What is Linux?
Linux is a 32-bit operating system that was initially created as a hobby by a young student, Linus Torvalds, at the University of Helsinki in Finland. Linus had an interest in Minix, a small UNIX system, and decided to develop a system that exceeded the Minix standards. He began his work in 1991 when he released version 0.02 and worked steadily until 1994 when version 1.0 of the Linux Kernel was released.
The kernel, at the heart of all Linux systems, is developed and released under the GNU General Public License and its source code is freely available to everyone.
Linux is a version of the UNIX operating system that has become very popular over the last several years
Linux (often pronounced LIH-Nuhks with a short "I") is a Unix-like operating system that was designed to provide personal computer users a free or very low-cost operating system comparable to traditional and usually more expensive Unix systems. Linux has a reputation as a very efficient and fast-performing system.
Linux is a remarkably complete operating system, including a graphical user interface, an X Window System, TCP/IP, the Emacs editor, and other components usually found in a comprehensive Unix system.
Unlike Windows and other proprietary systems, Linux is publicly open and extendible by contributors. Because it conforms to the Portable Operating System Interface standard user and programming interfaces, developers can write programs that can be ported to other operating systems
Why Linux is so popular?
Linux is as much a phenomenon as it is an operating system. To understand why Linux has become so popular, it is helpful to know a little bit about its history. The first version of UNIX was originally developed several decades ago and was used primarily as a research operating system in universities. High-powered desktop workstations from companies like Sun proliferated in the 1980s, and they were all based on UNIX. A number of companies entered the workstation field to compete against Sun: HP, IBM, Silicon Graphics, Apollo, etc. Unfortunately, each one had its own version of UNIX and this made the sale of software difficult. Windows NT was Microsoft's answer to this marketplace. NT provides the same sort of features as UNIX operating systems -- security, support for multiple CPUs, large-scale memory and disk management, etc. -- but it does it in a way that is compatible with most Windows applications.
The entry of Microsoft into the high-end workstation arena created a strange dynamic. The proprietary operating systems owned by separate companies and the lack of a central authority in the UNIX world weaken UNIX, but many people have personal problems with Microsoft. Linux stepped into this odd landscape and captured a lot of attention.
The Linux kernel, created by Linus Torvalds, was made available to the world for free. Torvalds then invited others to add to the kernel provided that they keep their contributions free. Thousands of programmers began working to enhance Linux, and the operating system grew rapidly. Because it is free and runs on PC platforms, it gained a sizeable audience among hard-core developers very quickly. Linux has a dedicated following and appeals to several different kinds of people:
• People who already know UNIX and want to run it on PC-type hardware
• People who want to experiment with operating system principles
• People who need or want a great deal of control over their operating system
• People who have personal problems with Microsoft
In general, Linux is harder to manage than something like Windows, but offers more flexibility and configuration options.
Following are the advantages of Linux
1. Portability: Means to modify a program from one computer system so that it work with different system. About 90% of code in current version of Linux is written in c language and remainder in assembly language. Linux is there fore a potable operating system as it can be easily modified.
• Multitasking:
It is an operating system that can do more than one thing at a time. Linux allows user to run as many process as it can handle. User can run several commands in background while executing another in fore ground.
• Multi-user:
An operating system that can be used by more than one person at a time, sharing resources, file space, printer and soon Linux support from one to 2000 users at a time.
• Job control: It is ability to control which job is executed in fore ground, back ground or is suspended.
• File system: It has tree like structure. It start with one directories called root, symbolized by / , has multiples directories under it. Storage space for different user files are maintained by operating system. Files can be protected by unauthorized users.
• Pipes: It is Linux file that take output of one process and provide it as input to next process. While executing and multiple Linux command pipes may be used between command to create what is referred to as pipe line command.
• Linux shell: User interaction with Linux is controlled by shell, a powerful command for interpreter. When user interact with shell search for program, if found, executes it.
• Visual shell: These is menu-driven and provide command for file management, text processing and electronic mail.
• Linux utilities: It include 100 utility program for function like sorting data, processing text and searching for information.
• System Security
There is several level of security in Linux. The First level is system security the standard login procedure be force Linux start running on the system which stopped the illegal user to start the windows. 2nd level security is file system security. So every user uses its own set of files and third level security allow user to encrypt the data files on the disk.
• Linux Maturity
Linux is solid and time tested operating system that has been in use over 25 years. Software is free form bugs and has high level of reliability of its capability.
Linux connection:
Hosts and Terminal:
As Linux is multi-user system, so there is one computer while is shared by all the user. This main computer is called host and does most of work. In order to use Linux system, you need to connect to the host computer. Each such connection is called a session. Linux may be supporting more than one session at same time. The device that you use to do your work is called terminal. A terminal consists of display and keyboard along with associated electronics. These terminals are connected to host by cables or over telephone lines.
Server and Client:
Most networks have one or more computer that share resources thought the network. Such nodes are called servers. A server provides a server to the network server can provide following types of servers.
File server: A server on network that provides file storage, e.g. sharing of files among different users with one hard disk.
Printer server: A Server on network that provides access to a printer. If more than one user want to print and printer is connected to server than all users printing is managed by server.
Communication Server: A server on network that provide access to modems.
Clients:
When your computer makes use of shared resources, we speak of your computer as the client, for e.g. you are using Linux workstation that is connected to Linux network. Your computer has its own hard disk on which you store some of your files, for e.g. one of other computer on network, a file server, has very large hard disk on which you keep the rest of your files. When you use files on your own computer the network is not involved, but when you access files as another computer, you are sharing resources of network. At such times, your computer is client and other computer is server. If some one at another computer needs to use files on your computer than, from their point of view, their machine is client and yours is the server.
Architecture of Linux Operating System or Components
Linux has all the components like a typical operating system as under.
Kernel:-
The Kernel (Basically in raw binary form that is laded directly into memory at time of startup) is the central part of Linux Operating System.
The Linux Kernel includes device driver supports for a large number of PC Hardware devices (graphic cards, Network Cards, Hard Disk etc), advanced processor and memory management feature , and supports for many different types of file system including dos floppies and iso9660 standard for CD ROMs.
The Shell and GUIs:
The Shell Surrounds the Kernel and provides the Linux user interface. As Linux Supports two form of command input. Through textual command line shells like that Bourne shell and CSH the C shell. The second type of interface is graphical interface (GUIs) such as KDE and GNOME windows Manager.
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