The use of module systems to manage user environment in a controlled way is a common practice at HPC centers that is often embraced also by individual programmers on their development machines. To support this common practice Spack integrates with Environment Modules and LMod by providing post-install hooks that generate module files and commands to manipulate them.


If your machine does not already have a module system installed, we advise you to use either Environment Modules or LMod. See Environment Modules for more details.

Using module files via Spack

If you have installed a supported module system either manually or through spack bootstrap, you should be able to run either module avail or use -l spack to see what module files have been installed. Here is sample output of those programs, showing lots of installed packages:

$ module avail

--------------------------------------------------------------- ~/spack/share/spack/modules/linux-ubuntu14-x86_64 ---------------------------------------------------------------
autoconf-2.69-gcc-4.8-qextxkq       hwloc-1.11.6-gcc-6.3.0-akcisez             m4-1.4.18-gcc-4.8-ev2znoc                   openblas-0.2.19-gcc-6.3.0-dhkmed6        py-setuptools-34.2.0-gcc-6.3.0-fadur4s
automake-1.15-gcc-4.8-maqvukj       isl-0.18-gcc-4.8-afi6taq                   m4-1.4.18-gcc-6.3.0-uppywnz                 openmpi-2.1.0-gcc-6.3.0-go2s4z5          py-six-1.10.0-gcc-6.3.0-p4dhkaw
binutils-2.28-gcc-4.8-5s7c6rs       libiconv-1.15-gcc-4.8-at46wg3              mawk-1.3.4-gcc-4.8-acjez57                  openssl-1.0.2k-gcc-4.8-dkls5tk           python-2.7.13-gcc-6.3.0-tyehea7
bison-3.0.4-gcc-4.8-ek4luo5         libpciaccess-0.13.4-gcc-6.3.0-gmufnvh      mawk-1.3.4-gcc-6.3.0-ostdoms                openssl-1.0.2k-gcc-6.3.0-gxgr5or         readline-7.0-gcc-4.8-xhufqhn
bzip2-1.0.6-gcc-4.8-iffrxzn         libsigsegv-2.11-gcc-4.8-pp2cvte            mpc-1.0.3-gcc-4.8-g5mztc5                   pcre-8.40-gcc-4.8-r5pbrxb                readline-7.0-gcc-6.3.0-zzcyicg
bzip2-1.0.6-gcc-6.3.0-bequudr       libsigsegv-2.11-gcc-6.3.0-7enifnh          mpfr-3.1.5-gcc-4.8-o7xm7az                  perl-5.24.1-gcc-4.8-dg5j65u              sqlite-3.8.5-gcc-6.3.0-6zoruzj
cmake-3.7.2-gcc-6.3.0-fowuuby       libtool-2.4.6-gcc-4.8-7a523za              mpich-3.2-gcc-6.3.0-dmvd3aw                 perl-5.24.1-gcc-6.3.0-6uzkpt6            tar-1.29-gcc-4.8-wse2ass
curl-7.53.1-gcc-4.8-3fz46n6         libtool-2.4.6-gcc-6.3.0-n7zmbzt            ncurses-6.0-gcc-4.8-dcpe7ia                 pkg-config-0.29.2-gcc-4.8-ib33t75        tcl-8.6.6-gcc-4.8-tfxzqbr
expat-2.2.0-gcc-4.8-mrv6bd4         libxml2-2.9.4-gcc-4.8-ryzxnsu              ncurses-6.0-gcc-6.3.0-ucbhcdy               pkg-config-0.29.2-gcc-6.3.0-jpgubk3      util-macros-1.19.1-gcc-6.3.0-xorz2x2
flex-2.6.3-gcc-4.8-yf345oo          libxml2-2.9.4-gcc-6.3.0-rltzsdh            netlib-lapack-3.6.1-gcc-6.3.0-js33dog       py-appdirs-1.4.0-gcc-6.3.0-jxawmw7       xz-5.2.3-gcc-4.8-mew4log
gcc-6.3.0-gcc-4.8-24puqve           lmod-7.4.1-gcc-4.8-je4srhr                 netlib-scalapack-2.0.2-gcc-6.3.0-5aidk4l    py-numpy-1.12.0-gcc-6.3.0-oemmoeu        xz-5.2.3-gcc-6.3.0-3vqeuvb
gettext-    lua-5.3.4-gcc-4.8-im75yaz                  netlib-scalapack-2.0.2-gcc-6.3.0-hjsemcn    py-packaging-16.8-gcc-6.3.0-i2n3dtl      zip-3.0-gcc-4.8-rwar22d
gmp-6.1.2-gcc-4.8-5ub2wu5           lua-luafilesystem-1_6_3-gcc-4.8-wkey3nl    netlib-scalapack-2.0.2-gcc-6.3.0-jva724b    py-pyparsing-2.1.10-gcc-6.3.0-tbo6gmw    zlib-1.2.11-gcc-4.8-pgxsxv7
help2man-1.47.4-gcc-4.8-kcnqmau     lua-luaposix-33.4.0-gcc-4.8-mdod2ry        netlib-scalapack-2.0.2-gcc-6.3.0-rgqfr6d    py-scipy-0.19.0-gcc-6.3.0-kr7nat4        zlib-1.2.11-gcc-6.3.0-7cqp6cj

