Creating a spack.yaml file

Let's create a spack.yaml file that will allow us to create a Spack environment for compiling FluidSynth using CMake.

Below is a spack.yaml file which you can also find in the spack-config-templates repository inside the environment-templates sub-directory for the version of Spack you are using - called spack-cmake.yaml. Either copy and paste the below or grab the example from the repository, make sure it is named spack.yaml and save it into a directory of your choice for your environment. For the purposes of this tutorial I am going to save it as:

/gpfs/scratch/${USER}/spack-environments/spack-cmake/spack.yaml

(please create the directory first if it doesn't exist). This means the Spack environment will also be stored in /gpfs/scratch/${USER}/spack-environments/spack-cmake. You may wish to store your own environments in an alternative location if you need to keep them for longer. Please refer back to the Configuration overview page for further information.

Bash variables aren't expanded in prefix_inspections

Rather than using ${USER} or any other bash variables for prefix_inspections paths, you must use the full real path (i.e. use your actual username (abc123) not a variable).

Contents of spack.yaml (click to expand)

spack:
  concretizer:
    unify: true
  config:
    install_tree:
      root: /gpfs/scratch/${USER}/spack/apps
      projections:
        ^mpi: '{architecture}/{compiler.name}-{compiler.version}/{name}/{version}-{^mpi.name}-{^mpi.version}-{hash:7}'
        all: '{architecture}/{compiler.name}-{compiler.version}/{name}/{version}-{hash:7}'
    license_dir: /gpfs/scratch/${USER}/spack/licenses
    source_cache: /gpfs/scratch/${USER}/spack/cache
  modules:
    prefix_inspections:
      /gpfs/scratch/abc123/fluidsynth-install/bin:
      - PATH
      ./share/aclocal:
      - ACLOCAL_PATH
      ./lib:
      - LD_LIBRARY_PATH
      - LIBRARY_PATH
      ./lib64:
      - LD_LIBRARY_PATH
      - LIBRARY_PATH
      /gpfs/scratch/abc123/fluidsynth-install/lib64:
      - LD_LIBRARY_PATH
      - LIBRARY_PATH
      ./include:
      - C_INCLUDE_PATH
      - CPLUS_INCLUDE_PATH
      /gpfs/scratch/abc123/fluidsynth-install/include:
      - C_INCLUDE_PATH
      - CPLUS_INCLUDE_PATH
  packages:
    all:
      target: [x86_64_v4]
    gcc:
      externals:
      - spec: gcc@11.4.1 languages='c,c++,fortran'
        prefix: /usr
        extra_attributes:
          compilers:
            c: /usr/bin/gcc
            cxx: /usr/bin/g++
            fortran: /usr/bin/gfortran
      - spec: gcc@12.2.0 languages='c,c++,fortran'
        prefix: /share/apps/rocky9/spack/apps/linux-rocky9-x86_64_v4/gcc-11.4.1/gcc/12.2.0-6frskzg
        extra_attributes:
          compilers:
            c: /share/apps/rocky9/spack/apps/linux-rocky9-x86_64_v4/gcc-11.4.1/gcc/12.2.0-6frskzg/bin/gcc
            cxx: /share/apps/rocky9/spack/apps/linux-rocky9-x86_64_v4/gcc-11.4.1/gcc/12.2.0-6frskzg/bin/g++
            fortran: /share/apps/rocky9/spack/apps/linux-rocky9-x86_64_v4/gcc-11.4.1/gcc/12.2.0-6frskzg/bin/gfortran
          flags: {}
          environment: {}
          extra_rpaths: []
    openmpi:
      buildable: false
      prefer:
      - '@5.0.3 +gpfs'
      externals:
      - spec: "openmpi@5.0.3 +gpfs %gcc@12.2.0"
        prefix: /share/apps/rocky9/general/libs/openmpi/gcc/12.2.0/5.0.3
      - spec: "openmpi@5.0.3-nogpfs ~gpfs %gcc@12.2.0"
        prefix: /share/apps/rocky9/general/libs/openmpi/gcc/12.2.0/5.0.3-nogpfs
    ucx:
      buildable: false
      externals:
      - spec: "ucx@1.16.0%gcc@12.2.0"
        prefix: /share/apps/rocky9/general/libs/ucx/gcc/12.2.0/1.16.0
  repos:
    builtin:
      destination: /share/apps/rocky9/general/apps/spack-packages/2026.03.0
  specs:
    - cmake
    - gcc@12.2.0
    - glib
  upstreams:
    apocrita:
      install_tree: /share/apps/rocky9/spack/apps
  view:
    default:
      root: .spack-env/view

It's basically identical to our Python example apart from the specs list (which now has cmake, gcc@12.2.0 and glib). As before, the modules section sets the prefix_inspections: required to set the environment variables we are going to need for the manual compilation of FluidSynth using CMake. It also adds some additional paths to the modules: section, which we be explained later in this tutorial.