What is Ansible?

• Ansible is a software tool that provides simple but powerful automation for cross-platform computer support. It is primarily intended for IT professionals, who use it for application deployment, updates on workstations and servers, cloud provisioning, configuration management, intra-service orchestration, and nearly anything a systems administrator does on a weekly or daily basis.

• Ansible doesn't depend on agent software and has no additional security infrastructure, so it's easy to deploy.

How Ansible Works?

• Ansible works by connecting to nodes (clients, servers, or whatever you're configuring) on a network, and then sending a small program called an Ansible module to that node. Ansible executes these modules over SSH and removes them when finished.

• SSH keys are the most common way to provide access, but other forms of authentication are also supported.

Ansible Architecture: Nodes and Modules

• Ansible's Architecture is based on the concept of a control node and a managed node. The platform is executed from the control node where a user runs the ansible-playbook command. There must be at least one control node; a backup control node can also exist. The devices being automated and managed by the control node are known as managed nodes.

• Ansible automates Linux and Windows by connecting to managed nodes and pushing out small programs called Ansible modules. Ansible executes these modules, which are the resource models of the desired system state, over Secure Socket Shell (SSH) by default and removes them when finished.

• Ansible modules are written in Python and can be written in any language. Ansible modules are reusable, standalone scripts that can be used by the Ansible API, Ansible Playbooks, or Ansible Galaxy.

For a more comprehensive version of this blog post, please refer to the previous entry where you can find a thorough and hands-on rephrasing of the content:

• https://devops-rohit.hashnode.dev/day-55-grasping-configuration-management-with-ansible

Create 3 Instances on AWS EC2 with the following names:

• Ansible_Master_Server

• Node_1

• Node_2

Installation of Ansible on AWS EC2 (Master Node)

#!/bin/bash
sudo apt-add-repository ppa:ansible/ansible
sudo apt update
sudo apt install ansible

sudo chmod 777 install.sh
sudo ./install.sh

ansible --version

Create SSH key on Master Node.

cd ~/.ssh
ssh-keygen

What is a Hosts file?

• In the context of Ansible, a host file (also known as an inventory file) is configuration file used to define and organize the list of target hosts that Ansible should manage.

Where is the Hosts file located?

• Ansible uses this file to map target hosts to managed nodes. The host file is usually located in /etc/ansible/hosts.

• So, open the host file and add the IP addresses of the Nodes:

sudo vim /etc/ansible/hosts

[servers]
Node_1 ansible_host= <Public IP-Adddress of Node-1>
Node_2 ansible_host= <Public IP-Adddress of Node-2>

[all:vars]
ansible_python_interpreter=/usr/bin/python3
ansible_ssh_private_key_file=/home/ubuntu/.ssh/id_rsa

Now we will ping the Node server using Master Node by pasting the public SSH key of Master Node to the Node server.

# Open Node_1
cd /home/ubuntu/.ssh
vim authorized_keys

# Open Node_2
cd /home/ubuntu/.ssh
vim authorized_keys

Task-01

Write an ansible ad hoc ping command to ping 2 servers from the inventory file.

ansible all -m ping
# or
ansible servers -m ping
# or
ansible all -m ping -i /etc/ansible/hosts

Write an ansible ad hoc command to check uptime.

• ansible: This is the command-line tool used to interact with Ansible.

• all: This refers to the group of hosts or servers on which you want to execute the specified command. In this case, "all" means that the command will be executed on all the hosts specified in the inventory.

• -a: This option specifies that you are providing an ad-hoc command to execute on the targeted hosts.

• uptime: This is the actual command you want to run on the remote hosts. In this case, it's the "uptime" command, which provides information about how long the system has been running.

• -i /etc/ansible/hosts: This option specifies the inventory file to use. The inventory file contains a list of hosts or IP addresses that Ansible will manage. In this case, the inventory file is located at "/etc/ansible/hosts".

ansible all -a  uptime -i /etc/ansible/hosts

Now we will use the ansible ad-hoc command for checking the version of Python installed on Node_1 and Node_2.

ansible all -b -m shell -a 'sudo python3 --version

Happy Learning :)