Ansible is a configuration management open source software. It can use to setup client/remote system,
or in other words install your require packages to client/remote system. Ansible usage of SSH for transport. Ansible script is written into YML(yet another markup language).

How does ansible works?
Ansible sends its commands one by one to remote machine in each separate SSH connection. Ansible never install any agent to remote machine, that’s what make ansible a powerful configuration and management tool.

How does ansible works in background?

you describes your commands in YML file.
whenever you run its converted into relative shell script command.
it copies each command to target node via ssh
runs each command
collects the outputs and returns it.

How to install ansible on your linux system?
So the machine you are using to run ansible yml script that should have ansible runner to run it. ansbile never get installed on remote machine, but it must be present on the machine that which is used to run ansible script.
how to install ansible in ubuntu linux system ?

sudo apt-get update
sudo apt-get install -y git
sudo apt-get install software-properties-common
sudo apt-add-repository -y ppa:ansible/ansible
sudo apt-get update -y
sudo apt-get install -y ansible

how to install ansible on CentOS, RHEL, or Scientific Linux ?

sudo yum update -y
sudo yum install -y ansible

What is “hosts” file(inventory file) in ansible?
In Simple language here you enter the addresses of remote machine. So the whenever you run ansible script, ansbile-runner will look into hosts file and get the remote address.
what more you can do with host file is, you can define multiple remote machine addresses, group them, and one host can have multiple groups.
Here is one simple example of host file:

[remotemachine]
xx.xx.xx.xx

Here is one complex example of “hosts” file

[south_east_aisa]
xx.xx.xx.x1
xx.xx.xx.x2

[south_aisa]
xx.xx.xx.x1
xx.xx.xx.x2
xx.xx.xx.x3

[asia:children]
south_asia
south_east_asia

[aisa:vars]
foo_var=hello asia

[world:children]
asia
africa
america

Note: you can hosts file detail into file into “/etc/ansible/hosts” OR define anywhere and use command “-i path/to/your/hosts” while running ansible script.

How to run ansible script?
in simple way ansbile can be run by using command:

ansible-playbook playbook.yml

if you want to define host file location then use this

ansible-playbook playbook.yml -i path/to/hosts

if you want to run some of your command using super user

ansible-playbook playbook.yml -s

if you want to run ansible command with login as some_user to remote machine

ansible-playbook playbook.yml -u user_name

if you wants to run ansible command and provide private-key to access remote machine then

ansible-playbook playbook.yml –private-key=yourkey.pem

to check ansible script before run

ansible-playbook playbook.yml –check

to run ansible script on your local system for testing

ansible-playbook playbook.yml -c local

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