Ansible is an open source, powerful automation software for configuring, managing and deploying software applications on the nodes without any downtime just by using SSH. Today, most of the IT Automation tools runs as an agent in remote host, but ansible just need a SSH connection and Python (2.4 or later) to be installed on the remote nodes to perform its action.
How Ansible Works?
There are many similar automation tools available like Puppet, Capistrano, Chef, Salt, Space Walk etc, but Ansible categorize into two types of server: controlling machines and nodes.
The controlling machine, where Ansible is installed and Nodes are managed by this controlling machine over SSH. The location of nodes is specified by controlling machine through its inventory.
The controlling machine (Ansible) deploys modules to nodes using SSH protocol and these modules are stored temporarily on remote nodes and communicate with the Ansible machine through a JSON connection over the standard output.
Ansible is agent-less, that means no need of any agent installation on remote nodes, so it means there are no any background daemons or programs are executing for Ansible, when it’s not managing any nodes.
Ansible can handle 100’s of nodes from a single system over SSH connection and the entire operation can be handled and executed by one single command ‘ansible’. But, in some cases, where you required executing multiple commands for a deployment, here we can build playbooks.
Playbooks are bunch of commands which can perform multiple tasks and each playbooks are in YAML file format.
Prerequisites
- Distro: RHEL/CentOS/Debian/Ubuntu Linux
- Jinja2: A modern and designer friendly templating language for Python.
- PyYAML: A YAML parser and emitter for the Python programming language.
- parmiko: Native Python SSHv2 protocol library.
- httplib2: A comprehensive HTTP client library.
- Most of the actions listed in this post are written with the assumption that they will be executed by the root user running the bash or any other modern shell.
Setup EPEL Repository
First we need to enable ‘epel’ repository for CentOS 7 on the controller server because Ansible package is not available in the default yum repositories, so we will be using below commands to Enable EPEL repository on CentOS 7 / RHEL 7.
# rpm -iUvh http://dl.fedoraproject.org/pub/epel/7/x86_64/Packages/e/epel-release-7-11.noarch.rpm
Now run the command to update your operating system.
# yum -y update
Install Ansible
Now we can install Ansible using the ‘yum’ command that will install it including its required dependencies.
# yum install ansible
Once installed check the version you installed using
# ansible –version