The high level goal of Unikraft is to be able to build unikernels and specialized OSes targeted at specific applications, without requiring the time-consuming, expert work that building such systems requires today. Unikraft supports multiple platforms (e.g., Xen and KVM) and CPU architectures, meaning that if you are able to build an application in Unikraft, you get support for these platforms and architectures for “free”. Unikraft consists of three basic components:
- Library Pools are Unikraft modules, each of which provides a basic piece of functionality. Libraries can be arbitrarily small (e.g., a small library providing a proof-of-concept scheduler) or as large as standard libraries like libc.
- Configuration Menu. Inspired by Linux’s Kconfig sytem, this menu allows users to pick and choose which libraries to include in the build process, as well as to configure options for each of them, where available. Like Kconfig, the menu keeps track of dependencies and automatically selects them where applicable.
- Build Tool. Based on make, it takes care of compiling and linking all the relevant libraries, and of producing images for the different platforms selected via the configuration menu.
Unikraft libraries are grouped into two large groups: core libraries, and external libraries. Core libraries generally provide functionality typically found in operating systems. Such libraries are grouped into categories such as memory allocators, schedulers, filesystems, network stacks and drivers, among others. Core libraries are part of the main Unikraft repo which also contains the build tool and configuration menu.
External libraries consist of existing code not specifically meant for Unikraft. This includes standard libraries such as libc or openssl, but also run-times like Python.
Whether core or external, from a user’s perspective these are indistinguishable: they simply show up as libraries in the menu.