On the heels of the NixOS 25.11 release, I reproduced the minimal
installation ISO again.
My approach is to take a NixOS VM from 2020, and then build the ISO (almost) without relying on the binary cache. This means it builds essentially all of the build-time dependencies and all of the items that make it into the ISO
from source, without directly relying on Nix-specific prebuilt packages. On the other hand, NixOS is somewhat less strict than for example Debian in
requiring package 'sources' are actually sources, so a few builds (notably go) are actually 'built' from upstream binary releases.
It's very satisfying to see such a long (albeit well-controlled) Rube Goldberg machine of builds results in a single hash that is identical to the one from the ISO you can download from the website.
Full write-up with all details at https://arnout.engelen.eu/blog/reproducing-nixos-25.11-minimal-iso/