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私有链

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搭建私有链，首先需要写一个创世块文件，创世块就是我自己链上的第一个区块。

{
 "config":{},
 "nonce":"0x0000000000000042",
 "mixhash":"0x0000000000000000000000000000000000000000000000000000000000000000",
 "difficulty": "0x100",
 "alloc": {},
 "coinbase":"0x0000000000000000000000000000000000000000",
 "timestamp": "0x00",
 "parentHash":"0x0000000000000000000000000000000000000000000000000000000000000000",
 "extraData": "0x00",
 "gasLimit":"0xfffffff" }

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1. config：这个参数很重要，如果少了这个参数，挖矿就会一直不成功
2. nonce: 是一个64位随机数，用于挖矿
3. mixhash: 与nonce配合用于挖矿，由上一个区块的一部分生成的hash
4. difficulty: 设置当前区块的难度，如果难度过大，cpu挖矿就很难，这里设置较小难度
5. alloc: 用来预置账号以及账号的以太币数量
6. coinbase: 矿工的账号,默认的初始值为创建的第一个账户
7. timestamp：设置创世块的时间戳，可计算当前实时时间，以后查询交易时间更方便
8. parentHash：上一个区块的hash值，因为是创世块，所以这个值是0
9. extraData：附加信息
10. gasLimit：该值设置对GAS的消耗总量限制，用来限制区块能包含的交易信息总和，以后为了更复杂的交易，我们将其设置为最大值

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初始化
（1）在终端输入这两条命令，创建文件夹myPrivate,并进入该文件夹

mkdir myPrivate
cd myPrivate

（2）将刚刚的创世块文件genesis.json，放在文件夹下，接着执行命令进行初始化

geth init genesis.json

启动私有链
执行如下命令：

geth  --rpc --rpccorsdomain "*" --rpcapi "personal,web3,eth"  console

这是我总结的最重要的geth启动项，在区块链的前端开发中每一个都不可缺少。

$ geth  --rpc --rpccorsdomain "*" --rpcapi "personal,web3,eth"  --rpc
addr "10.18.25.15" console
INFO [06-13|10:45:13] instance:Geth/v1.6.0-unstable-105b37f1/darwin/go1.8
INFO [06-13|10:45:13] Allocated cache and file handles database=/Users/xue/Library/Ethereum/geth/chaindata cach
e=128 handles=1024
INFO [06-13|10:45:13] Initialised chain configuration config="{ChainID: 0 Homestead: <nil> DAO: <nil> DAOSuppo
rt: false EIP150: <nil> EIP155: <nil> EIP158: <nil>}"
INFO [06-13|10:45:13] Disk storage enabled for ethash caches dir=/Users/xue/Library/Ethereum/geth/ethash count=3
INFO [06-13|10:45:13] Disk storage enabled for ethash DAGs dir=/Users/xue/.ethash count=2
INFO [06-13|10:45:13] Initialising Ethereum protocol versions="[63 62]" network=1
INFO [06-13|10:45:13] Loaded most recent local header number=288 hash=9a47c9…e52fea td=38712958
INFO [06-13|10:45:13] Loaded most recent local full block number=288 hash=9a47c9…e52fea td=38712958
INFO [06-13|10:45:13] Loaded most recent local fast block number=288 hash=9a47c9…e52fea td=38712958
INFO [06-13|10:45:13] Starting P2P networking
INFO [06-13|10:45:15] RLPx listener up self=enode://c0aa55a66963bc5321dd6633d029e3259458e68a2de
a591baee5b0bb96e1194ec7eea9bfd5fc2eaee518bfc58ed2c475a4574e9dae7a569625c6c88d89140ec7@[::]:30303INFO [06-13|10:45:15] IPC endpoint opened: /Users/xue/Library/Ethereum/geth.ipc
INFO [06-13|10:45:15] HTTP endpoint opened: http://10.18.25.15:8545
Welcome to the Geth JavaScript console!
instance: Geth/v1.6.0-unstable-105b37f1/darwin/go1.8
coinbase: 0xaae168cfde121cbbb2ceb3c7157f81a7dae82964
at block: 288 (Mon, 12 Jun 2017 12:37:45 CST)
 datadir: /Users/xue/Library/Ethereum
 modules: admin:1.0 debug:1.0 eth:1.0 miner:1.0 net:1.0 personal:1.0 rpc:1.0 txpool:1.0 web3:1.0

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