Learning ROS for Robotics Programming

In this step, you have to select your Ubuntu version. It is possible to install ROS Electric in various versions of the operating system. You can use any of them, but we recommend you to always use the most updated version to avoid problems:

Once you have added the correct repository, your operating system knows where to download the programs that need to be installed on your system.

This step is to confirm that the origin of the code is correct, and nobody has modified the code or programs without the knowledge of the owner. Normally, when you add a new repository, you have to add the keys of that repository so that it is added to your system's trusted list:

$ wget http://packages.ros.org/ros.key -O - | sudo apt-key add –

We can now be sure that the code came from an authorized site.

Now we are ready to start the installation. Before we start, it would be better to update the software to avoid problems with libraries or the wrong software version. We do this with the following command:

$ sudo apt-get update

ROS is huge; sometimes you will install libraries and programs that you will never use. Normally, it has four different installations depending on the final use; for example, if you are an advanced user, you may only need basic installation for a robot without enough space in the hard disk. For this book, we recommend the use of full installation because it will install everything that's necessary to make the examples and tutorials work.

Don't worry if you don't know what you are installing right now, be it rviz, simulators, or navigation. You will learn everything in the upcoming chapters:

Congratulations! You are in this step because you have an installed version of ROS on your system. To start using it, the system must know where the executable or binary files as well as other commands are. To do this, you need to execute the next script. If you install another ROS distro in addition to your existing version, you can work with both by calling the script of the one you need every time, since this script simply sets your environment. Here, we will use the one for ROS Electric, but just change electric to fuerte or groovy in the following command if you want to try other distros:

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

If you type roscore in the shell, you will see that something is starting. This is the best test to find out whether you have ROS and whether it is installed correctly.

Note that if you open another shell and type roscore or any other ROS command, it does not work. This is because it is necessary to execute the script again to configure the global variables and path for the location where ROS is installed.

It is very easy to solve this. You only need to add the script at the end of your .bashrc file and when you start a new shell, the script will execute and you will have the environment configured. Use the following command to do this:

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

If it happens that you have more than a single ROS distribution installed on your system, your ~/.bashrc file must source only setup.bash of the version you are currently using. This is because the last call will override the environment set of the others, as we have mentioned previously, to have several distros living in the same system and switch among them.

First, you must check that your Ubuntu accepts restricted, universal, and multiversal repositories. Refer to the Installing ROS Electric – using repositories section if you want to see how to do it.

Normally, Ubuntu is configured to allow these repositories and you won't have problems with this step.

Now we are going to add the URLs from where we can download the code. Note that ROS Fuerte doesn't work for Maverick and Natty, so you must have Ubuntu 10.04, 11.10, or 12.04 on your computer.

For this book we have used Ubuntu 12.04 and it works fine. All the examples have been checked, compiled, and executed in this version of Ubuntu.

Open a new shell and type the following command, as we did before, which should work for any Ubuntu version you have:

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

It is important to add the key because with it we can be sure that we are downloading the code from the right place and nobody has modified it.

If you have followed the steps to install ROS Electric, you don't need to do this again as you have already completed this earlier; if not, add the repository using the following command:

$ wget http://packages.ros.org/ros.key -O - | sudo apt-key add –

We are ready to install ROS Fuerte at this point. Before doing something, it is necessary to update all the programs used by ROS. We do it to avoid incompatibility problems.

Type the following command in a shell and wait:

$ sudo apt-get update

Depending on whether you had the system updated or not, the command will take more or less time to finish.

ROS has a lot of parts and installing the full system can be heavy in robots without enough features. For this reason, you can install various versions depending on what you want to install.

For this book, we are going to install the full version. This version will install all the examples, stacks, and programs. This is a good option for us because in some chapters of this book, we will need to use tools, and if we don't install it now, we will have to do it later:

Do not worry if you are installing things that you do not know. In the upcoming chapters, you will learn about everything you are installing and how to use it.

When you gain experience with ROS, you can make basic installations in your robots using only the core of ROS, using less resources, and taking only what you need.

