Userlevel checkpointing through exportable kernel state

Checkpointing, process migration, and similar services need to have access not only to the memory of the constituent processes, but also to the complete state of all kernel pro-vided objects (e.g., threads and ports) involved. Tradition-ally, a major stumbling block in these operations is acquir-ing and re-creating the state in the operating system. We have implemented a transparent user-mode check-pointer as an application on our Fluke microkernel. This microkernel consistently and cleanly supports the importing and exporting of fundamental kernel state safely to and from user applications. Implementing a transparent checkpoint-ing facility with this sort of kernel support simplifies the im-plementation, and expands its flexibility and power. 1