Using Ansible with Vagrant to create a Docker host

Ansible (https://www.ansible.com/) is a very simple and powerful open source automation tool. While using and creating Ansible playbooks is off-topic for this book, we'll use a very simple playbook to install and configure Docker on a CentOS 7 box. Starting from here, you'll be able to iterate through more complex Ansible playbooks.

Getting ready

To step through this recipe, you will need the following:

• A working Vagrant installation
• A working hypervisor
• A working Ansible installation on your machine (an easy way is to $ pip install ansible or to pick your usual package manager like APT or YUM/DNF)
• An Internet connection

How to do it…

Because writing complex Ansible playbooks is out of the scope of this book, we'll use a very simple one, so you can learn more about Ansible later and still reuse this recipe.

A simple Ansible Docker playbook for Vagrant

Our playbook file (playbook.yml) is a plain YAML file, and we'll do the following in this order:

1. Install EPEL.
2. Create a Docker Unix group.
3. Add the default Vagrant user to the new Docker group.
4. Install Docker from CentOS repositories.
5. Enable and start Docker Engine.

Here's how the playbook.yml file looks:

---
- hosts: all
  become: yes
  tasks:
    - name: Enable EPEL
      yum: name=epel-release state=present
    - name: Create a Docker group
      group: name=docker state=present
    - name: Add the vagrant user to Docker group
      user: name=vagrant groups=docker append=yes
    - name: Install Docker
      yum: name=docker state=present
    - name: Enable and Start Docker Daemon
      service: name=docker state=started enabled=yes

Apply Ansible from Vagrant

To use our Ansible playbook, let's start with a simple Vagrantfile starting a CentOS 7 box:

Vagrant.configure("2") do |config|
  config.vm.box = "bento/centos-7.2"
  config.vm.define "srv-1" do |config|
    config.vm.hostname = "srv-1"
    config.vm.network "private_network", type: "dhcp"
  end
end

Simply add Ansible provisioning like this to the VM definition so it will load and apply your playbook.yml file:

    config.vm.provision "ansible" do |ansible|
      ansible.playbook = "playbook.yml"
    end

You can now run vagrant up and use CentOS 7 Docker Engine version right away:

$ vagrant ssh
[vagrant@srv-1 ~]$ systemctl status docker
[vagrant@srv-1 ~]$ docker --version
Docker version 1.10.3, build d381c64-unsupported
[vagrant@srv-1 ~]$ docker run -it --rm alpine /bin/hostname
0f44a4d7afcd

There's more…

What if for some reason you don't or can't have Ansible installed on your host machine? Alternatively, maybe you need a specific Ansible version on your Vagrant box to mimic production and you don't want to mess with your local Ansible installation. There's an interesting variant Ansible provider you can use: it will either use Ansible directly from the guest VM, and if it's not installed, it will install it from official repositories or PIP. You can use this very simple default configuration:

    config.vm.provision "ansible_local" do |ansible|
      ansible.playbook = "playbook.yml"
    end

You can also use the following command:

$ vagrant up
[…]
==> srv-1: Running provisioner: ansible_local...
    srv-1: Installing Ansible...
    srv-1: Running ansible-playbook...
[…]

Log in to the box via SSH and check that Ansible is locally installed with the latest version:

$ vagrant ssh
$ ansible --version
ansible 2.1.1.0

If your use case is different, you can use more precise deployment options, to be able to fix an Ansible version number using PIP (here, version 1.9.6 instead of the latest 2.x series):

Note

It will take noticeably longer to start, as it needs to install many packages on the guest system.

    config.vm.provision "ansible_local" do |ansible|
      ansible.version = "1.9.6"
      ansible.install_mode = :pip
      ansible.playbook = "playbook.yml"
    end

You can also use the following command:

$ vagrant up
[…]
==> srv-1: Running provisioner: ansible_local...
    srv-1: Installing Ansible...
    srv-1: Installing pip... (for Ansible installation)
    srv-1: Running ansible-playbook...

Inside the Vagrant guest, you can now check for the PIP and Ansible versions:

$ pip --version
pip 8.1.2 from /usr/lib/python2.7/site-packages (python 2.7)
$ ansible --version
ansible 1.9.6

You can also check if our playbook has been installed correctly with the old 1.x Ansible version:

$ docker version

Also check if Docker is installed, and verify now it's working as the Vagrant user:

$ docker run -it --rm alpine ping -c2 google.com
PING google.com (216.58.211.78): 56 data bytes
64 bytes from 216.58.211.78: seq=0 ttl=61 time=22.078 ms
64 bytes from 216.58.211.78: seq=1 ttl=61 time=21.061 ms