diff --git a/nixos/modules/installer/cd-dvd/installation-cd-base.nix b/nixos/modules/installer/cd-dvd/installation-cd-base.nix
index 89d50b7460c..e453a629f74 100644
--- a/nixos/modules/installer/cd-dvd/installation-cd-base.nix
+++ b/nixos/modules/installer/cd-dvd/installation-cd-base.nix
@@ -45,6 +45,9 @@ with lib;
   # Add support for cow filesystems and their utilities
   boot.supportedFilesystems = [ /* "zfs" */ "btrfs" ];
 
+  # Configure host id for ZFS to work
+  networking.hostId = "8425e349";
+
   # Allow the user to log in as root without a password.
   users.extraUsers.root.initialHashedPassword = "";
 }
diff --git a/nixos/modules/system/boot/stage-1-init.sh b/nixos/modules/system/boot/stage-1-init.sh
index 5a9beeeafa1..7ecc95aa079 100644
--- a/nixos/modules/system/boot/stage-1-init.sh
+++ b/nixos/modules/system/boot/stage-1-init.sh
@@ -122,6 +122,9 @@ for o in $(cat /proc/cmdline); do
     esac
 done
 
+# Set hostid before modules are loaded.
+# This is needed by the spl/zfs modules.
+@setHostId@
 
 # Load the required kernel modules.
 mkdir -p /lib
diff --git a/nixos/modules/system/boot/stage-1.nix b/nixos/modules/system/boot/stage-1.nix
index 33c9a70eb1b..45229e871ab 100644
--- a/nixos/modules/system/boot/stage-1.nix
+++ b/nixos/modules/system/boot/stage-1.nix
@@ -188,6 +188,15 @@ let
     fsInfo =
       let f = fs: [ fs.mountPoint (if fs.device != null then fs.device else "/dev/disk/by-label/${fs.label}") fs.fsType fs.options ];
       in pkgs.writeText "initrd-fsinfo" (concatStringsSep "\n" (concatMap f fileSystems));
+
+    setHostId = optionalString (config.networking.hostId != null) ''
+      hi="${config.networking.hostId}"
+      ${if pkgs.stdenv.isBigEndian then ''
+        echo -ne "\x''${hi:0:2}\x''${hi:2:2}\x''${hi:4:2}\x''${hi:6:2}" > /etc/hostid
+      '' else ''
+        echo -ne "\x''${hi:6:2}\x''${hi:4:2}\x''${hi:2:2}\x''${hi:0:2}" > /etc/hostid
+      ''}
+    '';
   };
 
 
diff --git a/nixos/modules/tasks/filesystems/zfs.nix b/nixos/modules/tasks/filesystems/zfs.nix
index aecda3e4101..ab5942b7945 100644
--- a/nixos/modules/tasks/filesystems/zfs.nix
+++ b/nixos/modules/tasks/filesystems/zfs.nix
@@ -51,19 +51,6 @@ in
   ###### interface
 
   options = {
-    boot.spl.hostid = mkOption {
-      default = "";
-      example = "0xdeadbeef";
-      description = ''
-        ZFS uses a system's hostid to determine if a storage pool (zpool) has been
-        imported on this system, and can thus be used again without reimporting.
-        Unfortunately, this hostid can change under linux from boot to boot (by
-        changing network adapters, for instance). Specify a unique 32 bit hostid in
-        hex here for zfs to prevent getting a random hostid between boots and having to
-        manually and forcibly reimport pools.
-      '';
-    };
-
     boot.zfs = {
       useGit = mkOption {
         type = types.bool;
@@ -196,6 +183,10 @@ in
   config = mkMerge [
     (mkIf enableZfs {
       assertions = [
+        {
+          assertion = config.networking.hostId != null;
+          message = "ZFS requires config.networking.hostId to be set";
+        }
         {
           assertion = !cfgZfs.forceImportAll || cfgZfs.forceImportRoot;
           message = "If you enable boot.zfs.forceImportAll, you must also enable boot.zfs.forceImportRoot";
@@ -205,9 +196,6 @@ in
       boot = {
         kernelModules = [ "spl" "zfs" ] ;
         extraModulePackages = [ splPkg zfsPkg ];
-        extraModprobeConfig = mkIf (cfgSpl.hostid != "") ''
-          options spl spl_hostid=${cfgSpl.hostid}
-        '';
       };
 
