When I was working on Othernet (www.othernet.is), I wanted to do Over-The-Air updates of our firmware. Over a unidirectional, slow (~20kbps), broadcast satellite link with significant packet dropout this was quite a challenge. Amongst the many tools that helped in making it work was diffoscope. I used it to make our buildroot-based firmware have deterministic, minimal-diff build, thus reducing the amount of update I needed to send out.

For a few weeks, I simply iterated between building the firmware, using diffoscope to diff the new build against a previous build to find what files changed and where, fix buildroot packages to eliminate these file changes whereever possible, lather-rinse-repeat.

In the end I was able to reduce our OTA update sizes to a typical 20-50KB (base, compressed firmware image as 30MB).

Fun times!