nix-collect-garbage 1 Nix nix-collect-garbage delete unreachable store paths nix-collect-garbage --delete-old -d --delete-older-than period --print-roots --print-live --print-dead --delete --dry-run 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 two additional options: -d (--delete-old), which 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); and --delete-older-than period, where period is a value such as 30d, which deletes all non-current generations that are older than the specified number of days in all profiles in /nix/var/nix/profiles. To delete from the Nix store everything that is not used by the current generations of each profile, do $ nix-collect-garbage -d