To simulate how to edit the Docker Daemon we'll launch a new daemon. The command below starts a new Docker 1.10 daemon.

The cluster-store parameter tells Docker where the Consul is running and the port. Docker uses Consul to register itself and discover other accessible Docker hosts.

The cluster-advertise is the IP address to register for this Docker instance. This is the IP address that Consul provides to other Docker daemons. In most cases this will be the Host's IP address. :0 advertises all ports.

docker run --privileged --name d1 -d \ --net=host katacoda/dind:1.10 -H 0.0.0.0:3375 \ --cluster-store=consul://[[HOST_IP]]:8500 \ --cluster-advertise=[[HOST_IP]]:0

Talk to the new Docker Daemon

To communicate with the launched daemon we can update our DOCKERHOST or define an alias and providing the host via -H_ parameter.

export DOCKER_HOST="[[HOST_IP]]:3375"

Like with the first host, we'll launch a second Docker 1.10 Daemon and register it with Consul. Notice we're registering a different IP address.

docker run --privileged --name d1 -d \ --net=host katacoda/dind:1.10 -H 0.0.0.0:3375 \ --cluster-store=consul://[[HOST_IP]]:8500 \ --cluster-advertise=[[HOST2_IP]]:0

Talk to the new Docker Daemon

As with the step before, we need to update the second host to talk to the daemon.

export DOCKER_HOST="[[HOST2_IP]]:3375"

With 1.10 we can now create a new network. All containers on the same network will be able to communicate with an other as if they where on the same box. If containers are not in the same network then they won't be able to communicate.

On one of the Docker hosts you need to create the network. In the example below the network will be of type overlay and called multihost-net.

docker network create -d overlay multihost-net

When new containers launch on any host they register themselves to the network. We'll explore this in the next step.

With the network created containers can register themselves and be available on multiple hosts.

In this example we're launching a web server called ws1 and registering it on the multihost-net network.

docker run -d --name ws1 --net=multihost-net katacoda/docker-http-server

Other hosts will be able to access this container via it's container name.

When registered to the network, containers launched on the second host can communicate with containers on the first host. By attaching to the multihost-net network our containers behave as if they're on the same machine.

docker run --net=multihost-net benhall/curl curl -Ss ws1