nix-collect-garbage 1 Nix nix-collect-garbage delete unreachable store paths nix-collect-garbage --delete-old -d --print-roots --print-live --print-dead --delete The command nix-collect-garbage is mostly an alias of nix-store --gc, that is, it deletes all unreachable paths in the Nix store to clean up your system. However, it provides an additional option -d (--delete-old) that deletes all old generations of all profiles in /nix/var/nix/profiles by invoking nix-env --delete-generations old on all profiles. Of course, this makes rollbacks to previous configurations impossible. To delete from the Nix store everything that is not used by the current generations of each profile, do $ nix-collect-garbage -d