Template for travis.yml with docker cache between the builds

travis-cache-docker.yml

sudo: required
dist: trusty

services:
  - docker

cache:
  - directories:
    - /var/tmp/docker

before_install:
  - echo 'DOCKER_OPTS="-g /var/tmp/docker/"' | sudo tee -a /etc/default/docker
  - sudo service docker restart

install:
# docker build commands
  - sudo chmod -R 775 /var/tmp/docker

script:
# docker run tests

after_success:
# docker push