nfsd service: use upstream systemd units

* Use /etc/nfs.conf as the recommended upstream way to configure services.
* Move server options to nfsd module.

nixos/modules/services/network-filesystems/nfsd.nix

@@ -20,6 +20,7 @@ in
 
       server = {
         enable = mkOption {
+          type = types.bool;
           default = false;
           description = ''
             Whether to enable the kernel's NFS server.
@@ -27,6 +28,7 @@ in
         };
 
         exports = mkOption {
+          type = types.lines;
           default = "";
           description = ''
             Contents of the /etc/exports file.  See
@@ -36,6 +38,7 @@ in
         };
 
         hostName = mkOption {
+          type = types.nullOr types.str;
           default = null;
           description = ''
             Hostname or address on which NFS requests will be accepted.
@@ -46,6 +49,7 @@ in
         };
 
         nproc = mkOption {
+          type = types.int;
           default = 8;
           description = ''
             Number of NFS server threads.  Defaults to the recommended value of 8.
@@ -53,11 +57,13 @@ in
         };
 
         createMountPoints = mkOption {
+          type = types.bool;
           default = false;
           description = "Whether to create the mount points in the exports file at startup time.";
         };
 
         mountdPort = mkOption {
+          type = types.nullOr types.int;
           default = null;
           example = 4002;
           description = ''
@@ -66,11 +72,26 @@ in
         };
 
         lockdPort = mkOption {
-          default = 0;
+          type = types.nullOr types.int;
+          default = null;
+          example = 4001;
           description = ''
-            Fix the lockd port number. This can help setting firewall rules for NFS.
+            Use a fixed port for the NFS lock manager kernel module
+            (<literal>lockd/nlockmgr</literal>).  This is useful if the
+            NFS server is behind a firewall.
           '';
         };
+
+        statdPort = mkOption {
+          type = types.nullOr types.int;
+          default = null;
+          example = 4000;
+          description = ''
+            Use a fixed port for <command>rpc.statd</command>. This is
+            useful if the NFS server is behind a firewall.
+          '';
+        };
+
       };
 
     };
@@ -82,61 +103,42 @@ in
 
   config = mkIf cfg.enable {
 
+    services.nfs.extraConfig = ''
+      [nfsd]
+      threads=${toString cfg.nproc}
+      ${optionalString (cfg.hostName != null) "host=${cfg.hostName}"}
+
+      [mountd]
+      ${optionalString (cfg.mountdPort != null) "port=${toString cfg.mountdPort}"}
+
+      [statd]
+      ${optionalString (cfg.statdPort != null) "port=${toString cfg.statdPort}"}
+
+      [lockd]
+      ${optionalString (cfg.lockdPort != null) ''
+        port=${toString cfg.lockdPort}
+        udp-port=${toString cfg.lockdPort}
+      ''}
+    '';
+
     services.rpcbind.enable = true;
 
     boot.supportedFilesystems = [ "nfs" ]; # needed for statd and idmapd
 
-    environment.systemPackages = [ pkgs.nfs-utils ];
-
     environment.etc.exports.source = exports;
 
-    boot.kernelModules = [ "nfsd" ];
-
-    systemd.services.nfsd =
-      { description = "NFS Server";
-
+    systemd.services.nfs-server =
+      { enable = true;
         wantedBy = [ "multi-user.target" ];
-
-        requires = [ "rpcbind.service" "mountd.service" ];
-        after = [ "rpcbind.service" "mountd.service" "idmapd.service" ];
-        before = [ "statd.service" ];
-
-        path = [ pkgs.nfs-utils ];
-
-        script =
-          ''
-            # Create a state directory required by NFSv4.
-            mkdir -p /var/lib/nfs/v4recovery
-
-            ${pkgs.procps}/sbin/sysctl -w fs.nfs.nlm_tcpport=${builtins.toString cfg.lockdPort}
-            ${pkgs.procps}/sbin/sysctl -w fs.nfs.nlm_udpport=${builtins.toString cfg.lockdPort}
-
-            rpc.nfsd \
-              ${if cfg.hostName != null then "-H ${cfg.hostName}" else ""} \
-              ${builtins.toString cfg.nproc}
-          '';
-
-        postStop = "rpc.nfsd 0";
-
-        serviceConfig.Type = "oneshot";
-        serviceConfig.RemainAfterExit = true;
       };
 
-    systemd.services.mountd =
-      { description = "NFSv3 Mount Daemon";
-
-        requires = [ "rpcbind.service" ];
-        after = [ "rpcbind.service" "local-fs.target" ];
-
-        path = [ pkgs.nfs-utils pkgs.sysvtools pkgs.utillinux ];
+    systemd.services.nfs-mountd =
+      { enable = true;
+        path = [ pkgs.nfs-utils ];
+        restartTriggers = [ exports ];
 
         preStart =
           ''
-            mkdir -p /var/lib/nfs
-            touch /var/lib/nfs/rmtab
-
-            mountpoint -q /proc/fs/nfsd || mount -t nfsd none /proc/fs/nfsd
-
             ${optionalString cfg.createMountPoints
               ''
                 # create export directories:
@@ -149,15 +151,6 @@ in
 
             exportfs -rav
           '';
-
-        restartTriggers = [ exports ];
-
-        serviceConfig.Type = "forking";
-        serviceConfig.ExecStart = ''
-          @${pkgs.nfs-utils}/sbin/rpc.mountd rpc.mountd \
-              ${if cfg.mountdPort != null then "-p ${toString cfg.mountdPort}" else ""}
-        '';
-        serviceConfig.Restart = "always";
       };
 
   };