website/www: feature preview docker provider
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Mitchell Hashimoto
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page_title: "Vagrant 1.6 Feature Preview: Docker-Based Development Environments"
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title: "Feature Preview: Docker-Based Development Environments"
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author: "Mitchell Hashimoto"
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author_url: https://github.com/mitchellh
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---
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Vagrant 1.6 comes with a new built-in provider: Docker. The Docker provider
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allows Vagrant to manage development environments that run within containers,
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rather than virtual machines. This works without any additional software
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required on Linux, Mac OS X, and Windows.
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The Docker provider in Vagrant makes it incredibly easy to keep the workflow
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you're used to with both Vagrant and Docker while gaining all the benefits
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of Vagrant: cross-platform portability, synced folders, networking,
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provisioners, vagrant share, plugins, etc.
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On platforms that don't support Linux Containers natively such as
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Mac OS X and Windows, Vagrant automatically brings up and shares a proxy
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virtual machine to run Docker. This proxy VM is completely customizable,
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and Vagrant ensures that synced folders and networking work as you would
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expect. Users of Vagrant don't need to worry about doing any of
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this manually.
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Read on to learn more.
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READMORE
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### Demo
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We've prepared a few demo videos below showcasing the Docker provider
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in Vagrant before we get into the details in this blog post. We recommend
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watching these videos in order.
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<iframe src="//player.vimeo.com/video/93167741" width="680" height="382" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>
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<iframe src="//player.vimeo.com/video/93176926" width="680" height="382" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>
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<iframe src="//player.vimeo.com/video/93180496" width="680" height="382" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>
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### Docker, With Vagrant
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Vagrant is built to be the best way to manage development environments
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for applications built with any technology. In many cases, virtual machines
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are the best answer for this, so Vagrant has used virtual machines for years.
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But Vagrant isn't tied to virtual machines at all, and in some cases containers
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are the best option. With the Docker provider, Vagrant builds development
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environments with Linux containers built with Docker.
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Users of Docker who use Vagrant for development get what Vagrant is best known
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for: [the Vagrant workflow](http://mitchellh.com/the-tao-of-vagrant). One
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`vagrant up` on Linux, Mac, or Windows and developers get a consistent
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development environment that they can work on. No extra steps other than
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installing Vagrant, no clicking, and no discontinuity between operating
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systems.
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And due to Vagrant's flexibility, you keep the identical workflow
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for managing systems that don't use Docker. This might be another Linux-based
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system, or it might even be something completely different such as a
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[Windows-based development environment](/blog/feature-preview-vagrant-1-6-windows.html).
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With Vagrant, the workflow is always the same.
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### Docker Host VM
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Linux containers do not run natively on non-Linux machines. If your developers
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are on Mac or Windows, they can't run Docker containers natively. Vagrant
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detects these cases and automatically spins up a Linux virtual machine to
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run the Docker containers.
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Vagrant then shares this virtual machine for all Docker-based development
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environments with Vagrant. That means with just a single virtual machine,
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Vagrant can manage many Docker environments.
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Even when using a Docker host virtual machine, synced folders, SSH, and
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other features of Vagrant work just as you expect, uniformly across every
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platform.
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If Vagrant is being used with Docker on Linux, Vagrant won't automatically
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spin up a virtual machine and instead will run Docker natively.
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By default, Vagrant spins up a default virtual machine with Docker installed.
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But you can also specify **any Vagrant-managed machine** as the Docker
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host machine. An example is shown below:
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<pre class="prettyprint">
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Vagrant.configure("2") do |config|
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config.vm.provider "docker" do |d|
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d.vagrant_vagrantfile = "../docker-host/Vagrantfile"
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end
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end
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</pre>
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With the configuration above, Vagrant will use the default machine
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in the Vagrantfile specified as the Docker host. This is _very powerful_.
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With this feature, you can have Vagrant automatically manage a Docker
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host using any operating system that Vagrant supports, such as Ubuntu,
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RHEL, or CoreOS. And you can change this host VM for each development
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environment if you want.
