Ansible Level 04 Day 05: Using Ansible Conditionals¶

This document outlines the solution for Ansible Level 04 Day 05. The objective was to create a single Ansible playbook that runs on all hosts but performs different file copy operations depending on the specific server's node name by leveraging the when conditional statement.

Table of Contents¶

Task Overview
Step-by-Step Solution
Deep Dive: Ansible Concepts Used
- The when Conditional
- Ansible Facts (ansible_nodename)

Task Overview¶

Objective: Distribute specific files to specific App Servers using a single playbook targeting all hosts.

Requirements: 1. Playbook: Create /home/thor/ansible/playbook.yml. 2. Target: The play must use - hosts: all. 3. Logic (using when condition and ansible_nodename): * If node is App Server 1: Copy /usr/src/finance/blog.txt to /opt/finance/blog.txt. Owner: tony, Permissions: 0744. * If node is App Server 2: Copy /usr/src/finance/story.txt to /opt/finance/story.txt. Owner: steve, Permissions: 0744. * If node is App Server 3: Copy /usr/src/finance/media.txt to /opt/finance/media.txt. Owner: banner, Permissions: 0744. 4. Constraint: Must run cleanly using ansible-playbook -i inventory playbook.yml.

Step-by-Step Solution¶

1. Verify the Environment¶

Before creating the playbook, verify the pre-existing inventory file to ensure we can connect to all target servers.

Command:

cd /home/thor/ansible
cat inventory

2. Create the Playbook¶

Create the playbook using the copy module combined with the when conditional. We must use become: yes because writing to /opt/finance/ and changing file ownership requires elevated root privileges.

Note: In the Nautilus Datacenter environment, the ansible_nodename fact typically returns the fully qualified domain name (FQDN) like stapp01.stratos.xfusioncorp.com.

Command:

vi playbook.yml

Content:

---
- name: Copy files using conditionals
  hosts: all
  become: yes
  tasks:
    - name: Show the nodename for debugging (Optional)
      debug:
        msg: "Nodename is: {{ ansible_nodename }}"

    - name: Copy blog.txt to App Server 1
      copy:
        src: /usr/src/finance/blog.txt
        dest: /opt/finance/blog.txt
        owner: tony
        group: tony
        mode: '0744'
      when: ansible_nodename == 'stapp01.stratos.xfusioncorp.com' or ansible_nodename == 'stapp01'

    - name: Copy story.txt to App Server 2
      copy:
        src: /usr/src/finance/story.txt
        dest: /opt/finance/story.txt
        owner: steve
        group: steve
        mode: '0744'
      when: ansible_nodename == 'stapp02.stratos.xfusioncorp.com' or ansible_nodename == 'stapp02'

    - name: Copy media.txt to App Server 3
      copy:
        src: /usr/src/finance/media.txt
        dest: /opt/finance/media.txt
        owner: banner
        group: banner
        mode: '0744'
      when: ansible_nodename == 'stapp03.stratos.xfusioncorp.com' or ansible_nodename == 'stapp03'

3. Execute and Validate¶

Run the playbook against the inventory.

Execution Command:

ansible-playbook -i inventory playbook.yml

Expected Output: The output will clearly show the conditional logic in action. You will see tasks being executed on the matching host and skipped on the others:

PLAY [Copy files using conditionals] ************************************************

TASK [Gathering Facts] **************************************************************
ok: [stapp01]
ok: [stapp02]
ok: [stapp03]

TASK [Copy blog.txt to App Server 1] ************************************************
changed: [stapp01]
skipping: [stapp02]
skipping: [stapp03]

TASK [Copy story.txt to App Server 2] ***********************************************
skipping: [stapp01]
changed: [stapp02]
skipping: [stapp03]

TASK [Copy media.txt to App Server 3] ***********************************************
skipping: [stapp01]
skipping: [stapp02]
changed: [stapp03]
...

Manual Verification (Optional): To independently verify the content and permissions on the remote servers, use ad-hoc commands:

ansible stapp01 -i inventory -m command -a "ls -l /opt/finance/blog.txt" --become
ansible stapp02 -i inventory -m command -a "ls -l /opt/finance/story.txt" --become
ansible stapp03 -i inventory -m command -a "ls -l /opt/finance/media.txt" --become

Deep Dive: Ansible Concepts Used¶

The `when` Conditional¶

The when statement is Ansible's version of an if statement. It evaluates a Jinja2 expression before executing a task. If the expression is true, the task runs. If false, the task is skipped. * Syntax: when: variable == "value" * Context: You do not need {{ }} brackets inside a when clause because it is already evaluated as an implicit Jinja2 context.

Ansible Facts (`ansible_nodename`)¶

When Ansible runs (specifically during the implicit Gathering Facts task at the start of a play), it collects a massive dictionary of data about the remote system. * ansible_hostname: Usually just the short hostname (e.g., stapp01). * ansible_nodename or ansible_fqdn: Often the fully qualified domain name (FQDN) assigned to the system (e.g., stapp01.stratos.xfusioncorp.com). * Why use it? It allows us to define a single play targeting all servers, but selectively execute tasks on specific machines without writing multiple separate plays in the playbook.