Copying raw data
The holy grail of any data cloning job is 1:1 replication of the source. In simpler words, cloning is different from copying because copying data only works and is applicable for storage mediums which have a working filesystem and you only need the visible data. Cloning, on the other hand, will copy each and every byte of the storage medium, without caring if that particular storage area is blank or filled with data. While it obviously takes up more space than a normal copy, you get an exact representation of the filesystem/data on the storage medium. It is useful in cases like data recovery, where you would rather work with a 1:1 copy to recover data rather than risking further corruption of the medium. It is also useful when you want to clone drives and discs to make perfect backups.
The basic structure of the 'dd' command is as follows:
dd if=/dev/source of=/mnt/disk/destination.iso
While it does accept other parameters like bootsector size and so on, this small snippet is enough to create a 1:1 copy of the source and place it at the destination. In our case, we will be copying from a CDROM. In Linux, the CD-ROM can be found at many different places inside the /dev folder, so a small part of the command will have to be changed by you to what your computer's CD drive reflects:
dd if=/dev/cdrom of=/media/cdclone.iso
Replace the 'cdrom' with whatever location your computer's CDROM holds. It might be /dev/hdX or /dev/sdX. The command will take a few minutes and will make an exact copy of the CD and store it inside the /media folder with the filename cdclone.iso.