6. Deploy Contract

  1. 1.
    truffle configuration
  2. 2.
    Deploy setup
  3. 3.

1) truffle configuration

truffle-config.js file describes how to deploy your contract code. You can configure below items in truffle-config.js
1) Who will deploy the contract (Which Klaytn account will deploy the contract)? 2) Which network will you deploy to? 3) How many gas are you willing to pay to deploy the contract?
There are 2 different methods to deploy your contract, first one uses private key, the other one uses unlocked account.

DEPLOY METHOD 1: By private key

WARNING: You shouldn't expose your private key. Otherwise, your account would be hacked.
If you want to deploy your contract using the private key, provider option is needed.
1) Pass your private key as the 1st argument of new HDWalletProvider(). 2) Pass your Klaytn node's URL as the 2nd argument of new HDWalletProvider().
provider: new HDWalletProvider(
'', // If you're running full node you can set your node's rpc url.
const HDWalletProvider = require("truffle-hdwallet-provider-klaytn");
const NETWORK_ID = '1001'
const GASLIMIT = '8500000'
* We extracted `URL`, `PRIVATE_KEY` as const variable to set value easily.
* Set your private key and klaytn node's URL in here.
const URL = ``
const PRIVATE_KEY = '0x48f5a77dbf13b436ae0325ae91efd084430d2da1123a8c273d7df5009248f90c'
module.exports = {
networks: {
* DEPLOY METHOD 1: By private key.
* You shouldn't expose your private key. Otherwise, your account would be hacked!!
baobab: {
provider: () => new HDWalletProvider(PRIVATE_KEY, URL),
network_id: NETWORK_ID,
gasPrice: null,
See networks property in the above code. It has baobab key which has 4 properties, provider, network_id, gas, gasPrice.
provider: new HDWalletProvider(PRIVATE_KEY, URL) line informs the contract deployer account and the target network node URL.
network_id: NETWORK_ID line specifies the network id in Klaytn. Use 1001 for the Baobab network (testnet).
gas: GASLIMIT line informs how much gas limit will you endure to deploy your contract.
gasPrice: null line informs truffle how much price will you pay per gas unit. Currently in Klaytn, the price is fixed to 25000000000. If you set it to null, truffle will set the value with the fixed gas price automatically.

DEPLOY METHOD 2: By unlocked account (difficult)

To deploy a contract by unlocked account, you should have your Klaytn full node. Access your Klaytn node console by typing $ klay attach http://localhost:8551 If you don't have a Klaytn account in the node, generate it by typing personal.newAccount() on the console. If you already have one, unlock your account through personal.unlockAccount().
After ensuring account is unlocked, you should set the properties, host, port, network_id, and from. 1) Which network to deploy (host, port, network_id) 2) Who will deploy (from) 3) How much gas will you endure to deploy your contract (gas)
Put your unlocked account address on from. If you're running your own Klaytn full node, set the node's host to host and node's port to port.
host: 'localhost',
port: 8551,
from: '0xd0122fc8df283027b6285cc889f5aa624eac1d23',
network_id: NETWORK_ID,
gasPrice: null,

2) Deploy setup (Which contract do you want to deploy?)

const Count = artifacts.require('./Count.sol')
const fs = require('fs')
module.exports = function (deployer) {
.then(() => {
// Record recently deployed contract address to 'deployedAddress' file.
if (Count._json) {
// Save abi file to deployedABI.
JSON.stringify(Count._json.abi, 2),
(err) => {
if (err) throw err
console.log(`The abi of ${Count._json.contractName} is recorded on deployedABI file`)
(err) => {
if (err) throw err
console.log(`The deployed contract address * ${Count.address} * is recorded on deployedAddress file`)
You can specify which contract code will you deploy in your contracts/ directory. First, you should import your contract file (Count.sol) in this file through const Count = artifacts.require('./Count.sol') And use deployer to deploy your contract, through deployer.deploy(Count). If you want to run some logic after deploying your contract, use .then(). We want to store the contract ABI and the deployed address in files. fs node.js module is used to do it. (fs.writeFile(filename, content, callback)) Through this post-process, we save our contract address and ABI as deployedABI and deployedAddress in the directory. For further information about artifacts., visit truffle document site,

3) Deploy

You need KLAY to deploy a contract. You can receive testnet KLAY on faucet.
Type $ truffle deploy --network baobab. It will deploy your contract according to the configurations defined in truffle-config.js and migrations/2_deploy_contracts.js.
cf) --reset option After deploying your contract, if you type $ truffle deploy --network baobab again, nothing will happen. Because truffle deploys a contract only when there are changes in the contract, otherwise truffle will not do anything. If you want to re-deploy your contract anyway, there is an option --reset. If you provide this option, truffle will deploy your contract even the content of contract hasn't changed. ex) $ truffle deploy --reset --network baobab
To recap, truffle-config.js configures the target network, deployer account, and the gas limit. migrations/2_deploy_contracts.js configures the contract to deploy. target network: We deploy our contract to the node deployer account: '0xd0122fc8df283027b6285cc889f5aa624eac1d23' will deploy this contract. gas limit: We can endure up to '20000000' gas for deploying our contract. contract: We will deploy the Count contract.
From the terminal output, you can see if the deployment has been succeeded and find the deployed address.