What is Unity
Unity is a distributed computing environment available to NC State faculty,
staff, and students. A distributed computing environment provides users with access to an
ever-increasing wealth of resources, such as software applications, electronic
resources on the Internet, and other hardware and software (such as printing and disk
space).
Distributed computing means that your computing power comes from several powerful
servers that are centrally located or remotely distributed across campus.
In the Unity environment, you have a network of workstations running the unix
operating system, the Athena Software (from MIT), and the Andrew File System
(AFS).
The Unity realm uses the client-server model for interaction between
workstations. A client is usually the user's machine that sends a request to a
program on another machine and awaits a response. The responder is the server.
There are several server machines in the Unity realm that take requests from
the servers and deliver the requested item(s).
To use the Unity realm resources, you need some type of workstation. Your workstation may be a unix workstation running the unix operating system or an Intel-based machine (486 or better) running linux. Your workstation can also be a PC or Macintosh -based system that connects to remote machines
through the campus communications network via telnet or a modem.
You can also have two different interfaces with Unity; one is an Xwindow
environment, and the other is a "line-mode" or tty access. The Xwindow
environment is what makes a unix system what it is. It provides
multi-tasking capabilities and allows users to have several windows open
simultaneously. By using your mouse, you can quickly switch from one window to
another by clicking on the window or icon you want (without closing or exiting
the other window or application that you are using). However, to work in this
type of environment, you need either a unix workstation (X terminal), or a PC
or Macintosh computer with an Ethernet connection running some type of Xwindow
emulation software.
For information on what X emulation software the NC State Computing Center
supports, contact a consultant at 515-3035, send e-mail to
help@ncsu.edu or stop by the Information Center in Room 208 of the Hillsborough
Building.
Line mode or tty access means that only one window is
available. When you telnet or dial-in to Unity, you use
line mode. This decreases your access to some XWindow applications (ie, you
cannot run "X" applications over telnet or dial-in).
The server computers are connected to the network and each has a specific task
assigned to it. For example, there is a server computer for user e-mail
storage, one for mathematical computations and programming (SAS, Fortran), one
for mail services and so forth. When a request is received from a client, it is
sent to the correct server and the specified or requested task is carried out.
The user doesn't have to be concerned with what machine is processing their
request; the request is received, processed and information is fed back to the
user. This is one benefit of a distributed computing environment...not having
to be concerned with what machine has the neccessary computational power you
need, just so long as the job gets done.
Software in Unity includes the Operating System, user applications and
programs. Applications that users access include word processing, electronic
mail, spreadsheet applications, mathematical packages, programming languages
and others (some of this software requires an X Windows workstation).
Some software is responsible for the operating system and the user's visual
environment (screen layout). These types of applications are not neccessarily
visible to you, but you should have some knowledge of these "behind the scenes"
workings. We discuss some of these services below.
There are three network services that are important to the Eos/Unity realm;
they are Hesiod, Kerberos and Zephyr services:
- Hesiod stores user information such as name, identification number, group identification,
and file space (home directory) location.
- Kerberos verifies your login password,
providing system security.
- Zephyr is a network messaging system that you can use to send on-line messages.Your messages are "zephyr
grams", and they appear on the receiver's screen in either a separate window (for XWindows users) or as a screen message broadcast
(tty users). Tty users must turn them on to receive Zephyrs, your environment
is set to not receive them by default.
An operating system (OS) is necessary regardless of what type of computer you
are using. An operating system provides a necessary and basic set of
instructions to the computer hardware that tells the computer how to work. The
operating system provides the interface between the hardware and software. In
the unix world, depending upon your hardware platform, your OS may differ
slightly. Some examples of the different "flavors" of unix in the Unity realm
are HPUX (Hewlett Packard), SunOS and Solaris (Sun) and AIX (IBM).
In the Unity realm, you do not actually interact directly with the operating
system; rather, you give commands and interact with Unity via a shell
command interpreter. In a stand-alone unix environment or in the Unity realm, there are
several different shells. Under Unity, we use "tcsh" as our default shell.
Unity uses the Andrew File System (AFS) software to manage user and program files
in a distributed computing environment. Since the realm consists of more than one
server, files may be stored on different servers within the Unity realm. It is
AFS that joins these files together. It is the AFS software that gives users
the flexibility to login to any workstation and always have their home file
space available. The AFS also makes it easy for groups of people to share files and
other information, regardless of the machine they logged into in the realm.
Users need a lot of software and programming languages; Unity offers the user
word processing (WordPerfect), statistical/mathematical packages (Maple, SAS),
electronic mail (Z-Mail and ZM-Lite, elm) programming languages (Fortran), text
editors (Pico, vi, emacs, Crisp, NEdit) and others.
Go on to next section, Getting started
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