DebOps for Ansible users

This document explains certain aspects of the DebOps project to existing Ansible users.

Roles and playbooks are read-only

Current Ansible ecosystem relies on Ansible Galaxy for role distrbution. The usual use case for Galaxy roles is either as examples to write your own roles, or to heavily modify them according to your own needs.

DebOps roles and provided playbooks are designed to be used in a "read-only" mode. This allows easy upgrades of the project codebase by using the git pull command, as well as distributed development model where changes and new features can be shared between DebOps users through the central repository. You are not expected to have to modify roles directly; any and all changes necessary should be supported by the role default variables which can then be modified as needed through Ansible inventory.

Many roles support usage as "role dependencies" - other roles, either those in DebOps or written by its users, can request certain configuration to be defined on their behalf. This design principle allows for the DebOps roles to be focused on specific services or applications, and encourages re-use of existing roles when writing custom ones by users. For example when you write a role that deploys a web application, you don't need to worry about required firewall configuration, web server or system package upgrades; existing roles can handle that for you.

Roles and playbooks are shared between multiple inventories

The custom debops* scripts provided with DebOps support creation and management of multiple "project directories". Each project directory contains its own Ansible inventory, as well as custom playbooks, roles and other resources written for that environment. This allows easy creation of development, test and production environments that use the same set of playbooks and differ only via inventory variables.

Ansible inventory is a source of truth

DebOps roles don't modify the Ansible inventory directly, it is treated as the "source of truth" defined by the user. This means that users can provide any inventory they want to use, be it a set of static YAML files, or a dynamic inventory based on scripts and a database. Users don't even need to specifically configure things, many roles use sensible defaults to configure the host according to its environment (DNS domain name, IP addresses, number of CPU cores, amout of RAM, network interfaces, etc.). The aim is to have roles that work fine with default configuration in a typical Debian installation, with configuration tweaked to provide more security when necessary.