Technical Note - Customising your UNIX environment


This document outlines how to customise your UNIX environment, and the risks involved.


Benefits of customisation

  • To make your working environment more pleasant, such as changing your wallpaper to something more calming!
  • To make it easier to do the things you want frequently, such as having programs start up when you log in.
  • To make it possible to do things most other people don't want to do, such as using web authoring tools that are not enabled by default.

Risks of customisation

  • If the ECS Programmers make upgrades to the default customisation files, either for bug fixes or feature upgrades, you may be screening yourself from these enhancements.
  • If you don't know what you are doing, you can make mistakes which might make it impossible to use programs, or even to log in. Use caution!

How to customise

Optional software packages

Several utilities, or sets of utilities, are available on the system, but not enabled as standard for every user. This could be for any of a number of reasons, for example:

  • The utilities are not available on every one of our mixed bag of hardware platforms
  • There are commands which might clash with something else
  • Adding many commands for every user complicates their setup and may slow down their interaction with the system.

We call these sets of utilities packages. They are generally introduced into your run-time environment by adding the location of the binaries to your PATH and the location of the manual pages to your MANPATH. In order to avoid you having to sort out where the binaries are for different architectures, and to avoid any difficulties were the location of the utilities to change for whatever reason, the selection of such packages is automated with the need command.

To see which packages are currently available, type need at the command prompt.

When you see a package you would like to enable, type need [package]. To have this package loaded whenever you log in, you can add the command to your ~/.cshrc file (don't move or remove the need SYSfirst or need SYSlast lines in here!)

Environment variables

Environment variables are definitions which are usually set in a shell, and then inherited by all the programs and processes which are started directly or indirectly by that shell. A few standard variables control the behaviour of a number of different programs:
  • EDITOR: Used by programs like pine and gripe to determine which program to use to allow you to edit data. You might want to set this to /usr/pkg/bin/vim, /usr/pkg/bin/emacs or /usr/pkg/bin/pico.
  • PRINTER: Used by lpr to determine the printer if none is specified. Most applications invoke lpr, so will inherit this setting.
  • PAGER: Used by programs like man to determine which program to control your window with. The default is often /usr/bin/more, but many people prefer /usr/bin/less.

Typically these lines are added to your ~/.cshrc file, for example:
setenv EDITOR emacs
setenv PAGER "/usr/bin/less"


The shell is the command-line interface you use. The ECS default is a shell called tcsh. The documentation is very long, so we'd suggest finding tutorials for things you might want to do. Three common tasks are changing the prompt (the beginning of the line where you type your command; you might want to know the folder you are in, or the current time, or such) defining new commands with alias and putting programs or scripts in your PATH.

You would make all these, and any other, shell customisations in the file ~/.cshrc.

MIT has selected the most popular variables for your shell prompt.

Norm Matloff at UC Davis has a good introduction to setting your PATH and aliases.

Changing shell from tcsh to bash or zsh
ALERT! Advanced users only

Short answer: Don't do this.
Long answer: Changing your shell.

Customising the KDE GUI (Graphical User Interface)

KDE is the default desktop environment on ECS systems. It is highly customisable via the "Settings" item on the "K" menu. This technote currently doesn't provide any information on the types of customisations that are possible. Some day it might!