Interview › Infrastructure as Code (Terraform, Ansible)
What are Ansible modules, and why prefer them over shell commands?
Infrastructure as Code (Terraform, Ansible) · Intermediate level
Answer
Ansible modules are reusable units that implement desired-state logic for a target system. I prefer modules over shell because modules understand idempotency, check mode, return values, errors, and platform differences better than hand-written commands.
Technical explanation
Modules return structured JSON results that can be registered and tested.
Modules support check mode and diff mode more reliably than shell.
Purpose-built modules reduce quoting, parsing, and platform portability problems.
Prefer idempotent modules over shell so repeated runs are safe and change reporting is meaningful.
Separate reusable role logic from inventory-specific variables so the same automation works across environments.
Run lint, syntax checks, check mode where useful, and staged rollouts before production-wide changes.
Hands-on example
1. Make a task idempotent for: What are Ansible modules, and why prefer them over shell commands?
2. Replace an unsafe command with a module where possible:
- name: Install nginx idempotently
ansible.builtin.package:
name: nginx
state: present
3. If command is unavoidable, add guards:
- name: Initialize application database once
ansible.builtin.command: /opt/app/bin/init-db
args:
creates: /var/lib/app/.db_initialized
register: init_result
changed_when: init_result.rc == 0
4. Run the playbook twice; the second run should report ok rather than changed for already-converged tasks.
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