# Talk proposal for Package Management devroom at FOSDEM'26 on Spack on top of EESSI

- deadline: Mon 1 Dec 2025
- see https://blog.ecosyste.ms/2025/11/06/fosdem-2026-package-managers-devroom-cfp.html
- Desired talk length (10/25 minutes): ?

## Title and subtitle

*Using Spack on top of EESSI: a tale of clashing packaging ecosystems*

## Abstract

Scientific computing software has always been a pain to build (from source), install, and run, especially for researchers, who often do not have a deep expertise in computer science and High-Performance Computing (HPC).
Managing numerical libraries and obscure dependencies that clash with each other is no easy feat, especially in an HPC environment. And even worse, modern supercomputers add complexity with diverse CPU/GPU architectures, making performance and portability not easy to attain. For HPC sysadmins, maintaining large scientific software stacks that are both up-do-date and optimized is an ongoing struggle.

Luckily, package management tools like [EasyBuild](https://easybuild.io) and [Spack](https://spack.io) emerged to ease this pain.
They automate builds through simple, human-readable Python recipes and enable the creation of common software stacks across heterogeneous platforms and CPU/GPU architectures. Both ecosystems have gained a lot of success, attracting growing communities of contributors and widespread adoption in HPC centers. Their extensive catalogs of build recipes and user-friendly workflows make these tools very attractive even to less experienced users.

More recently, the [European Environment for Scientific Software Installations](https://www.eessi.io) (EESSI) project introduced a shared stack of ready-to-use installations of scientific software that can be easily deployed across workstations, HPC clusters, and cloud infrastructure under a uniform user experience. EESSI is already being adopted by [an increasing number European HPC centers, and beyond](https://www.eessi.io/docs/systems/).
Under the hood, EESSI uses EasyBuild to build optimized software and libraries and exposes them in the form of environment modules. [CernVM-FS](https://cernvm.cern.ch/fs/) is used to distribute these software installations worldwide, providing an "on-demand streaming" access mechanism that is fully transparent to end users.

In this talk, we’ll explore what happens when you try to combine two packaging ecosystems: using Spack on top of EESSI by making Spack aware of EESSI’s software stack as an external database. This integration enables developers to leverage Spack’s flexibility while reusing EESSI’s optimized builds out of the box. Will they cooperate or clash? What lessons can we learn from this experiment? And could it inspire better interoperability and smoother user experience across HPC packaging tools?

## witty rewrite by Copilot ;)
Building scientific software has always been a rite of passage—one that most researchers would gladly skip. Wrestling with cryptic build systems, clashing dependencies, and obscure numerical libraries is hard enough. Throw in modern supercomputers with exotic CPU/GPU architectures, and suddenly performance and portability feel like mythical creatures. For HPC sysadmins, keeping massive software stacks current and optimized is less a job and more an endurance sport.

Enter the heroes: EasyBuild and Spack. These tools automate the pain away with human-readable Python recipes and portable stacks that work across heterogeneous platforms. Both have thriving communities, thousands of build recipes, and adoption that’s spreading faster than compiler warnings. Even newcomers can get complex software running without summoning ancient incantations.

Then came EESSI—a bold project offering a shared, ready-to-use scientific software stack that runs everywhere: laptops, HPC clusters, and the cloud. Under the hood, EasyBuild does the heavy lifting, while CernVM-FS streams software worldwide like Netflix for binaries. HPC centers across Europe (and beyond) are already tuning in.

In this talk, we’ll see what happens when two packaging titans collide: Spack meets EESSI. By making Spack aware of EESSI’s stack as an external database, we aim to combine Spack’s flexibility with EESSI’s out-of-the-box optimized builds. Will they play nice? Will sparks fly? And most importantly, could this experiment inspire a future where HPC packaging ecosystems actually get along?

## Submission notes (optional)

(These notes are meant for the organiser and won't be made public.)

## Speakers

- Loris Ercole (CECAM, EPFL, CH)
- Kenneth Hoste (University of Gent, BE)
- Todd Gamblin (LLNL, Livermore CA, USA)
- Massimiliano Culpo (np-complete S.r.l., IT)

## Software license(s)

- Spack: Apache-2.0, MIT
- EESSI: GPL-2.0

## talk slug (for URL on FOSDEM website)

- `spack-eessi`