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I have a number of CDs and DVDs (some RW and some not). Some of these disks contain simple files (such as .txt, .doc, etc) and others contain Dell system drivers, various Windows OS's and so on. I am in the process of making duplicates of all these disks because the original disks are getting old and have a retention period (an amount of time before the disk is more vulnerable to corruption) that is going to expire in the near future.

The process I am following: Create .cdr disk image, convert to .iso image, burn .iso into a new disk all on a MacOS.

My problem: I would like to validate whether the new disk is exactly the same as the old one by comparing them somehow (I know MacOS's disk utility offers "verify" option, but long story short, I don't have access to that feature for problem at hand).

I have looked at numerous sites, some of which offer solutions such as using ImgBurn, Winmerge, and Hashing the two ISOs and comparing. One issue: none of these sites seem to take into account or explain whether these methods examine only the files within the .iso image or if they examine the files within the .iso image as well as the metadata (partition layout, file structure, bootcode, etc...).

My Question in a nutshell: do Hashing (likely SHA-256), Winmerge, or ImgBurn take into account hidden data (metadata and other data that might exist unseen to users) as well as the files contained in the .iso file? Also, what if I compare the disk itself (inserted in one of the drives) against its own .iso image?

Sorry for the length. Trying to give as much info as I can. Thank you in advance!

Also note, I would prefer not to use external tools such as ImgBurn and Winmerge; but if left with no choice, I am willing to use them. Willing to use BeyondCompare because I already have access to it.

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If you're looking to check on a file-by-file basis, you can do this on macOS with diff (assuming you have two drives for the original and the duplicate at the same time):

diff -rq /Volumes/Original /Volumes/Duplicate

Update the paths with two paths to where the disks are mounted. This will check every file reachable, including telling you when a file exists in one but not the other.

The -r option makes diff recurse into the directory structure, and the -q flag makes it only output differing files (instead of trying to show differences inside each file).

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  • .Yes. That is something I can try, but I am looking to do more than just file-file. For file-file, I have available tools like BeyondCompare than can compare most types of files (including .iso) byte by byte (or bit by bit - I can't recall right now). Only issue is BeyondCompare won't compare .iso files on a partition, metadata level and only on a file to file level (it treats .iso files like zip files and just compares the files inside). But thank you very much for your answer; its good to learn tools such as diff for the future.
    – Shamioso
    Commented Feb 18, 2021 at 14:04

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