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Part Seven - Remote Computing

You may already know that the University's unix computers can be accessed remotely, for example using programs like telnet (or the more secure ssh) you can use the unix command line (text only) from your own computer.

i.e. The University's big unix computer does the hard work, and all your computer does is send your text commands and display the resulting output.

This will work fine over the university network, or even with a slow dial-up modem internet connection.

This means, for example, that you can edit files (using text based editors like jove or emacs) and compile C++ programs (using g++).

However, the X-Windows system (which we installed in part four) also lets you run graphical programs remotely.

i.e. The University's big unix computer does the hard work, all your computer does is send your keyboard typing and mouse movement, and displays the resulting graphics.

This really needs a fast network connection, so it won't work very well from home if you have dialup modem internet access. It should be fine using broadband.

This means you can, for example, run graphical programs like nedit and gnuplot on one University's big unix computers, and all you laptop just has to do is draw the resulting windows.

In order to do this, we need to install the ssh program.

  1. Close any Cygwin windows, and shut down X-Windows if it is running
  2. Run Cygwin setup
  3. Click on "Next" until you reach the "Select Packages" screen.
  4. Find the "Net" entry (about halfway down the list).
  5. Click on the plus symbol, and some sub entries should appear.
  6. Find the "openssh" entry and click on the text "Default" which should change to say "install"
  7. Click on the next button, and let Cygwin download and install ssh.
Now, lets use ssh to log into a University unix computer to run some text only programs.
  1. Run Cygwin, or the windows command prompt
  2. At the command prompt type the following and press enter:

    ssh -l username mimosa.warwick.ac.uk

    or:

    ssh username@mimosa.warwick.ac.uk

    where username is your university computer account name (probably six letters, starting ms.... for Chemists or MOAC students) and mimosa is the name of one of the university's computers.

  3. This should open a connection to mimosa, which will ask you for your university (unix) password.
  4. You should then get a screen full of messages
  5. Try typing some unix commands, like ls to list your files, or g++ -v to see what version of the GCC C++ compiler is installed.
  6. Type logout to close the connection to mimosa.
Now, lets use ssh to log into a University unix computer to run some graphical programs...
  1. Start X-Windows by running the "Start X Win" shortcut on your desktop
  2. At the command prompt type the following and press enter:

    ssh -X -l username mimosa.warwick.ac.uk

    or:

    ssh -X username@mimosa.warwick.ac.uk

    As before, username is your university computer account name (probably six letters, starting ms....) and mimosa is the name of one of the university's computers. The -X (which must be uppercase) tells ssh to pass the address of your computer's X Windows system to mimosa.

    If you see the following, don't worry - it doesn't seem to matter:
    Warning: No xauth data; using fake authentication data for X11 forwarding

  3. This should open a connection to mimosa, which will ask you for your university (unix) password.
  4. You should then get a screen full of messages
  5. As before, try typing some text based unix commands, like ls to list your files, or g++ -v to see what version of the GCC C++ compiler is installed.
  6. Also try some graphical program, for example type nedit & or mozilla &. These should appear on your screen, but are running on mimosa.
  7. Type logout to close the connection to mimosa.
Remember you are running the program on the University's unix machine - so when you try and read/write files, these are on your university unix account, NOT on your laptop.