Re: Networking

[Jim Jackson <nospam [at] scs.leeds.ac.uk>]

On Wed, 3 Nov 1999, Ian W. Wright wrote:

> As a complete Linux novice, I sometimes feel a little overwhelmed by all
> the expertise displayed on this list and so it has taken a while for me
> to pluck up courage to ask what, to most of you, will probably seem a
> couple of very simple and stupid questions.

not stupid and hardly simple :-)

> I have four computers sitting in various parts of my house and workshop,
> all Pentiums, two with Windows 98 only, one with windows 95 and Redhat
> linux 5.2 and one with RedHat 6.0 only and a couple of printers and a
> scanner. So, bearing in mind that I have now given up work and am on a
> small pension and so am rather cash limited, what do I need to
> do/get/buy(yuk) to link all the machines together - hardware and
> software - so that I can, at least, print from any machine and exchange
> or access files between machines? Also, is it possible to combine the
> computing power of the various machines (build my own mini Cray!!!! ;0))
> - something like having a multi-processor machine. Is there software
> which would do this or would it also need programmes written
> specifically for such an environment?

Hardware wise - the cheapest solution is to build yourself a thin ethernet
network. Buy some cheap PCI or ISA ethernet cards with BNC connectors.
Buy 50ohm coax cable, BNC connectors Or ready BNC'd coax lengths) and T
pieces and two terminators (50ohm resistors excapsulated in a BNC
socket). The object is to have one continous cable run past all your
computers - no splitting/forking etc.

Terminator Tpiece
coax coax
[TERM][T]----------[T]-----------[T]--------[T]----------[T][TERM]
| | | | |
----- ----- ----- ----- -----
computer computer

start with the terminator (TERM) plug it on one side of a 50ohn BNC T
piece, plug this T-piece on the first computer ethernet card, plug a
length of coax to the other side of the T-piece, sting the coax to the
second computer and plug the coax on another T-piece, plug T-piece onto
ethernet card of computer, connect another piece of coax etc etc
At the last computer plug the second Terminator on the last T-piece.
The T-pieces MUST plug straight on the back of the ethernet card BNC
socket.

Terminators can be bought or made. standard 1/4watt 51ohm 5% metal film
resistors will do soldered with short leads on the back of a 50ohm BNC
socket between the centre pin and outer metal work.

50 ohm BNC plugs can be soldered onto 50ohm coax to make the leads - this
is not difficult but also is not trivial. Expect a few failures at first
if you've not done this before.

Get your linux setup for networking - see the Ethernet howto, usually at

/usr/doc/HOWTO/Ethernet-HOWTO

use the ping to check connectivity.

Linux comes with virtually everything you will need for successful
networking.

telnet/rlogin so that you can login to another computer on the network

rcp/ftp for copying files from computer to computer

NFS for NFS file serving

SAMBA for file serving/access to Windows platforms

WWW apache etc for web serving

For multi-processor then don't expect alot. Look up Beowulf on the
Web. but don't expect much from it unless you are writing custom parallel
programs. I believe there is clustering project under way for linux
which would give some needed transparency to sharing computers. At moment
if you are a C or C++ coder you can use MPI (and others, with or without
Beowulf) to write a parallelised program to take advantage of several
networked machines - not trivial stuff.

Hope thats enough to get you started :-)

Jim

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