Not able to use .env file with docker-compose

Question

I'm trying to use the .env file to set some variables on my docker-compose.yml like it's described here : and I'm not able to make it work. I tried exactly the same example from the doc and I keep getting the same error:

WARNING: The TAG variable is not set. Defaulting to a blank string.

This is the part of my docker-compose.yml where I use the variable:

version: '2.0'
services:
    mariadb-service:
        container_name: database-container
        image: mariadb:${TAG}

And this is my .env file:

TAG=10.1

I have docker-compose version 1.6.0.

Answer 1

only docker compose 1.7+ has supported .env file. You need to update docker-compose

you can check you version docker-compose -v