diff --git a/usr/bin/spoc-container b/usr/bin/spoc-container
index 1a21784..4a8bff2 100644
--- a/usr/bin/spoc-container
+++ b/usr/bin/spoc-container
@@ -66,33 +66,33 @@ def modify_container(container, depends, mounts, envs, uid, gid, cmd, cwd, ready
             setattr(container, member, value)
 
 def create(container_name, image_name, depends, mounts, env, uid, gid, cmd, cwd, ready, halt, autostart):
-    container = Image(image_name, True).get_container(container_name)
+    container = Image(image_name).get_container(container_name)
     modify_container(container, depends, mounts, env, uid, gid, cmd, cwd, ready, halt, autostart)
     container.create()
 
 def modify(container_name, depends, mounts, env, uid, gid, cmd, cwd, ready, halt, autostart):
-    container = Container(container_name, True)
+    container = Container(container_name)
     modify_container(container, depends, mounts, env, uid, gid, cmd, cwd, ready, halt, autostart)
     container.create()
 
 def destroy(container_name):
-    container = Container(container_name)
+    container = Container(container_name, False)
     container.destroy()
 
 def start(container_name):
-    container = Container(container_name, True)
+    container = Container(container_name)
     container.start()
 
 def stop(container_name):
-    container = Container(container_name, True)
+    container = Container(container_name)
     container.stop()
 
 def status(container_name):
-    container = Container(container_name, True)
+    container = Container(container_name)
     print(container.get_state().value)
 
 def execute(container_name, command):
-    container = Container(container_name, True)
+    container = Container(container_name)
     container.execute(command)
 
 parser = argparse.ArgumentParser(description='SPOC container manager')
diff --git a/usr/bin/spoc-hook b/usr/bin/spoc-hook
index 420d912..084bc91 100644
--- a/usr/bin/spoc-hook
+++ b/usr/bin/spoc-hook
@@ -7,7 +7,7 @@ from spoc.container import Container
 
 if __name__ == '__main__':
     hook_type = os.environ['LXC_HOOK_TYPE']
-    container = Container(os.environ['LXC_NAME'], True)
+    container = Container(os.environ['LXC_NAME'])
     if hook_type == 'pre-start':
         container.clean_ephemeral_layer()
         container.mount_rootfs()
diff --git a/usr/bin/spoc-image b/usr/bin/spoc-image
index acbb262..142186e 100644
--- a/usr/bin/spoc-image
+++ b/usr/bin/spoc-image
@@ -38,13 +38,13 @@ def download(image_name):
     raise NotImplementedException() # TODO
 
 def delete(image_name):
-    image = Image(image_name)
+    image = Image(image_name, False)
     image.delete()
 
 def build(filename, force, do_publish):
     # Check if a build is needed and attempt to build the image from image file
     image_name = get_image_name(filename)
-    image = Image(image_name)
+    image = Image(image_name, False)
     if force or image.name not in repo_local.get_images():
         image.delete()
         print(f'Building image {image_name} from file {filename}')
@@ -59,7 +59,7 @@ def build(filename, force, do_publish):
 
 def publish(image_name, force):
     # Check if publishing is needed and attempt to publish the image
-    image = Image(image_name, True)
+    image = Image(image_name)
     if force or image.name not in repo_publish.get_images():
         image.unpublish()
         print(f'Publishing image {image_name}')
@@ -69,7 +69,7 @@ def publish(image_name, force):
         print(f'Image {image_name} already published, skipping publish task')
 
 def unpublish(image_name):
-    image = Image(image_name)
+    image = Image(image_name, False)
     image.unpublish()
 
 def extract(image_name, source, destination):
diff --git a/usr/lib/python3.8/spoc/container.py b/usr/lib/python3.8/spoc/container.py
index cfa6f24..1fc5f3c 100644
--- a/usr/lib/python3.8/spoc/container.py
+++ b/usr/lib/python3.8/spoc/container.py
@@ -21,10 +21,10 @@ STATE_FREEZING = 'FREEZING'
 STATE_FROZEN = 'FROZEN'
 STATE_THAWED = 'THAWED'
 
