1. Would you please share the contents of...
(A) <Cubic Project Folder>/custom-live-iso/boot/grub/grub.cfg
(B) <Cubic Project Folder>/custom-live-iso/boot/grub/loopback.cfg
You might also want to try...
2. Instead of dd, try using mkusb (https://help.ubuntu.com/community/mkusb) to create the USB image.
3. Have you tried to boot your customized iso directly from your hard drive into Virtual Box (instead of creating a bootable USB)?
1. Would you please share the contents of...
(A) <Cubic Project Folder> /custom- live-iso/ boot/grub/ grub.cfg
(B) <Cubic Project Folder> /custom- live-iso/ boot/grub/ loopback. cfg
You might also want to try...
2. Instead of dd, try using mkusb (https:/ /help.ubuntu. com/community/ mkusb) to create the USB image.
3. Have you tried to boot your customized iso directly from your hard drive into Virtual Box (instead of creating a bootable USB)?