diff --git a/src/moby/output.go b/src/moby/output.go
index c8c859242..5ca663cf7 100644
--- a/src/moby/output.go
+++ b/src/moby/output.go
@@ -13,19 +13,33 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
-const (
-	isoBios    = "linuxkit/mkimage-iso-bios:9a51dc64a461f1cc50ba05f30a38f73f5227ac03"
-	isoEfi     = "linuxkit/mkimage-iso-efi:343cf1a8ac0aba7d8a1f13b7f45fa0b57ab897dc"
-	rawBios    = "linuxkit/mkimage-raw-bios:d90713b2dd610cf9a0f5f9d9095f8bf86f40d5c6"
-	rawEfi     = "linuxkit/mkimage-raw-efi:8938ffb6014543e557b624a40cce1714f30ce4b6"
-	gcp        = "linuxkit/mkimage-gcp:e6cdcf859ab06134c0c37a64ed5f886ec8dae1a1"
-	vhd        = "linuxkit/mkimage-vhd:3820219e5c350fe8ab2ec6a217272ae82f4b9242"
-	vmdk       = "linuxkit/mkimage-vmdk:cee81a3ed9c44ae446ef7ebff8c42c1e77b3e1b5"
-	dynamicvhd = "linuxkit/mkimage-dynamic-vhd:743ac9959fe6d3912ebd78b4fd490b117c53f1a6"
-	rpi3       = "linuxkit/mkimage-rpi3:0f23c4f37cdca99281ca33ac6188e1942fa7a2b8"
-	qcow2Efi   = "linuxkit/mkimage-qcow2-efi:787b54906e14a56b9f1da35dcc8e46bd58435285"
+var (
+	outputImages = map[string]string{
+		"iso-bios":    "linuxkit/mkimage-iso-bios:9a51dc64a461f1cc50ba05f30a38f73f5227ac03",
+		"iso-efi":     "linuxkit/mkimage-iso-efi:343cf1a8ac0aba7d8a1f13b7f45fa0b57ab897dc",
+		"raw-bios":    "linuxkit/mkimage-raw-bios:d90713b2dd610cf9a0f5f9d9095f8bf86f40d5c6",
+		"raw-efi":     "linuxkit/mkimage-raw-efi:8938ffb6014543e557b624a40cce1714f30ce4b6",
+		"gcp":         "linuxkit/mkimage-gcp:e6cdcf859ab06134c0c37a64ed5f886ec8dae1a1",
+		"qcow2-efi":   "linuxkit/mkimage-qcow2-efi:787b54906e14a56b9f1da35dcc8e46bd58435285",
+		"vhd":         "linuxkit/mkimage-vhd:3820219e5c350fe8ab2ec6a217272ae82f4b9242",
+		"dynamic-vhd": "linuxkit/mkimage-dynamic-vhd:743ac9959fe6d3912ebd78b4fd490b117c53f1a6",
+		"vmdk":        "linuxkit/mkimage-vmdk:cee81a3ed9c44ae446ef7ebff8c42c1e77b3e1b5",
+		"rpi3":        "linuxkit/mkimage-rpi3:0f23c4f37cdca99281ca33ac6188e1942fa7a2b8",
+	}
 )
 
+// UpdateOutputImages overwrite the docker images used to build the outputs
+// 'update' is a map where the key is the output format and the value is a LinuxKit 'mkimage' image.
