I know and I did that manual copy many times in the past. But I do not want that. I just want a new node to be like a "child" to the old ones and instead of going out in internet to use local nodes. That's all. So no interruption of existing nodes, just a smooth local sync. Once is done, to switch back to "normal" sync. I know it is a bitcoin-cli command but can't find right now. I remember I did something like that long time ago with Bitcoin Core/QT app, pointing to another node in LAN and grab the blocks from that local IP.