Tuesday, June 27, 2017

Ethereum Dev Chain - Private Chain

To develop and test an Ethereum smart contract we need a test network. The easiest way is go get spin off our own test chain with sufficient amount ethers. Below are the steps for spinning a development chain.

First download the latest Geth from the below URL

As I am using a windows machine, I downloaded the windows version. Install the Geth on your machine as per the installation guide.

Create a folder called DevChain where you can keep the chain data.

After that let’s create an account using command prompt. Specify the password when prompted.

Now create a genesis file to define the genesis block, which is the start of the block chain. Here is the genesis file (“genesis_dev.json”) I am using. Replace the account number with number you got in the previous step.

  "nonce": "0x0000000000000042",
  "difficulty": "0x200",
  "config": {
    "chainId": 15,
    "homesteadBlock": 0,
    "eip155Block": 0,
    "eip158Block": 0
  "alloc": {
    "0x0bd615694d433424c292599f080bda45b0c257fc": {
      "balance": "100000000000000000000000"
  "mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "coinbase": "0x0000000000000000000000000000000000000000",
  "timestamp": "0x00",
  "parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "gasLimit": "0x8000000"

Now create a batch file (“startgeth.bat”) which will initialize the network every time you run.

RD /S /Q %~dp0\devChain\geth

geth.exe --datadir=devChain init genesis_dev.json
geth.exe --mine --networkid=12345 --cache=2048 --maxpeers=0 --datadir=devChain --rpc --rpccorsdomain "*" --rpcapi "eth,web3,personal,net,miner,admin,debug" console 

Now run the batch file to initialize and start the test network.

Now our development network is ready to start deploying and testing smart contracts.


  1. Hi,
    I have a problem when deploy smart contract. Because my account have 0 ETH with balance so I have error when deploy: gas price.
    I try to use rinkeby account and make it have 3ETH, but when I use function get my balance, it equal 0.
    Please help me !
    Thanks !

    1. You need to set the default account to be used for collecting gas price
      eth.defaultAccount = eth.coinbase;
      Alternatively you can pass in the account to be used while deploying the contract.

  2. i want to ask if there is any tutorial for a full solution who use a smart contract in youtube