nix-tutorial

What is nix?

Nix is a package manager, like apt,yum,dnf,pip, etc. It can be installed in any operating system, although there is a Linux distribution that uses it by default: NixOS.

When installed independently, it doesn't interfere with the system's package manager (e.g. apt), as it uses a separate directory for everything: /nix.

Why nix?

It allows for creating reproducible environments. This means that once someone creates a development environment, its configuration can be shared with other developers on the team, and have it work exactly the same way!

This has multiple benefits:

• Each developer doesn't need to struggle with installing every package one-by-one from their distribution's repositories, take care of incompatible versions, missing packages, add third-party repositories (e.g PPAs for Ubuntu), etc
• Easy on-boarding: new contributors can start working right away!

Why not...

• Docker/Podman:
  • It's not reproducible!
    • The versions for every package installed depends on what was available the day the image was built. Some distribution package managers support version pinning, but that might not always work as expected.
    • Nix references packages not only by version, but also by the hash of its contents, and one can also even reference the nixpkgs repository's snapshot at a specific point in time (it's a git repository == commit!). This also means that multiple versions of the same package can be installed at the same time.
  • Inconvenient for everyday use: A large image will take a few seconds to start; the user needs to mount every directory needed as volumes; UID, file permissions and ownership inconsistencies; the user's system's familiar shell configuration, aliases, and utilities, are not available inside the container, etc
• pip:
  • Is language-specific; nix can manage everything, so the way it is used across e.g. an organization would be more uniform and familiar across projects
  • It isn't able to install system utilities, compilers, etc (which some pypi packages need during installation!)
• chroot/lxc containers
  • Harder to use for a development workflow
  • Similar problems with Docker/Podman

Install

nix

The recommended way is:

sh <(curl --proto '=https' --tlsv1.2 -L https://nixos.org/nix/install) --daemon

If you encounter any issues during installation, for example if your Linux distribution uses SELinux, you can try the single-user installation:

sh <(curl --proto '=https' --tlsv1.2 -L https://nixos.org/nix/install) --no-daemon

or Determinate nix, a nix distribution (!= Linux distribution):

curl -fsSL https://install.determinate.systems/nix | sh -s -- install --determinate

devbox

As using nix by its own can be daunting for new users, we can use devbox (think of it as a wrapper for nix, which can be used like python/pip but for any package we need!)

nix profile install nixpkgs#devbox

Using devbox

To create a devbox configuration:

cd project
devbox init

To manage your project's dependencies:

devbox add gcc@4.9.4
devbox list
devbox rm gcc
devbox add gcc

You can search for packges on nixhub, or directly from the terminal:

devbox search numpy
devbox add python313Packages.numpy

Then, enter the environment with:

devbox shell

devbox also supports various programming languages. For example, Python: once you add it as a dependency, devbox will also manage and activate a Python virtual environment for you:

devbox add python@3.6.12
devbox add gcc git ipcalc
devbox shell
pip install numpy
pip install -r requirements.txt

Bonus use-cases

devbox can also be used with direnv:

nix profile install nixpkgs#direnv
cd project
devbox generate direnv

Then, after you also configure your shell, the environment is activated automatically when you enter a project:

cd project
make

You could also use devbox as a general package manager, without needing to devbox shell in a project to keep software available:

devbox global add ripgrep vim git
devbox global list

The same is possible with a nix command (although devbox might still seem easier for beginners):

nix profile install nixpkgs#wget

You can search nix packages to find the name of a package you want to install