How to use environment variables in docker compose

Question

I would like to be able to use env variables inside docker-compose.yml, with values passed in at the time of docker-compose up. This is the example. I am doing this today with basic docker run command, which is wrapped around my own script. Is there a way to achieve it with compose, without any such bash wrappers?

proxy:
  hostname: $hostname
  volumes:
    - /mnt/data/logs/$hostname:/logs
    - /mnt/data/$hostname:/data

Answer 1

1. Create a template.yml, which is your docker-compose.yml with environment variable.
2. Suppose your environment variables are in a file 'env.sh'
3. 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:

oracledb:
        image: ${ORACLE_DB_IMAGE}
        privileged: true
        cpuset: "0"
        ports:
                - "${ORACLE_DB_PORT}:${ORACLE_DB_PORT}"
        command: /bin/sh -c "chmod 777 /tmp/start; /tmp/start"
        container_name: ${ORACLE_DB_CONTAINER_NAME}

Sample env.sh file:

#!/bin/bash 
export ORACLE_DB_IMAGE=<image-name> 
export ORACLE_DB_PORT=<port to be exposed> 
export ORACLE_DB_CONTAINER_NAME=ORACLE_DB_SERVER

Answer 2

You cannot ... yet. But this is an alternative, think like a docker-composer.yml generator:

https://gist.github.com/Vad1mo/9ab63f28239515d4dafd

Basically a shell script that will replace your variables. Also you can use Grunt task to build your docker compose file at the end of your CI process.

Answer 3

add env to .env file

Such as

VERSION=1.0.0

then save it to deploy.sh

INPUTFILE=docker-compose.yml
RESULT_NAME=docker-compose.product.yml
NAME=test

prepare() {
        local inFile=$(pwd)/$INPUTFILE
        local outFile=$(pwd)/$RESULT_NAME
        cp $inFile $outFile
        while read -r line; do
            OLD_IFS="$IFS"
            IFS="="
            pair=($line)
            IFS="$OLD_IFS"
               sed -i -e "s/\${${pair[0]}}/${pair[1]}/g" $outFile
            done <.env
     }

deploy() {
        docker stack deploy -c $outFile $NAME
}


prepare
deploy

Answer 4

When using environment variables for volumes you need:

1. create .env file in the same folder which contains docker-compose.yaml file

2. declare variable in the .env file:

   HOSTNAME=your_hostname
   

3. Change $hostname to ${HOSTNAME} at docker-compose.yaml file

   proxy:
     hostname: ${HOSTNAME}
     volumes:
       - /mnt/data/logs/${HOSTNAME}:/logs
       - /mnt/data/${HOSTNAME}:/data
   

Of course you can do that dynamically on each build like:

echo "HOSTNAME=your_hostname" > .env && sudo docker-compose up

Answer 5

I have a simple bash script I created for this it just means running it on your file before use: https://github.com/antonosmond/subber

Basically just create your compose file using double curly braces to denote environment variables e.g:

app:
    build: "{{APP_PATH}}"
ports:
    - "{{APP_PORT_MAP}}"

Anything in double curly braces will be replaced with the environment variable of the same name so if I had the following environment variables set:

APP_PATH=~/my_app/build
APP_PORT_MAP=5000:5000

on running subber docker-compose.yml the resulting file would look like:

app:
    build: "~/my_app/build"
ports:
    - "5000:5000"

Answer 6

The best way is to specify environment variables outside the docker-compose.yml file. You can use env_file setting, and define your environment file within the same line. Then doing a docker-compose up again should recreate the containers with the new environment variables.

Here is how my docker-compose.yml looks like:

services:
  web:
    env_file: variables.env

Note: docker-compose expects each line in an env file to be in VAR=VAL format. Avoid using export inside the .env file. Also, the .env file should be placed in the folder where the docker-compose command is executed.