diff --git a/flake.nix b/flake.nix
index d461baf..baeeb65 100644
--- a/flake.nix
+++ b/flake.nix
@@ -61,10 +61,12 @@
       build = nixosconf.config.system.build;
     in pkgs.mkShell {
       pname = "lagarto-hun-shell";
+      TOPLEVEL = build.toplevel;
       OPENSBI = syspkgs.opensbi;
       KERNEL = build.kernel;
       INITRD = build.initialRamdisk;
       ROOTFS = build.sdImage;
+      UBOOT_ENV = syspkgs.uboot-env;
     };
   };
 }
diff --git a/fpga/upload.sh b/fpga/upload.sh
index adbcc4e..191e3cc 100755
--- a/fpga/upload.sh
+++ b/fpga/upload.sh
@@ -11,6 +11,7 @@ rsync -a fpga/env.sh "$dst"
 rsync "$OPENSBI/share/opensbi/lp64/fpga/openpiton/firmware/fw_payload.bin" "$dst/opensbi.bin"
 rsync "$KERNEL/Image" "$dst/kernel.bin"
 rsync "$INITRD/initrd" "$dst/initrd.bin"
-rsync "$ROOTFS/rootfs.img" "$dst/rootfs.img"
+rsync "$ROOTFS/sd-image/rootfs.img" "$dst/rootfs.img"
+rsync "$UBOOT_ENV" "$dst/uboot.env"
 
 echo "Now go to $dst and run ./boot.sh"
diff --git a/lagarto-hun.nix b/lagarto-hun.nix
index f7fbc76..1fececa 100644
--- a/lagarto-hun.nix
+++ b/lagarto-hun.nix
@@ -81,6 +81,30 @@
       '';
     };
 
+    uboot-env = let
+      init = "${config.system.build.toplevel}/init";
+      initrd = "${config.system.build.initialRamdisk}/initrd";
+    in prev.runCommand "uboot.txt" {} ''
+      cat > $out <<EOF
+      # Create pmem
+      fdt mknode / pmem@0x180000000
+      fdt set /pmem@0x180000000 compatible "pmem-region"
+      fdt set /pmem@0x180000000 reg <0x1 0x80000000 0x0 0x80000000>
+
+      # Reduce memory
+      fdt set /memory@80000000 reg <0x00000000 0x80000000 0x00000001 0x00000000>
+
+      # Set kernel options
+      setenv bootargs "root=/dev/ram0 loglevel=7 debug rw earlycon=sbi boot.trace console=hvc0 init=${init}"
+
+      EOF
+
+      # Populate the bood commands from the initrd size
+      echo "# Boot system" >> $out
+      echo "setenv ramdisk_size $(stat --format %s $(readlink -f ${initrd}))" >> $out
+      echo 'booti ''${kernel_addr_r} ''${ramdisk_addr_r}:''${ramdisk_size} ''${fdtcontroladdr}' >> $out
+    '';
+
     opensbi = prev.opensbi.overrideAttrs (old: {
       makeFlags = old.makeFlags ++ [
         "PLATFORM=fpga/openpiton"