Unix

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  • Topic: File system, Unix, File system permissions
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  • Published : February 24, 2013
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UNIX is a computer Operating System which is capable of handling activities from multiple users at the same time. Unix was originated around in 1969 at AT&T Bell Labs by Ken Thompson and Dennis Ritchie. This tutorial gives an initial push to start you with UNIX. For more detail kindly check tutorialspoint.com/unix

What is Unix ?
The UNIX operating system is a set of programs that act as a link between the computer and the user. The computer programs that allocate the system resources and coordinate all the details of the computer's internals is called the operating system or kernel. Users communicate with the kernel through a program known as the shell. The shell is a command line interpreter; it translates commands entered by the user and converts them into a language that is understood by the kernel.

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Unix was originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna. There are various Unix variants available in the market. Solaris Unix, AIX, UP Unix and BSD are few examples. Linux is also a flavour of Unix which is freely available. Several people can use a UNIX computer at the same time; hence UNIX is called a multiuser system. A user can also run multiple programs at the same time; hence UNIX is called multitasking.

Unix Architecture:
Here is a basic block diagram of a UNIX system:

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The main concept that unites all versions of UNIX is the following four basics:

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Kernel: The kernel is the heart of the operating system. It interacts with hardware and most of the tasks like memory management, tash scheduling and file management. Shell: The shell is the utility that processes your requests. When you type in a command at your terminal, the shell interprets the command and calls the program that you want. The shell uses standard syntax for all commands. C Shell, Bourne Shell and Korn Shell are most famous shells which are available with most of the Unix variants. Commands and Utilities: There are various command and utilities which you would use in your day to day activities. cp, mv, cat and grep etc. are few examples of commands and utilities. There are over 250 standard commands plus numerous others provided through 3rd party software. All the commands come along with various optional options. Files and Directories: All data in UNIX is organized into files. All files are organized into directories. These directories are organized into a tree-like structure called the filesystem.

System Bootup:
If you have a computer which has UNIX operating system installed on it, then you simply need to turn on its power to make it live. As soon as you turn on the power, system starts booting up and finally it prompts you to log into the system, which is an activity to log into the system and use it for your day to day activities.

Login Unix:
When you first connect to a UNIX system, you usually see a prompt such as the following:

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login:

To log in:
1. 2. 3. 4. Have your userid (user identification) and password ready. Contact your system administrator if you don't have these yet. Type your userid at the login prompt, then press ENTER. Your userid is case-sensitive, so be sure you type it exactly as your system administrator instructed. Type your password at the password prompt, then press ENTER. Your password is also case-sensitive. If you provided correct userid and password then you would be allowed to enter into the system. Read the information and messages that come up on the screen something as below.

login : amrood amrood's password: Last login: Sun Jun 14 09:32:32 2009 from 62.61.164.73 [amrood]$ You would be provided with a command prompt ( sometime called $ prompt ) where you would type your all the commands. For...
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