What are Docker Compose variables and how do I use them?

What are Docker Compose variables and how do I use them?

Docker Compose variables allow you to customize your Docker Compose files. You can define variables in a .env file or directly in the Compose file using the ${VARIABLE_NAME} syntax.

Can you give me an example of how to define a variable in a .env file?

Sure! In your .env file, you can define a variable like this: MYSQL_ROOT_PASSWORD=my-secret-pw. Then, in your docker-compose.yml, you can reference it as ${MYSQL_ROOT_PASSWORD}.

What happens if I don't define a variable in the .env file?

If you don't define a variable in the .env file, Docker Compose will use the default value if specified, or it will throw an error if the variable is required.

Can I override these variables when running Docker Compose?

Yes, you can override variables by passing them directly in the command line like this: MYSQL_ROOT_PASSWORD=new-password docker-compose up.