Ansible Skill

Expert guidance for Ansible playbooks, roles, and automation best practices.

Playbook Structure

Basic Playbook

---
- name: Configure web servers
  hosts: webservers
  become: true
  vars:
    http_port: 80

  tasks:
    - name: Install nginx
      ansible.builtin.apt:
        name: nginx
        state: present
        update_cache: true

    - name: Start nginx service
      ansible.builtin.service:
        name: nginx
        state: started
        enabled: true

Multiple Plays

---
- name: Configure database servers
  hosts: databases
  tasks:
    - name: Install PostgreSQL
      ansible.builtin.apt:
        name: postgresql
        state: present

- name: Configure web servers
  hosts: webservers
  tasks:
    - name: Install nginx
      ansible.builtin.apt:
        name: nginx
        state: present

Idempotency (CRITICAL)

Idempotent tasks can run multiple times without changing the result after the first run.

✅ Idempotent Examples

# Good - using built-in modules (always idempotent)
- name: Ensure nginx is installed
  ansible.builtin.apt:
    name: nginx
    state: present

- name: Ensure config file has correct content
  ansible.builtin.copy:
    src: nginx.conf
    dest: /etc/nginx/nginx.conf
    owner: root
    mode: '0644'

❌ Non-Idempotent Antipatterns

# BAD - runs every time, always reports "changed"
- name: Configure system
  ansible.builtin.shell: echo "config" >> /etc/app.conf

# GOOD - idempotent alternative
- name: Ensure config line exists
  ansible.builtin.lineinfile:
    path: /etc/app.conf
    line: "config"
    create: true

Making Shell/Command Idempotent

# Use changed_when and creates/removes
- name: Download file
  ansible.builtin.shell: |
    curl -o /tmp/file.tar.gz https://example.com/file.tar.gz
  args:
    creates: /tmp/file.tar.gz
  changed_when: false

# Or check conditions first
- name: Check if configured
  ansible.builtin.stat:
    path: /etc/app/.configured
  register: configured

- name: Run configuration script
  ansible.builtin.shell: /opt/app/configure.sh
  when: not configured.stat.exists

- name: Mark as configured
  ansible.builtin.file:
    path: /etc/app/.configured
    state: touch
  when: not configured.stat.exists

Variables & Jinja2 Templating

Variable Precedence (low to high)

1. Role defaults (roles/*/defaults/main.yml)
2. Inventory vars
3. Playbook vars
4. Extra vars (-e / --extra-vars)

Using Variables

---
- name: Deploy application
  hosts: app_servers
  vars:
    app_version: "1.2.3"
    app_user: "appuser"

  tasks:
    - name: Download application version {{ app_version }}
      ansible.builtin.get_url:
        url: "https://releases.example.com/app-{{ app_version }}.tar.gz"
        dest: "/opt/app-{{ app_version }}.tar.gz"
        owner: "{{ app_user }}"

Facts

# Gather facts automatically (default: true)
- name: Show system facts
  hosts: all
  tasks:
    - name: Display OS family
      ansible.builtin.debug:
        msg: "OS family is {{ ansible_os_family }}"

    - name: Display IP address
      ansible.builtin.debug:
        msg: "IP is {{ ansible_default_ipv4.address }}"

Conditionals

- name: Install package on Debian-based systems
  ansible.builtin.apt:
    name: nginx
    state: present
  when: ansible_os_family == "Debian"

- name: Install package on RedHat-based systems
  ansible.builtin.yum:
    name: nginx
    state: present
  when: ansible_os_family == "RedHat"

Handlers

Handlers run once at the end of a play, after all tasks.

