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EasyBuild Framework Overview

Package Structure

The easybuild-framework package provides the following easybuild.* Python packages:

  • easybuild.framework is the core of EasyBuild, which contains the machinery to build and install software by processing EasyConfigs and their EasyBlocks.

  • is a toolbox of utilities used across the EasyBuild codebase (easybuild-framework and easybuild-easyblocks). Its functionality ranges from handling EasyBuild options and configuration, to file system operations, including the integration with GitHub, support for hooks, etc.

  • easybuild.toolchains contains all toolchain definitions.

Overview of the package structure of EasyBuild framework (v4.7.1) — easybuild.framework shown in blue and in orange: EasyBuild Framework package structure

Workflow Overview

The following diagram shows the main steps carried out by EasyBuild for a regular software installation with the eb command:

    easybuild.main --> tools
    robot --> build_install
    build_install --> easyblock

    state "" as tools{
        [*] --> options
        options --> parse_ec
        process_ec --> robot

        state "
        • parsing of options
        • set_up_configuration( )" as options

        state "
        • resolve_dependencies( )" as robot

    state "build_and_install_software( )" as build_install

    state "easybuild.framework.easyblock" as easyblock{
        [*] --> build_install_one
        build_install_one --> get_easyblock
        get_easyblock --> easyblock_class

        state "easybuild.framework.easyblock
        • build_and_install_one( )" as build_install_one

        state "class EasyBlock
        • run_all_steps( )" as easyblock_class

    state "easybuild.framework.easyconfig" as easyconfig{
        parse_ec --> process_ec

        state "
        • parse_easyconfigs( )" as parse_ec

        state "easybuild.framework.easyconfig.easyconfig
        • process_easyconfig( )" as process_ec

        state "easybuild.framework.easyconfig.easyconfig
        • get_easyblock_class( )" as get_easyblock

The process starts by calling the set_up_configuration function, which takes care of configuration options passed to EasyBuild. Either through the command line, configuration files or in the environment.

The scope of the EasyBuild execution is ultimately defined by the target easyconfig files given in the eb command. They will define the number of actions to carry out, such as software installations, fetching of sources or opening of PRs. Therefore, target easyconfig files are parsed early in the process, just after the runtime options have been resolved. The tooling to parse easyconfig files is located in a specific tools module in, while the EasyConfig class is found in easybuild.framework.easyconfig.easyconfig.

Once the easyconfig files are properly parsed, a common action is to resolve the dependencies for those installations with the --robot option. This is handled in which provides methods to search easyconfig files, resolve dependencies, and check conflicts between software packages.

The resolve_dependencies function returns an ordered list of all (parsed) easyconfigs that have to be installed to fulfill the dependency requirements of the requested installation (or throws an error if those dependencies cannot be fulfilled). EasyBuild will iterate over that list carrying out each installation in sequence.

The installation procedure of each software package is defined by the easyblock attached to it. This means that EasyBuild creates an EasyBlock instance for each individual installation and determines the easyblock to use from the easyconfig file. Once the EasyBlock instance is created, EasyBuild will call its run_all_steps() method to execute the installation steps defined for that software.

Step-wise Installation Procedure

flowchart LR
    subgraph source_phase [A. Setting up]
        direction TB
        parse[A1. Parse EasyConfig]
        fetch[A2. Fetch sources]
        check[A3. Check readiness]
        unpack[A4. Unpack sources]
        patch[A5. Apply patches]
        parse --> fetch
        fetch --> check
        check --> unpack
        unpack --> patch
    subgraph build_phase [B. Installing]
        direction TB
        prepare[B1. Prepare build]
        config[B2. Configure build]
        build[B3. Compile/build]
        test[B4. Test]
        install[B5. Install]
        prepare --> config
        config --> build
        build --> test
        test --> install
    subgraph ext_phase [Extensions]
        ext_install[Extension Install]
    subgraph clean_phase [C. Wrapping up]
        direction TB
        postinstall[C1. Post-Install]
        sanity[C2. Sanity check]
        clean[C3. Clean-up]
        module[C4. Make Module]
        perms[C5. Permissions]
        package[C6. Package]
        testcases[C7. Test Cases]
        postinstall --> sanity
        sanity --> clean
        clean --> module
        module --> perms
        perms --> package
        package --> testcases
    source_phase --> build_phase
    build_phase --> ext_phase
    ext_phase --> clean_phase

