Setting Up a Private Blockchain with Geth: A Step-by-Step Guide

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Introduction

This tutorial will guide you through creating your own private Ethereum blockchain using Geth. Before proceeding, ensure you have foundational knowledge in blockchain technology and a configured Golang environment.

Prerequisites

Part 1: Creating the Private Chain

Step 1: Genesis Block Setup

The Genesis Block is the starting point of your blockchain. Configure a unique genesis.json file to define initial parameters (chain ID, consensus rules, etc.). Example structure:

{
  "config": {
    "chainId": 12345,
    "homesteadBlock": 0,
    "eip150Block": 0
  },
  "difficulty": "0x400",
  "gasLimit": "0x8000000",
  "alloc": {}
}

👉 Learn more about Genesis configurations

Part 2: Initializing the Blockchain

  1. Create a data directory:

    mkdir ~/private-chain/data

  2. Initialize Geth with the Genesis file:

    geth --datadir ~/private-chain/data init genesis.json
  3. Verify the output directories (geth/ for chain data, keystore/ for accounts).

Part 3: Launching the Node

Run the node with:

geth --datadir ~/private-chain/data --networkid 12345 --http --allow-insecure-unlock

Key Notes:

Part 4: Verifying Success

After launch, check logs for:

INFO [02-01|13:45:00] HTTP server started endpoint=http://127.0.0.1:8545

This confirms your private chain is active!

FAQ Section

Q1: Why use a private blockchain?

A1: Private chains enable custom testing, smart contract development, and controlled transactions without public network fees.

Q2: How do I add nodes?

A2: Share the genesis.json and use the same networkid across nodes.

Q3: Can I mine on a private chain?

A3: Yes! Configure miners via Geth flags (--mine).

Conclusion

Now you can mine, transact, and deploy smart contracts on your private chain. Explore advanced features like connecting MetaMask or deploying DApps.

👉 Advanced Geth configurations

References