Fixing ‘Unable to Locate Package’ Error When Downloading ROS Melodic on Ubuntu 20.04

In this article, we will discuss a common issue encountered by many users when they try to install the Robot Operating System (ROS) Melodic on Ubuntu 20.04 LTS – the ‘Unable to locate package’ error. We will delve into why this issue arises and provide a step-by-step guide on how to resolve it.

Understanding the Issue

The ‘Unable to locate package’ error typically occurs when the system cannot find the package you are trying to install in its repositories. In this case, the problem arises due to a compatibility issue. ROS Melodic is designed to work with Ubuntu 18.04 LTS, not Ubuntu 20.04 LTS. The version of ROS that is compatible with Ubuntu 20.04 LTS is ROS Noetic.

Solution 1: Installing ROS Noetic

The simplest solution to this problem is to install ROS Noetic instead of ROS Melodic. Here’s how you can do it:

1. Configure your Ubuntu repositories Ubuntu needs to be configured to allow “restricted,” “universe,” and “multiverse.” You can do this from the Ubuntu Software Center under the “Software & Updates” setting.
2. Set up your sources.list You need to allow your system to accept software from packages.ros.org. Open your terminal and input the following command:

   sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'

3. Set up your keys Next, use the following command to set up your keys:

   curl -s https://raw.githubusercontent.com/ros/rosdistro/master/ros.asc | sudo apt-key add -

4. Installation First, make sure your Debian package index is up-to-date:

   sudo apt update

   Then, install ROS Noetic using the following command:

   sudo apt install ros-noetic-desktop-full

   The ros-noetic-desktop-full package includes ROS, rqt, rviz, robot-generic libraries, 2D/3D simulators, navigation, and 2D/3D perception.

You can find more detailed instructions on the official ROS wiki.

Solution 2: Using a Virtual Machine

If your project specifically requires ROS Melodic, you can install it on a virtual machine or a separate system running Ubuntu 18.04 LTS. This way, you can work with ROS Melodic without running into compatibility issues.

Solution 3: Modifying Repository Configuration Files

Another option is to modify the repository configuration files to force the installation of ROS Melodic on Ubuntu 20.04 LTS. However, this method is not officially supported and could lead to other problems. Proceed with this option at your own risk.

Conclusion

The ‘Unable to locate package’ error when trying to install ROS Melodic on Ubuntu 20.04 LTS is primarily due to a compatibility issue. The recommended solution is to install ROS Noetic, which is compatible with Ubuntu 20.04 LTS. If you specifically require ROS Melodic, consider using a virtual machine running Ubuntu 18.04 LTS or modifying the repository configuration files. Always remember to follow the official guidelines and recommendations to avoid potential issues.