Adding a tag to all images in a docker-compose file?

For all my images I have a latest tag for production, and test for testing. I also have 2 docker-compose files that only differ in that one uses latest on all packages (except nginx), while the other uses test. Is there a way to set this via a CLI variable, so that I don’t have to keep those two files in sync manually all the time?

>Solution :

We can handle this with an environment variable.

docker-compose.yml:

services:
  ...
  my-service-one:
    image: my/service-one:$TAG
    ...
  my-service-two:
    image: my/service-two:$TAG
    ...

Then we can add an .env file (for production) with content

TAG=latest

and a test.env file (for testing) with content

TAG=test

When we run docker compose up, file .env will be used by default. If we want to start our test deployment, we can run docker compose --env-file test.env up.