use intermediate dockerfile

Dockerfile.bionic

@@ -3,7 +3,7 @@ FROM ubuntu:bionic
 RUN sed -i -E 's/(archive|security).ubuntu.com/192.168.1.142/' /etc/apt/sources.list && \
     sed -i -E 's/^deb-src/# deb-src/' /etc/apt/sources.list && \
     apt-get update && \
-    apt-get install -y dpkg-dev debhelper build-essential sudo wget curl
+    DEBIAN_FRONTEND=noninteractive apt-get install -y dpkg-dev debhelper build-essential sudo wget curl
 
 RUN useradd builder && \
     install -d /build -o builder -g builder

Dockerfile.disco

@@ -3,7 +3,7 @@ FROM ubuntu:disco
 RUN sed -i -E 's/(archive|security).ubuntu.com/192.168.1.142/' /etc/apt/sources.list && \
     sed -i -E 's/^deb-src/# deb-src/' /etc/apt/sources.list && \
     apt-get update && \
-    apt-get install -y dpkg-dev debhelper build-essential sudo wget curl
+    DEBIAN_FRONTEND=noninteractive apt-get install -y dpkg-dev debhelper build-essential sudo wget curl
 
 RUN useradd builder && \
     install -d /build -o builder -g builder

Dockerfile.focal

@@ -0,0 +1,14 @@
+FROM ubuntu:focal
+
+RUN sed -i -E 's/(archive|security).ubuntu.com/192.168.1.142/' /etc/apt/sources.list && \
+    sed -i -E 's/^deb-src/# deb-src/' /etc/apt/sources.list && \
+    apt-get update && \
+    DEBIAN_FRONTEND=noninteractive apt-get install -y dpkg-dev debhelper build-essential sudo wget curl
+
+RUN useradd builder && \
+    install -d /build -o builder -g builder
+
+ADD scripts/bootstrap.sh /bootstrap.sh
+ADD scripts/build.sh /build.sh
+
+ENTRYPOINT ["/bootstrap.sh"]

Dockerfile.trusty

@@ -3,7 +3,7 @@ FROM ubuntu:trusty
 RUN sed -i -E 's/(archive|security).ubuntu.com/192.168.1.142/' /etc/apt/sources.list && \
     sed -i -E 's/^deb-src/# deb-src/' /etc/apt/sources.list && \
     apt-get update && \
-    apt-get install -y dpkg-dev debhelper build-essential sudo wget curl
+    DEBIAN_FRONTEND=noninteractive apt-get install -y dpkg-dev debhelper build-essential sudo wget curl
 
 RUN useradd builder && \
     install -d /build -o builder -g builder

Dockerfile.xenial

@@ -3,7 +3,7 @@ FROM ubuntu:xenial
 RUN sed -i -E 's/(archive|security).ubuntu.com/192.168.1.142/' /etc/apt/sources.list && \
     sed -i -E 's/^deb-src/# deb-src/' /etc/apt/sources.list && \
     apt-get update && \
-    apt-get install -y dpkg-dev debhelper build-essential sudo wget curl
+    DEBIAN_FRONTEND=noninteractive apt-get install -y dpkg-dev debhelper build-essential sudo wget curl
 
 RUN useradd builder && \
     install -d /build -o builder -g builder

build.sh

@@ -4,4 +4,13 @@ VARSFILE=$1
 
 . src/$VARSFILE
 
-time docker run -it --rm -e "VARSFILE=$VARSFILE" -v $PWD/src:/src extbuilder-$EXTPYTHON_DIST
+
+echo "FROM extbuilder-$EXTPYTHON_DIST" > Dockerfile.temp
+echo "RUN apt-get update && \\" >> Dockerfile.temp
+echo "    DEBIAN_FRONTEND=noninteractive apt-get install -y -o Dpkg::Options::=\"--force-confdef\" -o Dpkg::Options::=\"--force-confold\" $CPYTHON_DEPS" >> Dockerfile.temp
+
+# build image with just the deps
+docker build -t extbuilder-${EXTPYTHON_DIST}-deps -f Dockerfile.temp .
+rm -f Dockerfile.temp
+
+time docker run -it --rm -e "VARSFILE=$VARSFILE" -v $PWD/src:/src extbuilder-${EXTPYTHON_DIST}-deps

images.sh

@@ -1,7 +1,8 @@
 #!/bin/bash -ex
 
-RELEASES="trusty xenial bionic disco"
+RELEASES="trusty xenial bionic focal"
 
 for release in $RELEASES ; do
+    docker pull ubuntu:${release}
     docker build -t extbuilder-${release} -f Dockerfile.${release} .
 done

scripts/bootstrap.sh

@@ -5,10 +5,6 @@ ln -s /src/$VARSFILE /tmp/vars.sh
 . /tmp/vars.sh
 . /etc/lsb-release  #for DISTRIB_CODENAME
 
-# install deps
-apt-get update
-DEBIAN_FRONTEND=noninteractive apt-get install -y -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" $CPYTHON_DEPS
-
 # run the build
 sudo -Hu builder /build.sh