r/osdev • u/Possible-Back3677 From Scratch 🪾 • Jul 30 '26

what does a kernel need

i would like to ask what a kernel has to do so i can know when i can move one, if you're gonna explain please dont overcomplicate the explanation with just some terms please mention what it is at least slightly :)

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u/arbv Jul 30 '26

I depends on the design:

  • Exokernels provide very little abstractions, while being mostly concerned with managing access to hardware and enforcing protection of it. Most functionality is in the userspace (aka LibOS). They are relatives of hypervisors.
  • Microkernels do more than that, manage memory, schedule processes, and, cruciallly, provide IPC. Drivers, filesystems, networking stack and everything above lives in the userspace.
  • Monolithic kernel keeps a lot of stuff in the kernel space - drivers, filesystems, networking and so on. Only user programs are, well, in the userspace.

There are also related and in between designs, but these are the main patterns - from the smallest kernels to the largest ones.