I’ve been wondering how can I add existing docker-swarm cluster to Rancher. Should I use https://github.com/rancher/swarm-agent instead of https://github.com/rancher/rancher/tree/master/agent ??
Looks like forum is pretty much dead 
I’ve found following link:
it’s pretty old - more than year but seems that it’s still impossible to import externally created swarm cluster into rancher.
Currently, you cannot add existing docker-swarm cluster. There is an open issue for it.