docker-compose.override.yml

docker-compose.override.yml

The docker-compose.override.yml is the configuration file where you can override existing settings from docker-compose.yml or even add completely new services.

By default, this file does not exist and you must create it. You can either copy the existing docker-compose.override.yml-example or create a new one.

How does docker-compose.override.yml work?

When you run docker-compose up, it searches for a file named docker-compose.yml and reads all configured services, networks, volumes etc to create your Docker stack. If you also additionally have a file named docker-compose.override.yml this will be read as well and used as an override file to complement. It works in the following order:

1. All definitions from docker-compose.yml will be used
2. All definitions that are also defined in docker-compose.override.yml will automatically overwrite the settings from docker-compose.yml
3. All definitions only available in docker-compose.override.yml will be added additionally.

For starting up your Docker Compose stack there are no additional steps or command line arguments required. If both files exist, they will be read automatically.

docker compose extends

Create docker-compose.override.yml

Copy example file

host> cd path/to/devilbox
host> cp docker-compose.override.yml-example docker-compose.override.yml

Create new file from scratch

1. Create an empty file within the Devilbox git directory named docker-compose.override.yml
2. Retrieve the currently used version from the existing docker-compose.yml file
3. Copy this version line to your newly created docker-compose.override.yml at the very top

# Create an empty file
host> cd path/to/devilbox
host> touch docker-compose.override.yml

# Retrieve the current version
host> grep ^version docker-compose.yml
version: '2.1'

# Add this version line to docker-compose.override.yml
host> echo "version: '2.1'" > docker-compose.override.yml

Let’s see again how this file should look like now:

version: '2.1'

[!NOTE] The documentation might be outdated and the version number might already be higher. Rely on the output of the grep command.

Further reading

To dive deeper into this topic and see how to actually add new services or overwrite existing services follow the below listed links:

* add-your-own-docker-image * overwrite-existing-docker-image