Slim down configurator image with alpine

By switching from ubuntu:18.04 to alpine, we reduce the local image size
from 510 to 87 Mb. Because we don't use bash anymore, it's difficult to
rely on chroot, so we just get rid of docker-entrypoint.sh

build/configurator/Dockerfile

@@ -1,14 +1,11 @@
-FROM ubuntu:18.04
+FROM python:3.6-alpine
 
-RUN apt update && \
-  apt install -y python3 python3-pip curl
-RUN pip3 install jinja2
+RUN apk add --no-cache curl
+RUN pip install jinja2
 
 RUN mkdir /openedx /openedx/config /openedx/templates
 COPY ./bin/configurator /usr/local/bin
-COPY ./bin/docker-entrypoint.sh /usr/local/bin
 WORKDIR /openedx/
 
-ENTRYPOINT ["docker-entrypoint.sh"]
 CMD configurator -c /openedx/config/config.json interactive && \
     configurator -c /openedx/config/config.json substitute /openedx/templates/ /openedx/output/

build/configurator/bin/configurator

@@ -103,6 +103,7 @@ def main():
     parser_substitute.set_defaults(func=substitute)
 
     args = parser.parse_args()
+
     args.func(args)
 
 def load_config(path):
@@ -183,6 +184,7 @@ def interactive_configuration(config_path):
     # Save values
     with open(config_path, 'w') as f:
         json.dump(configurator.as_dict(), f, sort_keys=True, indent=4)
+    set_owner(config_path)
 
 
 def substitute(args):
@@ -206,14 +208,35 @@ def substitute_file(config, src, dst):
         sys.exit(1)
 
     dst_dir = os.path.dirname(dst)
-    if not os.path.exists(dst_dir):
-        os.makedirs(dst_dir)
+    ensure_path_exists(dst_dir)
     with codecs.open(dst, encoding='utf-8', mode='w') as fo:
         fo.write(substituted)
+    set_owner(dst)
 
     # Set same permissions as original file
     os.chmod(dst, os.stat(src).st_mode)
 
+def ensure_path_exists(directory):
+    """
+    Create the required subfolders one by one, if necessary, and assign them
+    the right uid/gid.
+    """
+    to_create = []
+    while not os.path.exists(directory):
+        to_create.append(directory)
+        directory = os.path.dirname(directory)
+    for d in to_create[::-1]:
+        os.mkdir(d)
+        set_owner(d)
+
+def set_owner(path):
+    """
+    If the USER_ID environment variable is defined, use it to set the
+    owner/group of the given file path.
+    """
+    user_id = int(os.environ.get('USERID', 0))
+    if user_id:
+        os.chown(path, user_id, user_id)
 
 def random_string(length):
     return "".join([random.choice(string.ascii_letters + string.digits) for _ in range(length)])

build/configurator/bin/docker-entrypoint.sh

@@ -1,17 +0,0 @@
-#!/bin/bash -e
-USERID=${USERID:=0}
-
-## Configure user with a different USERID if requested.
-if [ "$USERID" -ne 0 ]
-    then
-        useradd --home-dir /openedx -u $USERID openedx
-
-        # Change file permissions
-        chown --no-dereference -R openedx /openedx/config
-
-        # Run CMD as different user
-        exec chroot --userspec="$USERID" --skip-chdir / env HOME=/openedx "$@"
-else 
-        # Run CMD as root (business as usual)
-        exec "$@"
-fi

deploy/templates/openedx/stats

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 # This is a small script that helps me collect stats about who is using this
 # project and understand how they are using it. Please don't remove me! As you
 # can see, no personal data is leaked.