Once the kernel is loaded and the boot-code jumps to it, the kernel will initialize itself, trying to determine what hardware is present and so on, and then it needs to find a root filesystem.
Presently we support the following types of rootfilesystems:
This is the most normal type of root filesystem. It can reside on a floppy or on harddisk.
While this is technically possible, it isn't particular useful, because of ``FAT'' filesystems inability to make links, device nodes and such ``UNIXisms''.
This is actually a UFS filesystem which has been compiled into the kernel. That means that the kernel does not really need any disks/floppies or other HW to function.
This is for using a CD-ROM as root filesystem.
This is for using a fileserver as root filesystem, basically making it a diskless machine.