diff --git a/Makefile b/Makefile
index f7cab05c86..83a6f3ce9f 100644
--- a/Makefile
+++ b/Makefile
@@ -40,14 +40,16 @@ export PX4_BASE		 := $(realpath $(dir $(lastword $(MAKEFILE_LIST))))/
 include $(PX4_BASE)makefiles/setup.mk
 
 #
-# Canned firmware configurations that we build.
+# Canned firmware configurations that we (know how to) build.
 #
-CONFIGS			?= $(subst config_,,$(basename $(notdir $(wildcard $(PX4_MK_DIR)config_*.mk))))
+KNOWN_CONFIGS		:= $(subst config_,,$(basename $(notdir $(wildcard $(PX4_MK_DIR)config_*.mk))))
+CONFIGS			?= $(KNOWN_CONFIGS)
 
 #
-# Boards that we build NuttX export kits for.
+# Boards that we (know how to) build NuttX export kits for.
 #
-BOARDS			:= $(subst board_,,$(basename $(notdir $(wildcard $(PX4_MK_DIR)board_*.mk))))
+KNOWN_BOARDS		:= $(subst board_,,$(basename $(notdir $(wildcard $(PX4_MK_DIR)board_*.mk))))
+BOARDS			?= $(KNOWN_BOARDS)
 
 #
 # Debugging
@@ -87,10 +89,11 @@ endif
 #
 # Built products
 #
-STAGED_FIRMWARES	 = $(foreach config,$(CONFIGS),$(IMAGE_DIR)$(config).px4)
-FIRMWARES		 = $(foreach config,$(CONFIGS),$(BUILD_DIR)$(config).build/firmware.px4)
+DESIRED_FIRMWARES 	 = $(foreach config,$(CONFIGS),$(IMAGE_DIR)$(config).px4)
+STAGED_FIRMWARES	 = $(foreach config,$(KNOWN_CONFIGS),$(IMAGE_DIR)$(config).px4)
+FIRMWARES		 = $(foreach config,$(KNOWN_CONFIGS),$(BUILD_DIR)$(config).build/firmware.px4)
 
-all:			$(STAGED_FIRMWARES)
+all:			$(DESIRED_FIRMWARES)
 
 #
 # Copy FIRMWARES into the image directory.
@@ -114,13 +117,26 @@ $(FIRMWARES): $(BUILD_DIR)%.build/firmware.px4:
 	@$(ECHO) %%%%
 	@$(ECHO) %%%% Building $(config) in $(work_dir)
 	@$(ECHO) %%%%
-	$(Q) mkdir -p $(work_dir)
-	$(Q) make -r -C $(work_dir) \
+	$(Q) $(MKDIR) -p $(work_dir)
+	$(Q) $(MAKE) -r -C $(work_dir) \
 		-f $(PX4_MK_DIR)firmware.mk \
 		CONFIG=$(config) \
 		WORK_DIR=$(work_dir) \
 		$(FIRMWARE_GOAL)
 
+#
+# Make FMU firmwares depend on the corresponding IO firmware.
+#
+# This is a pretty vile hack, since it hard-codes knowledge of the FMU->IO dependency
+# and forces the _default config in all cases. There has to be a better way to do this...
+#
+FMU_VERSION		 = $(patsubst px4fmu-%,%,$(word 1, $(subst _, ,$(1))))
+define FMU_DEP
+$(BUILD_DIR)$(1).build/firmware.px4: $(IMAGE_DIR)px4io-$(call FMU_VERSION,$(1))_default.px4
+endef
+FMU_CONFIGS		:= $(filter px4fmu%,$(CONFIGS))
+$(foreach config,$(FMU_CONFIGS),$(eval $(call FMU_DEP,$(config))))
+
 #
 # Build the NuttX export archives.
 #
@@ -147,12 +163,12 @@ $(ARCHIVE_DIR)%.export:	configuration = nsh
 $(NUTTX_ARCHIVES): $(ARCHIVE_DIR)%.export: $(NUTTX_SRC)
 	@$(ECHO) %% Configuring NuttX for $(board)
 	$(Q) (cd $(NUTTX_SRC) && $(RMDIR) nuttx-export)
-	$(Q) make -r -j1 -C $(NUTTX_SRC) -r $(MQUIET) distclean
+	$(Q) $(MAKE) -r -j1 -C $(NUTTX_SRC) -r $(MQUIET) distclean
 	$(Q) (cd $(NUTTX_SRC)/configs && $(COPYDIR) $(PX4_BASE)nuttx-configs/$(board) .)
 	$(Q) (cd $(NUTTX_SRC)tools && ./configure.sh $(board)/$(configuration))
 	@$(ECHO) %% Exporting NuttX for $(board)
-	$(Q) make -r -j1 -C $(NUTTX_SRC) -r $(MQUIET) CONFIG_ARCH_BOARD=$(board) export
-	$(Q) mkdir -p $(dir $@)
+	$(Q) $(MAKE) -r -j1 -C $(NUTTX_SRC) -r $(MQUIET) CONFIG_ARCH_BOARD=$(board) export
+	$(Q) $(MKDIR) -p $(dir $@)
 	$(Q) $(COPY) $(NUTTX_SRC)nuttx-export.zip $@
 	$(Q) (cd $(NUTTX_SRC)/configs && $(RMDIR) $(board))
 
