docker commit after docker compose - docker

Question

I'm running docker compose as follows:
docker-compose -f docker-compose.dev.yml up --build -d
the contents of docker-compose.dev.yml are:
version: '3'
services:
client:
container_name: client
build:
context: frontend
environment:
- CADDY_SUBDOMAIN=xxx
- PRIVATE_IP=xxx
restart: always
ports:
- "80:80"
- "443:443"
links:
- express
volumes:
- /home/ec2-user/.caddy:/root/.caddy
express:
container_name: express
build: express
environment:
- NODE_ENV=development
restart: always
Then I want to create images from these containers to use them in a testing server by pushing them to aws ECR and pulling on the test server, to avoid the time of creating the dockers all over again. Simply using docker commit did not worked.
what is the correct approach to creating images from outputs of docker compose?
thanks

Answer 1

You should basically never use docker commit. The standard approach is to describe how to build your images using a Dockerfile, and check that file into source control. You can push the built image to a registry like Docker Hub, and you can check out the original source code and rebuild the image.
The good news is that you basically have this setup already. Each of your Compose services has a build: block that has the data on how to build the image. So it's enough to
docker-compose build
and you'll get a separate Docker image for each component.
Often if you're doing this you'll also want to push the images to some Docker registry. In the Compose setup, you can specify an image: for each service as well. If you have both build: and image:, that specifies the image name to use for the built image (otherwise Compose will pick one based on the project name).
version: '3.8'
services:
client:
build:
context: frontend
image: registry.example.com/project/frontend
et: cetera
express:
build: express
image: registry.example.com/project/express
et: cetera
Then you can have Compose both build and push the images
docker-compose build
docker-compose push
One final technique that can be useful is to split the Compose setup into two files. The main docker-compose.yml file has the setup you'd need to run the set of containers, on any system, with access to the container registry. A separate docker-compose.override.yml file would support developer use where you have a copy of the source code as well. If you're using Compose for deployment, you only need to copy the main docker-compose.yml file to the target system.
# docker-compose.yml
version: '3.8'
services:
client:
image: registry.example.com/project/frontend
ports: [...]
environment: [...]
restart: always
# volumes: [...]
express:
image: registry.example.com/project/express
ports: [...]
environment: [...]
restart: always
# docker-compose.override.yml
version: '3.8'
services:
client:
build: frontend
# all other settings come from main docker-compose.yml
express:
build: express
# all other settings come from main docker-compose.yml