diff --git a/UPGRADE.md b/UPGRADE.md
index ebcdc47b..70826680 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -1,3 +1,40 @@
+# Upgrade from 4.x to 5.x
+
+1. Servers to Hosts
+   
+   * Refactor `server($name, $hostname)` to `host($hostname)`
+   * Refactor `localServer($name)` to `localhost()`
+   * Rename `serverList($file)` to `inventory($file)`
+  
+2. Configuration options
+
+   * Rename `{{server.name}}` to `{{hostname}}`
+   
+3. DotArray syntax
+
+   In v5 access to nested arrays in config via dot notation was removed. 
+   If you was using it, consider to move to plain config options.
+   
+   Refactor this:
+   
+   ```php
+   set('a', ['b' => 1]);
+   
+   // ...
+   
+   get('a.b');
+   ```
+   
+   To:
+   
+   ```php
+   set('a_b', 1);
+   
+   // ...
+   
+   get('a_b');
+   ```
+
 # Upgrade from 3.x to 4.x
 
 1. Namespace for functions
diff --git a/src/Host/FileLoader.php b/src/Host/FileLoader.php
index ea84e90c..6adcc317 100644
--- a/src/Host/FileLoader.php
+++ b/src/Host/FileLoader.php
@@ -22,6 +22,10 @@ class FileLoader
      */
     public function load($file)
     {
+        if (!file_exists($file) || !is_readable($file)) {
+            throw new ConfigurationException("File `$file` doesn't exists or doesn't readable.");
+        }
+
         $data = Yaml::parse(file_get_contents($file));
 
         if (!is_array($data)) {
diff --git a/src/Utility/Proxy.php b/src/Utility/Proxy.php
new file mode 100644
index 00000000..b0b11535
--- /dev/null
+++ b/src/Utility/Proxy.php
@@ -0,0 +1,26 @@
+<?php
+/* (c) Anton Medvedev <anton@medv.io>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Deployer\Utility;
+
+class Proxy
+{
+    private $objects;
+
+    public function __construct(array $objects)
+    {
+        $this->objects = $objects;
+    }
+
+    public function __call($name, $arguments)
+    {
+        foreach ($this->objects as $object) {
+            $object->$name(...$arguments);
+        }
+        return $this;
+    }
+}
\ No newline at end of file
diff --git a/src/functions.php b/src/functions.php
index 508c7376..87567937 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -13,6 +13,7 @@ use Deployer\Task\Context;
 use Deployer\Task\GroupTask;
 use Deployer\Task\Task as T;
 use Deployer\Type\Result;
+use Deployer\Utility\Proxy;
 use Monolog\Logger;
 use Symfony\Component\Console\Input\InputArgument;
 use Symfony\Component\Console\Input\InputInterface;
@@ -30,12 +31,22 @@ use Symfony\Component\Finder\Finder;
 // execution stage. They are acts like two different function, but have same name. Example of such function
 // is set() func. This function determine in which stage it was called by Context::get() method.
 
-function host($hostname, $alias = null)
+function host(...$hostnames)
 {
     $deployer = Deployer::get();
-    $host = new Host($hostname);
-    $deployer->hosts->set($alias ?: $hostname, $host);
-    return $host;
+
+    if (count($hostnames) === 1) {
+        $host = new Host($hostnames[0]);
+        $deployer->hosts->set($hostnames[0], $host);
+        return $host;
+    } else {
+        $hosts = array_map(function ($hostname) use ($deployer) {
+            $host = new Host($hostname);
+            $deployer->hosts->set($hostname, $host);
+            return $host;
+        }, $hostnames);
+        return new Proxy($hosts);
+    }
 }
 
 function localhost($alias = 'localhost')
@@ -51,7 +62,7 @@ function localhost($alias = 'localhost')
  *
  * @param string $file
  */
-function hostsList($file)
+function inventory($file)
 {
     $deployer = Deployer::get();
     $fileLoader = new FileLoader();