Building ROS node with OpenCV

[sarahl]

@modaltb So I finally got the docker loaded, and also built cv_bridge and the camera ros driver. However, it doesn't seem to be reading in the camera (a FLIR). When I'm outside the docker, plugging in the device adds /dev/ttyACM0 and /dev/video2, the latter of which is used by the ros node. Is there something I need to do when running the docker to have access to the usb devices?

[modaltb]

@sarahl , here's an example of how we map and HDMI adapter into docker, not exactly the same but shows the usage:

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ModalAI technical documentation for VOXL and VOXL 2 Companion Computers for PX4 and ArduPilot Obstacle Avoidance and GPS-denied navigation, assembled in the USA

ModalAI Technical Docs (docs.modalai.com)

[sarahl]

@modaltb thanks, I actually tried something similar by mapping /dev to /dev, and also passing it in with the --device parameter, but I'll try this out! is there a reason it's mapped as /dev to /opt in here? Should the /dev directory not be used in the docker contained? I did notice when I plugged and unplugged the device and ran ls /dev, that the device list did not update.

[sarahl]

@modaltb actually I think it's working now, and I somehow didn't actually have to map the /dev port. Turns out I just had a typo in my launch file. Thanks again for all the help!

[sarahl]

@modaltb I wanted to send an update, I was able to build and run an Ubuntu 18.04 + ROS Melodic docker + OpenCV 4.2.0 (because some of my nodes weren't working on the ROS Kinetic docker), but did require using multi-line arguments as @Voxlady suggested to reduce the size enough to fit. It seems like the size constraints are somewhere around 2.7 GB virtual docker size, and stem from too many docker overlays. Is there anyway around that in case there is a need for larger docker images?

[modaltb]

Hi @sarahl , unfortunately I don't have a quick answer for this

[Eric Katzfey]

@sarahl You could try using an SD card to build. This would give you a lot more space. You would have to change the Docker start service to tell it to use the SD card instead of /data for the build.

[ryan_meagher]

@Eric-Katzfey Thanks for the suggestion.

For anyone else interested in doing this, these are the steps I took to accomplish this.

• In order to change where the root of the docker runtime points to in the docker service go to
  /etc/systemd/system/docker-start.service and change the following line so that it uses the sd card(ext4 format) in the voxl ExecStart=/usr/bin/docker daemon -g /mnt/sdcard

• restart the service for the changes to take effect: systemctl restart docker-start.service

• Delete the directories that docker uses in the data partition:cd /data; rm -rf containers linkgraph.db overlay tmp volumes graph network repositories-overlay trust

• [NOTE] The previous commands will delete any images that were previously available.

• You can now run voxl-configure-docker-support.sh and a hello world image will be created
  and the directories that were deleted from the /data partition will be in the /mnt/sdcard
  directory.

• You can verify that you have freed up the /data partition via df -h

[Chad Sweet]

Thank you for following up! Added to the docs here: https://docs.modalai.com/docker-on-voxl/

[ryan_meagher]

@Chad-Sweet cool, happy to contribute!

[ryan_meagher]

@Chad-Sweet Hey, I updated my voxl to the newest system image and after doing so my docker is using docker-start.service while before it was using docker-daemon.service.

Not sure why this has changed, but I have updated the above instructions and wanted to let you know so you could change this in the documentation.

Is there a reason why this would have changed after flashing a new system image onto the device? Both times I configured my docker by using voxl-configure-docker-support.sh