Creating DVD or CD ISO file

To create a DVD ISO, one can use this command at shell (i'm using bash)
dd if=/dev/dvd of=/mydir/myDVDImage.iso

Or to create a CD ISO, one can use this command
dd if=/dev/cdrom of=/mydir/myCDImage.iso

Or if one prefers a friendly GUI tool, i suggest K3B burning tool. Click on menu Tools -> Copy DVD / Copy CD. And dont forget to check the "Create Image Only" checkbox before start copying the DVD or the CD. Notice the directory too that will hold the output image file in the burn window dialog.