Because Dockerfiles delegate all the complexity to a package manager (apt, apk, ...), which has its own languages (eg. debian/rules for apt). Using Docker with

Because Dockerfiles delegate all the complexity to a package manager (apt, apk, ...), which has its own languages (eg. debian/rules for apt). Using Docker without any package manager doing this job would be a completely different story. And btw, you can also use Nix to build docker images. For example, here is what would be the equivalent of a Dockerfile but with Nix: https://nixos.org/nixpkgs/manual/#ex-dockerTools-buildImage https://nixos.org/nixpkgs/manual/#ex-dockerTools-buildImage > the DockerFiles themselves can also describe a reproducible process It's trickier. You need to pin all versions of all packages you use, even indirect dependencies.