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I have an ISO file and a DVD burned from that ISO file. Is there a way I can validate that the DVD contains the same as the ISO file and that nothing is wrong with the DVD?

I have the tools available on the System Rescue CD.

  • it suprises me that a rescue cd doesn't have an md5sum or shaXsum utility. – RobotHumans Dec 9 '10 at 11:28
  • @aking1012: It does! Several of them actually. I just don't know how to use them to compare an ISO with a DVD :p – Svish Dec 9 '10 at 11:56
  • okay I just didn't see it on the included utilities list in the link, perhaps I overlooked it...in that case harrymc should get the check unless you specifically request a shasum – RobotHumans Dec 9 '10 at 13:21
  • What disc burning software do you use? Most of them have a 'verify burn' option that compares the ISO/Disc checksums. – invert Dec 9 '10 at 14:41
  • @wez, That I know. Thing is this is a DVD i burned a while ago and I think it might have gotten buggy or something. I was able to install my OS from it back then, but now it is giving me lots of trouble. Could be my hardware going bad too, but I'd just like to rule out a faulty install disk :) – Svish Dec 9 '10 at 23:03
15

The following command compares the contents of two binary files, and print the offset of the first differing byte. Replace /dev/dvd by the path to the DVD device (/dev/cdrom, /dev/scd0, /dev/hdc, …).

cmp /dev/dvd /path/to/foo.iso

I'm not sure if all DVDs contain an indication of where the data ends (I think some CDs don't); you can limit the comparison to the size of the image file.

ls -l /path/to/foo.iso  # copy the file size, e.g. 123456789 bytes
cmp -n 123456789 /dev/dvd /path/to/foo.iso

You can also compute a checksum for the image file, compute a checksum for the disk, and check that they match. This is slower for a single comparison, but faster if you need to compare many disks against one image, and allows the image and the disk to be on different computers. To detect accidental corruption, md5sum is perfectly suitable.

md5sum /path/to/foo.iso
md5sum /dev/dvd     # if the size can be determined; otherwise:
head -c 123456789 /dev/dvd | md5sum
  • 1
    worked great for me, but I had to use cmp -n: cmp -n 123456789 /dev/dvd /path/to/foo.iso – bmaupin Jul 31 '12 at 21:00
  • @bmaupin That was a typo, I've fixed it. Thanks for the notice. – Gilles Jul 31 '12 at 21:02
5

Since the question is not OS-specific and Windows users may find their way here, I’ll suggest that a relatively easy way to accomplish this on Windows is to mount the ISO (OSFMount is particularly good), then compare (e.g., with WinMerge) the CD/DVD drive root with the mounted volume root:

winmerge d:\ e:\
  • 1
    I just created this account to say thanks! I wanted to check if a written disk with windows xp was identical to the iso of it and this method worked great. – Mario Vlad Apr 21 '13 at 23:52
3

Here are the correct steps to verify 256sum of the iso before and after burning.

determine iso sha256sum..

$ sha256sum ubuntu-5.10-dvd-i386.iso
e41c0631f6f2c138a417b59bcb880fce

then determine size of iso in bytes...

$ wc -c ubuntu-5.10-dvd-i386.iso  
3048179712

then dd your cd/dvd drive |then count the first bits of each file to sum |then read its sha256sum

$ dd if=/dev/sr0 | head -c 3048179712 | sha256sum  
e41c0631f6f2c138a417b59bcb880fce

Substitute /dev/sr0 with /dev/cdrom or other drive name depending on system.

For a better DD experience and to view dd's progress in real-time without having to write a script, use dcfldd the forensic dd (dcfldd can port to 2 different outputs as well.)

sudo apt-get install dcfldd

(shamelessly stolen from an article on unbutu.com)

2

I assume from your post that you are on Linux.

See this article : Verify a burned CD/DVD image on Linux.

The main idea is simple :

cat iso-file.iso | md5sum
dd if=/dev/hdc | md5sum
1

On Windows, install VCdControlTool.exe and WinMerge (remember to add it to system path, there's a specific checkbox in the installer).

Insert DVD, usually mounted on d:

Mount the .iso with VCdControlTool.exe, e.g. on z:

From cmd, run:

winmergeu.exe /r d:\ z:\

It might take a while.

Caveat: WinMerge runs out of memory with big files.

0

On Windows, comparing an already burned DVD or CD with an ISO file is super-easy with the help of the donate-ware "ImgBurn". Has helped me a ton in the past!

Still need to find something similar for OS X / macOS, because it seems to me that above mentioned methods for Linux / Unix don't work there.

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