UNIX (pronounced YEW-nihks) is an operating system that originated at AT&T's Bell Labs in 1969 as an interactive time-sharing system. Ken Thompson and Dennis Ritchie are considered the inventors of UNIX. UNIX originated when Ken Thompson, facinated with the game Space Travel, decided it would be easier to write an operating system for the DEC PDP-7 to run his game rather than to write a PDP-7 cross compiler on the lab's GE-645. UNIX inhereted features from MULTiplexed Information and Computer System (MULTICS), a project that Bell Labs, General Electric, and RAND were involved in. UNIX became popular in the labs and soon the source code was given away to Universities such as the west coast's University of California at Berkeley which developed the Berkeley Software Distribution (BSD) variant of UNIX.

     As you may already know, UNIX is not a single operating system; it refers to a family of operating systems which includes Linux, FreeBSD, NetBSD, OpenBSD, IBM's AIX, Hewlett-Packard's HP-UX, SGI's IRIX, SCO (UnixWare and OpenServer), Sun's SunOS and Solaris, Compaq/DEC's Tru64 UNIX, and Cray's UNICOS, just to name the more prominent ones. The two main variants of the UNIX versions are the SYSTEM V operating system distributions and the BSD operating system distributions.

     "If you’re a UNIX user, all UNIX are pretty much the same. If you’re a UNIX programmer, all UNIX are a little bit different. If you’re a UNIX system admin, all UNIX are completely different! That’s coming from ULTRIX, AIX, HP-UX, Solaris, and Digital UNIX experiences. Might as well count Linux, too." Bob Koehler, Hubble Space Telescope Payload Flight Software Team.

     Unix distributions come with multiple applications (command-line commands) that are considered part of the distribution. Many of these commands have a common syntax such as the "ls" command which lists directories. When an administrator decides to add a 3rd party application such as Apache, the installation process requires compilation as part of the installation. This makes the application available for most all Unix versions even though the compiled version may not run on another Unix variant without recompiling the application.
In general, a UNIX server is halted only in the following situations:

	o Due to a hardware failure, for instance, a hard drive fails;
	o A hardware upgrade needs to be performed;
	o A lengthy power outage has occurred and the backup power
	  supply resources have been exhausted;
	o The kernel is being upgraded.
Unix Summary

     Unix is most often used as network servers providing services throughout a specified network. Unlike conventional personal computer (PC) software such as Microsoft Windows, Unix systems are intended for multiple users running processes simultaneously on the same system. Unix systems are also designed to run without being rebooted unless power or hardware failures occur. There are Unix systems running today which have not been rebooted since before Microsoft released Windows NT 4.0. Unix is the type of environment you would see running CNC machinery, NASA equipment, etc.. Unix is also used as a workstation for CAD designing and large graphic work. Unix is used in graphics environments when, for instance, the US Geological Survey or NASA need giant maps that are terrabytes in size and hard to work on with conventional PC equipment and software.

     When logging into a Unix server as a user just learning what it is all about, you need to know a few things to help get you started. Unix is made up of a large amount of small utilities. Each utility is kept simple and each are designed not to do what another does. You use command combinations to use some of them at once, thus giving you powerful results with many ways to create script macros to always call a certain combination.

     Unix system configuration files are stored in the folder /etc. During the bootstrap, Unix looks here for scripts to configure itself. As other services, (daemons) are started, they will look in /etc for a configuration file often having the extension .conf for configuration, BSD variants also have files called rc.filename which are configuration files.

     Temporary data (ie c:\windows\temp) is kept in /tmp. Data which always changes sizes is kept in /var such as newsgroup data that changes daily. This is often a seperate partition to minimize fragmentation. Individual user information and home directories are stored in /home/username. Common programs or binaries are stored in /bin and root user or administrator binaries are stored in /sbin. Programs that did not come with the operating system (distribution) installed by default are put in the /usr folder. The /usr folder has a bin and sbin folder (/usr/bin and /usr/sbin).

DOS to Unix
	Dos command = Unix command (description)

	\    = /     (directory seperator, Unix is like a website URL)
	dir  = ls    (LiSt directory contents)
	type = cat   (type / conCATonate an ascii file to the console)
	cls  = clear (clear the console screen)
	cd   = cd    (Change Directory)
	del  = rm    (DELete / ReMove a file)
	ren  = mv    (REName / MoVe a file)
	md   = mkdir (MaKe DIRectory)
	rd   = rmdir (ReMove DIRectory)
	edit = pico  (Text editor, also vi, emacs)

	who   - who is logged into the system
	ps    - show running processes
	top   - continously show sorted running processes
	lynx  - text web browser (lynx www.google.com)
	exit  - exit shell (or session)
	man   - Unix MANual, shows a program's docs (ie. man ls)
	mail  - send/read email (mail user@isp.com)
	pine  - send/read email (pine user@isp.com)
	
	To list commands available on a system:

		ls /bin
		ls /usr/bin

	Use the more command to stop at a screenful of text. In this
	case, you have to "pipe" the data to the more command:

		ls /usr/bin | more

	More is available on DOS systems also and used in the same way.
	Unix also has less, which obviously derived it's name from the
	more command. It has the ability to scroll back up, and much more.

		ls /usr/bin | less

	To record the results of a command to a file, use the output
	redirect character >.

		ls /usr/bin > filename
		edit filename
     Using the Unix application "Samba", a Unix machine can emulate the domain authentication structure of the Windows NT Server, thus allowing Windows based workstations to work seamlessly on a Unix Network Operating System. "Samba 2.0 has been benchmarked using the Ziff-Davis NetBench (R) benchmarking suite, as the world's fastest Windows server, achieving 193 megabits per second file serving performance on a Silicon Graphics (R) Origin 200 (R) server with 60 Windows clients."

"UNIX IS user friendly - it's just selective about who it's friends are."