Preparatory Work 1

Why ROS2?

ROS2, or Robot Operating System 2, is the successor to ROS1, featuring enhanced capabilities. Simply put, ROS2 is a collection of tools and libraries that provide a standardized middleware for developing robotic applications, promoting code reuse and efficiency. ROS2 is particularly well-suited for building scalable and complex robotic systems that require robust communication, such as those with multiple sensors and actuators.

Here are some key benefits of using ROS2:

  • Code Separation: Enhanced modularity and reusability

  • Communication Tools: Simplifies interactions between subprograms

  • Tools and Libraries: Offers many ready-to-use resources

  • Language-Agnostic: Supports multiple languages, primarily Python and C++

  • Improved Performance: Better scalability, real-time capabilities, and security over ROS1

Selecting a ROS2 Distribution

ROS2 is released through distributions, which are collections of ROS2 packages and tools, on an annual basis. When starting a ROS2 project, the first decision you need to make is which distribution (or “distro”) to use. How should you choose? The key distinction to understand is that ROS2 alternates between Long-Term Support (LTS) versions, which receive 5 years of support, and non-LTS versions, which are supported for 2 years.

_images/distro.png

List of ROS2 Distributions

Non-LTS versions are primarily intended for testing new features and tools and are generally not recommended for starting new projects. Instead, LTS versions are preferred, especially one that has been released for at least a few months, to ensure stability and the availability of necessary resources. Additionally, each ROS2 distribution is adapted to work with specific operating systems, most commonly the latest Ubuntu LTS release. The official ROS2 documentation provides the End of Life (EOL) date for each version, indicating the period during which stability and maintenance are guaranteed.

_images/platform.png

Humble Hawksbill Supported Platforms

Key points to consider when choosing a distribution:

  • EOL Date: Ensure the distribution will be supported for the duration of your project

  • LTS Version: Opt for an LTS release, preferably one that has been available for several months

  • Supported Platform: Verify that the “distro” is compatible with your OS, typically Ubuntu LTS

For this course, we will use the Humble Hawksbill distribution, as it meets all of these recommendations. It is an LTS version, supported until May 2027. However, the best-supported platform for this distribution is Ubuntu 22.04 (Jammy Jellyfish), which could be a critical consideration for the course. In the next section, we will explore how to address this issue.

Why Docker?

In the previous section, we identified a potential issue with the ROS2 Humble distribution, which requires a specific operating system. In our case, the most suitable platform is Ubuntu 22.04. But how can we all work with Ubuntu on our own computers, regardless of our current setup? This is where Docker comes in.

Docker is a platform that allows you to package and run applications in isolated environments called containers. It ensures that the software behaves consistently, no matter where it is run, by providing everything the application needs, including the OS, libraries, and dependencies.

But how does Docker achieve this?

  • Docker Image: An image is essentially a blueprint for a container. It contains the necessary software, dependencies, and system configurations. Think of it as a snapshot of a specific environment, such as Ubuntu 22.04 with ROS2 pre-installed. When you want to run an application, Docker uses this image to create a container.

  • Docker Container: A container is an instance of an image. It is a lightweight, isolated environment where your application runs. The container shares the OS kernel with your host machine but remains isolated in terms of processes, file system, and network settings. This ensures that the container runs in a clean, consistent environment without interfering with your local setup.

In conclusion, Docker allows us to work in a clean, reproducible environment perfectly suited for our ROS2 application. For easier management, we willl use Docker Desktop, which provides a more user-friendly interface for handling containers.

In the next section, you will see the steps needed to access an Ubuntu desktop directly from your browser using Docker.

Installing Docker Desktop

Warning

Before starting the installation, make sure you have enough disk space. The full setup (Docker Desktop + Docker image) will require approximately 10GB of storage, so check your available space before proceeding.

  1. Install Docker Desktop

    Follow the instructions for installing Docker Desktop based on your operating system:

    Need help?

    If you encounter any issues during installation, please do not hesitate to contact us.

  2. Configure Docker

    Once the installation is complete, Accept the Subscription Service Agreement to proceed. You can then skip all the following questions, as creating an account is optional and not required.

  3. Pull the Docker Image

    On the Docker Desktop, use the search bar to find the image named luky005/ros2_basics and pull it.

    _images/step1.png

    Open the search bar

    _images/step2.png

    Find and pull the image

  4. Locate the Image and Run the Container

    Once the image is downloaded, find it in the Images section on the left sidebar. Then, start the container by clicking the ▶ symbol.

    _images/step3.png

    Locate and run the image

  5. Set Optional Settings and Launch the Container

    Open the Optional settings tab and fill in the following fields:

    1. Set the container name to ros2_basics

    2. Set the port to 6080

    Then, click the Run button to launch the container.

    _images/step4.png

    Open the optional settings

    _images/step5.png

    Set the settings and run

  6. Access Ubuntu

    After the container has launched, you can access Ubuntu in your preferred browser at http://localhost:6080, or you can directly access the port through Docker Desktop.

    _images/step6.png

    Access the port directly from Docker Desktop

    Warning

    Running the container in Safari may result in slower performance. For a smoother experience, we recommend using Firefox or Google Chrome.

  7. Connect to Your Desktop

    Finally, click on Connect to access your new desktop for these lab sessions.

    _images/step7.png

    Connect to Ubuntu desktop

    _images/step8.png

    Ubuntu MATE 22.04 desktop

    Important

    If you are logged out of the Ubuntu desktop due to inactivity, the following login information may be helpful: Username: ubuntu | Password: ubuntu

  8. Exit and Stop the Container

    Once you have finished working in the environment, be sure to disconnect from the VNC server and stop the container in Docker Desktop.