Now that you have installed ROS, to start using it, you must provide Ubuntu with the path where ROS is installed. Open a new shell and type the following command:

$ roscore
roscore: command not found

You will see this message because Ubuntu does not know where to search for the commands. To solve it, type the following command in a shell:

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

Then, type the roscore command once again, and you will see the following output:

...
started roslaunch server http://localhost:45631/
ros_comm version 1.8.11

SUMMARY
========

PARAMETERS
* /rosdistro
* /rosversion

NODES

auto-starting new master
....

This means that Ubuntu knows where to find the commands to run ROS. Note that if you open another shell and type roscore, it will not work. This is because it is necessary to add this script within the .bashrc file. So, every time you start a new shell, the scripts will run because .bashrc always runs when a shell runs.

Use the following commands to add the script:

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

As mentioned before, only source setup.bash for one ROS distribution. Imagine that you had Electric and Fuerte installed on your computer, and you are using Fuerte as the normal version. If you want to change the version used in a shell, you only have to type the following command:

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

If you want to use another version on a permanent basis, you must change the .bashrc file and put the correct script for your version.

ROS has some tools that need to be installed after the principal installation. These tools will help us install dependencies between programs to compile, download, and install packages from ROS. These tools are rosinstall and rosdep. We recommend installing them because we will use them in the upcoming chapters. To install these tools, type the following command in a shell:

$ sudo apt-get install python-rosinstall python-rosdep

Now we have a full installation of ROS on our system. As you can see, only a few steps are necessary to do it.

It is possible to have two or more versions of ROS installed on our computer. Furthermore, you can install ROS on a virtual machine if you don't have Ubuntu installed on your computer.

In the next section, we will explain how to install a virtual machine and use a drive image with ROS. Perhaps this is the best way to get ROS for new users.

The first step is to download the VirtualBox installation file. At the time of writing, the following links had the latest versions available:

Once installed, you need to download the image of Ubuntu. For this tutorial, we will use an Ubuntu copy with ROS Fuerte installed. You can download it from the following URL: http://nootrix.com/wp-content/uploads/2012/08/ROS.ova.

You can find different virtual machines with preinstalled Ubuntu and ROS, but we are going to use this version because it is referred by the official page of ROS.

Creating a new virtual machine with the downloaded file is very easy; just follow the steps outlined in this section. Open VirtualBox and navigate to File | Import Appliance.... Then, click on Open appliance and select the ROS.ova file downloaded before.

In the next window, you can configure the parameters for the new virtual machine. Keep the default configuration and only change the name of the virtual system. This name helps you distinguish this virtual machine from others. Our recommendation is to put a descriptive name; in our case, the book's name.

Click on the Import button and accept the software license agreement in the next window. Then, you will see a progress bar. It means that VirtualBox is copying the file with the virtual image and is creating a new copy with the new name.

Note that this process doesn't modify the original file ROS.ova, and you could create more virtual machines with different copies from the original file.

The process will take a few minutes depending on the speed of your computer. When it finishes, you can start your virtual machine by clicking on the Start button. Remember to select the right machine before starting it. In our case, we have only one machine but you could have more.

Sometimes you will get the error shown in the following screenshot. It is because your computer doesn't have the correct drivers to use USB 2.0. You can fix it by installing Oracle VM VirtualBox Extension Pack, but you can also disable the USB support to start using the virtual machine.

To disable USB support, right-click on the virtual machine and select Settings. In the toolbar, navigate to Ports | USB and uncheck Enable USB 2.0 (EHCI) Controller. You can now start the virtual machine again, and it should start without problems.

Once the virtual machine starts, you should see the ROS-installed Ubuntu 12.04 window on your screen as shown in the following screenshot:

When you have finished these steps, you will have a full copy of ROS Fuerte that can be used in this book. You can run all the examples and stacks that we are going to work with. Unfortunately, VirtualBox has problems while working with real hardware, and it's possible that you can't use this copy of ROS Fuerte for the steps outlined in Chapter 4, Using Sensors and Actuators with ROS.