Ethereum Private Chain Setup, Genesis Block Creation, and Smart Contract Deployment

1. Ethereum Installation, Private Chain Genesis Block Setup, and Node Addition

1.1 Ethereum Installation

Official Download Link: Geth Ethereum

Download the appropriate Geth version for your OS. Verify installation by checking the version:

geth version  

1.2 Private Chain Genesis Block Setup

1. Create genesis.json:

   {  
     "config": {  
    "chainId": 15,  
    "homesteadBlock": 0,  
    "eip150Block": 0,  
    "eip155Block": 0,  
    "eip158Block": 0  
     },  
     "difficulty": "0x400",  
     "gasLimit": "0x8000000",  
     "alloc": {}  
   }  

2. Initialize Genesis Block:

   geth --datadir "./chain" init ./genesis.json  

3. --datadir: Specifies blockchain data storage location.

4. Start Private Chain:

   geth --datadir "./chain" --nodiscover console 2>> eth_output.log  

5. --nodiscover: Ensures the chain remains private.
6. Monitor logs: tail -f eth_output.log (Windows users need Tail.exe).

7. Account Management:

   personal.newAccount("password") // Create account  
   eth.accounts // List accounts  
   web3.fromWei(eth.getBalance(eth.accounts[0]), "ether") // Check balance  

8. Mining:

   miner.start(1) // Start mining  
   miner.stop() // Stop mining  

1.3 Adding Nodes to the Private Chain

1. Retrieve First Node’s enode URL:

   admin.nodeInfo.enode  

2. Initialize Second Node:

   geth --datadir "./chain2" init ./genesis.json  
   geth --datadir "./chain2" --port 30305 --nodiscover console  

3. Connect Nodes:

   admin.addPeer("enode://<first-node-id>@127.0.0.1:30303")  

4. Verify Connection:

   net.peerCount // Should return 1  

2. Explanation of getBlock Fields

| Field | Description |
|--------|-------------|
| difficulty | Block mining difficulty (adjusts dynamically). |
| extraData | Custom metadata or notes. |
| gasLimit | Max gas allowed per block. |
| hash | Block’s unique hash. |
| miner | Miner’s address (reward recipient). |
| nonce | Proof-of-Work hash. |
| transactions | List of transactions or hashes. |

👉 Explore Ethereum development tools

3. Log Output Interpretation

• Startup Logs: Configuration, protocol initialization, memory allocation.

• Mining Logs:

  • Generating DAG: Directed Acyclic Graph creation for mining.
  • Successfully sealed new block: New block confirmed.
• Transactions: Submitted transaction indicates broadcasted TX.

4. Smart Contract Deployment

1. Write a Simple Contract (e.g., Solidity):

   pragma solidity ^0.8.0;  
   contract SimpleCalc {  
     function f(uint a, uint b) public pure returns (uint) {  
    return a * b;  
     }  
   }  

2. Compile in Remix: Copy WEB3DEPLOY code.

3. Deploy via Geth:

   personal.unlockAccount(acc0, "password")  
   miner.start(1)  
   // Paste WEB3DEPLOY code  

4. Success: Contract mined! appears.

5. Call Contract Function:

   SimpleCalc.f(3, 8) // Returns 24  

5. Transaction Field Breakdown

• blockHash: Parent block’s hash.
• gasPrice: Gas cost per unit (wei).
• input: Data for contract calls/deployment.
• value: Transferred Ether (wei).

👉 Master Ethereum transactions

6. Quick Command Reference

| Command | Purpose |
|---------|---------|
| geth init | Initialize genesis block. |
| miner.start() | Begin mining. |
| eth.sendTransaction() | Send Ether. |

FAQ

Q1: How do I resolve ‘DAG generation’ delays?
A1: DAG generates once per epoch (~30,000 blocks). Pre-download it using geth makedag.

Q2: Why is my transaction pending?
A2: Ensure the sender’s account is unlocked and has sufficient gas.

Q3: How to secure a private chain?
A3: Use --nodiscover and restrict RPC access (--rpcapi).