Docker-compose, conditional statements? (e.g. add volume only if condition)

Question

I want to add a volume to my service, but only if the final user gave a folder for it. Otherwise, no volume should be mounted, for the already-prepared image has valid data in a

Answer 1

Using conditional stmts in docker-compose is somewhat possible. Checkout variable substitution. The documentation is available for just the simplest of if-else. And since I have not tried with complex expressions involving strings, I cannot be sure. But following are the points you might want to keep in mind when trying out conditional variables:

• Environment variables in docker-compose file (with only a key) are resolved to their values on the machine Compose is running on. So when using ${CHEESE} in docker-compose, one should have CHEESE="cheddar" set in .env file or exported manually in host machine.
• Alternatively .env file can be set with env_file option. Variables in this file are exported in the docker container before the variables under environment option. That means variables in environment will override variables in env_file .