Load Docker image from registry to daemon.

load_image_from_registry.py

#!/usr/bin/env python3
import os
import json
from io import BytesIO
import tarfile
from tarfile import TarInfo
import docker
import sys

reg_dir = os.environ.get('DOCKER_REGISTRY_DIR', '/tmp/registry')
c = docker.Client(os.environ.get('DOCKER_HOST', 'unix://var/run/docker.sock'))

tar_io = BytesIO()
tar = tarfile.open(mode='w|', fileobj=tar_io)
os.chdir(reg_dir)
os.chdir('./repositories/library/{0}'.format(sys.argv[1]))

latest = open('./tag_latest').read()
repositories = TarInfo('repositories')
repositories_io = BytesIO()
repositories.size = repositories_io.write(json.dumps({"app-base": {"latest": latest}}).encode())
repositories_io.seek(0)
tar.addfile(repositories, repositories_io)

os.chdir(reg_dir)
os.chdir('./images')
ids =  [i['Id'] for i in c.images(all=True)]

os.chdir(latest)
ancestry = json.load(open('ancestry'))
os.chdir('../')
for image_id in ancestry:
    if image_id not in ids:
        tar.add(image_id)
        tar.add('{0}/json'.format(image_id))
        tar.add('{0}/layer'.format(image_id), '{0}/layer.tar'.format(image_id))
tar.close()
tar_io.seek(0)
c.load_image(tar_io)