Modern High Performance Computing systems are becoming larger and more heterogeneous. The proper management of software for the users of such systems poses a significant challenge. These users run very diverse applications that may be compiled with proprietary tools for specialized hardware. Moreover, the application life-cycle of these software may exceed the lifetime of the HPC systems themselves. These difficulties motivate the use of specialized package management systems. In this presentation, we outline an approach to HPC package development, deployment, management, sharing, and reuse based on the Nix functional package manager. We report our experience with this approach inside the GRICAD HPC center in Grenoble, France, and compare it to other existing approaches. --- After a PhD in applied mathematics, I have worked in the scientific computing field, with a strong HPC component.