Building ROS 2 on RHEL

Table of Contents

System requirements
System setup
Get ROS 2 code
Install dependencies using rosdep
Install additional DDS implementations (optional)
Build the code in the workspace
Environment setup
- Source the setup script
Try some examples
Next steps after installing
Additional RMW implementations (optional)
Alternate compilers
- Clang
Stay up to date
Troubleshooting
Uninstall

System requirements 

The current target Red Hat platforms for Galactic Geochelone are:

Tier 2: RHEL 8 64-bit

As defined in REP 2000

Make sure you have a locale which supports UTF-8. If you are in a minimal environment (such as a docker container), the locale may be something minimal like C. We test with the following settings. However, it should be fine if you’re using a different UTF-8 supported locale.

locale  # check for UTF-8

sudo dnf install langpacks-en glibc-langpack-en
export LANG=en_US.UTF-8

locale  # verify settings

Enable required repositories 

The rosdep database contains packages from the EPEL and PowerTools repositories, which are not enabled by default. They can be enabled by running:

sudo dnf install 'dnf-command(config-manager)' epel-release -y
sudo dnf config-manager --set-enabled powertools

Install development tools and ROS tools 

sudo dnf install -y \
  cmake \
  gcc-c++ \
  git \
  make \
  patch \
  python3-colcon-common-extensions \
  python3-pip \
  python3-rosdep \
  python3-setuptools \
  python3-vcstool \
  wget
# install some pip packages needed for testing and
# not available as RPMs
python3 -m pip install -U --user \
  flake8-blind-except \
  flake8-builtins \
  flake8-class-newline \
  flake8-comprehensions \
  flake8-deprecated \
  flake8-docstrings \
  flake8-import-order \
  flake8-quotes \
  mypy==0.761 \
  pydocstyle \
  pytest-repeat \
  pytest-rerunfailures \
  pytest \
  setuptools

Get ROS 2 code 

Create a workspace and clone all repos:

mkdir -p ~/ros2_galactic/src
cd ~/ros2_galactic
wget https://raw.githubusercontent.com/ros2/ros2/galactic/ros2.repos
vcs import src < ros2.repos

Install dependencies using rosdep 

sudo rosdep init
rosdep update
rosdep install --from-paths src --ignore-src -y --skip-keys "fastcdr rti-connext-dds-5.3.1 urdfdom_headers pydocstyle python3-mypy python3-babeltrace python3-lttng asio"

Install additional DDS implementations (optional)

If you would like to use another DDS or RTPS vendor besides the default, Cyclone DDS, you can find instructions here.

Build the code in the workspace 

If you have already installed ROS 2 another way (either via RPMs or the binary distribution), make sure that you run the below commands in a fresh environment that does not have those other installations sourced. Also ensure that you do not have source /opt/ros/${ROS_DISTRO}/setup.bash in your .bashrc. You can make sure that ROS 2 is not sourced with the command printenv | grep -i ROS. The output should be empty.

More info on working with a ROS workspace can be found in this tutorial.

cd ~/ros2_galactic/
colcon build --symlink-install --cmake-args -DTHIRDPARTY_Asio=ON --no-warn-unused-cli

Note: if you are having trouble compiling all examples and this is preventing you from completing a successful build, you can use COLCON_IGNORE in the same manner as CATKIN_IGNORE to ignore the subtree or remove the folder from the workspace. Take for instance: you would like to avoid installing the large OpenCV library. Well then simply run touch COLCON_IGNORE in the cam2image demo directory to leave it out of the build process.

Environment setup 

Source the setup script 

Set up your environment by sourcing the following file.

. ~/ros2_galactic/install/local_setup.bash

Try some examples 

In one terminal, source the setup file and then run a C++ talker:

. ~/ros2_galactic/install/local_setup.bash
ros2 run demo_nodes_cpp talker

In another terminal source the setup file and then run a Python listener:

. ~/ros2_galactic/install/local_setup.bash
ros2 run demo_nodes_py listener

You should see the talker saying that it’s Publishing messages and the listener saying I heard those messages. This verifies both the C++ and Python APIs are working properly. Hooray!

Next steps after installing 

Continue with the tutorials and demos to configure your environment, create your own workspace and packages, and learn ROS 2 core concepts.

Additional RMW implementations (optional)

The default middleware that ROS 2 uses is Cyclone DDS, but the middleware (RMW) can be replaced at runtime. See the guide on how to work with multiple RMWs.

Alternate compilers 

Using a different compiler besides gcc to compile ROS 2 is easy. If you set the environment variables CC and CXX to executables for a working C and C++ compiler, respectively, and retrigger CMake configuration (by using --force-cmake-config or by deleting the packages you want to be affected), CMake will reconfigure and use the different compiler.

Clang 

To configure CMake to detect and use Clang:

sudo dnf install clang
export CC=clang
export CXX=clang++
colcon build --cmake-force-configure

If you installed your workspace with colcon as instructed above, “uninstalling” could be just a matter of opening a new terminal and not sourcing the workspace’s setup file. This way, your environment will behave as though there is no Galactic install on your system.
If you’re also trying to free up space, you can delete the entire workspace directory with:
```
rm -rf ~/ros2_galactic
```