On Linux, software is divided into two realms. The first realm, kernel space, is a privileged space that has visibility of the entire system. On some systems, this is also known as the supervisor mode. The other realm, user space, is an unprivileged space backed by hardware. It has a limited visibility of the entire system. All hardware access is done through the Linux API. Attempts to increase visibility beyond what the Linux API allows will result in a fault or at least an error. All the exercises up to this point have been exclusively in the user space. One important detail to note is that the system software or distributions include both kernel and user space components. Kernel space is exclusively in the Linux kernel and everything else is user space.

The distinction between user space and kernel on the BeagleBone is very important. The kernel is aware of the differences in hardware. A few things that the kernel is aware of are as follows...