Some notes for Flux modules users

With the operating system upgrade in July, 2016, the ARC-TS clusters will be using Lmod as a replacement for the Environment Modules (Tmod, hereafter). Lmod was designed to be a drop-in replacement for Tmod, so for many operations, the commands and functionality are the same. Below are sections on what is similar and what is different about the module commands.

Basic module commands

The basic module command is the same, and it has most of the same options. The most commonly used commands are exactly the same. For example, using the program R as an example,

$ module load R
$ module unload R

When you want to search for a module, there are now three choices,

$ module av 
$ module spider 
$ module keyword

You may want to try that with both gcc and python to get an idea of the differences among them.

We recommend that you review our Lmod documentation page at

Saving a named set of loaded modules

The section on Prerequisites and Named Sets explains how you can create a set of modules that can be saved with a name and reloaded with a single command.

Changed behavior of default version specification

Under Environment Modules, if you added a folder to the MODULEPATH, then the versions in that folder would take precedence over those in the system folders. This does not seem to be true with Lmod. If you want to load a version from your own folder, say, one that is lower than or different from, the system default, you should specify that version explicitly on the module load command, or you can create a symbolic link called default that points to the version you want.

So for example, if you create ~/Lmod/my_modules to put your module files into, and your create a module for hello version 1.1, then

$ lmod use ~/Lmod/my_modules
$ cd ~/Lmod/my_modules/hello
$ ln -s 1.1.lua default

will make that the default version. So long as no other default version appears in the MODULEPATH ahead of it, that will be the default.

At the present time (Jun 20, 2016), we are still working out final details of the configuration. We will decide how best to handle default modules and post the information here. If this interests you, please let us know at, make the subject line read: Lmod default modules.