Introduction to Ansible

Introduction to Ansible
By-
Himanshu Rajput
Software Consultant
Knoldus Software LLP

Agenda
1. What is Ansible
2. Why Ansible
3. Ansible Use Cases
4. Architecture of Ansible
5. Configuration Management With Ansible
6. Quick Demo

What is Ansible
➔ Ansible is an open-source configuration management and
provisioning tool, similar to Chef, Puppet or Salt.
➔ It uses SSH to connect to servers and run the configured
Tasks. Ansible lets you control and configure nodes from a
single machine.
➔ What makes it different from other management software is
that Ansible uses SSH infrastructure. The project was founded
in 2013 and bought by Red Hat in 2015.

Why Ansible
● No Agent- As long as the box can be ssh’d into and it has python,
it can be configured with Ansible.
● Idempotent- Ansible’s whole architecture is structured around the
concept of idempotency. The core idea here is that you only do
things if they are needed and that things are repeatable without
side effects.
● Declarative Not Procedural- Other configuration tools tend to be
procedural do this and then do that and so on. Ansible works by
you writing a description of the state of the machine that you want
and then it takes steps to fulfill that description.
● Tiny Learning Curve- Ansible is quite easy to learn. It doesn’t
require any extra knowledge.

Ansible Use Cases
● Provisioning
● Configuration Management
● App Deployment
● Continuous Delivery
● Security & Compliance
● Orchestration

Architecture of Ansible
disparate

Inventory
The Inventory is a description of the nodes that can be accessed
by Ansible. By default, the Inventory is described by a
configuration file, whose default location is in./etc/ansible/hosts
The configuration file lists either the IP address or hostname of
each node that is accessible by Ansible.
Every host is assigned to a group such as web servers, db
servers etc. The inventory file can be in one of many formats
such as yaml, INI etc

Example of an Inventory file
mail.example.com
[webservers]
foo.example.com
bar.example.com
[dbservers]
one.example.com
two.example.com
three.example.com

Playbook
Playbooks are simple YAML files. These files are descriptions of
the desired state of your systems. Ansible then does the hard
work of getting your systems to that state no matter what state
they are currently in. Playbooks make your installations,
upgrades and day-to-day management repeatable and reliable.
Playbooks are simple to write and maintain. Playbooks are
written in a natural language so they are very easy to evolve and
edit.
Playbook contains Plays.
Plays contain tasks.
tasks call modules.

Example of an ansible playbook
---
- hosts: webservers
remote_user: root
tasks:
- name: ensure apache is at the latest version
yum: name=httpd state=latest
- name: ensure apache is running
service: name=httpd state=started enabled=yes

Modules
There are over 1000 modules provided by Ansible to automate
every part of the environment. Modules are like plugins that do
the actual work in Ansible, they are what gets executed in each
playbook task.
Each module is mostly standalone and can be written in a
standard scripting language (such as Python, Perl, Ruby, Bash,
etc.). One of the guiding properties of modules is idempotency,
which means that even if an operation is repeated multiple times,
it will always place the system into the same state.

Example of Modules
There are lots of modules such as :
Service, file, copy, iptables etc.
Any Module can be used as :
ansible 127.0.0.1 -m service -a "name=httpd state=started"
ansible localhost -m ping

Roles
Roles are a way to group tasks together into one container. We
could have a role for setting up MySQL, another one for
configuring iptables etc.
Roles makes it easy to configure hosts. Any role can be
performed on any host or group of hosts such as:
- hosts: all
roles:
- role_1
- role_2

Companies that are using Ansible

Configuration Management with Ansible
Ansible is the simplest solution for configuring the nodes. It’s designed
to be minimal in nature, consistent, secure and highly reliable. Any
developer, tester or IT manager can easily configure nodes. Any IT
person can write playbooks easily.
Ansible configurations are simple data descriptions of your
infrastructure (human readable) ensuring everyone on your team will be
able to understand the meaning of each configuration task.
Ansible requires nothing more than a password or SSH key in order to
start managing systems and can start managing them without installing
any agent software.

References
1.docs.ansible.com
2.https://www.digitalocean.com/community/tutori
als/configuration-management-101-writing-
ansible-playbooks

Introduction to Ansible

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