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I have two DVDs and if I open the DVDs and copy the content to the HDD and compare the respective files on the HDD it shows no difference. As I know DVD does also have some additional content (this content includes information saying if the DVD is bootable and some formating information I guess).

How can I check also this additional content?

Is it somehow possible without additional programs, using Windows or Ubuntu?

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Are you comparing store bought movie DVDs or another type of DVD? –  pacoverflow Jun 10 at 21:06
    
Not sure if it would work...You could try 'dd if=/dev/cdrom of=file1.img' and 'dd if=/dev/cdrom of=file2.img' and then 'diff file1.img file2.img'. –  BenjiWiebe Jun 10 at 21:18
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Yeah, although it involves unnecessary steps, you could always compare images. There should be free software to create them on Windows, too. But if you don’t want extra software... –  Daniel B Jun 10 at 21:31
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You can usually read the Burst Cutting Area to find that information out. It is effectively a serial number for DVDs, truly duplicate DVDs will have identical BCAs. –  Andon M. Coleman Jun 11 at 7:30
    
define "exactly". Down to molecular level they're never going to be the same... –  jwenting Jun 12 at 8:05

4 Answers 4

The easiest way to determine if 2 discs are the same is to run a hash of both of them:

sudo md5sum /dev/cdrom

If the hashes match, the disks are exactly the same. However this will not tell you what is different about them. Even if a single bit is different you would get a totally different hash.

You can check the partition table of a disc with fdisk:

sudo fdisk -l /dev/cdrom
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In the question it says using Windows or Ubuntu... –  mtak Jun 10 at 20:19
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O_O Never thought that CDs use a usual MBR. Just checked this on kubuntu iso image, and fdisk -l indeed appeared to print some sensible data. Looking with xxd at first 512 bytes also gave very similar structure to that of HDD MBR. +1 for enlightening :) –  Ruslan Jun 11 at 10:55
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@Chips_100 If you are talking about a hash collision, the chance of that are astronomically small. (Probability of two hashes accidentally colliding is 1/2^128 which is 1 in 340 undecillion 282 decillion 366 nonillion 920 octillion 938 septillion 463 sextillion 463 quintillion 374 quadrillion 607 trillion 431 billion 768 million 211 thousand 456, source) –  mtak Jun 11 at 13:45
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@Chips_100 Sure, you're right, but we're talking about MD5. Yes, collisions have even found, but they aren't random collisions, they are generated by a program that does an exotic thing called maths for a couple hours. Needless to say, to hash, you read the entire file and do math operations on the data. If you're gonna use hashing to compare files, you might as well just do a byte-by-byte comparison. –  Cole Johnson Jun 11 at 15:12
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Just comparing the folders and files misses other things about the disc. If you create an .ISO image file from each disc and byte compare them you'd have a better idea of the discs are really the same or not.

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Instead of byte compare, you could use a checksum or hash. –  Ryan Jun 11 at 17:35
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As @colejohnson says on a reply to another answer: "Needless to say, to hash, you read the entire file and do math operations on the data. If you're gonna use hashing to compare files, you might as well just do a byte-by-byte comparison". –  That Brazilian Guy Jun 11 at 21:22

When using Windows you can use the Microsoft File Checksum Integrity Verifier to get hash values of files on the disk.

The Microsoft File Checksum Integrity Verifier tool is an unsupported command line utility that computes MD5 or SHA1 cryptographic hashes for files.

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-1 this way it will compare only files and folders, and only for the current recording session. –  That Brazilian Guy Jun 11 at 21:08

To compare the content of the files one can use tools such as freefilesynch. But it is not possible to compare the format tables of boot sector of those DVDs

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