UNIX
UNIX is a command line operating system written in the C programming language.
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UNIX has been around for almost 30 years. That maturity brings a stable, mature high-end operating system available for servers and supercomputers
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UNIX was conceived in the early 1970s by AT&T employees as an operating environment to provide services to software developers who were discouraged by the incompatibility of new computers and the lack of development tools for application development.
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After AT&T was forced to abandon commercial computing as part of an
antitrust settlement, AT&T’s UNIX was made available for free to the academic community.
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Because UNIX had been designed in a way that made it easy to “port” (move) to new
hardware, colleges and universities that
switched to UNIX were able to run a single operating system on all of their computers, even if their computers came from multiple manufacturers.
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Programmers at the University of
California at Berkeley made significant modifications to the original source
code and called it BSD (Berkeley Software Distribution) UNIX.
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They sent this new version of the UNIX environment to other programmers around the country, who then added tools and
code as they saw fit. Possibly the most important advance made to the software by the programmers at Berkeley was the addition of networking software which
allowed the operating system to function in a local area network (LAN).
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Sun Microsystems original version of UNIX, the Sun operating system was
based on BSD UNIX Version 4.2. At that time, AT&T’s version of the UNIX
environment was known as System V. In 1988, Sun OS/BSD, AT&T System 3, and XENIX were combined into what became System V Release 4 (SVR4).
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This new generation of the
operating system was an effort to combine the best features of both BSD and AT&T UNIX and create a kind of industry standard for the
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This enabled software to be
developed for UNIX without concern as to whether it was System V or BSD 4.2. The new SVR4 became the basis for not only Sun and AT&T versions of the UNIX environment, but also IBM’s AIX, and Hewlett-Packard’s HP-UX.
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One of the things that UNIX systems are famous for is the interoperability
they offer based on what some people have called the universal technical
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UNIX is particularly desirable as a server platform for client/server
computing because of the large range of platform sizes available and the huge base of application and development software available.
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Eventually UNIX spread into the business community, and pushed aside almost all
proprietary mainframe and minicomputer operating systems.
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Even IBM and DEC ended up offering their own versions of
UNIX as well as their proprietary operating systems.
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UNIX people are pretty fanatical when it comes to support of their
favorite operating system, and there is pretty much only one way of
doing things—their way or the highway.
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The UNIX file system (UFS) controls the way that information in files and directories is stored on disk and other forms of secondary storage. It
controls which users can access what items and how. The file system is therefore one of the most basic tools for enforcing UNIX security on your system.
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A shell is an interface between the user and the kernel. It acts as an
interpreter or translator. In other
words, the shell accepts commands issued by you, interprets these
commands, and executes the appropriate programs.
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Three shells are available
in the typical UNIX
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1) Bourne shell ($) – The default shell
for the typical UNIX computing
environment. The Bourne shell was developed for the AT&T System V.2 UNIX environment. It is typically used by system administrators.
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2) Korn shell ($) – A superset of the
Bourne shell. It has many of the Bourne shell features plus added
features. This is the industry standard for normal system users.
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3) C shell (%) – A shell based on the C
programming language. Like the Korn shell, it has additional features such as aliasing and history. C shell was
developed by Sun’s Bill Joy for programmers, but is used with
increasing frequency by normal system users.
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Following are some of the networking advantages that UNIX Servers offer:
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Telnet
Administrators can Telnet into a remote host to perform routine administrative tasks. The
administrator does not have to be sitting in front of the computer that requires the attention. This is
also a cost savings, because a UNIX machine can be operated headless, without a keyboard or a
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Performance
UNIX provides faster read/write operations than other operating systems. UNIX computers tend to operate for months or years without the need of a reboot. Crashes are rare. The number of
reboots forced by configuration changes are minimal in a UNIX environment.
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Hardware
Because the hardware has a longer life in the UNIX world, more drivers tend to be available and the
network cards and other peripherals can be used for a longer period of time. This minimizes the
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Automating Processes
UNIX/Linux administrators are able to automate many of the processes of the
operating system and of the applications by making use of shell scripting. A shell script is a program that the administrator can write to automate certain administrative tasks.
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Scalability
Mainstream UNIX systems can take
advantage of multiple motherboards that can handle from 2 to over 100 processors. High availability of these systems makes for almost 100% uptime.
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Sun Microsystems was the first company to use a windowing
environment in conjunction with the UNIX operating system. In 1993, a
consortium of UNIX platform vendors was formed to develop an integrated, standard, and consistent graphical
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Hewlett-Packard, IBM, Novell, and Sun Microsystems, along with many other companies and members of the OSF (Open Software Foundation),
X/Open, and the X Consortium all
came together to develop the Common Desktop Environment or CDE.
The Common Desktop Environment (CDE):
Is a graphical user interface (GUI) between the user and the operating system
Provides built-in menus for users to select and run utilities and programs without using Solaris 7
environment commands
Enables users to control multiple documents or applications on the screen at the same time
Controls activities in windows using both the mouse and the keyboard
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The Common Desktop Environment (CDE) is part of the Common Operating System
Environment (COSE, pronounced "cozy") agreement, one of many attempts at unifying the UNIX market. Although COSE itself never took off, CDE has achieved some
success--most notably, all the major UNIX vendors
agreeing on the Motif interface as the basis for the Common Desktop Environment.
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Despite its numerous advantages as a desktop and server operating system, UNIX never has been widely accepted in the general corporate world that
favors DOS/Windows and Novell's
NetWare. A key drawback to UNIX in the corporate arena has been the lack of a single UNIX standard.
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Although Windows dominates the
corporate desktop, UNIX is still widely used as a server platform due to its strong performance and robust features.
Business-critical servers must be able to deliver high-end features and run the
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UNIX has a well established position as the operating system of choice for distributed
relational databases from vendors like Informix, Ingres, Oracle, and Sybase. Most of these
vendors, however, will port their products to Windows NT as well. Any effort to reduce the problems associated with the multiple UNIX variants will do much to bolster the stature of UNIX as a worthwhile alternative to Windows NT.
