diff --git a/modules/outputs/jffs2.nix b/modules/outputs/jffs2.nix
index 02c7c10..0a69a1f 100644
--- a/modules/outputs/jffs2.nix
+++ b/modules/outputs/jffs2.nix
@@ -5,7 +5,8 @@
 , ...
 }:
 let
-  inherit (lib) mkIf mkOption types;
+  inherit (pkgs) liminix;
+  inherit (lib) mkIf;
   o = config.system.outputs;
 in
 {
@@ -24,17 +25,10 @@ in
     };
     boot.initramfs.enable = true;
     system.outputs = {
-      rootfs =
-        let
-          inherit (pkgs.pkgsBuildBuild) runCommand mtdutils;
-          endian = if pkgs.stdenv.isBigEndian
-                   then "--big-endian" else "--little-endian";
-        in runCommand "make-jffs2" {
-          depsBuildBuild = [ mtdutils ];
-        } ''
-          tree=${o.bootablerootdir}
-          (cd $tree && mkfs.jffs2 --compression-mode=size ${endian} -e ${toString config.hardware.flash.eraseBlockSize} --enable-compressor=lzo --pad --root . --output $out --squash --faketime )
-        '';
+      rootfs = liminix.builders.jffs2 {
+        bootableRootDirectory = o.bootablerootdir;
+        inherit (config.hardware.flash) eraseBlockSize;
+      };
     };
   };
 }
diff --git a/modules/outputs/tftpboot.nix b/modules/outputs/tftpboot.nix
index 6d5bad9..ca51d10 100644
--- a/modules/outputs/tftpboot.nix
+++ b/modules/outputs/tftpboot.nix
@@ -5,10 +5,18 @@
 , ...
 }:
 let
-  inherit (lib) mkOption types concatStringsSep;
+  inherit (lib) mkOption mkIf types concatStringsSep;
+  inherit (pkgs) liminix;
   cfg = config.boot.tftp;
   hw = config.hardware;
   arch = pkgs.stdenv.hostPlatform.linuxArch;
+
+  # UBI cannot run on the top of phram.
+  needsSquashfs = config.rootfsType == "ubifs";
+  rootfstype = if needsSquashfs then "squashfs" else config.rootfsType;
+  rootfs = if needsSquashfs then
+    liminix.builders.squashfs config.filesystem.contents
+  else config.system.outputs.rootfs;
 in {
   imports = [ ../ramdisk.nix ];
   options.boot.tftp = {
@@ -74,6 +82,11 @@ in {
   config = {
     boot.ramdisk.enable = true;
 
+    kernel.config = mkIf needsSquashfs {
+      SQUASHFS = "y";
+      SQUASHFS_XZ = "y";
+    };
+
     system.outputs = rec {
       tftpboot-fit = 
       let
@@ -128,7 +141,7 @@ in {
             hex() { printf "0x%x" $1; }
 
             rootfsStart=${toString cfg.loadAddress}
-            rootfsSize=$(binsize64k ${o.rootfs} )
+            rootfsSize=$(binsize64k ${rootfs} )
             rootfsSize=$(($rootfsSize + ${toString cfg.freeSpaceBytes} ))
 
             ln -s ${o.manifest} manifest
@@ -142,13 +155,13 @@ in {
             dtbStart=$(($rootfsStart + $rootfsSize))
             ${if cfg.compressRoot
               then ''
-                lzma -z9cv ${o.rootfs} > rootfs.lz
+                lzma -z9cv ${rootfs} > rootfs.lz
                 rootfsLzStart=$dtbStart
                 rootfsLzSize=$(binsize rootfs.lz)
                 dtbStart=$(($dtbStart + $rootfsLzSize))
               ''
               else ''
-                ln -s ${o.rootfs} rootfs
+                ln -s ${rootfs} rootfs
               ''
              }
 
@@ -165,7 +178,7 @@ in {
             fdtput -p -t s dtb /reserved-memory/$node compatible phram
             fdtput -p -t lx dtb /reserved-memory/$node reg $ac_prefix $(hex $rootfsStart) $sz_prefix $(hex $rootfsSize)
 
-            cmd="liminix ${cmdline} mtdparts=phram0:''${rootfsSize}(rootfs) phram.phram=phram0,''${rootfsStart},''${rootfsSize},${toString config.hardware.flash.eraseBlockSize} root=/dev/mtdblock0";
+            cmd="liminix ${cmdline} mtdparts=phram0:''${rootfsSize}(rootfs) phram.phram=phram0,''${rootfsStart},''${rootfsSize},${toString config.hardware.flash.eraseBlockSize} rootfstype=${rootfstype} root=/dev/mtdblock0";
             fdtput -t s dtb /chosen ${config.boot.commandLineDtbNode} "$cmd"
 
             dtbSize=$(binsize ./dtb )
diff --git a/modules/outputs/ubivolume.nix b/modules/outputs/ubivolume.nix
index 1b9decc..45aa889 100644
--- a/modules/outputs/ubivolume.nix
+++ b/modules/outputs/ubivolume.nix
@@ -29,13 +29,6 @@ in
       };
       boot.initramfs.enable = true;
 
-      # In TFTP, the device named "rootfs" is the UBI device.
-      # We tell the kernel to load it.
-      # This avoids interference from the other UBI volumes.
-      boot.tftp.commandLine = [
-        "ubi.mtd=rootfs"
-      ];
-
       system.outputs.rootfs =
       let
         inherit (pkgs.pkgsBuildBuild) runCommand;
diff --git a/pkgs/default.nix b/pkgs/default.nix
index b63ab3a..7bb2470 100644
--- a/pkgs/default.nix
+++ b/pkgs/default.nix
@@ -13,6 +13,7 @@ in {
   liminix = {
     builders =  {
       squashfs = callPackage ./liminix-tools/builders/squashfs.nix {};
+      jffs2 = callPackage ./liminix-tools/builders/jffs2.nix {};
       dtb = callPackage ./kernel/dtb.nix {};
       uimage = callPackage ./kernel/uimage.nix {};
       kernel = callPackage ./kernel {};
diff --git a/pkgs/liminix-tools/builders/jffs2.nix b/pkgs/liminix-tools/builders/jffs2.nix
new file mode 100644
index 0000000..62378b4
--- /dev/null
+++ b/pkgs/liminix-tools/builders/jffs2.nix
@@ -0,0 +1,17 @@
+{
+  stdenv
+, busybox
+, buildPackages
+, callPackage
+, pseudofile
+, runCommand
+, writeText
+} : { eraseBlockSize, bootableRootDirectory }:
+let
+  endian = if stdenv.isBigEndian then "--big-endian" else "--little-endian";
+in runCommand "frob-jffs2" {
+    depsBuildBuild = [ buildPackages.mtdutils ];
+  } ''
+    tree=${bootableRootDirectory}
+    (cd $tree && mkfs.jffs2 --compression-mode=size ${endian} -e ${toString eraseBlockSize} --enable-compressor=lzo --pad --root . --output $out --squash --faketime)
+  ''