Master Ansible: From Basics to Advanced Automation with Playbooks

Ansible Overview

Ansible is a popular open‑source automation tool that simplifies operations by allowing engineers to execute tasks across many hosts with minimal effort, reducing manual errors and increasing efficiency.

Key Features

Written in Python, easy to extend.

Thousands of built‑in modules.

One command can manage thousands of machines.

Agent‑less, communicates over SSH.

Adopted by major cloud providers and enterprises.

Ansible Roles

Users : Interact with Ansible via CMDB integration, public/private APIs, ad‑hoc commands, or pre‑written playbooks.

Toolset : Consists of Inventory, Modules, Plugins, and API.

Targets : Any Linux or non‑Linux host, as well as network devices.

Installation & Basic Configuration

Ansible can be installed on a Linux control node (e.g., RedHat, Debian, CentOS) using YUM:

<code># cd /mnt/ansiblerepo/ansiblerepo/repodata/
# vim /etc/yum.repos.d/local.repo
[local]
name=centos
baseurl=file:///mnt/ansiblerepo/ansiblerepo
enabled=1
gpgcheck=0
# yum -y install ansible</code>

Verify installation:

<code># ansible --version
ansible 2.3.1.0
config file = /etc/ansible/ansible.cfg
python version = 2.7.5</code>

Set up password‑less SSH for remote hosts:

<code># ssh-keygen -t rsa
# ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected]
# ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected]</code>

Inventory Configuration

The inventory file (default

/etc/ansible/hosts

) defines host groups. Example entries:

<code>[web]
192.168.100.20
192.168.100.30
[test]
www.example.com:222
mail
yj1.kgc.cn
yj[2:5].kgc.cn</code>

Run commands against groups or individual hosts using the

-i

or

--inventory-file

options.

Core Commands

ansible

: Execute ad‑hoc tasks (e.g.,

ansible all -m ping

).

ansible-doc

: Show module documentation.

ansible-playbook

: Run YAML playbooks.

ansible-console

: Interactive shell for Ansible.

Common Modules

command : Run a command without shell features.

shell : Run a command with full shell support.

copy : Transfer files to remote hosts.

hostname : Manage remote hostnames.

yum : Manage packages on RPM‑based systems.

service : Control system services.

user : Manage user accounts.

Playbook Basics

Playbooks are YAML files that describe a series of tasks. A minimal example:

<code>---
- hosts: web1
  remote_user: root
  tasks:
    - name: add user
      user:
        name: user1
        state: present
    - name: copy file
      copy:
        src: /etc/passwd
        dest: /home
</code>

Key elements include

hosts

,

remote_user

,

tasks

,

handlers

, and

roles

. Playbooks can be validated (

--syntax-check

), tested (

-C

), and executed (

ansible-playbook playbook.yml

).

Handlers

Handlers run only when notified by a task and execute after all tasks finish. Example:

<code>- name: change port
  command: sed -i 's/Listen 80/Listen 8080/g' /etc/httpd/conf/httpd.conf
  notify: restart httpd

handlers:
  - name: restart httpd
    service:
      name: httpd
      state: restarted</code>

Roles

Roles are reusable collections of files, templates, tasks, handlers, and variables stored under

/etc/ansible/roles/

. A typical role directory contains

files

,

templates

,

tasks

,

handlers

,

vars

,

defaults

, and

meta

. Roles can be invoked in a playbook:

<code>- hosts: web
  roles:
    - mysql
    - httpd</code>

Practical Example: Installing MariaDB

A playbook can automate the installation of MariaDB, copy configuration files, restart the service, create a database, and grant privileges.

Overall, Ansible provides a powerful, agent‑less framework for automating configuration management, application deployment, and routine operational tasks across heterogeneous environments.