Creating a private network

After Geth is installed, it can be configured to run locally without connecting to any network on the internet. Every chain and network has a genesis block or the first block. This block does not have any parent and is the first block of the chain. A genesis.json file is required to create this first block. A sample genesis.json file is shown in the following code snippet:

{  
"config": {
"chainId": 15,
"homesteadBlock": 0,
"eip155Block": 0,
"eip158Block": 0
},
"nonce": "0x0000000000000042",
"mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000",
"difficulty": "0x200",
"alloc": {},
"coinbase": "0x0000000000000000000000000000000000000000",
"timestamp": "0x00",
"parentHash&quot...