Build Your Own Blockchain – FACILELOGIN

How to Create a Private Ethereum Blockchain from Ground-up?

Ethereum is a decentralized podium that runs clever contracts, applications that run exactly spil programmed without possibility of downtime, censorship, fraud or third party interference. Te this blog postbode I will take you through all the steps required te setting up a fully functioning private ethereum blockchain, inwards your local network — which includes:

  • Setting up a private blockchain with ethereum using geth.
  • Setting up the MetaMask ethereum wallet to work with the private blockchain.
  • Transfer funds inbetween numerous accounts.
  • Create, deploy and invoke a wise contract on the private blockchain using remix.
  • Setting up ethereum block explorer overheen the private blockchain.

Install Geth

Go Ethereum (or geth) is one of the three original implementations (along with C++ and Python) of the ethereum protocol. It is written ter Go, fully open source and licensed under the GNU LGPL v3. Go Ethereum is available either spil a standalone client called geth that you can install on pretty much any operating system, or spil a library that you can embed ter your Go, Android or iOS projects.

To install geth on Mac OS X, wij use homebrew. Homebrew installs the stuff you need that Apple didn’t. This blog assumes you have homebrew installed already, ter case not check this out. Once you have homebrew installed, following guidelines will install geth.

Installing geth on Ubuntu is straightforward, you just need to use apt-get — the directions are shown below.

For Windows, you can find the corresponding geth installation here. If you find any difficulties ter any of the above installations, check this out.

Create a Miner Account

Very first wij need to create an account for ethereum mining. This will generate a public/private key pair for you — and will be password protected. Do not lose your password, otherwise you will never be able to recover the keys. By default, keys are stored inwards, <,datadir>,/keystore. Everything geth persists, gets written inwards datadir (except for the PoW Ethash DAG). The default gegevens directory locations are toneel specific. It is always better to override the path of the datadir, and maintain your own location for your private blockchain.

The Ethash DAG is stored at

/.ethash (Mac/Linux) or %APPDATA%\Ethash (Windows) so that it can be reused by all clients.

Following instruction shows how to create an account, with a custom-built path for the datadir. Once ended, it will print your ethereum address.

Create the Genesis Block

One ethereum blockchain differs from another by the genesis block. A blockchain starts with a genesis block and keeps building on top of it, where each block refers to the one below. Ter the ethereum public blockchain, the genesis block wasgoed created on July 20, 2015. To build our own blockchain, wij need to create our own genesis block. Use the following guideline to init our private blockchain with the given genesis block.

  • datadir: gegevens directory for the databases and keystore.
  • init: bootstrap and initialize a fresh genesis block — with the provided json opstopping.

Following shows our genesis block, used te our private blockchain — you need to save this spil genesis.json and pass it to the above directive.

  • chainid: this provides a way to send transactions that work on ethereum without working on ETC (ethereum classic) or the Morden testnet. EIP 155 suggests following chainid values for different networks: ethereum mainnet (1), morden /expanse mainnet (Two), ropsten (Three), rinkeby (Four), rootstock mainnet (30), rootstock testnet (31), kovan (42), ethereum classic mainnet (61), ethereum classic testnet (62), geth private chains (1337 by default). Ter our example wij have used 15, which is not used by any of thesis networks.
  • homesteadBlock: the value 0 indicates, it is using ethereum homestead release. Homestead is the 2nd major ethereum release — and duo of days back on 16th Oct, 2018, ethereum did a hard fork to budge to the byzantium release.
  • eip155Block: the value 0 indicates, this block supports EIP (ethereum improvement proposal)155. EIPs describe standards for the ethereum toneel, including core protocol specifications, client APIs, and contract standards.
  • eip158Block: the value 0 indicates, this block supports EIP (ethereum improvement proposal)158.
  • difficulty: a value corresponding to the difficulty level applied during the nonce discovery of this block. Ter this blog I explain how the difficulty is calculated ter ethereum, te detail.
  • gasLimit: gas is the internal pricing for running a transaction or contract te ethereum. Each instruction sent to the Ethereum Virtual Machine (EVM) to process a transaction or brainy contract costs a specific amount of gas. If the required amount of gas is not provided to the transaction, it will fail before completion. When you do any ethereum transaction, you specify a gas limit — that is the maximum gas all the operations corresponding to that transaction can consume. The gasLimit parameter ter the block specifies, the aggregated gasLimit from all the transactions included te the block.
  • alloc: this permits to pre-allocate ether to one or more accounts from the genesis block. Ter the above genesis block, the pre-allocation is done to the account wij created at the begining.

