Deploy with NixOps

1. Bootstrap

Create a folder called mycompany-agents with a file:

  hercules-ci-agent =
      builtins.fetchTarball "";
  network.description = "Hercules CI agents";

  agent = {
    imports = [
      (hercules-ci-agent + "/module.nix")

    services.hercules-ci-agent.enable = true;
    services.hercules-ci-agent.concurrentTasks = 4; # Number of jobs to run
    deployment.keys."cluster-join-token.key".keyFile = ./cluster-join-token.key;
    deployment.keys."binary-caches.json".keyFile = ./binary-caches.json;

2. Pick provisioning target

Choose between backends. NixOps can deploy to:

An example physical specification:

  agent = {
    deployment.targetHost = ""; # Your agent's IP address running NixOS

3. Get a cluster join token.

  1. In the dashboard, find the account for which you would like to deploy the agent,

  2. Click the "Agents" button and the button in "Generate token" tab. This produces a private token that should be protected like a password.

  3. Copy the token into a plain text file /var/lib/hercules-ci-agent/secrets/cluster-join-token.key.

4. Configure a binary cache

Write a file binary-caches.json in the same directory as hercules-ci-agents.nix.

On Cachix you can create a binary cache. After you complete the process, gather the keys into a binary-caches.json file, replacing all placeholders:

{ "mycache": (1)
    { "kind": "CachixCache"
    , "authToken": "eyJhaf23GH53a.bc23BUSI.9q3048hWHh" (2)
    , "publicKeys": [""] (3)
    , "signingKeys": ["uAhqM3jG..."] (4)
1 The name of the Cachix cache; for example the mycache part from
2 Optional; only required for private binary caches. You may retrieve this from the Cachix Getting started instructions, step 3.
3 The public part of the signing key. Look for "Public Key" on your cache page (example page:
4 A cache-specific secret key to sign store paths. You can find it in ~/.config/cachix/cachix.dhall or your key backup after following the setup instructions on Make sure you copy the right key if you have multiple in your cachix.dhall.
For more detail, see The binary-caches.json format in the Reference.
Although a single-agent "cluster" works with an empty {} cache configuration, we highly recommend setting up a cache from the start. Running without a cache will break some features and will cause unexpectedly long build times due to automatic garbage collection.

5. Deploy

To avoid compiling the agent you can use binary cache to speed it up:

$ nix-env -iA cachix -f
$ cachix use hercules-ci

Deploy using:

$ nix-shell -p nixops -I nixpkgs=
$ nixops create -d my-agent ./hercules-ci-agents.nix ./hercules-ci-agents-target.nix
$ nixops deploy -d my-agent

The agent will start working as soon as the deployment has succeeded and builds are queued.

6. Repository Setup

The goal of this step is to make sure everything is set up correctly.


To inspect the agent’s local log, run nixops ssh agent journalctl -u hercules-ci-agent -n 100 to see the last 100 lines.