A powerful DevOps tool: Ansible

Ansible is a radically simple IT automation platform that makes your applications and systems easier to deploy. Avoid writing scripts or custom code to deploy and update your applications— automate in a language that approaches plain English, using SSH, with no agents to install on remote systems.

http://ansible.com/

At the Openstack Summit in Vancouver I attended a great session presented by two Cisco colleagues:

Juergen Brendel (@brendelconsult), David Lapsey (@devlaps) both from Cisco Metacloud.

These are my notes, that you could find useful as a easy introduction.

But I suggest you to watch the recording of their session at the end of this post, because it is very educational.

Configuration Management tools

They are better than scripts, that in turn are better than written manual instructions, that are better than a seasoned administrator's memory.

CM tools describe the desired state of a resource (i.e. a server) via assertions (ensure that… exists/installed/...): a declarative way to provision resources.
Comparison of existing tools:

puppet dates 2005, chef dates 2009 - they are powerful and rich

salt dates 2011, ansible dates 2012 - they are easy and quick

Ansible

It's written in Python, uses YAML to create Playbooks (description of the desired state)

It's simple: no central server to maintain, no keys management, NO AGENT on the managed servers - but requires ssh and python on the target server (powershell support is coming).

Ansible executes commands in explicit order (so there are no race conditions due to dependencies).

Modules

Modules are pieces of code that do a single thing.

There are hundreds of modules available to reuse.

They’re copied to the target server at runtime, executed there (they return results) and then deleted.

Inventory file

It defines hosts and groups them so that you can apply same commands to all at once.

Adhoc commands apply to groups - example: ansible -i hosts europe -a “uname -a", where europe is a group.

Playbooks

they are written in YAML and tell Ansible what to do (a sequence of tasks)

Projects layout

A Ansible project is made of:
config files

inventory files

group variables

yaml file

Roles

contains tasks, handlers, templates, files, vars

apply to servers (that have the same role)

can be included in playbooks

Usage of API

to manage infrastructure and services

there are modules available for public cloud and private cloud management systems

Vagrant

Vagrant is a tool that matches Ansible very well:
it is used to create VM in cloud

it can use Ansible as a provisioner

written in Ruby

commands:

vagrant up - creates the vm

vagrant provision - calls Ansible

Takeaways

A single Ansible playbook can be used to deploy apps locally and in the cloud

Download Ansible for free from Github.