ROS Kick Off

This chapter describes the avenues available for learning about and getting help with ROS, as well as how to get started by setting up and installing ROS.

Resources

The most up to date information about ROS can be found on the web. There are a myriad of resources on-line to help you out in your educational or practical journey. One thing to keep in mind is that ROS, like most software, has different versions, and the format and structure of commands and API calls may differ slightly between versions (although the developers try to keep things as stable as possible). This book is specifically written for ROS 2, Eloquent Elusor, or ROS Eloquent to be terse.

While newer or older versions of ROS 2 will be generally similar, it is worth paying attention to the distribution name or version number as there are changes between versions. A major version of ROS 2 generally corresponds to a distribution, denoted by a pair of matching letter adjectives and specific nouns related to specific genus and species of turtles (e.g. Eloquent Elusor, or Foxy Fitzroy). It is worth noting that ROS versions are usually pegged to specific version of Ubuntu Linux.

ROS grew up with the modern web, and as such it has a variety of resources and forums to help you solve problems and learn about the API and tools. Some of our web resources actually pre-date more widely used systems, so it helps to know where they are and how to use them. Probably the most important resource on the web for ROS users is answers.ros.org. Answers is a Q&A website similar to StackOverflow. Once you register for Answers you can ask or answer any ROS-related question. Be aware that asking a question well can be difficult. You should include as much information as possible to help others answer your question. This means you should include the ROS version, platform version, any debugging or stack trace information you have, and the offending source code.

Aside from ROS Answers you should check out both the ROS 2 tutorials and API documentation, and the ROS 1 wiki. The ROS 1 wiki can be found at wiki.ros.org. While it is specifically dedicated to ROS 1, much of the information is still relevant to ROS 2. If you are searching for up to date ROS 2 information, your go to source is the ROS 2 tutorials and API documents located at index.ros.org/doc/ros2. Many of the tutorials you will find in this book pull directly from this body of work. If you would like to find the latest ROS news and discuss various ROS features, the ROS Discourse forum at discourse.ros.org is your best bet. ROS discourse is the community hub where developers discuss their latest projects and debate the finer points of ROS development.

For ROS application developers there are a number of tools to help you connect with the broader ROS developer community. Open Robotics supports index.ros.org, which is an extended list of ROS packages sorted by version. If you are searching for a ROS driver for a particular piece of hardware, then the index is a great place to start. If you find a package with failing tests, or would like to know the build status of any ROS package, take a look at build.ros.org. Similarly, for un-indexed packages GitHub maintains a ROS code tag. This tag will allow you to search all of the tagged repositories that are publicly listed. At the time of writing there were close to 4000 repositories listed on GitHub, so there is a pretty good chance you'll find what you need.

Finally, there are a variety of unofficial resources that you should be aware of that can be useful, particularly if you want to keep yourself up to date with the latest ROS projects and features. Both Open Robotics and ROS maintain twitter feeds to share the latest news. We also have a yearly ROS developers conference called ROSCon; most talks are freely available on the web. There are a few other resources that can also be useful including the ROS subreddit and an "unofficial" ROS Discord.

Setting Up Your Computer

For this chapter we assume that you are working on a modern desktop with a discrete graphics card. While a graphics card isn't necessary for this chapter, later chapters will be graphics intensive and having one will greatly improve the end user experience. Moreover, this book assumes you are working with the Ubuntu Linux 18.04 operating system. While other operating systems are supported by ROS 2, all of the tutorials and instructions on this book assume you are running Linux. If instead you're using a Mac or Windows PC, you can install ROS 2 Eloquent Elusor using the instructions found on the ROS 2 installation instructions page. An alternative path for installation on Mac and PC is to using a virtual machine. Roughly the process for doing so is as follows:

Install virtual machine software like Virtual Box or VMWare on your host machine.
Create a virtual machine using the software, and install Desktop Ubuntu 18.04 Bionic Beaver from the Canonical website. Configure the installation as you wish.
Now start your virtual machine and log in as a user. The directions below should be applicable.

