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I tried dd, dd_rescue and ddrescue, all failed. I thought these tools bypass the filesystem and make a bitwise copy.

dd is fooled, it finishes but just produces a small file and states it's finished.

dd_rescuse and ddrescue are complaining about read errors and are intolerably slow. These tools can copy only a few MB in 10 minutes.

Why is this happening, why are these tools failing?


AnyDVD makes the disc copyable in a second on a Win7 host. It says that the UDF filesystem is patched, curiously, it also says that there are no bad sectors. The whole disc can be copied in 10 minutes.
UPDATE: As for the solution, see my similar question on superuser.

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2 Answers 2

up vote 7 down vote accepted

I think that the simplest answer is that dd, dd_rescue and ddrescue are not designed to defeat copy protection schemes. They make no assumptions about the format of the data and try to maintain the integrity of the whole of the original on disk data.

In the case of dd I suspect that it is terminating due to an intentional read error on the disk that is part of the copy protection scheme. It would help to confirm this if you included the commandline output from dd with your question. You may also find some read errors recorded in the dmesg command output.

You may get dd to copy more of the file by passing the noerror flag to it on the commandline. However you may find that this just leaves you with corruption in your final image.

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Thanks, upvoted. If I bypass the filesystem and do a "bitwise" copy, and replace the read errors with zero bytes, would that still yield a corrupted image? After all I only replace that data with zero bytes that cannot be read anyhow. I will include the dmesg output later, I do not have the DVD with me. –  Ali Feb 24 '12 at 15:43
    
Really the only way to determine if the final image is "corrupted" is to work out if it is usable. Part of that will be making sure that only the actual broken blocks are read as zeros and none of the surrounding blocks. That might mean that you need to pass a bs=512 (from memory that is the CD/DVD blocksize) parameter to dd. Really though that sort of thing is what dd_rescue is designed to do. It might take time but it tries to lose the minimum amount of data possible. –  Richm Feb 24 '12 at 16:40
    
OK, thanks for all your help. I am screwed on way too many levels. I ended up using AnyDVD. –  Ali Feb 28 '12 at 21:08

I'm not sure why this works but opening the DVD first with VLC, just enough to view the menu, and then pausing lets dd work.

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Thanks. My DVD cannot be opened with VLC; unfortunately, my situation was a lot more complicated. –  Ali Dec 30 '13 at 16:07

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