The names should look familiar, as they resemble the output from spack find. You can use the modules here directly. For example, you could type either of these commands to load the cmake module:

$ use cmake-3.7.2-gcc-6.3.0-fowuuby
$ module load cmake-3.7.2-gcc-6.3.0-fowuuby

Neither of these is particularly pretty, easy to remember, or easy to type. Luckily, Spack has its own interface for using modules.

Shell support

To enable additional Spack commands for loading and unloading module files, and to add the correct path to MODULEPATH, you need to source the appropriate setup file in the $SPACK_ROOT/share/spack directory. This will activate shell support for the commands that need it. For bash, ksh or zsh users:

$ . ${SPACK_ROOT}/share/spack/

For csh and tcsh instead:

$ set SPACK_ROOT ...
$ source $SPACK_ROOT/share/spack/setup-env.csh

Note that in the latter case it is necessary to explicitly set SPACK_ROOT before sourcing the setup file (you will get a meaningful error message if you don’t).

When bash and ksh users update their environment with, it will check for spack-installed environment modules and add the module command to their environment; This only occurs if the module command is not already available. You can install environment-modules with spack bootstrap as described in Environment Modules.

Finally, if you want to have Spack’s shell support available on the command line at any login you can put this source line in one of the files that are sourced at startup (like .profile, .bashrc or .cshrc). Be aware though that the startup time may be slightly increased because of that.

spack load / unload

Once you have shell support enabled you can use the same spec syntax you’re used to and you can use the same shortened names you use everywhere else in Spack.

For example this will add the mpich package built with gcc to your path:

$ spack install mpich %gcc@4.4.7

# ... wait for install ...

$ spack load mpich %gcc@4.4.7
$ which mpicc

These commands will add appropriate directories to your PATH, MANPATH, CPATH, and LD_LIBRARY_PATH. When you no longer want to use a package, you can type unload or unuse similarly:

$ spack unload mpich %gcc@4.4.7


The load and unload subcommands are only available if you have enabled Spack’s shell support. These command DO NOT use the underlying Spack-generated module files.

Ambiguous specs

If a spec used with load/unload or is ambiguous (i.e. more than one installed package matches it), then Spack will warn you:

$ spack load libelf
==> Error: libelf matches multiple packages.
Matching packages:
  libelf@0.8.13%gcc@4.4.7 arch=linux-debian7-x86_64
  libelf@0.8.13%intel@15.0.0 arch=linux-debian7-x86_64
Use a more specific spec

You can either type the spack load command again with a fully qualified argument, or you can add just enough extra constraints to identify one package. For example, above, the key differentiator is that one libelf is built with the Intel compiler, while the other used gcc. You could therefore just type:

$ spack load libelf %intel

To identify just the one built with the Intel compiler.

spack module tcl loads

In some cases, it is desirable to use a Spack-generated module, rather than relying on Spack’s built-in user-environment modification capabilities. To translate a spec into a module name, use spack module tcl loads or spack module lmod loads depending on the module system desired.

