Published on 16 April 2015 by

With the impending release of Puppet Enterprise 3.8, we will be adding support for managing Docker and Docker containers.

For those of you who haven't yet had the chance to take a look at Docker, it enables apps to be quickly assembled from multiple components and eliminates some of the friction between development, QA, and production environments. With new Docker Platform tools Swarm, Machine and Compose, it is a growing component of modern infrastructure.

Docker was first released around two years ago, and since then it's increasingly used as the basis for testing infrastructure, development environments and all manner of production applications. Using Puppet to manage Docker allows users to more quickly and efficiently deploy, and start and stop containers. The Puppet Docker module was first released around the initial release of Docker, and has been a great community effort since then, with more than 200 pull requests and close to 100,000 downloads from the Puppet Forge alone.

Managing Docker

At its simplest, the Docker module allows you to install Docker with one line in your manifest:

include 'docker'

The module also supports specifying a version of Docker, binding to a TCP socket, providing DNS settings, selecting a storage driver and much more. Configuration can be done by passing parameters to the Docker class or via Hiera.

As well as installing and managing Docker, the module allows for downloading images from the Docker Hub. You can download images and keep them current, or download specific tags, all using the Puppet domain-specific language (DSL):

docker::image { 'nginx': }

docker::image { 'ubuntu':
  image_tag => 'precise'
}

The module also supports building images from Dockerfiles automatically.

Running Docker Instances

The module supports running and managing individual Docker containers. This doesn't aim to replace a higher-level scheduler like Kubernetes or Mesos, but has the advantage of not requiring additional software. The module is perfect for managing containers you want running everywhere, or for using Docker on existing infrastructure. The containers can run under the host init system (like systemd or sysvinit) or using Docker's built-in process manager.

docker::run { 'helloworld':
  image   => 'base',
  command => '/bin/sh -c "while true; do echo hello world; sleep 1; done"',
}

The module also supports mounting volumes, setting environment variables, running privileged containers, exposing ports and more. You can also execute commands within the context of running containers using the docker exec feature.

docker::exec { 'helloworld-uptime':
  detach    => true,
  container => 'helloworld',
  command   => 'uptime',
  tty       => true,
}

See How It Works

This short video walks through how to manage Docker with Puppet:

Examples of Usage

There are a number of examples of the module in action, including using Puppet to create and manage a Docker Swarm cluster:

  • Launch vNext app in Docker using Puppet. This example contains a fairly simple example using Vagrant to launch a Linux virtual machine, then Puppet to install Docker, build an image and run a container. For added spice, the container runs an ASP.NET vNext application.

  • Multihost containers connected with Consul. This lets you launch multiple hosts running simple application containers, and load-balance between them using Nginx.

  • Configure Docker Swarm using Puppet. This example builds a cluster of hosts running Docker Swarm.

The Future

The combination of Puppet and Docker presents a number of exciting opportunities for managing modern infrastructure, and this module is really just the start. If you're already using the two together, we'd like to hear how, and what the results are. We're also interested in your ideas for features or enhancements. Please share your input in the comments section of this post, or on the puppet-users mailing list. Thanks in advance!

Learn more

  • The Puppet Forge has more than 3,000 modules to choose from for automating many operations tasks with Puppet.
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