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Create a private network using Clique

A private network provides a configurable network for testing. This private network uses the Clique (proof of authority) consensus protocol.

danger

The steps in this tutorial create an isolated, but not protected or secure, Ethereum private network. We recommend running the private network behind a properly configured firewall.

Prerequisites​

Steps​

Listed on the right-hand side of the page are the steps to create a private network using Clique.

1. Create directories​

Each node requires a data directory for the blockchain data. When the node starts, Besu saves the node key in this directory.

Create directories for your private network, each of the three nodes, and a data directory for each node:

Clique-Network/
├── Node-1
│   ├── data
├── Node-2
│   ├── data
└── Node-3
    ├── data

2. Get the address for Node-1​

In Clique networks, you must include the address of at least one initial signer in the genesis file. For this Clique network, we'll use Node-1 as the initial signer. This requires obtaining the address for Node-1.

To get the address for Node-1, in the Node-1 directory, use the public-key export-address subcommand to write the node address to the specified file (node1Address in this example).

besu --data-path=data public-key export-address --to=data/node1Address

3. Create the genesis file​

The genesis file defines the genesis block of the blockchain (that is, the start of the blockchain). The Clique genesis file includes the address of Node-1 as the initial signer in the extraData field.

All nodes in a network must use the same genesis file.

Copy the following genesis definition to a file called cliqueGenesis.json and save it in the Clique-Network directory:

{
  "config": {
    "chainId": 1337,
    "berlinBlock": 0,
    "clique": {
      "blockperiodseconds": 15,
      "epochlength": 30000
    }
  },
  "coinbase": "0x0000000000000000000000000000000000000000",
  "difficulty": "0x1",

  "extraData": "0x0000000000000000000000000000000000000000000000000000000000000000<Node 1 Address>0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
  "gasLimit": "0xa00000",
  "mixHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "nonce": "0x0",
  "timestamp": "0x5c51a607",
  "alloc": {
    "fe3b557e8fb62b89f4916b721be55ceb828dbd73": {
      "privateKey": "8f2a55949038a9610f50fb23b5883af3b4ecb3c3bb792cbcefbd1542c692be63",
      "comment": "private key and this comment are ignored.  In a real chain, the private key should NOT be stored",
      "balance": "0xad78ebc5ac6200000"
    },
    "627306090abaB3A6e1400e9345bC60c78a8BEf57": {
      "privateKey": "c87509a1c067bbde78beb793e6fa76530b6382a4c0241e5e4a9ec0a0f44dc0d3",
      "comment": "private key and this comment are ignored.  In a real chain, the private key should NOT be stored",
      "balance": "90000000000000000000000"
    },
    "f17f52151EbEF6C7334FAD080c5704D77216b732": {
      "privateKey": "ae6ae8e5ccbfb04590405997ee2d52d2b330726137b875053c36d94e974d162f",
      "comment": "private key and this comment are ignored.  In a real chain, the private key should NOT be stored",
      "balance": "90000000000000000000000"
    }
  }
}
note

We recommend specifying the latest milestone when creating the genesis file for a private network. This ensures you are using the most up-to-date protocol and have access to the most recent opcodes.

In extraData, replace <Node 1 Address> with the address for Node-1, excluding the 0x prefix.

{
  ...
"extraData":"0x0000000000000000000000000000000000000000000000000000000000000000b9b81ee349c3807e46bc71aa2632203c5b4620340000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
  ...
}
warning

Do not use the accounts in alloc in the genesis file on Mainnet or any public network except for testing. The private keys display, which means the accounts are not secure.

4. Start the first node as the bootnode​

Start Node-1:

besu --data-path=data --genesis-file=../cliqueGenesis.json --network-id 123 --rpc-http-enabled --rpc-http-api=ETH,NET,CLIQUE --host-allowlist="*" --rpc-http-cors-origins="all"

The command line enables:

When the node starts, the enode URL displays. Copy the enode URL to specify Node-1 as the bootnode in the following steps.

Node 1 Enode URL

5. Start Node-2​

Start another terminal, change to the Node-2 directory and start Node-2 specifying the Node-1 enode URL copied when starting Node-1 as the bootnode:

besu --data-path=data --genesis-file=../cliqueGenesis.json --bootnodes=<Node-1 Enode URL> --network-id 123 --p2p-port=30304 --rpc-http-enabled --rpc-http-api=ETH,NET,CLIQUE --host-allowlist="*" --rpc-http-cors-origins="all" --rpc-http-port=8546

The command line specifies:

  • A different port to Node-1 for P2P discovery using the --p2p-port option.
  • A different port to Node-1 for HTTP JSON-RPC using the --rpc-http-port option.
  • The enode URL of Node-1 using the --bootnodes option.
  • The data directory for Node-2 using the --data-path option.
  • Other options as for Node-1.

6. Start Node-3​

Start another terminal, change to the Node-3 directory and start Node-3 specifying the Node-1 enode URL copied when starting Node-1 as the bootnode:

besu --data-path=data --genesis-file=../cliqueGenesis.json --bootnodes=<Node-1 Enode URL> --network-id 123 --p2p-port=30305 --rpc-http-enabled --rpc-http-api=ETH,NET,CLIQUE --host-allowlist="*" --rpc-http-cors-origins="all" --rpc-http-port=8547

The command line specifies:

  • A different port to Node-1 and Node-2 for P2P discovery using the --p2p-port option.
  • A different port to Node-1 and Node-2 for HTTP JSON-RPC using the --rpc-http-port option.
  • The data directory for Node-3 using the --data-path option.
  • The bootnode as for Node-2.
  • Other options as for Node-1.

7. Confirm the private network is working​

Start another terminal, use curl to call the JSON-RPC API net_peerCount method and confirm the nodes are functioning as peers:

curl -X POST --data '{"jsonrpc":"2.0","method":"net_peerCount","params":[],"id":1}' localhost:8545

The result confirms Node-1 has two peers (Node-2 and Node-3):

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x2"
}

Next steps​

Look at the logs displayed to confirm Node-1 is producing blocks and Node-2 and Node-3 are importing blocks.

Use the Clique API to add Node-2 or Node-3 as a signer.

note

To add Node-2 or Node-3 as a signer you need the node address as when specifying Node-1 as the initial signer.

Import accounts to MetaMask and send transactions, as described in the Quickstart tutorial.

info

Besu doesn't support private key management.

Stop the nodes​

When finished using the private network, stop all nodes using ++ctrl+c++ in each terminal window.

tip

To restart the Clique network in the future, start from 4. Start First Node as Bootnode.