Extend two or more overlay

Extend your project with two or more overlay and define priority for each.

Before starting, it's important to remember that a Kom project is equal to a Overlay as OpenEmbedded; you can add recipes, images, machine's configuration, distro's configuration, etc..
All this files and directories are part of project. A user can publish it as a complete overlay. Other users can, for example, extend his project's overlay. In other words, someone can use your recipes, images, machine's configuration, distro's configuration in his project as you use OpenEmbedded Overlay.
Moreover, the project has a private directory build which contains configuration to build your personal image and packages, and all the results of building.

In another lesson, you can find how configure Kom to find the new overlays installed in your system and configure your project to use it. Summary of lesson in two command:

  • Only the first time, when you have installed a new overlay. To configure Kom to find foobar overlay:
    kom -o foobar /path/to/foobar
  • To configure your project to use foobar overlay:

    This operations should be done for all overlay

    kom -a foobar

Now, to view what overlay use my project:

kom -L

This is a example of project which uses two extra overlay: OpenEmbedded (oe) and foobar:

Extend overlays

All overlay are identified by a ID. This ID is used by Kom to associate an overlay with its path. Moreover, all overlay have a number associated. This number represents the priority where the overlay with the highest value is taken into account with priority than that with lower one.

To understand what is the priority, you imagine to have your modified version of console-image.bb recipe which you save in your recipes directory in /path/to/yourproject/recipes/images. If you start bitbkake console-image command, bitbake uses your recipe instead OpenEmbedded's overlay version because project's overlay has the higher priority than other.

Note: The last row in figure identifies project's overlay. It has always the higher priority and Kom can't modify it.
This means that first bitbake search configuration / recipes / images in your project and then in overlay extended.

Modify priority is very simple. Just a command to execute.
To decrease overlay's priority:

kom -d [overlay_id]

To increase overlay's priority:

kom -D [overlay_id]