To load not just a module, but also all the modules it depends on, use the --dependencies option. This is not required for most modules because Spack builds binaries with RPATH support. However, not all packages use RPATH to find their dependencies: this can be true in particular for Python extensions, which are currently not built with RPATH.

Scripts to load modules recursively may be made with the command:

$ spack module tcl loads --dependencies <spec>

An equivalent alternative using process substitution is:

$ source <( spack module tcl loads --dependencies <spec> )

Module Commands for Shell Scripts

Although Spack is flexible, the module command is much faster. This could become an issue when emitting a series of spack load commands inside a shell script. By adding the --dependencies flag, spack module tcl loads may also be used to generate code that can be cut-and-pasted into a shell script. For example:

$ spack module tcl loads --dependencies py-numpy git
# bzip2@1.0.6%gcc@4.9.3=linux-x86_64
module load bzip2-1.0.6-gcc-4.9.3-ktnrhkrmbbtlvnagfatrarzjojmkvzsx
# ncurses@6.0%gcc@4.9.3=linux-x86_64
module load ncurses-6.0-gcc-4.9.3-kaazyneh3bjkfnalunchyqtygoe2mncv
# zlib@1.2.8%gcc@4.9.3=linux-x86_64
module load zlib-1.2.8-gcc-4.9.3-v3ufwaahjnviyvgjcelo36nywx2ufj7z
# sqlite@3.8.5%gcc@4.9.3=linux-x86_64
module load sqlite-3.8.5-gcc-4.9.3-a3eediswgd5f3rmto7g3szoew5nhehbr
# readline@6.3%gcc@4.9.3=linux-x86_64
module load readline-6.3-gcc-4.9.3-se6r3lsycrwxyhreg4lqirp6xixxejh3
# python@3.5.1%gcc@4.9.3=linux-x86_64
module load python-3.5.1-gcc-4.9.3-5q5rsrtjld4u6jiicuvtnx52m7tfhegi
# py-setuptools@20.5%gcc@4.9.3=linux-x86_64
module load py-setuptools-20.5-gcc-4.9.3-4qr2suj6p6glepnedmwhl4f62x64wxw2
# py-nose@1.3.7%gcc@4.9.3=linux-x86_64
module load py-nose-1.3.7-gcc-4.9.3-pwhtjw2dvdvfzjwuuztkzr7b4l6zepli
# openblas@0.2.17%gcc@4.9.3+shared=linux-x86_64
module load openblas-0.2.17-gcc-4.9.3-pw6rmlom7apfsnjtzfttyayzc7nx5e7y
# py-numpy@1.11.0%gcc@4.9.3+blas+lapack=linux-x86_64
module load py-numpy-1.11.0-gcc-4.9.3-mulodttw5pcyjufva4htsktwty4qd52r
# curl@7.47.1%gcc@4.9.3=linux-x86_64
module load curl-7.47.1-gcc-4.9.3-ohz3fwsepm3b462p5lnaquv7op7naqbi
# autoconf@2.69%gcc@4.9.3=linux-x86_64
module load autoconf-2.69-gcc-4.9.3-bkibjqhgqm5e3o423ogfv2y3o6h2uoq4
# cmake@3.5.0%gcc@4.9.3~doc+ncurses+openssl~qt=linux-x86_64
module load cmake-3.5.0-gcc-4.9.3-x7xnsklmgwla3ubfgzppamtbqk5rwn7t
# expat@2.1.0%gcc@4.9.3=linux-x86_64
module load expat-2.1.0-gcc-4.9.3-6pkz2ucnk2e62imwakejjvbv6egncppd
# git@2.8.0-rc2%gcc@4.9.3+curl+expat=linux-x86_64
module load git-2.8.0-rc2-gcc-4.9.3-3bib4hqtnv5xjjoq5ugt3inblt4xrgkd

The script may be further edited by removing unnecessary modules.

