The repo provides some ROS2 cheat-sheet.

• 01. How to create packages
• 02. Publish and Subscribe
• 03. Service and Client
• 04. Action
• 05. Launch
• 06. Component
• 07. LifeCycle
• 08. Parameter: TODO
• 09. Timer: TODO
• 10. QoS: TODO
• 11. Interface

• ROS 2 domain bridge: How to bridge communication between different domains.
• RMF: The framework proposed by OR for building your own fleet management system.
• message filter example: The package shows you how to use message filter.
• topic_tools: Manipulate ROS 2 topic at a meta-level

# Topic relay: subscribe and then republish
ros2 run topic_tools relay <origin_topic> <new_topic>

• Discourse: The forum for ROS
• ROS answers
• ROS packages: Packages list for ROS
• ROS2 wiki: Wiki for ROS2
• ROS 2 Overview: Documentation for developers
• ROS 2 Design: The design behind ROS2
• ROS 2 Demo Code: Demo Code for ROS2
• ROS 2 Example Code: Example Code for ROS2
• Design of ros2 trace tool: There are some explaination of ROS2 work flow.