UNIX

JIN GUO 08/30/00

AGENDA1. Creation of Unix2. Unix Uniqueness3. Unix Architecture4. Unix Application5. Unix Security6. Unix & Web

Creation of Unix

• What is UnixUnix is a computer operating

system, a control program

that works with users to run

programs, manage resources,

and communicate with other

computer system.

• Unix CreationIn late 1960s, Ken Thompson fromBell Labs wrote a computer gameon PDP-7, he started with animplementation of an earlier filesystem, then added processes,simple file utilities and commandinterpreter which he called a“shell”. Hence, he created systemnamed “Unix” , however, Unixdeveloped by more and more

programmers in the past decades.

Unix Uniqueness

• Multitasking Capability

• Multiuser Capability

• Multichoice System

• System Portability

• Application Libraries

Multitasking

• Unix allows users to do several things at once, such as printing out one file while the user edits another file.

• This is a major feature for users, since users don’t have to wait for one application to end before starting another one.

Multiusers

• Unix allows several users to access the same document by compartmentalizing the document so that the change of one user don’t override the change another user.

• Unix can take the commands of a number of users---determined by the design of the computer—to run program, access file, and print documents at the same time.

Multichoice System

• Microsoft MS-DOS and the Apple Macintosh interface are easy to use as both of them are designed to give the users less power, both have fewer command

• Unix is a multichoice system, as an example, Unix has three different types of

shell.

System Portability

• Unix can be moved from one brand of computer to another with a minimum of code change

• Unix can be upgraded without having all the customer’s data inputted again, and new version of Unix were backward compatible with older version

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Application Libraries

• From Bell Labs to the universities, every computer programmer worth his or her own salt started developing programs for Unix

• Today there are hundreds of Unix applications that can be purchased from third-party vendors, in addition to the applications that come with Unix

Unix Architecture(Chart)

K ern e l S h e ll Too ls & A p p lica tion s

U N IX

Unix Architecture

• The Kernel controls the hardware and turns part of the system on and off at the programmer’s command. If you ask the computer to list all the files in a directory, the kernel tells the computer to read all the files in that directory from the disk and display them on your screen

• The Shell -- 3 major types of shell: Bourne Shell, C Shell,

Korn Sell; The purpose of the shell is to act as an interpreter between the user and the computer.

• Tools& Applications There are hundreds of tools available to Unix users, and tools are grouped into categories for certain functions, such as word processing, business applications or programming

Unix Applications

• Productivity and office applicationsUnix has abandoned productivity applications to the PC world. Computers sold in

local stores don’t run on Unix

• Small database and client-server applications –Many competitors fight in this market, such as Windows NT, Unix, IBM’s AS/400 etc. Unix competes here using database products that are ODBC-enabled, use Java and Web technology and have better management tools for widely dispersed situation

• Small technical applications• Large commercial applications and database Unix is powerful in this market

• Large technical applications

Unix Security

There are many choices available to assist in strengthening security of Unix, examples are as follows:

• Tripwire tool is used to detect unauthorized changes at a file/directory level. It can manage and track changes to key system files by maintaining an information database for the specified files.

• Sudo utility lets the administrator delegate root authority to users without sharing the root password.With Sudo, the system administrator can permit access to only a small set of commands based on the role performed by a user.

• ssh shell is the preferred tool for remote access to system resource by many system administrators today. ssh uses public-key crytography to establish a secure channel of communication over public networks such as the Internet.There is a server side and a client side to ssh.

Unix & Web

• During these years, it was widely reported that Windows NT was expected to bludgeon Unix into the OS oblivion.Is that true?

• It is not likely.Using Apache as an indicator of the Unix presence on the web and Microsoft’s Internet Information Server(IIS) for NT to compare, the statistics shows that Apache increased sales from 15,797 server sites in 1996 to more than 827,000 in 1999, while IIS from no presence in 1996 to more than 381,000. Keep in mind these Apache servers are only a fraction of the total number of Unix servers on the web.

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