PGDOC :Using tse Machines.

Using the Machines.

Author: David O'Brien.

Introduction

The aim of this document is to introduce new users to the computing facilities available at the School of Computer Studies. The school maintains several servers (big hard disks) for the storage of software and user files, mostly serving:

Suns
A dual processor Sun Sparcserver 1000e with 192MB of memory and a network of over 40 Sun Microsystems Sun3 and Sun4 ( Sparc) workstations, used by staff and postgraduates.

SGs
A network of over 75 Silicon Graphics (SG) Iris Indig workstations and 15 SG Indys used by staff, postgraduates and undergraduates. These machines have advanced graphics and sound capabilities.

Both of these are Unix systems, with high-resolution consoles supporting the X windows interface. While they can't share software, they can now share file server space. Ethernet connections allow remote logins, and remote display between consoles. Further, many of the machines now support the Internet communications protocols that allow you to communicate with a machine on the other side of the world as easily as with a machine in the next room.

The Suns and the Sgis can be remotely accessed from many of the text-based terminals to be found in the labs or in staff and postgraduate offices.

Staff and postgraduates (after consulting their supervisors) can obtain an account on the various computing facilities through support (see below). This means getting a slice of server space to keep your files, and a password to access it and the system software. Having an account (or username ) also allows you to send and recieve electronic mail, and to read news.

Undergraduates have their accounts arranged before they start here.

Support

The Computer and Technical Services Group (a.k.a support) are responsible for running all the School's computers and networks. This includes the installation and maintenance of systems, applications and communications software and the installation and maintenance of all computer and network hardware.

Currently support consists of the following:

	 Mark Conmy 
	 Ian Eastwood 
	 David Harkess 
	 Steve Harris 
	 Jim Jackson 
	 Peter Jowett 
	 Savio Pirondini 
	 Marcia Pusey 
	 Simon Saunders 

Reports of any and all perceived faults in software or hardware should be directed via electronic mail to ``support''. If this is not possible or the matter is urgent users are requested to telephone the machine room on extension 5488. In some cases there are notices placed near certain pieces of equipment e.g. the laserwriter in the Sun Lounge which indicate who should be contacted in the event of that device having a fault. It is wise not to assume that somebody else has already reported any given fault. All members of support read their email very frequently so responses and necessary action will usually be prompt, but sometimes they may have more important matters to deal with, and your problem may have to wait a little.

All fault reports and requests should always be directed at support and not to a specific member of staff even if the user thinks they know who will respond to their report or enquiry. This avoids messages lying unread for hours or even days.

Please note that support does not provide a programming advisory service. They deal with faults with the facilities, not the people who use them.

Logging in for the First Time

Once you've got your account(s), you can log in to one of the consoles. When you sit down at a machine, you will be greeted by the prompt:

login:

to which you type your username (followed by Return ). Now you type your password to the prompt: Password:

The Computer Manager will inform you of your initial password.

Your password will not be visible as you type it. The password is like the PIN number for a cash card- given that it is something only you should know, it confirms your identity as the owner of the account.

If you make a mistake entering your username or your password, the machine will respond with a message like Login Incorrect

and return to the Login: prompt for you to try again.

If you have not managed to log in after several careful attempts, seek assistance from support.

Changing your Password

Once you have logged in for the first time, you should change your password immediately. Type passwd to a Unix prompt. You will be asked to type your current password.

You will then be asked for the new password that you want to use, and then asked again for confirmation. Nothing that you type will be visible. If you make a mistake at any point, your password will not be changed.

Support currently supply the following advice on selecting a new password:

For example:

You should change your password often.

Unix

The Shell

The Unix shell is the ``Command Line Interface'' between Unix and the user --- i.e. you can type commands to it. A shell is what greets you when you log into a sun console or text terminal, and is what runs in a shell window under X (Xterm on the Suns, Winterm on the SGIs). You get a prompt like: csparc1

where ``csparc1'' is the name of the machine (computer science Sparc one). Programs are run by typing their name to this command line, the same as on a PC.

The shell can run ``script'' files (like batchfiles on a PC) which are a collection of Unix commands to be executed. Again, these are run by their name. Shell commands support programming constructs like loops and conditionals.

You'll need to know some basic shell commands to get very far here. New users can refer to any of the large number of introductory texts on Unix which can be borrowed from the University libarary or bought from a good bookshop.

