Nix

Nix is a functional programming language and Nix-Cli(aka nix) is a declarative package manager designed to create reproducible and declarative software environments. It works by treating configurations as code, ensuring that every aspect of your environment is consistent, version-controlled, and isolated. One of Nix’s standout features is its ability to manage software dependencies seamlessly while maintaining exact version control.

Key Concepts of Nix

• Declarative Configurations: Environments and configurations are defined in .nix files, making them reproducible.

• Immutable Packages: Nix stores packages in a unique, hashed location /nix/store/$hash-$packagename, ensuring no conflicts between versions where $hash represents the hash id of the package and $packagename refers to the name of the package itself. For example, if I do the follwing in my terminal:

  $ nix-shell -p gcc
  

  Nix would go and evaluate the package derivation from nixpkgs and store it in /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0

  NOTE: /nix/store is an immutable file-system which means the user can only access it read-only.

• Version Locking: Using tools like flakes or nixpkgs, you can pin specific versions of packages for consistent builds.

What is nixpkgs?

nixpkgs is a central repository that contains thousands of software packages available in Nix. It acts as the foundation for most Nix-based configurations and is continuously updated to include new packages and fixes. You can view the repo in GitHub.

$ nix-shell -p neovim git

This command starts a bash shell environment with neovim and git installed, without affecting your system configuration.

What is flakes?

Flakes are an experimental feature that enhances reproducibility by locking dependencies and configurations in a standardized format. It is intended to replace default.nix which you would normally use in a Nix system. This brings a new schema where you can define your packages from the web in inputs and build package or a shell for the user. You could say that flakes work similar to the Rust package manager cargo or Javascript package manager npm which locks your dependencies in a separate file (Cargo.lock and packages-lock.json respectively), flake.lock in this case.

# flake.nix
{
    description = "An example NixOS configuration";

    inputs = {
        nixpkgs = { url = "github:nixos/nixpkgs/nixos-unstable"; };
        nur = { url = "github:nix-community/NUR"; };
    };

    outputs = inputs: {
        nixosConfigurations = {
            mysystem = inputs.nixpkgs.lib.nixosSystem {
                system = "x86_64-linux";
                modules = [ ./configuration.nix ];
                specialArgs = { inherit inputs; };
            };
        };
    };
}

This allow user to use flakes to build a system configuration using nixosConfigurations defined in the flake.nix.

You can learn more about nix and flakes by referring to resources