NixOS

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Continuous Integration with GitHub Actions

This tutorial guides you through a few short steps to start using GitHub Actions as your CI for commits and pull requests.

Caching builds using Cachix

One nice benefit of Nix is that CI can build and cache developer environments for every project on every branch using binary caches.

Another important aspect of CI is the feedback loop of how many minutes does the build take to finish.

Using Cachix you’ll never have to waste building any derivation twice and you’ll share built derivations with all your developers.

After each job, just built derivations are pushed to your binary cache.

Before each job, derivations to be built are first substituted (if they exist) from your binary cache.

1. Creating your first binary cache

It’s recommended to have different binary caches per team, depending who will have write/read access to it.

Fill out the form on create binary cache page.

On your freshly created binary cache, follow Push binaries tab instructions.

2. Setting up secrets

On your GitHub repository or organization (for use across all repositories):

  1. Click on Settings

  2. Click on Secrets.

  3. Add your previously generated secrets (CACHIX_SIGNING_KEY and/or CACHIX_AUTH_TOKEN).

Setting up GitHub Actions

Create .github/workflows/test.yml with:

name: "Test"
on:
  pull_request:
  push:
jobs:
  tests:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v2.3.4
    - uses: cachix/install-nix-action@v12
      with:
        nix_path: nixpkgs=channel:nixos-unstable
    - uses: cachix/cachix-action@v8
      with:
        name: mycache
        # If you chose signing key for write access
        signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
        # If you chose API tokens for write access OR if you have a private cache
        authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
    - run: nix-build
    - run: nix-shell --run "echo OK"

Once you commit and push to your GitHub repository, you should see status checks appearing on commits and PRs.

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