Use docker-compose env variable in Dockerbuild file

Question

Having the following docker-compose file:

db:     build: .     environment:         - MYSQL_ROOT_PASSWORD=password         - ENV=test     env_file: .env 

Is there any way to use the env variables declared in docker-compose.yml (either as environment or declared in the env_file) as part of Dockerfile without declaring them in the Dockerfile? Something like this:

FROM java:7 ADD ${ENV}/data.xml /data/ CMD ["run.sh"] 

Answer 1

Although this question was asked long ago, there is an answer to a similar question here: Pass environment variables from docker-compose to container at build stage

Basically, to use variables at the container's build time one has to define the variable in docker-compose.yml:

build:   context: .   args:     MYSQL_ROOT_PASSWORD: password     ENV: test 

and then reference it in the Dockerfile using ARG:

ARG MYSQL_ROOT_PASSWORD ARG ENV ADD ${ENV}/data.xml /data/ 

Concerning environment variables defined in an *.env file, I believe that they can't be passed to the container at build time.