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.
Installing Ansible
To begin exploring Ansible as a means of managing our various servers, we need to install the Ansible software on at least one machine. We will be using an Ubuntu 16.04 server for this section.
The best way to get Ansible for Ubuntu is to add the project’s PPA (personal package archive) to your system. We can add the Ansible PPA by typing the following command:
# apt-add-repository ppa:ansible/ansible
Press ENTER to accept the PPA addition.
Next, we need to refresh our system’s package index so that it is aware of the packages available in the PPA. Afterwards, we can install the software:
# apt-get update # apt-get install ansible
As we mentioned above, Ansible primarily communicates with client computers through SSH. While it certainly has the ability to handle password-based SSH authentication, SSH keys help keep things simple. You can follow the tutorial linked in the prerequisites to set up SSH keys if you haven’t already.
We now have all of the software required to administer our servers through Ansible.
Read More: How to install Ansible on Centos/RHEL
