Rosdep

The VM has been updated since producing this video. You should expect your build to be error-free. and absent the build errors the speaker addresses in the video.

After the last exercise, you might have noticed the following warning line:

The controller spawner couldn’t find the expected controller_manager ROS interface.

ROS packages have two different types of dependencies: build dependencies, and run dependencies. This error message was due to a missing runtime dependency.

The rosdep tool will check for a package's missing dependencies, download them, and install them.

To check for missing dependencies in the simple_arm package:

$ rosdep check simple_arm

Note : In order for the command to work, the workspace must be sourced.

This gives you a list of the system dependencies that are missing, and where to get them.

To have rosdep install packages, invoke the following command from the root of the catkin workspace

$ rosdep install -i simple_arm

Issues with this command may arise when using a VM. If this is the case, please try:

sudo apt-get install ros-kinetic-gazebo-ros-control

And there you have it, launch the simple_arm package again and your arm should no longer be swinging around!

With all packages properly installed, you will now learn more about ROS packages, in preparation for writing your own nodes in the next lesson!