Start a Docker Swarm Clustern within "Docker in Docker (doid)"

docker_swarm_init_in_doid.sh

#!/bin/bash

# Init Swarm master
docker swarm init

# Get join token:
SWARM_TOKEN=$(docker swarm join-token -q worker)
echo $SWARM_TOKEN

# Get Swarm master IP (Docker for Mac xhyve VM IP)
SWARM_MASTER_IP=$(docker info | grep -w 'Node Address' | awk '{print $3}')
echo $SWARM_MASTER_IP

# Next, setup environment variables for what Docker version to use and how many worker nodes you want:

# Docker version or change it to dind and use the latest version
DOCKER_VERSION=18.05.0-ce-dind

# Number of workers
NUM_WORKERS=3

# Now, we can launch the worker nodes as containers and ask them to join our Docker Swarm cluster:

# Run NUM_WORKERS workers with SWARM_TOKEN
for i in $(seq "${NUM_WORKERS}"); do
	docker run -d --privileged --name worker-${i} --hostname=worker-${i} -p ${i}2375:2375 docker:${DOCKER_VERSION}
	docker --host=localhost:${i}2375 swarm join --token ${SWARM_TOKEN} ${SWARM_MASTER_IP}:2377
done

# The first docker run command might take some time due to the required Docker image needs to be downloaded, otherwise 
# it should only take a few seconds to setup the Swarm cluster!

# Check the docker swarm node cluster is around
docker node ls

For more information, like "how to tear down a node, rebalancing of instances, etc. check out the blog