Looking after your Files

Unix has excellent file maintainance facilities, supporting a heirarchical (branching) directory structure. Every user has their own ``home'' directory, where they start off when they log in: their own ``folder'' in which they can keep their files --- edited text and diagrams, program code, images, data and so on.

File maintenance is the business of creating, updating, using (and letting others use) and ultimately deleting files. To make this easier, users are encouraged to:

  1. Organise their files into suitable sub-directories.

  2. Use sensible (meaningful) filenames. Many standard extensions are observed --- .txt for text files, .jpg for JPEG image files, and so on.

Support maintain a regular and secure backup service of all user and system files. If you've accidently deleted a file that you wanted to keep, mail support with precise precise details of filename(s), hostname and most importantly, the last known date that the file was intact and when it was last amended.

File Protection and Sharing

Unix allows you to specify who can read and write your files and directories, or run your programs. You can set these permissions for:

Undergraduate groups are sorted by course --- csx, dpy etc. On top of that, there are staff, operator (support) and postgraduate groups.

By default, nobody but you can look in your directories --- this is for the sake of security. For the sake of collaboration, you can set permissions with the Unix chmod and umask commands. It's common to open your home directory for reading by others, and to put anything private into sub-directories. Check the permissions you have set with ls -l .

Disk Quotas

The fileservers (the system hard disks) are not of inifinite capacity, and so everybody gets a limited portion, or quota, of server disk space for their own files. These quotas are nominally 4 MegaBytes.

You can overrun your quota, provided you remove the excess within seven days. You can exceed your quota by up to 1MB, at which point you (and any programs you run) will not be able to write anything more into your home directory.

To relieve the burden on the file servers, and keep you within your quota, clear out unwanted files often. You can also compress files that you need to keep on the server but don't use that often. If there are any files that you want to keep, but don't need to hand, you can save them to 3.5 inch Ms-dos compatible floppy disks. Remember that certain kinds of files can take up a lot of space- images and sound files especially. Images can be compressed with the Jpeg format supported by xv .

If you find that for your work you need to keep more files on the servers than your disk quota will allow, discuss the matter with your supervisor or tutor, and direct any request for extra quota in the first instance to support.

You can find out how much disk quota you have left or how long you have left to get rid of any excess with: quota -v

X Windows

X windows is a Graphical User Interface, that runs on Unix machines. It allows for the display of graphics --- pictures (with programs like xv ), drawings (eg xfig ) and the detailed, stylised text characters, fonts , needed for document preparation (eg Showcase , Xdvi ). Users may be familiar with other GUIs, such as Windows , RISC-OS and NeXTStep . Novice users will have no trouble finding introductory texts in the library or a good bookshop.

User interaction with X is via a pointer, which the user moves about the screen using a mouse connected to the keyboard. The mouse has 3 buttons, which can be used to action events, depending on the pointer location. Programs written especially for X generally take advantage of the pointing and clicking nature of the interface with menus and ``pushbutton'' controls, rather than using typed commands. Usually, placing the pointer in a window gives it input focus --- ie, it will recieve keyboard input.

Under X, Programs run in ``windows'' graphical objects which can be moved, resized, stacked on top of each other, reduced to an icon or quit (terminating the program). All these operations are achieved by using the mouse. Perhaps most important of these are shell windows --- Xterm on the Suns, and Xwsh on the Sgis --- in which run Unix shells. Ideally, all the functionality you need should be in X --- all the commands you need on menus, etc --- but in reality you will want to run many Unix programs from the command line, especially file handling commands (in the absence of a good X-based file manager). Further, Unix text-based editors like vi or Emacs require a shell window in which to run.

X allows programs to run side by side on the same screen --- for example, you don't have to stop or quit a text editor to work out some figures, or to look at a manual file --- programs like xcalc and xman will share processor time and screen space along with the editor. X also allows you to copy text from one window and paste it into another, using the pointer --- a useful technique, worth learning.

You will probably notice that some people have X set up in very different ways --- different window colours, different menu options, backdrops and so on. We are coming to that.

Customising ``your'' Machine

Environment Variables

Unix and X, and by extension the programs running under them, use a number of environment variables , which can be set by the user to create a useful and pleasant working environment. These variables specify things like what sort of terminal is being used ( +PRINTER) to use by default and so on. To display the current environment variable settings, use the ``env'' command.

