Create Your Own Ethereum Blockchain

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Setting up and exploring a private Ethereum blockchain is an excellent way to understand how decentralized networks operate under the hood. Whether you're a developer, blockchain enthusiast, or someone looking to experiment with smart contracts in a safe environment, building your own Ethereum test network using Geth offers invaluable hands-on experience.

Geth (Go Ethereum) is one of the most widely used Ethereum clients, implemented in the Go programming language. It enables users to run a full Ethereum node, interact with the Ethereum Virtual Machine (EVM), deploy smart contracts, and even mine Ether — all within a controlled private network. This guide walks you through setting up your own private Ethereum blockchain step by step.

Why Build a Private Ethereum Blockchain?

A private blockchain gives you complete control over the network configuration. Unlike the public Ethereum mainnet, where consensus is decentralized and gas fees apply, a private chain allows:

This makes it ideal for development, education, and enterprise use cases.

Prerequisites

Before diving in, ensure you have:

While Geth can be installed on macOS and other Linux distributions, Ubuntu provides the smoothest experience with minimal dependency issues. For Mac users, consider running Ubuntu via VirtualBox or another virtualization tool.

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Setting Up Ubuntu (Optional for Mac Users)

If you're on macOS, follow these steps:

  1. Download and install VirtualBox.
  2. Download the latest Ubuntu Desktop ISO from ubuntu.com.
  3. Create two virtual machines in bridged network mode so each gets its own IP address.
  4. Install Ubuntu on both VMs.

Alternatively, you can use cloud services like AWS EC2 to spin up Ubuntu instances quickly. Just make sure to use at least a t2.large instance — the free-tier t2.micro lacks sufficient resources and will prevent Geth from mining blocks effectively.

Installing Geth on Ubuntu

Once your environment is ready, install Geth using the official PPA:

sudo add-apt-repository -y ppa:ethereum/ethereum
sudo apt update
sudo apt install ethereum -y

Verify the installation:

geth version

You should see output showing the Geth version, architecture, and commit hash.

Initializing the Private Blockchain

The next step is creating a custom genesis block, which defines the initial state and rules of your blockchain.

Create a directory for your project:

mkdir ~/my-ethereum-chain
cd ~/my-ethereum-chain

Now create a genesis.json file:

{
  "config": {
    "chainId": 15,
    "homesteadBlock": 0,
    "eip150Block": 0,
    "eip155Block": 0,
    "eip158Block": 0,
    "byzantiumBlock": 0,
    "constantinopleBlock": 0,
    "petersburgBlock": 0,
    "istanbulBlock": 0,
    "muirGlacierBlock": 0,
    "berlinBlock": 0,
    "londonBlock": 0,
    "clique": {
      "period": 15,
      "epoch": 30000
    }
  },
  "difficulty": "1",
  "gasLimit": "8000000",
  "alloc": {}
}
Note: This configuration uses Clique consensus, ideal for private networks with a single or few validators.

Initialize the blockchain:

geth init genesis.json --datadir ./data

This creates the necessary data structure inside the ./data folder.

Starting Your Ethereum Node

Launch your node with the following command:

geth \
  --datadir ./data \
  --networkid 15 \
  --http \
  --http.addr 0.0.0.0 \
  --http.port 8545 \
  --http.api eth,net,web3,personal \
  --allow-insecure-unlock \
  --nodiscover \
  --syncmode 'full' \
  --gcmode 'archive'

Key flags explained:

Your node is now running! You’ll see logs indicating block creation and peer activity.

Creating an Account and Mining Ether

Open a new terminal and attach to the running Geth instance:

geth attach http://127.0.0.1:8545

Inside the Geth JavaScript console:

// Create a new account
personal.newAccount("your-password")

// List accounts
eth.accounts

// Start mining (replace with your account address)
miner.setEtherbase(eth.accounts[0])
miner.start(1)

Wait a few seconds — you should start seeing mined blocks and increasing balance:

// Check balance
web3.fromWei(eth.getBalance(eth.accounts[0]), "ether")

Stop mining when done:

miner.stop()

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Deploying a Simple Smart Contract (Optional)

With your node active and Ether available, try deploying a basic smart contract using Remix IDE or Truffle. Connect Remix to your node via Web3 Provider at http://<your-vm-ip>:8545.

Ensure port 8545 is open and accessible from external machines if connecting remotely.

Frequently Asked Questions (FAQ)

What is Geth used for?

Geth is an Ethereum client that implements the Ethereum protocol in Go. It allows you to run a full Ethereum node, interact with the blockchain, mine Ether, deploy smart contracts, and support decentralized applications (dApps).

Can I run Geth on Windows?

Yes, Geth supports Windows, but Ubuntu is recommended for tutorials due to fewer dependency conflicts and better community support. Use WSL2 (Windows Subsystem for Linux) for optimal performance.

Why isn’t my node mining blocks?

Common causes include insufficient system resources (especially on AWS t2.micro), incorrect etherbase setup, or missing API permissions. Ensure your account is set as miner.setEtherbase() and APIs like personal are enabled.

Is it safe to use --allow-insecure-unlock?

It’s acceptable in local development environments but never in production. This flag allows unlocking accounts over HTTP, posing a security risk if exposed publicly.

How do I connect MetaMask to my private chain?

In MetaMask:

  1. Go to Networks > Add Network

  2. Enter:

    • Network Name: My Private Chain
    • RPC URL: http://<your-node-ip>:8545
    • Chain ID: 15
    • Currency Symbol: ETH
  3. Import an account using the private key from your Geth node.

Can multiple nodes join my private network?

Yes! Run additional Geth nodes with the same genesis file and use admin.addPeer() to connect them via enode URLs. Ensure all required ports are open across machines.

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Final Thoughts

Building your own Ethereum blockchain with Geth demystifies core concepts like consensus, account management, mining, and smart contract deployment. It's a powerful foundation for anyone entering blockchain development or exploring enterprise-grade decentralized solutions.

By following this guide, you’ve created a fully functional private Ethereum network — perfect for learning, testing, or prototyping dApps in a secure environment.

As blockchain technology evolves, mastering tools like Geth ensures you stay ahead in the rapidly growing Web3 ecosystem. Whether you're preparing for mainnet deployments or experimenting with Layer-2 solutions, hands-on experience remains invaluable.

Remember: Always secure your private keys, avoid exposing RPC endpoints publicly, and never reuse test accounts on mainnet.

Now that your node is live — what will you build next?