In the original github issue for geth --fast feature karalabe writes:

After a node managed to successfully sync with the network, fast sync is forever disabled.

Is there a way to circumvent this? I don't want to run the full node all the time, I want to check my wallet every other few weeks and the full sync takes forever.

  • Hi, @eth I have seen the question that you think is a duplicate of this question before I posted this here. This is not a duplicate, I am asking how to disable the mechanism that prevents me to run --fast afterwards, and if it is possible. These questions are not answered in the original question. Jun 14, 2016 at 10:07
  • ok, though circumventing security is usually inadvisable :)
    – eth
    Jun 14, 2016 at 10:18
  • Yeah I am aware of the risk. Although I think that the argumentation used "This is the reason why fast sync is only a one shot sync mechanism: people will likely verify that they are indeed up to date and correctly when they initially sync, but probably will assume nothing's wrong afterwards." can be equally applied to doing fast sync afterwards. Jun 14, 2016 at 10:27
  • there is interesting post here: reddit.com/r/ethereum/comments/3y9316/geth_fast_option_question Jun 16, 2016 at 11:12

2 Answers 2


Maybe you can remove your blockchain with geth removedb and do a --fast again. If not faster, it will for sure spare some diskspace. Worth a try I think. Let us know. It could be interesting if you are more than 1500 blocks late, because --fast takes a pivot at minus 1500 blocks from now and then downloads all the blocks from there (and only headers of the previous genesis to the 1500th from now)


You could either run a geth --syncmode light client or a parity --pruning fast client.

Geth light will only maintain a mininmal state snapshot of around 200 MB on your disk, Parity will continuously prune the state and therefore you only need 10GB on your disk.

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