How to invalidate a block

[decryptit]

Hey guys so for educational purposes, how do I use Bitcoin Core to invalidate a block? And then how do I return to normal after? Thanks.

[achow101]

invalidateblock <blockhash> where <blockhash> is the hash of the block you wish to mark as invalid.

reconsiderblock <blockhash> where <blockhash> is the hash of the block and it's ancestors that you wish for the node to revalidate.

[decryptit]

ah ok. Thank you.

[decryptit]

invalidateblock <blockhash> where <blockhash> is the hash of the block you wish to mark as invalid.

reconsiderblock <blockhash> where <blockhash> is the hash of the block and it's ancestors that you wish for the node to revalidate.

So I just tried it. And I get a "Empty response". What does that mean?

[NotATether]

invalidateblock <blockhash> where <blockhash> is the hash of the block you wish to mark as invalid.

reconsiderblock <blockhash> where <blockhash> is the hash of the block and it's ancestors that you wish for the node to revalidate.

So I just tried it. And I get a "Empty response". What does that mean?

Some RPC calls have no response because it wouldn't make any sense to return anything. Invalidateblock is one such example - you already have the block hash passed as a parameter, what more could be returned?

[nc50lc]

So I just tried it. And I get a "Empty response". What does that mean?

That's the response if that command is executed successfully.
Otherwise, it'll return with "Block not found", "blockhash must be of length 64" or other errors.

You can immediately see that the block is invalidated in bitcoind with the lines InvalidChainFound: invalid block=n or in the logs (debug.log) file.

[decryptit]

ah ok. Thanks!