ROS2 vs ROS1 Overlay Workspace

In ROS1, the structure of an overlay workspace, called the catkin workspace, looks like this:

workspace_folder:
|--src
   |--CMakeLists.txt
   |--package_1_folder
   |--
   |--package_n_folder
|--devel
|--build
|--install

The catkin workspace is built by running “catkin_make” command. To rebuild a catkin workspace, simply delete all the folders inside the workspace but the “src” folder and subsequently run the “catkin_make” command.

For a detailed description, please consult the following documentation: http://wiki.ros.org/catkin/workspaces

In ROS2, the structure of an overlay workspace looks like this:

workspace_folder:
|--src
   |--package_1_folder
   |--
   |--package_n_folder
|--build
   |--COLCON_IGNORE
   |--package_1_folder
   |--
   |--package_n_folder
|--install
   |--COLCON IGNORE 
   |--files: setup.bash, local_setup.bash, etc
   |--package_1_folder
   |--
   |--package_n_folder
|--log

Building command

To build a ROS2 workspace, use the following command:

colcon build --symlink-install

To rebuild a ROS2 workspace, simply delete all the folders inside the workspace but the “src” folder and subsequently perform the “colcon build” command.

If there are already a large number of packages inside your workspace, running the command above may take a long time to complete. Instead, you can only build the package(s) that has not been built yet by using the following command:

colcon build --packages-select [PACKAGE_NAME]