ROS is an open source software framework for programming robots and developing complex robotics applications. In addition, ROS is sometimes called a meta-operating system or middleware software framework because it performs many of the functions of an operating system, but it requires a host operating system, such as Linux.

Moreover, like any operating system, it provides a hardware abstraction layer to build robotics applications without worrying about the underlying hardware. The core of ROS is a message-passing middleware framework—synchronous or asynchronous—where processes and threads can communicate with and transport data between each other even when they are running from different machines. In addition, ROS software is organized as packages, offering good modularity and reusability, which can be integrated with and used for any custom robotic application with minimal changes.

The Robot Operating System (ROS) is a framework that is widely accepted and used in the robotics community, which ranges from researchers to professional developers of commercial robots. ROS was originally started in 2007 by the Stanford Artificial Intelligence Laboratory (SAIL) under the name SwitchYard, in support of the Stanford AI Robot project.

Since 2008, Willow Garage has been continuing the development, and recently ROS has been actively maintained by the Open Source Robotics Foundation (OSRF):

• ROS: http://www.ros.org/
• OSRF: http://www.osrfoundation.org/

Let's start with the introductory chapter of this book, where we will learn how to install ROS on various platforms.

We assume that you have a desktop system with Ubuntu 16.04 or Ubuntu 18.04 long-term support (LTS) installed, with an Intel Corei5 processor @3.2 GHz and 8GB of RAM, or similar. Furthermore, it is necessary to have a basic knowledge and understanding of Linux and command tools. If you need to refresh your memory or learn about these tools, you can find a lot of relevant resources on the internet, or you can find books on these topics instead.

In this section, we will discuss the ROS distribution and the corresponding supported operating system, which will guide help us in selecting the right combination, depending upon our requirements.

An ROS distribution is a versioned set of ROS packages. These are very similar to Linux distributions. The purpose of the ROS distributions is to let developers work against a relatively stable code base until they are ready to set up forward. Each distribution maintains a stable set of core packages up to the end of life (EOL) of the distribution.

The latest recommended ROS distribution is Kinectic Kame, which will get support up to May 2021, however, the latest ROS distribution is Melodic Morenia, which was released on 23rd May 2018, and will be supported up to May 2023. One of the problems with this latest ROS distribution is that most of the packages will not be available on it because it will take time to migrate them from the previous distribution, so we do not recommend this.

The list of distributions to use can be found on the ROS website (http://wiki.ros.org/distributions):

ROS is fully compatible with the Ubuntu operating system by design. Moreover, the ROS distributions are planned according to Ubuntu releases. Nevertheless, they are partially supported by Ubuntu ARM, Gentoo, macOS X, Arch Linux, and OpenEmbedded. The following table shows ROS distributions and the corresponding versions of the supported operating systems:

As we have discussed in the previous section, there are several ROS distributions available to download and install. Therefore, we recommend you select the LTS release, which is stable and getting maximum support.

However, if the latest features of ROS are required, you could go for the latest version, but you will not get the latest complete packages immediately after release because of the migration period from one distribution to another.

In this book, we are using two LTS distributions, ROS Kinetic and ROS Melodic, for all experiments.

The following screenshot shows a choice of ROS installations:

We can get the complete installation instructions for each distribution from the ROS website (http://www.ros.org/). Afterward, navigate to Getting Started | Install. It will show a screen listing, as shown in the preceding diagram, for the latest ROS distributions.

In the following section, we will go through the instructions for installing the latest ROS distribution.

To configure the Ubuntu repository, first search for Software & Updates in the Ubuntu Search Toolbar and enable the restricted, universe, and multiverse Ubuntu repositories, as shown in the following screenshot:

The next step is to set up the desktop system to accept software from packages.ros.org. The details of the ROS repository server have to be added into /etc/apt/source.list:

$ sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'

Whenever a new repository is added to the Ubuntu repository manager, we have to make it trusted to validate the origin of the packages by adding the keys. The following key should be added to Ubuntu before starting the installation, which will ensure the download comes from an authorized server:

$ sudo apt-key adv --keyserver hkp://ha.pool.sks-keyservers.net:80 --recv-key 421C365BD9FF1F717815A3895523BAEEB01FA116

