How can I empty the blockchain?

Question

I am trying to do a fast sync using geth --fast but I am getting this message:

blockchain not empty, fast sync disabled

How can I empty the blockchain to allow for fast sync?

score 16 · Accepted Answer · edited Jun 24 '17 at 05:32

16

To remove your blockchain with geth, run: geth removedb
Then:

Use --fast but you probably also need --cache=1024 (and --jitvm may also help). Without it, you are running with the default which is --cache=16.

A 50% speed increase is possible just by increasing the cache.

If you are starting from the beginning, use: geth --fast --cache=1024 --jitvm

Depending on your RAM, you can also try with higher values, like --cache=2048.

NOTE: The number after --cache= is the amount of memory allocated to the task of downloading the blockchain!!

Source

edited Jun 24 '17 at 05:32

Ismael

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answered Jun 05 '16 at 18:31

Astad

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Note this should now be geth removedb (no dash) – Derek May 31 '17 at 13:31
Is there a way to do this while geth --fast is already running? I want to leave it running long-term to answer RPC requests but don't want it to eat up my disk. – sudo Apr 07 '18 at 20:45
I mean a safe way. You can run geth removedb in a separate shell while geth --fast is running. I didn't have any problems doing this then sending a few xacts after, but I don't know if it's safe. Docs say nothing. – sudo Apr 07 '18 at 20:56

score 9 · Answer 2 · edited Apr 13 '17 at 13:01

The default datadir is:

Mac: ~/Library/Ethereum
Linux: ~/.ethereum
Windows: %APPDATA%/Ethereum

Delete the chaindata subdirectory that you find.

Run geth --fast --cache=1024 for a recommended way to sync the chain quickly (don't forget to use a bigger --cache with a value like 1024, otherwise the default is 16, and it won't sync as quickly).

EDIT: Running geth removedb is the simplest way to delete the blockchain in Geth.

score 6 · Answer 3 · answered Mar 14 '16 at 12:31

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If you have your blockchain partially or fully imported while starting geth, then using the --fast flag is ignored (the flag is disabled). To use the --fast flag you have to remove all of the data from your chaindata folder.

answered Mar 14 '16 at 12:31

romanoza

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Will starting fresh with --fast take less time than updating from the stored data? At what point would you say it's worth it? – TinyTimZamboni Jul 18 '17 at 02:58

score 1 · Answer 4 · answered Jan 11 '18 at 17:51

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use

geth --fast --cache=2048

it seems at least Mac does not provide the other options under go1.9.2:

flag provided but not defined: -jitvm

answered Jan 11 '18 at 17:51

Dennis Ng

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This is an old question (March 2016), early iterations of the --fast flag didn't allow restarting geth until it finished syncing, if you did restart it will switch to full mode. – Ismael Jan 12 '18 at 03:16

How can I empty the blockchain?

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