Errors when backing up using dd

It has always been my understanding, and perhaps I am wrong; that dd would always copy a bit for bit stream to another location, be it file or device. That is not happening in this case. Do any of the ‘dd’ users out there like me know the answer to this situation. Firstly, I do not want dd “judging” bits. I don’t want it encrypting or decrypting or altering or converting (for example into an ISO) my data. I have a video dvd, I rented the other day, I know, there’s copyrights, but I wanted to watch later. And I have plenty of DVDs of my own around. And I know the data is encrypted. But I don’t want dd to care. So I tried this;

dd if=/dev/sr0 of=file.dat conv=noerror status=none

This is the only thing I could use to get no errors. And it didn’t work. It spit out about 200 MB. If I didn’t use the conv or status flags, I would get IO errors to stderr. There’s no DVD damage and no DVD-R damage. Why is it not wanting to copy? It is “looking” at something. Why doesn’t it just copy? Not read and not like, and so spit out garbage or break.

For any normal media dd will make a one-to-one copy. However, DVDs, Blu-Rays , and many game disks, don’t fall under this category, and will “talk” directly with the drive to prevent duplication.
The reason you cannon make a bit-for-bit copy of a DVD, is because of the copy protection. There’s nothing you can do to stop this. Both the disk, and the drive reading it work to prevent unauthorized reproduction of the data

You will need specialized software in order to make backups of DVDs. This falls in a legally grey area that I’m not sure would be appropriated on this site. I might make some suggestions, but I don’t know any for Linux that produce a pure disk image, and certainly none that are free.

MakeMKV can rip video data, and is semi-freeware, but it won’t get you an iso.


Has also been asked on other general forums before, so worth looking there too:

OK I see. Well I am glad there’s nothing wrong with dd and the DVD media or media reader. Well then I guess so much for the power of dd then. I am a big fan of dd. Thanks much. Sounds like in order to use dd to copy, the bits have to be changed. Well it’s not dd’s fault anyway.

1 Like

You can blame the establishment that encrypts the content of DVDs and BluRays for the issue you see. With copyright and DRM protection it is difficult to make an actual backup identical to the original. AFAIK copying DVDs has never worked since that would allow bypassing all the DRM and potentially allow piracy of the media. Similar tactics were used as far back as 3.5 inch floppy disks in the 90s to prevent unauthorized copies.

You can, however, rip the media to a file using makeMKV or similar (as was already mentioned) and that mkv file is acceptable as a backup. In fact I just did that with 5 brand new BluRay disks and put the files on my plex media server for home use and put the actual disks up so they do not get damaged…

they don’t want you copying their property, so they alter and mess with yours to stop it. IMO my HD is mine; they evidently don’t think so.

IO errors, are they using the ioctl() from ioctl.h or from stropts.h? That’s the only two that I know of, other than kernel code I would suppose; whatever kernel functions would be.

This CSS was only 40 bit of encryption. They have to have come up with something better, AES or something surely. But if they are messing with your hardware, maybe they wouldn’t need encryption as much.

The thing is that DVD’s are subject to data rot, like anything else. Of course that takes a long time, and DVDs might be long out of fashion before that happens. Things like super 8s they want you to backup to VHS or DVDs. I do not want to backup my DVDs to google or any other online service either. My DVD’s bought or homemade is none of their business, and I might not have access at some point to google and so on. And DVDs are fragile too of course.

I don’t get how you claim they are doing anything with your hardware. Just because the data on the DVD is written in such a way that it cannot be ready directly by using dd does not mean anything about the hardware.

Your system can read the dvd if it has the correct encryption keys and thus addresses the data the same as your DVD player does. That is not a hardware issue, but rather a need for the correct software to tell the hardware how to read it properly.

Nobody has said one word about putting the data online. Lets not be going off on a tangent here.

Well perhaps I’m a pedant, but there is actually something wrong with your DVD player drive.

It is designed to disobey you. The manufacturer of the DVD drive took specific action to essentially booby trap every product they sold so that it wouldn’t work against its owner and prevent copying of DVDs. That is wrong in every sense.

I don’t believe the DVD disc because the disc does not process data. But the drive does. Software code exists and runs inside the drive and makes a decision. A decision against you. That is wrong.

Blaming the hardware manufacturer for the way the disk is created? The optical disk is the result of the those who produce the data. The optical drive in ones PC is a simple dumb device that is designed to read every bit of data on the disk.

The dvd drive is a mechanical device that is controlled by the software using it, and not designed to override anything the software does. Try with any other disk than a commercial video DVD and see if dd can copy it. If dd will copy that other disk then it is related to what is on the disk and not the drive or the software reading it. What is on the disk can affect the software reading it though, since encryption and addressing both affect how the data is read.

Plain and simple!

Although anybody is free to believe as they choose.

How sad that you’re so confident, because you clearly do not understand how CSS works.

Your DVD drive runs software internally (maybe you’d be more happy to call it firmware) that recognizes encrypted discs. And this software has the keys to decrypt them. And it will do so, in entirety, if an equally treacherous software program executing in your OS environment (say, WinDVD?) commands the drive to do so and its command is cryptographically signed via keys that are withheld from you.

What insufferable peasants of a users we must be.

