Merge pull request #18 from dj4ngo/feature/what-is-ansible

issue #7 - whats ansible

_drafts/contribute-to-ansible.markdown

@@ -32,9 +32,36 @@ Ansible unit and integration tests have parts also based on docker.
 For your information, this is a very interesting part to contribute on Ansible.
 
 ## What's Ansible?
-    Principe de fonctionnement
-    petit exemple d'installation d'un paquet (liens vers le site officiel de ansible)
-    Différencier serveur de client (machine hote ou cible) retrouve rles vrais termes ansible
+
+If you are reading this article, you should propably be already familiar with Ansible... So if you're not reading it, we'll explain it quickly ...
+
+Ansible is a simple IT automation engine. It is designed to easily configure several servers. It's a really good devOps partner to automate quickly and easily a CI/CD for example. Ansible have a lot of plugins which are used to manage almost everything in a server, network device, storage bay.... It is easy-to-use; all the configuration ans playbooks are simple yaml files and it doesn't need any agent on managed nodes. Ansible requires only an SSH connection and python installed on the manages server. In fact, that's not really true since Ansibe can manage windows nodes using the powershell distant connexion. It is fair to say that we will cover only the Linux use cases in this article. Ansible force lie in the capability to easily configure a lot of devices and guaranty that the configuration is consistent in all targets regardless the initial state. How is it done ? The concept behind an Ansible module is to be re-enterable!
+
+Ansible have severals competitors like, [Chef](https://www.chef.io/chef/), [Puppet](https://puppet.com/), [Saltstack](https://saltstack.com/), [Fabric](https://fabric.io) or others. Why did we choose Ansible? As we said previously, it is easy to use, and don't need agent. It is fully coded in python which is a language we appreciate and, on top of that, we are using it professionnaly every days and are really happy with it, of course. 
+
+OK, that sounds great, but what's the price? Ansible is an open-source project which have a growing community and it is really easy to use, so it won't costs many times (it will even save so much !) and it's fully free (you can have some support on some modules for profesionnal purposes regarding your use cases).
+
+
+
+#### Let's see main principles :
+
+We will just define few glossary terms before:
+There are two kinds of machines used during an Ansible deployment:
+  - Ansible is executed on a server host called `controller`
+  - The servers/devices managed by Ansible are called `managed nodes`
+Complete glossary is available [here](http://docs.ansible.com/ansible/latest/glossary.html) if you need it.
+
+Ansible uses an [inventory](http://docs.ansible.com/ansible/latest/intro_inventory.html)  which defines all managed nodes access in a simple (or multiples) YAML file. Ansible is using SSH to manage nodes. It can deal with a password or key authentication and is able to elevate privileges using su, sudo [or several others](http://docs.ansible.com/ansible/latest/become.html). You can even use an SSH bastion by simply using ssh args variables or your `ssh_config` file. This can address almost cases.
+
+To define what to perform on managed nodes you must creates playbook. This is still YAML files. You can find some documentation about playbooks [here](http://docs.ansible.com/ansible/latest/playbooks.html). To avoid having code duplication and win some flexibility I strongly recommend you to use [playbooks roles](http://docs.ansible.com/ansible/latest/playbooks_roles.html).
+
+We recommend to follow the [best practices](http://docs.ansible.com/ansible/latest/playbooks_best_practices.html) to organize your Ansible directory layout
+
+
+Get more informations on [how it works](https://www.ansible.com/how-ansible-works) or more generaly on [Ansible official site](https://www.ansible.com/) 
+The [Ansible documentation](http://docs.ansible.com/ansible/latest/index.html) is really up-to-date, well organised and contained a lots of example. It will be a great help for you. 
+
+
 
 ## Why contribute?