---
- name: Configure web server
  hosts: webservers
  tasks:
    - name: Copy nginx config
      ansible.builtin.copy:
        src: nginx.conf
        dest: /etc/nginx/nginx.conf
      notify: Restart nginx

    - name: Copy site config
      ansible.builtin.template:
        src: site.conf.j2
        dest: /etc/nginx/sites-available/mysite
      notify: Restart nginx

  handlers:
    - name: Restart nginx
      ansible.builtin.service:
        name: nginx
        state: restarted

Key points:

• Handlers only run if notified
• Handlers run once, even if notified multiple times
• Handlers run at the end of the play
• Use meta: flush_handlers to run handlers immediately

Loops

Modern Loop Syntax (Ansible 2.5+)

# Preferred
- name: Install packages
  ansible.builtin.apt:
    name: "{{ item }}"
    state: present
  loop:
    - nginx
    - postgresql
    - redis

# With dictionary
- name: Create users
  ansible.builtin.user:
    name: "{{ item.name }}"
    groups: "{{ item.groups }}"
  loop:
    - { name: 'alice', groups: 'admin' }
    - { name: 'bob', groups: 'users' }

Legacy Loop Syntax (avoid)

# OLD - avoid in new playbooks
- name: Install packages
  ansible.builtin.apt:
    name: "{{ item }}"
    state: present
  with_items:
    - nginx
    - postgresql

Roles

Role Structure

roles/
└── webserver/
    ├── tasks/
    │   └── main.yml          # Main task list
    ├── handlers/
    │   └── main.yml          # Handlers
    ├── templates/
    │   └── nginx.conf.j2     # Jinja2 templates
    ├── files/
    │   └── index.html        # Static files
    ├── vars/
    │   └── main.yml          # Variables
    ├── defaults/
    │   └── main.yml          # Default variables
    ├── meta/
    │   └── main.yml          # Role metadata/dependencies
    └── README.md

Using Roles

---
- name: Configure servers
  hosts: webservers
  roles:
    - common
    - webserver
    - monitoring

# Or with parameters
- name: Configure servers
  hosts: webservers
  roles:
    - role: webserver
      vars:
        http_port: 8080

Role Dependencies

# roles/webserver/meta/main.yml
---
dependencies:
  - role: common
  - role: firewall
    vars:
      firewall_allowed_ports:
        - 80
        - 443

Security Best Practices

Ansible Vault (CRITICAL)

Never commit unencrypted secrets!

# Encrypt a file
ansible-vault encrypt secrets.yml

# Edit encrypted file
ansible-vault edit secrets.yml

# Run playbook with vault password
ansible-playbook site.yml --ask-vault-pass
# Or use password file
ansible-playbook site.yml --vault-password-file ~/.vault_pass

Encrypted variables:

# vars/secrets.yml (encrypted with ansible-vault)
---
db_password: !vault |
          $ANSIBLE_VAULT;1.1;AES256
          66386439653361336136343...
api_key: !vault |
          $ANSIBLE_VAULT;1.1;AES256
          35323264353938643261623...

Privilege Escalation

Use become carefully:

# Entire play
- name: Configure system
  hosts: servers
  become: true  # Run all tasks as root
  tasks:
    - name: Install package
      ansible.builtin.apt:
        name: nginx

# Specific task
- name: Configure system
  hosts: servers
  tasks:
    - name: Install package (requires root)
      ansible.builtin.apt:
        name: nginx
      become: true

    - name: Copy user file (no root needed)
      ansible.builtin.copy:
        src: .bashrc
        dest: ~/.bashrc

Become user:

- name: Run as specific user
  ansible.builtin.command: whoami
  become: true
  become_user: appuser

Hiding Sensitive Output

# Don't log sensitive data
- name: Set database password
  ansible.builtin.shell: |
    psql -c "ALTER USER postgres PASSWORD '{{ db_password }}'"
  no_log: true

# Register without logging
- name: Get API token
  ansible.builtin.uri:
    url: https://api.example.com/token
    method: POST
  register: token_response
  no_log: true

Inventory Security

# Don't commit passwords in inventory
# BAD
[databases]
db1 ansible_host=10.0.1.10 ansible_user=admin ansible_password=secret123

