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Usage of software on HPC systems is managed by a modules system.


A module is a user interface that provides utilities for the dynamic modification of a user's environment, e.g. prepending paths to:

  • PATH
  • and more

to help you to access compilers, loader, libraries and utilities.

By using modules, you can smoothly switch between different versions of installed software packages and libraries.

Module Commands

Using modules is quite straightforward and the following table lists the basic commands.

Command Description
module help Show all module options
module list List active modules in the user environment
module purge Remove modules from the user environment
module avail [modname] List all available modules
module spider [modname] Search for modules across all environments
module load <modname> Load module modname in the user environment
module unload <modname> Remove module modname from the user environment
module switch <mod1> <mod2> Replace module mod1 with module mod2

Module files are ordered by their topic on ZIH systems. By default, with module avail you will see all topics and their available module files. If you just wish to see the installed versions of a certain module, you can use module avail softwarename and it will display the available versions of softwarename only.


Finding available software

This examples illustrates the usage of the command module avail to search for available Matlab installations.

marie@compute$ module avail matlab

------------------------------ /sw/modules/scs5/math ------------------------------
   MATLAB/2017a    MATLAB/2018b    MATLAB/2020a
   MATLAB/2018a    MATLAB/2019b    MATLAB/2021a (D)

   D:  Standard Modul.

Verwenden Sie "module spider" um alle verfügbaren Module anzuzeigen.
Verwenden Sie "module keyword key1 key2 ...", um alle verfügbaren Module
anzuzeigen, die mindestens eines der Schlüsselworte enthält.
Loading and removing modules

A particular module or several modules are loaded into your environment using the module load command. The counter part to remove a module or several modules is module unload.

marie@compute$ module load Python/3.8.6
Module Python/3.8.6-GCCcore-10.2.0 and 11 dependencies loaded.
Removing all modules

To remove all loaded modules from your environment with one keystroke, invoke

marie@compute$ module purge
Die folgenden Module wurden nicht entladen:
  (Benutzen Sie "module --force purge" um alle Module zu entladen):

  1) modenv/scs5
Module Python/3.8.6-GCCcore-10.2.0 and 11 dependencies unloaded.

Front-End ml

There is a front end for the module command, which helps you to type less. It is ml. Any module command can be given after ml:

ml Command module Command
ml module list
ml foo bar module load foo bar
ml -foo -bar baz module unload foo bar; module load baz
ml purge module purge
ml show foo module show foo
Usage of front-end ml
marie@compute$ ml +Python/3.8.6
Module Python/3.8.6-GCCcore-10.2.0 and 11 dependencies loaded.
marie@compute$ ml

Derzeit geladene Module:
  1) modenv/scs5                  (S)   5) bzip2/1.0.8-GCCcore-10.2.0       9) SQLite/3.33.0-GCCcore-10.2.0  13) Python/3.8.6-GCCcore-10.2.0
  2) GCCcore/10.2.0                     6) ncurses/6.2-GCCcore-10.2.0      10) XZ/5.2.5-GCCcore-10.2.0
  3) zlib/1.2.11-GCCcore-10.2.0         7) libreadline/8.0-GCCcore-10.2.0  11) GMP/6.2.0-GCCcore-10.2.0
  4) binutils/2.35-GCCcore-10.2.0       8) Tcl/8.6.10-GCCcore-10.2.0       12) libffi/3.3-GCCcore-10.2.0

   S:  Das Modul ist angeheftet. Verwenden Sie "--force", um das Modul zu entladen.

marie@compute$ ml -Python/3.8.6 +ANSYS/2020R2
Module Python/3.8.6-GCCcore-10.2.0 and 11 dependencies unloaded.
Module ANSYS/2020R2 loaded.

Module Environments

On ZIH systems, there exist different module environments, each containing a set of software modules. They are activated via the meta module modenv which has different versions, one of which is loaded by default. You can switch between them by simply loading the desired modenv-version, e.g.

marie@compute$ module load modenv/ml

modenv/scs5 (default)

  • SCS5 software
  • usually optimized for Intel processors (Partitions: haswell, broadwell, gpu2, julia)


  • data analytics software (for use on the partition ml)
  • necessary to run most software on the partition ml (The instruction set Power ISA is different from the usual x86 instruction set. Thus the 'machine code' of other modenvs breaks).


  • uses a hierarchical module load scheme
  • optimized software for AMD processors (Partitions: romeo, alpha)


  • deprecated, old software. Is not being curated.
  • may break due to library inconsistencies with the operating system.
  • please don't use software from that modenv

Searching for Software

The command module spider <modname> allows searching for a specific software across all modenv environments. It will also display information on how to load a particular module when giving a precise module (with version) as the parameter.

