Docker Compose use environment variable on volumes

Question

Is there any way to use Docker Compose environment variable on volume section?

I used this configuration but it does not work:

SampleContainer:
        image: myImage:latest
        container_name: sample
        depends_on:
            - mysql-server
        restart: always
        environment:
            - 'SERVER_NAME=jingool'
        volumes:
            - /opt/docker/myapplication/bootstrap.properties:/opt/myserver/${SERVER_NAME}/bootstrap.properties

My problem is directory jingool not defined on volume.

How can I fix this problem?

Answer 1

You should use .env file where you'd put your global environments to be read by compose.

See: https://docs.docker.com/compose/environment-variables/#the-env-file for more information on how to use the file.

Another possible solution would be template.yml file called with docker-compose, e.g.:

• Create a template.yml, which is your docker-compose.yml with environment variable.
• Suppose your environment variables are in a file 'env.sh'
• Put the below piece of code in a sh file and run it.

source env.sh; rm -rf docker-compose.yml; envsubst < "template.yml" > "docker-compose.yml";

A new file docker-compose.yml will be generated with the correct values of environment variables.

Sample template.yml file:

SampleContainer:
        image: myImage:latest
        container_name: sample
        depends_on:
            - mysql-server
        restart: always
        volumes:
            - /opt/docker/myapplication/bootstrap.properties:/opt/myserver/${SERVER_NAME}/bootstrap.properties

Sample env.sh file:

#!/bin/bash 
export SERVER_NAME=jingool

Another options would include:

docker-compose 1.5+ has enabled variables substitution: https://github.com/docker/compose/releases

The latest Docker Compose allows you to access environment variables from your compose file. So you can source your environment variables, then run Compose like so:

set -a
source .my-env
docker-compose up -d

Then you can reference the variables in docker-compose.yml using ${VARIABLE}, like so:

/opt/docker/myapplication/bootstrap.properties:/opt/myserver/${SERVER_NAME}/bootstrap.properties

And here is more info from the docs, taken here: https://docs.docker.com/compose/compose-file/#variable-substitution

The BASH way:

Here is a more flexible method using a bash script and a .env file.

An example .env file:

EXAMPLE_URL=http://example.com
# Note that the variable below is commented out and will not be used:
# EXAMPLE_URL=http://example2.com 
SECRET_KEY=ABDFWEDFSADFWWEFSFSDFM

# You can even define the compose file in an env variable like so:
COMPOSE_CONFIG=my-compose-file.yml
# You can define other compose files, and just comment them out
# when not needed:
# COMPOSE_CONFIG=another-compose-file.yml

then run this bash script in the same directory, which should deploy everything properly:

#!/bin/bash
docker rm -f `docker ps -aq -f name=myproject_*`
set -a
source .env
cat ${COMPOSE_CONFIG} | envsubst | docker-compose -f - -p "myproject" up -d

There's also an interesting read here: https://modulitos.com/2016/03/lets-deploy-part-1/