docker-compose not setting environment variables - docker

Question

When I run docker-compose build && docker-compose up redis, with environment specified in docker-compose.yaml and RUN env in the Dockerfile, the environment variables I set don't get printed.
Why does this not work?
I'm using docker-compose version 1.4.2.
Here are the relevant files:
docker-compose.yaml with environment as a list of KEY=value pairs:
redis:
build: ../storage/redis
ports:
- "6379:6379"
environment:
- FOO='bar'
docker-compose.yaml with environment as a dictionary:
redis:
build: ../storage/redis
ports:
- "6379:6379"
environment:
- FOO: 'bar'
Dockerfile:
FROM redis:2.6
MAINTAINER me#email.com
RUN mkdir -p /var/redis && chown -R redis:redis /var/redis
RUN echo '-------------- env ---------------'
RUN env
COPY redis.conf /usr/local/etc/redis/redis.conf
EXPOSE 6379
ENTRYPOINT ["redis-server", "/usr/local/etc/redis/redis.conf"]

Answer 1

That's normal
docker-compose only sets the environment variables specified in the environment directive in the docker-compose.yaml file during the run phase of the container, and not during the build phase.
So if you do docker-compose run --entrypoint "/bin/bash" redis -c env you will be able to see your env variables.
If you want to set variables inside your Dockerfile (to be able to see them during the build phase) you can add inside your dockerfile before your RUN env:
ENV FOO bar

Answer 2

Well
I have tested and found following solutions for docker compose with env file or without env file. I will show you two different approach
Lets say you have following docker compose yml file
version: '3.8'
services:
db:
image: postgres:13
volumes:
- "./volumes/postgres:/var/lib/postgresql/data"
ports:
- "5432:5432"
env_file: docker.env
Now you need to setup the postgres variable in a file called docker.env. Remember you need to keep the docker_compose.yml file and docker.env file in same folder.
Next, In the docker.env file you need to have the database variable and value like this:
POSTGRES_USER=postgres
POSTGRES_PASSWORD=postgres
POSTGRES_DB=myapp_db
Now hit docker-compose up . It should work.
Lets say now you dont like to specify the env file name in the docker-compose.yml file. So you have to write docker-compose.yml file like this:
version: '3.8'
services:
db:
image: postgres:13
volumes:
- "./volumes/postgres:/var/lib/postgresql/data"
ports:
- "5432:5432"
environments:
- POSTGRES_USER=${PGU}
-POSTGRES_PASSWORD=${PGP}
-POSTGRES_DB=${PGD}
Now your docker.env file should look like this:
PGU=postgres
PGP=postgres
PGD=myapp_db
now hit docker-compose --env-file docker.env up
you are good to go.

Answer 3

This is because you were using environment when (I guess) you wanted to use args inside the build block:
redis:
build:
context: ../storage/redis
args:
- FOO: 'bar'
ports:
- "6379:6379"
Your Dockerfile would define FUN in the (image) environment:
FROM redis:2.6
RUN mkdir -p /var/redis && chown -R redis:redis /var/redis
# Read FUN from (build) arguments
# (may define a default: ARG FUN='wow')
ARG FUN
# Define env variable FUN with value from ARG
ENV FUN=$FUN
RUN echo '-------------- env ---------------'
RUN env
COPY redis.conf /usr/local/etc/redis/redis.conf
EXPOSE 6379
ENTRYPOINT ["redis-server", "/usr/local/etc/redis/redis.conf"]
The environment block is used to define variables for the running container (when docker-compose up, NOT when docker-compose build).