This directory does contain an example configuration to run a cardano-node, hydra-node and the example hydraw application on a NixOS host.

It is not using fancy NixOps or proper NixOS services, but the basic declarative virtualisation.oci-containers NixOS options to make it very similar to the docker-compose way of orchestrating the containers.

Add & start containers

To use this, copy or symlink the hydraw.nix module and import it into your NixOS' configuration.nix:

{ config, pkgs, lib, ... }:

{
  imports = [
    ./hydraw.nix
  ];

  # ... the rest of your configuration.nix
}

Then, after the next nixos-rebuild switch, the relevant docker containers should be started by systemd and you can see their logs in either:

journalctl -u docker-cardano-node.service
docker logs cardano-node

Copying credentials

As not everything is automated yet, we will need to copy the configured credentials of hydraw.nix to the target host and create relevant directories. For example using ssh and scp with hostname example:

ssh example "mkdir -p /data/cardano-node /data/hydra-node/credentials"
scp sebastian.cardano.sk sebastian.hydra.sk example:/data/hydra-node/credentials/

Also copy any additional Hydra verification keys into the /data/hydra-node/credentials and extend the command line of the hydra-node container accordingly.

Lastly, the hydra-node requires some protocol-parameters.json to configure the ledger in the /data/hydra-node directory. Use the ones from the e2e tests hydra-cluster/config/protocol-parameters.json or the L1 ones via the cardano-cli on the target host as basis:

ssh example "CARDANO_NODE_SOCKET_PATH=/data/cardano-node/node.socket cardano-cli query protocol-parameters --testnet-magic 2 | 's/"txFeeFixed.*/"txFeeFixed": 0,/;s/"txFeePerByte.*/"txFeePerByte": 0,/' > /data/hydra-node/protocol-parameters.json"

IMPORTANT: The hydraw application requires 0 fees! So ensure "txFeeFixed": 0 and "txFeePerByte": 0.

Attach the tui

For this, we do not need a service definition, but can simply use docker via SSH:

ssh -t example docker run --rm -it \
  -v /data:/data \
  --network host \
  ghcr.io/cardano-scaling/hydra-tui \
  --connect 0.0.0.0:4001 \
  --node-socket /data/cardano-node/node.socket \
  --testnet-magic 2 \
  --cardano-signing-key /data/hydra-node/credentials/sebastian.cardano.sk

Fuel up and open a head

To continue, you will need to have some "fuel" UTxO owned by the --cardano-signing-key available to the hydra-node. See testnet instructions on how to do that.

Then, we can open the Head usin the TUI and commit some funds into it. If you have other participants in the head with you, they will need to commit something (or opt for nothing).

Once open, we can use the web interface of hydraw at port 1337 of your target or via a reverse proxy as in the example module to paint pixels!