Basics of Ansible - Sahil Davawala

 DevOps - a clipped compound of "development" and "operations"
 Automate the software integration, testing, deployment, and infrastructure
changes.
 Improve automation and measurement of system metrics.
 The best powerful automation tool which can help us in achieving everything is
ANSIBLE.

 Basics of Ansible
 Usage of Ansible
 Ansible without playbook i.e. through Adhoc commands
 Ansible with playbook
 Ansible modules
 Installation of a package on multiple instances followed by a Demo.

It is an IT automation tool which can configure systems, deploy
software, and orchestrate more advanced IT tasks such as
continuous deployments or zero downtime rolling updates.

 Ansible is an agent-less and uses a PUSH(SSH) approach.
 It is developed by RedHat.
 It is an OpenSource application.
 Platforms supported are Linux & Windows.
 Linux for control machine & Windows for managed nodes.
 Latest version of ansible is 2.3
Reference URL : https://github.com/ansible/ansible/releases
 Major companies using Ansible are Atlassian, CISCO, EA Sports, NASA, RedHat,
Twitter and many more.

Control Machine Requirements
 Currently Ansible can be run from any machine with Python 2.6 or 2.7 installed
Managed Node Requirements(Target Host)
 On the managed nodes, you need a way to communicate, which is normally SSH.
You also need Python 2.6 or later installed for the same.

Chef/Puppet Ansible
• Needs to be installed on Agents.
• Agents pull changes from a master.
• Communication channel used is their own
(usually not SSH)
• Complicated
setup/architecture/installation
• Complicated orchestration.
• Chef uses Ruby in backend and pure Ruby
DSL for configuration.
• Puppet using Ruby in backend and uses
Puppet DSL for configuration.
• Need not be installed on Agents.
• Pushes the changes to Agents whenever
required.
• Uses SSH
• Easy installation and architecture
• Simplified orchestration.
• Ansible backed is on Python.
• Uses YAML as configuration files.

 Installing Ansible on CentOS :
 To get Ansible for CentOS 7, first ensure that the CentOS 7 EPEL repository is
installed:
sudo yum install epel-release
sudo yum update
 Once the repository is installed, install Ansible with yum:
sudo yum install ansible
 Installing Ansible on Ubuntu :
sudo apt-get install software-properties-common
sudo apt-add-repository ppa:ansible/ansible
sudo apt-get update
sudo apt-get install ansible

 Run command : ansible –version
 Example output :
ansible 2.3.1.0
config file = /etc/ansible/ansible.cfg
configured module search path = Default w/o overrides
NOTE : If anyone wants to execute the playbook on a remote machine
then it is mandatory to have Python libraries installed on that remote machine.

 Certain settings in Ansible are adjustable via a configuration file. This
configuration file is know as ANSIBLE CONFIG
 Ansible allows configuration of settings via environment variables. If these
environment variables are set, they will override any setting loaded from the
configuration file.
 Here is the order in which configuration file will be processed.

 We use YAML because it is easier for humans to read and write than other common data formats like XML or JSON.
 All YAML files (regardless of their association with Ansible or not) can optionally begin with --- and end with ... This is part of the YAML
format and indicates the start and end of a document.
 All members of a list are lines beginning at the same indentation level starting with a "- " (a dash and a space):
Example :
---
# A list of tasty fruits
fruits:
- Apple
- Orange
- Strawberry
- Mango
…
 A dictionary is represented in a simple key: value form (the colon must be followed by a space):
Example :
# An employee record
martin:
name: Martin D'vloper
job: Developer
skill: Elite

 Ansible works against multiple systems in our infrastructure at a particular point
of time.
 It does this by selecting portions of systems listed in Ansible’s inventory which
defaults to being saved at the location : /etc/ansible/hosts.
 You can specify a different inventory file using the -i <path> option on the
command line
 Example : ansible-playbook -i playbook.yml
 It can be used in both commands & playbooks.
 Types of inventories includes basic list, shell script, python script, advanced script
like ec2,etc.

 To ping multiple servers at a time(which are existing in inventory file) :
 ansible –m ping all
 For creating a new user and manipulation of existing user accounts :
 ansible all -m user -a "name=foo password=<crypted password here>”
 Ensure a service is started on all webservers:
 ansible webservers -m service -a "name=httpd state=started"

 Ansible adhoc commands have the limitation in complex scenarios so to overcome
this and make the automation easy & robust, playbooks were introduced.
 Playbooks can be used to manage configurations and deployments to remote
machines.
 Here is the example how to use a playbook.
 ansible-playbook first.yml –e name=webservers1

 apt module
 yum module
 package module
 shell module
 command module
 user module
 hostname module

 The apt module manages the apt packages.
Example :
- name: Remove "foo" package.
apt:
name: foo
state: absent
- name: Install the package "foo"
apt:
name: foo
state: present

 Installs, upgrade, removes, and lists packages and groups with the yum package
manager.
Example :
- name: install the latest version of Apache
yum:
name: httpd
state: latest

 Installs, upgrade and removes packages using the underlying OS package
manager.
Example :
- name: install the latest version of ntpdate
package:
name: ntpdate
state: latest

 The shell module takes the command name followed by a list of space-delimited
arguments. It is almost exactly like the command module but runs the command
through a shell (/bin/sh) on the remote node.
Example :
- name: Executing a Command Using Shell Module
shell: ls -lrt > temp.txt
The above command lists all the files in the current folder and writes that to the file i.e.
temp.txt.

 The command module takes the command name followed by a list of space-
delimited arguments.
 The given command will be executed on all selected nodes. It will not be processed
through the shell, so variables like $HOME and operations
like "<", ">", "|", ";" and "&" will not work.
Example :
- name: Executing a command using command module.
command: cat hello.txt
The above command displays the content of the file hello.txt

 Manage user accounts and user attributes.
Example :
- user:
name: johnd
comment: "John Doe"
uid: 1040
group: admin

 Set system’s hostname, supports most OSs/Distributions, including those using
systemd.
 Note, this module does NOT modify /etc/hosts. You need to modify it yourself using
other modules like template or replace.
Example :
- hostname:
name: web01

 Ansible command using a direct agent.
 Ansible command using an Inventory group.
 Ansible playbook for direct host (agent)
 Ansible playbook split into multiple tasks.
 Ansible playbook installing a service on multiple hosts.

Basics of Ansible - Sahil Davawala

Basics of Ansible - Sahil Davawala

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