Hi,
the ISO obtained with refractasnapshot doesn't boot when used with debian Testing (Stretch). In the documentation, you say "may be" for Stretch and Sid... : in fact, it's "not" for Stretch
The error is : (initramfs) aufs not found
So, I worked around

and found the solution

:
> the package aufs doesn't exist in Debian Testing actually
> the solution consist to use overlayfs in replacement
> the simple way to correct the problem is : at boot screen , select option and press tab to obtain the boot command. Delete "union=aufs 3" and replace by "union=overlay" and press enter. That's it ! The boot works now.
> the file refractasnapshot/iso/isolinux/live.cfg should be modified so to boot automatically with Debian Testing.
Thanks for this excellent tool !
Best regards,
X. HINAULT