       boot.initrd = mkIf inInitrd {
diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
index 22b52f77b14..9579eaa77d0 100644
--- a/nixos/modules/tasks/network-interfaces.nix
+++ b/nixos/modules/tasks/network-interfaces.nix
@@ -189,6 +189,10 @@ let
 
   };
 
+  hexChars = stringToCharacters "0123456789abcdef";
+
+  isHexString = s: all (c: elem c hexChars) (stringToCharacters (toLower s));
+
 in
 
 {
@@ -205,6 +209,20 @@ in
       '';
     };
 
+    networking.hostId = mkOption {
+      default = null;
+      example = "4e98920d";
+      type = types.nullOr types.str;
+      description = ''
+        The 32-bit host ID of the machine, formatted as 8 hexadecimal characters.
+
+        You should try to make this ID unique among your machines. You can
+        generate a random 32-bit ID using the following command:
+
+        <literal>head -c4 /dev/urandom | od -A none -t x4</literal>
+      '';
+    };
+
     networking.enableIPv6 = mkOption {
       default = true;
       description = ''
@@ -513,10 +531,15 @@ in
   config = {
 
     assertions =
-      flip map interfaces (i: {
+      (flip map interfaces (i: {
         assertion = i.subnetMask == null;
         message = "The networking.interfaces.${i.name}.subnetMask option is defunct. Use prefixLength instead.";
-      });
+      })) ++ [
+        {
+          assertion = cfg.hostId == null || (stringLength cfg.hostId == 8 && isHexString cfg.hostId);
+          message = "Invalid value given to the networking.hostId option.";
+        }
+      ];
 
     boot.kernelModules = [ ]
       ++ optional cfg.enableIPv6 "ipv6"
@@ -872,14 +895,29 @@ in
     # clear it if it's not configured in the NixOS configuration,
     # since it may have been set by dhcpcd in the meantime.
     system.activationScripts.hostname =
-      optionalString (config.networking.hostName != "") ''
-        hostname "${config.networking.hostName}"
+      optionalString (cfg.hostName != "") ''
+        hostname "${cfg.hostName}"
       '';
     system.activationScripts.domain =
-      optionalString (config.networking.domain != "") ''
-        domainname "${config.networking.domain}"
+      optionalString (cfg.domain != "") ''
+        domainname "${cfg.domain}"
       '';
 
+    environment.etc = mkIf (cfg.hostId != null)
+      [
+        {
+          target = "hostid";
+          source = pkgs.runCommand "gen-hostid" {} ''
+            hi="${cfg.hostId}"
+            ${if pkgs.stdenv.isBigEndian then ''
+              echo -ne "\x''${hi:0:2}\x''${hi:2:2}\x''${hi:4:2}\x''${hi:6:2}" > $out
+            '' else ''
+              echo -ne "\x''${hi:6:2}\x''${hi:4:2}\x''${hi:2:2}\x''${hi:0:2}" > $out
+            ''}
+          '';
+        }
+      ];
+
     services.udev.extraRules =
       ''
         KERNEL=="tun", TAG+="systemd"
diff --git a/pkgs/stdenv/generic/default.nix b/pkgs/stdenv/generic/default.nix
index 038afc585c2..8b269ffb525 100644
--- a/pkgs/stdenv/generic/default.nix
+++ b/pkgs/stdenv/generic/default.nix
@@ -187,6 +187,7 @@ let
       isArm = system == "armv5tel-linux"
            || system == "armv6l-linux"
            || system == "armv7l-linux";
+      isBigEndian = system == "powerpc-linux";
 
       # For convenience, bring in the library functions in lib/ so
       # packages don't have to do that themselves.