But dd doesn’t have those keys. Now the ATA protocol doesn’t have a ioctl like FU_Peasant, so it just throws I/O errors. But these are a lie. There is no I/O error. The drive has decided to not give you the data because its manufacturer, Phillips/Sony/Adaptec/whoever made an agreement with the MPAA that prioritized their interests over your own.

That is wrong. And so yes. Something is wrong with the drive. And all other DVD/BluRay drives you can get your hands on will also be wrong in the same way. They are working the way their treacherous manufacturers intended, and that is wrong.

MakeMKV is one of many workarounds out there which began with DeCSS (Google That), and I find MakeMKV actually more useful than ISO files to copy DVDs. It can ‘discover’ hidden video segments, and you can choose to skip audio tracks you don’t want. Or prune out all but the longest video streams to eliminate previews, etc. I could see it being a hassle if someone made a DVD that fully utilized menu-ing to create an interactive choose your own adventure DVD. I did one like that in highschool for my school yearbook, but I don’t think one has ever been made like that commercially.

There is a distinct difference between copying an optical disk and copying the data from an optical disk.

Copying an optical disk requires a low level software such as dd to read byte for byte every byte on the disk in sequence, and is usually used to create an image file, of which an iso is one type.

Copying the data from an optical disk may require simple software such as cp, rsync, etc. or it may require more involved software such as makeMKV, k3b, blender, or similar to handle and decypher the encryption such as is used on commercial DVDs for the explicit and publicly stated purpose of preventing digital piracy.

Copying the data has nothing to do with the underlying physical structure, but does require the ability to use tools to manage the decryption and follow the logical structure.

Copying the device, OTOH, does require the ability to read every byte in sequence from beginning to end and if the disk was created such that the device cannot be read in sequence every byte by byte then tools such as dd will fail.

@b3y I think I understand what you’re trying to say, but the fact is that this isn’t something wrong with the dvd player in the sense that it is doing exactly what it should be doing—i.e., it is not a bug or unexpected behaviour. As noted in the discussion, these are measures put in place to prevent piracy and copyright infringement. There may be hardware out there that does not include these measures (although I would assume that would add quite a bit of liability to the hardware manufacturer as they are helping to circumvent measures to prevent piracy/copyright infringement). At a higher, philosophical level, I can see how not being able to duplicate something one owns is perhaps wrong—but this is another example of where how things should be and how things are differ.

This topic has been discussed sufficiently, certainly to address the initial issue. So let’s not post any more unless there is useful factual information to add here.


What some of this sounds like is that we have lost the ability to simply give someone my book, for example. I can’t give someone my dvd without them having to pay again for something. There is no option for non commercial use. I think my point there is understood. But to dd, perhaps it is not a “low level” as I thought. It can manipulate data; but not just simply read and write bit for bit in order a disk,DVD,USB, and such. The ioctl some have mentioned, is that the ioctl defined by POSIX? Or the more linux version? Or some kernel function? Or is ioctl mentioned here in the thread more abstractly?

What comes to mind for me in regards to ioctl is the function mentioned in the link above. An older version.

I am sounding more like Richard Stallman in many ways. And he is absolutely right in his beliefs.

That’s not quite the case, though. You can give your dvd to others just as you can give your book. You cannot make copies of it to give to others—in the same way that you cannot make photocopies/xerox/digital scans of a book you own to share with others.

Commercial products that are proprietary/non-FOSS cannot be expected to be freely shared, re-used and studied. They are simply not sold on those terms either philosophically or legally. When one purchases proprietary products, one agrees to these terms even if one is not explicitly aware of what the terms are. Proprietary products are explicitly about ensuring that creators get paid—and allowing users to freely copy and share material will not allow that. This is not limited to film DVDs. Pretty much any proprietary product forbids copying and sharing—Windows OS (any non FOSS distribution), playstation/xbox games, or songs cds (or cassettes) etc. are all examples of this.

As for dd being “low-level”—“low-level” is quite an abstract concept. It could mean anything from at the hardware level to a “low level programming language”. dd is still a user-space tool, so it sits on top of system libraries, and hardware firmware. So for cases where the system libraries and hardware firmware allow a bit for bit copy, dd works, for cases like this where it doesn’t, dd does not.

Have you had a chance to read through the stackexchange link? It contains information on the ioctl bits, and includes a link to the discussion about their addition to allow reading cdroms etc. There’s not much more to add here.


I saw the GetBusKey() in the source code. I will take a look at that later.

Freedom First… Where is that from?

Treachery is wrong. A computer you own should do what you command it to do.

Any tool you own, even weapons, should do what you command them to do. Could you do something bad with them? Absolutely. That is your right as a sentient being. And if you do, in society, you may face consequences in law. It is up to you to use your tools in a manor you’re morally okay with. Your tools should not be making the decision for you. Such is a de facto violation of your freedom, and that’s wrong.

For many commercially produced movie DVDs, commonly available drives will violate your freedom. If you make your own DVD by yourself, the digital restrictions management system will not be activated by default.

It’s something that the authors of the disc have to opt-in. And if a disk’s authors have opted it in, then your drive might even refuse to read at all in some DVD players depending on which ‘region’ of the world the authors marketed to be sold in.

It’s pretty nutty the amount of work the motion picture industry put in to this anti-feature just to subvert your freedom.

Just to protect their intellectual property rights under copyright laws.