Dear Qlustar Team, I apologise if this isn't the appropriate channel for such report. If there's a better place to direct this question, please let me know. I believe I've encountered a bug with the recent update of Spack in the Qlustar HPC Core Stack 24.06. After upgrading my Qlustar system (both chroot and head-node, using 'apt update' followed by 'apt upgrade'), I started receiving the following error when attempting to install packages with Spack: ==> Error: Package 'spack.pkg.builtin.zlib-api' not found. Use 'spack create' to create a new package. Did you mean one of the following packages? libkcapi grib-api libcap Upon investigation, I found a relevant change in Spack itself: https://github.com/spack/spack/commit/e51748ee8f89e0d3db4e426e3d04157129a456... This change introduces a new virtual 'zlib-api', which replaces 'zlib' in most packages to allow users to switch to zlib-ng by default for better performance. However, I noticed that the /etc/spack/defaults/package.json file was missing the definition of this virtual library. I added the line "zlib-api": ["zlib", "zlib-ng+compat"] to the file, but I'm still encountering the same error. What am I missing? How can I resolve this issue? For reproducibility purposes: - Spack version: 0.22.0 (previous version before the update 0.20) - Command I'm running: spack install r Furthermore, I believe this would affect most of the installation packages in Spack, since zlib is used in alot of them. Thank you for your assistance. Best regards, Tiago Almeida