Hands-On-Ansible

This repository have the goal of providing an opportunity for all the people to get an insight on how to play with Ansible.

What is Ansible?

Ansible is an open source IT configuration management, deployment, and orchestration tool, based on Python.

Architecture

• There are two types of machines in the Ansible architecture: the control node and managed hosts.
• Ansible software is installed on the control node and all of its components are maintained on it.
• The managed hosts are listed in a host inventory, a text file on the control node that includes a list of managed host names or IP addresses.
• Ansible uses SSH as a network transport to communicate with the managed hosts.
• The modules referenced in the playbook are copied to the managed hosts.
• Then these modules are executed, in order, with the arguments specified in the playbook.

Ansible Core Components

1. Inventory

An inventory is a text file listing hostnames usually grouped by functionality. Files are organized as hosts and groups. A set of hosts can be under a group name. A host can be in more than one group.

Recommendations on the Inventory

• Give inventory nodes a human-friendly name rather than just putting the IP addresses or DNS hostnames.

Types of Ansible Inventories:

a) Static Inventory

• Static inventory is default inventory and is defined in the /etc/ansible/ansible.cfg file.

b) Dynamic Inventory

• Dynamic inventory to pull files from dynamic sources and cloud.
• If you have the setup where you add and remove the hosts very frequently, then keeping your inventory always up-to-date become a little bit problematic. In such case Dynamic inventory comes into picture.
• These are generally Python or Shell scripts for dynamic environments (for example cloud environments).

2. Ansible Modules

• Modules control system resources like services, packages, files, system commands, etc.
• It can be executed directly in CLI or through playbooks.
• Modules are language independent and idempotent(Avoid changes to system unless needed).
• There are three types of Ansible modules they are Core, Extras, and Custom modules
  • Core and Extras modules are always available. Ansible looks for custom modules on the control node in directories defined by the $ANSIBLE_LIBRARY environment variable.

  Running ad hoc commands

• To execute an ad hoc command, administrators need to execute the ansible command using the following syntax:

ansible host-pattern -m module [-a 'module argument'] [-i inventory]

3. Ansible Configuration File

• Simply Configuration file modifies the behaviour of ansible.

• When an ad hoc command is executed, First, the Ansible configuration file is consulted for various parameters.

• By default, connections to managed hosts are initiated using the SSH protocol.

• The SSH protocol requires the connection to be established using an account on the managed host.

• This account is referred by Ansible as the remote user and is defined using the remote_user parameter under the [defaults] section of the configuration file.

  $ ansible node -m ping

• The recommended practice is to create an ansible.cfg file in a directory from which you run Ansible commands.

4. Ansible Playbook

• Playbooks are executed using the ansible-playbook command.
  • Playbook contains Plays
  • Plays contains Tasks
  • Tasks call Modules
  • Tasks run sequentially
  • Tasks triggers handlers
  • Handlers run once at the end
• Complex playbooks may contain a long list of tasks.With Ansible version 2.0, blocks offer another alternative to task organization.

5. Ansible Roles

• Roles provide Ansible with a way to load tasks, handlers, and variables from external files.
• Static files and templates can also be associated and referenced by a role.
• Roles can be written so they are general purpose and can be reused.
• Some basic advantages of roles:
  1. Roles group content, allowing easy sharing of code with others.
  2. Roles can be written that define the essential elements of a system type: web server, database server, git repository, or other purpose.
  3. Roles make larger projects more manageable.
  4. Roles can be developed in parallel by different administrators.

6. Ansible Tasks

• Tasks are the individual actions that Ansible performs, such as copying a file, installing a package, or restarting a service.
• Tasks can be grouped together into playbooks or roles.

7. Ansible Collections

• Ansible Collections are a way of packaging and distributing collections of related Ansible content, including playbooks, roles, modules, and plugins.
• They allow for sharing and reuse of Ansible content across different projects and organizations.
• Collections can be installed using ansible-galaxy and once installed, their modules can be used in playbooks like any other Ansible module.

ansible-galaxy collection install community.general

8. Ansible Variables

• Ansible supports variables that can be used to store values that can be reused throughout files in an entire Ansible project.
• Simply we can manage dynamic values in our project.
• Quotes are mandatory when we use variables is used as the first element.
• Some examples of values that variables might contain include:
  1. Users to create.
  2. Packages to install.
  3. Services to restart.
  4. Files to remove.
  5. Archives to retrieve from the Internet.

9. Ansible Template

• In Ansible, a template is a file that has placeholders, which can be filled in with specific values during the playbook execution.
• Templates allow you to create reusable configuration files, scripts, or any other text file that needs to be customized for different systems or environments.
• Templates use Jinja2, a powerful templating engine, to provide a flexible and dynamic way to generate text files. The Jinja2 syntax allows you to include logic statements, such as loops and conditional statements, as well as variables and filters.
• Some common use cases of Ansible templates include:
  • Generating configuration files
  • Managing application settings
  • Generating scripts

10. Ansible Facts

• Ansible facts are variables that are automatically discovered by Ansible from a managed host.

• Facts are pulled by the setup module and contain useful information stored into variables that administrators can reuse.

• Fact variables can be used as part of playbooks, in conditionals, loops, or any other dynamic statement that depends on a value for a managed host.

• We can also create custom facts and push them to a managed node.

  Displaying facts from a hosts:

ansible host-pattern -m setup

11. Ansible Handlers

• Handlers are tasks that are triggered by another task, such as restarting a service after a configuration file has been updated.
• Handlers are useful when you need to perform a specific action only when a change has been made. For example, if a configuration file is modified, you might want to restart a service that is using that configuration file.
• Handlers have a unique name and can be triggered by using the "notify" keyword in a task.

12. Ansible Plugins

• Plugins are used to extend Ansible's functionality, such as adding new modules, inventory sources, and connection types.
• Plugins can be of different types, such as action, connection, inventory, and lookup plugins.

13. Ansible Vault

• Vault is used to protect sensitive data in your playbooks.

  • To create a new encrypted data file, run the following command:

ansible-vault create secret.yml

Similarly we can use edit, encrypt, decrypt and rekey, for more details on how to work with vault files, check manual page:

man ansible-vault