Embark Mining

All set! Now wij can begin mining with geth using the following directive. The networkid parameter here differentiates this ethereum network from the others. All the miners who want to connect to this network, have to use the same networkid along with the same genesis block.

  • networkid:network identifier of this ethereum network. You pick a value you want. For example: olympic (0), frontier (1), morden (Two), ropsten(Trio).
  • mine: enables mining.
  • rpc: enables an HTTP-RPC server. Wallet applications can connect to this mining knot overheen http.
  • rpcaddr: specifies the HTTP-RPC server listening interface (default: “localhost”)
  • rpcport: specifies the HTTP-RPC server listening port (default: 8545)
  • rpcapi: specifies the API’s suggested overheen the HTTP-RPC interface (default: “eth,netwerken,web3”)
  • rpccorsdomain: enables CORS by specifying a comma separated list of domains from which to accept cross origin requests. This is useful when using browser based solidity editors (remix) to deploy clever contracts or browser based wallets. For example, following will accept CORS from any domain.
  • nodiscover: disables the peer discovery mechanism. None of the other knots ter the network will not be able to find your knot. If you intend to have this private blockchain being used within your local network with others, do not use this parameter.
  • console:with this guideline wij can commence the mining knot with an interactive javascript environment. Wij will learn more about this ter the next section.

Link Geth Console

Either you can begin the mining knot spil a console — or you run the console separately and link it to a mining knot, with the fasten instruction. The following shows how to do it, and make sure you go after the same parameter order.

The console connects to the mining knot overheen ipc. ipc (inter-process communications) works on the local laptop. Te this case geth creates an ipc pipe (which is represented by the verkeersopstopping <,path-to-data-directory>,/geth.ipc) on local computer’s filesystem — and console makes the connection to that knot overheen ipc.

View All Accounts

Once you are connected to the geth console, you can attempt out the following directive to list all the available accounts.

View Account Balance

Following directive shows how to view the balance of a given account from the geth console.

Connect MetaMask Ethereum Wallet

MetaMask is an ethereum wallet, running spil a chrome extension. It injects the ethereum web3 API into every website’s javascript setting, so that those apps can read from the blockchain. MetaMask also lets the user create and manage their own identities, so when an application wants to perform a transaction and write to the blockchain, the user gets a secure interface to review the transaction, before approving or rejecting it.

To connect MetaMask to the private ethereum blockchain, wij need to pick the right host name and the port. Web3 API is the ethereum javascript API implemented te web3.js. To talk to an ethereum knot from a javascript application, MetaMask uses the web3.js library, which gives a convenient interface for the rpc methods. Under the spandex hood it communicates to a local knot through rpc calls. web3.js works with any ethereum knot, which exposes an rpc layer. You might have noticed ter the above, when wij begin the mining knot, wij can pass the parameter rpcapi to specify, which interfaces wij need to expose from that knot. By default, if you do not specify anything, eth,netwerk,web3 — will be exposed.

Transfer Ether

MetaMask will create you an ethereum account — a private key and an ethereum address. Following shows you how to transfer ether from the very first account you created at the very beginning to the MetaMask account, from the geth console. To transfer funds from an account, wij have to use that account’s private key for the signature. To use the private key, wij need to unlock it, spil shown below.

private is a management API provided by geth. Te addition to private, geth also provides management APIs: admin, debug, miner and txpool. Once wij unlock the account, wij can define three variables ter the console, for the sender, receiver and amount to be sent. The value of the sender is the ethereum address wij created at the very beginning of this blog, and the value of the receiver is the ethereum address created under MetaMask.