Module Prefixes

On some systems, modules are automatically prefixed with a certain string; spack module tcl loads needs to know about that prefix when it issues module load commands. Add the --prefix option to your spack module tcl loads commands if this is necessary.

For example, consider the following on one system:

$ module avail

$ spack module tcl loads antlr    # WRONG!
# antlr@2.7.7%gcc@5.3.0~csharp+cxx~java~python arch=linux-SuSE11-x86_64
module load antlr-2.7.7-gcc-5.3.0-bdpl46y

$ spack module tcl loads --prefix linux-SuSE11-x86_64/ antlr
# antlr@2.7.7%gcc@5.3.0~csharp+cxx~java~python arch=linux-SuSE11-x86_64
module load linux-SuSE11-x86_64/antlr-2.7.7-gcc-5.3.0-bdpl46y

Module file customization

Module files are generated by post-install hooks after the successful installation of a package. The table below summarizes the essential information associated with the different file formats that can be generated by Spack:

  Hook name Default root directory Default template file Compatible tools
TCL - Non-Hierarchical tcl share/spack/modules share/spack/templates/modules/modulefile.tcl Env. Modules/LMod
Lua - Hierarchical lmod share/spack/lmod share/spack/templates/modules/modulefile.lua LMod

Spack ships with sensible defaults for the generation of module files, but you can customize many aspects of it to accommodate package or site specific needs. In general you can override or extend the default behavior by:

  1. overriding certain callback APIs in the Python packages
  2. writing specific rules in the modules.yaml configuration file
  3. writing your own templates to override or extend the defaults

The former method let you express changes in the run-time environment that are needed to use the installed software properly, e.g. injecting variables from language interpreters into their extensions. The latter two instead permit to fine tune the filesystem layout, content and creation of module files to meet site specific conventions.

Override API calls in

There are two methods that you can override in any to affect the content of the module files generated by Spack. The first one:

def setup_run_environment(self, env):

can alter the content of the module file associated with the same package where it is overridden. The second method:

def setup_dependent_run_environment(self, env, dependent_spec):

can instead inject run-time environment modifications in the module files of packages that depend on it. In both cases you need to fill run_env with the desired list of environment modifications.

The r package and callback APIs

An example in which it is crucial to override both methods is given by the r package. This package installs libraries and headers in non-standard locations and it is possible to prepend the appropriate directory to the corresponding environment variables:

LIBRARY_PATH self.prefix/rlib/R/lib
LD_LIBRARY_PATH self.prefix/rlib/R/lib
CPATH self.prefix/rlib/R/include

with the following snippet:

    def setup_run_environment(self, env):
                         join_path(self.prefix, 'rlib', 'R', 'lib'))
                         join_path(self.prefix, 'rlib', 'R', 'lib'))
                         join_path(self.prefix, 'rlib', 'R', 'include'))

The r package also knows which environment variable should be modified to make language extensions provided by other packages available, and modifies it appropriately in the override of the second method:

    def setup_dependent_run_environment(self, env, dependent_spec):
        # For run time environment set only the path for dependent_spec and
        # prepend it to R_LIBS
        if dependent_spec.package.extends(self.spec):
            env.prepend_path('R_LIBS', join_path(
                dependent_spec.prefix, self.r_lib_dir))

Write a configuration file

The configuration files that control module generation behavior are named modules.yaml. The default configuration:

