A layered composite boot device, and a corresponding layered composite file system, can be implemented by a boot manager. Requests directed to the layered composite boot device and file system, can be serviced from a primary device and file system that are encapsulated by the layered composite boot device and file system. The primary device and file system can correspond to a virtualized file system within a container environment, thereby enabling changes within the container environment to affect early stages of operating system booting in the container environment. Should such requests not be serviceable from the primary layers, the composite device and file system can comprise secondary layers that can correspond to a container host connection and the host file system, providing fallback to existing data if changes within the container environment were not made, thereby enabling booting to proceed in a traditional manner.