docker run --name oc --link mysql:db   owncloud_owncloud:latest env
 [...]
 DB_PORT=tcp://172.17.1.12:3306
 DB_PORT_3306_TCP=tcp://172.17.1.12:3306
 DB_PORT_3306_TCP_ADDR=172.17.1.12
 DB_PORT_3306_TCP_PORT=3306
 DB_PORT_3306_TCP_PROTO=tcp
 DB_NAME=/oc/db