optimize image size with multistage builds

Author: Sameer Naik

Dockerfile

@@ -1,4 +1,12 @@
+FROM ubuntu:bionic-20180526 AS add-apt-repositories
+
+RUN apt-get update \
+ && DEBIAN_FRONTEND=noninteractive apt-get install -y wget gnupg \
+ && wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add - \
+ && echo 'deb http://apt.postgresql.org/pub/repos/apt/ bionic-pgdg main' >> /etc/apt/sources.list
+
 FROM ubuntu:bionic-20180526
+
 LABEL maintainer="[email protected]"
 
 ENV PG_APP_HOME="/etc/docker-postgresql" \
@@ -12,11 +20,11 @@ ENV PG_APP_HOME="/etc/docker-postgresql" \
 ENV PG_BINDIR=/usr/lib/postgresql/${PG_VERSION}/bin \
     PG_DATADIR=${PG_HOME}/${PG_VERSION}/main
 
+COPY --from=add-apt-repositories /etc/apt/trusted.gpg /etc/apt/trusted.gpg
+
+COPY --from=add-apt-repositories /etc/apt/sources.list /etc/apt/sources.list
+
 RUN apt-get update \
- && DEBIAN_FRONTEND=noninteractive apt-get install -y wget gnupg \
- && wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add - \
- && echo 'deb http://apt.postgresql.org/pub/repos/apt/ bionic-pgdg main' > /etc/apt/sources.list.d/pgdg.list \
- && apt-get update \
  && DEBIAN_FRONTEND=noninteractive apt-get install -y acl sudo \
       postgresql-${PG_VERSION} postgresql-client-${PG_VERSION} postgresql-contrib-${PG_VERSION} \
  && ln -sf ${PG_DATADIR}/postgresql.conf /etc/postgresql/${PG_VERSION}/main/postgresql.conf \
@@ -26,9 +34,13 @@ RUN apt-get update \
  && rm -rf /var/lib/apt/lists/*
 
 COPY runtime/ ${PG_APP_HOME}/
+
 COPY entrypoint.sh /sbin/entrypoint.sh
+
 RUN chmod 755 /sbin/entrypoint.sh
 
 EXPOSE 5432/tcp
+
 WORKDIR ${PG_HOME}
+
 ENTRYPOINT ["/sbin/entrypoint.sh"]