Preparing for the test

• Tools for preparation
• Quizzes
• Flash Cards
• Study Guide
• Learning Activites
• Interactive Diagram

A Brief Word on YAML

What is YAML and Why Does it Matter?

• YAML is a markup language used for formatting data
• YAML is generally considered easier for humans to read
• Ansible Playbooks use YAML syntax

Basic YAML Syntax

• YAML is composed of key-value pairs, lists, and dictionaries
• Files items are designated with a single hyphen and a space
• Each list item should have the same indentation
• Dictionaries are designated with a colon and a space followed by indented key-value pairs

Multiple Line Values

• It is frequently useful when working on Ansible playbooks to format input with line breaks
• YAML has a means of letting us do this
• The pipe and riht angle bracket (| ans >) may be used to allow for line breaks within YAML
• Pipe will take each line break as part of the input in the data that follows it
• The right-angle bracket will ignire line breaks in the data that follows it
• A typical use case is breaking up parameters for readability

Quotes and When to Use Them

• YAM has a relatively small set of special characters: [] {} : > |
• You must use double quotes to espace a special character
• Technically, you only need to escape a colon if it is followed by a space
• You will frequently need to escape curly braces {} as they are special to both YAML and Ansible:

Ansible variables are formatted "{{variable_name}}"- the double quotes are required.

This will be discussed more when we go overvariables in Ansible

• Boolean values auto-convert in YAML
• If you want a literal "YES", you must use quotes
• Floating Point Numbers are taken as numeric unless quoted

Understanding core components of Ansible

Overview

• Inventories
• Modules
• Variable
• Facts
• Plays
• Playbooks
• Configuration Files

Inventories

• Inventories are how Ansible can locate and run against multiple systems
• You can think of an inventory as a list of hosts
• By default, Ansible uses /etc/ansible/hosts as its inventory, but this is configurable
• Inventories may be formatted as an INI file or as a yaml file. Note: file formats ar interchangeable
• Inventory files may simply consist of a list of hostnames but can be musch more robust
• It is also possible to define groups of hosts, host or group level variables, and groups of groups within the inventory
• There are a number of variables that may be used within the inventory to control how ansible connects to an interacts with target hosts

$ vim -R /etc/ansible/hosts

[labservers]

scoldham2.mylabserver.com

$ cd ansible

vim inv.ini

scoldham2.mylabserver.com

[httpd]

scoldham3.mylabserver.com

scoldham4.mylabserver.com

[labservers]

scoldham[2:6].mylabserver.com

ansible scoldham2.mylabserver.com -m ping

scoldham2.mylabserver.com | SUCCESS => { "changed": false, "ping":"pong"}

ansible all -m ping

scoldham2.mylabserver.com | SUCCESS => { "changed": false, "ping":"pong"}

ansible -inv.ini httpd -m ping

scoldham3.mylabserver.com | SUCCESS => { "changed": false, "ping":"pong"}

scoldham4.mylabserver.com | SUCCESS => { "changed": false, "ping":"pong"}

Modules

• Modules are essentially tools for particular tasks
• Modules can take (and usually do) take parameters
• They return JSON
• Can run from the command line or within a playbook
• There are a significant number of modules for many kinds of work
• Custom modules can be written

Variables

• Variable names should be letters, numbers, and underscores
• Variables should always start with a letter
• Can be scoped by a group, host, or even in a playbook
• Typically used for configuration values and various parameters
• Variables can also be used to store the return value of executed commands
• Ansible variables may also be dictionaries
• There are a number of predefiner variable used by ansible

Facts

• Facts provide certain information about a given target host
• Facts are discovered by Ansible automatically when it reaches out to a host
• Fact gathering may be disabled
• Facts may be cached between playbook executions, but this is not default behavior

Plays and Playbooks

• The goal of a play is to map a group of hosts to some well-defined roles
• A play may use one or more modules to achieve a desired end state on a group of hosts
• A playbook is a series of plays
• A playbook may deploy new web servers, install a new application to existing application servers, and run SQL against some database servers to support the new application

Configuration Files

• Several possible locations (in order processed)

  • ANSIBLE_CONFIG ( an environment variable)

  • ansible.cfg (in the current directory)

  • .ansible.cfg (in the home directory)

  • /etc/ansible/ansible.cfg

• Configuration can also be set in environment variables

• Some commonly used settings:

  • ansible_managed
  • forks
  • inventory

Ad-Hoc Ansible Commands

overview

• What is an ad-hoc command in Ansible?
• Use cases for ad-hoc commands
• Ad-hoc vs Playbook
• Ansible command syntax
• Common modules

What is an ad-hoc command in Ansible?

• You can run ansible either ad-hoc or as a playbook
• Both methods have the same capabilities
• Ad-hoc commands are effectively one-liners

Use cases for Ad-hoc

• Operational commands

  • Checking log contents
  • Daemon control
  • Process management

• Informational commands

  • check installed software
  • check system properties
  • Gather system performance information (CPU, disk space, memory use)

• research

  • work with unfamiliar modules on test systems

Ad-hoc vs Playbook

Demonstration