Appendix B

B.1 Using X Windows

Throughout this guide we have stuck rigidly to using a UNIX system from its command line interface however, it is also possible to run software that uses a graphical user interface (GUI) similar to those seen in Microsoft Windows and on the Apple Mac. In fact is even possible to run a whole desktop environment complete with desktop manager as in Windows/MacOS. The UNIX feature that makes this possible is something called the X Windows system or just X Windows for short.

There are two main components to X Windows, namely: an X server which displays the graphics sent from a remote UNIX machine on a PC (and which allows interaction via the keyboard and mouse) and an X client which is a program running on the remote system. Note that is the opposite way round to what you might expect: the X server runs locally on your PC and the X clients run remotely on the UNIX machine.

There are many software packages which can be used to run a Xserver on your PC but the one we'll concentrate on here is MobaXterm which we first came across in section 8.4 (another example is eXceed). Typically there will be many X client program available on a UNIX system and one of the most useful is Xterm (short for X terminal) which provides a command line interface similar to PuTTY.

If you don't already have MobaXterm installed, it can be installed on the MWS using:

Start -> Install Uni Apps -> Utilities -> MobaXterm 10.2

or you can download it from: http://mobaxterm.mobatek.net

Start MobaXterm by double-clicking on the desktop icon and then click on the Session icon in the top left hand corner and then the SSH icon in the pop-up window as shown below:

Next enter the name of the remote host you want to connect to which in this case is condor.liv.ac.uk and enter your username:

You will then be prompted for your password and, once this has been entered correctly, you should see another Xterm window similar to the one below:

You can use the Xterm to run commands as you would do with any other terminal emulator however, in addition, you can now open multiple Xterms on your desktop as well as run programs that have graphical interfaces. To run another Xterm, enter this command

$ xterm &

The ampersand (&) runs the Xterm program in the background which frees the command line on your original Xterm for you to enter other commands. Try running it without the & to see the difference.

You should now see another Xterm open on your desktop which you can use at the same time as the original one. You can also create additional Xterms by clicking Session and SSH again. Select Terminal | Detach from the menu to separate an Xterm from the original MobaXterm window thus allowing you to move it around your desktop as shown below:

You can use MobaXterm from off-campus but you will need to set up a virtual private network (VPN) connection first. See for details.

B.2 Using the nedit editor

One of the serious limitations with UNIX systems is the lack of resonably powerful and user-friendly file editors that are built-in. On Condor however, and many other systems at Liverpool, there is an editor called nedit which is easy to use and features many of the actions and shortcuts used in Windows editors (Windows Notepad in particular). For example you can use [Ctrl-x] to cut text and [Ctrl-c][Ctrl-v] to copy and paste text. To use nedit first start up an Xterm using MobaXterm as descibed above. Then enter this command:

$ nedit &

You should see a new window open with the nedit graphical interface:

(Note that you should still be able use the comamnd line interface. Press [Return] a few times in the Xterm window if you do not see the command prompt).

You can find help on how to use nedit by clicking on Help on menu bar. There is also a manual available online.

B.3 Command summary

Command Meaning
xterm & start an Xterm window in the background
nedit & start the nedit editor in the background