3.C: Other Questions?

3.A: So Which Machine do I Log on to?

3: Physics Department Cluster

When you sit down at a Unix computer, you may be facing a "console" which is connected directly into a computer's central processing unit, or a terminal connected over a network. It is likely that both can run the X Window System. A terminal engineered to run the X Window System remotely is called an X terminal or an X station. While these terminals contain rather substantial computing power themselves, they are still terminals in that they cannot function without the central workstation providing the terminal with operating system, programs, memory, and CPU cycles.

It might be hard to tell at first if you are seated at a console or an X station. If the screen in front of you requests a password, then you probably are at a console of a Unix machine. After you enter your userid and password, the X Window System begins.

If the screen in front of you contains a list of computer names ("hosts") or a whole bunch of windows, it's probably an X station. (Yet you can't be sure about that because some X stations may be set up to connect to only one computer. In that case you may need look at the physical characteristics, like lack of floppy drive, for clues.)

The X stations in our Departmental Cluster run the XDM station manager. This manager presents you with two host selection windows. Double clicking on a host in the larger or "Telnet" window will set up a telnet session. While a telnet session is not good for things graphical, it is probably the most reliable and fastest connection to other computers. It is ideal for reading mail and for connecting outside the Department, and is not as much of a load on the system as the X Window System. (Telnet is also useful if you've messed up your dotfiles and can't start an X session.)

Double clicking on a host name in the smaller or "Manage" window, which often gets hidden behind the larger one, starts a complete X session. This is what you usually want to do with an X station. Don't bother clicking on host name for machines on which you don't have accounts. You won't be able to get in.

Unix machines should go through a rather involved process before they are shut off. If your console or X station locks up and you are unable to unlock it from the keyboard, get help. If no help is available, then log onto another machine and send support email stating what happened on what machine. Never Turn The Power Off To A Unix Computer. That is the job for the system administrator only. (An X station can have its power turned off and then slowly turned back on. This should unlock it, but may take several minutes and does load down the system.)