# -------------------------------------------------------------------------
# This is the default configuration for Spack's module file generation.
# Settings here are versioned with Spack and are intended to provide
# sensible defaults out of the box. Spack maintainers should edit this
# file to keep it current.
# Users can override these settings by editing the following files.
# Per-spack-instance settings (overrides defaults):
#   $SPACK_ROOT/etc/spack/modules.yaml
# Per-user settings (overrides default and site settings):
#   ~/.spack/modules.yaml
# -------------------------------------------------------------------------
    - tcl
      - PATH
      - MANPATH
      - MANPATH
      - CPATH

      - mpi

activates the hooks to generate tcl module files and inspects the installation folder of each package for the presence of a set of subdirectories (bin, man, share/man, etc.). If any is found its full path is prepended to the environment variables listed below the folder name.

Activate other hooks

Any other module file generator shipped with Spack can be activated adding it to the list under the enable key in the module file. Currently the only generator that is not active by default is lmod, which produces hierarchical lua module files.

Each module system can then be configured separately. In fact, you should list configuration options that affect a particular type of module files under a top level key corresponding to the generator being customized:

    - tcl
    - lmod
    # contains environment modules specific customizations
    # contains lmod specific customizations

In general, the configuration options that you can use in modules.yaml will either change the layout of the module files on the filesystem, or they will affect their content. For the latter point it is possible to use anonymous specs to fine tune the set of packages on which the modifications should be applied.

Selection by anonymous specs

In the configuration file you can use anonymous specs (i.e. specs that are not required to have a root package and are thus used just to express constraints) to apply certain modifications on a selected set of the installed software. For instance, in the snippet below:

    # The keyword `all` selects every package
          BAR: 'bar'
    # This anonymous spec selects any package that
    # depends on openmpi. The double colon at the
    # end clears the set of rules that matched so far.
          BAR: 'baz'
    # Selects any zlib package
          LD_LIBRARY_PATH: 'foo'
    # Selects zlib compiled with gcc@4.8
        - FOOBAR

you are instructing Spack to set the environment variable BAR=bar for every module, unless the associated spec satisfies ^openmpi in which case BAR=baz. In addition in any spec that satisfies zlib the value foo will be prepended to LD_LIBRARY_PATH and in any spec that satisfies zlib%gcc@4.8 the variable FOOBAR will be unset.


Order does matter
The modifications associated with the all keyword are always evaluated first, no matter where they appear in the configuration file. All the other spec constraints are instead evaluated top to bottom.

Blacklist or whitelist specific module files

You can use anonymous specs also to prevent module files from being written or to force them to be written. Consider the case where you want to hide from users all the boilerplate software that you had to build in order to bootstrap a new compiler. Suppose for instance that gcc@4.4.7 is the compiler provided by your system. If you write a configuration file like:

    whitelist: ['gcc', 'llvm']  # Whitelist will have precedence over blacklist
    blacklist: ['%gcc@4.4.7']   # Assuming gcc@4.4.7 is the system compiler

you will prevent the generation of module files for any package that is compiled with gcc@4.4.7, with the only exception of any gcc or any llvm installation.

Customize the naming scheme

The names of environment modules generated by spack are not always easy to fully comprehend due to the long hash in the name. There are two module configuration options to help with that. The first is a global setting to adjust the hash length. It can be set anywhere from 0 to 32 and has a default length of 7. This is the representation of the hash in the module file name and does not affect the size of the package hash. Be aware that the smaller the hash length the more likely naming conflicts will occur. The following snippet shows how to set hash length in the module file names:

    hash_length: 7

To help make module names more readable, and to help alleviate name conflicts with a short hash, one can use the suffixes option in the modules configuration file. This option will add strings to modules that match a spec. For instance, the following config options,

        ^python@2.7.12: 'python-2.7.12'
        ^openblas: 'openblas'

will add a python-2.7.12 version string to any packages compiled with python matching the spec, python@2.7.12. This is useful to know which version of python a set of python extensions is associated with. Likewise, the openblas string is attached to any program that has openblas in the spec, most likely via the +blas variant specification.


