In order to start the node, you first need to gather the blockchain information you need to connect to.

1. the hash of the genesis block of the blockchain, this will be the source of truth of the blockchain. It is 64 hexadecimal characters.
2. the trusted peers identifiers and access points.

These information are essentials to start your node in a secure way.

The genesis block is the first block of the blockchain. It contains the static parameters of the blockchain as well as the initial funds. Your node will utilise the Hash to retrieve it from the other peers. It will also allows the Node to verify the integrity of the downloaded genesis block.

The trusted peers are the nodes in the public network that your Node will trust in order to initialise the Peer To Peer network.

The node configuration

Your node configuration file may look like the following:

Note

This config shouldn't work as it is, the ip address and port for the trusted peer should be those of an already running node. Also, the public_address ('u.x.v.t') should be a valid address (you can use an internal one, eg: 127.0.0.1). Furthermore, you need to have permission to write in the path specified by the storage config.

storage: "/mnt/cardano/storage"

rest:
listen: "127.0.0.1:8443"

p2p:
trusted_peers:
- id: 1
topics_of_interest:
messages: low
blocks: normal


Description of the fields:

• storage: (optional) Path to the storage. If omitted, the blockchain is stored in memory only.
• log: (optional) Logging configuration:
• level: log messages minimum severity. If not configured anywhere, defaults to "info". Possible values: "off", "critical", "error", "warn", "info", "debug", "trace".
• format: Log output format, plain or json.
• output: Log output destination. Possible values are:
• stdout: standard output
• stderr: standard error
• syslog: syslog (only available on Unix systems)
• journald: journald service (only available on Linux with systemd, (if jormungandr is built with the systemd feature)
• gelf: Configuration fields for GELF (Graylog) network logging protocol (if jormungandr is built with the gelf feature):
• backend: hostname:port of a GELF server
• log_id: identifier of the source of the log, for the host field in the messages.
• rest: (optional) Configuration of the REST endpoint.
• listen: address:port to listen for requests
• pkcs12: (optional) Certificate file
• p2p: P2P network settings
• trusted_peers: (optional) the list of nodes to connect to in order to bootstrap the P2P topology (and bootstrap our local blockchain);
• public_id: (optional) the public identifier sent to the other nodes in the P2P network. If not set it will be randomly generated.
• public_address: multiaddr string specifying address of the P2P service. This is the public address that will be distributed to other peers of the network that may find interest in participating to the blockchain dissemination with the node.
• topics_of_interest: The dissemination topics this node is interested to hear about:
• messages: Transactions and other ledger entries. Typical setting for a non-mining node: low. For a stakepool: high;
• blocks: Notifications about new blocks. Typical setting for a non-mining node: normal. For a stakepool: high;

Starting the node

jormungandr --config config.yaml --genesis-block-hash 'abcdef987654321....'


The 'abcdef987654321....' part refers to the hash of the genesis, that should be given to you from one of the peers in the network you are connecting to.

In case you have the genesis file (for example, because you are creating the network) you can get this hash with jcli.

cat block-0 | jcli genesis hash


or, in case you only have the yaml file

cat genesis.yaml | jcli genesis encode | jcli genesis hash