NixCon 2025 in Rapperswil-Jona, Switzerland
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Declarative builds
and deployments.
Nix is a tool that takes a unique approach to package management and system configuration. Learn how to make reproducible, declarative and reliable systems.
$ # Typing "nix-shell -p ..." each time can be tedious. We can do better. $ # We can write everything down in shell.nix $ cat -n shell.nix 1 { 2 pkgs ? import <nixpkgs> { }, # here we import the nixpkgs packages 3 }: 4 # mkShell is a helper function 5 pkgs.mkShell { 6 name = "dev-environment"; # that requires a name 7 buildInputs = [ 8 # and a list of packages 9 pkgs.nodejs 10 ]; 11 shellHook = '' 12 # bash to run when you enter the shell 13 echo "Start developing..." 14 ''; 15 } $ # This snippet provides a developer environment named "dev-environment" $ # with the node command line tool available $ # and which will print "Start developing..." on first start. $ # To enter this developer environment, run: $ nix-shell
Reproducible
Nix builds packages in isolation from each other. This ensures that they are reproducible and don’t have undeclared dependencies, so if a package works on one machine, it will also work on another.
Declarative
Nix makes it trivial to share development and build environments for your projects, regardless of what programming languages and tools you’re using.
Reliable
Nix ensures that installing or upgrading one package cannot break other packages. It allows you to roll back to previous versions, and ensures that no package is in an inconsistent state during an upgrade.
Choose from Thousands of Packages
The Nix Packages collection (Nixpkgs) is a set of over 120 000 packages for the Nix package manager.
Examples
Try new tools without fear
$ # Lets see if python is present on the system $ python --version python: command not found $ # Use nix-shell to create a shell environment with python $ nix-shell -p python3 (nix-shell) $ python --version Python 3.7.7 (nix-shell) $ # YAAAY! Python is available (nix-shell) $ exit $ # And this is how you create on demand environments
Multiple languages, one tool
$ # Lets create an environment with multiple packages $ nix-shell -p python3 nodejs go rustc (nix-shell) $ node --version v10.20.1 (nix-shell) $ go version go version go1.14.1 linux/amd64 (nix-shell) $ rustc --version rustc 1.42.0 (nix-shell) $ # Imagine how easy (nix-shell) $ exit $ # And POOF, just like that you are back to your normal environment after $ # playing aro
Declarative dev-environments
2 pkgs ? import <nixpkgs> { }, # here we import the nixpkgs packages 3 }: 4 # mkShell is a helper function 5 pkgs.mkShell { 6 name = "dev-environment"; # that requires a name 7 buildInputs = [ 8 # and a list of packages 9 pkgs.python3 10 pkgs.python3Packages.virtualenv 11 pkgs.nodejs 12 pkgs.yarn 13 ]; 14 shellHook = '' 15 # bash to run when you enter the shell 16 echo "Start developing..." 17 ''; 18 } $ # Pause the video to read and understand the shell.nix $ # To enter the dev-environment simply run: $ nix-shell Start developing... (nix-shell) $ python --version Python 3.7.7 (nix-shell) $ vi
Minimal docker images
$ # We all love docker. But over time it can become tedious to write $ # reliable docker files. $ # What if you could use the power of Nix to build Docker images? $ cat -n docker.nix 1 { 2 pkgs ? import <nixpkgs> { system = "x86_64-linux"; }, # nixpkgs package set 3 }: 4 # helper to build Docker image 5 pkgs.dockerTools.buildLayeredImage { 6 name = "nix-hello"; # give docker image a name 7 tag = "latest"; # provide a tag 8 contents = [ pkgs.hello ]; # packages in docker image 9 } $ # Pause the video to read and understand the docker.nix $ # Now we build a Docker imag
Declarative cloud images
$ # How hard would it be to build and configure an Amazon EC2 image? $ # Let us configure a Nginx to serve a "Welcome to nginx!" page, with a $ # valid SSL certificate (via LetsEncrypt) and recommended security settings $ cat -n amazon.nix 1 { pkgs, ... }: 2 { 3 security.acme.acceptTerms = true; 4 security.acme.email = "nix@example.com"; 5 services.nginx = { 6 enable = true; 7 recommendedGzipSettings = true; 8 recommendedOptimisation = true; 9 recommendedProxySettings = true; 10 recommendedTlsSettings = true; 11 virtualHosts."example.com" = { 12 enableACME = true; 13 forceSSL = true; 14 locations."/".root = "${pkgs.nginx}/html"; 15 }; 16 }; 17 } $ # Pause the video to understand t
Test your configurations
$ # In this example we will look into how to test your NixOS configuration $ # We will create a simple configuration with the `hello` package installed $ # system wide and check that the `hello` world binary works. $ cat -n test.nix 1 { 2 pkgs ? import <nixpkgs> { }, 3 }: 4 pkgs.nixosTest { 5 name = "example-test"; 6 # virtual machine with one package installed system wide 7 machine = 8 { pkgs, ... }: 9 { 10 environment.systemPackages = [ pkgs.hello ]; 11 }; 12 testScript = '' 13 # run hello on machine and check for output 14 machine.succeed('hello | grep "Hello, world!"') 15 # test is a simple python script 16 ''; 17 } $ # Pause the video to understand the t