上篇介绍了以太坊开发环境，本篇介绍下如何使用私有链。

使用私有链之前，先要创建创世块genesis。

初始化私有链

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{
 "nonce": "0x0000000000000042",
 "timestamp": "0x0",
 "parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
 "mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000",
 "extraData": "0x",
 "gasLimit": "0x80000000",
 "difficulty": "0x3",
 "coinbase": "0x3333333333333333333333333333333333333333",
 "config":{
    "chainId": 55,
    "homesteadBlock": 0,
    "eip155Block": 0
 },
 "alloc": {}
}

将上述内容写入文件genesis.json中，字段的解释如下:

nonce：64位随机数，用于挖矿
timestamp：创世块的时间戳
parentHash：上一个区块的hash值，因为是创世块，所以这个值是0
mixhash：与 nonce 配合用于挖矿，由上一个区块的一部分生成的 hash。(这个在bitcoin中没有，具体是干什么用的呢？？？)
extraData：附加信息，任意填写
gasLimit ：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，因为我们就测试链，所以随意填写。
difficulty：难度值，越大越难 (bitcoin是难度值越小越难，注意下不同，随后抽空看下以太坊的难度值)
coinbase：矿工账号，第一个区块挖出后将给这个矿工账号发送奖励的以太币。(感觉貌似没用？？？也可能使用的方式不对，待测)
alloc： 预设账号以及账号的以太币数量，测试链挖矿比较容易可以不配置
chainId 指定了独立的区块链网络 ID，不同 ID 网络的节点无法互相连接。

创建了genesis文件之后，初始化私有链，命令为geth --datadir=data0 init genesis.json
执行结果如下：

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hadoop@ubuntu:~/blockchain/ethereum$ geth --datadir data0 init genesis.json
WARN [08-23|08:39:07.353] Sanitizing cache to Go's GC limits       provided=1024 updated=662
INFO [08-23|08:39:07.355] Maximum peer count                       ETH=25 LES=0 total=25
INFO [08-23|08:39:07.357] Allocated cache and file handles         database=/home/hadoop/blockchain/ethereum/data0/geth/chaindata cache=16 handles=16
INFO [08-23|08:39:07.400] Persisted trie from memory database      nodes=0 size=0.00B time=14.163µs gcnodes=0 gcsize=0.00B gctime=0s livenodes=1 livesize=0.00B
INFO [08-23|08:39:07.405] Successfully wrote genesis state         database=chaindata                                             hash=4a306e…543a63
INFO [08-23|08:39:07.405] Allocated cache and file handles         database=/home/hadoop/blockchain/ethereum/data0/geth/lightchaindata cache=16 handles=16
INFO [08-23|08:39:07.420] Persisted trie from memory database      nodes=0 size=0.00B time=3.02µs   gcnodes=0 gcsize=0.00B gctime=0s livenodes=1 livesize=0.00B
INFO [08-23|08:39:07.420] Successfully wrote genesis state         database=lightchaindata                                             hash=4a306e…543a63

如上则初始化成功，下面开始使用私有链

使用私有链

执行命令geth --datadir data0 --networkid 1108 console进入geth的终端，此时就和上篇的开发环境一样了，同样的挖矿流程来一套就ok了。

别的命令不累赘了，有需要可以翻翻之前的文章，只记录下执行miner.start()命令之后的输出

miner.start()之后，先生成DAG，会展示进度，输出的关键字为Generating DAG in progress
随后在这个过程中会伴随块的产生，输出的关键字为Successfully sealed new block
具体输出如下:

