Different ROS version on laptop and workstation

[rickstaa]

Can the ROS version I use on my laptop be different from the one that is on the panda workstation?

[rickstaa]

As explained by this ROS answer, as long as the specific messages have not been changed between the two ROS distributions (which is only rarely the case), it should be work fine.

On the panda robot, this is not the case. When you use ROS kinetic on the workstation while you installed ROS noetic on your laptop, you are likely to run into several md5sum mismatch errors. As a result, you, have to install ROS Noetic on the workstation or run the franka_control node in a singularity container (see instructions below on how to use such a container).

How to run the franka_control node in a singularity container

Singularity is a free, cross-platform and open-source computer program that performs operating-system-level virtualization, also known as containerization. It is similar to docker in that it allows you to run a container with a different OS than the main system. The difference with docker is that it is better optimized for High-Performance Computing (HPC) and scientific purposes.

Install singularity

Singularity should already be installed on the workstation that is used with the Panda robot. If it is not, or you need to reinstall, please follow the documentation.

How to build the singularity container

The singularity container should also already present in the /home/userpanda/containers/singularity folder. If this is not the case, the recipes for building this container can be found in this repository's containers/singularity folder. You can build this container with the following command:

sudo singularity build --sandbox ros-noetic Singularity.ros_noetic-focal

The --sandbox flag makes sure that the container is built as a folder.

How to run the singularity container

After the container has successfully built, you can shell into, run or start the container.

Shell into the container

Run a shell within a container using the following command:

sudo singularity shell --writable ros-noetic

The --writable flag is important to be able to make changes in the container. In addition, the sudo is needed if you want to install additional packages. If this does not work on your system, you might have to use network virtualization.

After you are in the container, you have to set export ROS_MASTER_URI and ROS_IP environmental variables while ensuring the ROS_HOSTNAME variable is not set. You can then start the franka_control node and connect to it using your laptop. To work, you have to make sure that the ROS_MASTER_URI and ROS_IP environmental variables are also set in the laptop.

Run the container

You can also run the container. This sets up the required environment variables that are needed to start the franka_control node. Use the following command to run the container:

sudo singularity run --writable ros-noetic

Container permissions

By default, your user can not write to the container folder from outside the container. If you did build the singularity container as a writeable folder, you could give your user write and read access from outside the singularity container by:

1. Changing the group owner to your user group:

sudo chgrp -R <YOUR_USER_NAME> ./<YOUR_CONTAINER_NAME>

2. Giving your user group read and write access to the <YOUR_CONTAINER_NAME folder:

sudo chmod -R g+rwx ./<YOUR_CONTAINER_NAME>

Change the container bash prompt

You can change the container bash prompt to show the current working directory by setting the SINGULARITYENV_PS1 environmental variable (See the singularity documentation).

export SINGULARITYENV_PS1="Singularity:\[\e[01;32m\]\w\[\e[m\]> "

Troubleshooting

Segmentation fault (core dumped)

If you get a segmentation fault (core dumped) error, this probably means that your container requires access to memory it currently doesn't have access to (see [this stack question](https://stackoverflow.com/questions/19641597/what-is-segmentation-fault-core-dumped)). If this happens, you can try to run the runcommand as the root user (i.e.sudo) or switch to using the shell` command.

Control commands not received on workstation

When your control commands are not received on the workstation, but you can receive messages from the workstation, you probably set your ${ROS_IP} on your control laptop wrong.

X11 applications not working inside container

Make sure you use the --nv flag and added your user name to the xhost control access list when you can not open GUI applications like RVIZ and Gazebo (see apptainer/singularity#3800). To add your user account use xhost local:$(whoami) > /dev/null to add the root user use xhost local:root > /dev/null. If it does not work on your normal user account try to run the container as root.