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ROS Installation

The robot's computer runs ROS Noetic on Ubuntu 20.04 Focal Fossa (Raspberry Pi Setup). ROS Noetic reached its end of life in May 2025, at the same time as the standard support of Ubuntu 20.04; Ubuntu MATE's own support for 20.04 ended in April 2023. This project still uses them, and the ROS package server keeps the final Noetic packages, so the installation below works. A container for the robot, to run Noetic on a newer host OS, is planned in diffbot#109, and the way to ROS 2 in diffbot#107.

All in one for Remo: raspi-setup.sh

The diffbot repository's raspi-setup.sh runs the commands of this page and of Packages Setup in one go, for Remo. On the robot:

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curl -O https://raw.githubusercontent.com/ros-mobile-robots/diffbot/noetic-devel/raspi-setup.sh
bash raspi-setup.sh

The sections below explain what the script does. Hardware Interfaces is still needed: it gives your user access to I2C and the serial port. For DiffBot, follow the pages: its camera driver needs the extra steps on Raspberry Pi Camera, which the script doesn't do yet.

Install ROS Noetic

The key that signs the ROS packages expired on 1 June 2025 and was renewed. The ros-apt-source package sets up the package source together with the current key, as the ROS signing key migration guide recommends.

Robot set up before June 2025? Remove the old package source first

Older instructions, including the ROS wiki and earlier versions of this page, add the package source to /etc/apt/sources.list.d/ros-latest.list and the key with apt-key. If your robot has that file, sudo apt update fails because the key from back then has expired (EXPKEYSIG). Remove the old entry and key before the commands below, as the migration guide describes:

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sudo rm /etc/apt/sources.list.d/ros-latest.list
sudo apt-key del "C1CF 6E31 E6BA DE88 68B1 72B4 F42E D6FB AB17 C654"

Download and install ros-apt-source:

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sudo apt update && sudo apt install curl -y
export ROS_APT_SOURCE_VERSION=$(curl -s https://api.github.com/repos/ros-infrastructure/ros-apt-source/releases/latest | grep -F "tag_name" | awk -F\" '{print $4}')
curl -L -o /tmp/ros-apt-source.deb "https://github.com/ros-infrastructure/ros-apt-source/releases/download/${ROS_APT_SOURCE_VERSION}/ros-apt-source_${ROS_APT_SOURCE_VERSION}.$(. /etc/os-release && echo $VERSION_CODENAME)_all.deb"
sudo dpkg -i /tmp/ros-apt-source.deb

The second command asks GitHub for the latest version of ros-apt-source. GitHub answers 60 such requests per hour from one IP address, for example for a classroom behind one router. If dpkg reports that the file isn't a Debian archive, try again later, or set the version by hand, for example export ROS_APT_SOURCE_VERSION=1.3.0, and repeat the last two commands.

Then install ROS for the robot, ros-noetic-robot, without the GUI tools: RViz, Gazebo and rqt run on your PC, in the dev container. Install the tools to set up and build the workspace with it, among them the C++ compiler (build-essential), and python-is-python3, which nodes written with rospy need:

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sudo apt update
sudo apt install ros-noetic-robot python3-rosdep python3-catkin-tools python3-vcstool build-essential python-is-python3

Load ROS in every new terminal:

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

Dependencies: rosdep

rosdep installs the system dependencies that ROS packages list in their package.xml. Set it up once:

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sudo rosdep init
rosdep update --rosdistro noetic

Noetic is past its end of life, so a plain rosdep update skips it, and rosdep install then can't find the ROS packages. --rosdistro noetic includes it.

The dependencies of diffbot's packages are installed later, once they are in the workspace: see Packages Setup.

Build Tool: catkin_tools

To work with ROS we will use catkin_tools instead of catkin_make. catkin_tools provide commands such as catkin build which we will use instead of catkin_make because the catkin_tools are more actively developed than catkin_make ref.

