2. Installing Ubuntu and ROS 2

Match the versions first

Danger

Each ROS 2 release supports exactly one Ubuntu version. Install the wrong Ubuntu and you cannot install the ROS 2 you want — you have to reinstall the whole OS. Check this before you start.

ROS 2	Ubuntu	End of life
Humble ← this guide	22.04	May 2027
Jazzy	24.04	May 2029

Humble is chosen because the mobile-robot packages (Nav2, slam_toolbox, LiDAR drivers) are the most stable and have the most examples.

Install Ubuntu 22.04

Use Ubuntu Desktop 22.04 LTS, not Server — RViz needs a display.

Download from releases.ubuntu.com/22.04

Tip

Install on real hardware, not VirtualBox or VMware, if you intend to connect real devices. Virtual machines commonly have trouble with USB ports and with clock drift, and clock drift corrupts odometry.

Install ROS 2 Humble

Run these in order, letting each block finish.

① Enable the repositories Ubuntu needs

sudo apt update && sudo apt install -y software-properties-common curl
sudo add-apt-repository universe

② Add the ROS 2 key and source

sudo curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.key \
  -o /usr/share/keyrings/ros-archive-keyring.gpg

echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/ros-archive-keyring.gpg] \
http://packages.ros.org/ros2/ubuntu $(. /etc/os-release && echo $UBUNTU_CODENAME) main" \
  | sudo tee /etc/apt/sources.list.d/ros2.list > /dev/null

③ Install

sudo apt update
sudo apt install -y ros-humble-desktop

ros-humble-desktop includes RViz and the demo nodes. It takes a while and about 3 GB.

④ Build tools

sudo apt install -y python3-colcon-common-extensions python3-rosdep
sudo rosdep init && rosdep update

Prove it works

Installing is not enough — you must source in every new terminal.

source /opt/ros/humble/setup.bash

Then test with two terminals.

Terminal 1

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

Terminal 2

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

The talker should print Publishing: 'Hello World: 1' repeatedly, and the listener should print I heard: [Hello World: 1] right behind it.

Important

This test proves two things at once — the install is complete, and node-to-node communication works. If the talker prints but the listener is silent, fix that before going any further.

Sourcing automatically

Typing source every time gets old. Put it in ~/.bashrc:

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

Warning

🔴 This cuts both ways. Once you do it you will forget sourcing exists. The day you use another machine that is not set up, you get ros2: command not found and wonder why that machine is broken — when you simply have not sourced.

.bashrc types it for you. It does not remove the requirement.

Common problems

Symptom	Cause
ros2: command not found	Not sourced: source /opt/ros/humble/setup.bash
apt cannot find ros-humble-desktop	Ubuntu is not 22.04 — check with lsb_release -a
Talker runs but listener hears nothing	Terminal 2 not sourced, or a firewall is blocking
Download is very slow	Switch to a closer Ubuntu mirror

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