1 - Best practices and first playbook¶

Role webservers-nginx¶

We will name the role to be created as webservers-nginx. To proceed let’s create the minimum required directory structure for the role:

• Create the file webservers-nginx/tasks/main.yml

  (.venv) ~/ansible_1 $ mkdir -p roles/webservers-nginx/tasks/
  (.venv) ~/ansible_1 $ touch roles/webservers-nginx/tasks/main.yml
  

• Include the following content in the file main.yml (careful with the spaces: YAML is very sensitive with this)

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  --- - name: install the nginx reverse proxy apt: name: nginx update_cache: yes - name: enable nginx service systemd: name: nginx state: started enabled: yes

  Warning

  Do not use tabs as YAML doesn’t support them (see here).

In this example we’re just installing the popular webserver nginx, starting it, and enabling the service at boot time (so if we reboot the destination host, this service will be auto-started).

Creating a virtual machine using Vagrant¶

With Vagrant we can spin up virtual machines easily. In this case we will spin up a particular Ubuntu Xenial image. See below:

• Initialize vagrant with an ubuntu image:

  (.venv) ~/ansible_1 $ vagrant init bento/ubuntu-16.04 --minimal
  

  Note

  This will create the file ‘Vagrantfile’.

• Open the auto-generated Vagrantfile, and make sure the content looks like this:

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  Vagrant.configure("2") do |config| config.vm.box = "bento/ubuntu-16.04" config.vm.network "private_network", ip: "10.100.0.2" config.vm.hostname = "tutorial-1" end

• Start the virtual machine

  (.venv) ~/ansible_1 $ vagrant up
  

  Note

  Time to get a cup of tea while this is done.

The steps above will help to create a local virtual machine that we can use to run our Ansible playbook against. This helps in the way that you don’t (and shouldn’t) need to target your important infrastructure to test a particular playbook (careful with this!).

Because Vagrant is using VirtualBox as a default virtualizer, if you open the virtual box user interface you should see the machine we just created running.

The Vagrant box we just installed can be found here. This image by default has the following ssh credentials:

• Username: vagrant
• Password: vagrant (normally)

Simple inventory file¶

The playbook we are going to create needs an inventory file, therefore we will create simple one for now (this will be covered better in the next chapter).

• Create the inventor file:

  (.venv) ~/ansible_1 $ touch inventory.ini
  

• Include the following content in the file:

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  [nginx_webservers] 10.100.0.2 [all:vars] ansible_connection=ssh ansible_user=vagrant ansible_ssh_private_key_file=.vagrant/machines/default/virtualbox/private_key ansible_ssh_common_args='-o StrictHostKeyChecking=no'

After we have the inventory file, and the infrastructure ready, we are ready to create our first playbook.

• Create the file webservers.yml:

  (.venv) ~/ansible_1 $ touch webservers.yml
  

• Include the following content in the file:

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  --- - hosts: nginx_webservers become: true roles: - webservers-nginx

• Test the connectivity to the local VM using this ad-hoc command:

  (.venv) ~/ansible_1 $ ansible -i inventory.ini -m ping all
  

  Output:

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  10.100.0.2 | SUCCESS => { "changed": false, "ping": "pong" }

• Run the playbook:

  (.venv) ~/ansible_1 $ ansible-playbook -i inventory.ini webservers.yml
  

  Output:

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  PLAY [nginx_webservers] ************************************************************************************************************************************************ TASK [Gathering Facts] ************************************************************************************************************************************************* ok: [10.100.0.2] TASK [webservers-nginx : install the nginx reverse proxy] ************************************************************************************************************** changed: [10.100.0.2] TASK [webservers-nginx : enable nginx service] ************************************************************************************************************************* ok: [10.100.0.2] PLAY RECAP ************************************************************************************************************************************************************* 10.100.0.2 : ok=3 changed=1 unreachable=0 failed=0

• From the following output we can conclude that:

  • The only task that changed our infrastructure was the installation of nginx
  • The installed version of Nginx is enabled by default, therefore Ansible didn’t have to enable the service
  • In summary: only 1 item was changed

• If the playbook is ran repeatedly, the state on the remote server should be the same (this is called idempotence).

  (.venv) ~/ansible_1 $ ansible-playbook -i inventory.ini webservers.yml
  

  Output:

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  PLAY [nginx_webservers] ************************************************************************************************************************************************ TASK [Gathering Facts] ************************************************************************************************************************************************* ok: [10.100.0.2] TASK [webservers-nginx : install the nginx reverse proxy] ************************************************************************************************************** ok: [10.100.0.2] TASK [webservers-nginx : enable nginx service] ************************************************************************************************************************* ok: [10.100.0.2] PLAY RECAP ************************************************************************************************************************************************************* 10.100.0.2 : ok=3 changed=0 unreachable=0 failed=0

To confirm everything has worked fine, if you access http://10.100.0.2 this should display the popular Nginx default welcome page: