Now that we’ve covered the history behind Bitcoin and have a theoretical understanding of how blockchains function, let’s see it in action.
Thus far when we have said “node” we meant “full node”. As mentioned, full nodes keeps a complete copy of the Bitcoin blockchain and participates in network consensus by checking and forwarding valid transactions. They download every block and transaction and check them against Bitcoin’s consensus rules.
THINGS A "FULL NODE" DOES
- Keep a complete copy of the blockchain
- Maintain connections to peers
- Validate incoming data (transactions and blocks)
- Distribute valid data
In these ways, a full node contributes to network “consensus”.
Lightweight or thin clients are nodes that use Simplified Payment Verification. SPV is a method for verifying that particular transactions were included in a block without downloading the entire blockchain. This allows you to run software that interacts with the bitcoin network on low resource machines, such as running a wallet on a smartphone. However, using SPV instead of full nodes means the loss of some privacy and security.
Before we can set up a node there are two more things to consider. Do we want to run on mainnet, testnet or regtest? And which Bitcoin implementation do we want to use?
Mainnet
Mainnet is the live Bitcoin network. To fully participate in the Bitcoin ecosystem you’ll want to be running a mainnet node. However, when starting out and testing new applications mainnet is likely not the best option as it comes with the risk of losing coins which have real value. To run a mainnet full node you will need to download the entire ~200GB blockchain.
Testnet
Testnet is a public bitcoin network that is used by developers around the world to test Bitcoin applications. You can find and use Bitcoin testnet coins and exchange them with others on the testnet. These coins very intentionally have no exchange value; they are used simply for testing. To run a testnet node you will need to download the testnet blockchain which is significantly smaller than mainnet at only ~20GB.
Regtest
Regtest allows you to set up your own local blockchain. When you start a node in regtest mode there is no blockchain data to download. You need to create all the blockchain data yourself!
Once you know what network you want to run on, you’ll need to choose a client or implementation. Bitcoin core (formerly Bitcoin-Qt), is the reference implementation and is still the most commonly used bitcoin implementation. It is written in C++. However, there are now a number of other options such as Bitcore witch is written in Node.js or btcd which is written in GoLang.
Here we will walk through instructions for both Bitcoin’s testnet and running in regtest mode using the reference implementation Bitcoin Core, or more specifically the bitcoind daemon.
The below instructions are for Ubuntu machines. Mac OS and Windows instructions can be found
here.
UBUNTU INSTRUCTIONS
>_
Install the Bitcoin Daemon
hannah@ubuntu:
~/ $
apt-add-repository ppa:bitcoin/bitcoin
hannah@ubuntu:
~/ $
apt-get update
hannah@ubuntu:
~/ $
apt-get install bitcoind
BITCOIND RESOURCES
Once you have the software installed, we’ll need to configure it.
TESTNET INSTRUCTIONS
>_
Install the Bitcoin Daemon
hannah@ubuntu:
~/ $
apt-add-repository ppa:bitcoin/bitcoin
hannah@ubuntu:
~/ $
apt-get update
hannah@ubuntu:
~/ $
apt-get install bitcoind
>_
Start bitcoind
hannah@ubuntu:
~/ $
bitcoind -testnet -printtoconsole -daemon -server
>_
View the debug log in a separate console window
hannah@ubuntu:
~/ $
tail -f .bitcoin/testnet/debug.log
>_
Create a config file in .bitcoin
hannah@ubuntu:
~/ $
touch bitcoin.conf
THE BITCOIN.CONF FILE
Bitcoin.conf Configured for RPC
1
# Set up RPC
2
server=1
3
rpcuser=test
4
rpcpassword=test
5
rpchost=127.0.0.1
6
rpcport=6163
7
# Run on the testnet
8
testnet=1
9
# Specify a directory for testnet data
10
#datadir=/home/bitcoin/.bitcoin/testnet
REGTEST MODE INSTRUCTIONS
>_
Start bitcoind in regtest mode
hannah@ubuntu:
~/ $
bitcoind -regtest -printtoconsole -daemon -server
>_
View the debug log in a separate console window
hannah@ubuntu:
~/ $
tail -f .bitcoin/regtest/debug.log
>_
Create a config file in .bitcoin/regtest
hannah@ubuntu:
~/ $
touch bitcoin.conf
THE BITCOIN.CONF FILE
Bitcoin.conf Configured for RPC
1
# Set up RPC
2
server=1
3
rpcuser=test
4
rpcpassword=test
5
rpchost=127.0.0.1
6
rpcport=6163
7
# Run on a regtest network
8
regtest=1
9
# Connect only to the specified node
10
connect=[your local IP]
TRY OUT SOME COMMANDS
>_
Kill bitcoind and restart
hannah@ubuntu:
~/ $
pkill -9 -f bitcoind
hannah@ubuntu:
~/ $
bitcoind [-regtest or -testnet] -printtoconsole -daemon -server
>_
Use bitcoin-cli to view your connection to peers
hannah@ubuntu:
~/ $
bitcoin-cli [-regtest or -testnet] -getinfo
>_
Generate a new address to receive coins
hannah@ubuntu:
~/ $
bitcoin-cli [-regtest or -testnet] getnewaddress
>_
Check your balance
hannah@ubuntu:
~/ $
bitcoin-cli [-regtest or -testnet] getbalance
Now that we’ve had a chance to experience bitcoin on the command line, let’s take a step back in our next lesson and be sure we understand in more depth what a bitcoin is.