For these initial tutorials we will be working with the pre-compiled ROS 2: Eloquent Elusor desktop version. These directions follow directly from the installation instructions found on the [Eloquent installation page]https://index.ros.org/doc/ros2/Installation/Eloquent/Linux-Install-Debians/). To run these commands you'll need a terminal window. To open a terminal in Ubuntu 18.04 click on the nine dots in the bottom left hand of the screen. A dialog should appear. Enter the word terminal and click on the terminal icon to open a terminal. Alternatively, you can press the control, alt, and 't' keys simultaneously to open a terminal (we abbreviate this CTRL-ALT-T).

Setup Locale

The first step is to make sure you have a locale which supports UTF-8. What this means is that we will check that the language used by your computer uses a particular format of text. If you are in a minimal environment, such as a Docker container, the locale may be something minimal like POSIX. We test with the following settings. It should be fine if you're using a different UTF-8 supported locale.

sudo locale-gen en_US en_US.UTF-8
sudo update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8
export LANG=en_US.UTF-8

Setup Sources

You will need to add the ROS 2 apt repositories to your system. Out of the box Ubuntu doesn't know where the ROS 2 binary programs live so we have to give it a secure location. To do this the computer will prompt you for your root password. For more technical readers we need to authorize the ROS GPG key with apt by typing the following command in the terminal:

sudo apt update && sudo apt install curl gnupg2 lsb-release
curl -s https://raw.githubusercontent.com/ros/rosdistro/master/ros.asc | sudo apt-key add -

Install ROS 2 Packages

The next steps for installing ROS is to do a system update (i.e. check for newer programs) and then install ROS Eloquent. To do this we run the following commands. Be aware that these commands will download a lot of data and may take awhile. It is best to run these commands on your home network.

sudo apt update

Desktop Install (Recommended): ROS, RViz, demos, tutorials.

sudo apt install ros-eloquent-desktop

Next we'll install a set of tutorials called TurtleSim. To do this we run another apt command.

sudo apt install ros-eloquent-turtlesim

ROS 2 command line tools use argcomplete for autocompletion. If you want autocompletion, installing argcomplete is necessary. We're also going to install a few other tools to make our lives easier.

sudo apt install python3-argcomplete htop byobu

Check Your Installation

ROS uses environment variables to help keep track of what version of ROS is running and where all the programs using ROS are on the computer. To set these environment variables we source, or load, a bash script file. A bash script file isn't magic; it is a series of commands to enter into the terminal, just like the series of commands we just entered to setup ROS. It is possible to have different versions of ROS running on a single computer. Using the wrong version of ROS can lead to all sorts of problems and is a common mistake for new users! If you are having problems, try sourcing the correct ROS bash file. From now on, whenever you open a new terminal, you will need to tell the computer which version of ROS to use. To set the necessary environment variables for ROS you need to source a bash file every time you open a new terminal. Yes, this is annoying, but it is a sound approach as it makes the version of ROS you are using explicit. On Ubuntu 18.04 all versions of ROS live in /opt/ros/. Inside this directory will be a programs and scripts file to run ROS. To tell the operating system that we want to use ROS Eloquent we simply source the ROS Eloquent setup.bash file using the command below:

source /opt/ros/eloquent/setup.bash

Once that command runs, your terminal should be ready to run a ROS program. Let's test our installation by running two small ROS programs called talker and listener. These two programs will send data back and forth using ROS to perform the communication. One program was written in C++ and the other in Python. Running these two different programs is a quick and easy way to check that your ROS system is configured correctly. To start the talker run the following command:

source /opt/ros/eloquent/setup.bash
ros2 run demo_nodes_cpp talker

If everything is working correctly you should see something like the following:

[INFO] [talker]: Publishing: 'Hello World: 1'
[INFO] [talker]: Publishing: 'Hello World: 2'
[INFO] [talker]: Publishing: 'Hello World: 3'
....

Now, let's fire up the listener. We're going to use a Python listener in this example to make sure we installed Python correctly. First we will need a second terminal. We can open a new terminal tab by entering CTRL-SHIFT-T in our terminal. We can also create a wholly new terminal by pressing CTRL-ALT-T. Pick whatever works best for you. Now in your new terminal source your bash file and run the following command:

source /opt/ros/eloquent/setup.bash
ros2 run demo_nodes_py listener