The node is the entry gate and facade between blockchain network and developer/application. The blockchain itself is network of nodes cooperating with each other. The node provide API for mining, managing accounts, sending transactions, interacting with smart contracts and more.

Development node is what in this article is meant by 1-node-blockchain. It gives us all the features of main network blockchain node + the control over mining. Interaction with development network is easy and what important: free.
In this article I will present all the steps to setup it within few minutes on Linux system (Arch).

Ethereum nodes

Ethereum has two leading nodes implementations: Parity (https://www.parity.io/ethereum/) and Geth (https://geth.ethereum.org/).
According to https://www.ethernodes.org/network/1 Geth is lead running client. There might be differences between some extra features in these nodes implementations however we can be sure that both of them will implement https://github.com/ethereum/wiki/wiki/JSON-RPC API.

1. Download and setup Geth.

https://geth.ethereum.org/downloads/ is the link where depending of OS you have, any Geth executable can be download.
In my case I’ve downloaded Geth 1.8.17, 64 bit. If you are not sure about your CPU architecutre you can check it with uname -m bash command.

After download extract:

~ tar zxvf <your-file-name>.tar.gz

Then:

~ ./<extracted-geth-folder>/geth --datadir ./FirstEthBlockchain account new

<extracted-geth-folder> is the folder of extracted Geth. There should be geth binary inside.

You will be asked for password. For sake of simplicity you don’t have to provide it. In my case the whole procedure was:

~ ./geth-linux-amd64–1.8.17–8bbe7207/geth --datadir ./FirstEthBlockchain account new 
INFO [10–23|19:41:25.141] Maximum peer count ETH=25 LES=0 total=25 
Your new account is locked with a password. Please give a password. Do not forget this password. 
Passphrase: 
Repeat passphrase: 
Address: {c7c7d647cf3e4f1b072422c0ab5120fe810ee3b2}

The generated address is c7c7d647cf3e4f1b072422c0ab5120fe810ee3b2.

3. Create genesis file. Initialize blockchain.

The genesis file is json structured file which describes among the other the initial settings needed to initialize the blockchain. It is the initial, first block.
We will create minimum of the gensis file which will contain only required fields.

In our case the file should be created in FirstEthBlockchain folder. The content of genesis.json is given:

{
 “config”: {
 “chainId”: 1907,
 “homesteadBlock”: 0,
 “eip155Block”: 0,
 “eip158Block”: 0
 },
 “difficulty”: “10”,
 “gasLimit”: “2100000”,
 “alloc”: {},
 "coinbase": "c7c7d647cf3e4f1b072422c0ab5120fe810ee3b2"
}

Replace the coinbase key with the value of your account address, generated in step 1.

Run the blockchain initialization command:

~ ./<extracted-geth-folder>/geth --datadir ./FirstEthBlockchain init ./FirstEthBlockchain/genesis.json

In my case the command was and result was:

./geth-linux-amd64–1.8.17–8bbe7207/geth --datadir FirstEthBlockchain init FirstEthBlockchain/genesis.json
INFO [10-23|19:11:48.764] Maximum peer count                       ETH=25 LES=0 total=25 
INFO [10-23|19:11:48.764] Allocated cache and file handles         database=/home/w/Downloads/FirstEthBlockchain/geth/chaindata cache=16 handles=16 
INFO [10-23|19:11:48.777] Writing custom genesis block  
INFO [10-23|19:11:48.777] Persisted trie from memory database      nodes=0 size=0.00B time=4.777µs gcnodes=0 gcsize=0.00B gctime=0s livenodes=1 livesize=0.00B 
INFO [10-23|19:11:48.777] Successfully wrote genesis state         database=chaindata                                              hash=357b5e…1b20b9 
INFO [10-23|19:11:48.778] Allocated cache and file handles         database=/home/w/Downloads/FirstEthBlockchain/geth/lightchaindata cache=16 handles=16 
INFO [10-23|19:11:48.795] Writing custom genesis block  
INFO [10-23|19:11:48.795] Persisted trie from memory database      nodes=0 size=0.00B time=5.114µs gcnodes=0 gcsize=0.00B gctime=0s livenodes=1 livesize=0.00B 
INFO [10-23|19:11:48.796] Successfully wrote genesis state         database=lightchaindata                                              hash=357b5e…1b20b9

4. Start Ethereum node.

Our goal is to run Ethereum node and communicate with it using RPC API. It’s just a HTTP based communication, most messages are JSON based.

