Is it better to use cat, dd, pv or another procedure to copy a CD/DVD?

## Background ## I'm copying some data CDs/DVDs to ISO files to use them later without the need of them in the drive. I'm looking on the Net for procedures and I found a lot: - Use of cat to copy a medium: http://www.yolinux.com/TUTORIALS/LinuxTutorialCDBurn.html cat /dev/sr0 > image.iso - Use of dd to do so (apparently the most widely used): http://www.linuxjournal.com/content/archiving-cds-iso-commandline dd if=/dev/cdrom bs=blocksize count=count of=/path/to/isoimage.iso - Use of just pv to accomplish this: See man pv for more information, although here's an excerpt of it: Taking an image of a disk, skipping errors: pv -EE /dev/sda > disk-image.img Writing an image back to a disk: pv disk-image.img > /dev/sda Zeroing a disk: pv /dev/sda I don't know if all of them should be equivalent, although I tested some of them (using the md5sum tool) and, at least, dd and pv are *not* equivalent. Here's the md5sum of both the drive and generated files using each procedure: md5 of dd procedure: 71b676875b0194495060b38f35237c3c md5 of pv procedure: f3524d81fdeeef962b01e1d86e6acc04 **EDIT:** That output was from another CD than the output given. In fact, I realized there are some interesting facts I provide as an answer. In fact, the size of each file *is different* comparing to each other. So, is there a best procedure to copy a CD/DVD or am I just using the commands incorrectly? ---------- ## More information about the situation ## Here is more information about the test case I'm using to check the procedures I've found so far: isoinfo -d i /dev/sr0 Output: https://gist.github.com/JBFWP286/7f50f069dc5d1593ba62#file-isoinfo-output-19-aug-2015 dd to copy the media, with output checksums and file information Output: https://gist.github.com/JBFWP286/75decda0a67605590d32#file-dd-output-with-md5-and-sha256-19-aug-2015 pv to copy the media, with output checksums and file information Output: https://gist.github.com/JBFWP286/700a13fe0a2f06ce5e7a#file-pv-output-with-md5-and-sha256-19-aug-2015 Any help will be appreciated!