Spider command
marie@login$ module spider p7zip

      p7zip is a quick port of 7z.exe and 7za.exe (command line version of 7zip) for Unix. 7-Zip is a file archiver with highest compression ratio.


  Um detaillierte Informationen über ein bestimmtes "p7zip"-Modul zu erhalten (auch wie das Modul zu laden ist), verwenden sie den vollständigen Namen des Moduls.
  Zum Beispiel:
    $ module spider p7zip/17.03

In some cases a desired software is available as an extension of a module.

Extension module
marie@login$ module spider tensorboard

    tensorboard/2.4.1 (E)

Names marked by a trailing (E) are extensions provided by another module.

You retrieve further information using the spider command.

marie@login$  module spider tensorboard/2.4.1

tensorboard: tensorboard/2.4.1 (E)
This extension is provided by the following modules. To access the extension you must load one of the following modules. Note that any module names in parentheses show the module location in the software hierarchy.

    TensorFlow/2.4.1 (modenv/hiera GCC/10.2.0 CUDA/11.1.1 OpenMPI/4.0.5)
    TensorFlow/2.4.1-fosscuda-2019b-Python-3.7.4 (modenv/ml)
    TensorFlow/2.4.1-foss-2020b (modenv/scs5)

Names marked by a trailing (E) are extensions provided by another module.

Finaly, you can load the dependencies and tensorboard/2.4.1 and check the version.

marie@login$ module load modenv/hiera GCC/10.2.0 CUDA/11.1.1 OpenMPI/4.0.5

The following have been reloaded with a version change:
    1) modenv/scs5 => modenv/hiera

Module GCC/10.2.0, CUDA/11.1.1, OpenMPI/4.0.5 and 15 dependencies loaded.
marie@login$ module load TensorFlow/2.4.1
Module TensorFlow/2.4.1 and 34 dependencies loaded.
marie@login$ tensorboard --version

Per-Architecture Builds

Since we have a heterogeneous cluster, we do individual builds of some of the software for each architecture present. This ensures that, no matter what partition the software runs on, a build optimized for the host architecture is used automatically. For that purpose we have created symbolic links on the compute nodes, at the system path /sw/installed.

However, not every module will be available for each node type or partition. Especially when introducing new hardware to the cluster, we do not want to rebuild all of the older module versions and in some cases cannot fall-back to a more generic build either. That's why we provide the script: ml_arch_avail that displays the availability of modules for the different node architectures.

Example Invocation of ml_arch_avail

marie@compute$ ml_arch_avail TensorFlow/2.4.1
TensorFlow/2.4.1: haswell, rome
TensorFlow/2.4.1: haswell, rome

The command shows all modules that match on TensorFlow/2.4.1, and their respective availability. Note that this will not work for meta-modules that do not have an installation directory (like some tool chain modules).

Advanced Usage

For writing your own module files please have a look at the Guide for writing project and private module files.


When I log in, the wrong modules are loaded by default

Reset your currently loaded modules with module purge (or module purge --force if you also want to unload your basic modenv module). Then run module save to overwrite the list of modules you load by default when logging in.

I can't load module TensorFlow

Check the dependencies by e.g. calling module spider TensorFlow/2.4.1 it will list a number of modules that need to be loaded before the TensorFlow module can be loaded.

Loading the dependencies
marie@compute$ module load TensorFlow/2.4.1
Lmod hat den folgenden Fehler erkannt:  Diese Module existieren, aber
können nicht wie gewünscht geladen werden: "TensorFlow/2.4.1"
   Versuchen Sie: "module spider TensorFlow/2.4.1" um anzuzeigen, wie die Module
geladen werden.

marie@compute$ module spider TensorFlow/2.4.1

  TensorFlow: TensorFlow/2.4.1
      An open-source software library for Machine Intelligence

    Sie müssen alle Module in einer der nachfolgenden Zeilen laden bevor Sie das Modul "TensorFlow/2.4.1" laden können.

      modenv/hiera  GCC/10.2.0  CUDA/11.1.1  OpenMPI/4.0.5
     This extension is provided by the following modules. To access the extension you must load one of the following modules. Note that any module names in parentheses show the module location in the software hierarchy.

