.gz
}
menuentry "Knoppix 8.2 from /dev/sda7" {
    insmod part_msdos
    insmod ext2
    set root='hd0,msdos7'
    linux /KNOPPIX/linux64 knoppix_dir=/KNOPPIX mkimage keyboard=us lang=us tz=America/Chicago nocompiz
    initrd /KNOPPIX/minirt.gz
}