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Create a swarm for development

This section tells you how to create a Docker Swarm on your network to use only for debugging, testing, or development purposes. You can also use this type of installation if you are developing custom applications for Docker Swarm or contributing to it.

Caution: Only use this set up if your network environment is secured by a firewall or other measures.

Prerequisites

You install Docker Swarm on a single system which is known as your Docker Swarm manager. You create the cluster, or swarm, on one or more additional nodes on your network. Each node in your swarm must:

be accessible by the swarm manager across your network
have Docker Engine 1.6.0+ installed
open a TCP port to listen for the manager

You can run Docker Swarm on Linux 64-bit architectures. You can also install and run it on 64-bit Windows and Max OSX but these architectures are not regularly tested for compatibility in the BETA phase.

Take a moment and identify the systems on your network that you intend to use. Ensure each node meets the requirements listed above.

Pull the swarm image and create a cluster.

The easiest way to get started with Swarm is to use the official Docker image.

Pull the swarm image.
```
 $ docker pull swarm
```
Create a Swarm cluster using the docker command.
```
 $ docker run --rm swarm create
 6856663cdefdec325839a4b7e1de38e8 # 
```
The create command returns a unique cluster ID (cluster_id). You'll need this ID when starting the Docker Swarm agent on a node.

Create swarm nodes

Each Swarm node will run a Swarm node agent. The agent registers the referenced Docker daemon, monitors it, and updates the discovery backend with the node's status.

This example uses the Docker Hub based token discovery service. Log into each node and do the following.

Start the Docker daemon with the -H flag. This ensures that the Docker remote API on Swarm Agents is available over TCP for the Swarm Manager.
```
 $ docker daemon -H tcp://0.0.0.0:2375
```
Note: versions of docker prior to 1.8 used the -d flag instead of the docker daemon subcommand.
Register the Swarm agents to the discovery service. The node's IP must be accessible from the Swarm Manager. Use the following command and replace with the proper node_ip and cluster_id to start an agent:
```
 docker run -d swarm join --addr=<node_ip:2375> token://<cluster_id>
```
For example:
```
 $ docker run -d swarm join --addr=172.31.40.100:2375 token://6856663cdefdec325839a4b7e1de38e8
```

Configure a manager

Once you have your nodes established, set up a manager to control the swarm.

Start the Swarm manager on any machine or your laptop.

The following command illustrates how to do this:
```
 docker run -d -p <manager_port>:2375 swarm manage token://<cluster_id>
```
The manager is exposed and listening on <manager_port>.

Once the manager is running, check your configuration by running docker info as follows:

 docker -H tcp://<manager_ip:manager_port> info

For example, if you run the manager locally on your machine:

 $ docker -H tcp://0.0.0.0:2375 info
 Containers: 0
 Nodes: 3
  agent-2: 172.31.40.102:2375
 	└ Containers: 0
 	└ Reserved CPUs: 0 / 1
 	└ Reserved Memory: 0 B / 514.5 MiB
  agent-1: 172.31.40.101:2375
 	└ Containers: 0
 	└ Reserved CPUs: 0 / 1
 	└ Reserved Memory: 0 B / 514.5 MiB
  agent-0: 172.31.40.100:2375
 	└ Containers: 0
 	└ Reserved CPUs: 0 / 1
 	└ Reserved Memory: 0 B / 514.5 MiB

If you are running a test cluster without TLS enabled, you may get an error. In that case, be sure to unset DOCKER_TLS_VERIFY with:

$ unset DOCKER_TLS_VERIFY

Using the docker CLI

You can now use the regular Docker CLI to access your nodes:

docker -H tcp://<manager_ip:manager_port> info
docker -H tcp://<manager_ip:manager_port> run ...
docker -H tcp://<manager_ip:manager_port> ps
docker -H tcp://<manager_ip:manager_port> logs ...

List nodes in your cluster

You can get a list of all your running nodes using the swarm list command:

docker run --rm swarm list token://<cluster_id>
<node_ip:2375>

For example:

$ docker run --rm swarm list token://6856663cdefdec325839a4b7e1de38e8
172.31.40.100:2375
172.31.40.101:2375
172.31.40.102:2375

TLS

Swarm supports TLS authentication between the CLI and Swarm but also between Swarm and the Docker nodes. However, all the Docker daemon certificates and client certificates must be signed using the same CA-certificate.

In order to enable TLS for both client and server, the same command line options as Docker can be specified:

swarm manage --tlsverify --tlscacert=<CACERT> --tlscert=<CERT> --tlskey=<KEY> [...]

Please refer to the Docker documentation for more information on how to set up TLS authentication on Docker and generating the certificates.

Note: Swarm certificates must be generated with extendedKeyUsage = clientAuth,serverAuth.

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