Two frequent recommendations made online for creating ISO images are to use dd or cat e.g. For example:
ORcat /dev/cdrom > cdimage.iso
Neither are appropriate to create an image of CD or DVD.
- They provide no error checking and require a hash checksum such as MD5 or SHA1 to verify the image created is true to the original media; and
- Neither dd or cat lock the underlying files so there's a risk they could change whilst the image is being created.