TCL module files

A modification that is specific to tcl module files is the possibility to change the naming scheme of modules.

    naming_scheme: '{name}/{version}-{}-{compiler.version}'
        - '{name}'
        - 'intel/14.0.1'

will create module files that will conflict with intel/14.0.1 and with the base directory of the same module, effectively preventing the possibility to load two or more versions of the same software at the same time. The tokens that are available for use in this directive are the same understood by the format() method.


LMod hierarchical module files

When lmod is activated Spack will generate a set of hierarchical lua module files that are understood by LMod. The hierarchy will always contain the two layers Core / Compiler but can be further extended to any of the virtual dependencies present in Spack. A case that could be useful in practice is for instance:

    - lmod
      - 'gcc@4.8'
      - 'mpi'
      - 'lapack'

that will generate a hierarchy in which the lapack and mpi layer can be switched independently. This allows a site to build the same libraries or applications against different implementations of mpi and lapack, and let LMod switch safely from one to the other.


Deep hierarchies and lmod spider
For hierarchies that are deeper than three layers lmod spider may have some issues. See this discussion on the LMod project.

Filter out environment modifications

Modifications to certain environment variables in module files are there by default, for instance because they are generated by prefix inspections. If you want to prevent modifications to some environment variables, you can do so by using the environment blacklist:

        # Exclude changes to any of these variables
        environment_blacklist: ['CPATH', 'LIBRARY_PATH']

The configuration above will generate module files that will not contain modifications to either CPATH or LIBRARY_PATH.

Autoload dependencies

In some cases it can be useful to have module files that automatically load their dependencies. This may be the case for Python extensions, if not activated using spack activate:

      autoload: 'direct'

The configuration file above will produce module files that will load their direct dependencies if the package installed depends on python. The allowed values for the autoload statement are either none, direct or all. The default is none.


Building external software
Setting autoload to direct for all packages can be useful when building software outside of a Spack installation that depends on artifacts in that installation. E.g. (adjust lmod vs tcl as appropriate):
      autoload: 'direct'


TCL prerequisites
In the tcl section of the configuration file it is possible to use the prerequisites directive that accepts the same values as autoload. It will produce module files that have a prereq statement instead of automatically loading other modules.

Maintaining Module Files

Each type of module file has a command with the same name associated with it. The actions these commands permit are usually associated with the maintenance of a production environment. Here’s, for instance, a sample of the features of the spack module tcl command:

$ spack module tcl --help
usage: spack module tcl [-h] SUBCOMMAND ...

positional arguments:
    refresh   regenerate module files
    find      find module files for packages
    rm        remove module files
    loads     prompt the list of modules associated with a constraint

optional arguments:
  -h, --help  show this help message and exit

Refresh the set of modules

The subcommand that regenerates module files to update their content or their layout is refresh:

$ spack module tcl refresh --help
usage: spack module tcl refresh [-hy] [--delete-tree] [--upstream-modules] ...

positional arguments:
  installed_specs     constraint to select a subset of installed packages

optional arguments:
  -h, --help          show this help message and exit
  --delete-tree       delete the module file tree before refresh
  --upstream-modules  generate modules for packages installed upstream
  -y, --yes-to-all    assume "yes" is the answer to every confirmation request

A set of packages can be selected using anonymous specs for the optional constraint positional argument. Optionally the entire tree can be deleted before regeneration if the change in layout is radical.

Delete module files

If instead what you need is just to delete a few module files, then the right subcommand is rm:

$ spack module tcl rm --help
usage: spack module tcl rm [-hy] ...

positional arguments:
  installed_specs   constraint to select a subset of installed packages

optional arguments:
  -h, --help        show this help message and exit
  -y, --yes-to-all  assume "yes" is the answer to every confirmation request


We care about your module files!
Every modification done on modules that are already existing will ask for a confirmation by default. If the command is used in a script it is possible though to pass the -y argument, that will skip this safety measure.