Can bitcoind and btcd share a datadir?

Question

I've already fully synced the blockchain with btcd, can I point bitcoind at the same datadir and use its contents?

Answer 1

No, they’re completely incompatible.

Answer 2

You can't use the same datadir, but you can tell btcd to connect to your locally-running bitcoind instance in order to do the initial blockchain sync. This means that you'll end up with two copies of the blockchain (one for bitcoind and one for btcd) but the sync will happen much faster than starting btcd with default settings.

In your btcd.conf file:

; only connect to locally-running node
connect=127.0.0.1

; no need to query for other nodes
nodnsseed=1

; listen on a port other than the default (if bitcoind is already running on the default)
listen=127.0.0.1:8336

; secure the RPC API so that you can interface with your sycing node by using btcctl
rpcuser=<rpcusername>
rpcpassword=<rpcuserpassword>

; sync with indexes enabled
txindex=1
addrindex=1

Now start btcd. It should start, but no peers will be connected - you can verify this by running btcctl getpeerinfo and you'll get [].

With btcd running, force your bitcoind node to connect to it by using the command bitcoin-cli --rpcuser=<bitcoindrpcusername> --rpcpassword=<bitcoindrpcuserpassword> addnode 127.0.0.1:8336 'onetry'

Now run btcctl getpeerinfo again, and you should see that your local bitcoind node is connected. btcd has started to sync and it should only take a few hours to sync from the local node. This is much faster than the days it would take to sync over the internet.