@@ -168,11 +184,11 @@ BOARD			 = $(BOARDS)
 menuconfig: $(NUTTX_SRC)
 	@$(ECHO) %% Configuring NuttX for $(BOARD)
 	$(Q) (cd $(NUTTX_SRC) && $(RMDIR) nuttx-export)
-	$(Q) make -r -j1 -C $(NUTTX_SRC) -r $(MQUIET) distclean
+	$(Q) $(MAKE) -r -j1 -C $(NUTTX_SRC) -r $(MQUIET) distclean
 	$(Q) (cd $(NUTTX_SRC)/configs && $(COPYDIR) $(PX4_BASE)nuttx-configs/$(BOARD) .)
 	$(Q) (cd $(NUTTX_SRC)tools && ./configure.sh $(BOARD)/nsh)
 	@$(ECHO) %% Running menuconfig for $(BOARD)
-	$(Q) make -r -j1 -C $(NUTTX_SRC) -r $(MQUIET) menuconfig
+	$(Q) $(MAKE) -r -j1 -C $(NUTTX_SRC) -r $(MQUIET) menuconfig
 	@$(ECHO) %% Saving configuration file
 	$(Q)$(COPY) $(NUTTX_SRC).config $(PX4_BASE)nuttx-configs/$(BOARD)/nsh/defconfig
 else
@@ -191,7 +207,7 @@ $(NUTTX_SRC):
 # Testing targets
 #
 testbuild:
-	$(Q) (cd $(PX4_BASE) && make distclean && make archives && make -j8)
+	$(Q) (cd $(PX4_BASE) && $(MAKE) distclean && $(MAKE) archives && $(MAKE) -j8)
 
 #
 # Cleanup targets.  'clean' should remove all built products and force
@@ -206,8 +222,8 @@ clean:
 .PHONY:	distclean
 distclean: clean
 	$(Q) $(REMOVE) $(ARCHIVE_DIR)*.export
-	$(Q) make -C $(NUTTX_SRC) -r $(MQUIET) distclean
-	$(Q) (cd $(NUTTX_SRC)/configs && find . -maxdepth 1 -type l -delete)
+	$(Q) $(MAKE) -C $(NUTTX_SRC) -r $(MQUIET) distclean
+	$(Q) (cd $(NUTTX_SRC)/configs && $(FIND) . -maxdepth 1 -type l -delete)
 
 #
 # Print some help text
@@ -229,9 +245,9 @@ help:
 	@$(ECHO) "    A limited set of configs can be built with CONFIGS=<list-of-configs>"
 	@$(ECHO) ""
 	@for config in $(CONFIGS); do \
-		echo "  $$config"; \
-		echo "    Build just the $$config firmware configuration."; \
-		echo ""; \
+		$(ECHO) "  $$config"; \
+		$(ECHO) "    Build just the $$config firmware configuration."; \
+		$(ECHO) ""; \
 	done
 	@$(ECHO) "  clean"
 	@$(ECHO) "    Remove all firmware build pieces."
diff --git a/makefiles/config_px4fmu-v1_default.mk b/makefiles/config_px4fmu-v1_default.mk
index 8f2ade8dc8..0e4617f1db 100644
--- a/makefiles/config_px4fmu-v1_default.mk
+++ b/makefiles/config_px4fmu-v1_default.mk
@@ -6,6 +6,7 @@
 # Use the configuration's ROMFS.
 #
 ROMFS_ROOT	 = $(PX4_BASE)/ROMFS/px4fmu_common
+ROMFS_OPTIONAL_FILES = $(PX4_BASE)/Images/px4io-v1_default.bin
 
 #
 # Board support modules
diff --git a/makefiles/config_px4fmu-v2_default.mk b/makefiles/config_px4fmu-v2_default.mk
index 101b497125..61df64a78c 100644
--- a/makefiles/config_px4fmu-v2_default.mk
+++ b/makefiles/config_px4fmu-v2_default.mk
@@ -3,9 +3,11 @@
 #
 
 #
-# Use the configuration's ROMFS.
+# Use the configuration's ROMFS, copy the px4iov2 firmware into
+# the ROMFS if it's available
 #
 ROMFS_ROOT	 = $(PX4_BASE)/ROMFS/px4fmu_common
+ROMFS_OPTIONAL_FILES = $(PX4_BASE)/Images/px4io-v2_default.bin
 
 #
 # Board support modules
diff --git a/makefiles/firmware.mk b/makefiles/firmware.mk
index 8a027a0a81..b3e50501c7 100644
--- a/makefiles/firmware.mk
+++ b/makefiles/firmware.mk
@@ -322,7 +322,7 @@ endif
 # a root from several templates. That would be a nice feature.
 #
 