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Vagrant is smart: if the host VM matches multiple Vagrantfiles, the single
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VM will be shared. Vagrant won't spin up multiple VMs if it doesn't have to.
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Because Vagrant is just re-using Vagrant underneath the covers to manage
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this host VM, you're able to use all the features of Vagrant with this VM:
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provisioners, synced folders, networking, etc. It is the ultimate flexibility
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in building a development environment that is correct for your project.
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### Dockerfiles or Docker Index
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The Docker provider in Vagrant is flexible and supports Docker containers
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from both local Dockerfiles and the Docker Index. This is useful in being
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able to iterate on a Dockerfile while also depending perhaps on something
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in an index.
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As an example, below is a Vagrantfile that could be used for a web
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development environment:
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<pre class="prettyprint">
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Vagrant.configure("2") do |config|
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config.vm.define "app" do |app|
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app.vm.provider "docker" do |d|
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d.build_dir = "."
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d.link "db"
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end
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end
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config.vm.define "db" do |app|
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app.vm.provider "docker" do |d|
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d.image = "paintedfox/postgresql"
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d.name = "db"
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end
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end
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end
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</pre>
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In the example above, we build the "app" environment from a Dockerfile
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that might build the container for our web application. This app environment
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then links to the "db" environment which uses the "paintedfox/postgresql"
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image to provide a PostgreSQL database.
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And in both cases, synced folders work as you would expect with Vagrant,
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so data can be persisted outside the containers and file modifications
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can be mirrored back into the containers.
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### Containers with SSH
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The general approach to Docker containers is to have each container
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be a single application instead of a complete multi-process system. In these
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cases, SSH is unavailable so you can't take advantage of Vagrant features
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such as `vagrant ssh`, provisioners, etc. However, if the container _does_
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support SSH, then all these features are supported and do work.
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For example, the Vagrantfile below uses
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[baseimage](https://github.com/phusion/baseimage-docker) created by Phusion
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which behaves more like a lightweight virtual machine.
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<pre class="prettyprint">
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Vagrant.configure("2") do |config|
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config.vm.provider "docker" do |d|
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d.cmd = ["/sbin/my_init", "--enable-insecure-key"]
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d.image = "phusion/baseimage"
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d.has_ssh = true
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end
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config.ssh.username = "root"
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config.ssh.private_key_path = "phusion.key"
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end
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</pre>
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Assuming you have "phusion.key" in place, the above will start the container,
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wait for SSH, and run any provisioners, set any hostnames, etc. Additionally,
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`vagrant ssh` works perfectly.
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And again, all of these features work whether you're running Docker natively
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or running Docker via an automatically managed host VM from Vagrant.
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### Docker-Specific Enhancements
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So far, the behavior and workflow of using Docker with Vagrant has been
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identical to if you had been using Vagrant with VirtualBox, VMware, or a
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cloud service such as EC2.
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However, Vagrant 1.6 does introduce some new commands that are made
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specifically for the Docker provider to give some additional utility to
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Vagrant.
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`docker-logs` shows the logs from a container and optionally allows you
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to tail the logs. For single-process (non-SSH) containers, this is a great
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way to watch the output of the process. An example is shown below:
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<pre class="prettyprint">
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$ vagrant docker-logs web
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Server listening on port 3000...
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GET / 200 62.4ms
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GET /images/header.png 200 3.1ms
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GET /images/footer.png 200 2.8ms
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</pre>
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`docker-run` allows you to execute one-off commands in new containers.
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Along with synced folders, this is useful for some environments. For example,
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if you wanted to run tests in a Rails environment, it might look like the
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following:
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<pre class="prettyprint">
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$ vagrant docker-run web -- rake test:unit
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...
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</pre>
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### Next
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The Docker provider allows Vagrant to manage development environments
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with Docker-managed Linux containers. This lets users of Vagrant use this
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style of development where it makes sense, without sacrificing the workflow
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of any other development environments.
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We're now nearing the release of Vagrant 1.6! The feature previews are just
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about over and we're excited to gear up for a release shortly.
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