# Chapter 3 - Running the Object Detection nodes

**URL:** <https://get-help.theconstruct.ai/t/chapter-3-running-the-object-detection-nodes/23538>\
**Category:** ROS2 Manipulation Basics\
**Created:** [April 5, 2023, 4:54am UTC](https://get-help.theconstruct.ai/t/chapter-3-running-the-object-detection-nodes/23538 "2023-04-05T04:54:59Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![prostraintech](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/p/ce7236/32.png) [@prostraintech](https://get-help.theconstruct.ai/u/prostraintech)\
**Post date:** [April 5, 2023, 4:54am UTC](https://get-help.theconstruct.ai/t/chapter-3-running-the-object-detection-nodes/23538/1 "2023-04-05T04:54:59Z")

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Hello, I am trying to run the object detection node in Chapter 3 by running this command

```auto
ros2 run simple_grasping basic_grasping_perception_node --ros-args -p debug_topics:=true

```

But I got this error. I tried to recompile and source the workspace a few times but still does not work.

```auto
/home/user/ros2_ws/install/simple_grasping/lib/simple_grasping/basic_grasping_perception_node: symbol lookup error: /home/user/ros2_ws/install/simple_grasping/lib/simple_grasping/basic_grasping_perception_node: undefined symbol: _ZNK12class_loader11ClassLoader14getLibraryPathB5cxx11Ev

```

---

<div class="post-metadata">

**Author:** ![Dazai](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/d/c77e96/32.png) [@Dazai](https://get-help.theconstruct.ai/u/Dazai)\
**Post date:** [April 5, 2023, 8:43am UTC](https://get-help.theconstruct.ai/t/chapter-3-running-the-object-detection-nodes/23538/2 "2023-04-05T08:43:08Z")

</div>

One possible reason for this error is that the Class Loader library is not properly installed or linked. You may want to check if the Class Loader library is properly installed and available on your system. You can do this by running the command `ldconfig -p | grep class_loader` in your terminal. This command will show you if the Class Loader library is installed and where it is located.

Another possible reason for this error is that there is a version mismatch between the Class Loader library and the library `basic_grasping_perception_node`. In this case, you may want to ensure that the Class Loader library and the `basic_grasping_perception_node` library are built and linked against the same version of the Class Loader library.

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<div class="post-metadata">

**Author:** ![iisaac.saito](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/iisaac.saito/32/6413_2.png) [@iisaac.saito](https://get-help.theconstruct.ai/u/iisaac.saito)\
**Post date:** [April 23, 2023, 10:38am UTC](https://get-help.theconstruct.ai/t/chapter-3-running-the-object-detection-nodes/23538/3 "2023-04-23T10:38:33Z")

</div>

I saw the similar/same error and asked [get-help.robotigniteacademy.com#23704](https://get-help.robotigniteacademy.com/t/manipulation-unit3-action-client-ends-up-w-undefined-symbol-rosidl-double-sequence-are-equal/23704/2). I’ve only found a workaround.