EasyBlock class

The base EasyBlock class in easybuild.framework.easyblock is a skeleton class that cannot carry out any installation on its own, but that lays the ground for child classes to define custom installation procedures. This does not mean that the EasyBlock class is an empty shell though, it is actually one of the biggest classes in EasyBuild with 4000+ lines of code (v4.7.x). It provides methods for generic actions that are useful in most installations, independently of the installation method.

Most of the steps in the initial Arrangement phase are already covered to some extent in the EasyBlock class, such as:

  • A2. Fetch sources: EasyBlock.fetch_sources, EasyBlock.fetch_patches, EasyBlock.obtain_file

  • A3. Check readiness: EasyBlock.make_buildir, EasyBlock.reset_env

  • A4. Unpack sources: EasyBlock.checksum_step, EasyBlock.extract_step

Several steps in the last Cleaning phase are already covered by the base EasyBlock as well:

  • C1. Post-Install: EasyBlock.run_post_install_commands, EasyBlock.apply_post_install_patches, EasyBlock.fix_shebang

  • C2. Sanity check: EasyBlock.sanity_check_step, EasyBlock.sanity_check_load_module, EasyBlock.sanity_check_linked_shared_libs

  • C3. Clean-up: EasyBlock.cleanup_step

  • C4. Env. Module: EasyBlock.make_module_step

  • C5. Permissions: EasyBlock.permissions_step

Therefore, custom easyblocks (child classes of EasyBlock) only need to define some of the steps in the Build and Install phase, the core of the workflow. Specifically, the configuration (B2), build (B3) and install (B4) steps are the only mandatory steps in custom easyblocks. Check the section Implementing EasyBlocks to start writing your own custom easyblocks.

Extension and ExtensionEasyBlock classes

The EasyBlock class has the machinery to trigger the installation of any extensions found in the easyconfig file. The method EasyBlock.run_all_steps always goes through EasyBlock.extensions_step which executes the installation of each extension instance in EasyBlock.ext_instances (if any).

The installation process in the extension step starts in EasyBlock.install_extensions, which will determine the installation approach for the extensions (sequential or parallel based on given options/support) and call the method of each extension instance. This run method is the one carrying out the actual installation of the extension and typically executes the install step of the parent EasyBlock with some extra actions before and/or after it. Nonetheless, custom easyblocks for extensions can fully redefine their run method.


In EasyBuild v5.0 the name of the method will be changed to a more meaningful and less generic name.

Framework also provides the ExtensionEasyBlock class which inherits from both EasyBlock and Extension. This class is useful for software that can be either installed standalone with their own easyconfig file or as an extension:

  • as extension: ExtensionEasyBlock uses the Extension class

  • stand-alone: ExtensionEasyBlock uses the EasyBlock class

For instance, PythonPackage, RPackage or PerlModule are generic easyblocks commonly used to install standalone packages or extensions of packages that use other easyblocks. You will find many examples of both cases in our easyblock-easyconfigs repository.

EasyConfig class

The EasyConfig class handles parsing and validating of easyconfig files. As such, EasyConfig is independent from EasyBlock and it is actually needed to determine the easyblock used in the installation of the target software package.

Once the target easyconfig file is read and all its parameters are validated, they will be accessible through different attributes and methods of the EasyConfig object. The main examples are:

  • returns the name of the package

  • EasyConfig.version returns the version of the package

  • EasyConfig.toolchain returns the toolchain used by the package

  • EasyConfig.dependencies() returns the list of dependencies


The EasyConfig instance is also accessible from the corresponding EasyBlock instance through its EasyBlock.cfg attribute.

