Geth

geth is the the command line interface for running a full ethereum node implemented in Go.

Install geth

First we need to install geth on our Ubuntu machine. These steps are from the documentation: https://github.com/ethereum/go-ethereum/wiki/Installation-Instructions-for-Ubuntu

sudo apt-get install software-properties-common
sudo add-apt-repository -y ppa:ethereum/ethereum
sudo apt-get update
sudo apt-get install ethereum

Next we need to initialise the private blockchain with a genesis block.

mkdir MyPrivateNetwork
touch genesis.json

{
    "nonce": "0x0000000000000042",
    "mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000",
    "difficulty": "0x400",
    "alloc": {},
    "timestamp": "0x0",
    "parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
    "extraData": "0x",
    "gasLimit": "0x8000000",
    "config": {}
}

Now we’re ready to initialise the blockchain.
geth --datadir MyPrivateNetwork init genesis.json

Start a node with geth

geth --identity "MyPrivateNetwork" --cache 6000 --port 3000 --networkid 58342 --nodiscover --datadir="MyPrivateNetwork" --maxpeers=0 --rpc --rpcport 8545 --rpcaddr 0.0.0.0 --rpccorsdomain "*" --rpcapi "db,eth,net,web3,personal,web3" console 2>>geth.log

After starting the geth node you should see something like IPC endpoint opened:
/home/someone/privchain/geth.ipc

Console access

geth attach ipc:/root/MyPrivateNetwork/MyPrivateNetwork/geth.ipc

Logs

bash tail -f geth.log

Account management

---

coinbase

web3.eth.coinbase

newAccount()

personal.newAccount('your-password')

listAccounts()

personal.listAccounts

unlockAccount()

personal.unlockAccount(web3.eth.coinbase, "password", 15000)

checkAllBalances()

Print all balances with a JavaScript function:

function checkAllBalances() {
    var totalBal = 0;
    for (var acctNum in eth.accounts) {
        var acct = eth.accounts[acctNum];
        var acctBal = web3.fromWei(eth.getBalance(acct), "ether");
        totalBal += parseFloat(acctBal);
        console.log("  eth.accounts[" + acctNum + "]: \t" + acct + " \tbalance: " + acctBal + " ether");
    }
    console.log("Total balance: " + totalBal + " ether");
}

That can then be executed with:

checkAllBalances()

Mining

---

set Ether base account for mining

miner.setEtherbase(web3.eth.coinbase)
miner.start(2)

Smart Contract Deploying

---

1. Using Truffle Framework
2. Using Mist v0.9

1. Truffle Framework

---

Requires NodeJS 5.0+, MacOS, Linux or Windows**

Truffle is a world class development environment, testing framework and asset pipeline for Ethereum, aiming to make life as an Ethereum developer easier. With Truffle, you get:

• Built-in smart contract compilation, linking, deployment and binary management.
• Automated contract testing for rapid development.
• Scriptable, extensible deployment & migrations framework.
• Network management for deploying to any number of public & private networks.
• Package management with EthPM & NPM, using the ERC190 standard.
• Interactive console for direct contract communication.
• Configurable build pipeline with support for tight integration.
• External script runner that executes scripts within a Truffle environment.

npm install -g truffle

Create a project

mkdir myproject
cd myproject
truffle init

Using Minimum Viable Token from ethereum.org

The token contract is quite complex. But in essence a very basic token boils down to this:

contract MyToken {
    /* This creates an array with all balances */
    mapping (address => uint256) public balanceOf;

    /* Initializes contract with initial supply tokens to the creator of the contract */
    function MyToken(
        uint256 initialSupply
        ) {
        balanceOf[msg.sender] = initialSupply;              // Give the creator all initial tokens
    }

    /* Send coins */
    function transfer(address _to, uint256 _value) {
        if (balanceOf[msg.sender] < _value) throw;           // Check if the sender has enough
        if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
        balanceOf[msg.sender] -= _value;                     // Subtract from the sender
        balanceOf[_to] += _value;                            // Add the same to the recipient
    }
}

Compiling and deploying

truffle compile
truffle migrate
or
truffle migrate --network remotehost

Using the console

truffle console

truffle.js

module.exports = {
      rpc: {
            host: "GETH_REMOTE_ADDR",
            port: 8545
      },
      networks: {
        localhost: {
            host: "GETH_REMOTE_ADDR",
            port: 8545,
            network_id: 58342,
            gasPrice: 30000000,
            gas: 30000000
        },
        live: {
            host: "localhost", 
            port: 8545,
            network_id: 1,
            gasPrice: 3000,
            from: "0x058f862dea3e18b1da307f59fdc7e94a560279bc"
        }
    }
};

truffle compile
truffle migrate --network localhost

Troubleshooting

• Deploying Migrations...
  Error encountered, bailing. Network state unknown. Review successful transactions manually.
  Error: authentication needed: password or unlock

In the geth console, enter the following to unlock the default account, ensuring to replace password with the value entered when the account was created previously.
personal.unlockAccount(web3.eth.coinbase, "password", 15000)

• Deploying Migrations...
  Error encountered, bailing. Network state unknown. Review successful transactions manually.
  Error: Insufficient funds for gas * price + value

Start mining
miner.setEtherbase(web3.eth.coinbase)
miner.start(2)

2. Mist v0.9

---

For macOS

cd /Applications
cd Ethereum\ Wallet.app/
cd Contents
cd MacOS
ls
./Ethereum\ Wallet --rpc http://GETH_REMOTE_ADDR:8545 --networkid 58342 --node-ipcpath /root/MyPrivateNetwork/geth.ipc

Use the interface

Useful links

The Five Types Model