Configuring a node

The node should run successfully with the default configuration settings. However, if you need to change the node configuration, you can edit the configuration.yaml file that the --config flag points to. Ensure that the RequiresMagic parameter is set correctly for testnet usage.

A Cardano node uses three .json files to define its configuration:

  • config.json
  • topology.json
  • genesis.json


This file defines what a node does, and includes the following four sub sections:

  • Basic node configuration
  • Update parameters
  • Tracing
  • Logging control

Basic node configuration

This declares the basic node configuration parameters (TPraos as the protocol, the correct path to the ff-genesis.json file, and RequiresMagic for testnet use).

The basic configuration section might look like this:

  "Protocol": "TPraos",
  "GenesisFile": "ff-genesis.json",
  "RequiresNetworkMagic": "RequiresMagic",

Update parameters

Block-producing nodes use a protocol version number as part of the system for the agreement and synchronization of protocol updates. When configuring this section, you need to be aware of the latest version of the protocol supported by the network.

The update parameters section might look like this:

  "ApplicationVersion": 0,
  "LastKnownBlockVersion-Alt": 0,
  "LastKnownBlockVersion-Major": 0,
  "LastKnownBlockVersion-Minor": 0,


Tracers tell the node what information you are interested in when logging. For example, switches that you can turn ON or OFF according to the type and quantity of information that you are interested in. This provides fairly coarse-grained control, but it is relatively efficient at filtering out unwanted trace output.

You can learn more information about tracing here.

Logging control

It is possible to have more fine-grained control over filtering of trace output, and to match and route trace output to particular backends. This is less efficient than the coarse trace filters, but offers precise control options.


The information contained in this file tells the node which nodes in the network it should talk to.

A simple topology file might look like this:

  "Producers": [
      "addr": "x.x.x.x",
      "port": 3001,
      "valency": 1


The genesis file is generated with the cardano-cli by reading a genesis.spec.json file.

The genesis file is very important, as it sets four key parameters:

  • genDelegs: maps from genesis keys to genesis delegates.
  • initialFunds: maps from the initial addresses to the initial values at those addresses.
  • MaxLovelaceSupply: the total amount of lovelaces in the blockchain.
  • startTime: the time of slot zero.

For details on using the command line interface, stopping and starting the node, and ensuring the node is connected to the Cardano network, please refer to the README file.

Last updated: May 6, 2020 10:17 UTC