Ethereum

Ethereum is a crypto platform for running smart contracts and exchanging Ether.

My address is 0xd2f887eda1b28c8714dbb2cf63a59f77fb68fb94

Clients

There are a few clients that you can use.

Go-Ethereum (geth)

The Ethereum client written in Go.

Setup

To compile geth, ensure that you have go, gcc, and make installed. Then run:

$ git clone https://github.com/ethereum/go-ethereum
$ cd go-ethereum
$ make geth

geth will be compiled in build/bin/geth.

Usage

When starting geth, it will automatically start downloading the blockchain. It depends on UDP/30303. Ideally, the client should be accessible publicly via that port.

The default cache size used by geth is quite small, so for an initial sync run:

$ geth --datadir /path/to/ethereum-data --cache=1024

Whilst it is syncing, you can check the state of the client by starting and attaching an interactive console:

$ geth attach
> net.listening
true
> admin.peers
> eth.syncing

To create a private net, provide a custom --networkid value or provide a genesis json file with --genesis. While on the private net, you can create a new account and start mining.

Other things you may want to do are:

Task	Command
Create an account. Similar to creating a new wallet.	> personal.newAccount("Write here a good, randomly generated, passphrase!")
Show account balance	> web3.fromWei(eth.getBalance(eth.coinbase), "ether")
Show account address	> eth.coinbase ## or > eth.accounts[0]
Start CPU mining. Useful on testnets	> miner.setEtherbase(eth.accounts[0]) > miner.start()

Other

Backing up your key

Copy the ~/.ethereum/keystore as a backup. It contains your encrypted key. Also, don't forget your passphrase.

Private Test Net

To start your own test network with your own ether, install geth and then do the following:

$ mkdir /tmp/eth/70
$ geth console

## In geth console:
$ personal.newAccount('password')
$ eth.accounts[0]
## you can check the eth.accounts[0] address, copy it and memo to somewhere
## control + c then escape from geth console.


## next make the private net genesisblock json file.
vim privatenet_genesis_block.json 

## this is my sample of testnet genesis block json
{
    "nonce": "0xlitebeefdeadbeef",
    "timestamp": "0x0", 
    "parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000", 
    "extraData": "0x634f727365", 
    "gasLimit": "0x8000000", 
    "difficulty": "0x400", 
    "mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000", 
    "coinbase": "0x3333333333333333333333333333333333333333",
    "alloc": {
   }
}

## then use the previous eth.accounts[0] value as the etherbase value.
## The datadir should be somewhere else.
geth --datadir="/tmp/eth/70" --etherbase="{should be input }" --genesis privatenet_genesis_block.json console
privatenet

Example:

$ ./geth  --networkid 34093 --genesis ~/ethereum/genesis.json --datadir ~/ethereum --etherbase="0xdc9b165c433c8a6ae48713e8eae926767af0bca0" console
$ miner.start(1)

Then attach to the instance with:

$ ./geth  --networkid 34093 --genesis ~/ethereum/genesis.json --datadir ~/ethereum --etherbase="0xdc9b165c433c8a6ae48713e8eae926767af0bca0" --ipcpath ~/ethereum/geth.ipc attach

Dapp Information

Ethereum enables the decentralized web (web3). A dapp, short for decentralized app, is like a web application built on this decentralized web. dapps can be written in HTML and make use of existing JS libraries while taking advantage of the new features offered by ethereum (like what?)

To get started developing, get remix:

• https://github.com/ethereum/remix

Glossary

Because there are so many foreign terminology kicking around.

Term	Definition
web3	A decentralized web. The 'next' iteration of the centralized web as it is (web2).
DAG	Directed Acyclic Graph. A ~1GB dataset used by Ethash. Generated for eacah epoch (every 30,000 blocks or 100 hours). The generation of a new DAG takes a long time.
Target Block Time	The target block time is 15 seconds.
Gas	The amount of ether required to compute something on the virtual machine.
Gas limit	???
Gas Price	How much transactions cost.

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See Also

Greeter contract tutorial

• https://www.ethereum.org/greeter

Contract Guide

• https://eng.erisindustries.com/tutorials/2015/03/11/solidity-1/

DApp Tutorial

• https://dappsforbeginners.wordpress.com/tutorials/your-first-dapp/

• Chicken Lottery: https://www.reddit.com/r/ethereum/comments/3ivfyn/lotto_pollo_lottery_chicken/