nfsroot: export volumes not shares via nfs

hosts/containers/nfsroot/default.nix

@@ -1,6 +1,12 @@
 { zentralwerk, config, lib, pkgs, ... }:
 let
   netConfig = zentralwerk.lib.config.site.net.serv;
+
+  nfsExports = [
+    "var/lib/nfsroot/dacbert"
+    "var/lib/nfsroot/riscbert"
+    "var/lib/dump-dvb/whoopsie"
+  ];
 in {
   microvm = {
     hypervisor = "qemu";
@@ -17,7 +23,13 @@ in {
       tag = builtins.baseNameOf dir;
       proto = "virtiofs";
       socket = "${builtins.baseNameOf dir}.socket";
-    }) [ "etc" "home" "var" "var/lib/nfsroot/dacbert" "var/lib/nfsroot/riscbert" "var/lib/dump-dvb/whoopsie" ];
+    }) [ "etc" "home" "var" ];
+
+    volumes = map (export: {
+      mountPoint = "/${export}";
+      image = "/dev/zvol/${config.networking.hostName}/vm/nfsroot/${builtins.baseNameOf export}";
+      autoCreate = false;
+    }) nfsExports;
 
     interfaces = [ {
       type = "tap";
@@ -26,6 +38,10 @@ in {
     } ];
   };
 
+  fileSystems = builtins.foldl' (fileSystems: export: fileSystems // {
+    "/${export}".options = [ "relatime" "discard" ];
+  }) {} nfsExports;
+
   networking = {
     hostName = "nfsroot";