LMOD

LMOD is an environment module system used on Unix-like operating systems to manage user environments for software packages, especially in high-performance computing (HPC) contexts. It provides a modern, Lua-based alternative to the Tcl-based Environment Modules framework, while preserving the familiar concept of modulefiles and module commands.

LMOD uses modulefiles written in Lua to describe how environment variables should be modified when a module is loaded. It supports common commands such as module avail, module load, module unload, module swap, module purge, and module show, as well as utilities like module spider to discover modules. The system is designed for scalability: it can handle large numbers of modules and multiple module trees, and it can manage dependencies via prereq and conflict directives. It also supports multiple compiler toolchains and complex software stacks.

In practice, administrators install modulefiles in directories that are added to the MODULEPATH, and users load the desired software by issuing module load commands. LMOD automatically adjusts PATH, LD_LIBRARY_PATH, MANPATH, and other environment variables to reflect the selected modules. The system is shell-agnostic and works with Bash, Tcsh, Zsh, and others, and it integrates with existing module ecosystems through the MODULEPATH and metadata features like whatis and help.

LMOD is open-source and maintained through the community, with releases available on its GitHub repository. It is distributed under a permissive license, and is widely used in HPC centers to manage software environments efficiently.