Package versioning is used to differentiate the same package in different stages of its lifecycle. From Poky's perspective, it is also used as part of the equation that generates the checksum used by BitBake to verify whether a task must be rebuilt.

The package version, also known as PV, plays a central role when we select which recipe to build. The default behavior of Poky is to always prefer the newest recipe version, unless there is an explicit different preference, as we discussed in Chapter 4, Grasping the BitBake Tool. For example, consider that we have two versions of the recipe myrecipe—myrecipe_1.0.bb and myrecipe_1.1.bb. BitBake, by default, builds the recipe with version 1.1.

Inside the recipe, we may have other variables that compose package versioning with the PV variable. These are package epoch, known as PE and package revision, known as PR.

The PE variable has a default value of zero and is used when the package version schema is changed, breaking...