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Arnaud Taddei CN/DCI (for the HEPiX Shells Scripts Working Group)
In a previous CNL issue (CNL 219), an article in the Desktop Computing
Chapter presented
the strategy of two working groups, UMTF-X11 and HEPiX-X11, concerning an
X11 common graphical environment. This project comes after the HEPiX Shells
Login Scripts which are successfully being used on many services at CERN and
in the HEP community. The latter project addressed the shell customisation
(see the previous article, 
, on the latest release).
After introducing a preliminary version of the X11 environment on the CERNSP and CMS clusters, the first production release is now available and already deployed on some services. By the time of this article, the HPPLUS service should be using it and in the future CERNSP, CMS and other services will be using these so-called HEPiX X11 login scripts and probably other sites like INFN Pisa, etc.
This X11 environment consists of a set of scripts and programs with their documentation which provide users with a working X11 default environment and a proper architecture for various levels of system and group administrators to customise their users' environment the way they want. They permit users to get the same environment across HEP sites, to share a common method to handle the same problem at various sites and they are sometimes even the only way to provide users what they want.
The main idea of these scripts relies on an architecture in which are defined Major Switches which control the Xsession. When you log in from an Xterminal or a PC or a Mac Xserver emulator or the console of a workstation (if it is in graphical mode of course) then you are creating an Xsession.
To make an analogy to the telnet command, when you log in to a system with telnet or rlogin
for example, then there are scripts which are executed and perform some actions for you to create your user environment. This what is done by the HEPiX shells' login scripts.
Creating this Xsession involves a sequence of actions which are performed at login which start the various components of the session. For example, you can specify which desktop to run (HP-VUE, COSE-CDE, HEPIX); in the case where you choose the HEPIX desktop you can specify which are the xclients to start at the beginning of the session, which is the window manager (if any) to use, which is the root window to set, etc. Each of these items is called a Major Switch and you can specify them in a dedicated file in your user Home directory, or, if you are a system or group administrator, you can set it for a group of users, for a single machine, for a cluster or for a site (or any combination of these).
On the CERN site, the default is controlled by the UMTF-X11 working-group
whose recommendations are described in the following article ().
For more technical information you may consult:
http://wwwinfo.cern.ch/hepix/wg/scripts/www/
in which are listed a User Guide and a System Administrator Guide for installing and customising the HEPiX shells and X11 login scripts. Moreover the version page lists with more details the available features.
hepix/wg/scripts/doc/version/Version.html