Hardware Reference
In-Depth Information
When the kernel has finished loading, it automatically runs a program called init.
This program is designed to finish the initialization of the Raspberry Pi, and then
to load the rest of the operating system. This program starts by loading all the
daemons into the background, followed by the graphical user interface.
Daemons
A daemon is a piece of software that runs behind the scenes to provide the operating
system with different features. Some examples of a daemon include the Apache web
server, Cron, a job scheduler that is used to run programs automatically at different
times, and Autofs, a daemon that automatically mounts removable storage devices
such as USB drives.
A distribution such as Raspbian needs more than just the kernel to work. It also
needs other software that allows the user to interact with the kernel, and to manage
the rest of the operating system. The core operating system consists of a collection
of programs and scripts that make this happen.
The shell
After all the daemons have loaded, init launches a shell. A shell is an interface to
your Raspberry Pi that allows you to monitor and control it using commands typed
in using a keyboard. Don't be fooled by this interface, despite the fact that it looks
exactly like what was used in computers 30 years ago. The shell is one of the most
powerful parts of Raspbian.
There are several shells available in Linux. Raspbian uses the
Bourne again shell
(
bash
) This shell is by far the most common shell used in Linux.
