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ros2: start node with sudo rights

asked 2021-01-19 09:10:56 -0500

urczf gravatar image

updated 2021-01-19 10:21:19 -0500


as I have some nodes on a Raspi requiring access to the hardware, some of my nodes need to be started with sudo rights.

The easiest, but imho undesirable solution, is to open a shell with sudo -s and afterwards start the node. However, this is not really user-friendly. Is there a better solution for that? As mentioned in this post, launch-prefix may be used. However, this is a solution for ROS1. I gave it a try, and this results in errors. If I set the launch-prefix to either sudo or sudo -E, the following error occurs:

[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [led_strip_node-1]: process started with pid [20011]                                                          
[led_strip_node-1] Traceback (most recent call last):
[led_strip_node-1]   File "/home/pi/vehicle_workspace/install/vehicle_hardware/lib/vehicle_hardware/led_strip_node", line 33, in <module>
[led_strip_node-1]     sys.exit(load_entry_point('vehicle-hardware', 'console_scripts', 'led_strip_node')())         
[led_strip_node-1]   File "/home/pi/vehicle_workspace/install/vehicle_hardware/lib/vehicle_hardware/led_strip_node", line 22, in importlib_load_entry_point
[led_strip_node-1]     for entry_point in distribution(dist_name).entry_points                                       
[led_strip_node-1]   File "/home/pi/vehicle_workspace/env/lib/python3.7/site-packages/importlib_metadata/", line 549, in distribution
[led_strip_node-1]     return Distribution.from_name(distribution_name)                                              
[led_strip_node-1]   File "/home/pi/vehicle_workspace/env/lib/python3.7/site-packages/importlib_metadata/", line 206, in from_name
[led_strip_node-1]     raise PackageNotFoundError(name)
[led_strip_node-1] importlib_metadata.PackageNotFoundError: vehicle-hardware                                         
[ERROR] [led_strip_node-1]: process has died [pid 20011, exit code 1, cmd 'sudo -E /home/pi/vehicle_workspace/install/vehicle_hardware/lib/vehicle_hardware/led_strip_node --ros-args'].

Thanks in advance! urczf

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Wouldn't the 'best' solution be to make sure the user starting the ROS nodes has the access rights, instead of starting a whole node with root privileges?

What about writing a udev rule which allows a certain group read/write access? And then make your $USER a member of that group.

That's a very common approach which completely removes the need for running ROS nodes as root (which from a security perspective is not a very nice thing to do).

gvdhoorn gravatar image gvdhoorn  ( 2021-01-19 11:33:09 -0500 )edit

The questen is why do you need root rights, because it is not windows so you could solfe the problem buy adding you user to some groups.

duck-development gravatar image duck-development  ( 2021-01-19 12:50:14 -0500 )edit

Isn't this exactly what I wrote in my comment?

gvdhoorn gravatar image gvdhoorn  ( 2021-01-19 13:09:46 -0500 )edit

We need to access /dev/mem which is not possible with udev rules. By adding $USER to the root group would imply that by default I have always su rights, which is not what I want.

urczf gravatar image urczf  ( 2021-01-20 10:12:18 -0500 )edit

Are these GPIOs you're trying to access? I remember similar questions but in a ROS 1 context and I believe the solution was to use /dev/gpiomem instead of /dev/mem directly.

As to your issue: it's likely the environment of your process is getting sanatised, leading to the PYTHONPATH no longer containing the required packages.

gvdhoorn gravatar image gvdhoorn  ( 2021-01-20 10:36:34 -0500 )edit

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answered 2022-04-18 12:10:10 -0500

francisc0garcia gravatar image

Hi there,

This launch config works for my use case (Raspberry Pi 4 - ROS2 Galactic - run node as root with access to GPIO). You might need to add your user to /etc/sudoers to skip password prompt.

from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    return LaunchDescription([
            # Launch the node with root access (GPIO) in a shell
            prefix=["sudo -E env \"PYTHONPATH=$PYTHONPATH\" \"LD_LIBRARY_PATH=$LD_LIBRARY_PATH\" \"PATH=$PATH\" \"USER=$USER\"  bash -c "],
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Asked: 2021-01-19 09:10:56 -0500

Seen: 758 times

Last updated: Apr 18