I'm trying to start mongodb(3.0.2) with authentication enabled on mac osx 10.10 from the [doc](http://docs.mongodb.org/manual/tutorial/enable-authentication/). Starting monodb manually with `--auth` works and starts without any error. I installed mongodb using homebrew and want to place the auth switch in configuration file. I could not find anything appropriate in [Configuration Options](http://docs.mongodb.org/manual/reference/configuration-options/). I tried `auth: true` in the config file but mongodb failed to start. 

Anybody has got it working, I'm looking for config file option(rather than --auth) to run mongodb with authentication enabled to prevent anonymous access.