使用 env_file 参数指定的 Docker 组合环境变量在 dockerfile 中不起作用

Question

This is a snippet of my docker-compose.yml file which I'm running with docker-compose build percona_dev .

percona_dev:
  build: docker/percona
  dockerfile: percona-dev
  env_file: docker.env

I've specified environment variables in docker.env like this:

USERNAME=xxx
PASSWORD=xxx
DESKTOP_IP=192.168.1.1
PLAYBOOK_LOCATION=/path/to/location/

This is the relevant portion of my Dockerfile called percona-dev :

FROM percona:5.6.24
MAINTAINER xxx

RUN apt-get update && apt-get install wget

RUN wget --ftp-user=$USERNAME --ftp-password=$PASSWORD ftp://$DESKTOP_IP/$PLAYBOOK_LOCATION/inventory/localhost -O /tmp/playbook/hosts

EXPOSE 3306
ENTRYPOINT [“/usr/bin/mysql”]

Unfortunately the environment variables don't get recognized and the build fails with:

Step 5 : RUN wget --ftp-user=$USERNAME --ftp-password=$PASSWORD ftp://$DESKTOP_IP/$PLAYBOOK_LOCATION/inventory/localhost -O /tmp/playbook/hosts
 ---> Running in 3595b5ce9581
ftp:////inventory/localhost: Invalid host name.
Service 'percona_dev' failed to build:

How do I make sure I can run the build without exposing sensitive environment variables in my Dockerfile or in thefilesystem layer history of my image?

Answer 1

environment variables are not available to the build step. See this proposal for making that more obvious in compose and this feature request to support the new build args added to docker 1.9.

The build args will do what you need.