On Unix like systems it's easy to create an ISO image from an CD or DVD with dd.
You only need to know the device name of your CD or DVD device and a terminal.
If you don't know the device name open a terminal and type:
This shows you all of your active devices.
Now use the well known dd command to read all data from the device and write it 1:1 to a disk image.
dd if=<nameofyourdevice> of=<filename>
dd if=/dev/disk1 of=myiso.iso