To do so first login as a root user.
Let us assume the iso image name is disk-test.iso
# mkdir /mnt/iso
# mount -o loop disk-test.iso /mnt/iso
# cd /mnt/iso
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