3. Look up the tar file format specifications, it is actually a
relatively simple file format and you will need to understand it
to do the manual data rescue. In particular, you will need to
understand the PAX and GNU extensions to the format.
This is one of the first things that came to my mind. So far I know of the following sources of information:
- The GNU Tar documentation and source code
- Schily's star documentation and source code
**If you know of any other source code of specifications I should be aware of, please let me know.**
P.S. I just realized something that is probably quite relevant. That .tar file that has been corrupted was probably originally created with Mac OS X Tar. This makes sense considering that this is the machine I was backing up, and there are tell-tale signs and strings of "Mac OS X formatedness" in the .tar file, such as "com.apple.acl.text", "Mac OS X", and various permissions clues that indicate the original tar file was created on a Mac OS X machine.
This means that the original implementation of Tar *may* have been derived from BSD Tar (I have both GNU Tar and stock system Tar installed on that machine). So this gives me yet another set of specifications to look through.
There was a messy point in history, years ago, when BSD Tar was patched on Darwin/Mac OS X to store resource forks. I think (hope) those days are hopefully now behind us. I will ask around in Darwin/Mac OS X hacker groups to see if I can get any further information.