Unlike Windows Vista or XP, Linux doesn’t have to separately install Nero Burning ROM or CD image writer if you plan to create an ISO image to backup a CD or a DVD.

The standard dd command is available in linux to do this job.

Do not mount CD. Verify if cd is mounted or not with mount command:

#mount

If the cd is mounted automatically unmount the cd using the unmount command:

#umount /dev/cdrom

Check the exact location where the cd is mounted to unmount it.

Now once the cd is unmounted we can create an ISO image of it using the dd command

# dd if=/dev/cdrom of=/tmp/cdimg1.iso

where,

if=FILE : read from FILE instead of stdin
of=FILE : write FILE instead of stdout