This is a simple guide to help you create ISO image with some short commands in no time!
1- Create a CD image
sudo dd if=/dev/cdrom of=cd.iso |
2- Create a DVD image
sudo dd if=/dev/dvd of=dvd.iso |
3- Create a iSCSI cdrom image
sudo dd if=/dev/scd0 of=cd.iso |
A little explanation
sudo makes sure the command is executed as root. That's needed only if the user you're working under doesn't have enough permissions to access the device. But it's ignored if it's not needed so you can just ignore it as well.
dd stands for Disk Dump
if stands for Input File
of stands for Output File
Have fun!