Working with Go Ethereum (geth)

Mr. Latte ∙ Software Development Expert

Installing libraries

sudo apt-get install -y build-essential libgmp3-dev golang git tree

Geth

Geth is the Ethereum node core written in Go. The core exists in several languages, and the Go one is said to be the most widely used. On real projects, Parity is reportedly used more often, for reasons including stability.

Installing

cd
git clone https://github.com/ethereum/go-ethereum.git
cd go-ethereum/
git checkout refs/tags/v1.5.5
make geth
./build/bin/geth version
sudo cp build/bin/geth /usr/local/bin/
which geth

Preparing the data directory

mkdir ~/data_testnet

The genesis file

An identical genesis file means the network is recognized as the same coin, so creating a separate coin or a test network requires editing this file to change the block.

• cd data_testnet/
• vi genesis.json

    {
    	"nonce": "0x0000000000000042",
    	"timestamp": "0x0",
    	"parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
    	"extraData": "0x0",
    	"gasLimit": "0x8000000",
    	"difficulty": "0x4000",
    	"mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000",
    	"coinbase": "0x3333333333333333333333333333333333333333",
    	"alloc": {}
    }

The geth console

Initialize

geth --datadir /home/eth/data_testnet init /home/eth/data_testnet/genesis.json
cd
tree data_testnet/

Run

geth --networkid 4649 --nodiscover --maxpeers 0 --datadir /home/eth/data_testnet console 2>> /home/eth/data_testnet/geth.log

Create accounts

personal.newAccount("pass0")
personal.newAccount("pass1")

Check accounts

eth.accounts
eth.accounts[0]
eth.accounts[1]

Exit the geth console

exit

Create an account from the geth command line

geth --datadir /home/eth/data_testnet account new

List accounts from the geth command line

geth --datadir /home/eth/data_testnet account list

Run geth

geth --networkid 4649 --nodiscover --maxpeers 0 --datadir /home/eth/data_testnet console 2>> /home/eth/data_testnet/geth.log

Check accounts

eth.accounts

Check the etherbase

eth.coinbase

Change the etherbase

miner.setEtherbase(eth.accounts[1])

Check and restore the etherbase

eth.coinbase
miner.setEtherbase(eth.accounts[0])
eth.coinbase

Check account balances

eth.getBalance(eth.accounts[0])
eth.getBalance(eth.accounts[1])
eth.getBalance(eth.accounts[2])

Check the block number

The block number increases as mining proceeds. Since transactions are recorded in blocks, it is easy to assume a block only gets created when there is a transaction to record. In fact, once the block time passes with no transactions, an empty block is created anyway.

eth.blockNumber

Start mining

miner.start(1)

Confirm mining is running

eth.mining

Check the hashrate

eth.hashrate

Stop mining

miner.stop()

Check the etherbase balance

eth.getBalance(eth.coinbase)

Check account balances

eth.getBalance(eth.accounts[0])
eth.getBalance(eth.accounts[1])
eth.getBalance(eth.accounts[2])

Check balances through web3

web3.fromWei(eth.getBalance(eth.accounts[0]), "ether")
web3.fromWei(eth.getBalance(eth.accounts[1]), "ether")
web3.fromWei(eth.getBalance(eth.accounts[2]), "ether")

Send a transaction

eth.sendTransaction({from: eth.accounts[0], to: eth.accounts[1], value: web3.toWei(10, "ether")})

Unlock an account

personal.unlockAccount(eth.accounts[0])
personal.unlockAccount(eth.accounts[0], "pass0")
personal.unlockAccount(eth.accounts[0], "pass0", 0)

Check pending transactions

eth.pendingTransactions

Check the balance

web3.fromWei(eth.getBalance(eth.accounts[1]), "ether")

Send a transaction

eth.sendTransaction({from: eth.accounts[1], to: eth.accounts[2], value: web3.toWei(5, "ether")})

Check the balances

web3.fromWei(eth.getBalance(eth.accounts[2]), "ether")
web3.fromWei(eth.getBalance(eth.accounts[1]), "ether")
web3.fromWei(eth.getBalance(eth.accounts[0]), "ether")

Run geth in the background

nohup geth --networkid 4649 --nodiscover --maxpeers 0 --datadir /home/eth/data_testnet --mine --minerthreads 1 --rpc 2>> /home/eth/data_testnet/geth.log &

Attach to the geth console

geth attach rpc:http://localhost:8545

Run geth in the background with JSON-RPC

nohup geth --networkid 4649 --nodiscover --maxpeers 0 --datadir /home/eth/data_testnet --mine --minerthreads 1 --rpc --rpcaddr "0.0.0.0" --rpcport 8545 --rpccorsdomain "*" --rpcapi "admin,db,eth,debug,miner,net,shh,txpool,personal,web3" 2>> /home/eth/data_testnet/geth.log &