Run Docker container on Vagrant

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Post summary: How to run Docker container on Vagrant.

Code bellow can be found in GitHub sample-dropwizard-rest-stub repository in Vagrantfile-docker file. Since Vagrant requires to have only one Vagrantfile if you want to run this example you have to rename Vagrantfile-docker to Vagrantfile then run Vagrant commands described in the end of this post. This post is part of Vagrant series. All of other Vagrant related posts as well as more theoretical information what is Vagrant and why to use it can be found in What is Vagrant and why to use it post.

Vagrantfile

As described in Vagrant introduction post all configurations are done in a single text file called Vagrantfile. Bellow is a Vagrant file which can be used to deploy and start Docker container on Vagrant. Example here uses Dockerised application that is described in Run Dropwizard application in Docker with templated configuration using environment variables post.

Vagrant.configure('2') do |config|

  config.vm.hostname = 'dropwizard'
  config.vm.box = 'opscode-centos-7.2'
  config.vm.box_url = 'http://opscode-vm-bento.s3.amazonaws.com/vagrant/virtualbox/opscode_centos-7.2_chef-provisionerless.box'

  config.vm.synced_folder './', '/vagrant'

  config.vm.network :forwarded_port, guest: 9000, host: 9000
  config.vm.network :forwarded_port, guest: 9001, host: 9001

  config.vm.provider :virtualbox do |vb|
    vb.name = 'dropwizard-rest-stub-docker'
    vb.customize ['modifyvm', :id, '--memory', '768', '--cpus', '2']
  end

  config.vm.provision :shell do |shell|
    shell.inline = <<-SHELL
      sudo yum -y install epel-release
      sudo yum -y install python-pip
      sudo pip install --upgrade pip
      sudo pip install six==1.4
      sudo pip install docker-py
    SHELL
  end

  config.vm.provision :docker do |docker|
    docker.build_image '/vagrant/.', args: '-t dropwizard-rest-stub'
    docker.run 'dropwizard-rest-stub', args: '-it -p 9000:9000 -p 9001:9001 -e ENV_VARIABLE_VERSION=1.1.1'
  end

end

Vagrantfile explanation

File starts with a Vagrant.configure(‘2’) do |config| which states that version 2 of Vagrant API will be used and defines constant with name config to be used bellow. Guest operating system hostname is set with config.vm.hostname. If you use vagrant-hostsupdater plugin it will add it to your hosts file and you can access it from browser in case you are developing web applications. With config.vm.box you define which would be the guest operating system. Vagrant maintains config.vm.box = “hashicorp/precise64” which is Ubuntu 12.04 (32 and 64-bit), they also recommend to use Bento’s boxes. I have found issues with Vagrant’s as well as Bento’s boxes so I’ve decided to use one I know is working. I specify where it is located with config.vm.box_url. It is CentOS 7.2. With config.vm.synced_folder command you specify that Vagrantfile location folder is shared as /vagrant/ in guest operating system. This makes it easy to transfer files between guest and host operating systems. This mount is done by default, but it is good to explicitly state it for better readability. With config.vm.network :forwarded_port port from guest OS is forwarded to your hosting OS. Without exposing any port you will not have access to guest OS, only port open by default is 22 for SSH. With config.vm.provider :virtualbox do |vb| you access VirtualBox provider for more configurations, vb.name = ‘dropwizard-rest-stub-docker’ sets the name that you see in Oracle VirtualBox Manager. With vb.customize [‘modifyvm’, :id, ‘–memory’, ‘768’, ‘–cpus’, ‘2’] you modify default hardware settings for the machine, RAM is set to 768MB and 2 CPUs are configured. Finally the provisioning part takes place which is done by shell commands inside config.vm.provision :shell do |shell| block. This block installs Python as well as docker-py. It is CentOS specific as it uses YUM which is CentOS package manager. Next provisioning part is to run docker provisioner that builds docker image and then runs it by mapping ports and setting environment variable. For more details how to build and run Docker containers read Run Dropwizard application in Docker with templated configuration using environment variables post.

Running Vagrant

Command to start Vagrant machine is: vagrant up. Then in order to invoke provisioning section with actual deployment you have to call: vagrant provision. All can be done in one step: vagrant up –provision. To shutdown the machine use vagrant halt. To delete machine: vagrant destroy.

Conclusion

It is very easy to create Vagrantfile that builds and runs Docker container. Once created file can be reused by all team members. It is executed over and over again making provisioning extremely easy.

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Category: Tutorials | Tags: , ,