Recall, the Dockerfile syntax is 'imperative'. If we change the order of the commands in the Dockerfile, we likely end up with a different image. In the Nix ex

Recall, the Dockerfile syntax is 'imperative'. If we change the order of the commands in the Dockerfile, we likely end up with a different image. In the Nix example, the image we build is in the expression `nix2container.buildImage { ... }`. The `nginxWebRoot` is the package with the index.html: nginxWebRoot = pkgs.writeTextDir "index.html" '' <html><body><h1>Hello from NGINX</h1></body></html> ''; It's reasonable to say "writeTextDir" modifies the disk. I don't think it's reasonable to say just because changes in state occur that the code is imperative. (e.g. SQL is a declarative language, but clearly allows modifying the database). Similarly: nginxVar = pkgs.runCommand "nginx-var" {} '' mkdir -p $out/var/log/nginx mkdir -p $out/var/cache/nginx ''; We can say the contents of the runCommand argument are run imperatively, sure. (Especially: if you change the order of the bash commands, you might get a different result). But unlike the Dockerfile, the order where we declare this nginxVar package doesn't matter. Or, say: the `copyToRoot` in the `nix2container.buildImage` takes in a list of packages where the contents are copied to root. The copying is an action; but the list of what to copy is not an action. -- And again, `copyToRoot` could be put after the `config` attribute. The mechanisms describing how the copying is done is elsewhere.