-DEFINITION_MEMBERS = ('build', 'depends', 'layers', 'mounts', 'env', 'uid', 'gid', 'cmd', 'cwd', 'ready', 'halt', 'autostart')
+DEFINITION_MEMBERS = {'build', 'depends', 'layers', 'mounts', 'env', 'uid', 'gid', 'cmd', 'cwd', 'ready', 'halt', 'autostart'}
 
 class Container:
-    def __init__(self, name, load_from_repo=False):
+    def __init__(self, name, load_from_repo=True):
         self.name = name
         self.build = False
         self.depends = []
@@ -48,9 +48,8 @@ class Container:
             self.set_definition(repo_local.get_container(name))
 
     def set_definition(self, definition):
-        for key in DEFINITION_MEMBERS:
-            if key in definition:
-                setattr(self, key, definition[key])
+        for key in DEFINITION_MEMBERS.intersection(definition):
+            setattr(self, key, definition[key])
 
     def get_definition(self):
         definition = {}
diff --git a/usr/lib/python3.8/spoc/image.py b/usr/lib/python3.8/spoc/image.py
index 55898e0..7157052 100644
--- a/usr/lib/python3.8/spoc/image.py
+++ b/usr/lib/python3.8/spoc/image.py
@@ -12,10 +12,10 @@ from .container import Container
 from .imagebuilder import ImageBuilder
 from .paths import LAYERS_DIR, PUB_LAYERS_DIR
 
-DEFINITION_MEMBERS = ('parent', 'env', 'uid', 'gid', 'cmd', 'cwd', 'ready', 'halt', 'size', 'dlsize', 'hash')
+DEFINITION_MEMBERS = {'parent', 'env', 'uid', 'gid', 'cmd', 'cwd', 'ready', 'halt', 'size', 'dlsize', 'hash'}
 
 class Image:
-    def __init__(self, name, load_from_repo=False):
+    def __init__(self, name, load_from_repo=True):
         self.name = name
         self.layer_path = os.path.join(LAYERS_DIR, name)
         self.archive_path = os.path.join(PUB_LAYERS_DIR, f'{name}.tar.xz')
@@ -34,9 +34,8 @@ class Image:
             self.set_definition(repo_local.get_image(name))
 
     def set_definition(self, definition):
-        for key in DEFINITION_MEMBERS:
-            if key in definition:
-                setattr(self, key, definition[key])
+        for key in DEFINITION_MEMBERS.intersection(definition):
+            setattr(self, key, definition[key])
 
     def get_definition(self):
         definition = {}
@@ -47,10 +46,9 @@ class Image:
         return definition
 
     def get_container(self, container_name):
-        container = Image(self.parent, True).get_container(container_name) if self.parent else Container(container_name)
+        container = Image(self.parent).get_container(container_name) if self.parent else Container(container_name, False)
         container.layers.append(self.name)
-        for key,value in self.env.items():
-            container.env[key] = value
+        container.env.update(self.env)
         for member in ('uid', 'gid', 'cmd', 'cwd', 'ready', 'halt'):
             value = getattr(self, member)
             if value:
diff --git a/usr/lib/python3.8/spoc/imagebuilder.py b/usr/lib/python3.8/spoc/imagebuilder.py
index f08ed2b..43e855e 100644
--- a/usr/lib/python3.8/spoc/imagebuilder.py
+++ b/usr/lib/python3.8/spoc/imagebuilder.py
@@ -72,11 +72,11 @@ class ImageBuilder:
             script.write(f'#!/bin/sh\nset -ev\n\n{script_lines}\n')
         os.chmod(script_path, 0o700)
         os.chown(script_path, 100000, 100000)
-        # Get the current image container definition and add the script file as a mount
+        # Create a temporary container from the current image definition
         container = self.image.get_container(self.image.name)
-        container.is_build = True
+        container.build = True
+        # Add the script file as a mount and execute it withing the container
         container.mounts[script_name] = (os.path.basename(script_path), False)
-        # Create a temporary container and run the script in it
         container.create()
         container.execute(['/bin/sh', '-lc', os.path.join('/', script_name)], True)
         container.destroy()