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.
Readom (“read optical media”) is part of the wodim package. It performs error checking during the copy/imaging process and if it fails during a copy it will let you know. The command is simple:readom dev=/dev/cdrom f=cdimage.iso
# Eject (open) the cd driveeject cdrom
# Eject (close) the cdrom driveeject -t cdrom
# Create the imagereadom dev=/dev/cdrom f=/cdimage.iso
A further notable down side to using dd is that it does not create a sparse image i.e. it copies all of the blank space from the source disc too.
For the same reasons that you would use readom for creating an image, you shoud use wodim for burning the image back to CD or DVD again it's a simple command:
# Burn the imagewodim -v -eject cdimage.iso