ROS Melodic + Ubuntu 18.04

Fetch Robotics has recently started supporting ROS Melodic and Ubuntu 18.04 on Fetch and Freight robots. Other than the process of upgrading a robot, there should be minimal effect on using your robot. If you observe an issue, please let us know via a support ticket.

Upgrading Your Robot to ROS Melodic + Ubuntu 18.04


Read this document in full to ensure you understand the procedures. It is not straightforward to go back to ROS Indigo/Ubuntu 14.04 after doing this. Ensure your colleagues are on board with doing this upgrade.

This document is a procedure for replacing the contents of your robot’s SSD with an Ubuntu 18.04 install and ROS Melodic.

Before Upgrade

Back up files from the robot! There are a few categories of files to back up:

  1. Calibration and other robot-specific files. By convention, these are all in /etc/ros/[indigo|melodic]/
  2. Files relating to your research work
  3. A record of what packages you installed for ROS Indigo
  4. Udev rules created for additional hardware (e.g. sensors) added to your robot
  5. Network hardware configuration (for troubleshooting)

Below, we assume that after logging into the robot (e.g. via ssh) you back up files to a machine named HOST with username USER.

For (1), we recommend doing:

tar -zcf fetch_robot_files.tar.gz /etc/ros/indigo/
scp fetch_robot_files.tar.gz USER@HOST:~/

For (2), this may include workspaces, logs, and training data. You might even want to back up the entirety of /opt/ros/indigo if you are unsure.

For (3), you can easily record the list of packages you installed via:

dpkg -l | grep ros-indigo > installed_indigo_packages.txt

As well, you might want to record what repositories are part of your workspaces.

For (4), such files are likely located in /etc/udev/rules.d/, and should be saved.

For (5), this file may be useful for reference if the install process doesn’t automatically set up networking on your robot correctly:

scp /etc/udev/rules.d/70-persistent-net.rules USER@HOST:~/$(hostname)_udev_net_rules

If you are using any additional hardware (sensors), be sure to record what network or other hardware configuration changes were made to get them working.

18.04 Install and Installing ROS/Fetch Packages


Back up your files as described in the previous section

  1. Runstop the robot, to avoid unexpected movement of the robot.
  2. Install Ubuntu 18.04 on the robot. Download the latest 18.04 Ubuntu installer from (in these instructions we use the Desktop image, version 18.04.2). For help booting from USB, see Accessing Boot Menu on Fetch Robots.
  1. We recommend keeping the same hostname for the robot, e.g. fetch4
  2. You can create the fetch user, or let it be automatically created later. (The typical password for the fetch user is ‘robotics’.)
  • After install, you may need to unblock apt. Do this by clicking the App Store icon on the sidebar, which should trigger an update prompt you can close: AppStore
  • You’ll probably want to install a few convenience packages such as openssh-server to enable SSH into your robot: sudo apt install openssh-server net-tools. You might also want to install your favorite commandline text editor.
  1. Update your Ubuntu install: sudo apt update && sudo apt dist-upgrade -y
  2. Install ROS Melodic by following the instructions on the ROS Wiki. You will want to do steps 1.1 through 1.6. In writing/testing these instructions, we assume:
  • You use the ROS-Base setup, via the ros-melodic-ros-base package.

  • You’re using bash, so step 1.6 for the fetch user is:

    echo "source /opt/ros/melodic/setup.bash" >> ~/.bashrc
    source ~/.bashrc

    You can also make this apply for all new users: sudo su -c 'echo "source /opt/ros/melodic/setup.bash" >> /etc/bash.bashrc'

  1. NOTE: at a later time, Fetch may host and recommend its own mirror of ROS Melodic debians.

  2. Run the following to install Fetch research debians:

    • General packages for Fetch robots:

      sudo apt install ros-melodic-fetch-calibration ros-melodic-fetch-open-auto-dock \
      ros-melodic-fetch-navigation ros-melodic-fetch-tools -y
    • Then install packages specific to the robot type:

      export ROBOTTYPE=$(hostname | awk -F'[0-9]' '{print $1}')
      # sudo apt install $ROBOTTYPE-melodic-config  # pending future availability
      sudo apt install ./$ROBOTTYPE-melodic-config.deb -y
  3. Power cycle the robot:

    sudo /sbin/reboot

Post-install Validation

This is a direct continuation of the previous section’s procedure. It is assumed that your robot is still runstopped.

