Installing MongoDB is pretty easy, as long as you have homebrew, which can be done with one line command
$ brew install mongodb
However if you try to start a MongoDB daemon on your Mac OSX, most likely you will run into this error and fail to launch it.
error: dbpath (/data/db) does not exist
That means we mac users need something extra- to create such a path for MongoDB.
$ sudo mkdir -p /data/db $ sudo chown `id -u` /data/db