diff --git a/box.py b/box.py
index f336f4a..6e59632 100755
--- a/box.py
+++ b/box.py
@@ -7,8 +7,23 @@ import tempfile
 
 
 class VMCreate:
+    """
+    Create vbox VM of Ubuntu server from cloud image with the following steps:
+        - grab the image, unless it exists in XDG_CACHE_HOME
+        - convert it to raw, than to VDI, remove raw
+        - resize it to the right size
+        - create cloud ISO image with some basic bootstrap
+        - create and register VM definition
+        - tweak its params
+        - move disk image to the Machine directory
+        - attach disk and iso images to it
+        - run and wait for initial bootstrap, than acpishutdown
+        - detach iso image and remove it
+    """
     CLOUD_IMAGE = "ci.iso"
     CLOUD_INIT_FINISHED_CMD = "test /var/lib/cloud/instance/boot-finished"
+    CACHE_DIR = os.environ.get('XDG_CACHE_HOME',
+                               os.path.expanduser('~/.cache'))
 
     def __init__(self, args):
         self.vm_name = args.name
@@ -16,6 +31,7 @@ class VMCreate:
         self.memory = args.memory
         self.disk_size = args.disk_size
         self.ubuntu_version = args.version
+        self._img = f"ubuntu-{self.ubuntu_version}-server-cloudimg-amd64.img"
         self._temp_path = None
         self._disk_img = self.vm_name + '.vdi'
         self._tmp = None
@@ -31,14 +47,51 @@ class VMCreate:
     def _prepare_temp(self):
         self._tmp = tempfile.mkdtemp()
 
+    def _checksum(self):
+        expected_sum = None
+        fname = 'SHA256SUMS'
+        url = "https://cloud-images.ubuntu.com/releases/"
+        url += f"{self.ubuntu_version}/release/{fname}"
+        # TODO: make the verbosity switch be dependent from verbosity of the
+        # script.
+        subprocess.call(['wget', url, '-q', '-O',
+                         os.path.join(self._tmp, fname)])
+
+        with open(os.path.join(self._tmp, fname)) as fobj:
+            for line in fobj.readlines():
+                if self._img in line:
+                    expected_sum = line.split(' ')[0]
+                    break
+
+        if not expected_sum:
+            raise AttributeError('Cannot find provided cloud image')
+
+        if os.path.exists(os.path.join(self.CACHE_DIR, self._img)):
+            cmd = 'sha256sum ' + os.path.join(self.CACHE_DIR, self._img)
+            calulated_sum = subprocess.getoutput(cmd).split(' ')[0]
+            return calulated_sum == expected_sum
+
+        return False
+
     def _download_image(self):
+        if self._checksum():
+            print(f'Image already downloaded: {self._img}')
+            return
+
         url = "https://cloud-images.ubuntu.com/releases/"
         url += f"{self.ubuntu_version}/release/"
         img = f"ubuntu-{self.ubuntu_version}-server-cloudimg-amd64.img"
         url += img
-        print(url)
+        print(f'Downloading image {self._img}')
+        subprocess.call(['wget', '-q', url, '-O',
+                         os.path.join(self.CACHE_DIR, self._img)])
 
-        subprocess.call(['wget', url, '-O', os.path.join(self._tmp, img)])
+        if not self._checksum():
+            # TODO: make some retry mechanism?
+            raise AttributeError('Checksum for downloaded image differ from'
+                                 ' expected')
+        else:
+            print(f'downloaded image {self._img}')
 
     def _cleanup(self):
         subprocess.call(['rm', '-fr', self._tmp])
@@ -71,9 +124,7 @@ def main():
 
     args = parser.parse_args()
 
-    return args.func(args)
     try:
-        # __import__('ipdb').set_trace()
         return args.func(args)
     except AttributeError:
         parser.print_help()