But those libraries will not perform all the functions you would normally expect an OS kernel to perform.
In the Unikernel, no operating system exist and the Xen play the role of OS. Is it true?
"It depends.”
What do you mean by the operating system?
In terms of functionality, for a unikernel system, much of the functionality you would usually rely on the operating system to perform (in most cases, by a kernel) is provided by library code (unikernels — certainly Mirage OS — are strongly inspired by library operating systems). But not all — if you are using Xen as your host environment then yes, Xen will provide some of that functionality as well.
The Xen hypervisor can do anything that an OS kernel do???
I don’t think that’s a well-formed question — first, you probably need to declare what an OS kernel can do.
The source of photo is:
Can you show me a clear and better diagram about Unikernel?
Well, it depends what you want the diagram to help explain. I don’t have any to hand right now.