When subscription information is included in an image build, a systemd service is created to run on first boot in order to activate the system [1]. The same service can be used to enable any layered repositories (using the appropriate content label) that the user selected.

To propagate the labels to the pipeline generator code, they can be added to the subscription image options [2], which get copied to the OSCustomizations for the OS pipeline [3].

[1] https://github.com/osbuild/images/blob/15a7527e5745154c1e39245f2b29e7e7b46aaa78/pkg/manifest/subscription.go#L89
[2] https://github.com/osbuild/images/blob/15a7527e5745154c1e39245f2b29e7e7b46aaa78/pkg/customizations/subscription/subscription.go#L11-L22
[3] https://github.com/osbuild/images/blob/15a7527e5745154c1e39245f2b29e7e7b46aaa78/pkg/distro/generic/images.go#L282