There are several RPIs hosting an (always identical) custom set of software, and it's configuration. Each RPI runs binaries, triggers shell scripts, has configs, and any or all of those moving parts may have to be updated over the Internet at any point.
Basically, I'm tying to automate someone coming over to each RPI, swapping the SD card with an updated one, and rebooting the device.
There must be a solution already. I found this question, this article, a mention of Docker; there's too many options and I'm confused. Is virtualisation what I'm looking for?
I was hoping the updates could be incremental, because any RPI may be on cellular connection.
Please guide me in what direction to research.