Deploy with NixOS

NixOS deployment can be performed on the target machine itself or remotely by means of nixos-rebuild --target-host.

These instructions will use /etc/nixos as the location for the configuration modules. This directory is only used at evaluation time. If you perform remote deployment, you will use some project directory in place of /etc/nixos.

1. Bootstrap

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

$ nix-env -iA cachix -f https://cachix.org/api/v1/install
$ cachix use hercules-ci

Add this configuration to /etc/nixos/configuration.nix:

{
  imports = [
    ( builtins.fetchTarball "https://github.com/hercules-ci/hercules-ci-agent/archive/stable.tar.gz"
      + "/module.nix"
    )
  ];

  services.hercules-ci-agent.enable = true;
  services.hercules-ci-agent.concurrentTasks = 4; # Number of jobs to run
}

2. 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.

3. Configure a binary cache

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:

binary-caches.json
{ "mycache": (1)
    { "kind": "CachixCache"
    , "authToken": "eyJhaf23GH53a.bc23BUSI.9q3048hWHh" (2)
    , "publicKeys": ["mycache.cachix.org-1:EjBSHzF6VmDnzqlldGXbi0RM3HdjfTU3yDRi9Pd0jTY="] (3)
    , "signingKeys": ["uAhqM3jG..."] (4)
    }
}
1 The name of the Cachix cache; for example the mycache part from mycache.cachix.org.
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: https://mycache.cachix.org).
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 cachix.org. 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.

Copy or move the binary-caches.json file into /var/lib/hercules-ci-agent/secrets/.

Make sure that /var/lib/hercules-ci-agent/secrets and its contents can only be read by hercules-ci-agent.

4. Activation

Apply the configuration by running nixos-rebuild switch.

5. Repository Setup

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

Troubleshooting

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