Now, we are prepared to install the ROS packages on Ubuntu. The first step is to update the list of packages by using the following command:

$ sudo apt-get update

There are many different libraries and tools in ROS, however, we will provide four default configurations to get you started:

• Desktop-Full install (recommended):

$ sudo apt-get install ros-kinetic-desktop-full

• Desktop install:

$ sudo apt-get install ros-kinetic-desktop

• ROS-Base:

$ sudo apt-get install ros-kinetic-ros-base

• Individual Package:

$ sudo apt-get install ros-kinetic-PACKAGE

Now, we are ready to install the ROS packages on Ubuntu 18.04 LTS. The first step is to update the list of packages by using the following command:

$ sudo apt-get update

There are many different libraries and tools in ROS, however, we will provide four default configurations to get you started:

• Desktop-Full Install (recommended):

$ sudo apt-get install ros-melodic-desktop-full

• Desktop Install:

$ sudo apt-get install ros-melodic-desktop

• ROS-Base:

$ sudo apt-get install ros-melodic-ros-base

• Individual Package:

$ sudo apt-get install ros-melodic-PACKAGE

Before using ROS, you have to initialize rosdep, which enables you to easily install system dependencies for sources you want to compile, and also is required to run some core components in ROS:

$ sudo rosdep init
$ rosdep update

Good! We have completed the ROS installation. The ROS scripts and executables are mostly installed to /opt/ros/<ros_version>.

To get access to these scripts and executables, the ROS environment variables need to be added to the bash session. We have to source the following bash file for ROS Kinetic:

$ source /opt/ros/kinetic/setup.bash

ROS Melodic requires the following:

$ source /opt/ros/melodic/setup.bash

It's convenient if the ROS environment variables are automatically added to the bash session every time a new shell is launched.

For ROS Kinetic, use the following:

$ echo "source /opt/ros/kinetic/setup.bash" >> ~/.bashrc
$ source ~/.bashrc

For ROS Melodic, use the following:

echo "source /opt/ros/melodic/setup.bash" >> ~/.bashrc
source ~/.bashrc

If we have more than one ROS distribution installed, ~/.bashrc must only source setup.bash for the version we are currently using:

$ source /opt/ros/<ros_version>/setup.bash

Moreover, rosinstall is a frequently used command-line tool in ROS that is distributed separately. It enables us to easily download several source trees for the ROS packages with the single command.

This tool is based on Python, and can be installed using the following command:

$ sudo apt-get install python-rosinstall

The ROS packages are built by the ROS build farm. We can check the status of individual packages at http://repositories.ros.org/status_page/.

Congratulations! We are done with the ROS installation. We will execute the following command to check whether the installation is correct.

Open a new terminal to run roscore:

$ roscore

This is followed by a turtlesim node in another terminal:

$ rosrun turtlesim turtlesim_node

If everything is correct, we will get the following screen:

As we know, complete ROS support is only available on Ubuntu and Debian distributions. If we are Windows or macOS X users and we don't want to change the operating system of our computer to Ubuntu, we can use tools such as VMware or VirtualBox to help us to virtualize a new operating system on our computers.

VMware Workstation Pro is the industry standard for running multiple operating systems as virtual machines on a single PC. It is commercial software but also has free product trials and demos (https://www.vmware.com/in.html).

Alternatively, VirtualBox is a free and open source hypervisor for x86 computers that can be installed on several host operating systems, including Linux, macOS, Windows, Solaris, and OpenSolaris (https://www.virtualbox.org/).

Once the virtual machine starts and is configured properly, we should see another window on the host system, as seen in the following screenshot:

There is no difference in an ROS installation on a virtual machine. Therefore, we can simply install ROS Kinetic following the same instructions described in the previous section. We can run most of the examples and stacks that we are going to work with. Unfortunately, the virtual machine may have problems when working and interfacing with external custom hardware through ROS. Moreover, performance degradation could also be observed with ROS running in a virtual machine. It is possible that the example source code discussed in Chapter 4, ROS Visualization and Debugging Tools, will not work.