       TensorFlow/2.4.1 (modenv/hiera GCC/10.2.0 CUDA/11.1.1 OpenMPI/4.0.5)

    This module provides the following extensions:

       absl-py/0.10.0 (E), astunparse/1.6.3 (E), cachetools/4.2.0 (E), dill/0.3.3 (E), gast/0.3.3 (E), google-auth-oauthlib/0.4.2 (E), google-auth/1.24.0 (E), google-pasta/0.2.0 (E), grpcio/1.32.0 (E), gviz-api/1.9.0 (E), h5py/2.10.0 (E), Keras-Preprocessing/1.1.2 (E), Markdown/3.3.3 (E), oauthlib/3.1.0 (E), opt-einsum/3.3.0 (E), portpicker/1.3.1 (E), pyasn1-modules/0.2.8 (E), requests-oauthlib/1.3.0 (E), rsa/4.7 (E), tblib/1.7.0 (E), tensorboard-plugin-profile/2.4.0 (E), tensorboard-plugin-wit/1.8.0 (E), tensorboard/2.4.1 (E), tensorflow-estimator/2.4.0 (E), TensorFlow/2.4.1 (E), termcolor/1.1.0 (E), Werkzeug/1.0.1 (E), wrapt/1.12.1 (E)

      An open-source software library for Machine Intelligence

      More information
       - Homepage:

      Included extensions
      absl-py-0.10.0, astunparse-1.6.3, cachetools-4.2.0, dill-0.3.3, gast-0.3.3,
      google-auth-1.24.0, google-auth-oauthlib-0.4.2, google-pasta-0.2.0,
      grpcio-1.32.0, gviz-api-1.9.0, h5py-2.10.0, Keras-Preprocessing-1.1.2,
      Markdown-3.3.3, oauthlib-3.1.0, opt-einsum-3.3.0, portpicker-1.3.1,
      pyasn1-modules-0.2.8, requests-oauthlib-1.3.0, rsa-4.7, tblib-1.7.0,
      tensorboard-2.4.1, tensorboard-plugin-profile-2.4.0, tensorboard-plugin-
      wit-1.8.0, TensorFlow-2.4.1, tensorflow-estimator-2.4.0, termcolor-1.1.0,
      Werkzeug-1.0.1, wrapt-1.12.1

Names marked by a trailing (E) are extensions provided by another module.

marie@compute$ ml +modenv/hiera  +GCC/10.2.0  +CUDA/11.1.1 +OpenMPI/4.0.5 +TensorFlow/2.4.1

Die folgenden Module wurden in einer anderen Version erneut geladen:
  1) GCC/7.3.0-2.30 => GCC/10.2.0        3) binutils/2.30-GCCcore-7.3.0 => binutils/2.35
  2) GCCcore/7.3.0 => GCCcore/10.2.0     4) modenv/scs5 => modenv/hiera

Module GCCcore/7.3.0, binutils/2.30-GCCcore-7.3.0, GCC/7.3.0-2.30, GCC/7.3.0-2.30 and 3 dependencies unloaded.
Module GCCcore/7.3.0, GCC/7.3.0-2.30, GCC/10.2.0, CUDA/11.1.1, OpenMPI/4.0.5, TensorFlow/2.4.1 and 50 dependencies loaded.
marie@compute$ module list

Derzeit geladene Module:
  1) modenv/hiera               (S)  28) Tcl/8.6.10
  2) GCCcore/10.2.0                  29) SQLite/3.33.0
  3) zlib/1.2.11                     30) GMP/6.2.0
  4) binutils/2.35                   31) libffi/3.3
  5) GCC/10.2.0                      32) Python/3.8.6
  6) CUDAcore/11.1.1                 33) pybind11/2.6.0
  7) CUDA/11.1.1                     34) SciPy-bundle/2020.11
  8) numactl/2.0.13                  35) Szip/2.1.1
  9) XZ/5.2.5                        36) HDF5/1.10.7
 10) libxml2/2.9.10                  37) cURL/7.72.0
 11) libpciaccess/0.16               38) double-conversion/3.1.5
 12) hwloc/2.2.0                     39) flatbuffers/1.12.0
 13) libevent/2.1.12                 40) giflib/5.2.1
 14) Check/0.15.2                    41) ICU/67.1
 15) GDRCopy/2.1-CUDA-11.1.1         42) JsonCpp/1.9.4
 16) UCX/1.9.0-CUDA-11.1.1           43) NASM/2.15.05
 17) libfabric/1.11.0                44) libjpeg-turbo/2.0.5
 18) PMIx/3.1.5                      45) LMDB/0.9.24
 19) OpenMPI/4.0.5                   46) nsync/1.24.0
 20) OpenBLAS/0.3.12                 47) PCRE/8.44
 21) FFTW/3.3.8                      48) protobuf/3.14.0
 22) ScaLAPACK/2.1.0                 49) protobuf-python/3.14.0
 23) cuDNN/      50) flatbuffers-python/1.12
 24) NCCL/2.8.3-CUDA-11.1.1          51) typing-extensions/
 25) bzip2/1.0.8                     52) libpng/1.6.37
 26) ncurses/6.2                     53) snappy/1.1.8
 27) libreadline/8.0                 54) TensorFlow/2.4.1

   S:  Das Modul ist angeheftet. Verwenden Sie "--force", um das Modul zu entladen.