diff --git a/Kconfig b/Kconfig
index bf1f1c7b4b3..4ea2ee47aff 100644
--- a/Kconfig
+++ b/Kconfig
@@ -60,7 +60,13 @@ config WINDOWS_CYGWIN
 	bool "Cygwin"
 	---help---
 		Build natively in a Cygwin environment with POSIX style paths (like
-		/cygdrive/c/cgywin/home)
+		/cygdrive/c/Program Files)
+
+config WINDOWS_UBUNTU
+	bool "Ubuntu under Windows10"
+	---help---
+		Build natively in an Unbuntu shell under Windoes 10 environment with
+		POSIX style paths (like /mnt/c/Program Files)
 
 config WINDOWS_MSYS
 	bool "MSYS"
diff --git a/README.txt b/README.txt
index 201bc35ed0a..24838ee4bdd 100644
--- a/README.txt
+++ b/README.txt
@@ -67,7 +67,7 @@ ENVIRONMENTS
       using MSYS.  People report to me that they have used MSYS
       successfully.  I suppose that the advantages of the MSYS environemnt
       is that it is closer to a native Windows environment and uses only a
-      minimal of add-on POSIX-ish tools.
+      minimal of add-on POSIX-land tools.
 
     - NuttX can also be installed and built on a native Windows system, but
       with some potential tool-related issues (see the discussion "Native
@@ -178,10 +178,7 @@ Ubuntu Bash under Windows 10
   the same directory would appear at "/cygdrive/c/Program Files".
 
   With these differences (perhaps a few other Windows quirks) the Ubuntu
-  install works just like Ubuntu running natively on your PC.  Currently
-  there is no host configuration for Bash running under Windows 10 but
-  setting the host to either Linux or Cygwin in your configuratino file
-  should work fine.
+  install works just like Ubuntu running natively on your PC.
 
   Accessing Ubuntu Files From Windows
   -----------------------------------
@@ -224,9 +221,9 @@ Ubuntu Bash under Windows 10
   ------------------------------
   If you want to integrate with Windows native tools, then you will need
   deal with the same kind of craziness as with integrating Cygwin with
-  native toolchains.  If you set the host PC to Cygwin in this case, then
-  the NuttX build system should deal with that craziness for you. See the
-  section "Cygwin Build Problems" below.
+  native toolchains.  But when you select a Windows native toolchain, the
+  NuttX build system should deal with most that craziness for you.   But not
+  all, see the section "Cygwin Build Problems" below.
 