+func UpdateOutputImages(update map[string]string) error {
+	for k, img := range update {
+		if _, ok := outputImages[k]; !ok {
+			return fmt.Errorf("Image format %s is not known", k)
+		}
+		outputImages[k] = img
+	}
+	return nil
+}
+
 var outFuns = map[string]func(string, io.Reader, int) error{
 	"kernel+initrd": func(base string, image io.Reader, size int) error {
 		kernel, initrd, cmdline, ucode, err := tarToInitrd(image)
@@ -49,14 +63,14 @@ var outFuns = map[string]func(string, io.Reader, int) error{
 		return nil
 	},
 	"iso-bios": func(base string, image io.Reader, size int) error {
-		err := outputIso(isoBios, base+".iso", image)
+		err := outputIso(outputImages["iso-bios"], base+".iso", image)
 		if err != nil {
 			return fmt.Errorf("Error writing iso-bios output: %v", err)
 		}
 		return nil
 	},
 	"iso-efi": func(base string, image io.Reader, size int) error {
-		err := outputIso(isoEfi, base+"-efi.iso", image)
+		err := outputIso(outputImages["iso-efi"], base+"-efi.iso", image)
 		if err != nil {
 			return fmt.Errorf("Error writing iso-efi output: %v", err)
 		}
@@ -68,7 +82,7 @@ var outFuns = map[string]func(string, io.Reader, int) error{
 			return fmt.Errorf("Error converting to initrd: %v", err)
 		}
 		// TODO: Handle ucode
-		err = outputImg(rawBios, base+"-bios.img", kernel, initrd, cmdline)
+		err = outputImg(outputImages["raw-bios"], base+"-bios.img", kernel, initrd, cmdline)
 		if err != nil {
 			return fmt.Errorf("Error writing raw-bios output: %v", err)
 		}
@@ -79,7 +93,7 @@ var outFuns = map[string]func(string, io.Reader, int) error{
 		if err != nil {
 			return fmt.Errorf("Error converting to initrd: %v", err)
 		}
-		err = outputImg(rawEfi, base+"-efi.img", kernel, initrd, cmdline)
+		err = outputImg(outputImages["raw-efi"], base+"-efi.img", kernel, initrd, cmdline)
 		if err != nil {
 			return fmt.Errorf("Error writing raw-efi output: %v", err)
 		}
@@ -103,7 +117,7 @@ var outFuns = map[string]func(string, io.Reader, int) error{
 		if err != nil {
 			return fmt.Errorf("Error converting to initrd: %v", err)
 		}
-		err = outputImg(gcp, base+".img.tar.gz", kernel, initrd, cmdline)
+		err = outputImg(outputImages["gcp"], base+".img.tar.gz", kernel, initrd, cmdline)
 		if err != nil {
 			return fmt.Errorf("Error writing gcp output: %v", err)
 		}
@@ -114,7 +128,7 @@ var outFuns = map[string]func(string, io.Reader, int) error{
 		if err != nil {
 			return fmt.Errorf("Error converting to initrd: %v", err)
 		}
-		err = outputImg(qcow2Efi, base+"-efi.qcow2", kernel, initrd, cmdline)
+		err = outputImg(outputImages["qcow2-efi"], base+"-efi.qcow2", kernel, initrd, cmdline)
 		if err != nil {
 			return fmt.Errorf("Error writing qcow2 EFI output: %v", err)
 		}
@@ -139,7 +153,7 @@ var outFuns = map[string]func(string, io.Reader, int) error{
 		if err != nil {
 			return fmt.Errorf("Error converting to initrd: %v", err)
 		}
-		err = outputImg(vhd, base+".vhd", kernel, initrd, cmdline)
+		err = outputImg(outputImages["vhd"], base+".vhd", kernel, initrd, cmdline)
 		if err != nil {
 			return fmt.Errorf("Error writing vhd output: %v", err)
 		}
@@ -150,7 +164,7 @@ var outFuns = map[string]func(string, io.Reader, int) error{
 		if err != nil {
 			return fmt.Errorf("Error converting to initrd: %v", err)
 		}
-		err = outputImg(dynamicvhd, base+".vhd", kernel, initrd, cmdline)
+		err = outputImg(outputImages["dynamic-vhd"], base+".vhd", kernel, initrd, cmdline)
 		if err != nil {
 			return fmt.Errorf("Error writing vhd output: %v", err)
 		}
@@ -161,7 +175,7 @@ var outFuns = map[string]func(string, io.Reader, int) error{
 		if err != nil {
 			return fmt.Errorf("Error converting to initrd: %v", err)
 		}
-		err = outputImg(vmdk, base+".vmdk", kernel, initrd, cmdline)
+		err = outputImg(outputImages["vmdk"], base+".vmdk", kernel, initrd, cmdline)
 		if err != nil {
 			return fmt.Errorf("Error writing vmdk output: %v", err)
 		}
@@ -171,7 +185,7 @@ var outFuns = map[string]func(string, io.Reader, int) error{
 		if runtime.GOARCH != "arm64" {
 			return fmt.Errorf("Raspberry Pi output currently only supported on arm64")
 		}
-		err := outputRPi3(rpi3, base+".tar", image)
+		err := outputRPi3(outputImages["rpi3"], base+".tar", image)
 		if err != nil {
 			return fmt.Errorf("Error writing rpi3 output: %v", err)
 		}