Finding the Hyper-V .vhdx file format specifications

I recently found myself looking at the various files generated by Hyper-V virtualization, and for testing automation purposes, it would be great to be able to "inject" files into existing virtual disk files. Well, this of course, would require quite a lot of code, but the idea is nifty.

For this research project I wanted to find the specifications for the .vhdx virtual disk file format, and luckily because of the Microsoft Open Source Promise (OSP) initiative, these were pretty easy to find. In case you don't want to wander around, here's the direct link to the specifications.

Understanding the file format requires knowledge of how hard disks operate, as the format itself is "close to metal" in the sense that it works based on sectors and not individual files. In any case, it's interested reading, even though you don't specifically have a need to tinker deeper.