Apart from disassembling the machine code, assuming one could even attach a debugger to such an application, how would you debug a unikernel application in production?
Just like debugging Java and .NET applications running bare metal on production.
By having a rich runtime (kernel) that exposes the internals to the world, like Mission Control, TraceViewer and the respective debuggers, when the right set of flags/authentication are enabled.
Unikernel are no different from running embedded applications, bare metal.
I know they are no different since they are one and the same. Now imagine your unikernel application is running inside of a vehicle and there is a bug in the head-up display code. Without re-inventing DTrace and kdb from Solaris / illumos from scratch, how would you debug your unikernel application in order to find and even fix the bug? (With kdb, it can be done on the fly.)
Inside of a vehicle, not yet; production example, yes.
Back in the day, there was a kernel bug which prevented Solaris 10 installer from booting on systems with a Pentium III processor. The workaround was to boot the kernel with -k, let it crash and drop into kdb, then patch a certain kernel structure and drop out of the debugger, continuing execution. The same mechanism would work in a car or a Boeing 787, which I understand were actually running Solaris as the control & navigation system.
