Docker Provisioner

Provisioner name: "docker"

The Vagrant Docker provisioner can automatically install Docker, pull Docker containers, and configure certain containers to run on boot.

The docker provisioner is ideal for organizations that are using Docker as a means to distribute things like their application or services. Or, if you are just getting started with Docker, the Docker provisioner provides the easiest possible way to begin using Docker since the provisioner automates installing Docker for you.

As with all provisioners, the Docker provisioner can be used along with all the other provisioners Vagrant has in order to setup your working environment the best way possible. For example, perhaps you use Puppet to install services like databases or web servers but use Docker to house your application runtime. You can use the Puppet provisioner along with the Docker provisioner.

Note: This documentation is for the Docker provisioner. If you are looking for the Docker provider, visit the Docker provider documentation.

Options

The docker provisioner takes various options. None are required. If no options are required, the Docker provisioner will only install Docker for you (if it is not already installed).

• images (array) - A list of images to pull using docker pull. You can also use the pull_images function. See the example below this section for more information.

In addition to the options that can be set, various functions are available and can be called to configure other aspects of the Docker provisioner. Most of these functions have examples in more detailed sections below.

• build_image - Build an image from a Dockerfile.

• pull_images - Pull the given images. This does not start these images.

• post_install_provisioner - A provisioner block that runs post docker installation.

• run - Run a container and configure it to start on boot. This can only be specified once.

Building Images

The provisioner can automatically build images. Images are built prior to any configured containers to run, so you can build an image before running it. Building an image is easy:

Vagrant.configure("2") do |config|
  config.vm.provision "docker" do |d|
    d.build_image "/vagrant/app"
  end
end

The argument to build an image is the path to give to docker build. This must be a path that exists within the guest machine. If you need to get data to the guest machine, use a synced folder.

The build_image function accepts options as a second parameter. Here are the available options:

• args (string) - Additional arguments to pass to docker build. Use this to pass in things like -t "foo" to tag the image.

Pulling Images

The docker provisioner can automatically pull images from the Docker registry for you. There are two ways to specify images to pull. The first is as an array using images:

Vagrant.configure("2") do |config|
  config.vm.provision "docker",
    images: ["ubuntu"]
end

This will cause Vagrant to pull the "ubuntu" image from the registry for you automatically.

The second way to pull images is to use the pull_images function. Each call to pull_images will append the images to be pulled. The images variable, on the other hand, can only be used once.

Additionally, the pull_images function cannot be used with the simple configuration method for provisioners (specifying it all in one line).

Vagrant.configure("2") do |config|
  config.vm.provision "docker" do |d|
    d.pull_images "ubuntu"
    d.pull_images "vagrant"
  end
end

Running Containers

In addition to pulling images, the Docker provisioner can run and start containers for you. This lets you automatically start services as part of vagrant up.

Running containers can only be configured using the Ruby block syntax with the do...end blocks. An example of running a container is shown below:

Vagrant.configure("2") do |config|
  config.vm.provision "docker" do |d|
    d.run "rabbitmq"
  end
end

This will docker run a container with the "rabbitmq" image. Note that Vagrant uses the first parameter (the image name by default) to override any settings used in a previous run definition. Therefore, if you need to run multiple containers from the same image then you must specify the image option (documented below) with a unique name.

In addition to the name, the run method accepts a set of options, all optional:

• image (string) - The image to run. This defaults to the first argument but can also be given here as an option.

• cmd (string) - The command to start within the container. If not specified, then the container's default command will be used, such as the "CMD" command specified in the Dockerfile.

• args (string) - Extra arguments for docker run on the command line. These are raw arguments that are passed directly to Docker.

• auto_assign_name (boolean) - If true, the --name of the container will be set to the first argument of the run. By default this is true. If the name set contains a "/" (because of the image name), it will be replaced with "-". Therefore, if you do d.run "foo/bar", then the name of the container will be "foo-bar".

• daemonize (boolean) - If true, the "-d" flag is given to docker run to daemonize the containers. By default this is true.

• restart (string) - The restart policy for the container. Defaults to "always"

For example, here is how you would configure Docker to run a container with the Vagrant shared directory mounted inside of it:

Vagrant.configure("2") do |config|
  config.vm.provision "docker" do |d|
    d.run "ubuntu",
      cmd: "bash -l",
      args: "-v '/vagrant:/var/www'"
  end
end

In case you need to run multiple containers based off the same image, you can do so by providing different names and specifying the image parameter to it:

Vagrant.configure("2") do |config|
  config.vm.provision "docker" do |d|
    d.run "db-1", image: "user/mysql"
    d.run "db-2", image: "user/mysql"
  end
end

Other

This section documents some other things related to the Docker provisioner that are generally useful to know if you are using this provisioner.

Customize /etc/default/docker

To customize this file, use the post_install_provisioner shell provisioner.

Vagrant.configure("2") do |config|
  config.vm.provision "docker" do |d|
    d.post_install_provision "shell", inline:"echo export http_proxy='http://127.0.0.1:3128/' >> /etc/default/docker"
    d.run "ubuntu",
      cmd: "bash -l",
      args: "-v '/vagrant:/var/www'"
  end
end