Dotfiles

Environment variables (amongst other things) are usually set up for a program by dotfiles in your home directory (type ls -a and you'll see them). Some software (like Khoros or Explorer ) requires additions or changes to the dotfiles in order to run properly. User customisation of the working environment is a matter of changing these dotfiles, but new users beware that you can 'customise' your environment into working badly, or not at all, so be careful . The dotfiles that most people will be concerned with are:

.login - script run when the user logs in to a machine

.cshrc - script run when a new shell (eg an xterm) is created

.xinitrc (suns) - script run when X starts (run xmailtool etc)

.twmrc (suns) - used to define menus and key functions

.sgisession (SGIs) - script run when X starts (run xmailtool etc)

.chestrc (SGIs) - used to define menus

.4Dwmrc (SGIs) - used to define key functions

.Xdefaults - used to define the default styles (colours, fonts etc) that different X programs will use

.mailrc - customisations for the mail program

Finding out more

Manual Pages

Much of the documentation that you'll ever need is on-line, ie actually stored on the computers. Most software has a ``man'' (manual) page associated with it. For instance, if you want to know more about vi , a text editor, type to Unix :

And in a moment, the first screenfull of the man page will be displayed, Hit Space to move on to the next page screenfull. If instead of hitting Space you hit / (slash) and then type in a word to look for, the page will skip down to the next occurrence of that word in the man page.

If you're unsure what software is available in the first place, you can use the apropos command to get a list of man pages for software that mentions a certain keyword. Try, for example:

apropos image

There is also an X-based manual browser, xman , which supports the apropos facility. New users be warned, though, that man pages are often long and technical.

Pgdoc

The other main source of information is the new software review in the PGDOC area. To access the information simple add the following line to your .cshrc . source pgdoc/bin/setup

Either source the .cshrc file or logout and log back in. Now you may use the pgpage command to access the documentation. Read the introductory document for more details. If you are sitting in front of an X terminal simply type:

pgpage introduction

Alternatively you may access the pgdoc documentation by using a hyper-text basedsystem. Simply type:

xmosaic
and click on the PGDOC entry.

Built in Documents

A lot of the available software has extensive built-in documentation. You're also likely to come across README text files, usually in directories containing a piece or suite of software. You can view these with the more command.

Asking Around

Remember --- if you're stuck, don't be afraid to ask someone. The news system is always good place to look for help. We have amongst the local newsgroups:

local.unix

local.X11

local.indigo

and more specialised groups, like local.khoros, to which you can post technical questions, and get the attention of many in-school experts. It is hoped that all the Usenet groups will soon be available, giving you access to a very large body of technical expertise. Many newsgroups compile an FAQ (Frequently Asked Questions list), which you can get hold of by various means.

Requests for information may also be directed to support --- but remember, they are not a programming advisory service.

Books

The library has a well stocked Computer Science section, and many bookshops like Austicks (opposite the Parkinson building) keep many standard references in stock, or can order them for you.

There is some documentation of hardware and software held in the support office room 10.31a which is available on short term loan to staff and students. Most Ingres documentation, for example, is kept there.

Using Remote Machines

Remote Unix

The computer networking within the University allows remote logins between machines. If you want to use software on the Suns (say) and they're all being used, no problem. You can use an Sgi (say) as a display terminal. Just use rlogin (machine name)

You'll then be asked for your password on that machine. After that, you'll be using a shell running on the remote machine.

Remote X

X is a client/server system. That is, one console can display (serve) an X program (the client) running on a different machine. If you run an X program on a machine that you are remotely logged-into, you need to make sure that the environment variable DISPLAY is pointing to the display of the console that you are sitting at. This can be done automatically with small additions to your dotfiles --- see:

  ~pgdoc/remote_display.setup.txt 

Note that not all Sgi software can be displayed remotely --- some of it makes use of GL routines that are in the Sgi hardware.

File access between Suns and Sgis

It is possible to access your home directory on the Suns from the Sgis and vice versa (so you won't need to rlogin to use them). The home directory paths have the following structure: /home/system/username

where system is

csun for the SCS Suns

csgi for the SCS SGI's

For example, if user nobby is logged into an Sgi and wants list his Sun home directory he'll use:

ll /home/csun/nobby

Printers

What and Where

There are three types of printer available, accessible from any of the machines. In order to see up to date details of the printers available type printers on any School Sun or SG workstation.

