added -F flag (Fallback) to script

start_doth_dns.bash

@@ -59,7 +59,7 @@ exit_dc_err() {
 
 # Func for showing usage string
 usage_string() {
-  printf "\nUsage: %s [-f] [-a <arm|x86>] [-c] [-I <INTERFACE>] [-i <IP ADDRESS>] `
+  printf "\nUsage: %s [-f] [-F] [-a <arm|x86>] [-c] [-I <INTERFACE>] [-i <IP ADDRESS>] `
           `[-n <HOSTNAME>] [-t <TIMEZONE>] [-d <DOMAIN>] [-N] [-R] [-U] [-P] [-D] [-h]\n" "$0" 1>&2;
 }
 
@@ -79,11 +79,14 @@ help() {
 
 # ##########################################################################################
 # Catching flags
-while getopts ":fa:cI:i:n:t:d:NRUPDh" flag; do
+while getopts ":fFa:cI:i:n:t:d:NRUPDh" flag; do
   case ${flag} in
     f) # Set for overwriting existing configs with new ones.
       _FLAG_FRESH='y'
       ;;
+    F) # Set to let the script fallback to next source for configuration variables. Order: `flag -> .env file -> environment -> self gather`
+      _FLAG_FALLBACK='y'
+      ;;
     a) # Set ARCHITECTURE variable with 'ARM' or 'x86' (case insensitive).
       if ! [[ "${OPTARG,,}" == 'arm' ]] && ! [[ "${OPTARG,,}" == 'x86' ]]; then
         printf "No valid argument for '-a'.\n"