-# Add dependencies on anything in the ROMFS root
+# Add dependencies on anything in the ROMFS root directory
 ROMFS_FILES		+= $(wildcard \
 			     $(ROMFS_ROOT)/* \
 			     $(ROMFS_ROOT)/*/* \
@@ -334,7 +334,14 @@ ifeq ($(ROMFS_FILES),)
 $(error ROMFS_ROOT $(ROMFS_ROOT) specifies a directory containing no files)
 endif
 ROMFS_DEPS		+= $(ROMFS_FILES)
+
+# Extra files that may be copied into the ROMFS /extras directory
+# ROMFS_EXTRA_FILES are required, ROMFS_OPTIONAL_FILES are optional
+ROMFS_EXTRA_FILES	+= $(wildcard $(ROMFS_OPTIONAL_FILES))
+ROMFS_DEPS		+= $(ROMFS_EXTRA_FILES)
+
 ROMFS_IMG		 = romfs.img
+ROMFS_SCRATCH		 = romfs_scratch
 ROMFS_CSRC		 = $(ROMFS_IMG:.img=.c)
 ROMFS_OBJ		 = $(ROMFS_CSRC:.c=.o)
 LIBS			+= $(ROMFS_OBJ)
@@ -345,9 +352,18 @@ $(ROMFS_OBJ): $(ROMFS_IMG) $(GLOBAL_DEPS)
 	$(call BIN_TO_OBJ,$<,$@,romfs_img)
 
 # Generate the ROMFS image from the root
-$(ROMFS_IMG): $(ROMFS_DEPS) $(GLOBAL_DEPS)
+$(ROMFS_IMG): $(ROMFS_SCRATCH) $(ROMFS_DEPS) $(GLOBAL_DEPS)
 	@$(ECHO) "ROMFS:   $@"
-	$(Q) $(GENROMFS) -f $@ -d $(ROMFS_ROOT) -V "NSHInitVol"
+	$(Q) $(GENROMFS) -f $@ -d $(ROMFS_SCRATCH) -V "NSHInitVol"
+
+# Construct the ROMFS scratch root from the canonical root
+$(ROMFS_SCRATCH): $(ROMFS_DEPS) $(GLOBAL_DEPS)
+	$(Q) $(MKDIR) -p $(ROMFS_SCRATCH)
+	$(Q) $(COPYDIR) $(ROMFS_ROOT)/* $(ROMFS_SCRATCH)
+ifneq ($(ROMFS_EXTRA_FILES),)
+	$(Q) $(MKDIR) -p $(ROMFS_SCRATCH)/extras
+	$(Q) $(COPY) $(ROMFS_EXTRA_FILES) $(ROMFS_SCRATCH)/extras
+endif
 
 EXTRA_CLEANS		+= $(ROMGS_OBJ) $(ROMFS_IMG)
 
diff --git a/makefiles/setup.mk b/makefiles/setup.mk
index 168e41a5cb..51f830b6ee 100644
--- a/makefiles/setup.mk
+++ b/makefiles/setup.mk
@@ -71,6 +71,7 @@ export RMDIR		 = rm -rf
 export GENROMFS		 = genromfs
 export TOUCH		 = touch
 export MKDIR		 = mkdir
+export FIND		 = find
 export ECHO		 = echo
 export UNZIP_CMD	 = unzip
 export PYTHON		 = python
diff --git a/nuttx-configs/px4fmu-v1/nsh/defconfig b/nuttx-configs/px4fmu-v1/nsh/defconfig
index a7a6725c65..b8b98b1496 100644
--- a/nuttx-configs/px4fmu-v1/nsh/defconfig
+++ b/nuttx-configs/px4fmu-v1/nsh/defconfig
@@ -406,7 +406,7 @@ CONFIG_MAX_TASKS=32
 CONFIG_MAX_TASK_ARGS=10
 CONFIG_NPTHREAD_KEYS=4
 CONFIG_NFILE_DESCRIPTORS=32
-CONFIG_NFILE_STREAMS=25
+CONFIG_NFILE_STREAMS=8
 CONFIG_NAME_MAX=32
 CONFIG_PREALLOC_MQ_MSGS=4
 CONFIG_MQ_MAXMSGSIZE=32
diff --git a/nuttx-configs/px4fmu-v2/nsh/defconfig b/nuttx-configs/px4fmu-v2/nsh/defconfig
index 3e2a481087..e507c89baf 100644
--- a/nuttx-configs/px4fmu-v2/nsh/defconfig
+++ b/nuttx-configs/px4fmu-v2/nsh/defconfig
@@ -452,7 +452,7 @@ CONFIG_MAX_TASKS=32
 CONFIG_MAX_TASK_ARGS=10
 CONFIG_NPTHREAD_KEYS=4
 CONFIG_NFILE_DESCRIPTORS=32
-CONFIG_NFILE_STREAMS=25
+CONFIG_NFILE_STREAMS=8
 CONFIG_NAME_MAX=32
 CONFIG_PREALLOC_MQ_MSGS=4
 CONFIG_MQ_MAXMSGSIZE=32