docker use common configuration in dockerfile and docker-compose.yml

Question

I'm using many docker containers. I want to assign a static ip to one of them and use that static ip in dockerfile of an other one.
I want to use some sort of config files like .env file and use it in both of dockerfile and docker-compose.yml .

Answer 1

I figure out a way. simply:

1. add the configurations to .env file like ip_server=172.20.0.2 .
2. use .env variables in docker-compose.yml and pass them to docker image as argument like:

    services:
      client
      build:
        context: ./client
        args:
          - IP_SERVER=${ip_server}

3. then use it in dockerfile like so

    ARG IP_SERVER
    ENV IP_SERVER=${IP_SERVER}

---

references:
- docker-compose env file
- docker-compose args
- dockerfile env

Answer 2

You probably don't want to do either of these things.

If you are running both containers in the same Docker Compose setup, then Compose will create a private Docker network for you, and one container can access the other using its container name (or the name of the block in the docker-compose.yml ) as a host name. That should eliminate the need for a static IP address.

Secondly, hard-coding host names or IP addresses like this makes it a lot harder to reuse your setup. As a very basic example, in development outside Docker, you might run the client and server on the same host and use localhost as the host name, but in a Docker Compose setup they'll be in different containers and use different host names. This would also mean you can never docker push your image to a registry, which is needed for some common deployment scenarios. An environment variable is a common way to pass this in from outside.

A docker-compose.yml that accomplished this might look like:

version: '3'
services:
  server:
    build:
      context: ./server
  client:
    build:
      context: ./client
    env:
      SERVER_URL: 'http://server/'