 INSTALLATION
 ^^^^^^^^^^^^
diff --git a/arch/arm/src/arm/Toolchain.defs b/arch/arm/src/arm/Toolchain.defs
index d713e92e5da..199e118936f 100644
--- a/arch/arm/src/arm/Toolchain.defs
+++ b/arch/arm/src/arm/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/armv/Toolchain.defs
 #
-#   Copyright (C) 2012-2014 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2012-2014, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -129,6 +129,8 @@ ifeq ($(CONFIG_ARM_TOOLCHAIN),CODESOURCERYW)
   MAXOPTIMIZATION ?= -O2
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
@@ -139,6 +141,8 @@ ifeq ($(CONFIG_ARM_TOOLCHAIN),DEVKITARM)
   ARCROSSDEV ?= arm-eabi-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
@@ -158,5 +162,7 @@ ifeq ($(CONFIG_ARM_TOOLCHAIN),GNU_EABIW)
   MAXOPTIMIZATION ?= -Os
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
diff --git a/arch/arm/src/armv6-m/Toolchain.defs b/arch/arm/src/armv6-m/Toolchain.defs
index dfe5b9c9fdb..b3b1d3d7c0c 100644
--- a/arch/arm/src/armv6-m/Toolchain.defs
+++ b/arch/arm/src/armv6-m/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/armv6-m/Toolchain.defs
 #
-#   Copyright (C) 2013 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2013, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -107,6 +107,8 @@ ifeq ($(CONFIG_ARMV6M_TOOLCHAIN),ATOLLIC)
   ARCROSSDEV ?= arm-atollic-eabi-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   ARCHCPUFLAGS = -mcpu=cortex-m0 -mthumb -mfloat-abi=soft
 endif
@@ -134,6 +136,8 @@ ifeq ($(CONFIG_ARMV6M_TOOLCHAIN),CODEREDW)
   ARCROSSDEV ?= arm-none-eabi-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   ARCHCPUFLAGS = -mcpu=cortex-m0 -mthumb -mfloat-abi=soft
 endif
@@ -153,6 +157,8 @@ ifeq ($(CONFIG_ARMV6M_TOOLCHAIN),CODESOURCERYW)
   ARCROSSDEV ?= arm-none-eabi-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   ARCHCPUFLAGS = -mcpu=cortex-m0 -mthumb -mfloat-abi=soft
 endif
@@ -164,6 +170,8 @@ ifeq ($(CONFIG_ARMV6M_TOOLCHAIN),DEVKITARM)
   ARCROSSDEV ?= arm-eabi-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   ARCHCPUFLAGS = -mcpu=cortex-m0 -mthumb -mfloat-abi=soft
 endif
@@ -181,6 +189,8 @@ ifeq ($(CONFIG_ARMV6M_TOOLCHAIN),GNU_EABIW)
   ARCROSSDEV ?= arm-none-eabi-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   ARCHCPUFLAGS = -mcpu=cortex-m0 -mthumb -mfloat-abi=soft
 endif
diff --git a/arch/arm/src/armv7-a/Toolchain.defs b/arch/arm/src/armv7-a/Toolchain.defs
index 8ee6efdf2ad..329abba970f 100644
--- a/arch/arm/src/armv7-a/Toolchain.defs
+++ b/arch/arm/src/armv7-a/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/armv7-a/Toolchain.defs
 #
-#   Copyright (C) 2013 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2013, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -129,6 +129,8 @@ ifeq ($(CONFIG_ARMV7A_TOOLCHAIN),CODESOURCERYW)
   MAXOPTIMIZATION ?= -O2
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
@@ -139,6 +141,8 @@ ifeq ($(CONFIG_ARMV7A_TOOLCHAIN),DEVKITARM)
   ARCROSSDEV ?= $(TARGET_ARCH)-eabi-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
@@ -158,5 +162,7 @@ ifeq ($(CONFIG_ARMV7A_TOOLCHAIN),GNU_EABIW)
   MAXOPTIMIZATION ?= -Os
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
diff --git a/arch/arm/src/armv7-m/Toolchain.defs b/arch/arm/src/armv7-m/Toolchain.defs
index 8cfcaa3e1d4..262f79c4de3 100644
--- a/arch/arm/src/armv7-m/Toolchain.defs
+++ b/arch/arm/src/armv7-m/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/armv7-m/Toolchain.defs
 #
-#   Copyright (C) 2012-2013, 2015-2016 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2012-2013, 2015-2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -167,6 +167,8 @@ ifeq ($(CONFIG_ARMV7M_TOOLCHAIN),ATOLLIC)
   ARCHCPUFLAGS = $(TOOLCHAIN_MCPU) -mthumb $(TOOLCHAIN_MFLOAT)
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
@@ -203,6 +205,8 @@ ifeq ($(CONFIG_ARMV7M_TOOLCHAIN),CODEREDW)
   ARCHCPUFLAGS = $(TOOLCHAIN_MCPU) -mthumb $(TOOLCHAIN_MFLOAT)
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
@@ -224,6 +228,8 @@ ifeq ($(CONFIG_ARMV7M_TOOLCHAIN),CODESOURCERYW)
   ARCHCPUFLAGS = $(TOOLCHAIN_MCPU) -mthumb $(TOOLCHAIN_MFLOAT)
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
@@ -234,6 +240,8 @@ ifeq ($(CONFIG_ARMV7M_TOOLCHAIN),DEVKITARM)
   ARCROSSDEV ?= arm-none-eabi-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   ARCHCPUFLAGS = $(TOOLCHAIN_MCPU) -mthumb $(TOOLCHAIN_MFLOAT)
 endif
@@ -256,6 +264,8 @@ ifeq ($(CONFIG_ARMV7M_TOOLCHAIN),GNU_EABIW)
   ARCHCPUFLAGS = $(TOOLCHAIN_MCPU) -mthumb $(TOOLCHAIN_MFLOAT)
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
@@ -266,6 +276,8 @@ ifeq ($(CONFIG_ARMV7M_TOOLCHAIN),RAISONANCE)
