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webuhu/elixir_nix_example.json
{
  "createdAt": "2019-07-22T14:51:43Z",
  "defaultBranch": "main",
  "description": null,
  "fullName": "webuhu/elixir_nix_example",
  "homepage": null,
  "language": "Nix",
  "name": "elixir_nix_example",
  "pushedAt": "2021-12-15T09:23:34Z",
  "stargazersCount": 32,
  "topics": [],
  "updatedAt": "2025-10-31T14:47:33Z",
  "url": "https://github.com/webuhu/elixir_nix_example"
}

Elixir (Phoenix) Nix Example

Section titled “Elixir (Phoenix) Nix Example”

Example repo to show off how I use Nix as build environment for Elixir / Phoenix projects.
Important Nix stuff is located within flake.nix / default.nix & pkg/ folder.
This repo is not a working project! It just contains parts of the workflow.

Note

Since starting this example a lot of positive things have happened or are happening within Nixpkgs. You may be interested in mixRelease or friends.

I for myself stopped to use a full Nix leveraging build setup. I only use parts of this workflow anymore with reusing local _build & deps as it speeds up things for my requirements enorm.

Setup

Section titled “Setup”

This repo provides an easy environment setup by the usage of Nix (w/ flakes enabled).
Nix currently runs on Linux and macOS.

Enabling Nix flakes (Nix v2.4)

~/.config/nix/nix.conf
experimental-features = nix-command flakes

By using Nix, beside Nix nothing else needs to be installed manually.

Windows
Recommended also using Nix within a Linux Virtual Machine or WSL 2.

Manual Setup

Section titled “Manual Setup”

For maintaining simplicity, instructions for a manual setup isn’t part of this readme.
Anyway, required dependencies:

Development

Section titled “Development”

Environment

Section titled “Environment”
Terminal window
# Enter shell w/ development environment + temporary PostgreSQL database
nix develop


# Run commands without shell
nix develop --command <command>

Basics commands for working with Elixir / Phoenix

Section titled “Basics commands for working with Elixir / Phoenix”
Terminal window
# Get Elixir mix deps
mix deps.get


# Get JS packages
npm install --prefix assets


# Start Phoenix server
mix phx.server


# Start Elixir application
mix run --no-halt


# Enter IEx
iex -S mix


# Run tests
mix test

Build

Section titled “Build”
Terminal window
# mix deps
nix build --file default.nix mix_deps --relaxed-sandbox


# JS packages
nix build --file default.nix node_modules --relaxed-sandbox


# Compile
nix build --file default.nix mix_build --relaxed-sandbox


# Compile cacheable `_build`
nix develop --command mix compile


# Generate docs using `mix docs`
nix build --file default.nix docs --relaxed-sandbox


# Build production release using `mix release`
nix build --file default.nix release --relaxed-sandbox

Maintenance

Section titled “Maintenance”
Terminal window
# Update pinned Nix pkgs
elixir pkg/scripts/pkgs_update.exs
# Update flake.lock
nix flake update


# Check / update / clean Mix deps
mix hex.outdated
mix deps.update --all
mix deps.clean --unlock --unused


# Check / update / clean NPM packages
npm outdated --prefix assets
npm update --prefix assets
npm prune --prefix assets


# Flake checks
nix flake check

direnv

Section titled “direnv”

direnv let’s you automatically load environment variables per directory defined in .envrc.

Working with direnv

Terminal window
# Install via Nix
nix profile install nixpkgs#direnv


# Setup hook
# Add the following to your .profile
eval "$(direnv hook bash)"