# GOOD - use vault for passwords
[databases]
db1 ansible_host=10.0.1.10 ansible_user=admin

# In encrypted group_vars/databases.yml
ansible_password: !vault |
          $ANSIBLE_VAULT;1.1;AES256
          ...

Module Best Practices

Prefer Specific Modules Over shell/command

# BAD - using shell when module exists
- name: Install package
  ansible.builtin.shell: apt-get install -y nginx

# GOOD - using built-in module
- name: Install package
  ansible.builtin.apt:
    name: nginx
    state: present

# BAD - using shell for file operations
- name: Create directory
  ansible.builtin.shell: mkdir -p /opt/app

# GOOD - using file module
- name: Create directory
  ansible.builtin.file:
    path: /opt/app
    state: directory
    mode: '0755'

Fully Qualified Collection Names (Ansible 2.10+)

# GOOD - explicit collection
- name: Install package
  ansible.builtin.apt:
    name: nginx

# Also acceptable for clarity
- name: Manage Docker container
  community.docker.docker_container:
    name: myapp
    image: nginx:latest

Common Pitfalls

1. Not Using check_mode

# Always test with --check first
# ansible-playbook site.yml --check

- name: Dangerous operation
  ansible.builtin.file:
    path: /etc/important-config
    state: absent
  # Test with --check before running!

2. Ignoring Return Codes

# BAD - ignores failures
- name: Run script
  ansible.builtin.shell: /opt/app/script.sh
  ignore_errors: true

# GOOD - handle failures explicitly
- name: Run script
  ansible.builtin.shell: /opt/app/script.sh
  register: script_result
  failed_when: script_result.rc != 0 and script_result.rc != 2

3. Not Handling "changed" Status

# BAD - always reports changed
- name: Check status
  ansible.builtin.shell: systemctl status nginx

# GOOD - mark as not changed
- name: Check status
  ansible.builtin.shell: systemctl status nginx
  changed_when: false
  check_mode: false

4. Using shell when command suffices

# BAD - unnecessary shell features
- name: List files
  ansible.builtin.shell: ls /tmp

# GOOD - use command (safer, no shell injection)
- name: List files
  ansible.builtin.command: ls /tmp
  changed_when: false

Ansible Lint

Common Rules

yaml[line-length] - Keep lines under 160 characters name[missing] - All tasks must have names fqcn[action-core] - Use fully qualified collection names no-changed-when - shell/command should have changed_when risky-shell-pipe - Avoid pipes in shell commands

Configuration

# .ansible-lint
---
skip_list:
  - yaml[line-length]  # Skip if you have long lines

warn_list:
  - experimental  # Warn on experimental features

exclude_paths:
  - .cache/
  - test/

Naming Conventions

# GOOD - descriptive names in imperative mood
- name: Ensure nginx is installed
- name: Copy nginx configuration
- name: Restart nginx service

# BAD - vague or missing names
- name: nginx
- name: Task 1
- apt: name=nginx  # Missing name entirely

Tags for Selective Execution

---
- name: Configure system
  hosts: all
  tasks:
    - name: Install packages
      ansible.builtin.apt:
        name: "{{ item }}"
      loop:
        - nginx
        - postgresql
      tags:
        - packages
        - install

    - name: Configure firewall
      ansible.builtin.ufw:
        rule: allow
        port: 80
      tags:
        - firewall
        - security

# Run only specific tags
# ansible-playbook site.yml --tags "packages"
# ansible-playbook site.yml --skip-tags "firewall"

Review Severity Guidelines

• CRITICAL: Unencrypted secrets in files, using shell with user input, privilege escalation without justification
• MAJOR: Non-idempotent tasks, using shell/command when module exists, missing no_log on sensitive tasks, not using ansible-vault
• MINOR: Missing task names, not using FQCN, missing changed_when on commands, using legacy with_items
• SUGGESTION: Could use tags for organization, could extract to role, could use handlers instead of multiple restarts

References

• Ansible Documentation
• Ansible Best Practices
• Ansible Lint
• Ansible Vault