There probably should be an addendum to the "12-factor app" movement that says that the environment should be treated as read only for the duration of the proce

There probably should be an addendum to the "12-factor app" movement that says that the environment should be treated as read only for the duration of the process. Most of the issues people talk about here seem to relate to people trying to abuse the environment as some kind of key value store for mutable global state (which sounds like a bad idea). Why would you even want to do that?! Being on the JVM which actually treats the environment as immutable that and which probably inspired a lot of the 12 factor app movement (with companies like Soundcloud being big Scala and Java users and pushing this), I've never experienced any issues with the environment changing on me or causing any threading issues. The environment is effectively immutable and there's nothing in my processes that sneakily circumvents that (via some native calls into libc). So, complete non issue on the JVM. Even if somebody manages to modify the environment, the immutable copy stays the same. That copy gets created on JVM startup and is immutable. Anything using normal Java apis to interact with the environment will never see the modification. I'm sure people might have tried to work around that but it's not a wide spread practice. Because, again, why would you even want to do that? The problem with configuration files is that their parsing is process specific. That's why Linux/Unix is such a mess. Every single tool seems to have its own conventions and mechanisms for configuration. There are no standards for this. Other of course than the Docker ecosystem. You can do whatever you want inside the container but effectively your only interface to the outside world is either messily mounting some volume and doing whatever convoluted way of configuration your app requires; or just using environment variables. Most modern software is docker ready/friendly in the sense that you can fully control their behavior via the environment. It's perfectly adequate for most things that people run via docker these days. Which of course is pretty much anything. And of course with Docker compose or kubernetes (which I'm not necessarily a fan of) you get yaml files defining lists of environment variables that define how your process starts. So you more or less get what you are asking for. I'm not a big YAML fan but it works well enough. Too much potential for syntax issues really ruining your day IMHO. But it's not like the alternatives are free of issues.