Dependencies for building packages
Up to now you have installed what you need to run the core ROS packages. To create and manage your own ROS workspaces, there are various tools and requirements that are distributed separately. For example, rosinstall is a frequently used command-line tool that enables you to easily download many source trees for ROS packages with one command.
To install this tool and other dependencies for building ROS packages, run:
sudo apt install python-rosdep python-rosinstall python-rosinstall-generator python-wstool build-essential
Before you can use many ROS tools, you will need to initialize rosdep. rosdep enables you to easily install system dependencies for source you want to compile and is required to run some core components in ROS. If you have not yet installed rosdep, do so as follows.
sudo apt install python-rosdep
With the following, you can initialize rosdep.
sudo rosdep init rosdep update