Start 4 instances of Consul with Docker

start-consuls.sh

# run the first server node expecting at least two more nodes to form a Consul cluster
docker run -d --name node1 -h node1 progrium/consul -server -bootstrap-expect 3

# other two nodes will join the first one using its IP (in Docker network)
JOIN_IP="$(docker inspect -f '{{.NetworkSettings.IPAddress}}' node1)"

# run second server node
docker run -d --name node2 -h node2 progrium/consul -server -join $JOIN_IP

# run third server node
docker run -d --name node3 -h node3 progrium/consul -server -join $JOIN_IP

# run fourth *client* node, this time exposing Consul ports to the host machine
# it'll be able to communicate with the cluster but will not participate in the consensus quorum
docker run -d -p 8400:8400 -p 8500:8500 -p 8600:53/udp --name node4 -h node4 progrium/consul -join $JOIN_IP