What is Ansible?

Ansible: Automation for sysadmins

Ansible allows automation and configuration management for numerous hosts.

In details

It’s a simple automation language that can perfectly describe an IT application infrastructure in Ansible Playbooks. It’s an automation engine that runs Ansible Playbooks Playbooks are Ansible’s configuration, deployment, and orchestration language. They can describe a policy you want your remote systems to enforce, or a set of steps in a general IT process. At a basic level, playbooks can be used to manage configurations of and deployments to remote machines. At a more advanced level, they can sequence multi-tier rollouts involving rolling updates, and can delegate actions to other hosts, interacting with monitoring servers and load balancers along the way.

Ansilbe’s architecture is very straight forward

modules, roles, and playbooks: telling ansible what to do

Modules and playbooks are the actually code that gets run on different hosts

If Ansible modules are the tools in your workshop, playbooks are your instruction manuals, and your inventory of hosts are your raw material.

-Ansible documentation

Running playbooks

ansible-playbook playbook.yml
						

Running one off commands

$ansible localhost -m ping
$ansible localhost -a ls
						

Roles: DRY(Don't repeat yourself)

site.yml
webservers.yml
roles/
	role1/
		files/
		templates/
		tasks/
		handlers/
		vars/
		defaults/
		meta/
						

Use Case Example 1: Installing new software my servers

We need to install the package "nginx" on all of our servers

We can do this by running:

$ansible all -s -m shell -a 'apt-get install nginx'
						

We have just ran a task. Ansible also allows combining different tasks into a taskfile, which will itself be part of a "Role". A Role will have the taskfile and all its related files. (more on this later)

However, we could probably have done the same thing with a bash script. What sets ansible apart is the ability to ensure idempotence (same final result).

Running the code below will also install nginx on all of our servers

ansible all -s -m apt -a
'pkg=nginx state=installed update_cache=true'
						

The response will be:

127.0.0.1 | success >>
{
"changed": false
}
						

Note that this will also ensure idempotence. Note that we used the ansible module 'apt' to accomplish this. Modules are an essential part of ansible.

Use Case Example 2: Adding a database to our servers

We can write the following taskfile for our "createDB" role:

Recall that the structure of a role looks like this:

When we run the role, Ansible will automatically run the "main.yml" taskfile in that role.

To run our role, we need to create a playbook file which calls our role, running our taskfile.

Playbook files are in the .yml format, and can call multiple roles. Here is one which will call our "createDB" role. Assume that the following playbook file is "DBplaybook.yml"

We now simply run:

ansible-playbook DBplaybook.yml

And the database will be set up on all of our servers!

Other use cases

-Adding users to databases

-Managing services on servers

-Deploying applications to servers

-Running application scripts on servers

Ansible: Is it right for you?

The competitors of Ansible include:

• Puppet
• Chef
• SaltStack
• Terraform
• CloudFormation

Ansible users write playbooks in a descriptive language similar to YAML and Jinja. Users may prefer to use a competitor that uses a language they know, or that is coded in a more procedural style. For example, Terraform uses Go, and Puppet uses Ruby.

Ansible is often preferred because it uses client-only architecture. Many of its competitors, including Chef, SaltStack, and Puppet, use client-server architecture. However, there are two competitors, CloudFormation and Terraform, that also offer client-only architecture. Ansible is flexible and can be used either as push-based or pull-based system.

Ansible was first written for use in command line only. Unfortunately, this remains relevant, because the majority of functionality available in the command line is not available from the user interface.

Ansible is one of the newer configuration management tools, and some of its more established competitors, like Chef, offer greater stability. Chef and Puppet users will benefit from a larger user and developer communities.

Ansible nodes are managed by default over SSH. SSH communication can face reduced speed in a scaled or downsized environment. Furthermore, although Ansible uses an agentless architecture, machines must have a Python interpreter installed and require root SSH access for most functionality.

Example/tutorial 1: Localhost

Dependencies

• Ansible

Ad Hoc commands: Pinging the localhost

#this uses the module 'ping' on localhost
$ansible localhost -m ping
						

Ad Hoc commands: running shell commands

#this allows a single command to be run
$ansible localhost -a 'ls -al'
						

Making a playbook

---
# test-playbook.yml
- hosts: localhost
  tasks:
    - name: list homedir
      shell: ls
    - name: make ~/temp or update access time
      shell: touch temp
    - name: fail to make or update /tmp
      shell: touch tmp
      args:
        chdir: /
						

Running our playbook

ansible-playbook test-playbook.yml
						

The command failed. Can you fix it

Example/tutorial 2: docker/ansible-container

Ansible container allows you to configure and automate your containers in a sane manner that doesn't require bash scripts, and uses ansible playbooks. yay!

Dependencies

Ansible-container is not included in Ansible. You'll need to install it here

Basic example

Make a new directory and cd into it then run:

$ansible-container init
$ansible-container build
$ansible-container run
						

Example/tutorial 3: vagrant