diff --git a/ipynbsrv/core/models.py b/ipynbsrv/core/models.py
index cfb7193..7267a2e 100644
--- a/ipynbsrv/core/models.py
+++ b/ipynbsrv/core/models.py
@@ -544,6 +544,10 @@ def clean(self):
                 raise ValidationError({
                     'server': 'A clone can only be created on the same node as it\'s parent.'
                 })
+            if self.image and self.image.is_internal:
+                raise ValidationError({
+                    'image': 'Internal images cannot be used to create containers from.'
+                })
         super(Container, self).clean()
 
     def clone(self, name, description=None):
diff --git a/ipynbsrv/core/signals/container_images.py b/ipynbsrv/core/signals/container_images.py
index 16dcc8b..9a488fe 100644
--- a/ipynbsrv/core/signals/container_images.py
+++ b/ipynbsrv/core/signals/container_images.py
@@ -22,20 +22,6 @@ def create_image_on_server(sender, container, image, **kwargs):
             raise ex
 
 
-@receiver(container_deleted)
-def delete_internal_image_if_latest(sender, container, **kwargs):
-    """
-    Delete the internal only image if this is the last container using it.
-    """
-    if container is not None:
-        try:
-            if container.is_image_based() and container.image.is_internal and not container.has_clones():
-                if not Container.objects.filter(image=container.image).exists():
-                    container.image.delete()
-        except ContainerImage.DoesNotExist:
-            pass
-
-
 @receiver(container_image_deleted)
 def delete_related_notifications(sender, image, **kwargs):
     """
@@ -59,9 +45,10 @@ def delete_on_server(sender, image, **kwargs):
                     backend.delete_container_image(image.backend_pk)
                 except ContainerImageNotFoundError:
                     pass  # already removed
-                except ContainerBackendError as ex:
+                except ContainerBackendError:
                     # XXX: restore?
-                    raise ex
+                    # raise ex
+                    pass
 
 
 @receiver(post_delete, sender=ContainerImage)
diff --git a/ipynbsrv/core/signals/containers.py b/ipynbsrv/core/signals/containers.py
index 75689d6..5341fc5 100644
--- a/ipynbsrv/core/signals/containers.py
+++ b/ipynbsrv/core/signals/containers.py
@@ -72,9 +72,10 @@ def create_on_server(sender, container, **kwargs):
         if container.is_image_based():
             cmd = container.image.command
             image = container.image.backend_pk
-        elif container.is_clone() and container.clone_of.is_image_based():
+        elif container.is_clone():
             clone_of = container.clone_of.backend_pk
-            cmd = container.clone_of.image.command
+            if container.clone_of.is_image_based():
+                cmd = container.clone_of.image.command
 
         result = None
         try:
@@ -145,6 +146,10 @@ def delete_on_server(sender, container, **kwargs):
     if container is not None:
         try:
             container.server.get_container_backend().delete_container(container.backend_pk)
+            # cleanup internal images
+            # if container.is_image_based() and container.image.is_internal and not container.has_clones():
+            #     if not Container.objects.filter(image=container.image).exists():
+            #         container.image.delete()
         except ContainerNotFoundError as ex:
             pass  # already deleted
         except ContainerBackendError as ex:
diff --git a/lib/confs/nginx/ipynbsrv.conf b/lib/confs/nginx/ipynbsrv.conf
index 45e1616..1379430 100644
--- a/lib/confs/nginx/ipynbsrv.conf
+++ b/lib/confs/nginx/ipynbsrv.conf
@@ -16,8 +16,8 @@ server {
 
     location / {
         include      /usr/local/openresty/nginx/conf/uwsgi_params;
-        uwsgi_read_timeout  300s;
-        uwsgi_send_timeout  300s;
+        uwsgi_read_timeout  600s;
+        uwsgi_send_timeout  600s;
         uwsgi_param  REQUEST_URI  $uri$args;
         uwsgi_pass   unix:/var/run/ipynbsrv/ipynbsrv.sock;
     }
diff --git a/lib/confs/uwsgi/ipynbsrv.ini b/lib/confs/uwsgi/ipynbsrv.ini
index fbed1e0..0161a6a 100644
--- a/lib/confs/uwsgi/ipynbsrv.ini
+++ b/lib/confs/uwsgi/ipynbsrv.ini
@@ -8,8 +8,8 @@ master=True
 vacuum=True
 max-requests=5000
 processes=5
-harakiri=300
-chmod-socket = 660
-chown-socket = www-data:www-data
+harakiri=600
+chmod-socket=660
+chown-socket=www-data:www-data
 pidfile=/var/run/ipynbsrv/ipynbsrv.pid
 uwsgi-socket=/var/run/ipynbsrv/ipynbsrv.sock