Module names and module naming conventions

The modulefiles contain commands that change the user’s environment to make an application or library available to a user. So loading a modulefile named gcc/7.1 should hopefully make the programs Gnu Compiler Collection (i.e. gcc, gfortran and g++ compilers) available to a user.

So the gcc/7.1 module is a file named either 7.1 or 7.1.lua depending on whether the commands are written in TCL or Lua respectively and this file is in the gcc directory.

To see a more complete module layout, let’s assume your site has has a MODULEPATH set to:


And the directory layout from /apps/modulefiles is:

$ cd /apps/modulefiles; tree -a
├── Core
│   ├── A
│   │   ├── 1.0
│   │   └── 2.0.lua
│   ├── gcc
│   │   ├── 5.4
│   │   └── 7.1.lua
│   └── StdEnv.lua
└── Other
    ├── C
    │   ├── 3.3.lua
    │   └── 3.4.lua
    └── D
        └── 4.0.lua

In the above structure there are 8 modulefiles. So the 5 modulefiles under Core are: A/1.0, A/2.0, gcc/5.4, gcc/7.1 and StdEnv. Note that Lmod’s name of a modulefile doesn’t include the .lua extension. Also note that both A and gcc have two versions where as StdEnv has a name with no version.

fullName == sn/version

The fullName of a modulefile is complete name which is made of two parts: sn and version. The sn is the shortname and represents the minumum name that can be used to specify a module. So for the gcc/7.1 modulefile. The fullName is gcc/7.1 and the sn is gcc and the version is 7.1. This naming convention is known as NAME/VERSION and is abbreviated N/V. There are two more complicated naming schemes known as Category/Name/Version (a.k.a. C/N/V) and Name/Version/Version (a.k.a N/V/V). In all three naming schemes, a modulefile has a fullName which is split into sn / version. The split between the sn and version will be different depending on which naming scheme is used. Sometimes the version doesn’t exist like for StdEnv module. In this case the fullName is the same as the sn.

In next section How Lmod Picks which Modulefiles to Load, we explain how a Lmod takes an sn and determines which modulefile to load. But in short, Lmod picks the marked default or if there is no default then Lmod picks the “highest” version.

Special Names for modulefiles

If the version has a leading dot then this modulefile is hidden. That is, it can be loaded but it won’t be shown by module avail. If the sn name has a leading dot, such as .X then every version of this module will be hidden. So .X/1.0 is hidden and so is Y/.2.0.

Because of the way that Lmod passes information between module command invocations, a modulefile CANNOT have two or more leading underscores. So naming a modulefile _A/1.0 is acceptable but having two underscore such as __B/1.0 is not!

Module Naming scheme: Category/Name/Version (C/N/V)

Sites may wish to group similar modules into categories. For example, all the biology packages grouped together, like bowtie and tophat packages be named: bio/bowtie/3.4 or bio/tophat/2.7. When the fullName is bio/bowtie/3.4 then the sn for is bio/bowtie and the version is 3.4.

Sites should think carefully about chosing to using C/N/V. This can make it easier for users to know which modules provide say physics, chemistry or biology applications but it does lead to great deal more typing of which tab completion provided by the bash or zsh shells can only do so much.

Sites can have meta-module inside a category. A meta-module is a module that has no version. For example, suppose you have the following C/N/V modulefile structure:

$ cd /apps/modulefiles/Other; tree -a
└── bio
    ├── bowtie
    │   └── 3.1
    ├── genomics.lua
    └── tophat
        └── 7.2

In this case there are three modules bio/bowtie/3.1, bio/tophat/7.2. The bio/genomic module is a meta module where the fullName is the same as the sn and it has no version.

The rule that Lmod uses to determine which modules are meta modules and which have a version is the following. If a file is in a directory that has other sub-directories (other than . and ..), the file is a meta-module. So the genomic.lua file is part of the sn for bio/genomics because the genomics.lua file is in a sub-directory that has the directories bowtie and tophat.

Sites can mix N/V and C/N/V layouts, Lmod will be able to decide the sn and versions by walking directory tree. In general, the fullName, will be divided into directories names to become the sn and the version will be the file. So for the fullName bio/tophat/7.2 the directores bio and tophat become the sn, bio/tophat and the version is 7.2.

Lmod supports as many directory levels as site likes. For example, a site could have a modulefile named A/B/C/D/1.1 where the sn name is A/B/C/D and the version is 1.1.

Module Naming scheme: Name/Version/Version (N/V/V)

A site many wish to have directories has part of the version. This could be used to have 32 or 64 bit versions of the same package. So for example a site might wish to have a modules named acme/32/4.2 and acme/64/4.2 where sn is acme and the versions are 32/4.2 and 64/4.2.

By default, Lmod assumes that the version is just the file, so lmod needs to be told where the sn / version split is. This can be done by creating an empty .version or .modulerc file where a site wants the split to be. For the above example, the following layout make acme be the sn:

$ tree -a
└── acme
    ├── .version
    ├── 32
    │   └── 4.2
    └── 64
        └── 4.2

because there is a .version at the same level as the 32 and 64 directories. With the .version file, the fullName is acme/64/4.2 and the sn is acme and the version 64/4.2. If the .version file was removed then the sn would be acme/64 and the version would be 4.2.

Sites are can name modules with as many directories as they like. For example a site can have a module named:


If there is an empty file at mpi/mpich/.version then the sn would be mpi/mpich and the version would be 64/3.1/048.