To participate in the VRX competition, teams must create a Docker image that runs their virtual autonomous system. This tutorial outlines the steps required to produce this image.

A Docker image is an executable package that includes everything needed to run an application--the code, a runtime, libraries, environment variables, and configuration files. A Docker container is a runtime instance of an image.

To learn more about what Docker images and containers are, Docker has excellent tutorials and explanations.

The VRX competition relies on Docker as a component of its automated evaluation system. After we receive submissions, we simulate the competition by running each submitted containers concurrently with a separate container that simulates the task environments. This has a number of advantages:

• Teams have much greater control of their execution environment.
• Docker creates an abstraction layer between submitted solutions and the host system where they will be evaluated:
  • Teams don't have to know the details of the host system to ensure their software runs correctly.
  • Likewise, the organizers don't have to know the details of the container environment.

• Docker is required to create a Dockerhub image. Please follow the VRX Docker install tutorial and the Nvidia Docker install tutorial if you are using an Nvidia GPU.

• Create a Dockerhub account here if you do not already have one. Take note of your username.

• From here, there are two main options to create your Docker image. The first option is simpler and more intuitive for first-time Docker users. The second option is cleaner and less prone to error, but is more advanced.

• Run docker run --name my_container -it ros:noetic-ros-base. This will pull the ros:noetic-ros-base image from DockerHub and create a container of that image called my_container. -it` is added so that when this is complete, it starts an interactive Bash session for you to run commands. This may take a few minutes to run.

• This Bash session is very barebones. It does not have a text editor yet, so we will install one now. From the created interactive Bash session, run apt-get update && apt-get install -y nano or replace nano with your text editor of choice.

• Use the text editor to edit ros_entrypoint.sh. Eg. nano /ros_entrypoint.sh. This is a script that is run immediately after your container has been built. Replace all the text with the following:

#!/bin/bash
set -e

# setup ros environment
source "/opt/ros/$ROS_DISTRO/setup.bash"

/run_my_system.bash

This will run the script run_my_system.bash.

• Create the run_my_system.bash script. nano /run_my_system.bash. Copy the following text into the file

#!/bin/bash

# Create ros master if not already started
rostopic list > /dev/null 2>&1
retVal=$?
if [ $retVal -ne 0 ]; then
    roscore &
    echo "Wait for 5s to allow rosmaster to start"
    sleep 5s
else
    echo "rosmaster already setup"
fi

# Send forward command
RATE=1
CMD=2
echo "Sending forward command"
rostopic pub /wamv/thrusters/left_thrust_cmd std_msgs/Float32 -r ${RATE} -- ${CMD} &
rostopic pub /wamv/thrusters/right_thrust_cmd std_msgs/Float32 -r ${RATE} -- ${CMD}

• Run chmod +x /run_my_system.bash to make it executable.

• Run /run_my_system.bash & to execute the script in the background. You should see the ros core service start up, and the output of the echo message, "Sending forward command data", from the script you just created.

• Hit enter to get back to a command prompt and run rostopic echo /wamv/thrusters/left_thrust_cmd to test that your script is publishing data as expected. You should receive /wamv/thrusters/left_thrust_cmd data (which is set to 2.0 in the script).

• Run exit to leave this container.

• Run docker ps -a to list all containers. You should see your container my_container.

• Copy the Container ID of my_container.

• Run docker commit -m "Start off ros-noetic-base, add run_my_system simple script" -a "<FULL NAME>" <Container_ID> <USERNAME>/<IMAGE_REPOSITORY_NAME>:<TAG>. Your username must match the username of your Dockerhub account. The image repository name is the repository name that the image will be saved to on Dockerhub. The tag and colon are optional (but highly recommended) to help you version your images. Example: docker commit -m "Start off ros-melodic-base, add run_my_system simple script" -a "Tyler Lum" a0e1e92cb6a5 tylerlum/vrx-competitor-example:v2.2019 or docker commit -m "Start off ros-melodic-base, add run_my_system simple script" -a "Tyler Lum" a0e1e92cb6a5 tylerlum/vrx-competitor-example

• Run docker login

• Run docker push <USERNAME>/<IMAGE_REPOSITORY_NAME>:<TAG> with the same information as the previous step. Eg. docker push tylerlum/vrx-competitor-example:v2.2019

• You should be able to log onto your Dockerhub account and see your new repository.