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> miner.start(2)
INFO [08-22|09:10:31.066] Updated mining threads                   threads=2
INFO [08-22|09:10:31.067] Transaction pool price threshold updated price=18000000000
null
> INFO [08-22|09:10:31.109] Starting mining operation
INFO [08-22|09:10:31.109] Commit new mining work                   number=1 txs=0 uncles=0 elapsed=118.785µs
INFO [08-22|09:10:31.369] Generating DAG in progress               epoch=1 percentage=19 elapsed=2m3.630s
INFO [08-22|09:10:37.935] Generating DAG in progress               epoch=1 percentage=20 elapsed=2m10.196s
INFO [08-22|09:10:44.781] Generating DAG in progress               epoch=1 percentage=21 elapsed=2m17.043s
INFO [08-22|09:10:52.263] Generating DAG in progress               epoch=1 percentage=22 elapsed=2m24.524s
INFO [08-22|09:10:59.633] Generating DAG in progress               epoch=1 percentage=23 elapsed=2m31.895s
INFO [08-22|09:11:06.632] Generating DAG in progress               epoch=1 percentage=24 elapsed=2m38.894s
INFO [08-22|09:11:13.379] Generating DAG in progress               epoch=1 percentage=25 elapsed=2m45.641s
INFO [08-22|09:11:20.101] Generating DAG in progress               epoch=1 percentage=26 elapsed=2m52.362s
INFO [08-22|09:11:26.798] Generating DAG in progress               epoch=1 percentage=27 elapsed=2m59.059s
INFO [08-22|09:11:34.509] Generating DAG in progress               epoch=1 percentage=28 elapsed=3m6.770s
INFO [08-22|09:11:41.806] Generating DAG in progress               epoch=1 percentage=29 elapsed=3m14.068s
INFO [08-22|09:11:49.068] Generating DAG in progress               epoch=1 percentage=30 elapsed=3m21.329s
> eth.accounts.INFO [08-22|09:11:56.419] Generating DAG in progress               epoch=1 percentage=31 elapsed=3m28.680s
> eth.accounts
["0x729ef979ace85837425a46055e9b7264c32c21e6", "0xf5727a89f2b4dfb58ac199755823a22935fb9fbf"]
> INFO [08-22|09:12:03.486] Generating DAG in progress               epoch=1 percentage=32 elapsed=3m35.747s
INFO [08-22|09:12:10.594] Generating DAG in progress               epoch=1 percentage=33 elapsed=3m42.855s
INFO [08-22|09:12:17.769] Generating DAG in progress               epoch=1 percentage=34 elapsed=3m50.031s
INFO [08-22|09:12:24.648] Generating DAG in progress               epoch=1 percentage=35 elapsed=3m56.910s
INFO [08-22|09:12:31.965] Generating DAG in progress               epoch=1 percentage=36 elapsed=4m4.226s
INFO [08-22|09:12:38.996] Generating DAG in progress               epoch=1 percentage=37 elapsed=4m11.257s
INFO [08-22|09:12:46.210] Generating DAG in progress               epoch=1 percentage=38 elapsed=4m18.472s
INFO [08-22|09:12:52.898] Generating DAG in progress               epoch=1 percentage=39 elapsed=4m25.159s
INFO [08-22|09:12:59.072] Generating DAG in progress               epoch=1 percentage=40 elapsed=4m31.333s
INFO [08-22|09:13:03.176] Successfully sealed new block            number=1 hash=5b2050…9754cd
INFO [08-22|09:13:03.234] 🔨 mined potential block                  number=1 hash=5b2050…9754cd
INFO [08-22|09:13:03.237] Commit new mining work                   number=2 txs=0 uncles=0 elapsed=2.910ms
INFO [08-22|09:13:06.398] Successfully sealed new block            number=2 hash=ecb729…78a768
INFO [08-22|09:13:06.399] 🔨 mined potential block                  number=2 hash=ecb729…78a768
INFO [08-22|09:13:06.399] Commit new mining work                   number=3 txs=0 uncles=0 elapsed=123.882µs
INFO [08-22|09:13:07.162] Generating DAG in progress               epoch=1 percentage=41 elapsed=4m39.423s
INFO [08-22|09:13:08.005] Successfully sealed new block            number=3 hash=265505…2113c3
INFO [08-22|09:13:08.005] 🔨 mined potential block                  number=3 hash=265505…2113c3
INFO [08-22|09:13:08.005] Commit new mining work                   number=4 txs=0 uncles=0 elapsed=93.513µs
INFO [08-22|09:13:10.197] Successfully sealed new block            number=4 hash=07a7f2…9c3877
INFO [08-22|09:13:10.197] 🔨 mined potential block                  number=4 hash=07a7f2…9c3877