    _images/step9.png

    Disconnect from the VNC server

    _images/step10.png

    Stop the container

Important

To access the Ubuntu desktop in the future, navigate to the Containers section on the left sidebar. Click the ▶ symbol next to your container to start it directly.

_images/step11.png

Locate and run the container

Additionally, you can open your browser directly to http://localhost:6080 by clicking on the 6080:80 port located on the left side of the ▶ symbol. This allows you to quickly connect to the VNC server.

_images/step12.png

Access the port directly from Docker Desktop

Exploring Tools

In the container you just installed, we have preconfigured an Ubuntu environment with the ROS2 Humble distribution, along with several essential tools. On the desktop, you will find Firefox, Sublime Text, and Terminator. Below is a brief overview of each application:

  • Firefox: This web browser will enable you to access online resources, including the ROS2 Basics documentation.

    Tip

    We recommend using Firefox within the Ubuntu desktop for easier copying and pasting of code snippets from the documentation. If you need to copy from outside the Docker container, use the clipboard option in the noVNC menu on the left side of the desktop window.

    _images/clipboard.png

    Clipboard option in the noVNC menu

  • Sublime Text: This lightweight text editor is the recommended choice for writing code in this course, as its stability in the Docker environment has been proven.

  • Terminator: This enhanced terminal emulator allows you to split your screen and manage multiple terminal sessions simultaneously. This feature is especially useful when working with ROS2, as you will see in session 1.

    Here are some useful shortcuts for splitting the terminal:

    • Ctrl+Shift+O: Horizontal split

    • Ctrl+Shift+E: Vertical split

    You can also right-click on the Terminator window to access similar options for splitting the terminal.

    Additionally, here are some key shortcuts that will be especially handy while working in an Ubuntu terminal:

    • Ctrl+Shift+C: Copy

    • Ctrl+Shift+V: Paste

    • Ctrl+C: Kill current process

    • tab: Autocomplete

    • tab+tab: Show autocomplete suggestions

    • ▲ or ▼: Scroll through command history

Note

If you prefer using different tools, you are welcome to download and install them on your desktop. Customize your workspace to suit your preferences and workflow!

Learning Basic Linux Commands

As we prepare for our practical lab sessions with ROS2, being familiar with the terminal will be helpful. Here are some key Linux commands you will find useful throughout this course:

Essential Commands

  • mkdir <directory>: Create a new directory

  • cd <directory>: Change the current directory

  • ls: List directory contents

  • touch <file>: Create an empty file

  • chmod +x <file>: Make a file executable

Useful Commands

  • pwd: Display the full path of the current working directory

  • cat <file>: Display file contents

  • nano <file>: Basic text editor for editing files

  • cp <source> <destination>: Copy files or directories

  • mv <source> <destination>: Move and/or rename files or directories

  • rm <file>: Delete files

  • rmdir <directory>: Remove an empty directory

  • rm -r <directory>: Recursively delete directories and contents

Note

For more information on the Linux commands, refer to the official Ubuntu tutorial. At the very least, we highly recommend reviewing the following page to get familiar with the cd command and learn how to easily navigate between directories.

To reinforce your understanding of these commands, we invite you to participate in a command-line challenge designed to practice your skills!

Command-Line Challenge

Objective

Explore a virtual file system and complete tasks using the commands you have learned.

Instructions

  1. Setup the Challenge Environment

    Open your terminal and create a challenge directory:

    mkdir command_challenge
cd command_challenge

    Inside command_challenge, create a basic structure:

    mkdir -p challenge/{documents,images,videos}
touch challenge/documents/{notes.txt,tasklist.txt}
touch challenge/images/{pic1.jpg,pic2.jpg}
touch challenge/videos/video1.mp4

  2. Starting the challenge

    You are now in the command_challenge directory. Your objective is to complete the following tasks using your knowledge of Linux commands. Before reviewing the solutions, try to figure out the necessary commands on your own. Good luck!

Tip

Before and after each command, use ls to observe the changes in your directory.

Tasks

  • Task 1
  • Solution 1

Navigate to the documents directory

cd challenge/documents
  • Task 2
  • Solution 2

List the contents of the documents directory

ls
  • Task 3
  • Solution 3

Create a new text file called summary.txt

touch summary.txt
  • Task 4
  • Solution 4

Write a brief summary text in summary.txt, then save and exit

nano summary.txt

Example content: “This is a summary text.”

To save, press: Ctrl + S

To exit, press: Ctrl + X

  • Task 5
  • Solution 5

Display the contents of summary.txt

cat summary.txt
  • Task 6
  • Solution 6

Return to the main challenge directory

cd ..
  • Task 7
  • Solution 7

Check the full path of your current working directory

pwd
  • Task 8
  • Solution 8

Navigate to the images directory

cd images
  • Task 9
  • Solution 9

Remove pic2.jpg

rm pic2.jpg
  • Task 10
  • Solution 10

Go back to the challenge directory and remove the videos directory

cd .. && rm -r videos
  • Task 11
  • Solution 11

Copy pic1.jpg from the images directory to the challenge directory

cd images/ && cp pic1.jpg ..
  • Task 12
  • Solution 12

Rename pic1.jpg to my_pic.jpg in the challenge directory

cd .. && mv pic1.jpg my_pic.jpg
  • Task 13
  • Solution 13

Change the permissions of my_pic.jpg to make it executable

chmod +x my_pic.jpg
  • Task 14
  • Solution 14

Clean up your challenge by correctly removing the command_challenge directory

cd ../.. && rm -r command_challenge