Stefan Fiedler:

package/base/linux/linux.conf

@@ -492,7 +492,7 @@ main_lx() {
 	# just create a symlink to the default initrd image here; the file
 	# pointed to will be created by the rockinitrd postinstall script
 	if [ "$xpkg" = "$ROCKCFG_PKG_LINUX_DEFAULT" ]; then
-		ln -svf initrd-${lx_kernelrelease}.img /boot/initrd.img
+		ln -svf initrd-${lx_kernelrelease}.img $root/boot/initrd.img
 	fi
 }