Ubuntu Linux for Robotics · Lesson 37 of 96

Build with colcon

colcon build, options, reading the output and running your first executable.

Estimated time · 45–60 min

Learning goals

What you will understand

Explain build with colcon in your own words
Use it in a small workstation example
Verify the result instead of assuming it worked

Understand the idea first

The mental model

colcon build compiles every package in src in dependency order, installing the result into install/. Useful options: --symlink-install (edits to Python and config files apply without rebuilding), --packages-select name (build one package), --packages-up-to name, and --cmake-args -DCMAKE_BUILD_TYPE=Release for a faster build.

After building you must source the workspace (source install/setup.bash) so the shell can find the new executables. Read the summary at the end: 'Summary: N packages finished' means success. Warnings are worth fixing; the first error is usually the only one that matters.

Guided lesson

Work through these steps

1.
Open a terminal and record the current state before changing anything.
2.
Read the build with colcon commands and predict what each one does.
3.
Run the commands one at a time and compare each output with your prediction.
4.
Write the commands that worked in a setup note you can repeat later.

Worked example

Read it before you run it

cd ~/ros2_ws
# Always build from the workspace root.
source /opt/ros/lyrical/setup.bash
# The underlay must be sourced before building.
colcon build --symlink-install
# Build all packages.
colcon build --packages-select demo_nodes_cpp
# Rebuild only one package.
source install/setup.bash
# Make the built packages visible in this terminal.
ros2 run demo_nodes_cpp talker
# Run an executable from the workspace.

What the example is doing

1.Lines without sudo only inspect or change files you own; sudo authorizes a system-wide change.
2.Read command output before moving to the next line. Stop if names, versions, disks, or paths differ from the lesson.
3.Comments beginning with # explain safety checks and are not executed by the shell.

Watch it run · Build and run

See what this code does

The terminal types this lesson's practice solution and runs it. The scene shows the kind of robot behaviour that code drives. It plays by itself and loops.

Practice code

Now type it yourself

Open a terminal, run the starter line by line (or save it as practice.sh and run bash practice.sh), and replace every TODO with your own command.

cd ~/ros2_ws
source /opt/ros/lyrical/setup.bash
# TODO: build the workspace with colcon, using symlink install

Expected output

Summary: N packages finished

Stuck? Show the full solution (try it yourself first)

cd ~/ros2_ws
source /opt/ros/lyrical/setup.bash
colcon build --symlink-install

Expected result

How you know it worked

Each command completes without an unexplained error.
Your notes contain the command, the important output, and what it proves.

Practical exercise

Apply the lesson

Build the workspace, read the build summary, break one C++ file on purpose to see the error, fix it, rebuild only that package with --packages-select, and run the result.

Before you continue

You recorded the starting state
Every command and output is understood
The change can be repeated from your notes

If something goes wrong

A command says permission denied.

Check ownership and permissions first. Do not add sudo unless the command changes a documented system location.

A command or package is not found.

Check spelling, Ubuntu version, enabled repositories, and whether the previous installation command succeeded.