Ansible

https://charlesreid1-docker.github.io/charlesreid1-ansible/

Ansible can be thought of as a for-loop over SSH scripts, but it's also much more than that. Ansible is all about taking care of the heavy lifting involved in infrastructure automation.

Basic Features

Main article: Ansible/Basics

Summary:

• Ansible is Python-based
• Ansible uses playbooks, which are YAMl files, to configure remote machines
• Ansible is push-based, which means your workflow involves making changes to the playbook and pushing those changes to the server
• Ansible is idempotent, which means you can run the playbook multiple times and it will only carry out new tasks (it will not repeat tasks)
• Ansible allows executing arbitrary shell commands
• Ansible uses Jinja templates, in addition to YAML, to deploy files to machines

Directory Structure

The basic directory structure we'll use with Ansible is to create a playbooks directory to hold everything:

playbooks/
    hosts       <-- ansible inventory file
    .vagrant/   <-- directory used by vagrant for keys/machines (if using vagrant)
    playbook.yml

See Ansible/Directory Layout for a much more detailed discussion.

Using Ansible

Using Ansible Locally with Vagrant

Main article: Ansible/Vagrant

Vagrant allows you to set up virtual machine(s) using VirtualBox, which can give you a way of testing Ansible scripts locally (without using the AWS or Google Cloud platforms).

Ansible uses the hosts file to connect to Vagrant. You can either manage the hosts file by hand (for a small number of machines), or you can use a dynamic inventory script (for an arbitrary number of machines).

See Ansible/Vagrant for coverage of both methods when using Vagrant.

See Ansible/Vagrant/Dynamic_Inventory for a dynamic inventory script with Vagrant.

Using Ansible with EC2

Main article: Ansible/EC2

When using Ansible with Amazon AWS EC2, AWS manages the compute nodes.

Like with Vagrant, Ansible uses the hosts file to connect to the EC2 nodes. The hosts file can either be maintained by hand using the information from AWS, or a dynamic inventory script can be used to call the AWS API and get information about computational resources to give to Ansible.

See Ansible/EC2 for coverage of both methods (the static inventory script and the dynamic inventory script) when using Amazon EC2.

See Ansible/EC2/Dynamic Inventory for an example EC2 dynamic inventory script.

Ansible Features

Playbooks

Playbooks are the central feature of Ansible, and are where you tell Ansible what to do on what machines.

Ansible/Playbooks - this is where Ansible becomes really powerful

Ansible/Variables - defining and using variables to remove complexity

Hosts

Ansible host files tell Ansible how to work with host machines. Ansible can also interact programmatically with hosts.

Ansible/Hosts - configuring machines to work with Ansible

Roles

Roles can provide multiple "routes" through a playbook for different types of machines

Ansible/Roles - defining and using roles to make playbooks more powerful

Vaults and Secrets

Ansible uses vaults to encrypt and store keys and secrets. You can include a vault in playbooks/group_vars and have ansible ask for a password on the command line:

ansible-playbook site.yml --ask-vault-pass

Ansible/Vaults - mechanism for encrypting and decrypting secrets