   ARCROSSDEV ?= arm-none-eabi-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   ARCHCPUFLAGS = $(TOOLCHAIN_MCPU) -mthumb $(TOOLCHAIN_MFLOAT)
 endif
diff --git a/arch/arm/src/armv7-r/Toolchain.defs b/arch/arm/src/armv7-r/Toolchain.defs
index f1eb9db8170..09aab784409 100644
--- a/arch/arm/src/armv7-r/Toolchain.defs
+++ b/arch/arm/src/armv7-r/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/arm/src/armv7-r/Toolchain.defs
 #
-#   Copyright (C) 2015 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2015, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -129,6 +129,8 @@ ifeq ($(CONFIG_ARMV7R_TOOLCHAIN),CODESOURCERYW)
   MAXOPTIMIZATION ?= -O2
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
@@ -139,6 +141,8 @@ ifeq ($(CONFIG_ARMV7R_TOOLCHAIN),DEVKITARM)
   ARCROSSDEV ?= $(TARGET_ARCH)-eabi-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
@@ -158,5 +162,7 @@ ifeq ($(CONFIG_ARMV7R_TOOLCHAIN),GNU_EABIW)
   MAXOPTIMIZATION ?= -Os
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
diff --git a/arch/avr/src/avr/Toolchain.defs b/arch/avr/src/avr/Toolchain.defs
index 7503086fb07..eea11e441af 100644
--- a/arch/avr/src/avr/Toolchain.defs
+++ b/arch/avr/src/avr/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/avr/src/avr/Toolchain.defs
 #
-#   Copyright (C) 2012-2013 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2012-2013, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -134,6 +134,8 @@ ifeq ($(_WINAVR),1)
   CROSSDEV ?= avr-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   MAXOPTIMIZATION ?= -O2
   LDFLAGS += -nostartfiles -nodefaultlibs
diff --git a/arch/avr/src/avr32/Toolchain.defs b/arch/avr/src/avr32/Toolchain.defs
index b0a40e34b30..68f9c7045b0 100644
--- a/arch/avr/src/avr32/Toolchain.defs
+++ b/arch/avr/src/avr32/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/avr/src/avr32/Toolchain.defs
 #
-#   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2012, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -62,6 +62,8 @@ endif
 ifeq ($(CONFIG_AVR32_TOOLCHAIN),AVRTOOLSW)
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 else
   # AVR Tools or avr32-toolchain from https://github.com/jsnyder/avr32-toolchain
diff --git a/arch/mips/src/mips32/Toolchain.defs b/arch/mips/src/mips32/Toolchain.defs
index cee45311d8e..3e2947a7e1a 100644
--- a/arch/mips/src/mips32/Toolchain.defs
+++ b/arch/mips/src/mips32/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/mips/src/mips32/Toolchain.defs
 #
-#   Copyright (C) 2012-2013, 2015 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2012-2013, 2015, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -178,6 +178,8 @@ ifeq ($(CONFIG_MIPS32_TOOLCHAIN),MICROCHIPW_XC32)
   CROSSDEV ?= xc32-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 ifeq ($(CONFIG_MIPS32_TOOLCHAIN_MICROCHIP_XC32_LICENSED),y)
   MAXOPTIMIZATION ?= -O2
@@ -193,6 +195,8 @@ ifeq ($(CONFIG_MIPS32_TOOLCHAIN),MICROCHIPW)
   CROSSDEV ?= pic32-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   MAXOPTIMIZATION ?= -O2
   ARCHCPUFLAGS = -mprocessor=$(MIPS_MPROCESSOR) $(MIPS_MICROMIPS) -mno-float -mlong32 -membedded-data
@@ -219,6 +223,8 @@ ifeq ($(CONFIG_MIPS32_TOOLCHAIN),MICROCHIPW_LITE)
   # CROSSDEV ?= xc32-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   # MAXOPTIMIZATION ?= -O2
   ARCHCPUFLAGS = -mprocessor=$(MIPS_MPROCESSOR) $(MIPS_MICROMIPS) -mno-float -mlong32 -membedded-data
@@ -245,6 +251,8 @@ ifeq ($(CONFIG_MIPS32_TOOLCHAIN),PINGUINOW)
   CROSSDEV ?= p32-
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
   MAXOPTIMIZATION ?= -O2
   ARCHCPUFLAGS = -mlong32 -membedded-data -msoft-float -march=$(MIPS_MARCH) $(MIPS_MICROMIPS) -EL
diff --git a/arch/misoc/src/lm32/Toolchain.defs b/arch/misoc/src/lm32/Toolchain.defs
index f59fa1ab45e..f7c7c1adf9e 100644
--- a/arch/misoc/src/lm32/Toolchain.defs
+++ b/arch/misoc/src/lm32/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/misco/src/lm32/Toolchain.defs
 #
-#   Copyright (C) 2016 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2016-2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -100,5 +100,7 @@ ifeq ($(CONFIG_LM32_TOOLCHAIN),GNUW)
   MAXOPTIMIZATION ?= -Os
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
diff --git a/arch/sim/Kconfig b/arch/sim/Kconfig
index 975d0449a5b..5168c7796eb 100644
--- a/arch/sim/Kconfig
+++ b/arch/sim/Kconfig
@@ -37,7 +37,7 @@ config SIM_CYGWIN_DECORATED
 	default n
 	depends on WINDOWS_CYGWIN
 	---help---
-		Older versions of Cygwin toolsdecorated C symbol names by adding an
+		Older versions of Cygwin tools decorated C symbol names by adding an
 		underscore to the beginning of the symbol name.  Newer versions of
 		Cygwin do not seem to do this.
 