EasyStack class


EasyStacks are an experimental feature in active development.

The machinery for EasyStacks is located in the easybuild.framework.easystack module. It contains:

  • EasyStackParser: class to parse the easystack files in YAML format

  • SoftwareSpecs: attribute class with the specs of each software package in the easystack

  • EasyStack: collection of SoftwareSpecs in the easystack

Toolchain mechanism

A toolchain in EasyBuild is much more than just a bundle of libraries and compilers to build and run software in a consistent environment. Toolchains are defined by their own classes built on top of the Toolchain class.

The base Toolchain class is defined in It does not only provide the attributes defining the toolchain (i.e. name and version) but also provides methods to setup the build environment with that toolchain :

  • set the environment of the toolchain: Toolchain.prepare

    • validate dependencies for the toolchain: Toolchain._check_dependencies

    • load modules of the toolchain: Toolchain._load_modules

    • set environment variables (e.g. $CC, $CFLAGS): Toolchain._setenv_variables

    • handle build options: Toolchain.prepare_rpath_wrappers, Toolchain.prepare_compiler_cache, Toolchain.handle_sysroot

Hence, the base Toolchain class provides the skeleton to further develop custom toolchain definitions through child classes. EasyBuild already provides many toolchains definitions that cover common and not-so-common combinations of compilers, numeric libraries and MPI implementations. All toolchain definitions are found in the easybuild.toolchains package of the EasyBuild framework.

Toolchains are modular. Each toolchain component (i.e compiler, numerical library, MPI implementation) is defined by its own child class or by multiple ones. These components are combined in sub-toolchains (e.g. the gompi toolchain) which can then be re-combined with other components in bigger toolchains (e.g. the foss toolchain). Therefore, the resulting options of the toolchain, its attributes and methods will be the combined result of all inherited class components.

    toolchain --> compiler & mpi & linalg & fft
    subgraph "Compiler"
        compiler --> gcc --> gcccore --> gcctoolchain 
    subgraph "MPI Implementation"
        mpi --> ompi 
    gcctoolchain & ompi --> gompi --> foss
    subgraph "Fast-Fourier Libraries"
        fft --> fftw 
    fftw --> foss
    subgraph "Linear Algebra Libraries"
        linalg --> oblas & fblas
        linalg --> blacs --> scalapack
    oblas & fblas & scalapack --> foss
    toolchain("class Toolchain")
    compiler("class Compiler")
    gcc("class Gcc
    gcccore("class GccCore
    gcctoolchain("class GccToolchain
    mpi("class Mpi")
    ompi("class OpenMPI
    gompi("class Gompi
    fft("class Fft")
    fftw("class Fftw
    linalg("class LinAlg")
    oblas("class OpenBLAS
    fblas("class FlexiBLAS
    blacs("class Blacs
    scalapack("class ScaLAPACK
    foss("class Foss

EasyBuild configuration options

Configuration options in EasyBuild can come from multiple sources:

  • command line arguments to the eb command
  • environment variables
  • settings in configuration files
  • settings in easyconfig files


Check the Configuring EasyBuild for details on how to use the different configuration mechanisms.

All configuration options in EasyBuild are defined in The EasyBuildOptions class gathers all options, including the name of the argument and its help string.

The module also handles the parsing of options through its set_up_configuration() method, which is called in the very early stages of the eb execution. The main step is parse_options() to read and validate the command line itself.

Once all options are parsed, those options listed in will be gathered in a singleton BuildOptions class. This class is the centralized location of configuration options for the current EasyBuild session. The method build_option() in provides a simple interface to it:

if build_option('ignore_test_failure'):
    print_warning("Test failure ignored")
    raise EasyBuildError("Test failure")

Therefore, adding a new option to eb and making that options available through build_option() is a two step process. First the option has to be added to EasyBuildOptions in and then also listed in As an example, you can check easybuild-framework#4226 which is a PR adding the download_timeout option to EasyBuild.

