Exercise 1.6 - Templates

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Ansible uses Jinja2 templating to modify files before they are distributed to managed hosts. Jinja2 is one of the most used template engines for Python (http://jinja.pocoo.org/).

Step 6.1 - Using Templates in Playbooks

When a template for a file has been created, it can be deployed to the managed hosts using the template module, which supports the transfer of a local file from the control node to the managed hosts.

As an example of using templates you will change the motd file to contain host-specific data.

First in the ~/ansible-files/ directory create the template file motd-facts.j2:

Welcome to {{ ansible_hostname }}.
{{ ansible_distribution }} {{ ansible_distribution_version}}
deployed on {{ ansible_architecture }} architecture.

The template file contains the basic text that will later be copied over. It also contains variables which will be replaced on the target machines individually.

Next we need a playbook to use this template. In the ~/ansible-files/ directory create the Playbook motd-facts.yml:

---
- name: Fill motd file with host data
  hosts: node1
  become: yes
  tasks:
    - template:
        src: motd-facts.j2
        dest: /etc/motd
        owner: root
        group: root
        mode: 0644

You have done this a couple of times by now:

• Understand what the Playbook does.

• Execute the Playbook motd-facts.yml.

• Login to node1 via SSH and check the message of the day content.

• Log out of node1.

You should see how Ansible replaces the variables with the facts it discovered from the system.

Step 6.2 - Challenge Lab

Add a line to the template to list the current kernel of the managed node.

• Find a fact that contains the kernel version using the commands you learned in the “Ansible Facts” chapter.

Tip

Do a grep -i for kernel

• Change the template to use the fact you found.

• Run the Playbook again.

• Check motd by logging in to node1

Warning

Solution below!

• Find the fact:

[student<X>@ansible ansible-files]$ ansible node1 -m setup|grep -i kernel
       "ansible_kernel": "3.10.0-693.el7.x86_64",

• Modify the template motd-facts.j2:

Welcome to {{ ansible_hostname }}.
{{ ansible_distribution }} {{ ansible_distribution_version}}
deployed on {{ ansible_architecture }} architecture
running kernel {{ ansible_kernel }}.

• Run the playbook.
• Verify the new message via SSH login to node1.

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