diff --git a/update.py b/update.py
index 96be066..5015e90 100755
--- a/update.py
+++ b/update.py
@@ -1,48 +1,151 @@
 #!/usr/bin/python3
 
+from __future__ import annotations
+
+from functools import lru_cache
 from pathlib import Path
-from subprocess import call
+from subprocess import call, check_output
 from datetime import datetime
-from typing import List
+
+import logging
+
 
 KEEP_DAYS = 3
 
+
 def main():
+    setup_logger()
     build_images()
     update_containers()
     prune()
 
 
-def build_images():
-    images = read_file(Path('images.conf'))
-    today = datetime.now().strftime('%Y%m%d')
+@lru_cache(maxsize=1)
+def get_today() -> str:
+    return datetime.now().strftime('%Y%m%d')
+
+
+class Image:
+    def __init__(self, base_name: str):
+        self._base_name = base_name
+
+    @property
+    def qual_name(self) -> str:
+        return f'{self._base_name}-panthera'
+
+    @property
+    def latest(self) -> str:
+        return f'{self.qual_name}:latest'
+
+    @property
+    def today(self) -> str:
+        return f'{self.qual_name}:{get_today()}'
+
+    @classmethod
+    def from_file(cls, path: Path) -> list[Image]:
+        return [cls(name) for name in read_file(path)]
+
+    @property
+    def _work_dir(self) -> Path:
+        return Path(f'../images/{self._base_name}')
+
+    def build(self):
+        if self._todays_image_exists:
+            logging.info(f'don\'t need to build {self._base_name}')
+        else:
+            logging.info(f'building {self._base_name}')
+            self._build_image()
+            self._tag_image()
+
+    @property
+    def _todays_image_exists(self) -> bool:
+        for image in images_on_host():
+            if self.qual_name in image and get_today() in image:
+                return True
+        else:
+            return False
+
+    def _build_image(self):
+        call(['docker', 'build', '--no-cache', f'--tag={self.today}', '.'],
+               cwd=self._work_dir)
+
+    def _tag_image(self):
+        call(['docker', 'tag', f'{self.today}', f'{self.latest}'])
+
+
+class Container:
+    def __init__(self, name: str):
+        self._name = name
+
+    @property
+    def name(self) -> str:
+        return self._name
+
+    @property
+    def _work_dir(self) -> Path:
+        return Path(f'../container/{self.name}')
+
+    def _pull_images(self) -> None:
+        logging.info('  pulling images')
+        call(['docker-compose', 'pull', '--ignore-pull-failures', '--quiet'],
+                cwd=self._work_dir)
+
+    def _up(self) -> None:
+        logging.info('  bringing up')
+        call(['docker-compose', 'up', '--detach'],
+               cwd=self._work_dir)
+
+    def update(self) -> None:
+        logging.info(f'container: {self.name}')
+        self._pull_images()
+        self._up()
+
+    @classmethod
+    def from_file(cls, path: Path) -> list[Container]:
+        return [cls(name) for name in read_file(path)]
+
+
+def build_images() -> None:
+    logging.info('building images')
+    images = Image.from_file(Path('images.conf'))
     for image in images:
-        path = Path(f'../images/{image}')
-        call(['docker', 'build', '--no-cache', f'--tag={image}-panthera:{today}', '.'],
-               cwd=path)
+        image.build()
 
 
-def update_containers():
-    containers = read_file(Path('container.conf'))
+def update_containers() -> None:
+    logging.info('updating containers')
+    containers = Container.from_file(Path('container.conf'))
     for container in containers:
-        path = Path(f'../container/{container}')
-        call(['docker-compose', 'pull'],
-               cwd=path)
-        call(['docker-compose', 'up', '-d'],
-               cwd=path)
+        container.update()
 
 
-def read_file(path: Path) -> List[str]:
+@lru_cache(maxsize=1)
+def images_on_host() -> list[str]:
+    result = check_output(['docker', 'images']).decode('utf-8').strip()
+    images = result.split('\n')
+    for image in images:
+        logging.debug(image)
+    return images
+
+
+def read_file(path: Path) -> list[str]:
     content = path.read_text().strip()
     elements = content.split('\n')
     elements = [item for item in elements if not item.startswith('#')]
     return elements
 
 
-def prune():
+def prune() -> None:
+    logging.info('pruning')
     hours = int(KEEP_DAYS * 24)
     call(['docker', 'system', 'prune', '--all', '--force', '--filter', f'until={hours}h'])
 
+
+def setup_logger() -> None:
+    logging.basicConfig(format='%(levelname)s: %(message)s', level=logging.INFO)
+    logging.info('set up logger')
+
+
 if __name__ == "__main__":
     main()