Unit 3 — Turtlesim and the ROS Graph

You have ROS 2 running. Now stop treating it like a pile of terminal commands.

This Unit teaches you to look at a live ROS system.

PACKAGE
  ↓ provides
EXECUTABLE
  ↓ starts
NODE
  ↓ participates in
ROS GRAPH

Turtlesim is intentionally small. You can see the turtle move while ROS 2 exposes the software structure behind that movement.

Lessons

1. Start Turtlesim and Prove the Package Exists
2. ros2 run: Package, Executable, Node
3. Discover Nodes With ros2 node list
4. Interrogate a Node With ros2 node info
5. See the Graph With rqt_graph
6. Names, Namespaces, and Remapping
7. Run Reusable Nodes More Than Once
8. Unit Mission: Map the Running System

Unit artifact

An annotated live-system map that identifies the nodes you ran, the commands that started them, at least one connection between them, and one before/after change caused by remapping or renaming.

Source attribution: adapted from the ROS 2 Jazzy beginner CLI documentation in Gh0stlyKn1ght/ros2_documentation, CC BY 4.0.