MongoDB Configuration File Locations
The MongoDB server actually does not search any locations for config files, and there is (as at MongoDB 3.2) no way to specify multiple config files or include config file fragments. There was a feature suggestion for includes discussed (see: SERVER-14911 in the MongoDB issue tracker), but it was decided that includes are not part of standard YAML and configuration management systems are likely the best option.


  From searching I know it checks /usr/local/etc/mongod.conf by default.


This is the default provided in the service recipe for the mongodb Homebrew package. The official Linux packages generally use a convention of /etc/mongod.conf.