Nix (package manager): Difference between revisions

{{Disambiguation|message=This article is about the Nix package manager. Not to be confused with the [[Nix ecosystem]], the [[Nix (language)|Nix language]] or the [[Nix (command)|Nix command]].}}

Nix is a package manager and build system that parses reproducible build instructions specified in the [[Nix Expression Language]], a pure functional language with lazy evaluation. Nix expressions are pure functions<ref>Values cannot change during computation. Functions always produce the same output if their input does not change. </ref>taking dependencies as arguments and producing a ''[[Derivations|derivation]]'' specifying a reproducible build environment for the package. Nix stores the results of the build in unique addresses specified by a hash of the complete dependency tree, creating an immutable package store (aka the [[#Nix store|nix store]]) that allows for atomic upgrades, rollbacks and concurrent installation of different versions of a package, essentially eliminating [https://en.wikipedia.org/wiki/Dependency_hell dependency hell].  

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On [[NixOS]], Nix is automatically installed.

On other Linux distributions or on macOS, you can install Nix following the [https://nixos.org/manual/nix/stable/installation/installation installation section of the Nix manual].

The [[Nix (command line utilities)|Nix commands]] are documented in the [https://nixos.org/manual/nix/stable/command-ref/command-ref Nix reference manual]: main commands, utilities and experimental commands. Prior to version 2.0 (released in February 2018) there have been different commands.

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On NixOS, Nix can be configured using the [https://search.nixos.org/options?query=nix. <code>nix</code> option].  

Standalone Nix is configured through <code>nix.conf</code> (usually found in <code>/etc/nix/</code>). Details on the available options are [https://nixos.org/manual/nix/stable/command-ref/conf-file found in the Nix reference manual].  

You can also configure Nix using [[Home Manager]], which manages declarative environments for a single user. For system-wide configuration, you can use [https://github.com/numtide/system-manager System Manager] on Linux and [https://github.com/LnL7/nix-darwin nix-darwin] on macOS.

When sandbox builds are enabled, Nix will setup an isolated environment for each build process. It is used to remove further hidden dependencies set by the build environment to improve reproducibility. This includes access to the network during the build outside of <code>fetch*</code> functions and files outside the Nix store.  Depending on the operating system access to other resources are blocked as well (ex. inter process communication is isolated on Linux); see [https://nixos.org/nix/manual/#sec-conf-file nix.conf section] in the Nix manual for details.

In pull requests for [https://github.com/NixOS/nixpkgs/ Nixpkgs] people are asked to test builds with sandboxing enabled (see <code>Tested using sandboxing</code> in the pull request template) because in [https://nixos.org/hydra/ official Hydra builds] sandboxing is also used.

* [https://cs.tvl.fyi/depot/-/tree/tvix tvix]

* [https://lix.systems/ lix]

Earlier attempts can be found on [https://riir-nix.github.io/ riir-nix]