The following screenshot shows ROS running on one of the virtual machines and the ROS installation:

As the industry moves beyond the virtual machine consolidation paradigm, several types of containers have come into prominence. Two flavors currently enjoy the lion's share of deployments on the Linux operating system: Docker and LXC.

LXC (Linux Containers) is an OS-level virtualization technology that allows the creation and running of multiple isolated Linux virtual environments (VE) on a single control host. These isolation levels or containers can be used to either sandbox specific applications or emulate an entirely new host. LXC uses the Linux cgroups functionality, which was introduced in version 2.6.24, to allow the host CPU to better partition memory allocation into isolation levels called namespaces (https://linuxcontainers.org/).

Docker, previously called dotCloud, was started as a side project and only open sourced in 2013. It is really an extension of the LXC capabilities. This it achieved using a high-level API that provides a lightweight virtualization solution to run processes in isolation. Docker is developed in the Go language and utilizes LXC, cgroups, and the Linux kernel itself. Since it's based on LXC, a Docker container does not include a separate operating system; instead it relies on the operating system's own functionality, as provided by the underlying infrastructure. So, Docker acts as a portable container engine, packaging the application and all of its dependencies in a virtual container that can run on any Linux server (https://www.docker.com/).

Since Docker is an open platform that helps to distribute applications and complete systems and is based on LXC, we will discuss working with ROS Docker Images and how to distribute complex applications along with complete systems as a standalone image.

Before installing Docker, it will require the updated packages:

$ sudo apt-get update

Use the following command to add the GPG key for the official Docker repository to the system:

$ sudo apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D

For Ubuntu 16.04, add the following:

$ echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" | sudo tee /etc/apt/sources.list.d/docker.list

For Ubuntu 18.04, add the following:

$ echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" | sudo tee /etc/apt/sources.list.d/docker.list 

Updating the package database with the Docker packages from the newly added repository is done as follows:

$ sudo apt-get update

Make sure that we are about to install from the Docker repository instead of the default Ubuntu repository:

$ apt-cache policy docker-engine

Notice that docker-engine is not installed yet; to install docker-engine, use the following command:

$ sudo apt-get install -y docker-engine

Check whether Docker is started or not:

$ sudo systemctl status docker

To start the Docker service, use the following command:

$ sudo service docker start
$ docker

We can search for images available on Docker Hub by using the docker command with the search subcommand:

$ sudo docker search Ubuntu

To run the Docker container, use the following command:

$ sudo docker run -it hello-world

Docker images are akin to packages such as virtual machines or complete systems that are already set up. There are servers that provide the images, and users only have to download them. The main server is Docker Hub, which is located at https://hub.docker.com. Here, it is possible to search for Docker images for different systems and configurations.

Well! All ROS Docker images are listed in the official ROS repository on the web at https://hub.docker.com/_/ros/. We will use ROS Kinetic images, which are already available here:

$ sudo docker pull ros
$ sudo docker pull kinetic-ros-core 
$ sudo docker pull kinetic-ros-base
$ sudo docker pull kinetic-robot
$ sudo docker pull kinetic-perception

Similarly, we could pull ROS Melodic images, which are also already available there:

$ sudo docker pull ros
$ sudo docker pull melodic-ros-core
$ sudo docker pull melodic-ros-base
$ sudo docker pull melodic-robot
$ sudo docker pull melodic-perception

After the container is downloaded, we can run it interactively with the following command:

$ docker run -it ros

This will be like entering a session inside the Docker container. The preceding command will create a new container from the main image wherein we have a full Ubuntu system with ROS Kinetic already installed. We will be able to work as in a regular system, install additional packages, and run the ROS nodes.

We can list all the Docker containers available and the origin of their images:

$ sudo docker ps

Congratulations! We have completed the Docker installation. To set up the ROS environment inside the container in order to start using ROS, we have to run the following command (ros_version: kinetic/melodic):

$ source /opt/ros/<ros_version>/setup.bash

However, in principle, running docker should be enough, but we could even SSH into a running Docker container as a regular machine, using name or ID.