Note

It is recommended to use catkin_tools instead of the default catkin when building ROS workspaces. catkin_tools provides a number of benefits over regular catkin_make and will be used in the documentation. All packages can be built using catkin_make however: use catkin_make in place of catkin build where appropriate.

catkin_tools came with the python3-catkin-tools package above. Create and initialize a workspace, catkin_ws, with the commands from the catkin_tools quick start. ROS is already loaded through ~/.bashrc:

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fjp@ubuntu:~$ mkdir -p ~/catkin_ws/src           # Make a new workspace and source space
fjp@ubuntu:~$ cd ~/catkin_ws                     # Navigate to the workspace root
fjp@ubuntu:~/catkin_ws$ catkin init                         # Initialize it with a hidden marker file
Initializing catkin workspace in `/home/fjp/catkin_ws`.
----------------------------------------------------------------
Profile:                     default
Extending:             [env] /opt/ros/noetic
Workspace:                   /home/fjp/catkin_ws
----------------------------------------------------------------
Build Space:       [missing] /home/fjp/catkin_ws/build
Devel Space:       [missing] /home/fjp/catkin_ws/devel
Install Space:      [unused] /home/fjp/catkin_ws/install
Log Space:         [missing] /home/fjp/catkin_ws/logs
Source Space:       [exists] /home/fjp/catkin_ws/src
DESTDIR:            [unused] None
----------------------------------------------------------------
Devel Space Layout:          linked
Install Space Layout:        None
----------------------------------------------------------------
Additional CMake Args:       None
Additional Make Args:        None
Additional catkin Make Args: None
Internal Make Job Server:    True
Cache Job Environments:      False
----------------------------------------------------------------
Whitelisted Packages:        None
Blacklisted Packages:        None
----------------------------------------------------------------
Workspace configuration appears valid.
----------------------------------------------------------------

Command Overview of catkin_tools

To create packages, which will be covered in the next posts in more depth, we will use catkin create pkg PKG_NAME.

Building the workspace is done with catkin build.

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fjp@ubuntu:~/catkin_ws$ catkin build
----------------------------------------------------------------
Profile:                     default
Extending:             [env] /opt/ros/noetic
Workspace:                   /home/fjp/catkin_ws
----------------------------------------------------------------
Build Space:        [exists] /home/fjp/catkin_ws/build
Devel Space:        [exists] /home/fjp/catkin_ws/devel
Install Space:      [unused] /home/fjp/catkin_ws/install
Log Space:         [missing] /home/fjp/catkin_ws/logs
Source Space:       [exists] /home/fjp/catkin_ws/src
DESTDIR:            [unused] None
----------------------------------------------------------------
Devel Space Layout:          linked
Install Space Layout:        None
----------------------------------------------------------------
Additional CMake Args:       None
Additional Make Args:        None
Additional catkin Make Args: None
Internal Make Job Server:    True
Cache Job Environments:      False
----------------------------------------------------------------
Whitelisted Packages:        None
Blacklisted Packages:        None
----------------------------------------------------------------
Workspace configuration appears valid.

NOTE: Forcing CMake to run for each package.
----------------------------------------------------------------
[build] No packages were found in the source space '/home/fjp/catkin_ws/src'
[build] No packages to be built.
[build] Package table is up to date.
Starting  >>> catkin_tools_prebuild
Finished  <<< catkin_tools_prebuild                [ 10.0 seconds ]
[build] Summary: All 1 packages succeeded!
[build]   Ignored:   None.
[build]   Warnings:  None.
[build]   Abandoned: None.
[build]   Failed:    None.
[build] Runtime: 10.1 seconds total.

Environment Setup

Finally the newly built packages have to be loaded in the environment using source.

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fjp@ubuntu:~/catkin_ws$ source ~/catkin_ws/devel/setup.bash # Load the workspace's environment

Tip

To avoid tediously typing the above source command, it is convenient to create an alias in your ~/.bashrc or ~/.zshrc similar to the following: 

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alias s='source devel/setup.bash'
or using the absolute path 
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alias sa='source ~/catkin_ws/devel/setup.bash'
It is recommended to use the correct setup script for the shell you use (bash, zsh, etc.). In case you are unsure, you can check with the echo $SHELL command which will most likely output /bin/bash.

Info

Instead of source it is possible to use the . command instead. Don't confuse it though with the current directory, which is also represented as ..

Next, on the robot: Hardware Interfaces, for access to USB, GPIO and I2C.

Resources

Although the catkin tutorial uses catkin_make it provides a helpful guide to create a workspace

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