Use docker import/export to make image smaller

Using docker export gives us only the top filesystem layer and not all
the layers used to build. Resulting image is about 20% smaller. Further
optimizations will be made in future commits via removing build time
deps and temporary files in the Dockerfile.

Change-Id: I0f7ad6d00c6f47836dcd71b05907076701bb2789
(cherry picked from commit 99dba22eaa3961234abde1294e55026fd2cc9d4d)

coreos/Makefile

@@ -4,7 +4,7 @@ docker:
 	./docker_build.bash
 
 coreos:
-	mkdir UPLOAD
+	mkdir -p UPLOAD
 	./coreos-oem-inject.py oem UPLOAD
 
 clean:
@@ -12,6 +12,7 @@ clean:
 	rm -f oem/container.tar.gz
 	rm -f UPLOAD/coreos_production_pxe_image-oem.cpio.gz
 	rm -f UPLOAD/coreos_production_pxe.vmlinuz
+	rm -rf ../.image_cache
 
 docker_clean:
 	./docker_clean.bash

coreos/coreos-oem-inject.py

@@ -8,7 +8,7 @@ import tempfile
 import shutil
 from plumbum import local, cmd
 
-COREOS_VERSION="dev-channel"
+COREOS_VERSION="197.0.0"
 
 COREOS_ARCH="amd64-generic"
 COREOS_BASE_URL="http://storage.core-os.net/coreos/{}/{}".format(COREOS_ARCH, COREOS_VERSION)

coreos/docker_build.bash

@@ -23,4 +23,7 @@ cd -
 # TODO: Investigate running a container and using "export" to flatten the
 #       image to shrink the CoreOS fs size. This will also require run.sh to
 #       use docker import instead of docker load as well.
-docker save oemdocker | gzip > ${OUTPUT_FILE}
+docker run oemdocker echo PICKME
+CONTAINER=`docker ps -a |grep PICKME|awk '{print $1}'|head -n1`
+echo $CONTAINER
+docker export $CONTAINER | gzip > ${OUTPUT_FILE}

coreos/oem/run.sh

@@ -24,8 +24,7 @@ while [ ! -e /var/run/docker.sock ]; do
   sleep 1;
 done
 
-# TODO: Use docker import (and export the image) to shrink image size
-docker load < container.tar.gz
+docker import - oemdocker:latest < container.tar.gz
 
 systemctl enable --runtime /usr/share/oem/system/*
 systemctl start ironic-python-agent.service