/Docker 19

Link environment variables (superseded)

Note: Environment variables are no longer the recommended method for connecting to linked services. Instead, you should use the link name (by default, the name of the linked service) as the hostname to connect to. See the docker-compose.yml documentation for details.

Environment variables are only populated if you’re using the legacy version 1 Compose file format.

Compose uses Docker links to expose services’ containers to one another. Each linked container injects a set of environment variables, each of which begins with the uppercase name of the container.

To see what environment variables are available to a service, run docker-compose run SERVICE env.

Full URL, such as DB_PORT=tcp://

Full URL, such as DB_PORT_5432_TCP=tcp://

Container’s IP address, such as DB_PORT_5432_TCP_ADDR=

Exposed port number, such as DB_PORT_5432_TCP_PORT=5432

Protocol (tcp or udp), such as DB_PORT_5432_TCP_PROTO=tcp

Fully qualified container name, such as DB_1_NAME=/myapp_web_1/myapp_db_1

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