以太坊（ETH）同步公链数据

前后端分离的启动

这种方式既可以随时和geth交互，又不影响geth在后台运行，在服务器上非常有必要。先用nohup在后台进程中跑geth

> nohup geth --syncmode full --datadir /data1/eth-sync/online --cache 512 --maxpeers 50 &

INFO [09-27|07:37:04.628] Initialising Ethereum protocol           versions="[63 62]" network=1
INFO [09-27|07:37:04.629] Loaded most recent local header          number=1662235 hash=a9e294…913d4c td=25531653857731585264 age=2y4mo1d
INFO [09-27|07:37:04.629] Loaded most recent local full block      number=1662235 hash=a9e294…913d4c td=25531653857731585264 age=2y4mo1d
INFO [09-27|07:37:04.629] Loaded most recent local fast block      number=1662235 hash=a9e294…913d4c td=25531653857731585264 age=2y4mo1d
INFO [09-27|07:37:04.630] Loaded local transaction journal         transactions=0 dropped=0
INFO [09-27|07:37:04.630] Regenerated local transaction journal    transactions=0 accounts=0
INFO [09-27|07:37:04.630] Starting P2P networking 
INFO [09-27|07:37:06.795] UDP listener up                          self=enode://dd80bcf5bd935067e454e8b772253e3a7d745efb4a22f40a0bf865501c26b5dac78f5918bff36a1d167308c94d8742069f6752ce67c8030d9f0f8f70336a5819@[::]:30303
INFO [09-27|07:37:06.795] RLPx listener up                         self=enode://dd80bcf5bd935067e454e8b772253e3a7d745efb4a22f40a0bf865501c26b5dac78f5918bff36a1d167308c94d8742069f6752ce67c8030d9f0f8f70336a5819@[::]:30303
INFO [09-27|07:37:06.797] IPC endpoint opened                      url=/data1/eth-sync/online/geth.ipc
INFO [09-27|07:37:56.795] Block synchronisation started 
INFO [09-27|07:38:00.076] Imported new chain segment               blocks=2 txs=36 mgas=0.886 elapsed=1.137s mgasps=0.780 number=1662237 hash=f7d2f8…3920f1 age=2y4mo1d cache=105.16kB
INFO [09-27|07:38:00.431] Imported new chain segment               blocks=23 txs=1055 mgas=22.973 elapsed=354.861ms mgasps=64.737 number=1662260 hash=cc7e22…223ee9 age=2y4mo1d cache=2.23mB
INFO [09-27|07:38:00.947] Imported new chain segment               blocks=141 txs=856  mgas=28.562 elapsed=478.099ms mgasps=59.741 number=1662401 hash=557a65…a61dbd age=2y4mo1d cache=4.36mB
INFO [09-27|07:38:01.508] Imported new chain segment               blocks=147 txs=1068 mgas=36.480 elapsed=536.501ms mgasps=67.996 number=1662548 hash=00d1f3…827391 age=2y4mo1d cache=5.50mB
INFO [09-27|07:38:02.106] Imported new chain segment               blocks=146 txs=667  mgas=39.514 elapsed=594.797ms mgasps=66.433 number=1662694 hash=21fe04…4227cb age=2y4mo1d cache=6.10mB
INFO [09-27|07:38:04.766] Imported new chain segment               blocks=141 txs=2870 mgas=271.393 elapsed=2.656s    mgasps=102.177 number=1662835 hash=fbfdab…ec1102 age=2y4mo1d cache=14.44mB
INFO [09-27|07:38:09.719] Imported new chain segment               blocks=924 txs=7872 mgas=410.690 elapsed=4.941s    mgasps=83.117  number=1663759 hash=705b4c…2fdffb age=2y4mo1d cache=16.40mB

使用attach命令开启交互界面，geth启动时会在规定的data目录生成ipc，把attach的地址设置成该ipc所在地址，即可再次进入交互界面，用exit退出也不会影响后台进程。

> geth attach ipc:/data1/eth-sync/online/geth.ipc

#查看同步状态
> eth.syncing
{
  currentBlock: 1725364,
  highestBlock: 6407815,
  knownStates: 0,
  pulledStates: 0,
  startingBlock: 1662235
}

#查看同步高度
> eth.blockNumber
1725615

#查看节点数
> net.peerCount
5

#安全退出
> exit