Hi everyone, I'm new to ROS and try to do the NAV2 tutorial for a university project. Everything worked until i tried to launch in the "SEtting up the URDF"-part.

I use Ubuntu 20.04 and ROS2 galactic. I also installed the used packages: sudo apt install ros-<ros2-distro>-joint-state-publisher-gui sudo apt install ros-<ros2-distro>-xacro

After building with colcon and calling the setup.bash in my project, I get the following error:

[INFO] [launch]: All log files can be found below /home/valentin/.ros/log/2022-05-17-06-33-09-822486-valentin-7458
[INFO] [launch]: Default logging verbosity is set to INFO
Task exception was never retrieved
future: <Task finished name='Task-2' coro=<LaunchService._process_one_event() done, defined at /home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/launch_service.py:226> exception=SubstitutionFailure("file not found: [Errno 2] No such file or directory: 'xacro'")>
Traceback (most recent call last):
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/substitutions/command.py", line 108, in perform
    result = subprocess.run(
  File "/usr/lib/python3.8/subprocess.py", line 493, in run
    with Popen(*popenargs, **kwargs) as process:
  File "/usr/lib/python3.8/subprocess.py", line 858, in __init__
self._execute_child(args, executable, preexec_fn, close_fds,


File "/usr/lib/python3.8/subprocess.py", line 1704, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'xacro'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/launch_service.py", line 228, in _process_one_event
    await self.__process_event(next_event)
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/launch_service.py", line 248, in 

__process_event
    visit_all_entities_and_collect_futures(entity, self.__context))
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-

packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 45, in visit_all_entities_and_collect_futures
    futures_to_return += visit_all_entities_and_collect_futures(sub_entity, context)
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 45, in visit_all_entities_and_collect_futures
    futures_to_return += visit_all_entities_and_collect_futures(sub_entity, context)
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 45, in visit_all_entities_and_collect_futures
    futures_to_return += visit_all_entities_and_collect_futures(sub_entity, context)
  [Previous line repeated 1 more time]
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 38, in visit_all_entities_and_collect_futures
    sub_entities = entity.visit(context)



File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/action.py", line 108, in visit
    return self.execute(context)
      File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch_ros/actions/node.py", line 465, in execute
        self._perform_substitutions(context)
      File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch_ros/actions/node.py", line 420, in _perform_substitutions
        evaluated_parameters = evaluate_parameters(context, self.__parameters)
      File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch_ros/utilities/evaluate_parameters.py", line 151, in evaluate_parameters
    output_params.append(evaluate_parameter_dict(context, param))
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch_ros/utilities/evaluate_parameters.py", line 72, in evaluate_parameter_dict
    evaluated_value = perform_substitutions(context, list(value))
  File "/home/val

entin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/utilities/perform_substitutions_impl.py", line 26, in perform_substitutions
    return ''.join([context.perform_substitution(sub) for sub in subs])
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/utilities/perform_substitutions_impl.py", line 26, in <listcomp>
    return ''.join([context.perform_substitution(sub) for sub in subs])
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/launch_context.py", line 197, in perform_substitution
    return substitution.perform(self)
  File "/home/valentin/ros2_galactic/ros2-linux/lib/python3.8/site-packages/launch/substitutions/command.py", line 114, in perform
    raise SubstitutionFailure(f'file not found: {ex}')
launch.substitutions.substitution_failure.SubstitutionFailure: file not found: [Errno 2] No such file or directory: 'xacro'

Maybe the solution is very simple, bút i have actually no idea :) Thanks for your help.