So here's my dilemma:

i ran these 3 commands in terminal, one at a time, to check the hashes of a burnt dvd:

dd if=/dev/cdrom bs=1 count='size' | md5sum

dd if=/dev/cdrom bs=1 count='size' | sha1sum

dd if=/dev/cdrom bs=1 count='size' | sha256sum

The thing is, the md5 of the burnt dvd was the same as the ISO image md5. However the sah1 and sha256 were completely different!


  1. Are the above mentioned commands the correct ones for getting those 3 hashes?

  2. How is it possible for the md5 to match, but the sha1 and sha256 not to? Why is that? And how can i fix it?

Thank you for the upcoming support!

  • Is 'size' really some literal long number? – psusi Jan 21 '15 at 22:53
  • what do you mean literal? in my case it's 3320903680 – Zeno Jan 21 '15 at 23:02
  • Ok, yea.. just making sure you were really giving the number and just omitted it in the question instead of literally trying to pass "'size'" to dd – psusi Jan 21 '15 at 23:06
  • got it. maaan that wouldn't have made any sense :))) – Zeno Jan 21 '15 at 23:11
  • Well, if you are using the same cdrom, and the same size number each time, then it shouldn't be possible for one to agree and the other two not to. – psusi Jan 22 '15 at 1:20
  1. the 3 terminal codes are the right ones to get the hashes. if you verify the hashes with them it is impossible for 1 hash to match and the others not to.

2.they didn't match because i used the md5 checking code correct but for the other two i used: sha1sum dev/cdrom and sha256sum dev/cdrom. I checked the dvd again with the correct terminal commands and they all matched

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