Nix Binary Cache

Avrea provides a Nix binary cache endpoint that acts as a substituter. Store paths built on one run are available to all subsequent runs without rebuilding.

Work in progress

Nix binary cache support is functional but the setup is not yet fully automatic. Most CI environments use install-nix-action, which overwrites nix.conf on install. You need to re-add the substituter configuration after Nix is installed. This will get easier in a future update.

On Avrea runners

The Nix substituter needs to be configured after Nix is installed, because install-nix-action overwrites nix.conf. Add a step to append the cache configuration:

workflow.yml

jobs:
  build:
    runs-on: avrea-ubuntu-latest
    steps:
      - uses: actions/checkout@v6

      - name: Configure Avrea nix binary cache
        run: |
          cat << 'NIXCONF' | sudo tee -a /etc/nix/nix.conf > /dev/null
          trusted-users = root runner
          substituters = http://avrea-host:8290/nix-build/cache https://cache.nixos.org
          trusted-substituters = http://avrea-host:8290/nix-build/cache https://cache.nixos.org
          require-sigs = false
          NIXCONF
          sudo systemctl restart nix-daemon

      - name: Build
        run: nix build --no-link .#default

      - name: Push to Avrea binary cache
        run: nix copy --to http://avrea-host:8290/nix-build/cache .#default

Note

The nix copy step pushes newly built store paths to the cache. Use a flake reference (e.g. .#default) rather than ./result so the command works with --no-link. Paths already in the cache are substituted automatically on future builds.

Manual setup

- name: Configure Avrea nix binary cache
  run: |
    cat << 'NIXCONF' | sudo tee -a /etc/nix/nix.conf > /dev/null
    trusted-users = root runner
    substituters = http://avrea-host:8290/nix-build/cache https://cache.nixos.org
    trusted-substituters = http://avrea-host:8290/nix-build/cache https://cache.nixos.org
    require-sigs = false
    NIXCONF
    sudo systemctl restart nix-daemon

- run: nix build --no-link .#default
- run: nix copy --to http://avrea-host:8290/nix-build/cache .#default