diff --git a/arch/z80/src/ez80/Toolchain.defs b/arch/z80/src/ez80/Toolchain.defs
index bc68e4782dd..257a37d995c 100644
--- a/arch/z80/src/ez80/Toolchain.defs
+++ b/arch/z80/src/ez80/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/z80/src/ez80/Toolchain.defs
 #
-#   Copyright (C) 2012, 2016 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2012, 2016-2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -44,4 +44,6 @@ CONFIG_EZ80_TOOLCHAIN ?= ZDSII
 
 ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
   WINTOOL = y
+else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+  WINTOOL = y
 endif
diff --git a/arch/z80/src/z180/Toolchain.defs b/arch/z80/src/z180/Toolchain.defs
index cf97558ffca..ed57fff794f 100644
--- a/arch/z80/src/z180/Toolchain.defs
+++ b/arch/z80/src/z180/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/z80/src/z180/Toolchain.defs
 #
-#   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2012, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -69,6 +69,8 @@ endif
 ifeq ($(CONFIG_AVR_TOOLCHAIN),SDCCWIN32)
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
diff --git a/arch/z80/src/z8/Toolchain.defs b/arch/z80/src/z8/Toolchain.defs
index 9aaf1b89ced..e1f5cb64207 100644
--- a/arch/z80/src/z8/Toolchain.defs
+++ b/arch/z80/src/z8/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/z80/src/z8/Toolchain.defs
 #
-#   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2012, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -44,4 +44,6 @@ CONFIG_Z8_TOOLCHAIN ?= ZDSII
 
 ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
   WINTOOL = y
+else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+  WINTOOL = y
 endif
diff --git a/arch/z80/src/z80/Toolchain.defs b/arch/z80/src/z80/Toolchain.defs
index 90fc9944ad2..9c0776247a0 100644
--- a/arch/z80/src/z80/Toolchain.defs
+++ b/arch/z80/src/z80/Toolchain.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # arch/z80/src/z80/Toolchain.defs
 #
-#   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2012, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -69,6 +69,8 @@ endif
 ifeq ($(CONFIG_AVR_TOOLCHAIN),SDCCWIN32)
   ifeq ($(CONFIG_WINDOWS_CYGWIN),y)
     WINTOOL = y
+  else ifeq ($(CONFIG_WINDOWS_UBUNTU),y)
+    WINTOOL = y
   endif
 endif
 
diff --git a/tools/sethost.sh b/tools/sethost.sh
index 085361f5b68..ba7848e0427 100755
--- a/tools/sethost.sh
+++ b/tools/sethost.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 # tools/sethost.sh
 #
-#   Copyright (C) 2016 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2016-2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -42,13 +42,14 @@ unset configfile
 
 function showusage {
     echo ""
-    echo "USAGE: $progname [-w|l] [-c|n] [-32|64] [<config>]"
+    echo "USAGE: $progname [-w|l] [-c|u|n] [-32|64] [<config>]"
     echo "       $progname -h"
     echo ""
     echo "Where:"
     echo "  -w|l selects Windows (w) or Linux (l).  Default: Linux"
-    echo "  -c|n selects Windows native (n) or Cygwin (c).  Default Cygwin"
-    echo "  -32|64 selects 32- or 64-bit host (Only for Cygwin).  Default 64"
+    echo "  -c|u|n selects Windows environment option:  Cygwin (c), Ubuntu under"
+    echo "     Windows 10 (u), or Windows native (n).  Default Cygwin"
+    echo "  -32|64 selects 32- or 64-bit host.  Default 64"
     echo "  -h will show this help test and terminate"
     echo "  <config> selects configuration file.  Default: .config"
     exit 1
@@ -67,6 +68,9 @@ while [ ! -z "$1" ]; do
     -c )
     wenv=cygwin
     ;;
+    -u )
+    wenv=ubuntu
+    ;;
     -n )
     wenv=native
     ;;
@@ -170,6 +174,7 @@ if [ "X$host" == "Xlinux" ]; then
 
     kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_NATIVE
     kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_CYGWIN
+    kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_UBUNTU
     kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_MSYS
     kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_OTHER
 
