diff --git a/sw/.gitignore b/sw/.gitignore
index 09784aa..6f30340 100644
--- a/sw/.gitignore
+++ b/sw/.gitignore
@@ -1,4 +1,5 @@
 devicetree/devicetree.dtb
+buildroot_overlay/opt/
 downloads/
 buildroot-2023.02.8/
 u-boot/
diff --git a/sw/11_build_buildroot.sh b/sw/11_build_buildroot.sh
index 97604c8..5272a9b 100755
--- a/sw/11_build_buildroot.sh
+++ b/sw/11_build_buildroot.sh
@@ -7,6 +7,7 @@ set -e
 make -C "$BUILDROOT_DIR" clean
 
 cp -a config/buildroot_puzzlefw_defconfig "$BUILDROOT_DIR/.config"
+
 make -C "$BUILDROOT_DIR" olddefconfig
 make -C "$BUILDROOT_DIR"
 
diff --git a/sw/12_build_uboot.sh b/sw/12_build_uboot.sh
index 80cdc81..ee5653d 100755
--- a/sw/12_build_uboot.sh
+++ b/sw/12_build_uboot.sh
@@ -11,7 +11,7 @@ make -C "$UBOOT_DIR" CROSS_COMPILE=arm-linux- distclean
 # It contains the init code for the U-Boot SPL image.
 if [ ! -f "$XSA_FILE" ]; then
     echo "ERROR: $XSA_FILE not found" >&2
-    echo "Build the FPGA image before building U-Boot."
+    echo "       Build the FPGA image before building U-Boot." >&2
     exit 1
 fi
 
diff --git a/sw/13_build_kernel.sh b/sw/13_build_kernel.sh
index 86673a8..f9f1f44 100755
--- a/sw/13_build_kernel.sh
+++ b/sw/13_build_kernel.sh
@@ -5,17 +5,10 @@ set -e
 . script_env
 setup_toolchain
 
-#if [ ! -x "$TOOLCHAIN_DIR/arm-linux-gcc" ]; then
-#    echo "ERROR: Missing $TOOLCHAIN_DIR/arm-linux-gcc" >&2
-#    echo "       Build buildroot to prepare the arm-linux toolchain" >&2
-#    exit 1
-#fi
-#
-#export PATH="$TOOLCHAIN_DIR:$PATH"
-
 make -C "$LINUX_DIR" ARCH=arm mrproper
 
 cp -a config/linux_redpitaya_puzzlefw_defconfig "$LINUX_DIR/.config"
+
 make -C "$LINUX_DIR" ARCH=arm CROSS_COMPILE=arm-linux- olddefconfig
 make -C "$LINUX_DIR" ARCH=arm CROSS_COMPILE=arm-linux- zImage
 make -C "$LINUX_DIR" ARCH=arm CROSS_COMPILE=arm-linux- modules
diff --git a/sw/21_rebuild_rootfs.sh b/sw/21_rebuild_rootfs.sh
new file mode 100755
index 0000000..9341f23
--- /dev/null
+++ b/sw/21_rebuild_rootfs.sh
@@ -0,0 +1,19 @@
+#!/bin/bash
+
+set -e
+
+. script_env
+setup_toolchain
+
+TARGET=buildroot_overlay
+
+# Add kernel driver to rootfs image.
+mkdir -p "$TARGET/opt/puzzlefw/driver"
+cp -a src/linux_driver/puzzlefw.ko "$TARGET/opt/puzzlefw/driver"
+
+# Add userspace software to rootfs image.
+mkdir -p "$TARGET/opt/puzzlefw/bin"
+cp -a src/userspace/puzzlecmd "$TARGET/opt/puzzlefw/bin"
+
+make -C "$BUILDROOT_DIR"
+