6-Day3-1-Variables

Lab Exercise: Types of Variables and Their Hierarchy

Objective:

Understand the variable precedence hierarchy in Ansible using group variables, host variables, play variables, task variables, and extra vars in a step-by-step manner.

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Lab 1.1: Group Variables in Inventory

Scenario:

Define group variables in the inventory file and observe how they are resolved.

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Steps:

1. Define Inventory with Group Variables:

   • Create ~/day3/inventory.ini with the following content:

     [web_servers]
     web1 ansible_host=192.168.1.10 ansible_user=ec2-user
     web2 ansible_host=192.168.1.11 ansible_user=ec2-user
     
     [web_servers:vars]
     website_port=8080
     website_content="Content from group variables"

2. Create the Playbook:

   • Save as ~/day3/group_variables.yaml:

     - name: Group Variables Demo
       hosts: web_servers
       tasks:
         - name: Display website_port from group variables
           debug:
             msg: "Website Port: {{ website_port }}"
     
         - name: Display website_content from group variables
           debug:
             msg: "Website Content: {{ website_content }}"

3. Run the Playbook:

   • Execute the playbook:

     ansible-playbook ~/day3/group_variables.yaml -i ~/day3/inventory.ini

4. Expected Output:

   • The values of website_port and website_content are resolved from the group variables in the inventory file.

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Lab 1.2: Host Variables in Inventory

Scenario:

Add host variables to the inventory and observe how they override group variables.

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Steps:

1. Modify the Inventory File:

   • Update inventory.ini to include host-specific variables:

     [web_servers]
     web1 ansible_host=192.168.1.10 ansible_user=ec2-user website_port=9090
     web2 ansible_host=192.168.1.11 ansible_user=ec2-user
     
     [web_servers:vars]
     website_port=8080
     website_content="Content from group variables"

2. Modify the Playbook (optional):

   • Use the same playbook group_variables.yaml from Lab 1.1.

3. Run the Playbook:

   • Execute the playbook and observe the output:

     ansible-playbook ~/day3/group_variables.yaml -i ~/day3/inventory.ini

4. Expected Output:

   • web1 should display website_port=9090 (host variable), while web2 uses website_port=8080 (group variable).

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Lab 1.3: Play and Task Variables

Part A: Using Play Variables

1. Modify the Playbook:

   • Update the playbook to include play variables:

     - name: Play Variables Demo
       hosts: web_servers
       vars:
         website_port: 10010
         website_content: "Content from play variables"
       tasks:
         - name: Display website_port from play variables
           debug:
             msg: "Website Port: {{ website_port }}"
     
         - name: Display website_content from play variables
           debug:
             msg: "Website Content: {{ website_content }}"

2. Run the Playbook:

   • Execute the playbook and observe how play variables override group and host variables:

     ansible-playbook ~/day3/group_variables.yaml -i ~/day3/inventory.ini

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Part B: Using Task Variables

1. Add Task-Level Variables:

   • Update the playbook:

     - name: Task Variables Demo
       hosts: web_servers
       vars:
         website_port: 10010
         website_content: "Content from play variables"
       tasks:
         - name: Override website_content at the task level
           debug:
             msg: "Task-Level Override: Website Content is '{{ website_content }}'"
           vars:
             website_content: "Task-level override content"
     
         - name: Display website_port (play variable remains unchanged)
           debug:
             msg: "Website Port: {{ website_port }}"

2. Run the Playbook:

   • Observe how task variables override play variables for the specific task:

     ansible-playbook ~/day3/group_variables.yaml -i ~/day3/inventory.ini

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Lab 1.4: Extra Vars Precedence

Scenario:

Use extra vars with the -e option to override all other variables.

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Steps:

1. Execute the Playbook with Extra Vars:

   • Use the following command:

     ansible-playbook ~/day3/group_variables.yaml -i ~/day3/inventory.ini \
       --extra-vars "website_port=12345 website_content='Content from extra vars'"

2. Analyze Results:

   • Observe how website_port and website_content are resolved from extra vars, overriding all other variable sources (inventory, group, host, play, and task variables).

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Outcome of Labs:

1. Participants will understand the variable precedence hierarchy:

   • Extra vars (-e) > Task vars > Play vars > Host vars > Group vars > Inventory vars > Default vars.

2. Participants will explore variable resolution dynamically by modifying or adding variables at different levels and observing their behavior.

This step-by-step progression simplifies understanding variable precedence in Ansible.