Computer Science

The Computer Science Network

Submitted on Friday, 10/30/2015, at 12:55 PM

Our departmental network, which is available to faculty and to students in upper-level computer science courses, consists of three main servers and many workstations.  The workstations are located in our lab (Seeley Mudd 007), in out honors student office (Seeley Mudd 013) and in faculty offices.  Most of the systems are running Ubuntu 11.04.

Use for remote logins

Or connect directly to whatever workstation (e.g., x152) you usually use.

If you have a terminal session on some other machine (for example, a workstation, PC, or Mac), you can get a secure connection to castor by using ssh.  The fingerprint associated with castor's ssh key is


If you are connecting from a machine that has X windows, give the -X option when you make the connection.  That will cause any of castor's windows to appear on the client machine.  From a Mac, you'll want to use -Y instead.

Much more information about connecting to our systems is available in the menu at the left.  While we've written most of those pages to support students in our introductory classes, much of the information will apply to our departmental systems too.  If you're off-campus and have connection-speed problems, or if you run into trouble with fonts, see the page called "Solving graphical connection problems".

Access from Windows

Windows users can use Xming (if available) to access castor directly, or they can use Remote Desktop Connection to reach remus or romulus.  From remus or romulus, the command

ssh -X

will create a connection to castor.  The Windows advice page gives more information about Remote Desktop Connection.

Setting Up Your Desktop Toolbar

You get an "Ubuntu Classic Desktop" when you login to a workstation.

Chances are, there will be no icons in your top toolbar when you logon for the first time.  You can add an icon for and application by:

  • right-clicking somewhere in the empty part of the bar, add choosing "Add to Panel..."
  • choosing the second item "Application Launcher..."
  • choosing a particular item from the existing set of applications.  Two that you might want are Accessories...Terminal and Internet...Firefox.

Creating New Terminal Sessions

If you have an Ubuntu Classic Desktop, it's easy to create a new terminal session by clicking the terminal icon that you placed in the toolbar.

The situation is different if you logged on via an ssh connection from some other machine.  Suppose your client machine supports X windows and you have an ssh connection to castor.  Suppose further that the ssh connection came from an Xming client or used the -X or -Y options, meaning that graphical windows can be created on the client desktop.  In this case, you  can type "gnome-terminal" in the castor window to create an extra terminal window.  This is better than using "xterm" (which we recommended in previous years) because you can use the top bar of the gnome-terminal window to adjust the font size, create even more windows, and make other changes.

If you have used a non-graphical ssh connection, it's still easy to create multiple terminal windows.  Simply open as many ssh connections as you need.  Each connection will give you an independent non-graphical terminal session.

Changing Your Password

The command to change your password is


Be sure to change the password on your new account as soon as you can.


The default shell for users is /bin/tcsh. You can put aliases and similar material in your ~/.cshrc file. Look at Professor L. McGeoch's file, ~lamcgeoch/.cshrc, for examples of things that you can do.

If you change your .cshrc, be sure to type

   source ~/.cshrc

in any terminal window that needs access to the changes.


The CS network does not currently support printing for students.  Students should transfer their files to some other system and print from there.

The current printers are "cs3", "cs4", and "mathcscolor", all of which are intended for faculty use.

To set a default printer, put three lines into your .cshrc file that set the environment variables LPDEST, PSDEST, and PRINTER.  Also, look under System...Preferences...Default Printer on your Unix desktop menubar, and select the desired printer.

To print from the command line, use the command "lp".  You can do two-sided (duplex) printing with a command of the following form:

lp -o sides=two-sided-long-edge WhateverFile

You can define an alias in your .cshrc by saying

alias lp2 "lp -o sides=two-sided-long-edge"

The "enscript" command does "pretty-printing" of files.  Examples:

enscript -E
enscript -E2r

The -E option causes syntax highlighting, and the -2r option causes two-column printing in landscape mode.


Most new accounts are set so that

1) any users can look in your top directory

2) no one can look into your files or subdirectories.

3) the web server can access files in your public_html directory

You can totally close your top directory with the command

chmod o-rwx ~

(If you do this, you won't be able to have personal pages hosted on our systems.)

Ask one of the faculty if you'd like advice on fine-grained access control.


The department does not offer email service to students.  There is, however, a .forward file in your home directory that will cause any email that arrives to go to your regular Amherst account.

Web Pages

You can create webpages in your public_html directory, which can be accessed at

Let us know if you'd like to be able to run CGI or PHP within your
web area, and we'll turn it on for you.


Explore the "fApplications" menu to see what programs are available, and let us know if there are other programs that you think we should add.

On-Line Help

There is an extensive on-line manual of all commands and system calls. For example, for help on the command "ls", just type

man ls

To print up a copy of the manual entry on your default printer, type

man -t ls | ls

(Don't do this without looking at the manual entry first, because some are very lengthy.)


There are several odd wrinkles in the default version of emacs.  It's possible to remove much of the strangeness.  For more information click on the "Emacs fixes" link in the menu at the left.