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Is there a tool (preferably free) in OS X that will allow me to verify that an ISO was written to a CD or DVD correctly? I want a tool that can do that without going through the burn first.

If there's a tool that can be used from the command line, that's fine too.

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You have two choices that I can see if you don't want to re-burn and re-verify.

  1. Mount the ISO and the DVD and do a recursive diff of the two file systems. For example, if the DVD is /Volumes/DVD and the ISO is /Volumes/ISO then:

    diff --recursive /Volumes/DVD /Volumes/ISO

  2. Compare the MD5 sums of all the data on the two images. So:

    md5 original.iso

    dd if=/dev/disk1 bs=2048 count=169383 | md5

I'd take option #2 over #1 personally, though both are less than great ways to do a comparison.

You could also try exploiting rsync to do the comparison instead of using diff. If you ran rsync with the --checksum, --recursive and --dry-run options what you'd get back is a list of transfers that rsync thinks it needs to make to make the two file trees look the same.

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Thanks! Note for people using option 2: open Disk Utility and unmount the DVD volume first, otherwise dd will report that /dev/disk1 is busy. – Eliot Aug 27 '14 at 21:23

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