# Starting a passive node

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:


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)
• syslogudp: remote syslog (only available on Unix systems)
• host: address and port of a syslog server
• hostname: hostname to attach to syslog messages
• 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.
• file: path to the log file.
• rest: (optional) Configuration of the REST endpoint.
• listen: address:port to listen for requests
• tls: (optional) enables TLS and disables plain HTTP if provided
• cert_file: path to server X.509 certificate chain file, must be PEM-encoded and contain at least 1 item
• priv_key_file: path to server private key file, must be PKCS8 with single PEM-encoded, unencrypted key
• cors: (optional) CORS configuration, if not provided, CORS is disabled
• allowed_origins: (optional) allowed origins, if none provided, echos request origin
• max_age_secs: (optional) maximum CORS caching time in seconds, if none provided, caching is disabled
• p2p: P2P network settings
• trusted_peers: (optional) the list of nodes's multiaddr with their associated public_id to connect to in order to bootstrap the P2P topology (and bootstrap our local blockchain);
• public_id: (optional) the node's public ID that will be used to identify this node to the network.
• 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.
• listen_address: (optional) multiaddr specifies the address the node will listen to to receive p2p connection. Can be left empty and the node will listen to whatever value was given to public_address.
• 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.
• max_connections: The maximum number of simultaneous P2P connections this node should maintain.
• explorer: (optional) Explorer settings
• enabled: True or false
• no_blockchain_updates_warning_interval: (optional, seconds) if no new blocks were received after this period of time, the node will start sending you warnings in the logs.

## 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 block-0.bin, because you are creating the network) you can get this hash with jcli.

jcli genesis hash --input block-0.bin


or, in case you only have the yaml file

jcli genesis encode --input genesis.yaml | jcli genesis hash