$ sudo docker attach 665b4a1e17b6 #by ID ...OR
$ sudo docker attach loving_heisenberg #by Name

If we use attach, we can use only one instance of the shell. So, if we want to open a new terminal with a new instance of a container's shell, we just need to run the following:

$ sudo docker exec -i -t 665b4a1e17b6 /bin/bash #by ID ...OR 
$ sudo docker exec -i -t loving_heisenberg /bin/bash #by Name

Moreover, Docker containers can be stopped from other terminals using docker stop, and they can also be removed with docker rm.

This book comes with a working Docker Image, which is basically an extension of ROS Kinetic with the code for the examples. The instructions to download and install it will be on the GitHub repository with the rest of the code.

There is high demand from industries that are working on commercial robotic products for ROS that runs on an embedded platform, mostly on the ARM platform. Finally, OSRF, which maintains the open source ROS, has announced its formal support for an ARM target.

There are two streams to support ROS on an ARM target:

• Ubuntu ARM

• OpenEmbedded (meta-ros)

Ubuntu ARM is the most popular among researchers since it is easy to install and a lot of ARM boards are already supporting it; a few of them are shown in the following diagram. In addition, many ROS packages are already supported or could be ported with minimal changes:

Supported platforms

However, OpenEmbedded is used by professional developers for commercial products in industries. The following table shows a comparison of both:

Despite several possibilities, we have chosen to install ROS on Ubuntu ARM because these distributions are more common and can be used on other ARM-based boards such as UDOO, ODROID-U3, ODROID-X2, or Gumstix Overo. It is recommended to use an image of Ubuntu ARM 16.04 Xenial armhf on the platform to work with ROS.

Before installing ROS on the specific ARM platform, we have to complete a few prerequisites. As this book is focused on ROS, we will list them without going into detail. However, there is a lot of information about Ubuntu ARM for specific ARM platforms available on websites, forums, and books that could be reviewed.

When we have Ubuntu ARM on our selected platform, the network interfaces must be installed to provide access to the network by configuring the network settings, such as the IP, DNS, and gateway.

An Ubuntu image for most of the ARM platform will be set up for MicroSD cards with 1-4 GB size. This is not sufficient to use a large part of the ROS Kinetic packages. In order to solve this problem, we can use SD cards with more space and expand the file system to occupy all the space available with re-partitioning:

GParted

We could use the GParted utility, an open source graphical tool that is used for creating, deleting, resizing, moving, checking, and copying disk partitions and their file systems (http://gparted.org/).

Good! We should be ready to install ROS. After this, the process of installation is pretty similar to the desktop installation discussed in the previous section. The major difference when installing ROS on the Ubuntu ARM platform is that it will not be possible to go for the full desktop installation. We install the selected package that is required for our application. Nevertheless, it will be nice to work with source building and installation for a package not present in the ROS repository:

• ROS Kinectic <ros_version> is compatible with Ubuntu 16.04 Xenial Xerus

• ROS Melodic <ros_versions> is compatible with Ubuntu 18.04 Bionic Beaver

Configuring repositories

The first step consists of configuring our Ubuntu repositories to allow "restricted," "universe," and "multiverse":

$ sudo vi /etc/apt/sources.list

We have something like this for Ubuntu 16.04:

deb http://ports.ubuntu.com/ubuntu-ports/ xenial main restricted universe multiverse 
#deb-src http://ports.ubuntu.com/ubuntu-ports/ xenial main restricted universe multiverse deb http://ports.ubuntu.com/ubuntu-ports/ xenial-updates main restricted universe multiverse 
#deb-src http://ports.ubuntu.com/ubuntu-ports/ xenial-updates main restricted universe multiverse 
#Kernel source (repos.rcn-ee.com) : https://github.com/RobertCNelson/linux-stable-rcn-ee 
#
#git clone https://github.com/RobertCNelson/linux-stable-rcn-ee
#cd ./linux-stable-rcn-ee #git checkout `uname -r` -b tmp 
# deb [arch=armhf] http://repos.rcn-ee.com/ubuntu/ xenial main 
#deb-src [arch=armhf] http://repos.rcn-ee.com/ubuntu/ xenial main

