Deploy with NixOps

1. Bootstrap

Create a folder called mycompany-agents with a file:

  network.description = "Hercules CI agents";

  agent = {
    services.hercules-ci-agent.enable = true;

    deployment.keys."cluster-join-token.key" = {
      user =;
      destDir = clusterJoinTokenDir;
      keyFile = ./cluster-join-token.key;
    deployment.keys."binary-caches.json" = {
      user =;
      destDir = binaryCachesDir;
      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. Select your deployment method, select the Generate a token tab and use the button.

  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.

Although a single agent works with empty {} binary 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 eventual garbage collection.

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 Omit if you use a local signing key. Required if you use a Write token. You can retrieve one from cachix, click a cache, click per cache auth token. Select Write permission and generate a key. If you can only select Read permission, you have to ask a cache admin for a Write token or, if applicable, for the signing key.
3 The public part of the signing key. Look for "Public Key" on your cache page (example page:
4 Omit if you use a Write token. Otherwise, this is the 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.

5. Deploy

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.