build 接受--build-arg传递环境变量的方式，例如http_proxy 不将其保存在生成​​的映像中。

例：

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 .