Data directory /data/db not found.
The error above is most likely what is causing the mongod instance to terminate upon starting.
What is the actual / full mongod command you’re using to start up the mongod instance? From the error, it looks like there is no /data/db directory found for the data directory. I understand you’ve specified the configuration file contents which contains a different dbPath value so I assume you’ve started the mongod instance without the configuration file - To learn more on using the configuration file please see the following Configuration File Options documentation.
Regards,
Jason