Running a Camera Sensor Headless

Question

Hello,

We are looking to run a camera sensor headless on a VM, however when we do so several of the camera's image topic (notably, camera/image_raw) are not published. At ROSCon, I spoke briefly with Jose, who indicated that this could be done fairly painlessly, and is actually used for Gazebo's CI tests. How would I go about enabling that capability?

To clarify, we already have a camera plugin that runs just fine on a display-enabled machine. Our robot is defined in a URDF and launched using roslaunch. However, note that the "headless" option exposed by gazebo_ros_pkgs doesn't actually work - see https://github.com/ros-simulation/gazebo_ros_pkgs/issues/491

I also don't see an explicit "headless" option list in the Gazebo code. The Gazebo devs did mention that such a mode was possible, I just can't figure out how.

(Running Gazebo 7 and ROS Indigo)

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Originally posted by JLiviero on Gazebo Answers with karma: 94 on 2016-10-19

Post score: 0

Answer 1

I think it can be done by running the Gazebo server in Headless mode with the following command

gzserver  # then you can use gz topic -l to verify it is running

By default it doesn't have a camera sensor, so you will have to define your own world SDF file with a camera sensor.

The rest is up to you.

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Originally posted by chutsu with karma: 36 on 2016-10-19

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Original comments

Comment by JLiviero on 2016-10-24:
As I noted in the question, we already have a camera plugin that runs just fine on a display-enabled machine. Our robot is defined in a URDF and launched using roslaunch. I should have been more clear, sorry - I've updated my original question accordingly.

Comment by nkoenig on 2016-10-25:
gzserver runs headless. Your machine will need an xserver running if you want to render camera data.

Answer 2

Hello Jordan:

As Nate has mentioned in the comments, you will need an xserver running to be able to render camera data. In order to have an xserver running with a headless setup and assuming that you are using an Nvidia card, you could use (starting with 331.* driver series):

nvidia-xconfig --allow-empty-initial-configuration

This should generate the following configuration in your Xorg.conf file:

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    ...
    Option         "AllowEmptyInitialConfiguration" "True"
    ...
EndSection

Hope it helps. Thanks for sharing the feedback in the ROSCon!

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Originally posted by Jose Luis Rivero with karma: 1485 on 2016-10-26

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Original comments

Comment by jsather on 2018-08-28:
Hi Jose,

For this to work, do you also need to set up a display server like Xvfb? I am trying to run Gazebo on a Google Compute Engine instance running Ubuntu 16.04 with an Nvidia K80 GPU and have yet to get it working. If you are willing to take a look, I included a few more details in my StackOverflow post: https://stackoverflow.com/questions/52050708/how-to-run-gazebo-on-google-compute-engine-with-gpu

Answer 3

Thanks guys. I've got a solution, which I'll post here for the benefit of anyone else who comes searching for such a thing later.

Because our VMs aren't running NVidia drivers as a rule, I wanted to explore some other options before attempting Jose's solution. Based on Nate and Jose's comments, I went digging into virtual xservers and found this old comment, which led me to Xvfb. With Xvfb, I was able to do the following:

$ Xvfb :1 -screen 0 1600x1200x16  &
$ export DISPLAY=:1.0
$ roslaunch etc etc.launch

...which let me run the camera plugin headlessly on a VM with no problems. Here's a screen grab from the camera, taken remotely by connecting RQT to the robot on the VM:

(This timely Gazebo fix was also helpful.)

Thanks again!

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Originally posted by JLiviero with karma: 94 on 2016-10-31

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Original comments

Comment by GL on 2017-01-12:
This solution worked with my launch file. Thank you for sharing your fix!