Environment variables within docker images

Question

My goal is to use environment variables in the docker-compose.yml file that can be referenced inside the application itself like in config/database.yml

docker-compose.yml

 ... environment: $DB_NAME: myapplication $DB_USER: appadmin $DB_PASS: secret ... 

config/database.yml

... database: $DB_NAME db_user: $DB_USER db:pass: $DB_PASS ... 

But no matter how do I try to send the variables to my file, They don't get recognised. :(

Answer 1

You're just trying to set the variables in the compose file? You shouldn't need the "$" in front of them in that case:

environment: - DB_NAME=database - DB_USER=appadmin - DB_PASS=secret 

You could use mappings too:

environment: DB_NAME: database DB_USER: appadmin DB_PASS: secret 

When you reference them in the database config file, you can just use the variable name too, again, without the "$":

environment: DB_NAME DB_USER DB_PASS 

You can check the Compose Environment Options documentation and the Compose Environment reference for further information.

Hope that helps.