Nix ecosystem

The Core Nix Ecosystem is a collection of technologies designed to reproducibly build and declaratively configure and manage packages and systems as well as their dependencies. It achieves this by translating the functional paradigm from the program to the system domain by utilizing a dynamic, functional and lazy DSL called the Nix Language for specifying reproducible builds.

In addition there are many other applications (Extended Nix Ecosystem) developed by the Nix community, utilizing and supporting these core technologies.

Official ecosystem

Core Components of the Nix Ecosystem

Component	Manual	Description	Use	License
NixOS	NixOS Manual	A Linux distribution with all components built by Nix, and thus supporting reproducible and declarative system-wide configuration management as well as atomic upgrades and rollbacks.	Declaratively configure desktops, servers & clusters	MIT
Nixpkgs	Nixpkgs Manual	The largest community maintained Nix package and NixOS module repository; standard releases of NixOS are hosted here.	Share Nix packages & NixOS modules	MIT
Hydra	Hydra Manual	A Nix based continuous build system.	CI build farms	GPL-3.0
Nix	Nix Manual	A package manager that parses Nix expressions specifying reproducible build, putting the result in a store address with a hash of the dependency tree, sidestepping dependency hell and supporting multiversion installs and rollbacks.	Reproducible builds & package management in Linux & Darwin	LGPL-2.1

The NixOS core ecosystem stack

NixOS A Linux distribution and configuration system built using Nixpkgs.
Nixpkgs A large, community-maintained repository of packages.	Hydra A continuous build system built on Nix.
Nix A pure and functional build system.

Usage of NixOS

Users install the NixOS distribution on their computers just as any other Linux distribution. They read about packages to install and configuration options in Nixpkgs via https://search.nixos.org and this wiki. They use the Nix language to declaratively describe in a text file what software packages should be installed and how the system should be configured. They run 2 command line programs in a terminal to transform the system into the described system. They use the system as any other Linux system.

Development of NixOS

Developers of NixOS mainly work on Nixpkgs. NixOS development itself is compromised of three large areas as well as some others which are smaller by volume (but no less important). The major ones include packaging, the module system, and documentation. Packaging is done in Nixpkgs and is not exclusive to NixOS or even Linux-based platforms. Maintainers of packages which are not exclusive to NixOS (such as tooling required to run the distribution itself) usually take care of multiple platforms although not strictly required. The module system is the way in which services running on NixOS are primarily configured. This area stretches from "low-level" configuration such as systemd unit files or providing custom kernel configuration up to configuration file generation for specific services. The module system is the primary way for users to configure NixOS, and lives in the nixos/ subdirector of Nixpkgs. Documentation is largely embedded in packaging and module system data, although free-standing markdown files are also contained in the Nixpkgs repository. Documentation also includes maintaining the website, Wiki, and other aspects of the wider ecosystem. The first two categories are almost exclusively Nix language code written in text files, while the latter is a mix of Nix code, markdown files, and various other formats. All contributions to Nixpkgs, regardless of whether they affect NixOS or not, are subject to peer review before being integrated into Nixpkgs. Many packages alongside documentation and supplementary materials such as ISOs or tarballs are pre built on Hydra to reduce the update time for NixOS users. Those three categories are largest by contribution volume, however many maintainers also engage in activities surrounding the NixOS foundation, maintaining the infrastructure on which website, Hydra, and other tools run on, or developing tooling required for NixOS.

Various examples of NixOS development along with links.

Type of development	Location of Development	Examples
Platform Agnostic Packaging	Nixpkgs	coreutils package, stdenv framework, Libreoffice package
Platform Agnostic Tooling	Nixpkgs and various repositories	upstream/default Nix implementation (CppNix), Hydra source code, Nixpkgs merge bot
NixOS Tooling	mostly Nixpkgs	nixos-rebuild-ng source code, NixOS Installation ISOs
NixOS Module System	Nixpkgs	Display Manager configuration, MySQL (and derivative) database configuration
Infrastructure		Infrastructure for this Wiki, NixOS infra
Documentation		This Wiki, stdenv documentation, NixOS IPv6 configuration (visible in the IPv6 section of the NixOS manual), Nixpkgs Contribution Guidelines
Tech Organisation		NixOS RelEng, Nix and NixOS RFCs
Other		NixOS artwork, NixOS (and related) discourse, NixOS Foundation

See also: Nix organisation repository