Posted on Jan. 9, 2010 by
pauls
When you first turn on your computer the BIOS kicks in and searches for
instructions on your master boot record or MBR. From there it is able to
locate the boot loader which in turn figures out which kernel to run and then
loads it into memory and that is the point you start actually running your
flavor of UNIX. At this stage your computer is just running a kernel and has
no interactivity or running services.
You are most likely used to using your computer to do something, and to do that, you need to run processes. While at this point you could have your computer launch a shell, you would still have a lot of setting up to do such as mounting hard drives, bringing up your network adapters, starting services, launching a GUI or what ever else you want to do. This is tedious and beyond the ability of most people so instead of running a shell the first process your computer runs is some kind of process manager. Traditionally this has been the init program which is the parent of every process that is executing.
Init is controlled by a handful of scripts that in turn ...