Fugaku, Japan’s flagship supercomputer, serves a diverse range of scientific disciplines, requiring extensive open-source software (OSS) support. However, managing OSS on Fugaku presents unique challenges due to its A64FX-based Arm architecture and Fujitsu’s proprietary compilers and libraries. Our team has been leveraging Spack to efficiently manage and maintain OSS. In this talk, we will share our experience using Spack on Fugaku, highlighting how it has enabled a robust and up-to-date OSS environment. We will discuss the practical benefits of Spack, including streamlined software deployment and simplified package management, and reflect on lessons learned from maintaining software in a large-scale HPC system. By sharing our insights, we aim to contribute to the broader Spack community and reinforce its role as a key tool for HPC software management.