Using Linux to share your High-end Workstation

Written by Jörg Hau. Version: 2004-09-10 (first published: 2001-03-09).

Introduction

The majority of modern scientific instruments is controlled by computers, either embedded or connected through some kind of interface. Especially "high-end" equipment like mass spectrometers or nuclear magnetic resonance instrumentation is controlled using operating systems like Unix or OpenVMS, which are known for their stability and real-time multitasking capabilities.

Due to the permanent use of expensive instruments, there is a need to access data even if the instrument's workstation is occupied by an operator. The "traditional" approach to process data on another computer (or even to control the instrument) would be to buy another expensive high-end workstation with the same expensive software and to use it for off-line processing. However, this is rarely cost-effective.

A much simpler way is to use a "cheap" computer system and to redirect the display of the workstation to that computer. This is easily possible as all of the systems mentioned above make use of the X-Window system to interact with the user. X-Windows is completely different from the known Microsoft Windows environment in many aspects, one of the most interesting being that input and output can be redirected to another computer. This can be used in so-called "terminal emulation" programs, where the display from an X-Windows application is displayed in a browser; however, these emulators are often a costly piece of software and require a fairly powerful computer to run.

In contrast to this, any standard, low-end Personal Computer (PC) can be run under Linux. Linux is a freely available operating system and features the X-Windows system as its standard display. This text describes a simple approach that has been used with success in the author's laboratory.

Background

The X Server

Every "X Server" has a display name of the form:

hostname:displaynumber.screennumber

The hostname specifies the name of the machine to which the display is physically connected. The hostname can be omitted and in this case, the server on the same machine will be chosen - in fact, if you are the only one using X on your computer, you will want to just leave this off of your display specifications. The displaynumber is probably zero, this is used if the X Server is controlling more than one keyboard and monitor unit, for instance, a network of X terminals. The screennumber specifies which monitor in a multiple monitor setup should be used [1].

In this configuration, all the actual processing is performed on the workstation, and only the display (that is, screen, keyboard and mouse) are redirected to the computer running Linux. Thus, is is not required that the Linux PC be a powerful PC; a convenient., large display is sufficient. In the same context, it is not required to recompile any software for use under Linux as the processes are indeed running on another computer.

Experimental

The experiments described below were initially carried out using an old, "technically outdated" 75-MHz Pentium PC (Digital 575) running SuSE Linux 6.3. The application servers were a Digital AlphaStation 4/100 running Digital UNIX 4.2c and the application software package Finnigan ICIS2 Version 8.3, as well as Micromass OPUS under OpenVMS.

While the procedures described below should work ad hoc, it is recommended to create a second, separate user account for the data system to avoid interference with the data system version that is currently running on the workstation itself.

How-To

Procedure for Finnigan ICIS2 (Digital UNIX)

We assume that the ICIS2 package is installed on a workstation named alpha. The login shell for alpha is csh, which is the default Finnigan installation. We want to access the workstation from our "local" computer, a Linux PC called linuxbox. On linuxbox, type in a terminal window:

xhost alpha

You should get a message telling you that alpha is being added to the access control list. Now, use ssh, telnet, rlogin or whatever program you like to log in to the server:

telnet alpha

After login, redirect the display to your local computer:

setenv DISPLAY linuxbox:0.0

This requires that the IP address of linuxbox is known on alpha and vice versa. If no entry in /etc/hosts is provided (e.g. DHCP), it is also possible to specify the IP address directly:

setenv DISPLAY 192.168.111.111:0.0

Now you are ready to launch your application:

exec_icis &

The display will appear a few seconds later on your local Linux workstation. Note that applications should be launched in the background and that it is not recommended to launch a "daughter" application (CHRO, SPEC, ...) directly: In the case of Finnigan's ICIS2, all colour settings are controlled via the ICIS Executive, so that launching CHRO directly may lead to strange or unusable colour settings.

Here is a screenshot, displaying Finnigan's ICIS software on Linux' KDE2 desktop. Click on the image to see the full-size version (resolution 1280x1024, 144 kB).

XWindow

Procedure for Micromass OPUS (OpenVMS)

We assume that the OPUS software is installed on an OpenVMS workstation called opus. We want to access the workstation from our "local" computer, a Linux PC called linuxbox. On linuxbox, type in a terminal window:

xhost opus

You should get a message telling you that opus is being added to the access control list. Now, use ssh, telnet, rlogin or whatever program you like to log in to the server:

telnet alpha

When you have logged in, set a few variables, redirect the display to your local computer and create a DECterminal:

set sys$workstation decw$display
set display/create/node=192.168.111.111/transport=tcpip
create /term/detach

The upcoming terminal should show the message on launching OPUS:

opus

The OPUS display will appear a few seconds later on your local Linux workstation. Note that all colour settings are controlled via OPUS; we have experienced one case where a server crash on OPUS lead to unusable colour settings. The problem was cleared after a reboot of the OpenVMS system.

Remarks

Security Issues

Note that xhost is not a very secure method to establish connections. It should be used only in protected environments, i.e. if you are behind a firewall and you trust your colleagues on the other terminals. For an in-depth discussion, refer to [2]. In case of doubt, as soon as your X client has made its connection and displays a window, you may want to revoke permissions for more connections with:

xhost -alpha

Another, more straightforward solution is to use ssh, which also supports X forwarding. If you are looking for an ssh client and an X Server for Microsoft Windows, there is some information on my Windows page.

Legal Issues

In terms of licensing, most license contracts allow to run the original software on only one machine. However, this is not an obstacle as the software as such runs only on the host computer; is is the display that is redirected to another computer. Thus, this procedure should not violate most common license contracts.

Acknowledgements

Special Thanks for help with the individual configurations go to Jürgen Schmädecke from Finnigan, Bremen (ICIS system) and to Paul Darnley from Micromass, Manchester (OPUS system).

References

[1] Ray Brigleb. The X Window User HOWTO, v2.0, 1999-09-01.
[2] Vincent Zweije. Remote X Apps mini-HOWTO, 1998-07-14.

Disclaimer

(See also this page). This text is copyrighted by Jörg Hau. All rights reserved. The information and opinions contained on this Website is provided without warranty of any kind, neither expressed nor implied. Although I make reasonable efforts that the information provided here is correct, I do not guarantee that it is accurate, reliable or complete. All trademarks or similar items on this web site are the property of their respective owners and are used for identification purposes only. Their use does not imply any recommendation, invitation to buy a specific product, or similar.