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#9 simulation of bad sectors
STORY:
It becomes unnerving common behaviour from software companies to include piracy countermeasures in software, which actually prevents making backup copies of CDs/DVDs. Add this to the fact those companies are not very customer-friendly when ordering backup copy from them and you will get that punished person is not a "pirate" but a customer.
The oldest, the most trivial, yet still effective method is adding bad sectors to CD/DVD in process of making a disc. When you burn a copy of such disc, you will get "correct" version of it and that is how installer can tell the difference.
WISH:
Please provide a method to add info to .iso files (and others) -- additional file -- with bad sectors data (just numbers in text format?) and then use those data to return error code on reading such sector. That way the "client" of CD/DVD would get positive identification of the image.
Or/and special image format which contains information about bad sectors plus utility to copy CD to image with bad sectors.
This won't help making CD backup but at least image backup, and it would be a big help anyway.
Hmm. We should definitely add support for simulation of bad sectors (by triggering hard read errors) at some point. But I'm not sure exactly how it best can be utilized. Do you happen to know of some formats that stores info about bad sectors?
I am glad you are positive about this feature. Unfortunately I don't of any existing format -- but well, if it does not exists yet, time to be the first :-)
Bad sectors cannot be read from the disc (by definition), so when making an image, most of the burning software fill them with dummy data. If the software/image format supports reading raw data (e.g. 2352 bytes of sector data), the dummy error detection/error correction codes don't correspond to the dummy data, which also gives a bad sector in an image file (and, if you burn such image in raw mode, you also get bad sectors on the resulting disc).
So, if an image contains error detection/error correction codes and not only user data, bad sectors can already be identified. I've modified the daemon to support detection of such and trigger read errors on identified bad sectors.
ISO images, however, contain only 2048 bytes of user data, without edc/ecc. As you say, it might be possible to identify bad sectors via additional file, although I am reluctant to implement such as better solutions already exist - namely, making your backups in image format that supports raw sectors (e.g. toc/bin with cdrdao)