thanks for any response. :)
root@zdsx-Aspire-GX-781:/media/zdsx/Acer# bitcoin-cli -testnet -datadir="./bitcointestnetdata/" getbalance error code: -32601 error message: Method not found
root@zdsx-Aspire-GX-781:/media/zdsx/Acer# bitcoin-cli --version Bitcoin Core RPC client version v0.16.1.0-gdac5d68fc6cf