this question always comes up. I personally think the status quo is pretty weak here. I have certainly added a gdb stub to a unikernel before, but that apparently given that it was never used it wasn't the right answer.

people always talk about losing the excellent debugging facilities that linux gives you. if a service crashes in a big cloud environment what is that you do now that works so well. do you think its intractable to implement that in a single-process kernel?

I don't know if anything like this has been built, but I'd imagine you could have the hypervisor capture stack traces / log buffers / core dumps when a unikernel VM crashes.