不管是出于好奇还是出于真正的需要，你如何判断两张DVD是否完全相同？今天的超级用户问答会介绍一些不同的方法来找出答案。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

图片由卢卡·科利（Flickr）提供。

问题

超级用户reader Mega想知道是否有办法判断两张DVD是否完全相同：

I have two DVDs and if I open the them, then copy the contents to my hard-drive to compare the respective files, it shows no difference. As far as I know, DVDs also have some additional content (such as information saying if the DVD is bootable along with some formatting information I guess).

How can I also check this additional content? Is it possible without additional programs on Windows or Ubuntu?

有没有什么方法可以用来验证两张DVD是否相同？

答案

超级用户贡献者mtak和Dithermaster为我们提供了答案。首先，mtak：

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

• sudo md5sum /dev/cdrom

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

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

• sudo fdisk -l /dev/cdrom

接着是Dithermaster的回答：

Just comparing folders and files misses other things about the disc. If you create an .ISO image file from each disc and byte compare them, you would have a better idea if the discs are really the same or not.

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