diff --git a/Dockerfile b/Dockerfile
index a023345..99bdaa1 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM ubuntu
+FROM ubuntu:14.04
 MAINTAINER Christian Lück <christian@lueck.tv>
 
 RUN DEBIAN_FRONTEND=noninteractive apt-get update && apt-get install -y \
diff --git a/README.md b/README.md
index a884f7c..f7d2c62 100644
--- a/README.md
+++ b/README.md
@@ -164,6 +164,18 @@ For more information check out the [official documentation](https://github.com/g
 -e SELF_URL_PATH=https://example.org/ttrss
 ```
 
+### Additional configuration
+
+In addition to the environement variables above, it is possible to override any value in the `config.php`
+by using another environment variable. Prefix the config value you want to override with `CONFIG_`
+and it will replace the default value on container creation.
+
+For example, to add the `auth_external` plugin, set the following variable:
+
+```
+-e CONFIG_PLUGINS='auth_internal, note, auth_external'
+```
+
 ### Testing ttrss in foreground
 
 For testing purposes it's recommended to initially start this container in foreground.
diff --git a/configure-db.php b/configure-db.php
index 8f9b1e3..6582193 100644
--- a/configure-db.php
+++ b/configure-db.php
@@ -63,7 +63,7 @@
     $super['DB_NAME'] = null;
     $super['DB_USER'] = env('DB_ENV_USER', 'docker');
     $super['DB_PASS'] = env('DB_ENV_PASS', $super['DB_USER']);
-    
+
     $pdo = dbconnect($super);
 
     if ($super['DB_TYPE'] === 'mysql') {
@@ -75,7 +75,7 @@
     }
 
     unset($pdo);
-    
+
     if (dbcheck($config)) {
         echo 'Database login created and confirmed' . PHP_EOL;
     } else {
@@ -100,6 +100,15 @@
     unset($pdo);
 }
 
+$config_prefix = 'CONFIG_';
+foreach ($_SERVER as $name => $value) {
+    if (strpos($name, $config_prefix) === 0) {
+        $name = substr($name, strlen($config_prefix));
+        echo 'Getting config from env: ' . $name . PHP_EOL;
+        $config[$name] = $value;
+    }
+}
+
 $contents = file_get_contents($confpath);
 foreach ($config as $name => $value) {
     $contents = preg_replace('/(define\s*\(\'' . $name . '\',\s*)(.*)(\);)/', '$1"' . $value . '"$3', $contents);
@@ -109,11 +118,11 @@
 function env($name, $default = null)
 {
     $v = getenv($name) ?: $default;
-    
+
     if ($v === null) {
         error('The env ' . $name . ' does not exist');
     }
-    
+
     return $v;
 }