Using Nix with Gitea Actions

Carl Sagan once said, “If you wish to make an apple pie from scratch, you must first invent the universe.” In the world of software, creating a reproducible build environment is the universe you need to invent. This post will walk you through using Nix in tandem with Gitea Actions to make that universe a reality for your projects.

I am an enthusiastic user of Nix and am a maintainer of several packages. I appreciate the reproducibility of the binaries it offers across different systems and its rapid update cycle.

Gitea Actions is a CI/CD solution that can run your build and deployment tasks. Using Nix within Gitea Actions is as straightforward as adding a few lines to your workflow file. Here’s how:

name: nix

on:
  push:

jobs:
  lint-backend:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Install dependencies for Nix setup action
        run: |
          apt update -y
          apt install sudo -y                    
      - uses: cachix/install-nix-action@v27
        with:
          nix_path: nixpkgs=channel:nixos-unstable
      - name: Test running command with Nix
        run: nix-shell -p hello --run "hello"

This workflow will install Nix and then execute the hello command. Note that we need to install sudo, as it is a prerequisite for the cachix/install-nix-action and is not present in the default Gitea Actions runner image. If you’re using a custom runner that already has sudo installed, feel free to skip that step.

Regarding the Nix package channel, I prefer to live on the bleeding edge with nixpkgs=channel:nixos-unstable. However, you’re free to pin to a more stable channel if you wish. The cachix/install-nix-action Action does not have a channel configured by default, so you must specify one.

If you haven’t explored Nix yet, I highly recommend you do so. It’s a powerful tool for creating consistent and reproducible build environments.