Getting Started With Nix

Nix

Nix is a declarative package manager that enables users to declare the desired system state in configuration files(declarative configuration), and it takes responsibility for achieving that state.

Prerequisites

• curl Supported Platform:
• Linux (i686, x86_64, aarch64).
• macOS (x86_64, aarch64).

Installation

Multi Users

This option requires either:

• Linux running systemd, with SELinux disabled
• MacOS

  bash <(curl -L https://nixos.org/nix/install) --daemon
  mkdir /nix
  chown $USER /nix
  

Single User

Single-user is not supported on Mac.

bash <(curl -L https://nixos.org/nix/install) --no-daemon

Verify installation:

nix --version

Using Nix with Docker

docker run -ti nixos/nix

Install Global Packages

nix-env -i --attr nixpkgs.nodejs

node -v
v18.17.1

which node
/root/.nix-profile/bin/node

Uninstall Global Packages

nix-env --uninstall nodejs
uninstalling 'nodejs-18.17.1'

Update the channels

nix-channel --update nixpkgs
nix-env --upgrade '*'

Rollback

nix-env --rollback

Delete unused packages

We should run it periodically.

nix-collect-garbage --delete-old

Nix Shell(Without install)

You can use Nix packages without installing them globally on your machine. This is a good way to bring in the tools you need for individual projects.

nix-shell -p powershell
[nix-shell:~]# pwsh
PowerShell 7.3.4
PS /root>

Set up a development environment

Let’s build a Python web application using the Flask web framework as an exercise.

For our Flask web application, create a new file called myapp.py and add the following code:

#! /usr/bin/env python

from flask import Flask

app = Flask(__name__)

@app.route("/")
def hello():
    return {
        "message": "Hello, Nix!"
    }

def run():
    app.run(host="0.0.0.0", port=5000)

if __name__ == "__main__":
    run()

This is a simple Flask application which serves a JSON document with the message “Hello, Nix!”.

To declare the development environment, create a new file shell.nix:

{ pkgs ? import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/eabc38219184cc3e04a974fe31857d8e0eac098d.tar.gz") {} }:

pkgs.mkShell {
  packages = [
    (pkgs.python3.withPackages (ps: [
      ps.flask
    ]))

    pkgs.curl
    pkgs.jq
  ];
}

We can now use nix-shell to launch the shell environment we just declared:

nix-shell
python ./myapp.py

Launch a new terminal to start another session:

nix-shell
curl 127.0.0.1:5000 | jq '.message'

Uninstallation

Single User

rm /nix

Multi Users

sudo systemctl stop nix-daemon.service
sudo systemctl disable nix-daemon.socket nix-daemon.service
sudo systemctl daemon-reload

sudo rm -rf /etc/nix /etc/profile.d/nix.sh /etc/tmpfiles.d/nix-daemon.conf /nix ~root/.nix-channels ~root/.nix-defexpr ~root/.nix-profile

Remove build users and their group:

for i in $(seq 1 32); do
  sudo userdel nixbld$i
done
sudo groupdel nixbld

MacOS

https://nixos.org/manual/nix/stable/installation/uninstall#macos