Our approach with the maintenance of software on the CS Linux machines is to keep the standard versions of software as supplied by the linux distribution as the default. We then use a package called Environment Modules to make it easy for users to get access to new packages or newer versions of software.

When you log into the CS Linux systems, you will have access to the module command. Using module you can manipulate your environment variables (like your PATH and LD_LIBRARY_PATH) to gain access to new software or different versions of the same package. For example, to make Firefox version 2 the default, you would run:

module load firefox/2.0

Running this command would make Firefox 2.0 the default for the current shell. You can make this change permanent by added this module line to your .bash_profile (if using the bash shell) or .login file (if using csh or tcsh). Note that the default shell for new accounts is bash but you can confirm the shell you are using by running "echo $SHELL". After you make changes to your .bash_profile or .login file these changes will be in effect the next time you login.

Here are some useful module commands:

• module avail - List the available modules. Note that if there are multiple versions of a single package that one will be denoted as (default). If you load the module without a version number you will get this default version.

• module whatis - List all the available modules along with a short description.

• module load MODULE - Load the named module. For example, you can run

  module load firefox/2.0

  to use version 2.0 of Mozilla Firefox or you can just run:

  module load firefox

  to use the version of firefox denoted as (default).

• module unload MODULE - Unload the named module, reverting back to the OS defaults.

• module list - List all the currently loaded modules.

• module help - Get general help information about modules.

• module help MODULE - Get help information about the named module.

• module show MODULE - Show details about the module, including the changes that loading the module will make to your environment.

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