Change:
<ins> { config, lib, pkgs, ... }: with lib; let cfg = config.services.dragonflydb; dragonflydb = pkgs.dragonflydb; settings = { port = cfg.port; dir = "/var/lib/dragonflydb"; keys_output_limit = cfg.keysOutputLimit; } // (lib.optionalAttrs (cfg.bind != null) { bind = cfg.bind; }) // (lib.optionalAttrs (cfg.requirePass != null) { requirepass = cfg.requirePass; }) // (lib.optionalAttrs (cfg.maxMemory != null) { maxmemory = cfg.maxMemory; }) // (lib.optionalAttrs (cfg.memcachePort != null) { memcache_port = cfg.memcachePort; }) // (lib.optionalAttrs (cfg.dbNum != null) { dbnum = cfg.dbNum; }) // (lib.optionalAttrs (cfg.cacheMode != null) { cache_mode = cfg.cacheMode; }); in { ###### interface options = { services.dragonflydb = { enable = mkEnableOption "DragonflyDB"; user = mkOption { type = types.str; default = "dragonfly"; description = "The user to run DragonflyDB as"; }; port = mkOption { type = types.port; default = 6379; description = "The TCP port to accept connections."; }; bind = mkOption { type = with types; nullOr str; default = "127.0.0.1"; description = '' The IP interface to bind to. <literal>null</literal> means "all interfaces". ''; }; requirePass = mkOption { type = with types; nullOr str; default = null; description = "Password for database"; example = "letmein!"; }; maxMemory = mkOption { type = with types; nullOr ints.unsigned; default = null; description = '' The maximum amount of memory to use for storage (in bytes). <literal>null</literal> means this will be automatically set. ''; }; memcachePort = mkOption { type = with types; nullOr port; default = null; description = '' To enable memcached compatible API on this port. <literal>null</literal> means disabled. ''; }; keysOutputLimit = mkOption { type = types.ints.unsigned; default = 8192; description = '' Maximum number of returned keys in keys command. <literal>keys</literal> is a dangerous command. We truncate its result to avoid blowup in memory when fetching too many keys. ''; }; dbNum = mkOption { type = with types; nullOr ints.unsigned; default = null; description = "Maximum number of supported databases for <literal>select</literal>"; }; cacheMode = mkOption { type = with types; nullOr bool; default = null; description = '' Once this mode is on, Dragonfly will evict items least likely to be stumbled upon in the future but only when it is near maxmemory limit. ''; }; }; }; ###### implementation config = mkIf config.services.dragonflydb.enable { users.users = optionalAttrs (cfg.user == "dragonfly") { dragonfly.description = "DragonflyDB server user"; dragonfly.isSystemUser = true; dragonfly.group = "dragonfly"; }; users.groups = optionalAttrs (cfg.user == "dragonfly") { dragonfly = { }; }; environment.systemPackages = [ dragonflydb ]; systemd.services.dragonflydb = { description = "DragonflyDB server"; wantedBy = [ "multi-user.target" ]; after = [ "network.target" ]; serviceConfig = { ExecStart = "${dragonflydb}/bin/dragonfly --alsologtostderr ${builtins.concatStringsSep " " (attrsets.mapAttrsToList (n: v: "--${n} ${strings.escapeShellArg v}") settings)}"; User = cfg.user; # Filesystem access ReadWritePaths = [ settings.dir ]; StateDirectory = "dragonflydb"; StateDirectoryMode = "0700"; # Process Properties LimitMEMLOCK = "infinity"; # Caps CapabilityBoundingSet = ""; NoNewPrivileges = true; # Sandboxing ProtectSystem = "strict"; ProtectHome = true; PrivateTmp = true; PrivateDevices = true; ProtectKernelTunables = true; ProtectKernelModules = true; ProtectControlGroups = true; LockPersonality = true; RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ]; RestrictRealtime = true; PrivateMounts = true; MemoryDenyWriteExecute = true; }; }; }; } </ins>

Discussion:
Project description Metadata homepage URL: source URL: license: Business Source License 1.1, change to Apache License 2.0 on June 1st 2027 platforms: linux
Can you check out my PR if everything works?