make sure that $1 is a real user

create-image.sh

@@ -15,6 +15,13 @@ for COMMAND in "${COMMANDS_TO_CHECK[@]}"; do
     fi
 done
 
+if [[ -n "$1" ]]; then
+    GUSER="^$1"
+    if ! grep $GUSER /etc/shadow > /dev/null; then
+        >&2 echo "$0: ERROR: unable to find user '$1'"
+    fi
+fi
+
 function create_new_image {
     UBOOT_MAX_SIZE='32'
     IMAGE_SIZE=$(( $(stat -c '%s' "${IMAGE_NAME}") / 1024 / 1024 ))