To start Ethereum with RPC server enabled:

~ ./<extracted-geth-folder>/geth --rpc --rpcaddr localhost --rpcport 6666 --rpcapi “personal,eth,web3,net” ---datadir ./FirstEthBlockchain console

The command is basically: initialize blockchain with RPC server listening on 6666 port (the port we will communicate with node). Enable personal, eth, web3, net APIs enabled via RPC api calls. Open interactive console just after Ethereum node start.

In my case the command and the result:

~ ./geth-linux-amd64–1.8.17–8bbe7207/geth --rpc --rpcaddr localhost --rpcport 6666 --rpcapi “personal,eth,web3,net” --datadir ./FirstEthBlockchain console 
INFO [10-23|19:49:35.997] Maximum peer count                       ETH=25 LES=0 total=25 
INFO [10-23|19:49:35.998] Starting peer-to-peer node               instance=Geth/v1.8.17-stable-8bbe7207/linux-amd64/go1.11.1 
INFO [10-23|19:49:35.998] Allocated cache and file handles         database=/home/w/Downloads/FirstEthBlockchain/geth/chaindata cache=768 handles=1024 
INFO [10-23|19:49:36.021] Initialised chain configuration          config="{ChainID: 1907 Homestead: 0 DAO: <nil> DAOSupport: false EIP150: <nil> EIP155: 0 EIP158: 0 Byzantium: <nil> Constantinople: <nil> Engine: unknown}" 
INFO [10-23|19:49:36.022] Disk storage enabled for ethash caches   dir=/home/w/Downloads/FirstEthBlockchain/geth/ethash count=3 
INFO [10-23|19:49:36.022] Disk storage enabled for ethash DAGs     dir=/home/w/.ethash                                  count=2 
INFO [10-23|19:49:36.022] Initialising Ethereum protocol           versions="[63 62]" network=1 
INFO [10-23|19:49:36.022] Loaded most recent local header          number=0 hash=357b5e…1b20b9 td=10 age=49y6mo1w 
INFO [10-23|19:49:36.022] Loaded most recent local full block      number=0 hash=357b5e…1b20b9 td=10 age=49y6mo1w 
INFO [10-23|19:49:36.022] Loaded most recent local fast block      number=0 hash=357b5e…1b20b9 td=10 age=49y6mo1w 
INFO [10-23|19:49:36.022] Regenerated local transaction journal    transactions=0 accounts=0 
INFO [10-23|19:49:36.022] Starting P2P networking  
INFO [10-23|19:49:38.188] UDP listener up                          self=enode://b9e92c81cc46c89924e7f46c23dc6f78a088a130cf1dd5806637af8b43c2c5dab6eb770139828c2a7c5fce5e4940772f9b3b1a95367c1cd43e672dc479678f16@62.87.191.226:30303 
INFO [10-23|19:49:38.188] RLPx listener up                         self=enode://b9e92c81cc46c89924e7f46c23dc6f78a088a130cf1dd5806637af8b43c2c5dab6eb770139828c2a7c5fce5e4940772f9b3b1a95367c1cd43e672dc479678f16@62.87.191.226:30303 
INFO [10-23|19:49:38.193] IPC endpoint opened                      url=/home/w/Downloads/FirstEthBlockchain/geth.ipc 
INFO [10-23|19:49:38.195] HTTP endpoint opened                     url=http://localhost:6666                            cors= vhosts=localhost 
Welcome to the Geth JavaScript console! 
 
instance: Geth/v1.8.17-stable-8bbe7207/linux-amd64/go1.11.1 
INFO [10-23|19:49:38.290] Etherbase automatically configured       address=0xc7c7D647CF3e4F1b072422c0AB5120fe810Ee3b2 
coinbase: 0xc7c7d647cf3e4f1b072422c0ab5120fe810ee3b2 
at block: 0 (Thu, 01 Jan 1970 01:00:00 CET) 
 datadir: /home/w/Downloads/FirstEthBlockchain 
 modules: admin:1.0 debug:1.0 eth:1.0 ethash:1.0 miner:1.0 net:1.0 personal:1.0 rpc:1.0 txpool:1.0 web3:1.0 
 
>

Well done. Server started, console is opened.

