diff --git a/cinder/tests/unit/volume/drivers/test_nfs.py b/cinder/tests/unit/volume/drivers/test_nfs.py
index ab9b46317ab..5208e38c95f 100644
--- a/cinder/tests/unit/volume/drivers/test_nfs.py
+++ b/cinder/tests/unit/volume/drivers/test_nfs.py
@@ -1066,17 +1066,19 @@ class NfsDriverTestCase(test.TestCase):
         if file_format:
             volume.admin_metadata = {'format': file_format}
         mock_get.return_value = volume
-        path = 'path'
+        local_vol_dir = 'dir'
         newSize = volume['size'] + 1
 
         with mock.patch.object(image_utils, 'resize_image') as resize:
-            with mock.patch.object(drv, 'local_path', return_value=path):
+            with mock.patch.object(drv, '_local_volume_dir',
+                                   return_value=local_vol_dir):
                 with mock.patch.object(drv, '_is_share_eligible',
                                        return_value=True):
                     with mock.patch.object(drv, '_is_file_size_equal',
                                            return_value=True):
                         drv.extend_volume(volume, newSize)
 
+                        path = os.path.join(local_vol_dir, volume.name)
                         resize.assert_called_once_with(path, newSize,
                                                        run_as_root=True,
                                                        file_format=file_format)
diff --git a/cinder/tests/unit/volume/drivers/test_remotefs.py b/cinder/tests/unit/volume/drivers/test_remotefs.py
index a8c69398ccb..1902920d57c 100644
--- a/cinder/tests/unit/volume/drivers/test_remotefs.py
+++ b/cinder/tests/unit/volume/drivers/test_remotefs.py
@@ -363,11 +363,13 @@ class RemoteFsSnapDriverTestCase(test.TestCase):
                 self.context, connection_info=conn_info)
             snapshot.volume.volume_attachment.objects.append(attachment)
             mock_save = self.mock_object(attachment, 'save')
+            mock_vol_save = self.mock_object(snapshot.volume, 'save')
 
             # After the snapshot the connection info should change the name of
             # the file
             expected = copy.deepcopy(attachment.connection_info)
             expected['name'] = snapshot.volume.name + '.' + snapshot.id
+            expected['format'] = 'qcow2'
         else:
             expected_method_called = '_do_create_snapshot'
 
@@ -386,6 +388,8 @@ class RemoteFsSnapDriverTestCase(test.TestCase):
 
         if volume_in_use:
             mock_save.assert_called_once()
+            # We should have updated the volume format after the snapshot
+            mock_vol_save.assert_called_once()
             changed_fields = attachment.cinder_obj_get_changes()
             self.assertEqual(expected, changed_fields['connection_info'])
 
diff --git a/cinder/volume/drivers/nfs.py b/cinder/volume/drivers/nfs.py
index 95c33e0b756..a4151c3408c 100644
--- a/cinder/volume/drivers/nfs.py
+++ b/cinder/volume/drivers/nfs.py
@@ -392,18 +392,22 @@ class NfsDriver(remotefs.RemoteFSSnapDriverDistributed):
             raise exception.ExtendVolumeError(reason='Insufficient space to'
                                               ' extend volume %s to %sG'
                                               % (volume.id, new_size))
-        path = self.local_path(volume)
+        # Use the active image file because this volume might have snapshot(s).
+        active_file = self.get_active_image_from_info(volume)
+        active_file_path = os.path.join(self._local_volume_dir(volume),
+                                        active_file)
         LOG.info('Resizing file to %sG...', new_size)
         file_format = None
         admin_metadata = objects.Volume.get_by_id(
             context.get_admin_context(), volume.id).admin_metadata
+
         if admin_metadata and 'format' in admin_metadata:
             file_format = admin_metadata['format']
-        image_utils.resize_image(path, new_size,
+        image_utils.resize_image(active_file_path, new_size,
                                  run_as_root=self._execute_as_root,
                                  file_format=file_format)
         if file_format == 'qcow2' and not self._is_file_size_equal(
-                path, new_size):
+                active_file_path, new_size):
             raise exception.ExtendVolumeError(
                 reason='Resizing image file failed.')
 
diff --git a/cinder/volume/drivers/remotefs.py b/cinder/volume/drivers/remotefs.py
index 40d14b8faac..64bbeb2259a 100644
--- a/cinder/volume/drivers/remotefs.py
+++ b/cinder/volume/drivers/remotefs.py
@@ -1720,9 +1720,18 @@ class RemoteFSSnapDriverBase(RemoteFSDriver):
             self._create_snapshot_online(snapshot,
                                          backing_filename,
                                          new_snap_path)
+            # Update the format for the volume and the connection_info. The
+            # connection_info needs to reflect the current volume format in
+            # order for Nova to create the disk device correctly whenever the
+            # instance is stopped/started or rebooted.
+            new_format = 'qcow2'
+            snapshot.volume.admin_metadata['format'] = new_format
+            with snapshot.volume.obj_as_admin():
+                snapshot.volume.save()
             # Update reference in the only attachment (no multi-attach support)
             attachment = snapshot.volume.volume_attachment[0]
             attachment.connection_info['name'] = active
+            attachment.connection_info['format'] = new_format
             # Let OVO know it has been updated
             attachment.connection_info = attachment.connection_info
             attachment.save()
diff --git a/releasenotes/notes/attach-format-after-snapshot-9a1857456706aa72.yaml b/releasenotes/notes/attach-format-after-snapshot-9a1857456706aa72.yaml
new file mode 100644
index 00000000000..4b0e6d80930
--- /dev/null
+++ b/releasenotes/notes/attach-format-after-snapshot-9a1857456706aa72.yaml
@@ -0,0 +1,7 @@
+fixes:
+  - |
+    NFS driver `bug #1989514`_: When creating a snapshot of an attached volume,
+    the volume attachment format was not updated in its connection_info and
+    could have resulted in an unbootable guest. This has been fixed.
+
+    .. _bug #1989514: https://bugs.launchpad.net/cinder/+bug/1989514