@@ -184,11 +189,19 @@ else
     if [ "X$wenv" == "Xcygwin" ]; then
       echo "  Select CONFIG_WINDOWS_CYGWIN=y"
       kconfig-tweak --file $nuttx/.config --enable CONFIG_WINDOWS_CYGWIN
+      kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_UBUNTU
       kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_NATIVE
     else
-      echo "  Select CONFIG_WINDOWS_NATIVE=y"
-      kconfig-tweak --file $nuttx/.config --enable CONFIG_WINDOWS_NATIVE
       kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_CYGWIN
+      if [ "X$wenv" == "Xubuntu" ]; then
+        echo "  Select CONFIG_WINDOWS_UBUNTU=y"
+        kconfig-tweak --file $nuttx/.config --enable CONFIG_WINDOWS_UBUNTU
+        kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_NATIVE
+      else
+        echo "  Select CONFIG_WINDOWS_NATIVE=y"
+        kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_UBUNTU
+        kconfig-tweak --file $nuttx/.config --enable CONFIG_WINDOWS_NATIVE
+      fi
     fi
 
     kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_MSYS
diff --git a/tools/testbuild.sh b/tools/testbuild.sh
index 775dcab3fb9..75e0e3b57c0 100755
--- a/tools/testbuild.sh
+++ b/tools/testbuild.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 # testbuild.sh
 #
-#   Copyright (C) 2016 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2016-2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -47,12 +47,13 @@ unset testfile
 
 function showusage {
     echo ""
-    echo "USAGE: $progname [-w|l] [-c|n] [-s] [-a <appsdir>] [-n <nxdir>] <testlist-file>"
+    echo "USAGE: $progname [-w|l] [-c|u|n] [-s] [-a <appsdir>] [-n <nxdir>] <testlist-file>"
     echo "       $progname -h"
     echo ""
     echo "Where:"
     echo "  -w|l selects Windows (w) or Linux (l).  Default: Linux"
-    echo "  -c|n selects Windows native (n) or Cygwin (c).  Default Cygwin"
+    echo "  -c|u|n selects Windows environment option:  Cygwin (c), Ubuntu under"
+    echo "     Windows 10 (u), or Windows native (n).  Default Cygwin"
     echo "  -s Use C++ unsigned long size_t in new operator. Default unsigned int"
     echo "  -a <appsdir> provides the relative path to the apps/ directory.  Default ../apps"
     echo "  -n <nxdir> provides the relative path to the NxWidgets/ directory.  Default ../NxWidgets"
@@ -78,6 +79,9 @@ while [ ! -z "$1" ]; do
     -c )
     wenv=cygwin
     ;;
+    -u )
+    wenv=ubuntu
+    ;;
     -n )
     wenv=native
     ;;
@@ -165,11 +169,19 @@ function configure {
         if [ "X$wenv" == "Xcygwin" ]; then
           echo "  Select CONFIG_WINDOWS_CYGWIN=y"
           kconfig-tweak --file $nuttx/.config --enable CONFIG_WINDOWS_CYGWIN
+          kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_UBUNTU
           kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_NATIVE
         else
-          echo "  Select CONFIG_WINDOWS_NATIVE=y"
-          kconfig-tweak --file $nuttx/.config --enable CONFIG_WINDOWS_NATIVE
           kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_CYGWIN
+          if [ "X$wenv" == "Xubuntu" ]; then
+            echo "  Select CONFIG_WINDOWS_UBUNTU=y"
+            kconfig-tweak --file $nuttx/.config --enable CONFIG_WINDOWS_UBUNTU
+            kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_NATIVE
+          else
+            echo "  Select CONFIG_WINDOWS_NATIVE=y"
+            kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_UBUNTU
+            kconfig-tweak --file $nuttx/.config --enable CONFIG_WINDOWS_NATIVE
+          fi
         fi
 
         kconfig-tweak --file $nuttx/.config --disable CONFIG_WINDOWS_MSYS