how to create iso image from DVD Using UBUNTU

Insert the CD or DVD that you want to make an ISO image of, and open a terminal window. To do that, just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command(s) below:

sudo cat /dev/srx > /home/<user_name>/<file_name.iso>

Make sure that you replace (x) with your device number.
for example in my case I would do:

sudo cat /dev/sr0 > /home/aryan/image.iso