Set up Dockerized machines

The first step in getting the voting app deployed is to set up Docker machines for the swarm nodes. You could create these Docker hosts on different physical machines, virtual machines, or cloud providers.

For this example, we use Docker Machine to create two virtual machines on a single system. We’ll also verify the setup, and run some basic commmands to interact with the machines.

Prerequisites

• Docker Machine - These steps rely on use of Docker Machine (docker-machine), which comes auto-installed with both Docker for Mac and Docker for Windows.

• VirtualBox driver on Docker for Mac - On Docker for Mac, you’ll use docker-machine with the virtualbox driver to create machines. If you had a legacy installation of Docker Toolbox, you already have Oracle VirtualBox installed as part of that. If you started fresh with Docker for Mac, then you need to install VirtualBox independently. We recommend doing this rather than using the Toolbox installer because it can conflict with Docker for Mac. You can download VirtualBox for OS X hosts here, and follow install instructions. You do not need to start VirtualBox. The docker-machine create command will call it via the driver.

• Hyper-V driver on Docker for Windows - On Docker for Windows, you will use docker-machine with the Hyper-V driver to create machines. You will need to follow the instructions in the Hyper-V example reference topic to set up a new external network switch (a one-time task), reboot, and then create the machines (nodes) in an elevated PowerShell per those instructions.

Commands to create machines

The Docker Machine commands to create local virtual machines on Mac and Windows are are as follows.

Mac

docker-machine create --driver virtualbox HOST-NAME

Windows

docker-machine create -d hyperv --hyperv-virtual-switch "NETWORK-SWITCH"
MACHINE-NAME

This must be done in an elevated PowerShell, using a custom-created external network switch. See Hyper-V example.

Create manager and worker machines

Create two machines and name them to anticipate what their roles will be in the swarm:

• manager

• worker

Here is an example of creating the manager on Docker for Mac. Create this one, then do the same for worker.

$  docker-machine create --driver virtualbox manager
Running pre-create checks...
Creating machine...
(manager) Copying /Users/victoria/.docker/machine/cache/boot2docker.iso to /Users/victoria/.docker/machine/machines/manager/boot2docker.iso...
(manager) Creating VirtualBox VM...
(manager) Creating SSH key...
(manager) Starting the VM...
(manager) Check network to re-create if needed...
(manager) Waiting for an IP...
Waiting for machine to be running, this may take a few minutes...
Detecting operating system of created instance...
Waiting for SSH to be available...
Detecting the provisioner...
Provisioning with boot2docker...
Copying certs to the local machine directory...
Copying certs to the remote machine...
Setting Docker configuration on the remote daemon...
Checking connection to Docker...
Docker is up and running!
To see how to connect your Docker Client to the Docker Engine running on this virtual machine, run: docker-machine env manager

Verify machines are running and get IP addresses

Use docker-machine ls to verify that the machines are running and to get their IP addresses.

$ docker-machine ls
NAME       ACTIVE   DRIVER       STATE     URL                         SWARM   DOCKER        ERRORS
manager   *        virtualbox   Running   tcp://192.168.99.100:2376           v1.13.0-rc6
worker    -        virtualbox   Running   tcp://192.168.99.101:2376           v1.13.0-rc6

You now have two “Dockerized” machines, each running Docker Engine, accessible through the Docker CLI, and available to become swarm nodes.

You can also get the IP address of a particular machine:

$ docker-machine ip manager
192.168.99.100

You will need the IP address of the manager for a later step.

Interacting with the machines

There are a few ways to interact with these machines directly on the command line or programatically. We’ll cover two methods for managing the machines directly from the command line:

• Manage the machines from a pre-configured shell

• docker ssh into a machine

Manage the machines from a pre-configured shell

You can use docker-machine to set up environment variables in a shell that connect to the Docker client on a virtual machine. With this setup, the Docker commands you type in your local shell will run on the given machine. As an example, we’ll set up a shell to talk to our manager machine.

1. Run docker-machine env manager to get environment variables for the manager.

   $ docker-machine env manager
   export DOCKER_TLS_VERIFY="1"
   export DOCKER_HOST="tcp://192.168.99.100:2376"
   export DOCKER_CERT_PATH="/Users/victoriabialas/.docker/machine/machines/manager"
   export DOCKER_MACHINE_NAME="manager"
   export DOCKER_API_VERSION="1.25"
   # Run this command to configure your shell:
   # eval $(docker-machine env manager)
   

2. Connect your shell to the manager.

   On Mac:

   $ eval $(docker-machine env manager)
   

   On Windows PowerShell:

   & docker-machine.exe env manager | Invoke-Expression
   

   This sets environment variables for the current shell. The rest of the docker-machine commands we cover are the same on both Mac and Windows.

3. Run docker-machine ls again.

   $ docker-machine ls
   NAME      ACTIVE   DRIVER       STATE     URL                         SWARM   DOCKER        ERRORS
   manager   *        virtualbox   Running   tcp://192.168.99.100:2376           v1.13.0-rc6   
   worker    -        virtualbox   Running   tcp://192.168.99.101:2376           v1.13.0-rc6   
   

   The asterisk next manager indicates that the current shell is connected to that machine. Docker commands run in this shell will execute on the manager. (Note that you could change this by re-running the above commands to connect to the worker, or open multiple terminals to talk to multiple machines.)

If you use this method, you’ll need to re-configure the environment setup each time you want to switch between the manager and the worker, or keep two shells open.

ssh into a machine

Alternatively, you can use the command docker-machine ssh <MACHINE-NAME> to log into a machine.

$ docker-machine ssh manager
                        ##         .
                  ## ## ##        ==
               ## ## ## ## ##    ===
           /"""""""""""""""""\___/ ===
      ~~~ {~~ ~~~~ ~~~ ~~~~ ~~~ ~ /  ===- ~~~
           \______ o           __/
             \    \         __/
              \____\_______/
 _                 _   ____     _            _
| |__   ___   ___ | |_|___ \ __| | ___   ___| | _____ _ __
| '_ \ / _ \ / _ \| __| __) / _` |/ _ \ / __| |/ / _ \ '__|
| |_) | (_) | (_) | |_ / __/ (_| | (_) | (__|   <  __/ |
|_.__/ \___/ \___/ \__|_____\__,_|\___/ \___|_|\_\___|_|

  WARNING: this is a build from test.docker.com, not a stable release.

Boot2Docker version 1.13.0-rc6, build HEAD : 5ab2289 - Wed Jan 11 23:37:52 UTC 2017
Docker version 1.13.0-rc6, build 2f2d055

You do not have to set up docker-machine environment variables, as in the previous section, for docker ssh to work. You can run this command in that same shell you configured to talk to the manager, or in a new one, and it will work either way.

This tutorial will employ the docker ssh method to run commands on the machines, but which approach you use is really a matter of personal preference.

What’s next?

In the next step, we’ll create a swarm across these two Docker machines.