my-docs/Ansible/3-PlayBook.md

Ansible Playbook Guide

Ansible Playbooks are YAML files that define a series of tasks to automate server configuration, deployment, and management. This guide provides instructions on how to run a playbook and includes examples to help you get started.

Running an Ansible Playbook

To execute an Ansible Playbook, use the following command:

ansible-playbook <playbook.yaml> -i <inventory-file.ini>

• <playbook.yaml>: Path to your playbook file.
• <inventory-file.ini>: Path to your inventory file (can be in INI or YAML format).

Example Playbooks

1. Simple APT Cache Update

This playbook updates the APT package cache on all specified hosts.

- name: Update APT Cache Playbook
  hosts: all           # Run on all hosts defined in the inventory
  become: yes          # Use sudo for elevated privileges
  tasks:
    - name: Update apt-cache
      ansible.builtin.apt:
        update_cache: yes

2. Update APT Cache and Install Nginx

This playbook updates the APT cache and installs the Nginx web server on all specified hosts.

- name: Install Nginx and Update APT Cache
  hosts: all           # Run on all hosts defined in the inventory
  become: yes          # Use sudo for elevated privileges
  tasks:
    - name: Update apt-cache and install Nginx
      ansible.builtin.apt:
        name: nginx
        state: present
        update_cache: yes

3. Install Nginx and Copy Configuration File

This playbook installs Nginx and copies a custom configuration file from the Ansible server to the target hosts.

- name: Install Nginx and Copy Configuration
  hosts: all           # Run on all hosts defined in the inventory
  become: yes          # Use sudo for elevated privileges
  tasks:
    - name: Update apt-cache and install Nginx
      ansible.builtin.apt:
        name: nginx
        state: present
        update_cache: yes
        
    - name: Copy Nginx configuration file
      ansible.builtin.copy:
        src: /root/ansible/nginx.conf
        dest: /etc/nginx/nginx.conf

4. Full Nginx Deployment: Install, Configure, and Restart

This playbook demonstrates a full Nginx deployment: updating the APT cache, installing Nginx, copying a configuration file, and restarting the Nginx service to apply the changes.

- name: Full Nginx Deployment
  hosts: all           # Run on all hosts defined in the inventory
  become: yes          # Use sudo for elevated privileges
  tasks:
    - name: Update apt-cache and install Nginx
      ansible.builtin.apt:
        name: nginx
        state: present
        update_cache: yes
        
    - name: Copy Nginx configuration file
      ansible.builtin.copy:
        src: /root/ansible/nginx.conf
        dest: /etc/nginx/nginx.conf
        
    - name: Restart Nginx service
      ansible.builtin.service:
        name: nginx
        state: restarted

Key Components Explained

• hosts: all: Specifies that the playbook should run on all hosts listed in the inventory file.
• become: yes: Ensures tasks requiring elevated privileges (sudo) are executed as the root user.
• Tasks:
  • Update apt-cache: Uses the APT module to update the package cache.
  • Install Nginx: Installs the Nginx web server.
  • Copy Configuration File: Copies a custom configuration file to the appropriate directory on the target hosts.
  • Restart Nginx: Restarts the Nginx service to apply the new configuration.

Running the Playbooks

Save the desired playbook as a YAML file (e.g., deploy_nginx.yaml), and run it using:

ansible-playbook deploy_nginx.yaml -i inventory.ini

Ensure that your inventory file (inventory.ini) includes all necessary hosts and connection details.

Additional Examples

Show Debug Message

Use the debug module to display a message during playbook execution:

- name: Show Debug Message
  ansible.builtin.debug:
    msg: "Test Message"

Use a Shell Command

Run a shell command and capture the output:

- name: Execute Shell Command
  ansible.builtin.shell:
    cmd: echo "Hello, Ansible!"
  register: shell_output # Register the command output as a variable

- name: Display Shell Output
  ansible.builtin.debug:
    msg: "Output is: {{ shell_output.stdout }}" # Display the command output

Playbook with Conditional Statements

This playbook demonstrates the use of conditional statements to check if a file exists and take action based on the result:

- name: Check if File Exists
  ansible.builtin.shell:
    cmd: ls /path/to/file
  register: file_output
  ignore_errors: yes

- name: File Exists
  ansible.builtin.debug:
    msg: "File exists"
  when: file_output.rc == 0

- name: File Does Not Exist
  ansible.builtin.debug:
    msg: "File does not exist"
  when: file_output.rc != 0

Exit Codes Overview

Understanding exit codes is crucial when dealing with shell commands:

Exit Code	Description
0	Success: The command completed successfully.
1	General error: Catchall for general errors.
2	Misuse of shell builtins (e.g., cd).
126	Command invoked cannot execute.
127	Command not found.
128	Invalid argument to exit.
130	Script terminated by Control-C.
137	Script terminated by kill (or OOM).
139	Segmentation fault.
141	Script terminated by kill -13 (SIGPIPE).
143	Script terminated by kill -15 (SIGTERM).
255	Exit status out of range (exceeds 255).