shell-to-ansible

Shell-to-Ansible Conversion Skill

Convert procedural shell scripts into declarative, idempotent Ansible playbooks following Red Hat Communities of Practice standards.

Mindset Shift: Procedural vs. Declarative

Shell Scripts (Procedural)

• How to do it: Step-by-step instructions
• Imperative: "Install package, then configure it, then start service"
• State unaware: Runs all commands every time
• Error-prone: Partial failures leave inconsistent state

Ansible (Declarative)

• What should exist: Desired end state
• Declarative: "Package should be installed, configured correctly, service running"
• State aware: Only makes necessary changes
• Idempotent: Safe to run repeatedly

Conversion Process

Step 1: Analyze the Shell Script

Identify what the script accomplishes:

1. Packages to install
2. Files to create/modify
3. Services to manage
4. Users/groups to create
5. Permissions to set
6. Conditional logic
7. Loops and iterations

Step 2: Map to Ansible Modules

Replace shell commands with appropriate Ansible modules (see Module Mapping reference).

Step 3: Make it Idempotent

Ensure the playbook can run multiple times safely:

• Use declarative modules (package, service, file)
• Add creates/removes to commands
• Use changed_when: false for checks
• Leverage fact-based guards

Step 4: Add Error Handling

Replace || exit 1 with proper Ansible error handling:

• failed_when conditions
• ignore_errors where appropriate
• Assertions for validation

Step 5: Organize into Roles

For complex scripts, organize into proper role structure following Red Hat CoP.

Module Mapping

Package Management

# Shell
yum install -y httpd
apt-get install -y apache2

# Ansible
- name: Install Apache
  ansible.builtin.package:
    name: "{{ __rolename_package_name }}"
    state: present

# Shell
yum update -y
apt-get update && apt-get upgrade -y

# Ansible
- name: Update all packages
  ansible.builtin.package:
    name: '*'
    state: latest
  when: rolename_update_all_packages | default(false) | bool