Make base_image configurable

Fixes #487

repo2docker/app.py

@@ -415,6 +415,16 @@ def _user_name_default(self):
  """,
  )
 
+ base_image = Unicode(
+ "buildpack-deps:bionic",
+ config=True,
+ help="""
+ Base image to use when building docker images.
+
+ Should be an ubuntu derivative, minimum 18.04.
+ """,
+ )
+
  def get_engine(self):
  """Return an instance of the container engine.
 
@@ -757,7 +767,7 @@ def build(self):
 
  with chdir(checkout_path):
  for BP in self.buildpacks:
- bp = BP()
+ bp = BP(base_image=self.base_image)
  if bp.detect():
  picked_buildpack = bp
  break

repo2docker/buildpacks/base.py

@@ -12,7 +12,7 @@
 
 # Only use syntax features supported by Docker 17.09
 TEMPLATE = r"""
-FROM buildpack-deps:focal
+FROM {{base_image}}
 
 # Avoid prompts from apt
 ENV DEBIAN_FRONTEND=noninteractive
@@ -204,7 +204,6 @@ class BuildPack:
  Specifically used for creating Dockerfiles for use with repo2docker only.
 
  Things that are kept constant:
- - base image
  - some environment variables (such as locale)
  - user creation & ownership of home directory
  - working directory
@@ -214,9 +213,13 @@ class BuildPack:
 
  """
 
- def __init__(self):
+ def __init__(self, base_image):
+ """
+ base_image specifies the base image to use when building docker images
+ """
  self.log = logging.getLogger("repo2docker")
  self.appendix = ""
+ self.base_image = base_image
  self.labels = {}
  if sys.platform.startswith("win"):
  self.log.warning(
@@ -516,6 +519,7 @@ def render(self, build_args=None):
  appendix=self.appendix,
  # For docker 17.09 `COPY --chown`, 19.03 would allow using $NBUSER
  user=build_args.get("NB_UID", DEFAULT_NB_UID),
+ base_image=self.base_image,
  )
 
  @staticmethod

repo2docker/buildpacks/legacy/__init__.py

@@ -16,6 +16,9 @@ class LegacyBinderDockerBuildPack:
  This buildpack has been deprecated.
  """
 
+ def __init__(self, *args, **kwargs):
+ pass
+
  def detect(self):
  """Check if current repo should be built with the Legacy BuildPack."""
  log = logging.getLogger("repo2docker")