pyrox.dev
1---
2title: Introduction
3author: Frederik Rietdijk
4date: 2015-11-25
5---
6
7# Introduction
8
9The Nix Packages collection (Nixpkgs) is a set of thousands of packages for the
10[Nix package manager](http://nixos.org/nix/), released under a
11[permissive MIT/X11 license](https://github.com/NixOS/nixpkgs/blob/master/COPYING).
12Packages are available for several platforms, and can be used with the Nix
13package manager on most GNU/Linux distributions as well as NixOS.
14
15This manual primarily describes how to write packages for the Nix Packages collection
16(Nixpkgs). Thus it’s mainly for packagers and developers who want to add packages to
17Nixpkgs. If you like to learn more about the Nix package manager and the Nix
18expression language, then you are kindly referred to the [Nix manual](http://nixos.org/nix/manual/).
19
20## Overview of Nixpkgs
21
22Nix expressions describe how to build packages from source and are collected in
23the [nixpkgs repository](https://github.com/NixOS/nixpkgs). Also included in the
24collection are Nix expressions for
25[NixOS modules](http://nixos.org/nixos/manual/index.html#sec-writing-modules).
26With these expressions the Nix package manager can build binary packages.
27
28Packages, including the Nix packages collection, are distributed through
29[channels](http://nixos.org/nix/manual/#sec-channels). The collection is
30distributed for users of Nix on non-NixOS distributions through the channel
31`nixpkgs`. Users of NixOS generally use one of the `nixos-*` channels, e.g.
32`nixos-16.03`, which includes all packages and modules for the stable NixOS
3316.03. The purpose of stable NixOS releases are generally only given
34security updates. More up to date packages and modules are available via the
35`nixos-unstable` channel.
36
37Both `nixos-unstable` and `nixpkgs` follow the `master` branch of the Nixpkgs
38repository, although both do lag the `master` branch by generally
39[a couple of days](http://howoldis.herokuapp.com/). Updates to a channel are
40distributed as soon as all tests for that channel pass, e.g.
41[this table](http://hydra.nixos.org/job/nixpkgs/trunk/unstable#tabs-constituents)
42shows the status of tests for the `nixpkgs` channel.
43
44The tests are conducted by a cluster called [Hydra](http://nixos.org/hydra/),
45which also builds binary packages from the Nix expressions in Nixpkgs for
46`x86_64-linux`, `i686-linux` and `x86_64-darwin`.
47The binaries are made available via a [binary cache](https://cache.nixos.org).
48
49The current Nix expressions of the channels are available in the
50[`nixpkgs-channels`](https://github.com/NixOS/nixpkgs-channels) repository,
51which has branches corresponding to the available channels.