Move all of NixOS to nixos/ in preparation of the repository merge

nixos/modules/virtualisation/xen-domU.nix

@@ -0,0 +1,19 @@
+# Common configuration for Xen DomU NixOS virtual machines.
+
+{ config, pkgs, ... }:
+
+{
+  # We're being booted using pv-grub, which means that we need to
+  # generate a GRUB 1 menu without actually installing GRUB.
+  boot.loader.grub.version = 1;
+  boot.loader.grub.device = "nodev";
+  boot.loader.grub.extraPerEntryConfig = "root (hd0)";
+
+  boot.initrd.kernelModules = [ "xen-blkfront" ];
+
+  # Send syslog messages to the Xen console.
+  services.syslogd.tty = "hvc0";
+
+  # Don't run ntpd, since we should get the correct time from Dom0.
+  services.ntp.enable = false;
+}