Is it possible to source an environment file when launching a docker-compose file from Docker Stack

Question

I'd like to do create a sym link and source an environment file from my docker-compose file when I launch using Docker Stack. Like this:

version: '3'

services:
  hello_world:
    image: nginx:latest
    ports:
     - "80:80"
    volumes:
      - ./config:/config:ro   
      - ./data:/data          
    command:
      - /bin/bash
      - -c
      - |
        ln -s /config/lala /etc/nginx/lala
        source /config/env
        nginx -g 'daemon off;'

You can see that my command first creates a symbolic link, then sources an environment file found within the /config directory that is volume mounted, then launches nginx. I know that there are other ways to put environment variables in the docker-compose file, but I'm trying to decouple environment aspects from the docker-compose file itself.

I'm launching this using Docker Stack, like this:

docker stack deploy -c docker-compose-local.yml nginx-test

but when I shell into the container with:

docker exec -it 5c /bin/bash

I can see that while my symbolic link worked my environment variables are not loaded:

root@5c562e102cf4:/# env
HOSTNAME=5c562e102cf4
NJS_VERSION=1.15.9.0.2.8-1~stretch
NGINX_VERSION=1.15.9-1~stretch
PWD=/
HOME=/root
TERM=xterm
SHLVL=1
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
_=/usr/bin/env

root@5c562e102cf4:/# cat /etc/nginx/lala 
asdfadf

root@5c562e102cf4:/# source /config/env 
root@5c562e102cf4:/# env
TEST_NGINX_ENV_SETTING=test_setting1
HOSTNAME=5c562e102cf4
NJS_VERSION=1.15.9.0.2.8-1~stretch
TEST_POSTGRES_ENV_SETTING=test_setting2
NGINX_VERSION=1.15.9-1~stretch
PWD=/
HOME=/root
TERM=xterm
SHLVL=1
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
_=/usr/bin/env

Really appreciate anyone who can help me source this file from the mounted volume OR understand why what I'm trying to do may never work at all.

Does it work with normal docker-compose command ? I tested similar scenario with nodejs image with docker-compose command and it worked. — Mostafa Hussein, Mar 08 '19 at 00:36
It might, Mostafa, but it doesn't matter because I'm in a world where I have to use docker stack. — Bill Noto, Mar 08 '19 at 02:37
I could suggest adding your env file into a volume and then run your commands as an entrypoint. — Rodrigo Loza, Mar 08 '19 at 03:31

score 0 · Answer 1 · answered Mar 08 '19 at 03:40

Maybe you could try copying the content of your volume in a modified dockerfile and load the environment variables through an entrypoint.

The dockerfile would be:

FROM nginx:latest
COPY ./config /config

ENTRYPOINT ["bash", "start.sh"]

start.sh would be:

# !/bin/bash
source /config/env
nginx -g 'daemon off;'

And the stack.yml file would be:

version: '3'

services:
  nginx:
    image: nginx:latest
    ports:
     - "80:80"
    volumes:
      - ./data:/data

Note: you could also add your symbolic link in the entrypoint.

Is it possible to source an environment file when launching a docker-compose file from Docker Stack

1 Answers1