After editing the configuration file (and unintentionally adding some errors), I have restarted the service with:
sudo service mongodb restart
This results in the following message to the console:
mongodb stop/waiting
mongodb start/running, process XXXX
However, ps aux | grep mongo reports no mongo server running, and nothing it is written to the log.

If the server crashes due to a badly written configuration file, it should write to the log the cause and, even better, the lines in the configuration file that led to errors.

OS: Ubuntu 14.04, also on CentOS 7