Nix - Build the same thing at any time

Nix gives us the ability to build Docker image with minimum deterministic by providing some solid mechanisms.

Firstly, using Nix, we can specify exactly the version of each package and its dependencies, and keep it completely the same each time the package build happens. It is called reproducible build.

To achieve it, Nix originally combined two mechanisms, Pinning nixpkgs and Fixed-output derivation.

• Pinning nixpkgs
• Fixed-output derivation

Above is not all. Nix raised a new feature called Flake that has input and output that are determined exactly. To do it, Flake defines a standard structure for a Nix project where input (dependencies) and output are specified and locked. So your build now can avoid the dependency on the global state of Nix.