Unit Mission: Start the Same System Twice

A repeatable startup should produce the intended system from a clean shell more than once.

Round 1

Open a clean terminal:

source /opt/ros/jazzy/setup.bash
source ~/ros2_ws/install/local_setup.bash
ros2 launch robotnix_pubsub student_system.launch.py

Collect:

ros2 node list
ros2 topic list -t
ros2 topic info <your_topic> --verbose

Save the evidence.

Stop the launch cleanly.

Round 2

Close/reopen the terminal or use another clean terminal. Repeat the same source + launch sequence.

Collect the same evidence.

Compare

Your artifact should show that the important architecture is reproduced:

• same intended nodes;
• same resolved names/namespaces;
• same topic type;
• expected publisher/subscriber endpoints;
• same configured parameter values if used.

Defense

Explain:

1. Which decisions live in node source code?
2. Which decisions live in the launch file?
3. Which decisions live in the shell environment?
4. Which evidence proves the actual runtime graph matched the launch intent?

If you can reproduce and explain the system, you are ready for the final troubleshooting/readiness Unit.