services.factorio.allowedPlayers

If non-empty, only these player names are allowed to connect. The game will not be able to save any changes made in-game with the /whitelist console command, though they will still take effect until the server is restarted.

If empty, the whitelist defaults to open, but can be managed with the in-game /whitelist console command (see: /help whitelist), which will cause changes to be saved to the game's state directory (see also: stateDirName).