Operating System - Linux
Linux
is one of popular version of UNIX operating System. It is open source as its
source code is freely available. It is free to use. Linux was designed
considering UNIX compatibility. Its functionality list is quite similar to that
of UNIX.
Components of Linux
System
Linux Operating System has primarily three components
· Kernel −
Kernel is the core part of Linux. It is responsible for all major activities of
this operating system. It consists of various modules and it interacts directly
with the underlying hardware. Kernel provides the required abstraction to hide
low level hardware details to system or application programs.
· System
Library − System libraries are special functions or programs using which
application programs or system utilities accesses Kernel's features. These
libraries implement most of the functionalities of the operating system and do
not requires kernel module's code access rights.
· System
Utility − System Utility programs are responsible to do specialized, individual
level tasks.
Kernel Mode vs User Mode
Kernel component code executes in a special privileged mode
called kernel mode with full access to all resources of the computer.
This code represents a single process, executes in single address space and do
not require any context switch and hence is very efficient and fast. Kernel
runs each processes and provides system services to processes, provides
protected access to hardware to processes.
Support code which is not required to run in kernel mode is in
System Library. User programs and other system programs works in User Mode which
has no access to system hardware and kernel code. User programs/ utilities use
System libraries to access Kernel functions to get system's low level tasks.
Basic Features
Following are some of the important features of Linux Operating
System.
· Portable −
Portability means software can works on different types of hardware in same
way. Linux kernel and application programs supports their installation on any
kind of hardware platform.
· Open
Source − Linux source code is freely available and it is community based
development project. Multiple teams work in collaboration to enhance the
capability of Linux operating system and it is continuously evolving.
· Multi-User −
Linux is a multiuser system means multiple users can access system resources
like memory/ ram/ application programs at same time.
· Multiprogramming −
Linux is a multiprogramming system means multiple applications can run at same
time.
· Hierarchical
File System − Linux provides a standard file structure in which system
files/ user files are arranged.
· Shell −
Linux provides a special interpreter program which can be used to execute
commands of the operating system. It can be used to do various types of
operations, call application programs. etc.
· Security −
Linux provides user security using authentication features like password protection/
controlled access to specific files/ encryption of data.
Architecture
The following illustration shows the architecture of a Linux
system −
The architecture of a Linux System consists of the following
layers −
· Hardware
layer − Hardware consists of all peripheral devices (RAM/ HDD/ CPU etc).
· Kernel −
It is the core component of Operating System, interacts directly with hardware,
provides low level services to upper layer components.
· Shell −
An interface to kernel, hiding complexity of kernel's functions from users. The
shell takes commands from the user and executes kernel's functions.
· Utilities −
Utility programs that provide the user most of the functionalities of an
operating systems.
