Linux Architecture

The Linux operating system is composed of four major subsystems: Hardware, Kernel, Shell and user interface.

There are two important parts one is Kernel and other is Shell. The Kernel interacts with the machine's hardware and the Shell interacts with the user.


1. User Applications
The set of applications in use on a particular Linux system will be different depending on what the computer system is used for, but typical examples include a word-processing application and a web-browser. The user program or application that needs to access the hardware use the services of Kernel. These programs access the kernel through a set of function called System Calls.

2. O/S Services (Shell)

These are services that are typically considered part of the operating system (a windowing system, command shell, etc.); also, the programming interface to the kernel (compiler tool and library) is included in this subsystem. In Linux Shell is a command interpreter that handles the outer part of operating system. It is interface between user and kernel. There could be many shells that run on a system, but there is only one running kernel in a system.

3. Linux Kernel

Kernel is the core component of Operating System; it interacts directly with hardware and provides low level services to upper layer components. Kernel is loaded into memory when system is booted and communicates directly with hardware. Kernel also do the other job like manages schedule processes, systems memory, deciding the priority and other task.

4. Hardware Controllers

This subsystem is comprised of all the possible physical devices in a Linux installation; for example, the CPU, memory hardware, hard disks, and network hardware are all members of this subsystem. 

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Fig : Linux Architecture

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