Laser
for high quality reports and presentations, making use of fonts and graphics, as produced by or Showcase .

Dot matrix
for medium quality printouts of documents making use of rudimentary formatting such as emphasis.

Line
for medium to low quality printouts of plain text (like program listings).

How to use the Printers

When you print a file, you need to specify which printer you want to use. For example when printing a text file, use:

lpr -Pprintername filename

Print jobs join a queue to await printing. You can view the printer queue with:

lpq -Pprintername filename

If you think better about printing something (eg you have inadvertently sent a program listing to a laser printer), you can look at the queue and remove the print job with:

lprm -Pprintername filename

Some print jobs can take a very long time --- for example, long PostScript files or images. Save printing these till out of office hours, if possible. Some large print jobs can even exceed the printers memory capacity and get rejected.

Ettiquette

Be economical in your use of printing facilities, and restrict it to use related to your course or research work --- support can introduce printing quotas at the drop of a hat if need be. The large number of X terminals available means that you can edit your masterpiece in detail and comfort --- be it plain text in an A4 sized window, a Showcase document, LaTeX (with xdvi ) or PostScript (with xpsview ) --- before committing to paper.

Labs

Locations

The ``Sun Lounge'' on Level 9 currently contains one Sun4 console, one Sun3 console, and five SGI Indigo consoles, as well as 3 specialist Grasparc machines which have limited access. This lab is for the use of staff and postgraduates.

Computer Studies Room 10.31 (on Level 10, off Red Route in the Physics and Administration Building) is the main undergraduate facility. It contains 32 Sgi consoles, as well as nearly 30 text terminals from which the Suns, Sgis and UCS facilities can be accessed. The support offices are also located here.

Room 7.10 contains another 20 Sgi consoles. There are further machines in staff and postgraduate offices, and the seminar room, 7.10a. The arrangements as they stand are liable to change, so keep an eye on news for notification.

Security

It is hoped to ensure undergraduate access to rooms 10.31 and 7.10 from 8am to 12pm, 7 days a week in term time and vacations.

Postgraduates and staff are issued with keys that will allow them access to any of the labs at anytime, as well as their own office. Please ensure that you do not leave any doors open or unlocked outside of office hours, otherwise access may have to be restricted to prevent the danger of theft.

Ettiquette

Make best use of machine time and don't hog machines, especially when the labs are busy. So:

Also, don't eat or drink in the labs --- spillages can damage machines and your bank balance. Smoking is not allowed in any of the labs.

Sgi Specifics

X runs all the time on the Sgis, so you don't have to bother running it yourself. The standard setup supplies you with a couple of shell windows, a clock and a menu (``chest'' of useful things, including ``Overview'' and ``Learn'' facilities, which novice users will find useful. Use this menu (sub-menu ``Windows'') to log out.

Microsoft Windows users should find the style of X that runs standardly on the Sgis very familiar. If you happen to prefer the style that runs on the Suns, you can set up your Sgi account to use it.

On the Sgis, time quotas for console use do exist. These are currently:

Undergraduates - 5 to 7 hours per week (to be decided)

Staff and PGs - unlimited

Currently, only normal office hours (9 to 5) are on a quota --- outside of these, console time is not counted. If you use up your quota, you won't be able to use an Sgi console in office hours till the start of the next week. This is to ensure that only essential use is made of the Sgis during peak hours when they can be over-subscribed.

Never hit the reset button on the Sgis --- it can corrupt the file store. If a console is playing up, mail support .

You will not be able to log into an Sgi console if you have not cleared any disk quota excess within the 7 day limit --- you will need to borrow a shell window from someone and remotely login as yourself to delete files in your area.

Sun Specifics

Once you have logged in, you will be greeted by an informational ``message of the day'', and after a few moments, a Unix prompt.

To be able to use X on the suns, you need to do some setting up. The procedure is outlined in

  ~pgdoc/SunX.setup.txt 

Once this is done, you will not need to do it again. From now on, you can start X running by typing:

After a few moments, the screen will clear as programs start running under X. A clock should appear, along with a mail tool and two shell windows --- xterm and console .

With the standard setup, pressing the middle mouse button on the background (``root window'' will give you a menu of X window programs you have running. Pressing the right mouse button gives a menu of useful actions. From this menu, you can run programs like shell windows, editors, a calculator and so on. Use this menu to exit X --- note that this does not log you out: type logout afterwards to do this.

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