• Optional: If you want to keep your repository private, you can click on your repository, then click Settings, then Make Private. To ensure that your Docker image can be evaluated, you can click Collaborators and add the desired Docker ID. Exact details about submission and Docker ID are coming soon.

• Run mkdir ~/my_vrx_docker; cd ~/my_vrx_docker

• Run gedit Dockerfile and copy the following text into it:

# This is an auto generated Dockerfile for ros:ros-base
# generated from docker_images/create_ros_image.Dockerfile.em
FROM ros:noetic-ros-base

# install ros packages
RUN apt-get update && apt-get install -y \
    ros-noetic-ros-base \
&& rm -rf /var/lib/apt/lists/*

# Copy over script to Docker container
COPY ./run_my_system.bash /

# Use your ros_entrypoint
COPY ./ros_entrypoint.sh /

• Run gedit run_my_system.sh to create your script. Copy the following text into the file

#!/bin/bash

# Create ros master if not already started
rostopic list > /dev/null 2>&1
retVal=$?
if [ $retVal -ne 0 ]; then
    roscore &
    echo "Wait for 5s to allow rosmaster to start"
    sleep 5s
else
    echo "rosmaster already setup"
fi

# Send forward command
RATE=1
CMD=2
echo "Sending forward command"
rostopic pub /left_thrust_cmd std_msgs/Float32 -r ${RATE} -- ${CMD} &
rostopic pub /right_thrust_cmd std_msgs/Float32 -r ${RATE} -- ${CMD}

Then run chmod +x run_my_system.bash to make it executable.

• Run gedit ros_entrypoint.sh to create your script. Copy the following text into the file

#!/bin/bash
set -e

# setup ros environment
source "/opt/ros/$ROS_DISTRO/setup.bash"

/run_my_system.bash

Then run chmod +x ros_entrypoint.sh to make it executable.

• Run docker build --tag <USERNAME>/<IMAGE_REPOSITORY_NAME>:<TAG> . Eg. docker build --tag tylerlum/vrx-competitor-example:v2.2019 .

• Run docker run <USERNAME>/<IMAGE_REPOSITORY_NAME>:<TAG> This will create a container with the image you created in the previous step, and then run /run_my_system.bash.

• Run docker ps -a and take note of your container id. Then run docker commit -m "Start off ros-noetic-base, add run_my_system simple script" -a "<FULL NAME>" <Container_ID> <USERNAME>/<IMAGE_REPOSITORY_NAME>:<TAG>. Your username must match the username of your Dockerhub account. The image repository name is the repository name that the image will be saved to on Dockerhub. The tag and colon are optional to help you version your images. Example: docker commit -m "Start off ros-noetic-base, add run_my_system simple script" -a "Tyler Lum" a0e1e92cb6a5 tylerlum/vrx-competitor-example:v2.2019 or docker commit -m "Start off ros-noetic-base, add run_my_system simple script" -a "Tyler Lum" a0e1e92cb6a5 tylerlum/vrx-competitor-example

• Run docker login

• Run docker push <USERNAME>/<IMAGE_REPOSITORY_NAME>:<TAG> with the same information as the previous step. Eg. docker push tylerlum/vrx-competitor-example:v2.2019

• You should be able to log onto your Dockerhub account and see your new repository.

• Optional: If you want to keep your repository private, you can click on your repository, then click Settings, then Make Private. To ensure that your Docker image can be evaluated, you can click Collaborators and add the desired Docker ID. Exact details about submission and Docker ID are coming soon.

To see what is inside of your container, you can run:

docker run --name my_container <USERNAME>/<IMAGE_REPOSITORY_NAME>:<TAG>

Then in a different terminal, you can run:

docker exec -it my_container bash

This allows you to enter the running container and investigate:

source /opt/ros/noetic/setup.bash
rostopic list

/left_thrust_cmd
/right_thrust_cmd
/rosout
/rosout_agg

rostopic echo /left_thrust_cmd

data: 2.0
---
data: 2.0
---

You can exit with

exit

To kill the container from outside the container, you can run:

docker kill my_container