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Creating a Docker Swarm Cluster

Today we're going to be spinning up Docker Swarm! Docker Swarm is an orchestration platform (like Kubernetes) that allows you to manage a containerized environment. In 2019, I believe that Kubernetes is far more popular in the world of DevOps, but I still want to see what Docker Swarm is all about.. so let's get started!

Prerequisites;
1. Three Linux machines (I'm using Ubuntu 18.04.1 LTS servers)
2. Docker 1.12 or newer installed on all machines. At the  time of writing this, I have version 10.06.1-ce (ce stands for community edition)
3. SSH access to said machines
4. The following ports open; TCP port 2377, TCP/UDP port 7946, and UDP port 4789
5. Some type of naming convention - Because we're going to have a manager machine, pick a naming convention that is easy to remember. For example, I named my VM's dockerswarm01, dockerswarm02, and dockerswarm03. dockerswarm01 will be the management machine

For step 1, let's go ahead and SSH into each of the Linux machines. I used MobaXTerm for this so I can SSH into all from the same window. You can also use PowerShell or a Linix/OS X Terminal for this as well.


Now, ensure you're running as root by running sudo su - and typing in your password.

Next, let's initiate the Swarm cluster by running docker swarm init --advertise-addr <ip of your swarm manager>

Once you do that, your screen should look something similar to the below screenshot (yours will show a token and your current nodes GUID).


On your two other Linux machines, you're going to run the full command under the "To add a worker to this swarm, run the following command:". Ensure you run the command with the full token.

If the connection is successful, you should see a screen like the screenshot below. If you do not see this, please confirm the following;
1. Docker is running on the machine
2. You have network connectivity to the Swarm Manager
3. All of the ports were open from the pre-req section


If you run docker info on the manager, you should see some output about containers running, if swarm is active, etc.

Finally, go ahead and run docker node ls to see all of your nodes in your Docker Swarm cluster.


That's it! You've spun up your Docker Swarm cluster. Thanks for reading.

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