It’s been a while since I last did this but you never know when you might need it. When you see a “dd” command, you better make sure you know what you are doing. In other words, don’t type this just as you see it!
Identify where CD/DVD is mounted:
mount
Unmount the CD/DVD:
umount /dev/sr0
Copy data from CD/DVD to ISO file:
dd if/dev/sr0 of=~/image.iso
Or use dcfldd if you prefer:
dcfldd if/dev/sr0 of=~/image.iso