ROS2 systemd service launch to ROS topic

Question

We are trying to launch a ROS2 subscriber node and publisher node on boot. We are using a systemd service file to launch our launch.py file. When running systemctl status and viewing the systemctl log, we can see our nodes running and communicating. However, when we run ros2 topic list, we cannot see the topic over which the nodes are communicating. Why is this and how do we “re-route” the information from the systemctl logs to ROS2 such that we can view the topic and messages directly in ROS2?

(We confirmed that the nodes themselves work when running ros2 run <node_name>. Here is the service file:

[Unit]
Description=ROS 2 Node Launch Service

[Service]
Type=simple
Environment="HOME=root"
ExecStart=/usr/local/bin/worm7_ros2_launch.sh

[Install]
WantedBy=multi-user.target

Here is the bash file:

#!/bin/bash
source /home/worm7/worms_ws/install/setup.bash

ros2 launch startup startup.launch.py

Here is the launch file:

from launch_ros.actions import Node

def generate_launch_description():
    return LaunchDescription([
        Node(
            package='startup',
            namespace='startup',
            executable='listener',
            name='listener'
        ),
        Node(
            package='startup',
            namespace = 'startup',
            executable='talker',
            name='talker'
        )
        
    ])

The code for the publisher and subscriber nodes can be found here: https://docs.ros.org/en/iron/Tutorials/Beginner-Client-Libraries/Writing-A-Simple-Py-Publisher-And-Subscriber.html

Any help is appreciated. Thank you.

Answer 1

When running at a system process it will have a different user and environment. I would suggest making sure that you don't have any settings is places like your .bashrc file that is setting up your environment differently. Or elsewhere in your user directory or system in general.

Answer 2

There might be other ways but it sure makes things easier to specify the username in your service definition to match your default user. Otherwise the service defaults to root (and I could not get topics etc to connect). Do it like so:

[Service]
...
User=your_default_username
...