Similarly, the following is for Ubuntu 18.04:

deb http://ports.ubuntu.com/ubuntu-ports/ bionic main restricted universe multiverse 
#deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic main restricted universe multiverse deb http://ports.ubuntu.com/ubuntu-ports/ bionic-updates main restricted universe multiverse 
#deb-src http://ports.ubuntu.com/ubuntu-ports/ bionic-updates main restricted universe multiverse 
#Kernel source (repos.rcn-ee.com) : https://github.com/RobertCNelson/linux-stable-rcn-ee 
# 
#git clone https://github.com/RobertCNelson/linux-stable-rcn-ee 
#cd ./linux-stable-rcn-ee 
#git checkout `uname -r` -b tmp 
# deb [arch=armhf] http://repos.rcn-ee.com/ubuntu/ bionic main 
#deb-src [arch=armhf] http://repos.rcn-ee.com/ubuntu/ bionic main

Then, use the following to update the sources:

$ sudo apt-get update

Some ROS tools, such as Boost, require that the system locale be set. This can be set with the following:

$ sudo update-locale LANG=C LANGUAGE=C LC_ALL=C LC_MESSAGES=POSIX

Next, we will configure the source lists depending on the Ubuntu version installed in our ARM platform. Run the following command to install the Ubuntu armhf repositories:

$ sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -cs) main" > /etc/apt/sources.list.d/ros-latest.list'

As discussed previously, this step is needed to confirm that the origin of the code is correct and that no one has modified the code or programs without the knowledge of the owner:

$ sudo apt-key adv --keyserver hkp://ha.pool.sks-keyservers.net --recv-key 0xB01FA116

Before the installation of the ROS packages, make sure our Debian package index is up-to-date:

$ sudo apt-get update

There are many different libraries and tools in ROS—not all compile fully on ARM. So, it is not possible to make a full desktop installation. We should install ROS packages individually.

We could install ros-base (Bare Bones), which includes the ROS package, build, and communication libraries, but does not include GUI tools (press ENTER (Y) when prompted):

$ sudo apt-get install ros-<ros_version>-ros-base

However, we could try to install the desktop installation, which includes the ROS, rqt, RViz, and robot-generic libraries:

$ sudo apt-get install ros-<ros_version>-desktop

We can install a specific ROS package:

$ sudo apt-get install ros-<ros_version>-PACKAGE

Find available packages with the following command:

$ apt-cache search ros-<ros_version>

The rosdep command-line tool must be installed and initialized before we can use ROS. This allows us to easily install libraries and solve system dependencies for the source we want to compile, and is required to run some core components in ROS:

$ sudo apt-get install python-rosdep $ sudo rosdep init $ rosdep update

Well done! We have completed the ROS installation for the ARM platform. The ROS scripts and executables are mostly installed in /opt/ros/<ros_version>.

To get access to these scripts and executables, the ROS environment variables need to be added to the bash session. We have to source the following bash file:

$ source /opt/ros/<ros_version>/setup.bash

It's convenient if the ROS environment variables are automatically added to the bash session every time a new shell is launched:

$ echo "source /opt/ros/<ros_version>/setup.bash" >> ~/.bashrc
$ source ~/.bashrc

If we have more than one ROS distribution installed, ~/.bashrc must only source the setup.bash for the version we are currently using:

$ source /opt/ros/<ros_version>/setup.bash

rosinstall is a frequently used command-line tool in ROS that is distributed separately. It enables us to easily download several source trees for the ROS packages with a single command.

This tool is based on Python and can be installed using the following command:

$ sudo apt-get install python-rosinstall

As a basic example, we could run an ROS core on one terminal:

$ roscore

And from another terminal, we can publish a pose message:

$ rostopic pub /dummy geometry_msgs/Pose Position: x: 3.0 y: 1.0 z: 2.0 Orientation: x: 0.0 y: 0.0 z: 0.0 w: 1.0 -r 8

Moreover, we could set ROS_MASTER_URI on our desktop system (in the same network) to point to our ARM Platform (IP 192.168.X.X).

On your laptop, add the following:

$ export ROS_MASTER_URI=http://192.168.1.6:11311

And, we will see pose published from the ARM platform to our laptop.

On your laptop, add the following:

$ rostopic echo -n2 /dummy Position: x: 1.0 y: 2.0 z: 3.0 Orientation: x: 0.0 y: 0.0 z: 0.0 w: 1.0 ---