What is the best practice to start "roscore" followed by "rosrun ...." on Docker Container startup?

Question

I have created through a Dockerfile a Docker image on which Ubuntu 18.04 and ROS Melodic are properly installed. Please note that I have not used the official ROS-Docker image for creating my Docker image.

The Docker container derived from this Docker image is working fine. However, every time I want to work with the container, I need to execute the following commands:

1. Terminal window:

docker run -d -it --name container_name docker_image; docker exec -it container_name bash

Then, after I am within the Docker container: roscore

2. Terminal window:

docker exec -it container_name bash

Then, after I am within the Docker container: rosrun ROS_PackageName PythonScript.py

Please note that through the above-mentioned Docker commands, both terminals operate in the same Docker container.

I find my way to start the PythonScript.py inefficient. Therefore, I would like to ask for the best practice to start "roscore" followed by "rosrun...." on Docker Container startup.

In some Dockerfiles I see at the end of the file the command ENTRYPOINT as well as CMD . However, I do not know if these commands can help me to make my Docker container execute "roscore" followed by "rosrun" on container startup.

Answer 1

This is actually, in part, what roslaunch is for. It makes it easier to launch multiple nodes and nicer parameter input, but it will also start a roscore is one is not already running. In your example it would look something like this:

<launch>
  <node pkg="ROS_PackageName" type="PythonScript.py" name="my_node_name" output="screen" >
  </node>
</launch>