Features in

Environment modules

Interface provides the interface to the different environment module tools supported in EasyBuild. The ModulesTool class is an abstraction layer to interact with the environment modules in the host system.

Additionally, also provides methods to retrieve information about loaded software in the EasyBuild environment, such as get_software_root() or get_software_version(), which are extensively used in easyblocks.

Naming scheme contains the definitions of the module naming schemes (MNS) supported in EasyBuild. You will find in it one module per MNS. The structure of the naming scheme is defined in corresponding classes based on ModuleNamingScheme.

Module generator is the engine used by EasyBuild to write module files. It provides the ModuleGeneratorLua and ModuleGeneratorTcl classes for each of the supported module file formats. The module generator is mainly used in the make module step of the installation process.

Host system

System information provides a toolset to check multiple aspects of the underlying operative system, such as CPU specs, amount of memory, OS characteristics and system libraries.

Environment provides an interface to access and modify the environment in the host system.

File system provides multiple methods to interact with the underlying file system in the host. This abstraction layer sits on top of lower interfaces provided by the standard Python library.

Job schedulers contains the interfaces to the different job schedulers supported in EasyBuild.

Containers contains the interfaces to the different container systems supported in EasyBuild.

GitHub integration provides the interface to remote repositories in GitHub. It allows to fetch easyconfig files from PRs, open new PRs, upload test reports and several other maintainer actions on PRs.

Hooks contains the definition of all accessible hooks in EasyBuild. The actual call to the hooks defined by the user are spread across the steps of the installation process. Hence, this module is only interesting if you want to add or modify the available hooks.

Contributing to Framework

Reporting issues and bugs

Reporting issues and bugs to easybuild-framework is no different than to any other bug tracker. You should provide as many information as needed to allow the developers to reproduce your issue/bug, including:

  1. a description of what you are trying to do
  2. a description of the steps to reproduce the problem
  3. EasyBuild configuration and host system information
  4. custom easyblock or easyconfig files
  5. full error messages and tracebacks

In the case of EasyBuild, the main complication to report issues and bugs might be to determine if the issue/bug at hand does actually originate in easybuild-framework or if instead it belongs in easybuild-easyblocks or easybuild-easyconfigs. It is not uncommon that the traceback of bugs in easyblocks or easyconfigs reach the codebase in easybuild.framework or

Nevertheless, do not worry too much if you cannot determine which repository to target with your issue/bug. In case of doubt, easybuild-framework is the best bet in general and maintainers can move issues between EasyBuild repositories if needed.

Pull requests

Contributing bug fixes or new features to easybuild-framework is always welcomed. However, keep in mind that due to the broader scope of the source code in framework, making contributions might be a bit more complicated than for easyblocks and easyconfigs:

  • EasyBuild does not currently provide integration in the eb command to make contributions to the easybuild-framework repository. Therefore, as contributor, you have to manually fork easybuild-framework and open the pull request from your fork. The GitHub documentation contains a detailed description on how to create PRs from forks.

  • We recommend to link all new PRs in easybuild-framework to a corresponding issue in the issue tracker. Splitting the issue from the PR helps focus the activity in the PR to the changes in the source code and keep it separate from the discussion about the underlying problem.

  • The source code of easybuild-framework must be covered by the unit tests in test.framework and all tests must pass. You can run the unit tests in EasyBuild on your computer to check their results before opening the PR to our repository. In general, this requirement on unit tests has the following implications depending on the type of changes introduced in your PR:

    • Bug fix: the presence of a bug means that either that part of the codebase is currently uncovered by the tests or that it is already covered but tests are also buggy.

    • New feature: new unit tests have to be added covering the new feature.

    Therefore, in (almost) all cases, new PRs to framework have to also include related changes in unit tests. The suite of unit tests in framework is already very extensive and you will find all tests organized per module in the test/framework directory.

    If you are not familiar with writing tests in Python, you can find all the details in the unittest documentation. We also recommend the guide Getting Started With Testing in Python as a more comprehensive alternative.