Docker: Add IPAM_CONFIG_FILE config.php env

functions/classes/class.Config.php

@@ -13,12 +13,27 @@ class Config {
      */
     private static $config = null;
 
+    /**
+     * Return path of config.php
+     *
+     * @return string
+     */
+    private static function config_file_path() {
+        // IPAM_CONFIG_FILE, alternative config.php location
+        $alt_file = getenv('IPAM_CONFIG_FILE');
+        if (is_string($alt_file) && preg_match('/\.php$/', $alt_file) && is_readable($alt_file)) {
+            return $alt_file;
+        }
+
+        return dirname(__FILE__) . "/../../config.php";
+    }
+
     /**
      * Read config.php info self::$config
      * @return void
      */
     private static function read_config() {
-        require( dirname(__FILE__)."/../../config.php" );
+        require(self::config_file_path());
         self::$config = (object) get_defined_vars();
     }