Following directive will do the funds transfer — it refers the variables wij defined above.

View Account Balance Ter MetaMask

Once wij finished the funds transfer following the above steps, you can find the account balance te two ways. One way is directly from the MetaMask plugin, spil shown below.

The other way is via the geth console, with the following directive.

Remex Solidity Editor

Solidity is the most popular programming language to write ethereum wise contracts. Remix is an IDE for solidity and has an integrated debugger and testing environment. You can access remix online editor from here. Remix can be connected to any ethereum network. To connect it to our local blockchain, make sure that you have began your mining knot with the following guideline, with the highlighted parameter. The meaning of this parameter wasgoed discussed before. Instead of “*” (which is more open) you can also use “” spil the value of rpccorsdomain.

To connect, remix to our private network, wij need to switch the Environment to Web3 Provider, under the tabulator Run. When you do this switch, remix will prompt you to specify the Web3 Provider Endpoint — set the value http://localhost:8545. Unless you have switched the port explicitly, the default mining knot will begin on the port 8545.

Writing a Clever Contract

Now wij are all set to write our very very first clever contract to run on ethereum. Copy the following code and paste it on the remix online editor. This is a very elementary wise contract — and I do not wish to do a line by line explanation. Ter the next blog will explain solidity te detail.

If you have not switched any default settings ter remix, it is set to automaat compile. If not you need to compile.

After compiling, when you click on the Details button, it will voorstelling you the estimated gas need to create this brainy contract.

Deploying a Wise Contract

Now wij can deploy our clever contract to our private blockchain. Under the Run tabulator, make sure you have the right ethereum account selected, and then the right gas limit is specified. You can keep gas price and value spil zero.

Wij use an ethereum transaction, signed by the selected account above to deploy the wise contract to the blockchain. To do the signing, very first wij need to unlock the account, via the geth console.

Now you can click on the Create button to deploy the wise contract. Te our brainy contract, wij have a constructor which accepts a string parameter, that’s why remix shows you an input opbergruimte along with the Create button. You can type some value there (within quotes, e.g: “Hi”) — or just keep it empty. You will see the following message on the geth console when you submit the clever contract for creation. Also note that, if you have not specified the right gas limit, the above will terugwedstrijd an error.

Invoking a Wise Contract

Once you deploy the clever contract, remix UI gets switched a bit — spil shown below, under the Run tabulator.

Now you can set some value to the setGreeting method — and click on it to invoke the wise contract. Once again, make sure that you have your account unlocked, because, to invoke a wise contract wij use ethereum transactions and wij need the signature of the initiator. Once done with the setGreeting method, you can invoke other methods too.

Ethereum Block Explorer

You may be familiar with etherscan, which gives a lotsbestemming of insights into the ethereum public blockchain. But wij cannot use it to point to our local blockchain. Ethereum block explorer even however not spil feature rich spil etherscan, is fairly useful to find out what is going on te our local blockchain.

To setup ethereum block explorer very first wij need to get its source code from the following git repo.

Then, run the following install guideline from the explorer directory.

Once the installation is done, embark the ethereum block explorer with the following directive — and then you can access the web console from http://localhost:8000.

To connect ethereum block explorer to our local blockchain, make sure that you have began your mining knot with the following directive, with the highlighted parameter — the meaning of this parameter wasgoed discussed before.

Update: There is a discussion on this blog on Hacker News. Please feel free to join


Ter this blog postbode wij discussed how to set up a private blockchain with ethereum using geth. Then wij got MetaMask ethereum wallet to work with the private blockchain and transferred funds to the ethereum account created te MetaMask. remix online IDE wasgoed used to create, deploy and invoke a wise contract on the private blockchain. Eventually wij did set up ethereum block explorer overheen the private blockchain.

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