Well, actually I know what the process is, but I could not figure out why I cannot list it by ps command or I did something wrong with it.

As you may know, it should be "sched". But when you go to find all processes running, you will get "init" as the first one (PID=1, PPID=0)

The command you may use:
ps -ecl  [or ps -p 0 -l]
I would appreciate if anyone could give me the light why "sched" was not show up on ps command on Linux. I was already logged on as a root, but I still got no luck finding it. I had tried with Mac OS X Leopard, the same thing happened here [no PID 0 process, starting with init as PID 1] However, on FreeBSD & Windows, I got it fairly easy.