INFO [08-22|09:13:10.218] Commit new mining work                   number=5 txs=0 uncles=0 elapsed=118.561µs
INFO [08-22|09:13:11.572] Successfully sealed new block            number=5 hash=80c62e…229bb9
INFO [08-22|09:13:11.573] 🔨 mined potential block                  number=5 hash=80c62e…229bb9
INFO [08-22|09:13:11.573] Commit new mining work                   number=6 txs=0 uncles=0 elapsed=134.57µs
INFO [08-22|09:13:13.347] Generating DAG in progress               epoch=1 percentage=42 elapsed=4m45.609s
INFO [08-22|09:13:19.373] Generating DAG in progress               epoch=1 percentage=43 elapsed=4m51.634s
INFO [08-22|09:13:26.582] Generating DAG in progress               epoch=1 percentage=44 elapsed=4m58.844s
INFO [08-22|09:13:30.189] Successfully sealed new block            number=6 hash=c8e518…fbad3c
INFO [08-22|09:13:30.190] 🔗 block reached canonical chain          number=1 hash=5b2050…9754cd
INFO [08-22|09:13:30.192] 🔨 mined potential block                  number=6 hash=c8e518…fbad3c
INFO [08-22|09:13:30.203] Commit new mining work                   number=7 txs=0 uncles=0 elapsed=152.206µs
INFO [08-22|09:13:32.481] Generating DAG in progress               epoch=1 percentage=45 elapsed=5m4.743s
INFO [08-22|09:13:34.301] Successfully sealed new block            number=7 hash=b286af…979418
INFO [08-22|09:13:34.302] 🔗 block reached canonical chain          number=2 hash=ecb729…78a768
INFO [08-22|09:13:34.302] 🔨 mined potential block                  number=7 hash=b286af…979418
INFO [08-22|09:13:34.302] Commit new mining work                   number=8 txs=0 uncles=0 elapsed=135.716µs
INFO [08-22|09:13:35.776] Successfully sealed new block            number=8 hash=1496cd…e06258
INFO [08-22|09:13:35.778] 🔗 block reached canonical chain          number=3 hash=265505…2113c3
INFO [08-22|09:13:35.778] 🔨 mined potential block                  number=8 hash=1496cd…e06258
INFO [08-22|09:13:35.796] Commit new mining work                   number=9 txs=0 uncles=0 elapsed=905.496µs
INFO [08-22|09:13:38.655] Generating DAG in progress               epoch=1 percentage=46 elapsed=5m10.916s
INFO [08-22|09:13:40.374] Successfully sealed new block            number=9 hash=8d7fa0…676de1
INFO [08-22|09:13:40.375] 🔗 block reached canonical chain          number=4 hash=07a7f2…9c3877
INFO [08-22|09:13:40.375] 🔨 mined potential block                  number=9 hash=8d7fa0…676de1
INFO [08-22|09:13:40.386] Commit new mining work                   number=10 txs=0 uncles=0 elapsed=11.551ms
INFO [08-22|09:13:44.547] Generating DAG in progress               epoch=1 percentage=47 elapsed=5m16.809s
INFO [08-22|09:13:52.465] Generating DAG in progress               epoch=1 percentage=48 elapsed=5m24.726s
INFO [08-22|09:13:52.692] Successfully sealed new block            number=10 hash=687e93…116aa7
INFO [08-22|09:13:52.693] 🔗 block reached canonical chain          number=5  hash=80c62e…229bb9
INFO [08-22|09:13:52.693] 🔨 mined potential block                  number=10 hash=687e93…116aa7
INFO [08-22|09:13:52.693] Commit new mining work                   number=11 txs=0 uncles=0 elapsed=112.383µs
INFO [08-22|09:13:55.432] Successfully sealed new block            number=11 hash=09a872…2054a1
INFO [08-22|09:13:55.432] 🔗 block reached canonical chain          number=6  hash=c8e518…fbad3c
INFO [08-22|09:13:55.432] 🔨 mined potential block                  number=11 hash=09a872…2054a1
INFO [08-22|09:13:55.432] Commit new mining work                   number=12 txs=0 uncles=0 elapsed=124.793µs
INFO [08-22|09:13:57.145] Successfully sealed new block            number=12 hash=e9f8d3…e1c6ee
INFO [08-22|09:13:57.145] 🔗 block reached canonical chain          number=7  hash=b286af…979418
INFO [08-22|09:13:57.145] 🔨 mined potential block                  number=12 hash=e9f8d3…e1c6ee
INFO [08-22|09:13:57.145] Commit new mining work                   number=13 txs=0 uncles=0 elapsed=111.673µs
INFO [08-22|09:13:59.277] Generating DAG in progress               epoch=1 percentage=49 elapsed=5m31.538s