Environment Modules

Environment Modules allow for management of environment variables  when using multiple compilers, multiple libraries, or even versions of applications that you might need to run. Rather than change $PATH, $LD_LIBRARY_LOAD, or $MANPATH for each you can use Environment Modules to handle the path changes to ensure you run the appropriate version correctly.

Installation

On CentOS etc:

yum install environment-modules

On Ubuntu/Debian-esque:

sudo apt-get install environment-modules

Usage

Important: Log out and log back in again

Then check the modules that are currently available:

module avail
module list

Adding a Module

I’d like to add a module to set an alternative GCC compiler. The system version of GCC was at /usr/bin/gcc and was version 4.4.7. A more updated version 4.9.0 was comiled under /var/shared/gcc-4.9.0

To add an Environment Module for my custom GCC version 4.9.0, I did the following:

cd /usr/share/Modules/modulefiles/
mkdir compilers
cp /usr/share/Modules/modulefiles/modules /usr/share/Modules/modulefiles/compilers/gcc-4.9.0

The modules file copied above is a useful template but I amended a file by Jeff Layton from admin-magazine.com :

#%Module1.0#####################################################################
##
## modules compilers/gcc-4.9.0
##
## modulefiles/compilers/gcc-4.9.0 by jonny based on admin-magazine.com Jeff Layton
##
proc ModulesHelp { } {
        global version modroot
        puts stderr "compilers/gcc-4.9.0 - sets the Environment for GCC 4.9.0 in /var/shared "
}

module-whatis   "Sets the Environment for using the GCC compiler version 4.9.0"

# for Tcl script use only
set     topdir          /var/shared/gcc-4.9.0
set     version         4.9.0
set     sys             linux86

setenv          CC              $topdir/bin/gcc-4.9.0
setenv          GCC             $topdir/bin/gcc-4.9.0
setenv          FC              $topdir/bin/gfortran-4.9.0
setenv          F77             $topdir/bin/gfortran-4.9.0
setenv          F90             $topdir/bin/gfortran-4.9.0
prepend-path    PATH            $topdir/include
prepend-path    PATH            $topdir/bin
prepend-path    MANPATH         $topdir/share/man/
prepend-path    LD_LIBRARY_PATH $topdir/lib
prepend-path    LD_LIBRARY_PATH $topdir/lib64

To activate this environment:

module avail

module load compilers/gcc-4.9.0

Now if I run module list I can see the new module has been added:

module list

If I run:

which gcc

I should see:

/var/shared/gcc-4.9.0/bin/gcc

This assumes that there is a binary named gcc in /var/shared/gcc-4.9.0/bin – if there is not create a symbolic link to it. For example, I needed to do:

cd /var/shared/gcc-4.9.0/bin
ln -s ./gcc-4.9.0 ./gcc

Unloading Modules

To unload a module and return to using the system provided paths:

module unload compilers/gcc-4.9.0
module list

This should show no modules and running ‘which gcc’ should show the system gcc again:

I can now distribute the /usr/share/Modules/modulefiles/compilers/gcc-4.9.0 file among the cluster via Puppet for use on any cluster node.