Verify that things are working. All of the following steps assume that you are ssh‘d into the robot:

ssh fetch@fetchXXXX
  1. Verify that calibration is installed, e.g. a date should be output if you run the command below:

    fetch@fetch3:~$ calibrate_robot --date
    2018-11-26 14:48:04
  2. Verify that the robot can ping the mainboard and the laser:

    ping  # mainboard
    ping  # laser

    If not, see Ensuring robot’s ethernet ports are configured correctly

  3. Verify that the Primesense camera is working (if working with a Fetch robot):

    rostopic list head_camera | wc -l

    This should output 32, if everything is working fine.

  4. At this point, release the robot’s runstop button.

  5. The gripper should now have power, so we should be able to ping it:

    ping  # gripper
  6. The arm’s “gravity compensation” should now be working. You should be able to freely move the arm by hand.

  7. Check whether your PS3 controller pairs and controls the robot.

    Important note: The PS3 controller currently won’t work with ROS by default. To fix this, run sudo ln -s /dev/input/js0 /dev/ps3joy. We hope to fix this by fixing the corresponding udev rules eventually.

    Important note: for 18.04 the robots have switched from using sixad to using PS3joy. Some changes in behaviour you may see:

    • The LEDs on the PS3 controller may continually blink, even though it is connected.
    • Inputs may not be sent from the PS3 controller if the accelerometers in the controller do not detect motion. This can result in jerky motion when using the controller.

    We are hoping to determine fixes for these in the near future.

  8. At this point the robot is probably working fine and is ready for use! (Unless you have additional customizations to restore; see next step)

  9. If applicable, from your non-robot computer, restore the contents of /etc/ros/indigo to /etc/ros/melodic on the robot:

    scp fetch_robot_files.tar.gz fetch@fetchXXX:~/
    ssh fetch@fetchXXX
    sudo mkdir -p /etc/ros/melodic
    tar -xzf ~/fetch_robot_files.tar.gz /etc/ros/melodic/

    As well, you can restore any other saved files to the robot.

    This is the point at which some things may not work fully, e.g. if packages used in ROS Indigo need updates/replacements for ROS Melodic.

Compatibility of Other Computers Used with the Robot

For working with a robot running ROS Melodic, we recommend using an 18.04 Ubuntu machine that also has ROS Melodic installed.

  • In order for the robot to appear correctly in RViz, you will want to:
    • Ensure your computer is pointed at the packages.ros apt sources
    • Install ros-melodic-fetch-description and ros-melodic-freight-description packages. Addtionally you might want to install ros-melodic-fetch-tools.
    • Ensure that these packages are included in your path (e.g. rospack find fetch_description returns a path)
    • Common gotcha on a new setup: If the robot model doesn’t appear at first, you may want to change the “Fixed frame” from e.g. ‘map’ to ‘odom’.


Disk filling issue

Some robots may encounter an issue where Gnome3 fills the disk by spamming /var/log/syslog. This issue has a fix that is not available via apt yet, but can be manually done:

Ensuring robot’s ethernet ports are configured correctly

The robot has two ethernet ports on its computer. You can find more information on this at Computer Overview and Configuration.

The most likely problem you may encounter after getting 18.04 installed is if these two ports are “swapped”. This will cause the robot computer to be unable to talk to the rest of its hardware. You can fix this in software or in hardware:

  • Software: Edit /etc/udev/rules.d/70-persistent-net.rules and swap eth0 and eth1. Restart the robot for the change to take effect.
  • OR: Hardware: swap the two ethernet cables where they plug into the computer. This shouldn’t be needed, but in case you do, you should expect to find a gray cable (internal communications) and a blue cable (external). Typically, the blue goes to the top ethernet port, and the grey goes to the bottom.

Another issue you may encounter with 18.04 is if you are using the ethernet on the side access panel with a DHCP setup. In some setups, the ethernet port may fail to be assigned an IP automatically. We recommend consulting IT for help with this, if needed.

Accessing Boot Menu on Fetch Robots

You may need to access the boot menu in order to boot from a USB flash drive and install Ubuntu 18.04. Due to different computer motherboards used in the past, Fetch research robots may be using one of two BIOS flavors. Older robots use an MSI branded BIOS. Newer robots use American Megatrends Inc. (AMI).

These different BIOS types activate the boot media selection menu with different keys: - If your robot shows the MSI splash screen at boot, press F11 to access the boot menu. - If your robot shows the black AMI splash screen at boot (this lasts for about 1 second),

press F7 to access the boot menu.

If you fail to get into the boot menu, you can restart the computer and try again.