i've been tempted by NixOS for servers but keep going back to Debian. the reproducibility is amazing in theory, but when you need to debug a DKMS kernel module build at 2am on a VPS, having "just apt install" is worth a lot. maybe NixOS for dev workstations, Debian for production VPS is the right split.
The reproducibility is amazing in reality: you either just run the misbehaving server’s config in a VM (one command) or spin up a throwaway VPS and apply the config to that (one command and about 60s). One of the major benefits of reproducibility is not having to poke at production machines because that’s the one place you can manifest the issue, now you can reproduce the in-production issues in a safe environment and fix them there.
I think the most interesting use case I have seen so far was for computers that control industrial equipment where you want identical installs on potentially dozens of machines.
