How to rebuild dockerfile quick by using cache?

Question

I want to optimize my Dockerfile. And I wish to keep cache file in disk. But, I found when I run docker build . It always try to get every file from network.

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Answer 1

An update to previous answers, current docker build accepts --build-arg that pass environment variables like http_proxy without saving it in the resulting image.

Example:

# get squid
docker run --name squid -d --restart=always \
  --publish 3128:3128 \
  --volume /var/spool/squid3 \
  sameersbn/squid:3.3.8-11

# optionally in another terminal run tail on logs
docker exec -it squid tail -f /var/log/squid3/access.log

# get squid ip to use in docker build
SQUID_IP=$(docker inspect --format '{{ .NetworkSettings.IPAddress }}' squid)

# build your instance
docker build --build-arg http_proxy=http://$SQUID_IP:3128 .