not sure if anyone has seen this before: I'm trying to mine a private chain. For whatever reason, after I was able to mine two blocks, I tried to mine the chain again and I get the following...(below)...any ideas to troubleshoot? TIA. JD

> miner.start(1)
INFO [07-03|19:18:00] Updated mining threads                   threads=1
INFO [07-03|19:18:00] Transaction pool price threshold updated price=18000000000
INFO [07-03|19:18:00] Starting mining operation 
> INFO [07-03|19:18:00] Commit new mining work                   number=3 txs=0 uncles=0 elapsed=104.511µs
  • It is ok to me, null is the result of miner.start(1), I think it is a javascript thing. But the blocks should generated correctly. Check eth.blockNumber.
    – Ismael
    Jul 4, 2017 at 1:44
  • that doesn't work
    – user12506
    Jul 5, 2017 at 13:34
  • Try starting a second node miner, which would mine it, as a workaround.
    – shonjs
    Feb 9, 2018 at 14:00

3 Answers 3


What is your geth command used to start your private network?
I also encountered this problem before and fixed it by adding the flag --dev, which uses a preconfigured private network.

reference: https://github.com/ethereum/go-ethereum/wiki/Command-Line-Options

  • where do you add --dev ? the commands i'm using are: geth --datadir ~/.jdchain99 init ~/.jdchain99 and geth --datadir ~/.jdchain99 --port "44444" --networkid 99 console
    – user12506
    Jul 4, 2017 at 16:10
  • that doesn't work
    – user12506
    Jul 5, 2017 at 13:34
  • what does your genesis file look like? Maybe it is because you set the mining difficulty too high so you'll have to wait longer. In my case, it started mining after I change the difficulty from 2000000 to 20. I wrote a tutorial about this: medium.com/@tina26919742/… Hope you find it useful:)
    – Tina Lee
    Jul 5, 2017 at 23:20

Try to increase the verbosity of the log to max level i.e 6 by giving this is command line while starting geth --verbosity 6. This will give us some clue. Generally the mining takes time to start because it is required to generate DAG


miner.start(1) is return null in some time. But that not mean that mining is not done. Mining process is done based on you system capacity. Also you can check your hash rate using eth.hashrate command in javascript console. Hope it helpful.

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