Master Ansible: From Basics to Advanced Automation with Playbooks

Ansible Overview

Ansible is a popular open‑source automation tool that simplifies configuration management, application deployment and task execution across thousands of hosts using simple, agent‑less SSH communication.

Key Features

Written in Python, easy for developers to extend.

Thousands of built‑in modules cover most tasks.

One command can manage thousands of machines.

Agent‑less, uses SSH.

Adopted by major cloud providers.

Ansible Roles

Users: how to interact with Ansible.

Toolset: inventory, modules, plugins, API.

Targets: hosts and groups that can be managed.

Users

Ansible can be driven via CMDB integration, public/private APIs, ad‑hoc commands or pre‑written playbooks (see diagram).

Toolset

The core components are Inventory, Modules, Plugins and API.

Ansible Playbooks : YAML files that define ordered tasks.

Inventory : host list, supports grouping.

Modules : execution units, built‑in or custom.

Plugins : extend functionality (connection, loop, vars, filter).

API : programmatic access for integration.

Targets

Ansible can manage Linux, non‑Linux systems and various network devices.

Installation and Configuration

Installation

Install via YUM on a Linux control node (RedHat, Debian, CentOS). Example repository setup and installation commands:

# 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

Verify Installation

# ansible --version
ansible 2.3.1.0
config file = /etc/ansible/ansible.cfg
python version = 2.7.5 (default, Nov 6 2016, 00:28:07) [GCC 4.8.5 20150623 (Red Hat 4.8.5-11)]

SSH Key Setup

Create RSA key pair and copy the public key to managed hosts to enable password‑less SSH.

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

Inventory Configuration

The inventory file (default /etc/ansible/hosts) defines groups and hosts. Example:

[web]
192.168.100.20
192.168.100.30
[test]
www.benet.com:222
[mail]
yj1.kgc.cn
yj[2:5].kgc.cn

Hosts can belong to multiple groups and groups can be referenced with the -i or --inventory-file options.

Running Commands

Examples of ad‑hoc commands, module usage and playbook execution are provided, such as pinging all hosts, listing groups, checking disk usage, installing packages, managing services, users, and files.

# ansible all -m ping
# ansible web -m command -a "df -hT"
# ansible web -m yum -a "name=httpd state=present"
# ansible web -m service -a "name=httpd enabled=yes state=restarted"

Playbooks

Playbooks are YAML files that describe a series of tasks. They support variables, handlers, roles and tags. Example snippet:

---
- hosts: web1
  remote_user: root
  tasks:
    - name: add user
      user: name=user1 state=present
      tags: aaa
    - name: copy file
      copy: src=/etc/passwd dest=/home
      tags: ccc

Handlers run only when notified by a task, ensuring actions such as service restarts occur after configuration changes.

Roles

Roles encapsulate related tasks, files, templates and variables under a directory structure (e.g., /etc/ansible/roles/mysql). They can be included in playbooks to reuse common functionality.

- hosts: web
  roles:
    - mysql
    - httpd