In order to accomplish the dependency, the recipes must declare what they need to have available during the build process. BitBake ensures that the build-time dependencies are satisfied before starting the recipe build. This is easier to understand if we think about an application that uses a library. So, this library must be built and its headers made available for use, before the application itself can be built. The DEPENDS variable is used in a recipe to inform BitBake about the build-time dependency.

When an application depends on something to run, this is called a runtime dependency. This is common for shared data among applications (for example, icons), which is used only when running the application but not used during its build process or when an application calls another during its execution. The runtime dependencies can be expressed using the RDEPENDS variable in a recipe.

With the recipe dependencies chain, BitBake can sort all the recipes in a feasible order for the...