diff --git a/board/common/mkimage.sh b/board/common/mkimage.sh
index b20f23578e..3344302697 100755
--- a/board/common/mkimage.sh
+++ b/board/common/mkimage.sh
@@ -1,5 +1,13 @@
 #!/bin/bash -e
 
+# env vars:
+#  THINGOS_LOOP_DEV=/dev/loop0
+#  THINGOS_NAME=thingOS
+#  THINGOS_SHORT_NAME=thingos
+#  THINGOS_PREFIX=thing
+#  THINGOS_VERSION=3.14.15
+
+
 if [ -z "${IMG_DIR}" ] || [ -z "${BOARD}" ]; then
     echo "this script must be invoked from board specific mkimage.sh"
     exit 1
@@ -30,10 +38,13 @@ DISK_SIZE=$((ROOT_START + ROOT_SIZE + GUARD_SIZE))
 COMMON_DIR=$(cd ${IMG_DIR}/../../../board/common; pwd)
 OS_NAME=$(source ${COMMON_DIR}/overlay/etc/version && echo ${OS_SHORT_NAME})
 
+# "-f", unless a /dev/loopX is specified
+LOOP_DEV=${THINGOS_LOOP_DEV:--f}
+
 # boot filesystem
 msg "creating boot loop device"
 dd if=/dev/zero of=${BOOT_IMG} bs=1M count=${BOOT_SIZE}
-loop_dev=$(losetup -f --show ${BOOT_IMG})
+loop_dev=$(losetup --show ${LOOP_DEV} ${BOOT_IMG})
 
 msg "creating boot filesystem"
 mkfs.vfat -F16 ${loop_dev}
@@ -56,7 +67,7 @@ sync
 # root filesystem
 msg "creating root loop device"
 dd if=/dev/zero of=${ROOT_IMG} bs=1M count=${ROOT_SIZE}
-loop_dev=$(losetup -f --show ${ROOT_IMG})
+loop_dev=$(losetup --show ${LOOP_DEV} ${ROOT_IMG})
 
 msg "creating root filesystem"
 mkfs.ext4 ${loop_dev}
@@ -117,7 +128,7 @@ if [ -n "${UBOOT_BIN}" ] && [ -n "${UBOOT_SEEK}" ]; then
     msg "copying u-boot image"
     dd conv=notrunc if=${UBOOT_BIN} of=${DISK_IMG} bs=512 seek=${UBOOT_SEEK}
 fi
-loop_dev=$(losetup -f --show ${DISK_IMG})
+loop_dev=$(losetup --show ${LOOP_DEV} ${DISK_IMG})
 
 msg "partitioning disk"
 set +e
@@ -152,7 +163,7 @@ msg "destroying disk loop device (${loop_dev})"
 losetup -d ${loop_dev}
 
 msg "creating boot loop device"
-loop_dev=$(losetup -f --show -o $((${boot_offs} * 512)) ${DISK_IMG})
+loop_dev=$(losetup --show -o $((${boot_offs} * 512)) ${LOOP_DEV} ${DISK_IMG})
 
 msg "copying boot image"
 dd if=${BOOT_IMG} of=${loop_dev}
@@ -162,7 +173,7 @@ msg "destroying boot loop device (${loop_dev})"
 losetup -d ${loop_dev}
 
 msg "creating root loop device"
-loop_dev=$(losetup -f --show -o $((${root_offs} * 512)) ${DISK_IMG})
+loop_dev=$(losetup --show -o $((${root_offs} * 512)) ${LOOP_DEV} ${DISK_IMG})
 sync
 
 msg "copying root image"