5. Verify and test the blockchain.

We initialized the blockchain! The interactive console enables to execute node operations. Let’s check the current balance of the main account we previously created:

> eth.getBalance(eth.coinbase)
0

The balance is 0. We have currently just 1 block (genesis, with index 0). Let’s start mining:

> miner.start()
INFO [10-23|19:50:14.286] Updated mining threads                   threads=8 
INFO [10-23|19:50:14.286] Transaction pool price threshold updated price=1000000000 
null 
> INFO [10-23|19:50:14.287] Commit new mining work                   number=1 sealhash=6a7718…cc09c0 uncles=0 txs=0 gas=0 fees=0 elapsed=422.921µs 
INFO [10-23|19:50:18.778] Successfully sealed new block            number=1 sealhash=6a7718…cc09c0 hash=3cbd10…192cbd elapsed=4.491s 
INFO [10-23|19:50:18.778] 🔨 mined potential block                  number=1 hash=3cbd10…192cbd 
INFO [10-23|19:50:18.778] Commit new mining work                   number=2 sealhash=c46033…8e3acd uncles=0 txs=0 gas=0 fees=0 elapsed=124.783µs 
INFO [10-23|19:50:19.480] Successfully sealed new block            number=2 sealhash=c46033…8e3acd hash=2508d3…ef2775 elapsed=702.267ms 
INFO [10-23|19:50:19.480] 🔨 mined potential block                  number=2 hash=2508d3…ef2775 
INFO [10-23|19:50:19.480] Commit new mining work                   number=3 sealhash=32ed88…3efbfb uncles=0 txs=0 gas=0 fees=0 elapsed=106.819µs 
INFO [10-23|19:50:19.492] Successfully sealed new block            number=3 sealhash=32ed88…3efbfb hash=616d95…ea81ad elapsed=11.744ms 
INFO [10-23|19:50:19.492] 🔨 mined potential block                  number=3 hash=616d95…ea81ad 
INFO [10-23|19:50:19.492] Commit new mining work                   number=4 sealhash=25afba…e45d01 uncles=0 txs=0 gas=0 fees=0 elapsed=142.264µs 
INFO [10-23|19:50:20.028] Successfully sealed new block            number=4 sealhash=25afba…e45d01 hash=ea8fa1…2ded23 elapsed=535.337ms 
INFO [10-23|19:50:20.028] 🔨 mined potential block                  number=4 hash=ea8fa1…2ded23 
INFO [10-23|19:50:20.028] Commit new mining work                   number=5 sealhash=1b2621…c0e459 uncles=0 txs=0 gas=0 fees=0 elapsed=108.61µs
> 

Stop it after few seconds with:

> miner.stop()

Check the balance now:

> eth.getBalance(eth.coinbase) 
20000000000000000000

We mine 5 Ethereum per 1 block. After 5 blocks I have 25 Ethers (the value is given in Wei. Use the converter: https://etherconverter.online/ to find out how much Ether is it).

6. Test the RPC API.

Last part is to check if we can remotely use our node API using RPC API.
The API should be accessible under port 6666 (the value was given in previous steps). Let’s verify the server using curl:

~ curl --data-binary '{"jsonrpc":"2.0","id":"curltext","method":"eth_getBalance","params":["0xc7c7d647cf3e4f1b072422c0ab5120fe810ee3b2","latest"]}' -H 'content-type:application/json;' http://localhost:6666 -vvvv
* Rebuilt URL to: http://localhost:6666/ 
*   Trying ::1... 
* TCP_NODELAY set 
* connect to ::1 port 6666 failed: Connection refused 
*   Trying 127.0.0.1... 
* TCP_NODELAY set 
* Connected to localhost (127.0.0.1) port 6666 (#0) 
> POST / HTTP/1.1 
> Host: localhost:6666 
> User-Agent: curl/7.60.0 
> Accept: */* 
> content-type:application/json; 
> Content-Length: 124 
>  
* upload completely sent off: 124 out of 124 bytes 
< HTTP/1.1 200 OK 
< Content-Type: application/json 
< Date: Wed, 24 Oct 2018 07:11:17 GMT 
< Content-Length: 49 
<  
{"jsonrpc":"2.0","id":"curltext","result":"0x2fb474098f67c0000"} 
* Connection #0 to host localhost left intact

This call checks the balance of coinbase account (replace 0xc7c7d647cf3e4f1b072422c0ab5120fe810ee3b2 with your address) in the latest mined block.
The result is hexadecimal encoded — you can use this tool: https://codebeautify.org/hex-decimal-converter to decrypt it. In my case the decimal result is: 55000000000000000000 (Wei), what is 55 Ethers.

Summary

We did the minimal setup of the private network Ethereum Geth node, which allows to interact with node via remote RPC API. The user has the control over the network, including mining.