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 first block. This block does not have any parent and is the first block of a 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": 9999,
    "homesteadBlock": 0,
    "eip150Block": 0,
    "eip150Hash": 0,
    "eip155Block": 0,
    "eip158Block": 0,
    "byzantiumBlock": 0,
    "constantinopleBlock": 0,
    "petersburgBlock": 0,
    "istanbulBlock": 0,
    ...