Ansible.md

📜 Ansible Cheatsheet

🔹 Introduction to Ansible

✅ What is Ansible?

Ansible is an open-source automation tool used for:
✅ Configuration Management (e.g., installing & managing software on servers)
✅ Application Deployment (e.g., deploying a web app on multiple servers)
✅ Orchestration (e.g., managing multi-tier applications like load balancer + DB)
✅ Provisioning (e.g., setting up cloud infrastructure with AWS, Azure, GCP)

✅ Why Use Ansible?

🔹 Agentless: No need to install agents on target machines (uses SSH & WinRM)
🔹 Idempotent: Runs multiple times without unwanted changes
🔹 Human-Readable: Uses YAML playbooks
🔹 Cross-Platform: Works on Linux, Windows, macOS, Cloud Servers

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🛠️ 1. Installing & Setting Up Ansible

✅ Installing Ansible on Linux

# Ubuntu/Debian
sudo apt update
sudo apt install -y ansible

# CentOS/RHEL
sudo yum install -y ansible

✅ Checking Installation

ansible --version

✅ Setting Up an Inventory File

An inventory file (/etc/ansible/hosts) tells Ansible where to connect.
Example:

[webservers]
server1 ansible_host=192.168.1.10 ansible_user=ubuntu
server2 ansible_host=192.168.1.11 ansible_user=ubuntu

[dbservers]
db1 ansible_host=192.168.1.20 ansible_user=root

✅ Testing Connectivity with ping

ansible all -m ping

📌 If successful, you'll see:

server1 | SUCCESS => {"changed": false, "ping": "pong"}
server2 | SUCCESS => {"changed": false, "ping": "pong"}

---

🚀 2. Running Ad-Hoc Commands (Quick Tasks Without a Playbook)

✅ Check disk usage

ansible all -m command -a "df -h"

✅ Check system uptime

ansible all -m command -a "uptime"

✅ Create a directory on remote hosts

ansible all -m file -a "path=/opt/newdir state=directory"

✅ Copy files to remote servers

ansible all -m copy -a "src=/tmp/file.txt dest=/home/ubuntu/file.txt"

✅ Install a package (e.g., nginx) on all web servers

ansible webservers -m apt -a "name=nginx state=present" --become

✅ Restart a service (e.g., nginx)

ansible webservers -m service -a "name=nginx state=restarted" --become

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📜 3. Writing Ansible Playbooks (Automation Scripts)

✅ What is a Playbook?
A playbook is a YAML file that contains tasks to automate configuration.

🔹 Basic Playbook Example

- name: Install and Start Nginx
  hosts: webservers
  become: yes  # Run as sudo
  tasks:
    - name: Install Nginx
      apt:
        name: nginx
        state: present

    - name: Start Nginx
      service:
        name: nginx
        state: started

✅ Run the Playbook

ansible-playbook playbook.yml

---

🔹 4. Using Variables in Ansible

✅ Define Variables in a Playbook

- name: Install a Package with a Variable
  hosts: webservers
  vars:
    package_name: nginx
  tasks:
    - name: Install Package
      apt:
        name: "{{ package_name }}"
        state: present

✅ Use Built-in Ansible Facts

ansible all -m setup

Example Fact Usage in Playbook:

- name: Display System Information
  hosts: all
  tasks:
    - debug:
        msg: "This server is running {{ ansible_distribution }} {{ ansible_distribution_version }}"

---

🔹 5. Loops & Conditionals

✅ Loop Example (Install Multiple Packages)

- name: Install Multiple Packages
  hosts: webservers
  become: yes
  tasks:
    - name: Install Packages
      apt:
        name: "{{ item }}"
        state: present
      loop:
        - nginx
        - curl
        - unzip

✅ Conditional Execution

- name: Restart Nginx Only If Needed
  hosts: webservers
  become: yes
  tasks:
    - name: Check if Nginx is Running
      shell: pgrep nginx
      register: nginx_running
      ignore_errors: yes

    - name: Restart Nginx
      service:
        name: nginx
        state: restarted
      when: nginx_running.rc == 0

---

📂 6. Ansible Roles (Best Practices for Large Projects)

✅ Generate an Ansible Role Structure

ansible-galaxy init my_role

📌 This creates a structured directory like:

my_role/
├── tasks/
│   └── main.yml
├── handlers/
│   └── main.yml
├── templates/
├── files/
├── vars/
│   └── main.yml
├── defaults/
│   └── main.yml
├── meta/
│   └── main.yml
├── README.md

✅ Use Roles in a Playbook

- name: Deploy Web Server
  hosts: webservers
  roles:
    - nginx_role

---

🔐 7. Ansible Vault (Encrypting Secrets)

✅ Create an Encrypted File

ansible-vault create secrets.yml

✅ Edit an Encrypted File

ansible-vault edit secrets.yml

✅ Use Vault in Playbooks

- name: Deploy with Encrypted Secrets
  hosts: webservers
  vars_files:
    - secrets.yml
  tasks:
    - debug:
        msg: "The secret password is {{ secret_password }}"

✅ Run Playbook with Vault Password Prompt

ansible-playbook playbook.yml --ask-vault-pass

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🎯 8. Useful Ansible Commands

✅ Check Playbook Syntax

ansible-playbook playbook.yml --syntax-check

✅ Dry Run (Test Without Executing Changes)

ansible-playbook playbook.yml --check

✅ List All Available Modules

ansible-doc -l

✅ Get Help for a Specific Module

ansible-doc apt

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🎯 Conclusion

This Ansible Cheatsheet provides a step-by-step guide from beginner to advanced.

🚀 Next Steps:
✅ Practice with real-world playbooks
✅ Use roles for better structuring
✅ Secure credentials with Ansible Vault
✅ Automate cloud infrastructure with Terraform + Ansible

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